DNV-OS-F101 - Submarine Pipeline Systemsspkenny/Courses/Undergraduate/ENGI8673/Readin… ·...

OFFSHORE STANDARD

DET NORSKE VERITAS

DNV-OS-F101

SUBMARINE PIPELINE SYSTEMS

OCTOBER 2007

FOREWORDDET NORSKE VERITAS (DNV) is an autonomous and independent foundation with the objectives of safeguarding life, prop-erty and the environment, at sea and onshore. DNV undertakes classification, certification, and other verification and consultancyservices relating to quality of ships, offshore units and installations, and onshore industries worldwide, and carries out researchin relation to these functions.DNV Offshore Codes consist of a three level hierarchy of documents:— Offshore Service Specifications. Provide principles and procedures of DNV classification, certification, verification and con-

sultancy services.— Offshore Standards. Provide technical provisions and acceptance criteria for general use by the offshore industry as well as

the technical basis for DNV offshore services.— Recommended Practices. Provide proven technology and sound engineering practice as well as guidance for the higher level

Offshore Service Specifications and Offshore Standards.DNV Offshore Codes are offered within the following areas:A) Qualification, Quality and Safety MethodologyB) Materials TechnologyC) StructuresD) SystemsE) Special FacilitiesF) Pipelines and RisersG) Asset OperationH) Marine OperationsJ) Wind Turbines

Amendments and Corrections This document is valid until superseded by a new revision. Minor amendments and corrections will be published in a separatedocument normally updated twice per year (April and October). For a complete listing of the changes, see the “Amendments and Corrections” document located at: http://webshop.dnv.com/global/, under category “Offshore Codes”.
The electronic web-versions of the DNV Offshore Codes will be regularly updated to include these amendments and corrections.
Comments may be sent by e-mail to [email protected] subscription orders or information about subscription terms, please use [email protected] information about DNV services, research and publications can be found at http://www.dnv.com, or can be obtained from DNV, Veritasveien 1, NO-1322 Høvik, Norway; Tel +47 67 57 99 00, Fax +47 67 57 99 11.

© Det Norske Veritas. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, including photocopying and recording, without the prior written consent of Det Norske Veritas.

Computer Typesetting (FM+SGML) by Det Norske Veritas.Printed in Norway.

If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of Det Norske Veritas, then Det Norske Veritas shall pay compensation to such personfor his proved direct loss or damage. However, the compensation shall not exceed an amount equal to ten times the fee charged for the service in question, provided that the maximum compen-sation shall never exceed USD 2 million.In this provision "Det Norske Veritas" shall mean the Foundation Det Norske Veritas as well as all its subsidiaries, directors, officers, employees, agents and any other acting on behalf of DetNorske Veritas.

GeneralThis document supersedes the January 2000 edition, as amended in October 2005.

Main changesIn addition to updating the material related parts, DNV has used this opportunity to update the operation phase requirements,making it more transparent from design until abandonment. This included a re-assessment of the documentation requirementsthat now constitutes Sec.12 moved from Sec.3. This work has also been funded by a JIP from the industry. Minor changes havebeen made to the layout of the design sections. The intention is to make the design more consistent and transparent, in particularwith respect to load combinations. The resulting design is not intended to be changed. Some requirements have been added withrespect to Hydrogen Induced Stress Cracking (HISC).

AcknowledgementThe current revision of DNV-OS-F101 has been sponsored by three different Joint Industry Projects. The work has been performedby DNV and discussed in several workshops with individuals from the different companies. They are hereby all acknowledged fortheir valuable and constructive input. In case consensus has not been achievable DNV has sought to provide acceptable compromiseagreement.The two material related JIP's have in total been sponsored by:

The operation JIP has been sponsored by:

In addition, individuals from the following companies have been reviewers in the hearing process:

DNV is grateful for the valuable co-operations and discussions with the individual personnel in these companies.

BP MRM TechnipChevron NSC TenarisCorus PTT V&MEuropipe Saipem VectorFMC Sintef VetcoHydro Statoil WoodsideJFE Subsea7

ConocoPhillips Gassco ShellDONG Hydro StatoilENI

Acergy Hydro StatoilAllseas Inoxtech Sumitomo Corp., EuropeButting Intec Tenaris DalmineEuropipe JFE V & M DeutschlandGorgon Nippon Steel

DET NORSKE VERITAS

DET NORSKE VERITAS

Offshore Standard DNV-OS-F101, October 2007 Contents –

CONTENTS

Sec. 1 General................................................................. 13

A. General..................................................................................13A 100 Introduction..................................................................... 13A 200 Objectives ....................................................................... 13A 300 Scope and application ..................................................... 13A 400 Alternative methods and procedures............................... 14A 500 Structure of Standard ...................................................... 14A 600 Other codes ..................................................................... 14

B. References ............................................................................15B 100 Offshore Service Specifications...................................... 15B 200 Offshore Standards ......................................................... 15B 300 Recommended Practices ................................................. 15B 400 Rules ............................................................................... 15B 500 Certification notes and classification notes .................... 15B 600 Other references.............................................................. 15

C. Definitions ............................................................................18C 100 Verbal forms ................................................................... 18C 200 Definitions ...................................................................... 18C 300 Definitions (continuation)............................................... 21

D. Abbreviations and Symbols..................................................22D 100 Abbreviations.................................................................. 22D 200 Symbols .......................................................................... 23D 300 Greek characters ............................................................. 24D 400 Subscripts........................................................................ 25

Sec. 2 Safety Philosophy................................................ 26

A. General..................................................................................26A 100 Objective......................................................................... 26A 200 Application...................................................................... 26

B. Safety Philosophy Structure ................................................26B 100 General............................................................................ 26B 200 Safety objective............................................................... 26B 300 Systematic review of risks .............................................. 27B 400 Design criteria principles ................................................ 27B 500 Quality assurance............................................................ 27B 600 Health, safety and environment ...................................... 27

C. Risk Basis for Design ...........................................................27C 100 General............................................................................ 27C 200 Categorisation of fluids................................................... 27C 300 Location classes .............................................................. 28C 400 Safety classes .................................................................. 28C 500 Reliability analysis.......................................................... 28

Sec. 3 Concept Development and Design Premises .... 29

A. General..................................................................................29A 100 Objective......................................................................... 29A 200 Application...................................................................... 29A 300 Concept development ..................................................... 29

B. System Design Principles .....................................................29B 100 System integrity .............................................................. 29B 200 Monitoring/inspection during operation ......................... 29B 300 Pressure Protection System............................................. 30B 400 Hydraulic analyses and flow assurance .......................... 30

C. Pipeline Route.......................................................................31C 100 Location .......................................................................... 31C 200 Route survey ................................................................... 31C 300 Seabed properties............................................................ 32

D. Environmental Conditions.................................................... 32D 100 General............................................................................ 32D 200 Collection of environmental data.................................... 32D 300 Environmental data ......................................................... 32

E. External and Internal Pipe Condition ...................................33E 100 External operational conditions ...................................... 33E 200 Internal installation conditions........................................ 33E 300 Internal operational conditions ....................................... 33

Sec. 4 Design - Loads..................................................... 34

A. General..................................................................................34A 100 Objective......................................................................... 34A 200 Application ..................................................................... 34A 300 Load scenarios ................................................................ 34A 400 Load categories ............................................................... 34A 500 Design cases.................................................................... 34A 600 Load effect combination ................................................. 34

B. Functional Loads ..................................................................34B 100 General............................................................................ 34B 200 Internal Pressure loads.................................................... 34B 300 External Pressure loads................................................... 35

C. Environmental Loads............................................................35C 100 General............................................................................ 35C 200 Wind loads ...................................................................... 35C 300 Hydrodynamic loads....................................................... 35C 400 Ice loads .......................................................................... 36C 500 Earthquake ...................................................................... 36C 600 Characteristic environmental load effects ...................... 36

D. Construction Loads...............................................................38D 100 General............................................................................ 38

E. Interference Loads ................................................................38E 100 General............................................................................ 38

F. Accidental Loads ..................................................................38F 100 General............................................................................ 38

G. Design Load Effects .............................................................39G 100 Design cases.................................................................... 39G 200 Load combinations.......................................................... 39G 300 Load effect calculations.................................................. 40

Sec. 5 Design – Limit State Criteria ........................... 41

A. General..................................................................................41A 100 Objective......................................................................... 41A 200 Application ..................................................................... 41

B. System Design Principles .....................................................41B 100 Submarine pipeline system layout .................................. 41B 200 Mill pressure test and system pressure test..................... 42B 300 Operating requirements .................................................. 43

C. Design Format ......................................................................43C 100 General............................................................................ 43C 200 Design resistance ............................................................ 43C 300 Characteristic material properties ................................... 44C 400 Stress and strain calculations .......................................... 45

D. Limit States...........................................................................46D 100 General............................................................................ 46D 200 Pressure containment (bursting) ..................................... 46D 300 Local buckling - General ................................................ 46D 400 Local Buckling – External over pressure only

(System collapse)............................................................ 46D 500 Propagation buckling ..................................................... 47D 600 Local Buckling - Combined Loading Criteria ................ 47D 700 Global buckling ............................................................. 49D 800 Fatigue ............................................................................ 49D 900 Ovalisation...................................................................... 50D 1000 Accumulated deformation .............................................. 50D 1100 Fracture and supplementary requirement P .................... 50D 1200 Ultimate limit state – Accidental loads........................... 51

E. Special Considerations .........................................................51E 100 General............................................................................ 51E 200 Pipe soil interaction ........................................................ 51E 300 Spanning risers/pipelines ................................................ 52E 400 On bottom stability ......................................................... 52E 500 Trawling interference...................................................... 52E 600 Third party loads, dropped objects ................................. 53E 700 Thermal Insulation.......................................................... 53

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Offshore Standard DNV-OS-F101, October 2007 – Contents

E 800 Settings from Plugs .........................................................53

F. Pipeline Components and Accessories ................................. 53F 100 General ............................................................................53F 200 Design of bends...............................................................54F 300 Design of insulating joints ..............................................54F 400 Design of pig traps ..........................................................54F 500 Design of valves..............................................................54F 600 Pipeline fittings ...............................................................55

G. Supporting Structure............................................................. 55G 100 General ............................................................................55G 200 Pipe-in-pipe and bundles.................................................55G 300 Riser supports..................................................................55G 400 J-tubes .............................................................................55G 500 Stability of gravel supports and gravel covers ................55

H. Installation and Repair.......................................................... 56H 100 General ............................................................................56H 200 Pipe straightness..............................................................56H 300 Coating ............................................................................56

Sec. 6 Design - Materials Engineering......................... 57

A. General.................................................................................. 57A 100 Objective .........................................................................57A 200 Application......................................................................57A 300 Documentation ................................................................57

B. Materials Selection for Linepipe and Pipeline Components ..................................................... 57

B 100 General ............................................................................57B 200 Sour service.....................................................................57B 300 Corrosion resistant alloys (informative) .........................58B 400 Linepipe (informative) ....................................................58B 500 Pipeline components (informative) .................................59B 600 Bolts and nuts..................................................................59B 700 Welding consumables (informative) ...............................59

C. Materials Specification ......................................................... 59C 100 General ............................................................................59C 200 Linepipe specification .....................................................60C 300 Components specification ..............................................60C 400 Specification of bolts and nuts ........................................60C 500 Coating specification.......................................................60C 600 Galvanic anodes specification.........................................61

D. Corrosion Control ................................................................. 61D 100 General ............................................................................61D 200 Corrosion allowance .......................................................61D 300 Temporary corrosion protection......................................61D 400 External pipeline coatings (informative).........................62D 500 Cathodic Protection.........................................................62D 600 External corrosion control of risers

(informative) ...................................................................63D 700 Internal corrosion control (informative) .........................64

Sec. 7 Construction – Linepipe .................................... 66

A. General.................................................................................. 66A 100 Objective .........................................................................66A 200 Application......................................................................66A 300 Process of manufacture ...................................................66A 400 Supplementary requirements...........................................66A 500 Linepipe specification ....................................................66A 600 Manufacturing Procedure Specification

and qualification..............................................................66

B. Carbon Manganese (C-Mn) Steel Linepipe.......................... 67B 100 General ............................................................................67B 200 Pipe designation .............................................................67B 300 Manufacturing .................................................................67B 400 Acceptance criteria..........................................................69B 500 Inspection ........................................................................72

C. Corrosion Resistant Alloy (CRA) Linepipe ......................... 75C 100 General ............................................................................75C 200 Pipe designation ..............................................................75C 300 Manufacture ....................................................................75C 400 Acceptance criteria..........................................................75C 500 Inspection ........................................................................76

D. Clad or Lined Steel Linepipe................................................77D 100 General ............................................................................77D 200 Pipe designation ..............................................................77D 300 Manufacturing Procedure Specification .........................77D 400 Manufacture ....................................................................78D 500 Acceptance criteria..........................................................78D 600 Inspection ........................................................................79

E. Hydrostatic Testing...............................................................80E 100 Mill pressure test .............................................................80

F. Non-destructive Testing........................................................80F 100 Visual inspection.............................................................80F 200 Non-destructive testing ...................................................80

G. Dimensions, Mass and Tolerances .......................................81G 100 General ............................................................................81G 200 Tolerances .......................................................................81G 300 Inspection ........................................................................82

H. Marking, Delivery Condition and Documentation ...............84H 100 Marking...........................................................................84H 200 Delivery condition...........................................................84H 300 Handling and storage .....................................................84H 400 Documentation, records and certification .......................84

I. Supplementary Requirements...............................................84I 100 Supplementary requirement, sour service (S) .................84I 200 Supplementary requirement,

fracture arrest properties (F) ...........................................85I 300 Supplementary requirement, linepipe for plastic

deformation (P) ...............................................................86I 400 Supplementary requirement, dimensions (D) .................87I 500 Supplementary requirement, high utilisation (U) ...........88

Sec. 8 Construction - Components and Assemblies ... 89

A. General..................................................................................89A 100 Objective .........................................................................89A 200 Application......................................................................89A 300 Quality assurance ............................................................89

B. Component Requirements ....................................................89B 100 General ............................................................................89B 200 Component specification.................................................89B 300 Induction bends – additional

and modified requirements to ISO 15590-1....................89B 400 Fittings, tees and wyes -

additional requirements to ISO 15590-2.........................90B 500 Flanges and flanged connections -

additional requirements to ISO 15590-3.........................92B 600 Valves – Additional requirements to ISO 14723 ............92B 700 Mechanical connectors....................................................93B 800 CP Insulating joints.........................................................93B 900 Anchor flanges ................................................................94B 1000 Buckle- and fracture arrestors .........................................94B 1100 Pig traps...........................................................................94B 1200 Repair clamps and repair couplings ................................94

C. Materials for Components ....................................................94C 100 General ............................................................................94C 200 C-Mn and low alloy steel forgings and castings .............94C 300 Duplex stainless steel, forgings and castings ..................95C 400 Pipe and plate material ....................................................95C 500 Sour Service ....................................................................95

D. Manufacture..........................................................................95D 100 Manufacturing procedure specification (MPS) ..............95D 200 Forging ............................................................................95D 300 Casting ............................................................................96D 400 Hot forming.....................................................................96D 500 Heat treatment .................................................................96D 600 Welding...........................................................................96D 700 NDT ................................................................................96

E. Mechanical and Corrosion Testing of Hot Formed, Cast and Forged Components...............................................96

E 100 General testing requirements ..........................................96E 200 Acceptance criteria for C-Mn and low alloy steels ........97E 300 Acceptance criteria for duplex stainless steels................98

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F. Fabrication of Risers, Expansion Loops, Pipe Strings for Reeling and Towing........................................................98

F 100 General............................................................................ 98F 200 Materials for risers, expansion loops, pipe strings

for reeling and towing..................................................... 98F 300 Fabrication procedures and planning.............................. 98F 400 Material receipt, identification and tracking................... 98F 500 Cutting, forming, assembly, welding and heat treatment98F 600 Hydrostatic testing .......................................................... 98F 700 NDT and visual examination .......................................... 99F 800 Dimensional verification................................................. 99F 900 Corrosion protection ....................................................... 99

G. Hydrostatic Testing...............................................................99G 100 Hydrostatic testing .......................................................... 99G 200 Alternative test pressures ................................................ 99

H. Documentation, Records, Certification and Marking ........ 100H 100 General.......................................................................... 100

Sec. 9 Construction - Corrosion Protection and Weight Coating .......................................... 101

A. General................................................................................101A 100 Objective....................................................................... 101A 200 Application.................................................................... 101

B. External Corrosion Protective Coatings .............................101B 100 General.......................................................................... 101B 200 Coating materials, surface preparation,

coating application and inspection/testing of coating... 101

C. Concrete Weight Coating ...................................................101C 100 General.......................................................................... 101C 200 Concrete materials and coating manufacture................ 102C 300 Inspection and testing ................................................... 102

D. Manufacture of Galvanic Anodes....................................... 102D 100 Anode manufacture....................................................... 102

E. Installation of Galvanic Anodes .........................................103E 100 Anode installation ......................................................... 103

Sec. 10 Construction - Installation ............................... 104

A. General................................................................................104A 100 Objective....................................................................... 104A 200 Application.................................................................... 104A 300 Failure Mode Effect Analysis (FMEA)

and Hazard and Operability (HAZOP) studies ............. 104A 400 Installation and testing specifications and drawings..... 104A 500 Installation manuals ...................................................... 104A 600 Quality assurance.......................................................... 104A 700 Welding......................................................................... 104A 800 Non-destructive testing and visual examination........... 105A 900 Production tests............................................................. 105

B. Pipeline Route, Survey and Preparation .............................105B 100 Pre-installation route survey ......................................... 105B 200 Seabed preparation........................................................ 106B 300 Pipeline and cable crossings ......................................... 106B 400 Preparations for shore approach ................................... 106

C. Marine Operations ..............................................................106C 100 General.......................................................................... 106C 200 Vessels .......................................................................... 106C 300 Anchoring systems, anchor patterns and anchor

positioning .................................................................... 106C 400 Positioning systems ...................................................... 107C 500 Dynamic positioning..................................................... 107C 600 Cranes and lifting equipment........................................ 107C 700 Anchor handling and tug management ......................... 107C 800 Contingency procedures ............................................... 107

D. Pipeline Installation ............................................................107D 100 General.......................................................................... 107D 200 Installation manual........................................................ 108D 300 Review and qualification of the installation manual,

essential variables and validity ..................................... 108D 400 Operating limit conditions ............................................ 109D 500 Installation procedures.................................................. 109

D 600 Contingency procedures ............................................... 109D 700 Layvessel arrangement, laying equipment and

instrumentation ............................................................. 109D 800 Requirements for installation........................................ 110

E. Additional Requirements for Pipeline Installation Methods Introducing Plastic Deformations ........................111

E 100 General.......................................................................... 111E 200 Installation manual........................................................ 111E 300 Qualification of the installation manual ....................... 111E 400 Installation procedures.................................................. 111E 500 Requirements for installation........................................ 111

F. Pipeline Installation by Towing..........................................112F 100 General.......................................................................... 112F 200 Installation manual........................................................ 112F 300 Qualification of installation manual ............................. 112F 400 Operating limit conditions ............................................ 112F 500 Installation procedures.................................................. 112F 600 Contingency procedures ............................................... 112F 700 Arrangement, equipment and instrumentation ............. 112F 800 Pipestring tow and installation...................................... 112

G. Other Installation Methods .................................................112G 100 General.......................................................................... 112

H. Shore Pull............................................................................113H 100 General.......................................................................... 113H 200 Installation manual........................................................ 113H 300 Qualification of installation manual ............................. 113H 400 Operating limit conditions ............................................ 113H 500 Installation procedures.................................................. 113H 600 Contingency procedures ............................................... 113H 700 Arrangement, equipment and instrumentation ............. 113H 800 Requirements for installation........................................ 113

I. Tie-in Operations ................................................................113I 100 General.......................................................................... 113I 200 Installation manual........................................................ 113I 300 Qualification of installation manual ............................. 113I 400 Operating limit conditions ............................................ 113I 500 Tie-in procedures .......................................................... 113I 600 Contingency procedures ............................................... 114I 700 Tie-in operations above water ...................................... 114I 800 Tie-in operations below water ...................................... 114

J. As-Laid Survey...................................................................114J 100 General.......................................................................... 114J 200 Specification of as-laid survey...................................... 114J 300 As-laid survey............................................................... 114J 400 As-laid survey of corrosion protection systems............ 114

K. Span Rectification and Pipeline Protection ........................114K 100 General.......................................................................... 114K 200 Span rectification and protection specification............. 114K 300 Span rectification .......................................................... 115K 400 Trenching...................................................................... 115K 500 Post-installation gravel dumping .................................. 115K 600 Grout bags and concrete mattresses.............................. 115

L. Installation of Protective and Anchoring Structures...........116L 100 General.......................................................................... 116

M. Installation of Risers ...........................................................116M 100 General.......................................................................... 116M 200 Installation manual........................................................ 116M 300 Qualification of the installation manual ....................... 116M 400 Operating limit conditions ............................................ 116M 500 Contingency procedures ............................................... 116M 600 Requirements for installation........................................ 116

N. As-Built Survey ..................................................................116N 100 General.......................................................................... 116N 200 Specification of as-built survey .................................... 116N 300 As-built survey requirements........................................ 117N 400 Inspection of impressed current

cathodic corrosion protection system ........................... 117

O. Final Testing and Preparation for Operation ......................117O 100 General.......................................................................... 117

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O 200 Specification of final testing and preparation for operation ........................................117

O 300 Procedures for final testing and preparation for operation ........................................117

O 400 Cleaning and gauging....................................................117O 500 System pressure testing .................................................118O 600 De-watering and drying ................................................119O 700 Systems testing..............................................................119

P. Documentation.................................................................... 119P 100 General ..........................................................................119

Sec. 11 Operations and Abandonment ........................ 120

A. General................................................................................ 120A 100 Objective .......................................................................120A 200 Scope and application ...................................................120A 300 Responsibilities .............................................................120A 400 Authority and company requirements...........................120A 500 Safety philosophy..........................................................120

B. Commissioning................................................................... 120B 100 General ..........................................................................120B 200 Fluid filling ...................................................................120B 300 Operational verification ................................................120

C. Integrity Management System............................................ 120C 100 General ..........................................................................120C 200 Company policy ............................................................121C 300 Organisation and personnel...........................................121C 400 Condition evaluation and assessment methods .............121C 500 Planning and execution of activities .............................121C 600 Management of change .................................................121C 700 Operational controls and procedures.............................121C 800 Contingency plans.........................................................121C 900 Reporting and communication ......................................121C 1000 Audit and review...........................................................121C 1100 Information management ..............................................121

D. Integrity Management Process ........................................... 122D 100 General ..........................................................................122D 200 Evaluation of threats and condition ..............................122D 300 External inspection........................................................122D 400 In-line inspection...........................................................123D 500 Corrosion monitoring....................................................123D 600 Integrity assessment ......................................................124D 700 Mitigation, intervention and repairs..............................124

E. Re-qualification .................................................................. 125E 100 General ..........................................................................125E 200 Application....................................................................125E 300 Safety level....................................................................125E 400 System pressure test ......................................................125E 500 Deterioration .................................................................125E 600 Design criteria ...............................................................125

F. De-commissioning.............................................................. 126F 100 General ..........................................................................126

G. Abandonment...................................................................... 126G 100 General ..........................................................................126

Sec. 12 Documentation.................................................. 127

A. General................................................................................ 127A 100 Objective .......................................................................127

B. Design................................................................................. 127B 100 Structural .......................................................................127B 200 Linepipe and pipeline components

(including welding) .......................................................127B 300 Corrosion control systems and weight coating .............127B 400 Installation.....................................................................128B 500 Operation.......................................................................128B 600 DFI-Resumé ..................................................................128

C. Construction - Manufacturing and Fabrication .................. 128C 100 Linepipe and pipeline component .................................128C 200 Corrosion control system and weight coating ..............128C 300 DFI-resumé ...................................................................128

D. Construction - Installation and Pre-Commissioning...........128D 100 General ..........................................................................128D 200 DFI-Resumé..................................................................129

E. Operation - Commissioning................................................129E 100 General ..........................................................................129

F. Operation ............................................................................129F 100 General ..........................................................................129F 200 In-Service file................................................................129

G. Abandonment......................................................................129G 100 General ..........................................................................129

H. DFI Resumé ........................................................................129H 100 General ..........................................................................129H 200 DFI resumé content.......................................................129

I. Filing of Documentation.....................................................130I 100 General ..........................................................................130

Sec. 13 Commentary (Informative)............................. 131

A. General................................................................................131A 100 Objective .......................................................................131

B. Cross References ................................................................131

C. Design Philosophy ..............................................................132C 100 Safety Class discussion .................................................132C 200 Structural reliability analyses........................................132C 300 Characteristic values .....................................................133

D. Loads...................................................................................133D 100 Conversion of pressures ................................................133

E. Design Criteria....................................................................133E 100 General ..........................................................................133E 200 Condition load effect factors.........................................133E 300 Calculation of nominal thickness..................................133E 400 Pressure containment - equivalent format.....................134E 500 Pressure containment criterion, incidental

pressure less than 10% above the design pressure. .......134E 600 HIPPS and similar systems ...........................................134E 700 Local buckling - Collapse .............................................135E 800 Buckle arrestor ..............................................................135E 900 Local buckling - Moment..............................................135E 1000 Local buckling - Girth weld factor................................135E 1100 Ovalisation ....................................................................135

F. API Material Grades ...........................................................136F 100 API material grades.......................................................136

G. Components and Assemblies..............................................136G 100 Riser Supports ...............................................................136G 200 J-tubes ...........................................................................136

H. Installation ..........................................................................136H 100 Safety class definition ...................................................136H 200 Coating ..........................................................................136H 300 Simplified laying criteria ..............................................137H 400 Reeling ..........................................................................137

I. References...........................................................................139

App. A Structural Integrity of Girth Welds in Offshore Pipelines ....................................................... 140

A. General................................................................................140A 100 Objective .......................................................................140A 200 Introduction...................................................................140A 300 Application....................................................................140

B. Assessment Categories .......................................................141B 100 General ..........................................................................141

C. Generic ECA for Girth Welds Subject to Strains Less than 0.4% Assessed According to ECA Static – Low .........................143

C 100 General ..........................................................................143

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D. Generic ECA for Girth Welds Subjected to Strains Equal to or Larger than 0.4% but Less Than 2.25% Assessed According to ECA Static – High ........................145

D 100 General.......................................................................... 145

E. Girth Welds under Strain-based Loading Assessed According to ECA Static - Full...........................148

E 100 General.......................................................................... 148E 200 Assessment methodology ............................................. 149

F. Girth Welds Assessed According to ECA Fatigue.............151F 100 General.......................................................................... 151F 200 High-cycle fatigue......................................................... 152F 300 Low-cycle fatigue ......................................................... 152

G. Testing Requirements .........................................................152G 100 General.......................................................................... 152G 200 Straining and ageing ..................................................... 153

H. ECA Validation Testing .....................................................154H 100 General.......................................................................... 154

App. B Mechanical Testing and Corrosion Testing ... 156

A. Mechanical Testing and Chemical Analysis .....................156A 100 General.......................................................................... 156A 200 General requirements to selection and preparation

of samples and test pieces............................................. 156A 300 Chemical analysis ......................................................... 156A 400 Tensile testing ............................................................... 156A 500 Charpy V-notch impact testing ..................................... 157A 600 Bend testing .................................................................. 157A 700 Flattening test................................................................ 158A 800 Drop weight tear test..................................................... 158A 900 Fracture toughness testing ............................................ 158A 1000 Specific tests for clad and lined linepipe ...................... 159A 1100 Metallographic examination and hardness testing........ 159A 1200 Straining and ageing ..................................................... 160A 1300 Testing of pin brazings and aluminothermic welds ...... 161

B. Corrosion Testing ...............................................................161B 100 General.......................................................................... 161B 200 Pitting corrosion test ..................................................... 161B 300 Hydrogen Induced Cracking test .................................. 161B 400 Sulphide Stress Cracking test ....................................... 161

App. C Welding.............................................................. 165

A. Application .........................................................................165A 100 General.......................................................................... 165A 200 Welding processes ........................................................ 165A 300 Definitions .................................................................... 165A 400 Quality assurance.......................................................... 165

B. Welding Equipment, Tools and Personnel .........................165B 100 Welding equipment and tools ....................................... 165B 200 Personnel....................................................................... 166B 300 Qualification and testing of welding personnel

for hyperbaric dry welding .......................................... 166

C. Welding Consumables........................................................166C 100 General.......................................................................... 166C 200 Chemical composition .................................................. 167C 300 Mechanical properties................................................... 167C 400 Batch testing of welding consumables

for pipeline girth welds ................................................. 167C 500 Shielding, backing and plasma gases............................ 168C 600 Handling and storage of welding consumables ............ 168

D. Welding Procedures............................................................168D 100 General.......................................................................... 168D 200 Previously qualified welding procedures...................... 168D 300 Preliminary welding procedure specification ............... 169D 400 Welding procedure qualification record ....................... 169D 500 Welding procedure specification .................................. 169D 600 Welding procedure specification for repair welding .... 169D 700 Contents of pWPS......................................................... 169D 800 Essential variables for welding procedures .................. 170

E. Qualification of Welding Procedures .................................172E 100 General.......................................................................... 172E 200 Repair welding procedures ........................................... 173E 300 Qualification of longitudinal

and girth butt welds welding procedures ..................... 173E 400 Qualification of welding procedures

for corrosion resistant overlay welding ........................ 175E 500 Qualification of procedures

for Pin Brazing and Aluminothermic welding of anode leads ................................................. 176

E 600 Qualification of welding procedures for temporary and permanent attachments and branch welding fittings to linepipe ........................ 176

E 700 Qualification of welding procedures for structural components ................................................................... 177

E 800 Qualification of welding procedures for hyperbaric dry welding ........................................... 177

F. Examination and Testing for Welding Procedure Qualification ......................................................177

F 100 General.......................................................................... 177F 200 Visual examination and non-destructive testing

requirements ................................................................. 178F 300 Testing of butt welds .................................................... 178F 400 Testing of weld overlay ................................................ 179F 500 Testing of pin brazing and aluminothermic welds ...... 180F 600 Testing of welds for temporary and permanent

attachments and branch outlet fittings to linepipe ........ 180

G. Welding and PWHT Requirements ....................................180G 100 General.......................................................................... 180G 200 Production welding, general requirements ................... 180G 300 Repair welding, general requirements .......................... 181G 400 Post weld heat treatment............................................... 182G 500 Welding of pipeline girth welds ................................... 182G 600 Welding and PWHT of pipeline components ............... 183

H. Material and Process Specific Requirements .....................183H 100 Internally clad/lined carbon steel

and duplex stainless steel.............................................. 183H 200 13Cr martensitic stainless steel..................................... 184H 300 Pin brazing and aluminothermic welding ..................... 185

I. Hyperbaric Dry Welding ....................................................185I 100 General.......................................................................... 185I 200 Qualification and testing of welding personnel

for hyperbaric dry welding .......................................... 185I 300 Welding processes for hyperbaric dry welding ............ 186I 400 Welding consumables for hyperbaric dry welding....... 186I 500 Shielding and backing gases

for hyperbaric dry welding ........................................... 186I 600 Welding equipment and systems

for hyperbaric dry welding ........................................... 186I 700 Welding procedures for hyperbaric dry welding .......... 186I 800 Qualification welding for hyperbaric dry welding ....... 187I 900 Qualification of welding procedures

for hyperbaric dry welding ........................................... 187I 1000 Examination and testing ............................................... 187I 1100 Production welding requirements

for dry hyperbaric welding ........................................... 187

App. D Non-Destructive Testing (NDT) ...................... 189

A. General................................................................................189A 100 Objective....................................................................... 189A 200 Applicability of requirements ....................................... 189A 300 Quality assurance.......................................................... 189A 400 Non-destructive testing methods .................................. 189A 500 Personnel qualifications................................................ 189A 600 Timing of NDT............................................................. 190

B. Manual Non-Destructive Testing and Visual Examination of Welds ......................................190

B 100 General.......................................................................... 190B 200 Radiographic testing of welds ...................................... 190B 300 Manual ultrasonic testing of welds in C-Mn/low

alloy steel with C-Mn/low alloy steel weld deposits .... 191B 400 Manual ultrasonic testing of welds with CRA

(duplex, other stainless steels and nickel alloy steel) weld deposits ............................ 194

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B 500 Manual magnetic particle testing of welds ...................195B 600 Manual liquid penetrant testing of welds ......................196B 700 Manual eddy current testing of welds ...........................196B 800 Visual examination of welds.........................................197B 900 Acceptance criteria for manual non-destructive

testing of welds with nominal strains < 0.4% and no ECA...................................................................197

B 1000 ECA based non-destructive testing acceptance criteria for pipeline girth welds .....................................197

B 1100 Repair of welds .............................................................200

C. Manual Non-destructive testing and Visual Examination of Plate, Pipe and Weld Overlay ................... 200

C 100 General ..........................................................................200C 200 Plate and pipe ................................................................201C 300 Weld overlay .................................................................201C 400 Visual examination ......................................................202C 500 Residual magnetism ......................................................202C 600 Acceptance criteria for manual non-destructive

testing of plate, pipe and weld overlay .........................202

D. Non-destructive Testing and Visual Examination of Forgings.......................................................................... 203

D 100 General ..........................................................................203D 200 Ultrasonic and magnetic particle testing

of C-Mn and low alloy steel forgings ...........................203D 300 Ultrasonic and liquid penetrant testing

of duplex stainless steel forgings ..................................204D 400 Visual examination of forgings.....................................205D 500 Acceptance criteria for forgings....................................205

E. Non-destructive Testing and Visual Examination of Castings .......................................................................... 205

E 100 General ..........................................................................205E 200 Ultrasonic and magnetic particle testing

of C-Mn and low alloy steel castings............................205E 300 Ultrasonic and liquid penetrant testing

of duplex stainless steel castings...................................206E 400 Radiographic testing of castings ...................................207E 500 Visual examination of castings .....................................207E 600 Acceptance criteria for castings ....................................207

F. Automated Non-Destructive Testing.................................. 207F 100 General ..........................................................................207F 200 Documentation of function and operation ....................208F 300 Documentation of performance ....................................208F 400 Qualification..................................................................208F 500 Evaluation of performance documentation ...................208

G. Non-Destructive Testing at Plate and Coil Mill ................. 208G 100 General ..........................................................................208G 200 Ultrasonic testing of C-Mn steel and CRA plates.........208G 300 Ultrasonic testing of CRA clad C-Mn steel plate ........209G 400 Alternative test methods................................................209G 500 Disposition of plate and coil

with unacceptable laminations or inclusions ................209G 600 Visual examination of plate and coil.............................209G 700 Acceptance criteria and disposition of surface

imperfections.................................................................209

H. Non-Destructive Testing of Linepipe at Pipe Mills............ 209H 100 General ..........................................................................209H 200 Suspect pipe ..................................................................210H 300 Repair of suspect pipe ...................................................211H 400 General requirements for automated NDT systems ......211H 500 Visual examination and residual magnetism ................213H 600 Non-destructive testing of pipe ends not tested by

automated NDT equipment ...........................................214H 700 Non-destructive testing of pipe ends.............................214H 800 Non-destructive testing of seamless pipe......................215H 900 Non-destructive testing of HFW pipe ...........................215H 1000 Non-destructive testing of CRA liner pipe ...................216H 1100 Non-destructive testing of lined pipe ............................216H 1200 Non-destructive testing of clad pipe .............................217H 1300 Non-destructive testing of SAWL and SAWH pipe .....218H 1400 Manual NDT at pipe mills ............................................220H 1500 Non-destructive testing of weld repair in pipe .............222

App. E Automated Ultrasonic Girth Weld Testing ... 223

A. General................................................................................223A 100 Scope.............................................................................223A 200 References.....................................................................223

B. Basic Requirements ............................................................223B 100 General ..........................................................................223B 200 Documentation ..............................................................224B 300 Qualification..................................................................224B 400 Ultrasonic system equipment and components............224B 500 Calibration (reference) blocks.......................................225B 600 Recorder set-up .............................................................226B 700 Circumferential scanning velocity ................................226B 800 Power supply.................................................................226B 900 Software ........................................................................226B 1000 Reference line, band position and coating cut-back .....226B 1100 Reference line tools.......................................................226B 1200 Operators.......................................................................226B 1300 Spares ............................................................................226B 1400 Slave monitors...............................................................226

C. Procedure ............................................................................227C 100 General ..........................................................................227

D. Calibration (Sensitivity Setting) .........................................227D 100 Initial static calibration..................................................227D 200 Gate settings..................................................................227D 300 Recording Threshold.....................................................228D 400 Dynamic calibration......................................................228D 500 Recording of set-up data ...............................................228

E. Field Inspection ..................................................................228E 100 Inspection requirements ................................................228E 200 Operational checks........................................................229E 300 Adjustments of the AUT system...................................230

F. Re-examination of Welds ...................................................230F 100 General ..........................................................................230

G. Evaluation and Reporting ...................................................230G 100 Evaluation of indications ..............................................230G 200 Examination reports ......................................................230G 300 Inspection records ........................................................230

H. Qualification .......................................................................230H 100 General ..........................................................................230H 200 Scope............................................................................230H 300 Requirements ...............................................................230H 400 Variables .......................................................................231H 500 Qualification programme ..............................................231H 600 Test welds ....................................................................231H 700 Qualification testing .....................................................231H 800 Reference destructive testing .......................................232H 900 Analysis.........................................................................233H 1000 Reporting......................................................................233

I. Validity of Qualification.....................................................233I 100 Validity..........................................................................233I 200 Essential variables.........................................................233

J. Determination of Wave Velocities in Pipe Steels...............233J 100 General ..........................................................................233J 200 Equipment .....................................................................233J 300 Specimens .....................................................................234J 400 Test method...................................................................234J 500 Accuracy .......................................................................234J 600 Recording ......................................................................234

App. F Requirements for Shore Approach and Onshore Sections....................................................... 235

A. Application .........................................................................235A 100 Objective .......................................................................235A 200 Scope and limitation......................................................235A 300 Other codes ..................................................................235A 400 Definitions.....................................................................235

B. Safety Philosophy ...............................................................236B 100 General ..........................................................................236

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B 200 Safety philosophy ......................................................... 236B 300 Quantification of consequence ..................................... 236

C. Design Premise ...................................................................237C 100 General.......................................................................... 237C 200 Routing ......................................................................... 237C 300 Environmental data ....................................................... 237C 400 Survey ........................................................................... 237C 500 Marking......................................................................... 238

D. Design................................................................................. 238D 100 General.......................................................................... 238D 200 System design ............................................................... 238D 300 Design loads.................................................................. 238

D 400 Design criteria............................................................... 238

E. Construction........................................................................239E 100 General.......................................................................... 239E 200 Linepipe ........................................................................ 239E 300 Components and assemblies ......................................... 239E 400 Corrosion protection & coatings................................... 239

F. Operation ............................................................................239F 100 General.......................................................................... 239

G. Documentation....................................................................239G 100 General.......................................................................... 239

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Offshore Standard DNV-OS-F101, October 2007 Sec.1 –

SECTION 1GENERAL

A. GeneralA 100 Introduction101 This standard gives criteria and guidance on conceptdevelopment, design, construction, operation and abandon-ment of Submarine Pipeline Systems.

A 200 Objectives201 The objectives of this standard are to:

— Ensure that the concept development, design, construc-tion, operation and abandonment of pipeline systems aresafe and conducted with due regard to public safety and

the protection of the environment. — provide an internationally acceptable standard of safety

for submarine pipeline systems by defining minimumrequirements for concept development, design, construc-tion, operation and abandonment

— serve as a technical reference document in contractualmatters between Purchaser and Contractor

— serve as a guideline for Designers, Purchaser, and Con-tractors.

A 300 Scope and application301 The scope and applicability of this standard is given inTable 1-1.

1) Example of extra ordinary consequences may be pristine environmentand exploration in arctic climate.

2) Umbilicals intended for control of subsea installations are not included inthis standard. Individual pipes, within an umbilical, made of materials

Table 1-1 Scope and application summaryGeneral

Systems in the petroleum and natural gas industries are in general described in this table. For submarine pipeline systems that have extraordinary consequences, the quantification of con-sequences by the three safety classes provided in this standard may be insufficient, and higher safety classes may be required.1

Phases Concept development, design, construction, operation and abandonmentPipeline Types Dynamic risers and compliant risers are covered by DNV-OS-F201 Dynamic Risers.

Rigid metallic pipeSingle systems, pipeline bundles of the piggyback type and pipeline bundles within an outer pipe2

ExtentPressure and flow Pipeline system in such a way that the fluid transportation and pressure in the submarine pipeline

system is well defined and controlled 3

Concept development, design, construction, operation and abandonment

Submarine pipeline system 4

Geometry and configurationDimensions No limitation

(Explicit criteria for local buckling, combined loading are only given for straight pipes with 15 < D/t < 45)

Water depth No limitation, see Sec.5 A201Loads

Pressure No limitationTemperature No limitation

Material properties need to be documented for temperatures above 50oC and 200C for C-Mn steels and CRAs respectively, see Sec.5 C300

Global deformations No limitationLinepipe Material

General Sec.7 A201 C-Mn steel linepipe is generally conforming to ISO 3183 Annex J but with modifications and amendments.CRA linepipe with specific requirements to duplex stainless steel and 13Cr martensitic steelClad and Lined linepipe.Supplementary requirements for sour service, fracture arrest properties, plastic deformation, dimensional tolerances and high utilization.

Components Bends, Fittings, Flanges, Valves, Mechanical connectors, CP Insulating joints, Anchor flange, Buckle arrestor, Pig traps, Clamps and Couplings

Material and manufacture Sec.8Design Sec.5 F

FluidsCategories Table 2-1Sour service Generally conforming to ISO 15156

InstallationSec.10

Method S-lay, J-lay, towing and laying methods introducing plastic deformationsInstallation requirements for risers as well as protective and anchoring structures are also included.

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Offshore Standard DNV-OS-F101, October 2007 – Sec.1

applicable to this standard, may be designed according to this standard.3) Different parts of the pipeline system may be designed to different codes.

It is important to identify differences between these at an early stage andassess these. Examples of conflicting requirements are; pressure defini-tions and system test pressure requirements.

4) The owner may apply this standard on sub-sets of the limits of this stand-ard. Typical example of excluded items is smaller diameter piping suchas kicker lines and designs these to e.g. ISO 15649.

A 400 Alternative methods and procedures401 In case alternative methods and procedures to thosespecified in this Standard are used, it shall be demonstratedthat the obtained safety level is equivalent to the one specifiedherein, see Sec.2 C500.

A 500 Structure of Standard501 This Standard is based on limit state design. This impliesthat the same design criteria apply to both construction/instal-lation and operation. All structural criteria are therefore givenin Sec.5.502 The Standard is organised as follows:

— Sec.1 contains the objectives and scope of the standard. Itfurther introduces essential concepts, definitions andabbreviations.

— Sec.2 contains the fundamental safety philosophy anddesign principles. It introduces the safety class methodol-ogy and normal classification of safety classes.

— Sec.3 contains requirements to concept development,establishment of design premises, with system designprinciples, pressure protection system, and collection ofenvironmental data.

— Sec.4 defines the design loads to be applied in Sec.5. Itincludes classification of loads into functional loads(including pressure), environmental loads, interferenceloads and accidental loads. Finally, it defines design caseswith associated characteristic values and combinations.

— Sec.5 contains requirements to pipeline layout, system testand mill test. It contains description of the design (LRFD)format and characterisation of material strength forstraight pipes and supports. Design criteria for the differ-ent limit states for all phases; installation, as-laid, commis-sioning and operation, are given.

— Sec.6 contains materials engineering and includes materialselection, material specification (including required sup-plementary requirement to the linepipe specification),welding and corrosion control.

— Sec.7 contains requirements to linepipe. The requirementsto C-Mn steels are based on ISO 3183. The section alsoincludes requirements to CRAs and lined/clad pipe.

— Sec.8 contains requirements to materials, manufacture andfabrication of components and assemblies. Structuralrequirements to these components are given in Sec.5 F.

— Sec.9 contains requirements to corrosion protection andweight coating.

— Sec.10 contains requirements to installation including pre-and post-intervention and pre-commissioning.

— Sec.11 contains requirements to operation including com-missioning, integrity management, repair, re-qualifica-tion, de-commissioning and abandonment of thesubmarine pipeline system.

— Sec.12 contains requirements to documentation for thesubmarine pipeline system from concept development toabandonment.

— Sec.13 is an informative section which discusses severalaspects of the standard.

— The appendices are a compulsory part of the standard.— Appendix A contains the requirements to engineering crit-

ical assessment (ECA). It includes methodology, materialcharacterisation and testing requirements.

— Appendix B details the requirements to materials testingincluding mechanical and corrosion testing as well aschemical analysis.

— Appendix C contains requirements to welding includingqualification of welding procedures and constructionwelding.

— Appendix D contains requirements to Non-DestructiveTesting (NDT) except Automated Ultrasonic Testing(AUT) of girth welds.

— Appendix E contains requirements to AUT of girth welds.— Appendix F contains selected requirements to onshore

parts of the submarine pipeline system.

503 Cross references are made as:

— nnn within the same sub-section (e.g. 512)— X or Xnnn to another sub-section within the same section

(e.g. C, C500 or C512)— Section m, Section mX or Section mXnnn to section, sub-

section or paragraph outside the current section (e.g.Sec.5, Sec.5 C, Sec.5 C500 or Sec.5 C512).

Where m and nnn denotes numbers and X letter.504 Additional requirements or modified requirements com-pared to ISO 3183 are denoted by AR or MR by the end of theparagraph, see Sec.7 B102.

A 600 Other codes601 In case of conflict between requirements of this code anda referenced DNV Offshore Code, the requirements of thecode with the latest revision date shall prevail.

Guidance note:DNV Offshore code means any DNV Offshore Service Specifi-cation, DNV Offshore Standard, DNV Offshore RecommendedPractice, DNV Guideline or DNV Classification Note. Any conflict is intended to be removed in next revision of thatdocument.

---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---

602 Where reference is made to codes other than DNV doc-uments, the valid revision shall be taken as the revision whichwas current at the date of issue of this standard, unless other-wise noted.603 In case of conflict between requirements of this code andcode other than a DNV document, the requirements of thiscode shall prevail.604 This standard is intended to comply with the ISO stand-ard 13623: Petroleum and natural gas industries - Pipelinetransportation systems, specifying functional requirements foroffshore pipelines and risers.

Guidance note:The following major deviations to the ISO standard are known:- This standard allows higher utilisation for fluid category A

and C pipelines. This standard is here in compliance withISO16708.

- For design life less than 33 years, a more severe environmen-tal load is specified, in agreement with ISO16708.

- applying the supplementary requirements U, for increasedutilisation, this standard allows 4% higher pressure contain-ment utilisation than the ISO standard.

- the equivalent stress criterion in the ISO standard sometimesallows higher utilisation than this standard.

- requirements to system pressure test (pressure test).- minor differences may appear depending on how the pipeline

has been defined in safety classes, the ISO standard does notuse the concept of safety classes.

This standard requires that the manufacture of line pipe and con-struction is performed to this standard.


605 The requirements to C-Mn steel linepipe of this standardinclude amendments and modifications that are additional toISO 3183.

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B. ReferencesB 100 Offshore Service SpecificationsThe latest revision of the following documents applies:

B 200 Offshore StandardsThe following documents contain provisions which, throughreference in this text, constitute provisions of this OffshoreStandard. The latest revision of the following documentapplies.

B 300 Recommended PracticesThe latest revision of the following documents applies:

B 400 RulesThe latest revision of the following documents applies:

B 500 Certification notes and classification notesThe latest revision of the following documents applies:

B 600 Other references

DNV-OSS-301 Certification and Verification of PipelinesDNV-OSS-302 Certification and verification of Dynamic

RisersDNV-OSS-401 Technology Qualification Management

DNV-OS-A101 Safety Principles And Arrangements DNV-OS-C101 Design of Offshore Steel Structures, Gen-

eral (LRFD method)DNV-OS-C501 Composite ComponentsDNV-OS-E201 Oil And Gas Processing Systems DNV-OS-F201 Dynamic Risers

DNV-RP-A203 Qualification Procedures for New Technol-ogy

DNV-RP-B401 Cathodic Protection DesignDNV-RP-C203 Fatigue Strength Analysis of Offshore Steel

StructuresDNV-RP-C205 Environmental Conditions and

Environmental LoadsDNV-RP-F101 Corroded PipelinesDNV-RP-F102 Pipeline Field Joint Coating & Field Repair

of Linepipe CoatingDNV-RP-F103 Cathodic Protection of Submarine Pipelines

by Galvanic AnodesDNV-RP-F105 Free Spanning PipelinesDNV-RP-F106 Factory applied pipeline coatings for corro-

sion controlDNV-RP-F107 Risk Assessment of Pipeline ProtectionDNV-RP-F108 Fracture Control for Pipeline Installation

Methods Introducing Cyclic Plastic StrainDNV-RP-F109 On-bottom Stability Design of Submarine

PipelinesDNV-RP-F110 Global Buckling of Submarine Pipelines -

Structural Design due to High Temperature/High Pressure

DNV-RP-F111 Interference between Trawl Gear and Pipe-lines

DNV-RP-F112 Design of Duplex Stainless Steel Subsea Equipment Exposed to Cathodic Protection, Draft Issue April 2006

DNV-RP-F113 Pipeline Subsea RepairDNV-RP-F204 Riser FatigueDNV-RP-H101 Risk Management in Marine and Subsea

OperationsDNV-RP-H102 Marine Operations during Removal of Off-

shore InstallationsDNV-RP-O501 Erosive Wear in Piping Systems - Summary

DNV Rules for Certification of Flexible Risers and Pipes

DNV Rules for Classification of High Speed, Light Craft and Naval Surface Craft

DNV Rules for Planning and Execution of Marine Operations

DNV Rules for Classification of Fixed Offshore Installations

DNV CN 1.2 Conformity Certification Services, Type Approval

DNV CN 1.5 Conformity Certification Services, Approval of Manufacturers, Metallic Mate-rials

DNV CN 7 Non Destructive TestingDNV CN 30.4 FoundationsDNV CN 30.6 Structural Reliability Analysis of Marine

Structures

API RP5L1 Recommended Practice for Railroad transportation of Line Pipe

API5LW Recommended Practice for Transpor-tation of Line Pipe on Barges and Marine Vessels

API RP 2201 Safe Hot Tapping Practices in the Petroleum & Petrochemical Indus-tries-Fifth Edition

ASME/ANSI B16.9 Factory-Made Wrought Buttwelding Fittings

ASME B31.3 2004 Process PipingASME B31.4 2006 Pipeline Transportation Systems

for Liquid Hydrocarbons and Other Liquids

ASME B31.8 2003 Gas Transmission and Distribu-tion Systems

ASME BPVC-V BPBV Section V - Non-destructive Examination

ASME BPVC-VIII-1 BPVC Section VIII - Div. 1 - Rules for Construction of Pressure Vessels

ASME BPVC-VIII-2 BPVC Section VIII - Div. 2 - Rules for Construction of Pressure Vessels - Alternative Rules

ASNT Central Certification Program (ACCP).

ASTM D 695 Standard Test Method for Compres-sive Properties of Rigid Plastics

ASTM A388 Specification for Ultrasonic Examina-tion of Heavy Steel Forgings

ASTM A578/578M Standard Specification for Straight-Beam Ultrasonic Examination of Plain and Clad Steel Plates for Special Applications

ASTM A577/577M Standard specification for Ultrasonic Angle-Beam Examination of Steel Plates

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ASTM A609 Standard Practice for Castings, Low Alloy, and Martensitic Stainless Steel, Ultrasonic Examination Thereof

ASTM A 961 Standard Specification for Common Requirements for Steel Flanges, Forged Fittings, Valves, and Parts for Piping Applications

ASTM E165 Standard Test method for Liquid Pen-etrant Inspection

ASTM E280 Standard Reference Radiographs for Heavy-Walled (4 1/2 to 12-in. (114 to 305-mm)) Steel Castings

ASTM E309 Standard Practice for Eddy-Current Examination of Steel Tubular prod-ucts Using Magnetic Saturation

ASTM E 317-94 Standard Practice for Evaluating Per-formance Characteristics of Pulse Echo Testing Systems Without the Use of Electronic Measurement Instruments

ASTM E426 Standard Practice for Electromagnetic (Eddy Current) of Welded and Seam-less Tubular Products, Austenitic Stainless Steel and Similar Alloys

ASTM E 709 Standard Guide for Magnetic Particle Examination

ASTM E797 Standard Practice for Measuring Thickness by Manual Ultrasonic Pulse-Echo Contact Method

ASTM E 1212 Standard Practice for Quality Manage-ment Systems for Non-destructive Testing Agencies

ASTM E 1417 Standard Practice for Liquid Penetrant Examination

ASTM E1444 Standard Practice for Magnetic Parti-cle Examination

ASTM G 48 Standard Test Methods for Pitting and Crevice Corrosion Resistance of Stainless Steels and Related Alloys by Use of Ferric Chloride Solution

API 6FA Specification for Fire Test for Valves-Third Edition; Errata 12/18/2006

API RP 2201 Safe Hot Tapping Practices in the Petroleum & Petrochemical Indus-tries-Fifth Edition

AWS C5.3 Recommended Practices for Air Car-bon Arc Gouging and Cutting

BSI BS 7910 Guide to methods for assessing the acceptability of flaws in metallic structures

BSI PD 5500 Specification for Unfired fusion welded pressure vessels

EN 287-1 Qualification test of welders - Fusion welding - Part 1:Steels

EN 439 Welding consumables - Shielding gases for arc welding and cutting

EN 473 Non destructive testing - Qualification and certification of NDT personnel - General principles

EN 583-6 Non destructive testing - Ultrasonic examination Part 6 - Time-offlight diffraction as a method for defect detection and sizing

EN 1418 Welding personnel - Approval testing of welding operators for fusion weld-ing and resistance weld setters for fully mechanized and automatic weld-ing of metallic materials

EN 1591-1 Flanges and their joints - Design rules for gasketed circular flange connec-tions - Part 1: Calculation method

EN 1998 Eurocode 8: Design of structures for earthquake resistance

EN 10204 Metallic products - Types of inspec-tion documents

EN 12668-1 Non destructive testing - Characterisa-tion and verification of ultrasonic examination equipment- Part 1: Instruments

EN 12668-2 Non destructive testing - Characterisa-tion and verification of ultrasonic examination equipment- Part 2: Trans-ducers

EN 12668-3 Non destructive testing - Characterisa-tion and verification of ultrasonic examination equipment- Part: 3: Com-bined equipment

EN 13445 Unfired pressure vessels - Part 3: Design

EN 26847 Covered electrodes for manual metal arc welding. Deposition of a weld metal pad for chemical analysis

IMO 23rd Session 2003 (Res. 936-965)ISO 3183 Petroleum and natural gas industries -

Steel pipe for pipeline transportation systems

ISO 2400 Welds in steel -- Reference block for the calibration of equipment for ultra-sonic examination

ISO 3690 Welding and allied processes -- Deter-mination of hydrogen content in fer-reted steel arc weld metal

ISO 4063 Welding and allied processes -- Nomenclature of processes and refer-ence numbers

ISO 5817 Welding - Fusion-welded joints in steel, nickel, titanium and their alloys (beam welding excluded) - Quality levels for imperfections

ISO 6847 Welding consumables -- Deposition of a weld metal pad for chemical analysis

ISO 7005-1 Metallic flanges – Part 1: Steel Flanges

ISO 7963 Non-destructive testing -- Ultrasonic testing --- Specification for calibration block No. 2

ISO 9000 Quality management systems -- Fun-damentals and vocabulary

ISO 9001 Quality management systems - Requirements

ISO 9001 Quality systems -- Model for quality assurance in production, installation and servicing

ISO 9303 Seamless and welded (except sub-merged arc-welded) steel tubes for pressure purposes - Full peripheral ultrasonic testing for the detection of longitudinal imperfections

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ISO 9304 Seamless and welded (except sub-merged arc-welded) steel tubes for pressure purposes- Eddy current test-ing for the detection of imperfections

ISO 9305 Seamless tubes for pressure purposes - Full peripheral ultrasonic testing for the detection of transverse imperfec-tions

ISO 9402 Seamless and welded (except sub-merged arc welded) steel tubes for pressure purposes - Full peripheral magnetic transducer/ flux leakage test-ing of ferromagnetic steel tubes for the detection of longitudinal imperfec-tions

ISO 9598 Seamless steel tubes for pressure pur-poses - Full peripheral magnetic trans-ducer/flux leakage testing of ferromagnetic steel tubes for the detection of transverse imperfections

ISO 9606-1 Approval testing of welders -- Fusion welding -- Part 1: Steels

ISO 9712 Non-destructive testing -- Qualifica-tion and certification of personnel

ISO 9764 Electric resistance welded steel tubes for pressure purposes - Ultrasonic test-ing of the weld seam for longitudinal imperfections

ISO 9765 Submerged arc-welded steel tubes for pressure purposes - Ultrasonic testing of the weld seam for the detection of longitudinal and/or transverse imper-fections

ISO 10124 Seamless and welded (except sub-merged arc-welded) steel tubes for pressure purposes - Ultrasonic testing for the detection of laminar imperfec-tions

ISO 10375 Non-destructive testing -- Ultrasonic inspection -- Characterization of search unit and sound field

ISO 10543 Seamless and hot-stretch reduced welded steel tubes for pressure pur-poses - Full peripheral ultrasonic thickness testing

ISO 10474 Steel and steel productsISO 10497 Testing of Valves - Fire Type-Testing

Requirements-Second EditionISO 11484 Steel tubes for pressure purposes --

Qualification and certification of non-destructive testing (NDT) personnel

ISO 11496 Seamless and welded steel tubes for pressure purposes - Ultrasonic testing of tube ends for the detection of lami-nar imperfections

ISO 12094 Welded steel tubes for pressure pur-poses - Ultrasonic testing for the detection of laminar imperfections in strips or plates used in manufacture of welded tubes

ISO 12095 Seamless and welded steel tubes for pressure purposes - Liquid penetrant testing

ISO 12096 Submerged arc-welded steel tubes for pressure purposes - Radiographic test-ing of the weld seam for the detection of imperfections.

ISO 12715 Ultrasonic non-destructive testing -- Reference blocks and test procedures for the characterization of contact search unit beam profiles

ISO 13623 Petroleum and natural gas industries – Pipeline transportation systems

ISO 13663 Welded steel tubes for pressure pur-poses - Ultrasonic testing of the area adjacent to the weld seam body for detection of laminar imperfections

ISO 13664 Seamless and welded steel tubes for pressure purposes - Magnetic particle inspection of tube ends for the detec-tion of laminar imperfections

ISO 13665 Seamless and welded steel tubes for pressure purposes - Magnetic particle inspection of tube body for the detec-tion of surface imperfections

ISO 14723 Petroleum and natural gas industries - Pipeline transportation systems - Sub-sea pipeline valves

ISO 14731 Welding coordination -- Tasks and responsibilities

ISO14732 Welding personnel -- Approval testing of welding operators for fusion weld-ing and of resistance weld setters for fully mechanized and automatic weld-ing of metallic materials

ISO 15156-1 Petroleum and natural gas industries - Materials for use in H2S-containing environments in oil and gas produc-tion - Part 1: General principles for selection of cracking-resistant materi-als

ISO 15156-2 Petroleum and natural gas industries - Materials for use in H2S-containing environments in oil and gas produc-tion - Part 2: Cracking-resistant carbon and low alloy steels, and the use of cast irons

ISO 15156-3 Petroleum and natural gas industries - Materials for use in H2S-containing environments in oil and gas produc-tion - Part 3: Cracking-resistant CRAs (corrosion-resistant alloys) and other alloys

ISO 15589-2 Petroleum and natural gas industries - Cathodic protection of pipeline trans-portation systems - Part 2: Offshore pipelines

ISO 15590-1 Petroleum and natural gas industries -- Induction bends, fittings and flanges for pipeline transportation systems -- Part 1: Induction bends

ISO 15590-2 Petroleum and natural gas industries -- Induction bends, fittings and flanges for pipeline transportation systems -- Part 2: Fittings

ISO 15590-3 Petroleum and natural gas industries -- Induction bends, fittings and flanges for pipeline transportation systems -- Part 3: Flanges

ISO 15614-1 Specification and qualification of welding procedures for metallic mate-rials -- Welding procedure test -- Part 1: Arc and gas welding of steels and arc welding of nickel and nickel alloys

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Guidance note:The latest revision of the DNV codes may be found in the publi-cation list at the DNV website www.dnv.com.Amendments and corrections to the DNV codes are published bi-annually on www.dnv.com. These shall be considered as manda-tory part of the above codes.


C. DefinitionsC 100 Verbal forms101 Shall: Indicates requirements strictly to be followed inorder to conform to this standard and from which no deviationis permitted.102 Should: Indicates that among several possibilities, one isrecommended as particularly suitable, without mentioning orexcluding others, or that a certain course of action is preferredbut not necessarily required. Other possibilities may be appliedsubject to agreement. The expression may also be used toexpress interface criteria which may be modified subject toagreement.103 May: Verbal form used to indicate a course of action per-missible within the limits of the standard.104 Agreement, by agreement: Unless otherwise indicated,this means agreed in writing between Manufacturer/ Contrac-tor and Purchaser.

C 200 Definitions201 Abandonment: Abandonment comprises the activitiesassociated with taking a pipeline permanently out of operation.An abandoned pipeline cannot be returned to operation.

Depending on the legislation this may require cover orremoval.202 Accidental loads a load with an annual frequency lessthan 10-2, see Sec.5 D1200.203 Accumulated plastic strain: Sum of plastic strain incre-ments, irrespective of sign and direction. Strain incrementsshall be calculated from after the linepipe manufacturing, seeSec.5 D1100.204 Additional requirements: Requirements that applies tothis standard, additional to other referred standards.205 As-built survey: Survey of the installed and completedpipeline system that is performed to verify that the completedinstallation work meets the specified requirements, and to doc-ument deviations from the original design, if any.206 As-laid survey: Survey performed either by continuoustouchdown point monitoring or by a dedicated vessel duringinstallation of the pipeline.207 Atmospheric zone: The part of the pipeline system abovethe splash zone.208 Buckling, global: Buckling mode which involves a sub-stantial length of the pipeline, usually several pipe joints andnot gross deformations of the cross section; upheaval bucklingis an example thereof, see Sec.5 D700.209 Buckling, local: Buckling mode confined to a shortlength of the pipeline causing gross changes of the cross sec-tion; collapse, localised wall wrinkling and kinking are exam-ples thereof, see Sec.5 D300.210 Characteristic load (LSd): The reference value of a loadto be used in the determination of load effects. The character-istic load is normally based upon a defined fractile in the upperend of the distribution function for load, see Sec.4 G.211 Characteristic resistance (RRd): The reference value ofstructural strength to be used in the determination of the designstrength. The characteristic resistance is normally based upona defined fractile in the lower end of the distribution functionfor resistance. See Sec.5 C200.212 Clad pipe (C): Pipe with internal (corrosion resistant)liner where the bond between (linepipe) backing steel andcladding material is metallurgical.213 Clamp: Circumferential structural element, split intotwo or more parts. Examples; connecting two hubs in amechanical connector or two pipe half-shells for repair pur-pose214 Code: Common denotation on any specification, rule,standard guideline, recommended practice or similar.215 Coiled tubing: Continuously-milled tubular productmanufactured in lengths that require spooling onto a take-upreel, during the primary milling or manufacturing process.216 Commissioning; Activities associated with the initialfilling of the pipeline system with the fluid to be transported,part of operational phase.217 Commissioning, De-; Activities associated with takingthe pipeline temporarily out of service.218 Commissioning, Pre-, Activities after tie-in/connectionand prior to commissioning including system pressure testing,de-watering, cleaning and drying.219 Concept development phase: The concept developmentphase will typically include both business evaluations, collect-ing of data and technical early phase considerations.220 Condition load effect factor (γC): A load effect factorincluded in the design load effect to account for specific loadconditions, see Sec.4 G200 Table 4-5.221 Connector: Mechanical device used to connect adjacentcomponents in the pipeline system to create a structural joint

ISO 15618-2 Qualification testing of welders for underwater welding -- Part 2: Diver-welders and welding operators for hyperbaric dry welding

ISO 15649 Petroleum and natural gas industries – Piping

ISO 16708 Petroleum and natural gas industries – Pipeline transportation systems – Reli-ability-based limit state methods

ISO 17636 Non-destructive testing of welds -- Radiographic testing of fusion-welded joints

ISO 17637 Non-destructive testing of welds -- Visual testing of fusion-welded joints

ISO 17638 Non-destructive testing of welds -- Magnetic particle testing

ISO 17640 Non-destructive testing of welds -- Ultrasonic testing of welded joints

ISO 17643 Non-destructive testing of welds -- Eddy current testing of welds by com-plex-plane analysis

MSSSP-55 Quality standard for steel castings for valves, flanges, and fittings and other piping components (visual method).

MSS SP-75 Specification for High Test, Wrought, Butt Welding Fittings

NORDTEST NT Techn. Report 394 (Guidelines for NDE Reliability Determination and Description, Approved 1998-04).

NORSOK L-005 Compact flanged connectionsNS 477 Welding - Rules for qualification of

welding inspectors

DET NORSKE VERITAS


resisting applied loads and preventing leakage. Examples:Threaded types, including (i) one male fitting (pin), one femalefitting (integral box) and seal ring(s), or (ii) two pins, a cou-pling and seals sea rings(s); Flanged types, including twoflanges, bolts and gasket/seal ring; Clamped hub types, includ-ing hubs, clamps, bolts and seal ring(s); Dog-type connectors.222 Construction phase: The construction phase will typi-cally include manufacture, fabrication and installation activi-ties. Manufacture activities will typically include manufactureof linepipe and corrosion protection and weight coating. Fab-rication activities will typically include fabrication of pipelinecomponents and assemblies. Installation activities will typicalinclude pre- and post intervention work, transportation, instal-lation, tie-in and pre-commissioning.223 Contractor: A party contractually appointed by the Pur-chaser to fulfil all, or any of, the activities associated withdesign, construction and operation.224 Corrosion allowance (tcorr): Extra wall thickness addedduring design to compensate for any reduction in wall thick-ness by corrosion (internally/externally) during operation, seeSec.6 D200.225 Corrosion control: All relevant measures for corrosionprotection, as well as the inspection and monitoring of corro-sion, see Sec.6 D100.226 Corrosion protection: Use of corrosion resistant materi-als, corrosion allowance and various techniques for "corrosionmitigation", see Sec.6 D100227 Coupling: Mechanical device to connect two bare pipesto create a structural joint resisting applied loads and prevent-ing leakage.228 Design: All related engineering to design the pipelineincluding both structural as well as material and corrosion.229 Design case: Characterisation of different load catego-ries, see Sec.4 A500.230 Design life: The initially planned time period from ini-tial installation or use until permanent decommissioning of theequipment or system. The original design life may be extendedafter a re-qualification.231 Design premises: A set of project specific design dataand functional requirements which are not specified or whichare left open in the standard to be prepared prior to the designphase.232 Design phase: The design phase will typically be splitinto FEED-phase, basic design and detail design. For eachdesign phase, the same design tasks are repeated but in moreand more specific and detailed level.233 Dynamic riser: A riser which motion will influence thehydrodynamic load effects or where inertia forces become sig-nificant.234 Engineering Critical Assessment (ECA): Fracturemechanics assessment of the acceptability of flaws in metallicmaterials.235 Erosion: Material loss due to repeated impact of sandparticles or liquid droplets.236 Fabrication: Activities related to the assembly ofobjects with a defined purpose in a pipeline system.237 Fabrication factor (γfab): Factor on the material strengthin order to compensate for material strength reduction fromcold forming during manufacturing of linepipe, see Table 5-7.238 Fabricator: The party performing the fabrication.239 Failure: An event affecting a component or system andcausing one or both of the following effects:

— loss of component or system function; or— deterioration of functional capability to such an extent that

the safety of the installation, personnel or environment issignificantly reduced.

240 Fatigue: Cyclic loading causing degradation of thematerial.241 Fittings: Includes: Elbows, caps, tees, single or multipleextruded headers, reducers and transition sections242 Flange: Collar at the end of a pipe usually provided withholes in the pipe axial direction for bolts to permit other objectsto be attached to it.243 Fluid categorisation: Categorisation of the transportedfluid according to hazard potential as defined in Table 2-1.244 Fractile: The p-fractile (or percentile) and the corre-sponding fractile value xp is defined as:

F is the distribution function for xp245 Hub: The parts in a mechanical connector joined by a clamp.246 Hydrogen Induced Cracking (HIC): Internal cracking ofrolled materials due to a build-up of hydrogen pressure inmicro-voids (Related terms: stepwise cracking).247 Hydrogen Induced Stress Cracking (HISC): Crackingthat results from the presence of hydrogen in a metal whilesubjected to tensile stresses (residual and/or applied). Thesource of hydrogen may be welding, corrosion, cathodic pro-tection, electroplating or some other electrochemical process.Crack growth proceeds by a hydrogen embrittlement mecha-nism at the crack tip, i.e. the bulk material is not necessarilyembrittled by hydrogen. HISC by corrosion in presence ofhydrogen sulphide is referred to as Sulphide Stress Cracking(SSC).248 Hydro-test or Hydrostatic test: See Mill pressure test249 Inspection: Activities such as measuring, examination,weighing testing, gauging one or more characteristics of aproduct or service and comparing the results with specifiedrequirements to determine conformity.250 Installation (activity): The operations related to install-ing the equipment, pipeline or structure, e.g. pipeline laying,tie-in, piling of structure etc.251 Installation (object): See Offshore installation.252 Installation Manual (IM): A document prepared by theContractor to describe and demonstrate that the installationmethod and equipment used by the Contractor will meet thespecified requirements and that the results can be verified.253 Integrity: See Pipeline integrity.254 Jointer: Two lengths of pipe welded together by themanufacturer to build up one complete (≈40’) pipe joint.255 J-tube: A J-shaped tube installed on a platform, throughwhich a pipe can be pulled to form a riser. The J-tube extendsfrom the platform deck to and inclusive of the bottom bend atthe seabed. The J-tube supports connect the J-tube to the sup-porting structure.256 Limit state: A state beyond which the structure no longersatisfies the requirements. The following limit states catego-ries are of relevance for pipeline systems:

— Serviceability Limit State (SLS): A condition which, ifexceeded, renders the pipeline unsuitable for normal oper-ations. Exceedance of a serviceability limit state categoryshall be evaluated as an accidental limit state.

— Ultimate Limit State (ULS): A condition which, ifexceeded, compromises the integrity of the pipeline.

— Fatigue Limit State (FLS): An ULS condition accountingfor accumulated cyclic load effects.

— Accidental Limit State (ALS): An ULS due to accidental(in-frequent) loads.

F xp( ) p=

DET NORSKE VERITAS


257 Lined pipe (L): Pipe with internal (corrosion resistant)liner where the bond between (linepipe) backing steel and linermaterial is mechanical.258 Load: Any action causing stress, strain, deformation,displacement, motion, etc. to the equipment or system.259 Load categories: Functional load, environmental load,interference load or accidental load, see Sec.4 A.260 Load effect: Effect of a single load or combination ofloads on the equipment or system, such as stress, strain, defor-mation, displacement, motion, etc.261 Load effect combinations: See Sec.4 A.262 Load effect factor (γF, γE, γA): The partial safety factorby which the characteristic load effect is multiplied to obtainthe design load effect, see Sec.4 G200.263 Load scenarios: Scenarios which shall be evaluated, seeSec.4 A.264 Location class: A geographic area of pipeline system,see Table 2-2.265 Lot: Components of the same size and from the sameheat, the same heat treatment batch.266 Manufacture: Making of articles or materials, often inlarge volumes. In relation to pipelines, refers to activities forthe production of linepipe, anodes and other components andapplication of coating, performed under contracts from one ormore Contractors.267 Manufacturer: The party who is contracted to be respon-sible for planning, execution and documentation of manufac-turing.268 Manufacturing Procedure Specification (MPS): A man-ual prepared by the Manufacturer to demonstrate how the spec-ified properties may be achieved and verified through theproposed manufacturing route.269 Material resistance factor (γm): Partial safety factortransforming a characteristic resistance to a lower fractileresistance, see Sec.5 C200 Table 5-4.270 Material strength factor (αu ): Factor for determinationof the characteristic material strength reflecting the confidencein the yield stress see Sec.5 C300 Table 5-6.271 Mill pressure test: The hydrostatic strength test per-formed at the mill, see Sec.5 B200.272 Nominal outside diameter: The specified outside diame-ter.273 Nominal pipe wall thickness: The specified non-cor-roded pipe wall thickness of a pipe, which is equal to the min-imum steel wall thickness plus the manufacturing tolerance.274 Nominal strain: The total engineering strain notaccounting for strain concentration factors.275 Nominal plastic strain: The nominal strain minus the lin-ear strain derived from the stress-strain curve, see Sec.5Figure 3.276 Offshore installation (object): General term for mobileand fixed structures, including facilities, which are intendedfor exploration, drilling, production, processing or storage ofhydrocarbons or other related activities/fluids. The termincludes installations intended for accommodation of person-nel engaged in these activities. Offshore installation coverssubsea installations and pipelines. The term does not cover tra-ditional shuttle tankers, supply boats and other support vesselswhich are not directly engaged in the activities describedabove.277 Operation, Incidental: Conditions which that are notpart of normal operation of the equipment or system. In rela-tion to pipeline systems, incidental conditions may lead to inci-dental pressures, e.g. pressure surges due to sudden closing of

valves, or failure of the pressure control system and activationof the pressure safety system.278 Operation, Normal: Conditions that arise from theintended use and application of equipment or system, includ-ing associated condition and integrity monitoring, mainte-nance, repairs etc. In relation to pipelines, this should includesteady flow conditions over the full range of flow rates, as wellas possible packing and shut-in conditions where these occuras part of routine operation.279 Operation phase: The operation phase starts with thecommissioning, filling the pipeline with the intended fluid.The operation phase will include inspection and maintenanceactivities. In addition, the operation phase may also includemodifications, re-qualifications and de-commissioning.280 Operator: The party ultimately responsible for conceptdevelopment, design, construction and operation of the pipe-line system. The operator may change between phases.281 Out of roundness: The deviation of the linepipe perime-ter from a circle. This can be stated as ovalisation (%), or aslocal out of roundness, e.g. flattening, (mm).282 Ovalisation: The deviation of the perimeter from a cir-cle. This has the form of an elliptic cross section.283 Partial safety factor: A factor by which the characteris-tic value of a variable is modified to give the design value (i.e.a load effect, condition load effect, material resistance orsafety class resistance factor), see Sec.5 C.284 Pipe, High Frequency Welded (HFW): Pipe manufac-tured by forming from strip and with one longitudinal seamformed by welding without the addition of filler metal. Thelongitudinal seam is generated by high frequency currentapplied by induction or conduction. 285 Pipe, Seamless (SMLS): Pipe manufactured in a hotforming process resulting in a tubular product without awelded seam. The hot forming may be followed by sizing orcold finishing to obtain the required dimensions.286 Pipe, Submerged Arc-Welded Longitudinal or Helical(SAWL or SAWH): Pipe manufactured by forming from stripor plate, and with one longitudinal (SAWL) or helical(SAWH) seam formed by the submerged arc process with atleast one pass made on the inside and one pass from the outsideof the pipe. 287 Pipeline Components: Any items which are integralparts of the pipeline system such as flanges, tees, bends, reduc-ers and valves.288 Pipeline Integrity: Pipeline integrity is the ability of thesubmarine pipeline system to operate safely and withstand theloads imposed during the pipeline lifecycle.289 Pipeline Integrity Management: The pipeline integritymanagement process is the combined process of threat identi-fication, risk assessments, planning, monitoring, inspection,maintenance etc. to maintain pipeline integrity.290 Pipeline System: pipeline with compressor or pump sta-tions, pressure control stations, flow control stations, metering,tankage, supervisory control and data acquisition system(SCADA), safety systems, corrosion protection systems, andany other equipment, facility or building used in the transpor-tation of fluids.See also Submarine pipeline system.291 Pipeline walking: Accumulation of incremental axialdisplacement of pipeline due to start-up and shut-down.292 Pressure control system: In relation to pipelines, this isthe system which, irrespective of the upstream pressure,ensures that the maximum allowable operating pressure is notexceeded, see Figure 1 and Sec.3 B300.293 Pressure protection system: In relation to pipelines, thisis the system for control of the pressure in pipelines, compris-

DET NORSKE VERITAS


ing the Pressure Control System, Pressure Safety System andassociated instrument and alarm systems, see Figure 1 andSec.3 B300.294 Pressure safety system: The system which, independentof the pressure control system, ensures that the allowable inci-dental pressure is not exceeded, see Figure 1 and Sec.3 B300.295 Pressure test: See System pressure test296 Pressure, Collapse (pc): Characteristic resistanceagainst external over-pressure, see Sec.5 D400.297 Pressure, Design (pd): In relation to pipelines, this is themaximum internal pressure during normal operation, referredto a specified reference elevation, see Figure 1 and Sec.3 B300.298 Pressure, Hydro- or Hydrostatic test: See Pressure, Milltest.299 Pressure, Incidental (pinc): In relation to pipelines, thisis the maximum internal pressure the pipeline or pipeline sec-tion is designed to withstand during any incidental operatingsituation, referred to the same reference elevation as the designpressure, see Figure 1 and Sec.3 B300.

Figure 1 Pressure definitions

C 300 Definitions (continuation)301 Pressure, Initiation: The external over-pressure requiredto initiate a propagating buckle from an existing local buckleor dent, see Sec.5 D500.302 Pressure, Local; Local Design, Local Incidental orLocal Test: In relation to pipelines, this is the internal pressureat any point in the pipeline system or pipeline section for thecorresponding design pressure, incidental pressure or test pres-sure adjusted for the column weight, see Sec.4 B200.303 Pressure, Maximum Allowable Incidental (MAIP): Inrelation to pipelines, this is the maximum pressure at which thepipeline system shall be operated during incidental (i.e. tran-sient) operation. The maximum allowable incidental pressureis defined as the maximum incidental pressure less the positivetolerance of the pressure safety system, see Figure 1 andSec.3 B300.304 Pressure, Maximum Allowable Operating (MAOP): Inrelation to pipelines, this is the maximum pressure at which thepipeline system shall be operated during normal operation. Themaximum allowable operating pressure is defined as thedesign pressure less the positive tolerance of the pressure pro-tection system, see Figure 1 and Sec.3 B300.305 Pressure, Mill test (ph): The test pressure applied to pipejoints and pipe components upon completion of manufactureand fabrication, see Sec.5 B200.

306 Pressure, Operation (po): The most probable pressureduring 1-year operation.307 Pressure, Propagating (ppr): The lowest pressurerequired for a propagating buckle to continue to propagate, seeSec.5 D500.308 Pressure, shut-in: The maximum pressure that can beattained at the wellhead during closure of valves closest to thewellhead (wellhead isolation). This implies that pressure tran-sients due to valve closing shall be included.309 Pressure, System test (ptest): In relation to pipelines, thisis the internal pressure applied to the pipeline or pipeline sec-tion during testing on completion of installation work to testthe pipeline system for tightness (normally performed ashydrostatic testing), see Sec.5 B200.310 Pressure, Test: See Pressure, System test.311 Purchaser: The owner or another party acting on hisbehalf, who is responsible for procuring materials, componentsor services intended for the design, construction or modifica-tion of a installation or a pipeline.312 Quality Assurance (QA): Planned and systematicactions necessary to provide adequate confidence that a prod-uct or service will satisfy given requirements for quality. (TheQuality Assurance actions of an organisation is described in aQuality Manual stating the Quality Policy and containing thenecessary procedures and instructions for planning and per-forming the required actions).313 Quality Control (QC): The internal systems and prac-tices (including direct inspection and materials testing), usedby manufacturers to ensure that their products meet therequired standards and specifications.314 Quality Plan (QP): The document setting out the spe-cific quality practices, resources and sequence of activities rel-evant to a particular product, project or contract. A quality planusually makes reference to the part of the quality manual (e.g.procedures and work instructions) applicable to the specificcase.315 Ratcheting: Accumulated deformation during cyclicloading, especially for diameter increase, see Sec.5 D1000.Does not include so called Pipeline Walking.316 Reliability: The probability that a component or systemwill perform its required function without failure, under statedconditions of operation and maintenance and during a speci-fied time interval.317 Re-qualification: The re-assessment of a design due tomodified design premises and/or sustained damage.318 Resistance: The capability of a structure, or part of astructure, to resist load effects, see Sec.5 C200.319 Riser: A riser is defined as the connecting piping or flex-ible pipe between a submarine pipeline on the seabed andinstallations above water. The riser extends to the above seaemergency isolation point between the import/export line andthe installation facilities, i.e. riser ESD valve.320 Riser support/clamp: A structure which is intended tokeep the riser in place.321 Riser system: A riser system is considered to compriseriser, its supports, all integrated pipelining components, andcorrosion protection system.322 Risk: The qualitative or quantitative likelihood of anaccidental or unplanned event occurring, considered in con-junction with the potential consequences of such a failure. Inquantitative terms, risk is the quantified probability of adefined failure mode times its quantified consequence.323 Safety Class (SC): In relation to pipelines; a conceptadopted to classify the significance of the pipeline system withrespect to the consequences of failure, see Sec.2 C400.

PressureProtection

System

Inte

rnal

Pre

ssur

e

Maximum Allowable Incidental Pressure (MAIP)

Incidental PressureIncidental Pressure

Design PressureDesign Pressure Maximum Allowable Operating Pressure (MAOP)

Tolerance of Pressure Safety System

Tolerance of Pressure Safety System

Tolerance of Pressure Control System

Tolerance of Pressure Control System

Pre

ssur

e S

afet

y S

yste

m

Pres

sure

C

ontro

l Sy

stem

Acc

iden

tal

Pre

ssur

e

DET NORSKE VERITAS


324 Safety class resistance factor (γSC): Partial safety factorwhich transforms the lower fractile resistance to a designresistance reflecting the safety class, see Table 5-5.325 Single event: Straining in one direction.326 Slamming: Impact load on an approximately horizontalmember from a rising water surface as a wave passes. Thedirection is mainly vertical.327 Slapping: Impact load on an approximately vertical sur-face due to a breaking wave. The direction is mainly horizontal.328 Specified Minimum Tensile Strength (SMTS): The mini-mum tensile strength prescribed by the specification or stand-ard under which the material is purchased.329 Specified Minimum Yield Stress (SMYS): The minimumyield stress prescribed by the specification or standard underwhich the material is purchased.330 Splash zone: External surfaces of a structure or pipelinethat are periodically in and out of the water by the influence ofwaves and tides.331 Splash Zone Height: The vertical distance betweensplash zone upper limit and splash zone lower limit.332 Splash Zone Lower Limit (LSZ) is determined by:

333 Splash Zone Upper Limit (USZ) is determined by:

334 Splash zone wave-related height: The wave height witha probability of being exceeded equal to 10-2, as determinedfrom the long term distribution of individual waves. If thisvalue is not available, an approximate value of the splash zoneheight may be taken as:0.46 Hs

100

WhereHs

100 = significant wave height with a 100 year return period335 Submarine Pipeline: A submarine pipeline is defined asthe part of a submarine pipeline system which, except for pipe-line risers is located below the water surface at maximum tide,.The pipeline may, be resting wholly or intermittently on, orburied below, the seabed.336 Submarine Pipeline System: a submarine pipeline sys-tem extends to the first weld beyond:

— the first valve, flange or connection above water on plat-form or floater

— the connection point to the subsea installation (i.e. pipingmanifolds are not included)

— the first valve, flange, connection or insulation joint at alandfall unless otherwise specified by the on-shore legisla-tion.

The component above (valve, flange, connection, insulationjoint) includes any pup pieces, i.e. the submarine pipeline sys-tem extends to the weld beyond the pup piece.337 Submerged zone: The part of the pipeline system orinstallation below the splash zone, including buried parts.

338 Supplementary requirements: Requirements for materialproperties of linepipe that are extra to the additional require-ments to ISO and that are intended to apply to pipe used forspecific applications.339 System effects: System effects are relevant in caseswhere many pipe sections are subjected to an invariant loadingcondition, and potential structural failure may occur in connec-tion with the lowest structural resistance among the pipe sec-tions, see Sec.4 G200.340 System pressure test: Final test of the complete pipelinesystem, see Sec.5 B200.341 Target nominal failure probability: A nominal accepta-ble probability of structural failure. Gross errors are notincluded, see Sec.2 C500.342 Temperature, design, maximum: The highest possibletemperature profile to which the equipment or system may beexposed to during installation and operation. 343 Temperature, design, minimum: The lowest possibletemperature profile to which the component or system may beexposed to during installation and operation. This may beapplied locally, see Sec.4 B107344 Test unit: A prescribed quantity of pipe that is made tothe specified outer diameter and specified wall thickness, bythe same pipe-manufacturing process, from the same heat, andunder the same pipe-manufacturing conditions.345 Threats: An indication of impending danger or harm tothe pipeline system.346 Tide: See Sec.3 D300.347 Ultimate Tensile Strength (UTS): The measured ulti-mate tensile strength.348 Verification: An examination to confirm that an activity,a product or a service is in accordance with specified require-ments.349 Weld, strip/plate end: Weld that joins strip or plate joinstogether.350 Work: All activities to be performed within relevant con-tract(s) issued by Owner, Operator, Contractor or Manufac-turer.351 Yield Stress (YS): The measured yield tensile stress.

D. Abbreviations and SymbolsD 100 Abbreviations

LSZ = |L1| - |L2| - |L3|L1 = lowest astronomic tide level (LAT)L2 = 30% of the Splash zone wave-related height

defined in 303L3 = upward motion of the riser.

USZ = |U1| + |U2| + |U3|U1 = highest astronomic tide level (HAT)U2 = 70% of the splash zone wave-related height

defined in 303U3 = settlement or downward motion of the riser, if

applicable

ALS Accidental Limit StateAR Additional Requirement (to ISO 3183), see

Sec.7 B102API American Petroleum InstituteASD Allowable Stress DesignASME American Society of Mechanical EngineersASTM American Society for Testing and MaterialsAUT Automated Ultrasonic TestingBE Best EstimateBM Base materialBS British StandardC Clad pipeC-Mn Carbon ManganeseCP Cathodic ProtectionCRA Corrosion Resistant AlloyCTOD Crack Tip Opening Displacement

DET NORSKE VERITAS


D 200 Symbols201 Latin characters

CVN Charpy V-NotchDAC Distance Amplitude CorrectionDC Displacement controlledDFI Design, Fabrication and InstallationDNV Det Norske VeritasDP Dynamic PositioningDWTT Drop Weight Tear TestingEBW Electron Beam WeldedEC Eddy CurrentECA Engineering Critical AssessmentEDI Electronic Data InterchangeEMS Electro Magnetic StirringERW Electric Resistance WeldingESD Emergency Shut DownFEED Front End Engineering DesignFLS Fatigue Limit StateFMEA Failure Mode Effect AnalysisG-FCAW Gas-Flux Core Arc WeldingGMAW Gas Metal Arc WeldingHAT Highest Astronomical TideHAZ Heat Affected ZoneHAZOP Hazard and Operability StudyHFW High Frequency WeldingHIPPS High Integrity Pressure Protection SystemHIC Hydrogen Induced CrackingHISC Hydrogen Induced Stress CrackingID Internal DiameterIM Installation ManualISO International Organization for StandardizationJ-R curve Plot of resistance to stable crack growth for

establishing crack extensionKV Charpy valueKVL Charpy value in pipe longitudinal directionKVT Charpy value in pipe transversal directionL Lined pipe or load effectLAT Lowest Astronomic TideLB Lower BoundLC Load controlledLBW Laser Beam WeldedLBZ Local Brittle ZonesLRFD Load and Resistance Factor DesignLSZ Splash Zone Lower LimitM/A Martensitic/AusteniteMAIP Maximum Allowable Incidental PressureMAOP Maximum Allowable Operating PressureMDS Material Data SheetMPQT Manufacturing Procedure Qualification TestMPS Manufacturing Procedure SpecificationMR Modified Requirement (to ISO 3183), see

Sec.7 B102MSA Manufacturing Survey ArrangementMWP Multiple Welding ProcessN NormalisedNACE National Association of Corrosion EngineersNDT Non-Destructive TestingOD Outside Diameter

P ProductionPIM Pipeline Integrity ManagementPRE Pitting Resistance EquivalentPRL Primary Reference LevelPTFE Poly Tetra Flour EthylenePWHT Post weld heat treatmentpWPS preliminary Welding Procedure SpecificationQ QualificationQA Quality AssuranceQC Quality ControlQP Quality PlanQRA Quantitative Risk AssessmentQT Quenched and TemperedROV Remotely Operated VehicleRT Radiographic testingSAWH Submerged Arc-welding HelicalSAWL Submerged Arc-welding LongitudinalSC Safety ClassSCF Stress Concentration FactorSCR Steel Catenary RiserSENB Singel Edge Notched Bend fracture mechanics

specimenSENT Single Edge Notched Tension fracture mechan-

ics specimenSLS Serviceability Limit StateSMAW Shielded Metal Arc WeldingSMLS Seamless PipeSMTS Specified Minimum Tensile StrengthSMYS Specified Minimum Yield StressSN Stress versus number of cycles to failureSNCF Strain Concentration FactorSRA Structural Reliability AnalysisSSC Sulphide Stress CrackingST Surface testingTCM Two Curve MethodTMCP Thermo-Mechanical Controlled ProcessTOFD Time of Flight DiffractionTRB Three Roll BendingUB Upper BoundULS Ultimate Limit StateUO Pipe fabrication process for welded pipesUOE Pipe fabrication process for welded pipes,

expandedUSZ Splash Zone Upper LimitUT Ultrasonic testingUTS Ultimate Tensile StrengthWM Weld MetalWPQT Welding Procedure Qualification TestWPS Welding Procedure SpecificationYS Yield Stress

a Crack depthA Cross section area

DET NORSKE VERITAS


D 300 Greek characters

Ae Pipe external cross section area

Ai Pipe internal cross section area

As Pipe steel cross section area

B Specimen widthD Nominal outside diameter.Dfat Miner’s sumDi D-2tnom Nominal internal diameterDmax Greatest measured inside or outside diameterDmin Smallest measured inside or outside diameterE Young's Modulusf0 Ovality

fcb Minimum of fy and fu/1.15, see Eq. 5.9fu Tensile strength to be used in design, see Eq. 5.6fu,temp Derating on tensile stress to be used in design, see

Eq. 5.6fy Yield stress to be used in design, see Eq. 5.5fy,temp Derating on yield stress to be used in design, see

Eq. 5.5g Gravity accelerationH Residual lay tension, see Eq. 4.10 and Eq. 4.11hl Local height at pressure point, see Eq. 4.1Hp Permanent plastic dent depthhref Elevation at pressure reference level, see Eq. 4.1Hs Significant wave heightID Nominal inside diameterk number of stress blocksL Characteristic load effectM MomentN Axial force in pipe wall ("true" force) (tension is

positive) or Number of load effect cyclesni Number of stress blocksNi Number of stress cycles to failure at constant

amplitudeO Out of roundness, Dmax - DminOD Outside nominal diameterpb Pressure containment resistance, see Eq. 5.8pc Characteristic collapse pressure, see Eq. 5.10pd Design pressurePDi (i’th) Damaging event, see Eq. 5.34pe External pressurepel Elastic collapse pressure, see Eq. 5.11pf Failure probabilitypf,T Target nominal failure probabilityph Mill test pressure, see Sec.7 E100pi Characteristic internal pressurepinc Incidental pressurepinit Initiation pressurepld Local design pressurepli Local incidental pressure, see Eq. 4.1plt Local test pressure (system test), see Eq. 4.2pp Plastic collapse pressure, see Eq. 5.12ppr Propagating pressure, see Eq. 5.16

2

4D⋅

π

( )224

tD ⋅−π

( ) ttD ⋅−⋅π

DDD minmax _

ppr,A Propagating buckle capacity of infinite buckle arrestor

pt System test pressure, see Eq. 4.2, 5.1 and 5.2px Crossover pressure, see Eq. 5.18R Global bending radius of pipe, Reaction force or

ResistanceRm Tensile strengthRpx Strength equivalent to a permanent elongation of

x% (actual stress)Rtx Strength equivalent to a total elongation of x%

(actual stress)S Effective axial force (Tension is positive)Sm Resistance to failureSr Ultimate statetc Characteristic thickness to be replaced by t1 or t2

as relevant, see Table 5-2T Temperaturet, tnom Nominal wall thickness of pipe (un-corroded)T0 Testing temperaturet1, t2 Pipe wall thickness, see Table 5-2tcorr Corrosion allowance, see Table 5-2Tc/Tc’ Contingency time for operation/ceasing opera-

tion, see Sec.4 C600tfab Fabrication thickness tolerance, see Table 7-18tm,min Measured minimum thicknessTmax Maximum design temperature, see Sec.4 B100Tmin Minimum design temperature, see Sec.4 B100tmin Minimum thicknessTpop Planned operational period, see Sec.4 C600TR/TR’ Reference period for operation/ceasing opera-

tion, see Sec.4 C600TSafe Planned time to cease operation, see Sec.4 C600TWF Time between generated weather forecasts.W Section modulus or Specimen thickness.Wsub Submerged weight

α Thermal expansion coefficientαc Flow stress parameter, see Eq. 5.22αfab Fabrication factor, see Table 5-7αfat Allowable damage ratio for fatigue, see Table 5-9αgw Girth weld factor (strain resistance), see Eq. 5.30αh

Minimum strain hardeningαp Pressure factor used in combined loading criteria,

see Eq. 5.23αpm Plastic moment reduction factor for point loads,

see Eq. 5.26αU Material strength factor, see Table 5-6β Factor used in combined loading criteriaε Strainεc Characteristic bending strain resistance, see Eq.

5.30εf Accumulated plastic strain resistanceεl.nom Total nominal longitudinal strainεp Plastic strain

max

5,0⎟⎟⎠

⎞⎜⎜⎝

⎛

m

t

RR

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D 400 Subscriptsεr Residual strainεr,rot Residual strain limitγA Load effect factor for accidental load, see

Table 4-4γC Condition load effect factor, see Table 4-5γE Load effect factor for environmental load, see

Table 4-4γε Resistance factor, strain resistance, see Table 5-8γF Load effect factor for functional load, see Table

4-4γinc Incidental to design pressure ratio, see Table 3-1γm Material resistance factor, see Table 5-4γrot Safety factor for residual strainγSC Safety class resistance factor, see Table 5-5η Usage factorκ Curvatureν Poisson’s ratioμ Friction coefficientρcont Density pipeline contentρt Density pipeline content during system pressure

testσ Standard deviation of a variable (e.g. thickness)σe Equivalent stress, Von Mises, see Eq. 5.38σh Hoop stress, see Eq. 5.39σl Longitudinal/axial stress, see Eq. 5.40τ lh Tangential shear stress

A Accidental loadBA Buckle arrestorc Characteristic resistanced Design valueSd Design load (i.e. including load effect factors)Rd Design resistance (i.e. including partial resistance

factors)E Environmental loade Externalel ElasticF Functional loadh Circumferential direction (hoop direction)H Circumferential direction (hoop direction)i InternalL Axial (longitudinal) directionM Momentp PlasticR Radial directions SteelS SLSU ULSX Crossover (buckle arrestors)

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SECTION 2SAFETY PHILOSOPHY

A. General

A 100 Objective101 This section presents the overall safety philosophy thatshall be applied in the concept development, design, construc-tion, operation and abandonment of pipelines.

A 200 Application201 This section applies to all submarine pipeline systemswhich are to be built and operated in accordance with thisstandard.202 The integrity of a submarine pipeline system shall beensured through all phases, from initial concept through tofinal de-commissioning, see Figure 1. This standard definestwo integrity stages: establish integrity in the concept develop-ment, design and construction phases; and maintain integrity inthe operations phase. 203 This section also provides guidance for extension of thisstandard in terms of new criteria, etc.

B. Safety Philosophy Structure

B 100 General101 The integrity of the submarine pipeline system con-structed to this standard is ensured through a safety philosophyintegrating different parts as illustrated in Figure 2.102 The overall safety principles and the arrangement ofsafety systems shall be in accordance with DNV-OS-A101 andDNV-OS-E201.

B 200 Safety objective201 An overall safety objective shall be established, planned

and implemented, covering all phases from conceptual devel-opment until abandonment.

Guidance note:Most companies have a policy regarding human aspects, envi-ronment and financial issues. These are typically on an overalllevel, but may be followed by more detailed objectives andrequirements in specific areas. These policies should be used asa basis for defining the Safety Objective for a specific pipelinesystem. Typical statements may be:

- The impact on the environment shall be reduced to as far asreasonably possible.

- No releases will be accepted during operation of the pipelinesystem.

- There shall be no serious accidents or loss of life during theconstruction period.

- The pipeline installation shall not, under any circumstancesimpose any threat to fishing gear.

- Diverless installation and maintenance.Statements such as those above may have implications for all orindividual phases only. They are typically more relevant for thework execution (i.e. how the Contractor executes his job) andspecific design solutions (e.g. burial or no burial). Havingdefined the Safety Objective, it can be a point of discussion as towhether this is being accomplished in the actual project. It istherefore recommended that the overall Safety Objective be fol-lowed up by more specific, measurable requirements.If no policy is available, or if it is difficult to define the safetyobjective, one could also start with a risk assessment. The riskassessment could identify all hazards and their consequences,and then enable back-extrapolation to define acceptance criteriaand areas that need to be followed up more closely. In this standard, the structural failure probability is reflected inthe choice of three safety classes (see B400). The choice of safetyclass should also include consideration of the expressed safetyobjective.


Figure 1 Integrity assurance activities during the pipeline system phases

*indicates Section in this Standard.

Bus

ines

s dev

elop

men

t

Con

cept

dev

elop

men

t

Bas

ic d

esig

n

Det

ail d

esig

n

Line

pipe

Com

pone

nts a

nd a

ssem

blie

s

Cor

rosio

n pr

otec

tion

and

wei

ght c

oatin

g

Pre-

inte

rven

tion

Insta

llatio

n

Post-

inte

rven

tion

Pre-

com

miss

ioni

ng

Com

miss

ioni

ng

Inte

grity

man

agem

ent

Insp

ectio

n an

d re

pair

Re-

qual

ifica

tion

7 8 9

Construction Operation

Establish Integrity Maintain Integrity

Aba

ndon

men

t

112* & 3 4, 5 & 6 10

Concept Design

DET NORSKE VERITAS


Figure 2 Safety Philosophy structure

B 300 Systematic review of risks301 A systematic review shall be carried out at all phases toidentify and evaluate threats, the consequences of single fail-ures and series of failures in the pipeline system, such that nec-essary remedial measures can be taken. The extent of thereview or analysis shall reflect the criticality of the pipelinesystem, the criticality of a planned operation, and previousexperience with similar systems or operations.

Guidance note:A methodology for such a systematic review is quantitative riskanalysis (QRA). This may provide an estimation of the overallrisk to human health and safety, environment and assets andcomprises:- hazard identification- assessment of probabilities of failure events- accident developments- consequence and risk assessment.The scope of the systematic review should comprise the entirepipeline system, and not just the submarine pipeline system asdefined by this standard.It should be noted that legislation in some countries requires riskanalysis to be performed, at least at an overall level to identifycritical scenarios that might jeopardise the safety and reliabilityof a pipeline system. Other methodologies for identification ofpotential hazards are Failure Mode and Effect Analysis (FMEA)and Hazard and Operability studies (HAZOP).


302 Special attention shall be given to sections close toinstallations or shore approaches where there is frequenthuman activity and thus a greater likelihood and consequenceof damage to the pipeline. This also includes areas where pipe-lines are installed parallel to existing pipelines and pipelinecrossings.

B 400 Design criteria principles401 In this standard, structural safety of the pipeline systemis ensured by use of a safety class methodology. The pipelinesystem is classified into one or more safety classes based onfailure consequences, normally given by the content and loca-tion. For each safety class, a set of partial safety factors isassigned to each limit state.

B 500 Quality assurance501 The safety format within this standard requires that

gross errors (human errors) shall be controlled by requirementsfor organisation of the work, competence of persons perform-ing the work, verification of the design, and quality assuranceduring all relevant phases.502 For the purpose of this standard, it is assumed that theoperator of a pipeline system has established a quality objec-tive. The operator shall, in both internal and external qualityrelated aspects, seek to achieve the quality level of productsand services intended in the quality objective. Further, theoperator shall provide assurance that intended quality is being,or will be, achieved.503 Documented quality systems shall be applied by opera-tors and other parties (e.g. design contractors, manufactures,fabricators and installation contractors) to ensure that prod-ucts, processes and services will be in compliance with therequirements of this standard. Effective implementation ofquality systems shall be documented.504 Repeated occurrence of non-conformities reflecting sys-tematic deviations from procedures and/or inadequate work-manship shall initiate:

— investigation into the causes of the non-conformities— reassessment of the quality system— corrective action to establish possible acceptability of

products— preventative action to prevent re-occurrence of similar

non-conformities.

Guidance note:ISO 9000 give guidance on the selection and use of quality sys-tems.


505 Quality surveillance in the construction phase shall beperformed by the operator or an inspectorate nominated by theoperator. The extent of quality surveillance shall be sufficientto establish that specified requirements are fulfilled and thatthe intended quality level is maintained.506 To ensure safety during operations phase, an integritymanagement system in accordance with Sec.11 C shall beestablished and maintained.

B 600 Health, safety and environment601 The concept development, design, construction, opera-tion and abandonment of the pipeline system shall be con-ducted in compliance with national legislation and companypolicy with respect to health, safety and environmentalaspects.602 The selection of materials and processes shall be con-ducted with due regard to the safety of the public and employ-ees and to the protection of the environment.

C. Risk Basis for Design

C 100 General101 The design format within this standard is based upon alimit state and partial safety factor methodology, also calledLoad and Resistance Factor Design format (LRFD). The loadand resistance factors depend on the safety class, which char-acterizes the consequences of failure.

C 200 Categorisation of fluids201 Fluids to be transported by the pipeline system shall becategorised according to their hazard potential as given byTable 2-1.

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202 Gases or liquids not specifically identified in Table 2-1should be classified in the category containing fluids most sim-ilar in hazard potential to those quoted. If the fluid category isnot clear, the most hazardous category shall be assumed.

C 300 Location classes301 The pipeline system shall be classified into locationclasses as defined in Table 2-2.

C 400 Safety classes401 Pipeline design shall be based on potential failure conse-quence. In this standard, this is implicit by the concept ofsafety class. The safety class may vary for different phases andlocations. The safety classes are defined in Table 2-3.

402 The partial safety factors related to the safety class aregiven in Sec.5 C100.

403 For normal use, the safety classes in Table 2-4 apply:

1) Installation until pre-commissioning (temporary phase) will normally beclassified as safety class Low.

2) For safety classification of temporary phases after commissioning, spe-cial consideration shall be made to the consequences of failure, i.e. givinga higher safety class than Low.

3) Risers during normal operation will normally be classified as safety classHigh.

* Other classifications may exist depending on the conditions and critical-ity of failure the pipeline. For pipelines where some consequences aremore severe than normal, i.e. when the table above does not apply, theselection of a higher safety class shall also consider the implication, onthe total gained safety. If the total safety increase is marginal, the selec-tion of a higher safety class may not be justified.

C 500 Reliability analysis501 As an alternative to the LRFD format specified and usedin this standard, a recognised structural reliability analysisSRA) based design method may be applied provided that:

— the method complies with DNV Classification Note no.30.6 "Structural reliability analysis of marine structures"

— the approach is demonstrated to provide adequate safetyfor familiar cases, as indicated by this standard.

Guidance note:In particular, this implies that reliability based limit state designshall not be used to replace the pressure containment criterion inSec.5 with the exception of accidental loads.


502 Suitably competent and qualified personnel shall performthe structural reliability analysis, and extension into new areas ofapplication shall be supported by technical verification.503 As far as possible, nominal target failure probability lev-els shall be calibrated against identical or similar pipelinedesigns that are known to have adequate safety on the basis ofthis standard. If this is not feasible, the nominal target failureprobability level shall be based on the failure type and safetyclass as given in Table 2-5.

Table 2-1 Classification of fluidsCategory DescriptionA Typical non-flammable water-based fluids.B Flammable and/or toxic fluids which are liquids at

ambient temperature and atmospheric pressure condi-tions. Typical examples are oil and petroleum products. Methanol is an example of a flammable and toxic fluid.

C Non-flammable fluids which are non-toxic gases at ambient temperature and atmospheric pressure condi-tions. Typical examples are nitrogen, carbon dioxide, argon and air.

D Non-toxic, single-phase natural gas.E Flammable and/or toxic fluids which are gases at ambi-

ent temperature and atmospheric pressure conditions and which are conveyed as gases and/or liquids. Typical examples would be hydrogen, natural gas (not otherwise covered under category D), ethane, ethylene, liquefied petroleum gas (such as propane and butane), natural gas liquids, ammonia, and chlorine.

Table 2-2 Classification of locationLocation Definition1 The area where no frequent human activity is antic-

ipated along the pipeline route.2 The part of the pipeline/riser in the near platform

(manned) area or in areas with frequent human activity. The extent of location class 2 should be based on appropriate risk analyses. If no such anal-yses are performed a minimum distance of 500 m shall be adopted.

Table 2-3 Classification of safety classesSafety class

Definition

Low Where failure implies low risk of human injury and minor environmental and economic consequences. This is the usual classification for installation phase.

Medium For temporary conditions where failure implies risk of human injury, significant environmental pollution or very high economic or political consequences. This is the usual classification for operation outside the plat-form area.

High For operating conditions where failure implies high risk of human injury, significant environmental pollution or very high economic or political consequences. This is the usual classification during operation in location class 2.

Table 2-4 Normal classification of safety classes*Phase Fluid Category A, C Fluid Category B, D and E

Location Class Location Class1 2 1 2

Temporary1,2 Low Low - -Operational Low Medium3 Medium High

Table 2-5 Nominal failure probabilities vs. safety classesLimit States

Probability Bases Safety ClassesLow Medium High Very

High4)

SLS Annual per Pipeline1) 10-2 10-3 10-3 10-4

ULS 2) Annual per Pipeline1)

10-3 10-4 10-5 10-6FLS Annual per Pipeline3)

ALS Annual per Pipeline - Pressure containment 10-4-

10-510-5-10-6 10-6-

10-710-7-10-8

1) Or the time period of the temporary phase.2) The failure probability for the bursting (pressure containment) shall be

an order of magnitude lower than the general ULS criterion given in the Table, in accordance with industry practice and reflected by the ISO requirements.

3) The failure probability will effectively be governed by the last year in operation or prior to inspection depending on the adopted inspection philosophy.

4) See Appendix F Table F-2.

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SECTION 3CONCEPT DEVELOPMENT AND DESIGN PREMISES

A. GeneralA 100 Objective101 This section identifies and provides a basis for definitionof relevant field development characteristics. Further, keyissues required for design, construction, operation, and aban-donment of the pipeline system are identified.

A 200 Application201 This section applies to all pipeline systems which are tobe built according to this standard.202 The design premises outlined in this section should bedeveloped during the conceptual phase.

A 300 Concept development301 When selecting the pipeline system concept all aspectsrelated to design, construction, operation and abandonmentshould be considered. Due account should be given to identifi-cation of potential aspects which can stop the concept frombeing realised:

— long lead effects of early stage decisions (e.g. choice ofmaterial grade may affect manufacturing aspects of line-pipe, choice of diameter may give restrictions to installa-tion methods etc.)

— life cycle evaluations (e.g. maintenance activities etc.)— installation aspects for remote areas (e.g. non-availability

of major installation equipment or services and weatherissues).

302 Data and description of field development and generalarrangement of the pipeline system should be established.303 The data and description should include the following,as applicable:

— safety objective— environmental objective— location, inlet and outlet conditions— pipeline system description with general arrangement and

battery limits— functional requirements including field development

restrictions, e.g., safety barriers and subsea valves— installation, repair and replacement of pipeline elements,

valves, actuators and fittings— project plans and schedule, including planned period of

the year for installation— design life including specification for start of design life,

e.g. final commissioning, installation etc.— data of product to be transported including possible

changes during the pipeline system's design life— transport capacity and flow assurance— pressure protection system requirements including process

system layout and incidental to design pressure ratio eval-uations

— pipeline sizing data— attention to possible code breaks in the pipeline system— geometrical restrictions such as specifications of constant

internal diameter, requirement for fittings, valves, flangesand the use of flexible pipe or risers

— relevant pigging scenarios (inspection and cleaning)— pigging fluids to be used and handling of pigging fluids in

both ends of pipeline including impact on process systems— pigging requirements such as bend radius, pipe ovality and

distances between various fittings affecting design for pig-ging applications

— sand production

— second and third party activities— restricted access for installation or other activities due to

presence of ice.

304 An execution plan should be developed, including thefollowing topics:

— general information, including project organisation, scopeof work, interfaces and project development phases

— contacts with Purchaser, authorities, third party, engineer-ing, verification and construction Contractors

— legal aspects, e.g. insurance, contracts, area planning,requirements to vessels.

305 The design and planning for the submarine pipeline sys-tem should cover all development phases including construc-tion, operation and abandonment.

B. System Design Principles

B 100 System integrity101 The pipeline system shall be designed, constructed andoperated in such a manner that:

— the specified transport capacity is fulfilled and the flowassured

— the defined safety objective is fulfilled and the resistanceagainst loads during planned operational conditions is suf-ficient

— the safety margin against accidental loads or unplannedoperational conditions is sufficient.

102 The possibility of changes in the type or composition offluid to be transported during the lifetime of the pipeline sys-tem shall be assessed at the design phase.103 Any re-qualification deemed necessary due to changesin the design conditions shall take place in accordance withprovisions set out in Sec.11.

B 200 Monitoring/inspection during operation201 Parameters which could violate the integrity of a pipe-line system shall be monitored, inspected and evaluated with afrequency which enables remedial actions to be carried outbefore the system is damaged, see Sec.11.

Guidance note:As a minimum the monitoring/inspection frequency should besuch that the pipeline system will not be endangered due to anyrealistic degradation/deterioration that may occur between twoconsecutive inspection intervals.


202 Special focus shall be on monitoring and inspectionstrategies for “live pipeline systems” i.e. pipeline systems thatare designed to change the configuration during its design life.

Guidance note:Example of such systems may be pipelines that are designed toexperience global buckling or possible free-span developments


203 Instrumentation of the pipeline system may be requiredwhen visual inspection or simple measurements are not con-sidered practical or reliable, and available design methods and

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previous experience are not sufficient for a reliable predictionof the performance of the system.204 The need for in-line cleaning and/or inspection, involv-ing the presence of appropriate pig launcher / receiver shouldbe determined in the design phase.

B 300 Pressure Protection System301 A pressure protection system shall be used unless thepressure source to the pipeline system cannot deliver a pres-sure in excess of the incidental pressure including possibledynamic effects. The pressure protection system shall preventthe internal pressure at any point in the pipeline system risingto an excessive level. The pressure protection system com-prises the pressure control system, pressure safety system andassociated instrumentation and alarm systems.

Guidance note:An example of situations where a pressure protection system isnot required is if full shut-in pressure including dynamic effects,is used as incidental pressure.


302 The purpose of the pressure control system is to main-tain the operating pressure within acceptable limits during nor-mal operation i.e. to ensure that the local design pressure is notexceeded at any point in the pipeline system during normaloperation. The pressure control system should operate auto-matically. The local design pressure is defined in Sec.4 B200.Due account shall be given to the tolerances of the pressurecontrol system and its associated instrumentation, see Figure 1in Sec.1. Hence, the maximum allowable operating pressure(MAOP) is equal to the design pressure minus the pressurecontrol system operating tolerance.303 The purpose of the pressure safety system is to protectthe downstream system during incidental operation, i.e. toensure that the local incidental pressure is not exceeded at anypoint in the pipeline system in the event of failure of the pres-sure control system. The pressure safety system shall operateautomatically. Due account shall be given to the tolerances ofthe pressure safety system. Hence, the maximum allowableincidental pressure is equal to the incidental pressure minus thepressure safety system operating tolerance.304 The incidental pressure shall have an annual probabilityof exceedance less than 10-2. If the pressure probability densityfunction does not have a monotonic decay beyond 10-2 thenpressure exceeding the incidental pressure shall be checked asaccidental loads in compliance with Sec.5 D1200. Examples ofpressure probability density distributions are given in Figure 1and Figure 2. See also Sec.4 B200 for definition of the inciden-tal pressure.

Guidance note:When the submarine pipeline system is connected to another sys-tem with different pressure definition the pressure values may bedifferent in order to comply with the requirements of this sub-section, i.e. the design pressure may be different in two con-nected systems. The conversion between the two system defini-tions will often then be based on that the incidental pressures areequal.


Figure 1 Typical maximum pressure distribution – monotonic decay

Figure 2 Schematic illustration of maximum pressure distribution for highintegrity pressure protection systems (HIPPS)

305 For the conditions given in Table 3-1, the given inciden-tal to design ratios shall be used. The incidental to design pres-sure ratio shall be selected in order to meet the requirements in302, 303 and 304.

306 The pipeline system may be divided into sections withdifferent design pressures provided that the pressure protectionsystem ensures that, for each section, the local design pressurecannot be exceeded during normal operations and that the inci-dental pressure cannot be exceeded during incidental opera-tion.

B 400 Hydraulic analyses and flow assurance401 The hydraulics of the pipeline system should be ana-lysed to demonstrate that the pipeline system can safely trans-port the fluids, and to identify and determine the constraintsand requirements for its operation. This analysis should coversteady-state and transient operating conditions.

Table 3-1 Incidental to design pressure ratiosCondition or pipeline system γ incTypical pipeline system 1.10Minimum, except for below 1.05When design pressure is equal to full shut-in pressure including dynamic effects

1.00

System pressure test 1.00

Pressure

Pro

babi

lity

Den

isty

Fun

ctio

n Typical maximum pressure - monotonic decay.

Pressure

Prob

abili

ty D

enis

ty F

unct

ion

Typical maximum pressure distribution for high integrity pressure protection systems (HIPPS).

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Guidance note:Examples of constraints and operational requirements are allow-ances for pressure surges, prevention of blockage such as causedby the formation of hydrates and wax deposition, measures toprevent unacceptable pressure losses from higher viscosities atlower operation temperatures, measures for the control of liquidslug volumes in multi-phase fluid transport, flow regime forinternal corrosion control erosional velocities and avoidance ofslack line operations. It also includes requirements to insulation,maximum shut-down times, requirements for heating etc.


402 The hydraulics of the pipeline system shall be analysedto demonstrate that the pressure control system and pressuresafety system meet its requirement during start-up, normaloperation, shut-down (e.g. closing of valves) and all foreseennon-intended scenarios. This shall also include determinationof required incidental to design pressure ratio.

403 The hydraulic analyses shall be used to determine themaximum design temperature profile based on conservativeinsulation values reflecting the variation in insulation proper-ties of coatings and surrounding seawater, soil and gravel. 404 The hydraulic analyses shall be used to determine theminimum design temperature. Benefit of specifying low tem-peratures locally due to e.g. opening of valves is allowed andshall be documented e.g. by hydraulic analyses.

C. Pipeline RouteC 100 Location101 The pipeline route shall be selected with due regard tosafety of the public and personnel, protection of the environ-ment, and the probability of damage to the pipe or other facil-ities. Agreement with relevant parties should be sought asearly as possible. Factors to take into consideration shall, atminimum, include the following:Environment

— archaeological sites— exposure to environmental damage— areas of natural conservation interest including oyster beds

and corral reefs— marine parks— turbidity flows.

Seabed characteristics

— uneven seabed— unstable seabed— soil properties (hard spots, soft sediment and sediment

transport)— subsidence— seismic activity.

Facilities

— offshore installations— subsea structures and well heads— existing pipelines and cables— obstructions— coastal protection works.

Third party activities

— ship traffic— fishing activity— dumping areas for waste, ammunition, etc.— mining activities— military exercise areas.

Landfall

— local constraints— 3rd party requirements— environmental sensitive areas— vicinity to people— limited construction period.

102 Expected future marine operations and anticipateddevelopments in the vicinity of the pipeline shall be consideredwhen selecting the pipeline route.103 Pipeline components (e.g. valves, tees) in particularshould not be located on the curved route sections of the pipe-line.104 It is recommended that pipeline ends are designed witha reasonable straight length ahead of the target boxes. Curva-tures near pipeline ends should be designed with due regard toend terminations, lay method, lay direction and existing/planned infrastructure.

C 200 Route survey201 Surveys shall be carried out along the total length of theplanned pipeline route to provide sufficient data for design andinstallation related activities.202 The survey corridor shall have sufficient width to definean installation and pipeline corridor which will ensure safeinstallation and operation of the pipeline. 203 The required survey accuracy may vary along the pro-posed route. Obstructions, highly varied seabed topography, orunusually or hazardous sub-surface conditions may dictatemore detailed investigations.204 Investigations to identify possible conflicts with existingand planned installations and possible wrecks and obstructionsshall be performed. Examples of such installations includeother submarine pipelines, and power and communicationcables.205 The results of surveys shall be presented on accurateroute maps and alignments, scale commensurate with requireduse. Location of the pipeline, related facilities together withseabed properties, anomalies and all relevant pipelineattributes shall be shown. Reference seawater elevation shallbe defined.206 Additional route surveys may be required at landfalls todetermine:

— seabed geology and topography specific to landfall andcostal environment

— environmental conditions caused by adjacent coastal fea-tures

— location of the landfall to facilitate installation— facilitate pre or post installation seabed intervention works

specific to landfall, such as trenching— location to minimise environmental impact.

207 All topographical features which may influence the sta-bility and installation or influence seabed intervention of thepipeline shall be covered by the route survey, including but notlimited to:

— obstructions in the form of rock outcrops, large boulders,pock marks, etc., that could necessitate remedial, levellingor removal operations to be carried out prior to pipelineinstallation

— topographical features that contain potentially unstableslopes, sand waves, pock marks or significant depressions,valley or channelling and erosion in the form of scour pat-terns or material deposits.

208 Areas where there is evidence of increased geologicalactivity or significant historic events that if re-occurring againcan impact the pipeline, additional geohazard studies should be

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performed. Such studies may include:

— extended geophysical survey— mud volcanoes or pockmark activity— seismic hazard — seismic fault displacements— possibility of soil slope failure— mudflow characteristics— mudflow impact on pipelines.

C 300 Seabed properties301 Geotechnical properties necessary for evaluating theeffects of relevant loading conditions shall be determined forthe seabed deposits, including possible unstable deposits in thevicinity of the pipeline. For guidance on soil investigation forpipelines, reference is made to Classification Note No. 30.4"Foundations".302 Geotechnical properties may be obtained from generallyavailable geological information, results from seismic surveys,seabed topographical surveys, and in-situ and laboratory tests.Supplementary information may be obtained from visual sur-veys or special tests, as e.g. pipe penetration tests.

303 Soil parameters of main importance for the pipelineresponse are:

— shear strength parameters (intact and remoulded und-rained shear strength for clay, and angle of friction forsands); and

— relevant deformation characteristics.

These parameters should preferably be determined from ade-quate laboratory tests or from interpretation of in-situ tests. Inaddition, classification and index tests should be considered,such as:

— unit weight— water content— liquid and plastic limit— grain size distribution— carbonate content— other relevant tests.

304 It is primarily the characteristics of the upper layer ofsoil that determine the response of the pipeline resting on theseabed. The determination of soil parameters for these veryshallow soils may be relatively more uncertain than for deepersoils. Also the variations of the top soil between soil testinglocations may add to the uncertainty. Soil parameters used inthe design may therefore need to be defined with upper bound,best estimate and lower bound limits. The characteristicvalue(s) of the soil parameter(s) used in the design shall be inline with the selected design philosophy accounting for theseuncertainties.

Guidance note:For deep water areas the upper layer may be slurry with a verysmall strength. In these cases emphasize should also be made tothe soil layer underneath.


305 In areas where the seabed material is subject to erosion,special studies of the current and wave conditions near the bot-tom including boundary layer effects may be required for theon-bottom stability calculations of pipelines and the assess-ment of pipeline spans.306 Additional investigation of the seabed material may berequired to evaluate specific problems, as for example:

— problems with respect to excavation and burial operations— probability of forming frees-pans caused by scouring dur-

ing operational phase

— problems with respect to pipeline crossing— problems with the settlement of pipeline system and/or the

protection structure at the valve/tee locations— possibilities of mud slides or liquefaction as the result of

repeated loading— implications for external corrosion.

D. Environmental ConditionsD 100 General101 Environmental phenomena that might impair properfunctioning of the system or cause a reduction of the reliabilityand safety of the system shall be considered, including:

— wind— tide— waves— internal waves and other effects due to differences in water

density— current— ice— earthquake— soil conditions— temperature— marine growth (fouling).

102 The principles and methods described in DNV-RP-C205Environmental Conditions and Environmental Loads may beused as a basis for establishing the environmental conditions.

D 200 Collection of environmental data201 The environmental data shall be representative for thegeographical areas in which the pipeline system is to beinstalled. If sufficient data are not available for the geographi-cal location in question, conservative estimates based on datafrom other relevant locations may be used.202 Statistical data shall be utilised to describe environmen-tal parameters of a random nature (e.g. wind, waves). Theparameters shall be derived in a statistically valid mannerusing recognised methods.203 The effect of statistical uncertainty due to the amountand accuracy of data shall be assessed and, if significant, shallbe included in the evaluation of the characteristic load effect.204 For the assessment of environmental conditions alongthe pipeline route, the pipeline may be divided into a numberof sections, each of which is characterised by a given waterdepth, bottom topography and other factors affecting the envi-ronmental conditions.205 The environmental data to be used in the design of pipe-lines and/or risers fixed to an offshore structure are in principlethe same as the environmental data used in the design of theoffshore structure supporting the pipeline and/or riser.

D 300 Environmental data301 The estimated maximum tide shall include both astro-nomic tide and storm surge. Minimum tide estimates should bebased upon the astronomic tide and possible negative stormsurge.302 All relevant sources to current shall be considered. Thismay include tidal current, wind induced current, storm surgecurrent, density induced current or other possible phenomena.For near-shore regions, long-shore current due to wave break-ing shall be considered. Variations in magnitude with respectto direction and water depth shall be considered when relevant.303 In areas where ice may develop or where ice bergs maypass or where the soil may freeze sufficient statistics shall beestablished in order to enable calculations of design loads,either environmental or accidental.

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304 Air and sea temperature statistics shall be provided giv-ing representative design values.305 Marine growth on pipeline systems shall be considered,taking into account both biological and other environmentalphenomena relevant for the location.

E. External and Internal Pipe ConditionE 100 External operational conditions101 For the selection and detailed design of external corro-sion control, the following conditions relating to the environ-ment shall be defined, in addition to those mentioned in D101:

— exposure conditions, e.g. burial, rock dumping, etc.— sea water and sediment resistivity.

102 Other conditions affecting external corrosion whichshall be defined are:

— maximum and average operating temperature profilealong the pipeline and through the pipe wall thickness

— pipeline fabrication and installation procedures— requirements for mechanical protection, submerged

weight and thermal insulation during operation— design life— selected coating and cathodic protection system.

103 Special attention should be given to the landfall section(if any) and interaction with relevant cathodic protection sys-tem for onshore vs. offshore pipeline sections.104 The impact on the external pipe condition of the third

party activities as mentioned in C101 above should be consid-ered.

E 200 Internal installation conditions201 A description of the internal pipe conditions during stor-age, construction, installation, pressure testing and commis-sioning shall be prepared. The duration of exposure to seawater or humid air, and the need for using inhibitors or othermeasures to control corrosion shall be considered.

E 300 Internal operational conditions301 In order to assess the need for internal corrosion control,including corrosion allowance and provision for inspectionand monitoring, the following conditions shall be defined:

— maximum and average operating temperature/pressureprofile along the pipeline, and expected variations duringthe design life

— flow velocity and flow regime— fluid composition (initial and anticipated variations during

the design life) with emphasis on potentially corrosivecomponents (e.g. hydrogen sulphide, carbon dioxide,water content and expected content of dissolved salts inproduced fluids, residual oxygen and active chlorine in seawater)

— chemical additions and provisions for periodic cleaning— provision for inspection of corrosion damage and expected

capabilities of inspection tools (i.e. detection limits andsizing capabilities for relevant forms of corrosion damage)

— the possibility of erosion by any solid particles in the fluidshall be considered. Reference is made to DNV-RP-O501Erosive Wear in Piping Systems.

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SECTION 4DESIGN - LOADS

A. GeneralA 100 Objective101 This section defines the design loads to be checked bythe design criteria in Sec.5. This includes:

— load scenarios to be considered— categorisation of loads— design cases and corresponding characteristic loads— load effect combinations— load effect calculations.

A 200 Application201 This section applies to all parts of the submarine pipelinesystem.

A 300 Load scenarios301 All loads and forced displacements which may influencethe pipeline integrity shall be taken into account. For eachcross section or part of the system to be considered and foreach possible mode of failure to be analysed, all relevant com-binations of loads which may act simultaneously shall be con-sidered.302 The most unfavourable scenario for all relevant phasesand conditions shall be considered. Typical conditions to becovered in the design are:

— installation— as laid— water filled— system pressure test— operation— shut-down.

A 400 Load categories401 The objective of categorise the different loads into dif-ferent load categories is to relate the load effect to the differentuncertainties and occurrence.402 Unless the load is categorised as accidental it shall becategorised as:

— functional load— environmental load— interference load.

The load categories are described in B, C and E below. Con-struction loads shall be categorised into the above loads and aredescribed in D. Accidental loads are described in F.

A 500 Design cases501 The design cases describe the 100-year load effect. The100-year load effect is composed of contributions of func-tional, environmental and interference load effects. This willbe governed either by the 100-year functional load effect, the100-year environmental load effect or the 100-year interfer-ence load effect, see G100.

A 600 Load effect combination601 The load combinations combine the load effect of eachload category in a design case with different load effect factors,see G200.Each load combination constitutes a design load effect to becompared with relevant design resistance, see 5 C100.

B. Functional LoadsB 100 General101 Loads arising from the physical existence of the pipelinesystem and its intended use shall be classified as functionalloads.102 All functional loads which are essential for ensuring theintegrity of the pipeline system, during both the constructionand the operational phase, shall be considered.103 Effects from the following phenomena are the minimumto be considered when establishing functional loads:

— weight— external hydrostatic pressure— internal pressure— temperature of contents— pre-stressing— reactions from components (flanges, clamps etc.)— permanent deformation of supporting structure— cover (e.g. soil, rock, mattresses, culverts)— reaction from seabed (friction and rotational stiffness)— permanent deformations due to subsidence of ground, both

vertical and horizontal— permanent deformations due to frost heave— changed axial friction due to freezing — possible loads due to ice interference, e.g. bulb growth

around buried pipelines near fixed points (in-line valves/tees, fixed plants etc.), drifting ice etc.

— loads induced by frequent pigging operations.

104 The weight shall include weight of pipe, buoyancy, con-tents, coating, anodes, marine growth and all attachments tothe pipe.105 End cap forces due to pressure shall be considered, aswell as any transient pressure effects during normal operation(e.g. due to closure of valves).106 Environmental as well as operational temperatures shallbe considered. The maximum and minimum design tempera-ture profiles shall have an annual probability of exceedanceless than of 10-2. Different temperature profiles for differentconditions should be considered (e.g. installation, as-laid,water filled, pressure test, operation and design).107 Local minimum temperature profiles, which may becaused by e.g. sudden shut-downs, may be applied. This willtypically be relevant to defined components and sections of thepipeline (e.g. spots around valves).108 Fluctuations in temperature shall be taken into accountwhen checking fatigue strength.109 For expansion analyses, the temperature difference rela-tive to laying shall be considered. The temperature profile shallbe applied.110 Pre-stressing, such as permanent curvature or a perma-nent elongation introduced during installation, shall be takeninto account if the capacity to carry other loads is affected bythe pre-stressing. Pretension forces induced by bolts in flanges,connectors and riser supports and other permanent attach-ments, shall be classified as functional loads.111 The soil pressure acting on buried pipelines shall betaken into account if significant.

B 200 Internal Pressure loads201 The following internal pressures shall be defined at a cer-tain defined reference level; System Test Pressure, Operating

DET NORSKE VERITAS


Pressure (if relevant), Design pressure (if applicable), and Inci-dental Pressure, see Sec.3 B300 for definitions and Figure 1 in

Sec.1. These pressures are summarised in Table 4-1.

Guidance note:The incidental pressure is defined in terms of annual exceedanceprobability. The ratio between the incidental pressure and thedesign pressure, see Table 3-1, is determined by the accuracy ofthe pressure protection system. When the pressure source isgiven (e.g. well head shut-in pressure) this may constitute theselection of the incidental pressure. The design pressure can thenbe established based on the pressure protection system. Whentransport capacity requirement constitute the design premise thismay give the design pressure and the incidental pressure can thenbe established based on the pressure protection system.


202 The local pressure is the internal pressure at a specificpoint based on the reference pressure adjusted for the fluid col-umn weight due to the difference in elevation. It can beexpressed as:

wherepli is the local incidental pressurepinc is the incidental reference pressure at the reference ele-

vationρcont is the density of the relevant content of the pipelineg is the gravityhref is the elevation of the reference point (positive

upwards)hl is the elevation of the local pressure point (positive

upwards)plt is the local system test pressurept is the system test reference pressure at the reference ele-

vationρt is the density of the relevant test medium of the pipeline203 The test pressure requirement is given in Sec.5 B200.

B 300 External Pressure loads301 In cases where external pressure increases the capacity,the external pressure shall not be taken as higher than the waterpressure at the considered location corresponding to low astro-nomic tide including possible negative storm surge.302 In cases where the external pressure decreases thecapacity, the external pressure shall not be taken as less thanthe water pressure at the considered location corresponding tohigh astronomic tide including storm surge.

C. Environmental LoadsC 100 General101 Environmental loads are defined as those loads on thepipeline system which are caused by the surrounding environ-ment, and that are not otherwise classified as functional oraccidental loads.102 For calculation of characteristic environmental loads,reference is made to the principles given in DNV-RP-C205Environmental Conditions and Environmental Loads.

C 200 Wind loads201 Wind loads shall be determined using recognised theo-retical principles. Alternatively, direct application of data fromadequate tests may be used.202 The possibility of vibrations and instability due to windinduced cyclic loads shall be considered (e.g. vortex shed-ding).

C 300 Hydrodynamic loads301 Hydrodynamic loads are defined as flow-induced loadscaused by the relative motion between the pipe and the sur-rounding water. 302 All relevant sources for hydrodynamic loads shall beconsidered. This may include waves, current, relative pipemotions and indirect forces e.g. caused by vessel motions.303 The following hydrodynamic loads shall be considered,but not limited to:

— drag and lift forces which are in phase with the absolute orrelative water particle velocity

— inertia forces which are in phase with the absolute or rela-tive water particle acceleration

— flow-induced cyclic loads due to vortex shedding, gallop-ing and other instability phenomena

— impact loads due to wave slamming and slapping, and— buoyancy variations due to wave action.

Guidance note:Recent research into the hydrodynamic coefficients for openbundles and piggy-back lines indicates that the equivalent diam-eter approach may be unconservative, and a system specific CFDanalysis may be required to have a robust design.


304 The applied wave theory shall be capable of describingthe wave kinematics at the particular water depth in questionincluding surf zones hydrodynamics where applicable. Thesuitability of the selected theory shall be demonstrated anddocumented.

Table 4-1 Pressure termsPressure Abbreviations Symbol DescriptionMill test - Ph Hydrostatic test pressure at the mill, see Sec.7System test - Pt The pressure to which the complete submarine pipeline system is tested

to prior to commissioning, see Sec.5 B200Incidental - Pinc Maximum pressure the submarine pipeline system is designed forMaximum allowable incidental MAIP - The trigger level of pressure safety system. Maximum allowable inciden-

tal pressure is equal to the incidental pressure minus the pressure safety system operating tolerance

Design - PD The maximum pressure the pressure protection system requires in order to ensure that incidental pressure is not exceeded with sufficient reliabil-ity, typically 10% below the incidental pressure

Maximum allowable operating MAOP - Upper limit of pressure control system. Maximum allowable operating pressure is equal to the design pressure minus the pressure control system operating tolerance

(4.1)

(4.2)

( )lrefcontincli hhgpp −⋅⋅+= ρ

( )lrefttlt hhgpp −⋅⋅+= ρ

DET NORSKE VERITAS


305 The current-induced drag and lift forces on the subma-rine pipeline system shall be determined and combined withthe wave-induced forces using recognised theories for wave-current interaction. A vector combination of the current andwave-induced water particle velocities may be used. If availa-ble, however, calculation of the total particle velocities andaccelerations based upon more exact theories on wave-currentinteraction is preferable.306 Data from model testing or acknowledged industry prac-tice may be used in the determination of the relevant hydrody-namic coefficients.307 Where appropriate, consideration shall be given to wavedirection, short crested waves, wave refraction and shoaling,shielding and reflecting effects.308 For pipelines during installation and for in-place risers,the variations in current velocity magnitude and direction as afunction of water depth shall be considered.309 Where parts of the pipeline system are positioned adja-cent to other structural parts, possible effects due to distur-bance of the flow field shall be considered when determiningthe wave and/or current actions. Such effects may cause anincreased or reduced velocity, or dynamic excitation by vorti-ces being shed from the adjacent structural parts.310 If parts of the submarine pipeline system is built up of anumber of closely spaced pipes, then interaction and solidifi-cation effects shall be taken into account when determining themass and drag coefficients for each individual pipe or for thewhole bundle of pipes. If sufficient data is not available, large-scale model tests may be required.311 For pipelines on or close to a fixed boundary (e.g. pipe-line spans) or in the free stream (e.g. risers), lift forces perpen-dicular to the axis of the pipe and perpendicular to the velocityvector shall be taken into account (possible vortex inducedvibrations).312 In connection with vortex shedding-induced transversevibrations, the increase in drag coefficient shall be taken intoaccount.313 Possible increased waves and current loads due to pres-ence of Tee’s, Y’s or other attachments shall be considered.314 The effect of possible wave and current loading on thesubmarine pipeline system in the air gap zone shall beincluded.

Guidance note:Maximum wave load effects may not always be experienced dur-ing the passing of the design wave. The maximum wave loadsmay be due to waves of a particular length, period or steepness.The initial response to impulsive wave slam or slap usuallyoccurs before the exposed part of the submarine pipeline systemis significantly immersed. Therefore, other fluid loading on thesystem need not normally be applied with the impulsive load.However, due to structural continuity of the riser, global waveloading on other parts of the system must be considered in addi-tion to the direct wave loading.Wave slam occurs when an approximately horizontal member isengulfed by a rising water surface as a wave passes. The highestslamming forces occur for members at mean water level and theslam force directions are close to the vertical.Wave slap is associated with breaking waves and can affectmembers at any inclination, but in the plane perpendicular to thewave direction. The highest forces occur on members abovemean water level.Both slam and slap loads are applied impulsively (over a shortinstant of time) and the dynamic response of the submarine pipe-line system shall be considered.


315 Parts of the submarine pipeline system, located above

the normal wave impact zone, may be exposed to wave loadingdue to wave run-up. Loads due to this effect shall be consid-ered if relevant.316 The increased loads from marine growth shall be consid-ered as follows:

— Increased drag/lift area due to the marine growth — Increased pipe surface roughness and resulting increase in

drag coefficient and reduced lift coefficient— Any beneficial effect of the weight of the marine growth

shall be ignored in stability analyses

317 Tide loads shall be considered when the water depth is asignificant parameter, e.g. for the establishment of waveactions, pipe lay operation particularly near shore approaches/landfalls, etc.

C 400 Ice loads401 In areas where ice may develop or drift, the possibilityof ice loads on the pipeline system shall be considered. Suchloads may partly be due to ice frozen on the pipeline systemitself, and partly due to floating ice. For shore approaches andareas of shallow water, the possibility of ice scouring andimpacts from drifting ice shall be considered. Increased hydro-dynamic loading due to presence of ice shall be considered.The ice load may be classified as environmental or accidentaldepending on its frequency.402 In case of ice frozen to parts of the submarine pipelinesystem, (e.g. due to sea spray) the following forces shall beconsidered:

— weight of the ice— impact forces due to thaw of the ice— forces due to expansion of the ice— increased wind, waves and current forces due to increased

exposed area.

403 Forces from floating ice shall be calculated according torecognised theory. Due attention shall be paid to the mechani-cal properties of the ice, contact area, shape of structure, direc-tion of ice movements, etc. The oscillating nature of the iceforces (built-up of lateral force and fracture of moving ice)shall be taken into account in the structural analysis. Whenforces due to lateral ice motion will govern structural dimen-sions, model testing of the ice-structure interaction may berequired.

C 500 Earthquake501 Load imposed by earth quake, either directly or indi-rectly (e.g. due to failure of pipeline gravel supports), shall beclassified into accidental or environmental loads, dependingon the probability of earthquake occurrence in line with acci-dental loads in F.

Guidance note:Earth quake with 475 years return period may be taken fromInternational seismic zonation charts as in Eurocode 8. This canthen be converted by importance factors to 100 years returnperiod.


C 600 Characteristic environmental load effects601 The characteristic environmental load and the corre-sponding load effect depend on condition:

— weather restricted condition— temporary condition— permanent condition.

See Figure 1.

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Figure 1 Determination of characteristic environmental load

602 An operation can be defined as weather restricted oper-ation if it is anticipated to take less than 72 hours from previousweather forecast including contingency time, referred to asoperation reference period, TR. It may then start-up based onreliable weather forecast less than established operation limit.Uncertainty in the weather forecast for the operational periodshall be considered.603 An operation can be defined as weather restricted oper-ation even if the operation time is longer than 72 hours giventhat it can be ceased and put into safe condition within 72 hoursincluding contingency time and weather forecast intervals,referred to as operational reference period of ceasing opera-tion, T’R. The operation can then start-up and continue basedon reliable weather forecast less than established operationlimit during this operational reference period for ceasing theoperation. Uncertainty in the weather forecast for this periodshall be considered.

Guidance note:For weather restricted operations reference is made to DNV-OS-H101. This standard is not yet issued, until issue refer to DNVRules for planning of marine operations, Pt. 1, Ch. 2, paragraph3.1 and DNV-RP-H102, Ch. 2.1, paragraph 2.2.


604 An operation can be defined as a temporary condition ifthe duration is less than 6 months unless defined as weatherrestricted conditions. The environmental load effect for tempo-rary conditions shall be taken as the 10-year return period forthe actual season.

Guidance note:Conditions exceeding 6 months but no longer than 12 monthsmay occasionally be defined as temporary conditions.


605 Conditions not defined as weather restricted conditionsor temporary conditions shall be defined as permanent condi-tions. The environmental load effect for permanent conditionsshall be taken as the 100-year return period.606 When considering the environmental design load the most

unfavourable relevant combination, position and direction ofsimultaneously acting environmental loads shall be used in doc-umenting the integrity of the submarine pipeline system. Functional loads (see B), interference loads (see E) and acci-dental loads (see F) shall be combined with the environmentalloads as appropriate, see G103.607 The characteristic environmental load effect for installa-tion, LE, is defined as the most probable largest load effect fora given seastate and appropriate current and wind conditionsgiven by:

where:F(LE) is the cumulative distribution function of LE, and N is thenumber of load effect cycles in a sea-state of a duration not lessthan 3 hours.608 The most critical load effect combination for the rele-vant return period shall be used. When the correlations amongthe different environmental load components (i.e. wind, wave,current or ice) are unknown the characteristic combined envi-ronmental loads in Table 4-2 may be used.

1) The 100-year return period implies an annual probability of exceedance of 10-2. 2) This is in conflict with ISO 13623 in case the design life is less than 33 years.

10 yr seasonal

End

T’POP=TWF+TSAFE

End

TR: Operation reference period

TR=Δstart+TPOP+TC

Establish OPLIM

Calculate start & interrupt Criterion Co(α(TPOP))

End

T ’C: Contingency time to cease operation

TPOP: Planned operation period

Weather window (TR)

T’R=TWF+TSafe+TC

TSafe: Time to safely cease the operation

Δstart: Start-up time

Weather Restricted Operations Non-Weather Restricted Operations

Environmental conditions

TR<72 hNo

TR’<72 hNo

TR<6m

Establish OPLIM

Calculate start & interrupt Criterion Co(α(T’POP))

Weather window (T’R)

Environmental loads based on Statistics

100 yr

No

End

TC: Contingency time TWF: Weather forecast intervals

10 yr seasonal

End

T’POP=TWF+TSAFE

End

TR: Operation reference period

TR=Δstart+TPOP+TC

Establish OPLIM

Calculate start & interrupt Criterion Co(α(TPOP))

End

T ’C: Contingency time to cease operation

TPOP: Planned operation period

Weather window (TR)

T’R=TWF+TSafe+TC

TSafe: Time to safely cease the operation

Δstart: Start-up time

Weather Restricted Operations Non-Weather Restricted Operations

Environmental conditions

TR<72 hNo

TR<72 hNo

TR’<72 hNo

TR’<72 hNo

TR<6m

Establish OPLIM

Calculate start & interrupt Criterion Co(α(T’POP))

Weather window (T’R)

Environmental loads based on Statistics

100 yr

No

End

TC: Contingency time TWF: Weather forecast intervals

(4.3)

Table 4-2 Combinations of characteristic environmental loads in terms of return period 1)2) Wind Waves Current Ice Earth quakePermanent condition100-year 100-year 10-year10-year 10-year 100-year10-year 10-year 10-year 100-year

100-yearTemporary condition10-year 10-year 1-year1-year 1-year 10-year1-year 1-year 1-year 10-year

10-year

F LE( ) 1 1N----–=

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D. Construction Loads

D 100 General101 Loads which arise as a result of the construction of thepipeline system, comprising installation, pressure testing,commissioning, maintenance and repair, shall be classifiedinto functional and environmental loads.102 All significant loads acting on pipe joints or pipe sec-tions during transport, fabrication, installation, maintenanceand repair activities shall be considered.103 Functional Loads shall consider forces generated due toimposed tension during pipeline installation, maintenance andrepair.104 Environmental loads shall consider forces induced onthe pipeline due to wind, waves and current, including deflec-tions and dynamic loads due to vessel movement.105 Accidental loads shall consider inertia forces due to sud-den water filling, excessive deformation in overbend and sag-bend, and forces due to operation errors or failures inequipment that could cause or aggravate critical conditions,see Sec.10 A300.106 Other loads to be considered are:

— stacking of pipes— handling of pipe and pipe sections, e.g. lifting of pipe, pipe

joints, pipe strings and pipe spools, and reeling of pipestrings

— pull-in at landfalls, tie-ins, trenching etc.— pressure testing— commissioning activities, e.g. increase in pressure differ-

ential due to vacuum drying.

107 Operating limit conditions shall be established relevantfor the construction activity under consideration, see C600 andSec.10 D400.108 Typical construction loads for pre-installed risers, risersupports/guides and J-tubes on jackets and similar installationsare:

— wind-induced forces, in particular wind-induced vortexshedding, on parts which are designed to be submergedafter installation of the load-bearing structure

— deflections/forces generated during load-out of the load-bearing structure

— transportation forces due to barge movements— launch forces due to deflection and hydrodynamic loads

(drag, slam and slap) on the structure— deflections/forces generated during installation of load-

bearing structure— inertia loads on the riser supports/guides due to pile driv-

ing— re-distribution of support forces when possible temporary

riser supports are removed and the riser turned into thefinal position

— cold springing of the risers (elastic pre-deformations)— tie-in forces generated when the riser is connected to the

tie-in spool/pipeline— dynamic loads from pre-commissioning activities, e.g.

flooding and de-watering with pigs.

109 The load combinations to be considered shall be selectedto reflect the most severe load combinations likely to beencountered during the construction phase under considera-tion.110 The most severe load effect may be taken as mean ±3standard deviations unless otherwise stated.

Guidance note:This will typically apply to when dimensional tolerances are added.


E. Interference LoadsE 100 General101 Loads which are imposed on the pipeline system from3rd party activities shall be classified as interference loads.These loads include but are not limited to trawl interference,anchoring, vessel impacts and dropped objects.102 The requirement for designing the submarine pipeline sys-tem for interference loads shall be determined based upon inter-ference frequency studies and assessment of the potentialdamage. If the annual probability of occurrence is less than 10-2the load shall be classified as accidental load, see F.103 For calculations of trawl interference loads, reference isgiven to DNV-RP-F111 Interference between Trawl Gear andPipelines.104 The trawling loads can be divided in accordance with thethree crossing phases:

1) Trawl impact, i.e. the initial impact from the trawl boardor beam which may cause local dents on the pipe or dam-age to the coating.

2) Over-trawling, often referred to as pull-over, i.e. the sec-ond phase caused by the wire and trawl board or beam slid-ing over the pipe. This will usually give a more globalresponse of the pipeline.

3) Hooking, i.e. the trawl board is stuck under the pipe and inextreme cases, forces as large as the breaking strength ofthe trawl wire are applied to the pipeline.

Hooking is normally categorised as an accidental load.105 The trawl impact energy shall be determined consider-ing, as a minimum:

— the trawl gear mass and velocity— the effective added mass and velocity.

The impact energy shall be used for testing of the pipelinecoatings and possible denting of the pipeline wall thickness. Incase piggy-back lines these shall also have adequate safetyagainst trawl impacts. Reference is given to DNV-RP-F111.106 Other 3rd party interference loads shall be calculatedusing recognised methods.

F. Accidental LoadsF 100 General101 Loads which are imposed on a pipeline system underabnormal and unplanned conditions and with an annual proba-bility of occurrence less than 10-2 shall be classified as acci-dental loads.102 Typical accidental loads can be caused by:

— extreme wave and current loads— vessel impact or other drifting items (collision, grounding,

sinking, iceberg)— dropped objects— seabed movement and/or mud slides— explosion— fire and heat flux— operational malfunction

DET NORSKE VERITAS


— dragging anchors.

103 Size and frequency of accidental loads, for a specificpipeline system, may be defined through risk analyses. Refer-ence is also made to DNV-RP-F107 Risk Assessment of Pipe-line Protection.

G. Design Load EffectsG 100 Design cases101 Each static limit state, see Sec.5 D, shall be checked forthe load effect induced by the most critical 100-year design

case of functional, environmental, interference and accidentalloads. The 100-year load effect is the load with an annual prob-ability of 10-2 of exceedance in a period of one year.102 The most critical combination is normally governed byextreme functional, environmental, interference or accidentalload effect. These have been denoted design cases. Unless spe-cial evaluation of critical 100-year design case is carried out,the design cases defined by combinations of characteristic loadeffects in Table 4-3 shall be used.103 In addition to the conditions defined above, fatigue limitstate and accidental condition shall also be checked. The char-acteristic load definitions for this combination are given inTable 4-3.

G 200 Load combinations201 The design load effect can generally be expressed in thefollowing format:

In specific forms, this corresponds to:

Guidance note:The load combinations to the left are referred to explicitly in thedesign criteria, e.g. Eq. (5.19).


202 The design load effect shall be calculated for eachdesign case, see G100 for all relevant load combinations, Table4-4. The different ULS design load effects are referred to in thedifferent local buckling limit states.

Guidance note:The partial safety factors in DNV-OS-F101 have been deter-mined by structural reliability methods to a pre-defined failureprobability. Structural reliability calculations differentiatebetween single joint failures (local checks) and series systemfailures (system effects). These two kinds of scenarios are expressed as two different loadcombinations in DNV-OS-F101:

a) shall only be considered for scenarios where system effectsare present

b) for local scenarios and shall always be considered.

When system effects are present, the pipeline will fail at its weak-est point. Hence, the likely load shall be combined with theextreme low resistance. Applied to pipelines system effect can beexpressed as the weakest link principle (where the chain getsweaker the longer the chain is). This is characterised by that thewhole pipeline is exposed to the same load over time. Applied to pipelines, system effects are present for:- pressure containment - collapse, in as installed configuration - installation.

Table 4-3 Combinations of characteristic loads effects for different design casesDesign case Load

combination5)Functional

loadEnvironmental

loadInterference

loadAccidental

loadFunctional design case a, b 100-year1) 1-year Associated NAEnvironmental design case a, b Associated2) 100-year3) Associated NAInterference design case b Associated2) Associated UB NAFatigue design4) case c Associated Associated Associated NAAccidental design case d Associated Associated Associated BECharacteristic load definitionn-year: Most probable maximum in n years, UB: Upper Bound, BE: Best estimate

1) This will normally be equivalent to an internal pressure equal to the local incidental pressure combined with expected associated values of other functional loads.

2) This will normally be equivalent to an internal pressure and temperature not less than the operating pressure and the temperature profiles.3) As defined in C607.4) The fatigue design load shall be cyclic functional loading (start-up and shut-down), random environmental load (e.g. wave and current spectra) and

repeated interference loading. The load combinations shall be associated.5) The referred combinations is given in Table 4-4.

(4.4)

(4.5)(4.6)(4.7)

cAAcFIEEcFFSd LLLLL γγγγγγγ ⋅⋅+⋅⋅+⋅+⋅⋅=

cAAcFIEEcFFSd MMMMM γγγγγγγ ⋅⋅+⋅⋅+⋅+⋅⋅=

cAAcFIEEcFFSd γγεγγεγεγγεε ⋅⋅+⋅⋅+⋅+⋅⋅=

cAAcFIEEcFFSd SSSSS γγγγγγγ ⋅⋅+⋅⋅+⋅+⋅⋅=

Table 4-4 Load effect factors and load combinationsLimit State / Load combination

Design load combination Functional loads 1) Environmental load Interference loads Accidental loadsγ F γ E γ F γ A

ULS a System check2) 1.2 0.7b Local check 1.1 1.3 1.1

FLS c 1.0 1.0 1.0ALS d 1.0 1.0 1.0 1.01) If the functional load effect reduces the combined load effects, γF shall be taken as 1/1.1.2) This load combination shall only be checked when system effects are present, i.e. when the major part of the pipeline is exposed to the same functional

load. This will typically only apply to pipeline installation.

DET NORSKE VERITAS


The first two are handled with explicitly by the use of thicknesst1. This is also why thickness t2 and not t1 is used for the burstcapacity in the local buckling for pressurised pipes, since it is alocal check.Regarding installation, an extreme environmental load is notlikely to occur when the weakest pipe section is at the mostexposed location indicating that system effects not are present.However, combined with a more representative environmentalload (in the extreme case, “flat sea”), the whole pipeline willundergo the same deformation “over time”, hence, having a sys-tem effect present. In Table 4-3, load combination a has a 10% increase in the func-tional load to cover the system effect combined with a 0.7 factoron the extreme environmental load giving a more “representa-tive” environmental load, applicable for the above.Another example of where system effects are present is for reel-ing where the whole pipe also will undergo the same deformation(neglecting the variation in drum diameter increase). For thisapplication, a condition factor of 0.82 also applies, giving thetotal load effect factor of 1.0.Hence, load combination b shall always be checked while loadcombination a normally is checked for installation only.


203 The condition load effect factor applies to the conditionsin Table 4-5. Condition load effect factors are in addition to theload effect factors and are referred to explicitly in Eq. (4.5, 4.6and 4.7).

Guidance note:An uneven seabed condition is relevant in connection with free-spanning pipelines. If uncertainties in soil conditions and possi-ble trawl interference are accounted for, a lower γc is allowed.Reference is given to DNV-RP-F110 Global Buckling of Subma-rine Pipelines – Structural Design due to High Temperature/HighPressure.Continuously stiff supported denotes conditions where the mainpart of the load is also displacement controlled. Examples may bereeling on the drum or J-tube pull-in.Several condition factors may be required simultaneously, e.g.for pressure testing of pipelines on uneven seabed, the resultingcondition factor will be 1.07 · 0.93 = 1.00.


G 300 Load effect calculations301 The design analyses shall be based on accepted princi-ples of statics, dynamics, strength of materials and soilmechanics.302 Simplified methods or analyses may be used to calculatethe load effects provided that they are conservative. Modeltests may be used in combination with, or instead of, theoreti-cal calculations. In cases where theoretical methods are inade-

quate, model or full-scale tests may be required.303 When determining responses to dynamic loads, thedynamic effect shall be taken into account if deemed signifi-cant.304 When non-linear material is required in the analyses thestress-strain curve shall based on specified minimum valuesaccounting for temperature derating (fy and fu) consideredbeing engineering stress values, except for when the mean orupper bound values are explicitly required by the procedure(e.g. for fracture mechanics applications). The use of true ver-sus engineering stress strain curve shall be consistent with theFE-program applied.

Guidance note:The strain at fu is normally considerably less than the fracturestrain and is normally in the order of 6-10%. This should bedetermined from tests of similar material.


305 Load effect calculation shall be performed applyingnominal cross section values unless otherwise required by thecode.306 The effective axial force that determines the globalresponse of a pipeline is denoted S. Counting tensile force aspositive:

307 Split up into functional, environmental and accidentaleffective force, the following applies:

SE = NESA = NA308 In the as-laid condition, when the pipe temperature andinternal pressure are the same as when the pipe was laid,

Where H is the effective (residual) lay tension. The effectiveresidual lay tension may be determined by comparing the as-laid survey data to results from FE analysis.309 Effective axial force of a totally restrained pipe in thelinear elastic stress range is:

where:

H = Effective (residual) lay tensionΔ pi = Internal pressure difference relative to as laidΔΤ = Temperature difference relative to as laid.

Table 4-5 Condition load effect factors, γ CCondition γc

Pipeline resting on uneven seabed 1.07

Continuously stiff supported 0.82System pressure test 0.93Otherwise 1.00

(4.8)

(4.9)

(4.10)

(4.11)

( ) ( )( )2222

4DptDpNApApNpS eieeiii ⋅−⋅−⋅⋅−=⋅+⋅−=

π

( ) ( )( )2222

4DptDpNApApNpS eiFeeiiFiF ⋅−⋅−⋅⋅−=⋅+⋅−=

π

HS =

( ) TEAApHS sii Δ⋅⋅⋅−⋅−⋅⋅Δ−= αν21

DET NORSKE VERITAS


SECTION 5DESIGN – LIMIT STATE CRITERIA

A. GeneralA 100 Objective101 This section provides design and acceptance criteria forthe possible modes of structural failure in pipeline systems.

A 200 Application201 This standard includes no limitations on water depth.However, when this standard is applied in deep water whereexperience is limited, special consideration shall be given to:

— other failure mechanisms than those given in this section— validity of parameter range (environmental/design/opera-

tional parameters)— dynamic effects.

202 This standard does not specify any explicit limitationswith respect to elastic displacements or vibrations, providedthat the effects of large displacements and dynamic behaviour,including fatigue effect of vibrations, operational constraintsand ratcheting, are taken into account in the strength analyses.203 The local buckling criteria, see D300-D600, are onlyapplicable to pipelines that are straight in stress-free conditionand are not applicable to e.g. bends. 204 For parts of the submarine pipeline system which extendonshore complementary requirements are given inAppendix F.205 For spiral welded pipes, the following additional limita-tions apply:

— when supplementary requirement F (fracture arrest prop-erties) is specified, see Sec.7, the possibility for a runningfracture to continue from a weld in one pipe joint to theweld of the next pipe joint shall be assessed

— external pressure resistance should be documented— the design shall be based on the load controlled condition,

see D600, unless the feasibility for use of displacementcontrolled condition can be documented.

Guidance note:The limitations to fracture arrest and load controlled conditionare due to limited experience with spiral welded pipes subjectedto running fracture or large strains.


B. System Design PrinciplesB 100 Submarine pipeline system layout101 System lay out, including need for different valves etc.,shall be designed such that the requirements imposed by thesystematic review of the process control are met, see Sec.2 B.102 The submarine pipeline system should not be routedclose to other structures, other pipeline systems, wrecks, boul-ders, etc. The minimum distance should be determined basedupon anticipated deflections, hydrodynamic effects, and uponrisk-based evaluations. The detailed routing shall take the min-imum established distance into account.103 Pipelines, risers and J-tubes should be routed inside thestructure to avoid vessel impact, and shall be protected againstimpact loads from vessels and other mechanical interaction.Risers and J-tubes should not be located inside the loadingzones of platforms.

104 The routing of risers and J-tubes shall be based on thefollowing considerations:

— platform configuration and topsides layout— space requirements— movements of the Riser or J-tube— cable/pipeline approach— Riser or J-tube protection— in-service inspection and maintenance— installation considerations.

105 Crossing pipelines should be kept separated by a mini-mum vertical distance of 0.3 m.106 The submarine pipeline system shall be protectedagainst unacceptable damage caused by e.g. dropped objects,fishing gear, ships, anchoring etc. Protection may be achievedby one or a combination of the following means:

— concrete coating— burial— cover (e.g. sand, gravel, mattress)— other mechanical protection.

107 Relative settlement between the protective structure andthe submarine pipeline system shall be properly assessed in thedesign of protective structures, and shall cover the full designlife of the submarine pipeline system. Adequate clearancebetween the pipeline components and the members of the pro-tective structure shall be provided to avoid fouling.108 Structural items should not be welded directly to pres-sure containing parts or linepipe due to the increased localstress on the linepipe. External supports, attachments etc. shallbe welded to a doubler plate or ring. The doubler plate or ringshall be designed with sufficient thickness to avoid stresses onthe linepipe. In case structural items are integrated in the pipe-line, e.g. pipe in pipe bulkheads, and are welded directly to thelinepipe, detailed stress analyses are required in order to docu-ment sufficiently low stress to ensure resistance againstfatigue, fracture and yielding.109 Permanent doubler rings and plates shall be made ofmaterials satisfying the requirements for pressure containingparts. Doubler plates shall be circular. For gas service and liq-uid service above 137 bar, doubler rings shall be used. Forduplex stainless steels and 13Cr martensitic stainless steels noattachments are permitted unless a stress analysis is performedin each case to determine that local stresses will not exceed0.8 fy.110 Doubler rings shall be made as fully encircling sleeveswith the longitudinal welds made with backing strips, andavoiding penetration into the main pipe material. Other weldsshall be continuous, and made in a manner minimising the riskof root cracking and lamellar tearing. The toe of welds attach-ing anode pads, doubler plates and branch welding fittings,when permitted, shall have a toe-to-toe distance from otherwelds of minimum 4 · t or 100 mm, whichever is larger. 111 Girth welds shall not be inaccessible under doublerrings, clamps, or other parts of supports.112 Riser and J-tube supports shall be designed to ensure asmooth transition of forces between riser/J-tube and support.113 For requirements to transitions, see F110 through F113.114 Pipelines in C-Mn steel for potentially corrosive fluidsof categories B, D and E (see Sec.2 C) should be designed forinspection pigging. In cases where the pipeline design does notallow inspection pigging, an analysis shall be carried out in

DET NORSKE VERITAS


accordance with recognised procedures to document that therisk of failure (i.e. the probability of failure multiplied by theconsequences of failure) leading to a leak is acceptable. Forcorrosive fluids of other categories the benefit of inspectionpigging on operational reliability shall be evaluated.115 For piggable components the internal diameter of thecomponent shall meet the requirements imposed by the pig-train.

Guidance note:It is recommended that bends radius are designed with a radiusnot less than 5 x nominal internal pipe diameter.


B 200 Mill pressure test and system pressure test201 The purposes of the mill test are:

— to constitute a pressure containment proof test— to ensure that all pipe sections have a minimum yield

stress.

Therefore, the mill test pressure is defined in terms of stressutilisation, see Sec.7 E100, rather than in terms of design pres-sure.

Guidance note:“in terms of stress utilisation” implies that the same structuralutilisation will be achieved independent on temperature de-ratingor corrosion allowance used in the design.


202 The purpose of the system pressure test is to prove thepressure containment integrity of the submarine pipeline sys-tem, i.e. it constitutes a leakage test after completed construc-tion disclosing gross errors.203 The pipeline system shall be system pressure tested afterinstallation in accordance with Sec.10 O500 unless this iswaived by agreement in accordance with 204 below. The localtest pressure (plt) during the system pressure test shall fulfil thefollowing requirement:

— Medium and High Safety Class during normal operation:

— Low Safety Class during normal operation:

Guidance note:With an incidental pressure of 10% above design pressure, theabove gives a system test pressure of approximately 1.15 timesthe local design pressure at the highest point of the pipeline sys-tem part tested, see Figure 1.

Figure 1 Illustration of local pressures and requirements to systempressure test


204 Alternative means to prove the same level of safety aswith the system pressure test is allowed by agreement giventhat the mill pressure test requirement of Sec.7 E100 has beenmet and not waived in accordance with Sec.7 E107.The industries knowledge and track record to date implies thelimitations in Table 5-1 for waiving the system pressure test.

plt ≥ 1.05 · pli (5.1)

plt ≥ 1.03 · pli (5.2)

ρtest⋅g1

ρtest⋅g1

Water depth

Inte

rnal

pre

ssur

e

Water depth

Inte

rnal

pre

ssur

e

Local design

pressure

Local incidental

pressure, pli

System test requirement5% above pli

Resulting test pressure

Filled with operating content

Filled with water

ρcont⋅g 1ρcont⋅g 1

Table 5-1 Requirements to waive system pressure testRequirementOther aspects with respect to system pressure test than pressure con-tainment integrity such as cleaning, contractual, shall be agreed.An inspection and test regime for the entire submarine pipeline system shall be established and demonstrated to provide the same level of safety as the system pressure test with respect to detectable defect sizes etc.; Records shall show that the specified requirements have consistently been obtained during manufacture, fabrication and instal-lation.

Guidance note:The requirement implies that a reporting limit lower than theacceptance criteria shall be used. This enables tracking of tenden-cies such that it can be documented that the criteria has been con-sistently met. It will also indicate systematic errors


Less than 75% of the pressure containment design resistance shall be utilised

Guidance note:The requirement implies that external pressure governs the wallthickness design. The advantage of the system pressure test isnormally limited for deep water pipelines, hence, the criteria. Thelimitation implies that the wall thickness shall be at least 33%larger than required by the pressure containment criterion.


The linepipe shall be seamless or produced by the SAW method. Repairs by other methods are allowed by agreement.

Guidance note:Other welding methods have to date not proved similar degree ofquality as SAW. SAW is not required for the girth welds


DET NORSKE VERITAS


205 During system pressure test, all limit states for safetyclass low shall be satisfied (see D).

B 300 Operating requirements301 Operating requirements affecting safety and reliabilityof the pipeline system shall be identified during the designphase, and shall be documented in the DFI Resumé andreflected in the PIM system.

C. Design Format

C 100 General101 The design format in this standard is based on a Loadand Resistance Factor Design (LRFD) format.102 The fundamental principle of the LRFD format is to ver-ify that design load effects, LSd, do not exceed design resist-ances, RRd, for any of the considered failure modes in anyscenario:

Where the fractions i denotes the different loading types thatenters the design criterion103 A design load effect is obtained by combining the char-acteristic load effects from the different load categories by cer-tain load effect factors, see Sec.4 G.104 A design resistance is obtained by dividing the charac-teristic resistance by resistance factors that depends on thesafety class, reflecting the consequences of failures, see 200.

C 200 Design resistance201 The design resistance, RRd, can normally be expressed in

the following format:

where

Rc is the characteristic resistancefc is the characteristic material strength,

see Eq. 5.5 and Eq.5.6tc is the characteristic thickness, see Table 5-2 and

Table 5-3γm, γSC are the partial resistance factors, see Table 5-4

and 5-5202 Two different characterisations of the wall thickness areused; t1 and t2 and are referred to explicitly in the design crite-ria. Thickness t1 is used where failure is likely to occur in con-nection with a low capacity (i.e. system effects are present)while thickness t2 is used where failure is likely to occur inconnection with an extreme load effect at a location with aver-age thickness. These are defined in Table 5-2.

1) Is intended when there is negligible corrosion (mill pressure test, con-struction (installation) and system pressure test condition). If corrosionexist, this shall be subtracted similar to as for operation.

2) Is intended when there is corrosion

Guidance note:If relevant, the erosion allowance shall be compensated for in thesimilar way as the corrosion allowance.


203 Minimum wall thickness independent on limit staterequirements are given in Table 5-3.

All components and risers shall be hydrostatically pressure tested dur-ing manufacture.

Guidance note:Components include flanges, valves, fittings, mechanical con-nectors, induction bends, couplings and repair clamps, pig trapsetc.


Automated Ultrasonic Testing (AUT) shall be performed after instal-lation welding. Alternative NDT methods proven to give the same detectability and sizing accuracy may be allowed by agreement.

Guidance note:AUT is normally required in order to ensure that no criticaldefects exist. The acceptance criterion is often based on an ECAlinking the fracture toughness, defects and loads. A reportinglimit less than this acceptance criteria is required in order toensure that there is no systematic error on the welding and toprove that the criteria are systematically met.


The pipeline shall not be exposed to accumulated nominal plastic strains exceeding 2% after AUT.Installation and intervention work shall be unlikely to have caused damage to the submarine pipeline system.

Guidance note:Special attention shall here be given to ploughing, other trenchingmethods or third party damages e.g. anchor chains of wires.


Table 5-1 Requirements to waive system pressure test (Continued)Requirement

(5.3)1≤⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎟⎠

⎞⎜⎜⎝

⎛

iRd

Sd

RLf

(5.4)

Table 5-2 Characteristic wall thicknessPrior to operation1) Operation2)

t1 t-tfab t-tfab-tcorr

t2 t t-tcorr

( )SCm

cccRd

tfRRγγ ⋅

=,

DET NORSKE VERITAS


The minimum wall thickness requirement is based on failure statistics, whichclearly indicate that impact loads and corrosion are the most likely causes offailure and have the decisive effect on thickness design (not D/t).

204 Wall thickness for stability calculations is given inE404.205 The material resistance factor, γm, is dependent on thelimit state category and is defined in Table 5-4.

1) The limit states (SLS, ULS, ALS and FLS) are defined in D.

206 Based on potential failure consequences the pipelineshall be classified into a safety class see Sec.2 C400. This willbe reflected in the safety level by the Safety Class resistancefactor γSC given in Table 5-5.The safety class may vary for different phases and differentlocations.

1) For parts of pipelines in location class 1, resistance safety class mediummay be applied (1.138).

2) The number of significant digits is given in order to comply with the ISOusage factors.

3) Safety class low will be governed by the system pressure test which isrequired to be 3% above the incidental pressure. Hence, for operation insafety class low, the resistance factor will effectively be 3% higher.

4) For system pressure test, U shall be equal to 1.00, which gives an allow-able hoop stress of 96% of SMYS both for materials fulfilling supple-mentary requirement U and those not.

207 Possible beneficial strengthening effect of weight coat-ing on a steel pipe shall not be taken into account in the char-acteristic resistance, unless the strengthening effect isdocumented. Coating which adds significant bending stiffnessto the pipe may increase the stresses/strains in the pipe at anydiscontinuity in the coating (e.g. at field joints). When appro-priate, this effect shall be taken into account.208 Possible beneficial strengthening effect of cladding or

liner on a steel pipe shall not be taken into account in the char-acteristic resistance, unless the strengthening effect is docu-mented.

C 300 Characteristic material properties301 Characteristic material properties shall be used in theresistance calculations. The yield stress and tensile strength inthe limit state formulations shall be based on the engineeringstress-strain curve.302 The characteristic material strength fy and fu, values tobe used in the limit state criteria are:

Where:fy,temp and fu,temp are the de-rating values due to the tempera-

ture of the yield stress and the tensilestrength respectively, see 304.

αU is the material strength factor, see Table 5-6.303 The different mechanical properties refer to room tem-perature unless otherwise stated. 304 The material properties shall be selected with due regardto material type and potential temperature and/or ageingeffects and shall include:

— yield stress— tensile strength— Young's modulus— temperature expansion coefficient.

For C-Mn steel this shall be considered for temperatures above50°C, and for 22Cr and 25Cr for temperatures above 20°C.

Guidance note:Field joint coating application during installation may alsoimpose temperatures in excess of the above and shall be consid-ered.


Guidance note:If no other information of de-rating effects on the yield stressexist the recommendations for C-Mn steel and Duplex steels Fig-ure 2 below may be used. For 13Cr testing is normally required.


Table 5-3 Minimum wall thickness requirementsNominal diameter Safety Class Location class Minimum thickness≥ 219 mm (8”) High 2 12 mm unless equivalent protection against accidental loads, other external loads

and excessive corrosion is provided by other meansLow and Medium

All -

< 219 mm (8”) High 2 Special evaluation of accidental loads or other external loads and excessive corro-sion shall be included in the determination of minimum required wall thickness for pipelines with

Low and Medium

All -

Table 5-4 Material resistance factor, γmLimit state category1) SLS/ULS/ALS FLSγ m 1.15 1.00

Table 5-5 Safety class resistance factors, γ SCγ SC

Safety class Low Medium HighPressure containment 2) 1.046 3),4) 1.138 1.308 1)

Other 1.04 1.14 1.26

(5.5)

(5.6)( ) Utempyy fSMYSf α⋅−= ,

( ) Utempuu fSMTSf α⋅−= ,

DET NORSKE VERITAS


Figure 2 Proposed de-rating values for yield stress of C-Mn and duplex stainless steels (DSS).

Guidance note:If no other information on de-rating effect of the ultimate stressexists, the de-rating of the yield stress can be conservativelyapplied.


305 Any difference in the de-rating effect of temperature fortension and compression shall be accounted for.

Guidance note:Difference in de-rating effect for tension and compression hasbeen experienced on 13Cr steel material.


306 The material factor, αU, depend on Supplementaryrequirement U as shown in Table 5-6.

Note: For system pressure test, αU shall be equal to 1.00, which gives anallowable hoop stress of 96% of SMYS both for materials fulfilling supple-mentary requirement U and those not. This is equivalent to the mill test utili-sation.

Guidance note:The application of Supplementary requirement U requires docu-mentation after the manufacture and shall be used with care.Based on production data, it may be used for future upgrade ofthe pipeline


307 For manufacturing processes which introduce colddeformations giving different strength in tension and compres-sion, a fabrication factor, αfab, shall be determined. If no otherinformation exists, maximum fabrication factors for pipesmanufactured by the UOE or UO processes are given inTable 5-7. The fabrication factor may be improved through heat treatmentor external cold sizing (compression), if documented.

308 For material susceptible to HISC, see Sec.6 D500.

C 400 Stress and strain calculations401 Stress Concentration Factors (SCF) shall be included ifrelevant.

Guidance note:Distinction should be made between global and local stress con-centrations. Local stress concentrations (that may be caused by weldedattachments, the weld itself, or very local discontinuities) willaffect the pipe only locally and are typically accounted for infatigue and fracture evaluations. Global stress concentrations(such as stress amplifications in field joints due to concrete coat-ing, which typically extend one diameter) will affect the pipe glo-bally, and shall be accounted for in the bending bucklingevaluations as well as fatigue and fracture evaluations.


402 Strain Concentration Factors (SNCF) shall be deter-mined and accounted for if plastic strain is experienced. TheSNCF shall be adjusted for the non-linear stress-strain rela-tionship for the relevant load level.Different approaches for calculation of the SNCF for fractureassessment are specified in Appendix A.403 Strain concentrations shall be accounted for when con-sidering:

— uneven deformation caused by variations in actual mate-rial yield stress and strain hardenability between pipejoints and in the weld metal due to scatter in material prop-erties

— variations in cross sectional area (actual diameter or wallthickness) between pipe joints

— stiffening effects of coating and variations in coatingthickness

— reduction of yield stress in field joints due to high temper-ature imposed by field joint coating application duringinstallation

— undermatch/overmatch of actual weld metal yield stress,relative to actual pipe material yield stress.

404 Nominal plastic strain increment shall be calculatedfrom the point where the material stress-strain curve deviatesfrom a linear relationship, see Figure 3.

Figure 3 Reference for plastic strain calculation

Guidance note:The yield stress is defined as the stress at which the total strain is0.5%. As an example for a 415 grade C-Mn steel, a unidirectionalstrain of 0.5% corresponds to an elastic strain of approximately0.2% and a plastic strain of 0.3%.


Table 5-6 Material Strength factor, αUFactor Normally Supplementary requirement αUαU 0.96 1.00

Table 5-7 Maximum fabrication factor, α fabPipe Seamless UO & TRB &

ERWUOE

α fab 1.00 0.93 0.85

C-Mn

Stress

Strain

Total Strain

SMYS

0.5%

Plastic Strain

DET NORSKE VERITAS


D. Limit StatesD 100 General101 All relevant limit states (failure modes) shall be consid-ered in design for all relevant phases and conditions listed inSec.4.

Guidance note:As a minimum requirement, the submarine pipeline system shallbe designed against the following potential modes of failure:

Serviceability Limit State- ovalisation/ ratcheting limit state- accumulated plastic strain and strain ageing- large displacements- damage due to, or loss of, weight coating.

Ultimate Limit State- bursting limit state- ovalisation/ratcheting limit state (if causing total failure)- local buckling limit state (pipe wall buckling limit state)- global buckling limit state (normally for load-controlled

condition)- fatigue- unstable fracture and plastic collapse limit state- impact.


102 In case no specific design criterion is given for a specificlimit state this shall be developed in compliance with the safetyphilosophy in Sec.2.

D 200 Pressure containment (bursting)201 The following criteria are valid provided that the millpressure test requirement in Sec.7 E100 has been met. If not, acorresponding decreased utilisation shall be applied.202 The pressure containment shall fulfil the following cri-teria:

Whereplx = pli during operation, (see Sec.3 B300 and 4 B200) andplx = plt during system test.203 The pressure containment resistance pb(t) is given by:

where

Guidance note:In the above formulae, t shall be replaced by t1 when used in Eq5.7 and t2 when used in Eq. 5.19.


204 Reduction in pressure containment resistance due to truecompressive forces (load controlled), N, shall be considered.Reference is made to DNV-RP-F101 Corroded Pipelines.

D 300 Local buckling - General301 Local buckling (pipe wall buckling) implies gross defor-mation of the cross section. The following criteria shall be ful-filled:

— system collapse (external pressure only)— propagation buckling— combined loading criteria, i.e. interaction between exter-

nal or internal pressure, axial force and bending moment.

These will be given in the following sub-sections.302 Large accumulated plastic strain may aggravate localbuckling and shall be considered.

D 400 Local Buckling – External over pressure only (System collapse)401 The characteristic resistance for external pressure (pc)(collapse) shall be calculated as:

where:

αfab is the fabrication factor, see Table 5-7Guidance note:In the above formulas, t shall be replaced by t1 or t2 as given inthe design criteria.


Guidance note:Ovalisation caused during the construction phase shall beincluded in the total ovality to be used in design. Ovalisation dueto external water pressure or bending moment shall not beincluded.


402 The external pressure at any point along the pipelineshall meet the following criterion (system collapse check):

where

pmin is the minimum internal pressure that can be sustained.This is normally taken as zero for as-laid pipeline.

Guidance note:The system collapse will occur at the weakest point in the pipe-line. This will normally be represented by fy and the minimumwall thickness, t1. A seamless produced linepipe’s weakest section may not be wellrepresented by the minimum wall thickness since it is not likely tobe present around the whole circumference. A larger thickness,between t1 and t2, may be used for such pipes if this can be docu-mented representing the lowest collapse capacity of the pipeline.


(5.7)

(5.8)

(5.9)

( )SCm

belx

tppp

γγ ⋅≤− 1

( )3

22⋅⋅

−⋅

= cbb ftD

ttp

⎥⎦

⎤⎢⎣

⎡=15.1

; uycb

ffMinf

(5.10)

(5.11)

(5.12)

(5.13)

(5.14)

( ) ( )( ) ( ) ( )( ) ( ) ( ) ( )tDftptptptptptptp pelcpcelc ⋅⋅⋅⋅=−⋅− 0

22

( ) 2

3

1

2

ν−

⎟⎠⎞

⎜⎝⎛⋅⋅

= DtE

tpel

( )D

tftp fabyp⋅

⋅⋅=2α

foDmax Dmin–

D--------------------------------

not to be taken < 0.005 (0.5%)

=

( )SCm

ce

tppp

γγ ⋅≤− 1

min

DET NORSKE VERITAS


D 500 Propagation buckling 501 Propagation buckling cannot be initiated unless localbuckling has occurred. In case the external pressure exceedsthe criteria given below, buckle arrestors should be installedand spacing determined based on cost and spare pipe philoso-phy. The propagating buckle criterion reads:

where

αfab is the fabrication factor, see Table 5-7Guidance note:Collapse pressure, pc, is the pressure required to buckle a pipeline.Initiation pressure, pinit, is the pressure required to start a propa-gating buckle from a given buckle. This pressure will depend onthe size of the initial buckle.Propagating pressure, ppr, is the pressure required to continue apropagating buckle. A propagating buckle will stop when thepressure is less than the propagating pressure.The relationship between the different pressures are:pc > pinit > ppr


Guidance note:The safety class and amount of metal loss due to corrosion shallbe determined based on the probability and possibility of experi-encing a high external over pressure during operation. For liquidpipelines, safety class low and non-corroded cross section is nor-mally used while other properties may be used for gas pipelinessince they may experience a nearly zero internal pressure in theoperational phase. Note that the possibility of a propagating buckle shall not becombined with the likelihood of getting an initiating event in theshut-down time span, since a dent caused during the pressurisedcondition, may start propagating as the internal pressure is lost.


502 A buckle arrestor capacity depends on

— propagating buckle resistance of adjacent pipe— propagating buckle resistance of an infinite buckle arrestor— length of arrestor.

An integral buckle arrestor may be designed by:

where the crossover pressure px is

ppr,BA is the propagating buckle capacity of an infinite arres-tor. This is calculated by Eq. 5.16 with the buckle arre-stor properties

LBA buckle arrestor lengthGuidance note:The propagating buckle criterion, Eq. 5.15, corresponds to anominal failure probability that is one order of magnitude higherthan the target nominal failure probability. This is because it isdependent on an initiating even. However, for a buckle arrestor,

it is recommended to have a larger confidence and a safety classhigher than for the propagating pressure is recommended.


D 600 Local Buckling - Combined Loading Criteria601 Differentiation is made between:

— Load Controlled condition (LC condition)— Displacement Controlled condition (DC condition).

Different design checks apply to these two conditions.602 A load-controlled condition is one in which the struc-tural response is primarily governed by the imposed loads.603 A displacement-controlled condition is one in which thestructural response is primarily governed by imposed geomet-ric displacements.604 A load controlled design criterion can always be appliedin place of a displacement controlled design criterion.

Guidance note:An example of a purely displacement-controlled condition is apipeline bent into conformity with a continuous curved structure,such as a J-tube or on a reel. In that case, the curvature of the pipeaxis is imposed but the circumferential bending that leads toovalisation is determined by the interaction between the curva-ture of the axis and the internal forces induced by the curvature.A less clear-cut example is a pipeline in contact with the rollersof a lay barge stinger. On a large scale, the configuration of thepipeline has to conform to the rollers, and in that sense is dis-placement controlled. On a local scale however, bending of thepipe between the rollers is determined by the interaction betweenweight and tension and is load-controlled. The stinger tip will,however, always be load controlled.Another intermediate case is an expansion spool in contact withthe seabed. Pipeline expansion induced by temperature and pres-sure imposes a displacement at the end of the spool. The struc-tural response of the spool itself has little effect on the imposedexpansion displacement, and the response is primarily displace-ment-controlled. However, the lateral resistance to movement ofthe spool across the seabed also plays a significant part andinduces a degree of load control.The answer to the question on if a condition is load controlled ordisplacement controlled is impossible since the questions inwrong, the question should be; how can one take partial benefitof that a condition is partially displacement controlled element?On a general basis this needs sensitivity analyses. A load control-led criterion can, however, always be applied


Load controlled condition605 Pipe members subjected to bending moment, effectiveaxial force and internal overpressure shall be designed to sat-isfy the following condition at all cross sections:

where

MSd is the design moment, see Eq. 4.5SSd is the design effective axial force, see Eq. 4.7pi is the internal pressure, see Table 4-3pe is the external pressure, see Sec.4 B300

(5.15)

D/t < 45 (5.16)

(5.17)

(5.18)

SCm

pre

pp

γγ ⋅<

5.2235 ⎟

⎠

⎞⎜⎝

⎛⋅⋅=Dtfp fabypr α

SCm

Xe

ppγγ ⋅⋅

≤1.1

( ) ⎥⎦

⎤⎢⎣

⎡⎟⎠

⎞⎜⎝

⎛ ⋅−−⋅−+= 2

2, 201

DLtEXPpppp BA

prBAprprX(5.19a)

(5.19b)

( )( )

( ) ( )1

32

2

2

22

22

≤

⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜

⎝

⎛

⋅⋅

−⋅+

⎪⎭

⎪⎬⎫

⎪⎩

⎪⎨⎧

⎪⎭

⎪⎬⎫

⎪⎩

⎪⎨⎧

⋅⋅⋅

+⋅

⋅⋅tp

pptS

pStM

M

bc

eip

pc

iSdSCm

pc

SdSCm

αα

αγγ

αγγ

( ) ( ) ( ) 1,''2

2

22

22 ≤⎟⎟⎠

⎞⎜⎜⎝

⎛⋅+

⎪⎭

⎪⎬⎫

⎪⎩

⎪⎨⎧

⎭⎬⎫

⎩⎨⎧ ⋅⋅

+⋅⋅c

hp

c

iSdSCm

c

SdSCm

tqtpStMα

αα

γγα

γγ

DET NORSKE VERITAS


pb is the burst pressure, Eq. 5.8Sp and Mpdenote the plastic capacities for a pipe defined by:

MSd’ = MSd/Mp (normalised moment)Sd’ = Sd/Sp(normalised effective force)

αc is a flow stress parameter and αp account for effect of D/t ratio.Guidance note:The left hand side of the combined loading criterion is referred toas interaction ratio in order not to mix it with “unity check”. In aunity check, the loads are normally directly proportional to theutilisation while the axial load and internal pressure are squaredin this criterion.


Guidance note:In order to improve the engineering understanding, it is recom-mended to use normalised moment, force and pressure as givenin the b equations.


606 If the pipeline in addition to the axial load, pressure andmoment also has a lateral point load, this should be includedby a modification of the plastic moment capacity as follows:

where

αpm = Plastic moment reduction factor accounting for point load

R = Reaction force from point load

607 Pipe members subjected to bending moment, effectiveaxial force and external overpressure shall be designed to satisfy

the following equation:

wherepmin is the minimum internal pressure that can be sustained.

This is normally taken as zero for installation except forcases where the pipeline is installed water filled.

pc is the characteristic collapse pressure, Eq. 5.10. Thisshall be based on thickness t2.

Guidance note:The left hand side of the combined loading criterion is referred toas interaction ratio in order not to mix it with “unity check”. In aunity check, the loads are normally directly proportional to the uti-lisation while the load components are squared in this criterion.


Displacement controlled condition608 Pipe members subjected to longitudinal compressivestrain (bending moment and axial force) and internal over pres-sure shall be designed to satisfy the following condition at allcross sections:

where:εSd = Design compressive strain, Eq. (4.6)

pmin = Minimum internal pressure that can be continuouslysustained with the associated strain

γε = Strain resistance factor, Table 5-8

αh = , Table 7.5 and Table 7.11

αgw = See Sec.13 E1000.

609 Pipe members subjected to longitudinal compressivestrain (bending moment and axial force) and external overpressure shall be designed to satisfy the following condition atall cross sections:

(5.20)

(5.21)

(5.22)

(5.23)

(5.24)

(5.25)

(5.26)

(5.27)

( ) ( ) ttDftS yp ⋅−⋅⋅= π

( ) ( ) ttDftM yp ⋅−⋅= 2

32

⋅==

b

i

y

yh

p

pf

qσ (normalised pressure)

( )y

uc f

f⋅+−= ββα 1

⎪⎪⎩

⎪⎪⎨

⎧

≥⎟⎟⎠

⎞⎜⎜⎝

⎛−−

<−

=7.0131

7.01

b

i

b

i

b

i

p

pp

pp

pp

β

βα

⎪⎪⎩

⎪⎪⎨

⎧

>

<<⎟⎠⎞

⎜⎝⎛ −

<

=

60/0

60/1590

/6015/5.0

2

22

2

tDfor

tDfortDtDfor

β

pmpp MM α⋅=loadpoint,

ypm R

RtD130

/1 2−=α

229.3 tfR yy ⋅⋅=

(5.28a)

(5.28b)

(5.29)

(5.30)

(5.31)

( ) ( ) ( ) 12

2

min

22

22

≤⎟⎟⎠

⎞⎜⎜⎝

⎛ −⋅⋅+

⎪⎭

⎪⎬⎫

⎪⎩

⎪⎨⎧

⎪⎭

⎪⎬⎫

⎪⎩

⎪⎨⎧

⋅⋅⋅

+⋅

⋅⋅tppp

tSS

tMM

c

eSCm

pc

SdSCm

pc

SdSCm γγ

αγγ

αγγ

( ) ( )( ) 1''

2

2

min

22

22 ≤⎟⎟⎠

⎞⎜⎜⎝

⎛ −⋅⋅+

⎪⎭

⎪⎬⎫

⎪⎩

⎪⎨⎧

⎭⎬⎫

⎩⎨⎧ ⋅⋅

+⋅⋅tppptStM

c

eSCm

c

SdSCm

c

SdSCm γγ

αγγ

αγγ

D t 45 pi pe<,≤⁄

D/t ≤ 45, pi ≥ pe( )

εγεεε ec

RdSdppt −

=≤ min2 ,

( )gwh

b

eec

tp

ppDtppt ααε ⋅⋅

⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜

⎝

⎛

⋅

−⋅+⋅⎟

⎠⎞

⎜⎝⎛ −⋅=− − 5.1min

min

32

5101.078.0),(

max

5,0⎟⎟⎠

⎞⎜⎜⎝

⎛

m

t

RR

D/t < 45, pmin < pe1)()0,( 2

min

8.0

2≤

⋅

−+

⎟⎟⎟⎟

⎠

⎞

⎜⎜⎜⎜

⎝

⎛

SCm

c

e

c

Sd

tppp

tγγγ

εε

ε

DET NORSKE VERITAS


Guidance note:For D/t < 23, the utilisation may be increased provided that fullscale testing, observation, or former experience indicate suffi-cient safety margin in compliance with this standard. Anyincreased utilisation shall be supported by analytical designmethods.


Guidance note:System effects are normally not present for local buckling con-siderations and, hence, t2 should be used. However, for reeling, alarge portion of the pipeline will be exposed to similar curvatureand load combination “a” shall be used combined with the con-dition factor of 0.82, yielding unity, and the nominal thicknesscan be used also for this criteria. The thickness and yield stressvariation along the pipe, in particular between two pipe jointsshould be evaluated in addition to this system effect.

610 A higher probability of failure corresponding to a serv-iceability limit state may be allowed during the installationphase provided that:

— aids to detect buckle are provided— repair of potential damage is feasible and may be per-

formed during laying— buckle arrestors are installed if the external pressure

exceeds the initiation propagating pressure.

Relevant resistance factors may then be calibrated according tothe SLS requirements in Sec.2.

D 700 Global buckling 701 Global buckling implies buckling of the pipe as a bar incompression. The pipeline may buckle globally, either down-wards (in a free span), laterally ("snaking" on the seabed), orvertically (as upheaval buckling of a buried pipeline or on afree-span shoulder of an exposed pipeline).702 The effect of internal and external pressures should betaken into account using the concept of an effective axial force,see Sec.4 G300. The procedure is as for "ordinary" compres-sion members in air.703 A negative effective axial force may cause a pipeline ora riser to buckle as a bar in compression. Distinction shall bemade between load-controlled and displacement-controlledbuckling.704 The following global buckling initiators shall be consid-ered:

— trawl board impact, pullover and hooking— out of straightness.

705 Load-controlled global buckling may be designed inaccordance with DNV-OS-C101 Design of Offshore SteelStructures, General (LRFD). 706 Displacement-controlled global buckling may beallowed. This implies that global buckling may be allowedprovided that:

— pipeline integrity is maintained in post-buckling configu-rations (e.g. local buckling, fracture, fatigue etc.)

— displacement of the pipeline is acceptable.

707 For design of the following high pressure/high tempera-ture pipelines:

— exposed on even seabed

— exposed on un-even seabed— buried pipelines— reference is made to DNV-RP-F110 Global Buckling of

Submarine Pipelines – Structural Design due to HighTemperature/High Pressure.

708 It is not sufficient to design HP/HT pipelines for globalbuckling based on "worst case condition" axial and lateral soilresistance combined with displacement controlled local buck-ling criteria only. These upper and lower bound soil resistancevalues will typically have a probability of exceedance in theorder of a couple of per cent and will not alone prove a suffi-cient nominal failure probability. A more total evaluation ofthe failure probability is, hence, required.

D 800 Fatigue801 Reference is made to the following codes:

DNV-RP-C203 Fatigue Strength Analysis of Offshore SteelStructures

DNV-RP-C205 Environmental Conditions and Environmen-tal Loads

DNV-RP-F105 Free Spanning PipelinesDNV-RP-F204 Riser Fatigue.802 The pipeline systems shall have adequate safety againstfatigue failures within the design life of the system.803 All stress fluctuations imposed on the pipeline systemduring the entire design life, including the construction phase,which have magnitude and corresponding number of cycleslarge enough to cause fatigue effects shall be taken intoaccount when determining the long-term distribution of stressranges. The fatigue check shall include both low-cycle fatigueand high-cycle fatigue. The requirements regarding accumu-lated plastic strain (D1000 below) shall also be satisfied.

Guidance note:Typical causes of stress fluctuations in a pipeline system are:- direct wave action- vibrations of the pipeline system, e.g. due to vortex shedding

(current, waves, wind, towing) or fluid flow- supporting structure movements- fluctuations in operating pressure and temperature.Locations to be checked are the girth welds, seam welds and con-struction details. Seam welds will be more vulnerable to fatiguefor higher steel grades.


804 Special consideration shall be given to the fatigueassessment of construction details likely to cause stress con-centrations, and to the possibility of having low-cycle highstrain fatigue. The specific design criterion to be used dependsupon the analysis method, which may be categorised into:

— methods based upon fracture mechanics (see 805)— methods based upon fatigue tests (see 806).

805 Where appropriate, a calculation procedure based uponfracture mechanics may be used. The specific criterion to beused shall be determined on a case-by-case basis, and shallreflect the target safety levels in Sec.2 C500.For further guidance on fracture mechanics based fatigue anal-yses see Appendix A.806 When using calculation methods based upon fatiguetests, the following shall be considered:

— determination of long-term distribution of stress range, see807

— selection of appropriate S-N curve (characteristic resist-ance), see 808

— determination of Stress Concentration Factor (SCF) notincluded in the S-N curve

— determination of accumulated damage, see 809.

Table 5-8 Resistance strain factors, γ eSafety classLow Medium High2.0 2.5 3.3

DET NORSKE VERITAS


807 As most of the loads which contribute to fatigue are of arandom nature, statistical consideration is normally required indetermining the long-term distribution of fatigue loadingeffects. Where appropriate, deterministic or spectral analysismay be used.808 The characteristic resistance is normally given as S-Ncurves or -N curves, i.e. stress amplitudes (or strain amplitudesfor the case of low-cycle fatigue), versus number of cycles tofailure, N. The S-N curve shall be applicable for the material,construction detail, NDT acceptance criteria and state of stressconsidered, as well as to the surrounding environment. The S-N curve shall be based on the mean curve of log (N) with thesubtraction of two standard deviations in log (N). If a fracturemechanic assessment (ECA) is performed according torequirements in D1100, the S-N curve shall be validated for theallowable defect sizes determined by the ECA or a fracturemechanics based fatigue assessment shall be performed asdescribed in Appendix A. 809 In the general case where stress fluctuations occur withvarying amplitude of random order, the linear damage hypoth-esis (Miner's Rule) may be used. The application of Miner'sRule implies that the long-term distribution of stress range isreplaced by a stress histogram, consisting of a number of con-stant amplitude stress or strain range blocks, (σr)i or (εr)i, andthe corresponding number of repetitions, ni. Thus, the fatiguecriterion is given by:

Where:

Dfat = Miner's sumk = number of stress blocksni = number of stress cycles in stress block iNi = number of cycles to failure at constant stress range of

magnitude (sr)i or strain range (er)i.αfat = allowable damage ratio, see Table 5-9

810 For detailed explanation regarding fatigue calculations/analysis reference is made to DNV-RP-F105 Free SpanningPipelines and DNV-RP-F204 Riser Fatigue. In cases wherethis guideline is not applicable, allowable damage ratios aregiven in Table 5-9.

811 The split between the different phases of the designfatigue life as described in Table 5-9 shall be agreed in the ini-tiation phase of the project and be based on the highest safetyclass during the lifetime.

Guidance note:For a pipeline where e.g. 10% of the design lifetime can be uti-lized during the installation and which is classified as safety classmedium (high) during the operational phase this will correspondto a damage ratio of 2% (1%) of the operational lifetime.A common split between installation, as laid and operation is10%, 10% and 80% but depend on the need for fatigue capacityin the different phases.


D 900 Ovalisation901 Risers and pipelines shall not be subject to excessiveovalisation and this shall be documented. The flattening due tobending, together with the out-of-roundness tolerance from

fabrication of the pipe, is not to exceed 3%, defined as:

The requirement may be relaxed if:

— a corresponding reduction in moment resistance has beenincluded

— geometrical restrictions are met, such as pigging require-ments

— additional cyclic stresses caused by the ovalisation havebeen considered

— tolerances in the relevant repair system are met.

902 Ovalisation shall be checked for point loads at any pointalong the pipeline system. Such point loads may arise at free-span shoulders, artificial supports and support settlements.

D 1000 Accumulated deformation1001 Accumulated plastic deformation of pipe caused bycyclic loads leading to increased diameter or ovality (ratchet-ing) shall be considered. If the ratcheting causes increasedovality, special consideration shall also be made of the effecton buckling resistance.1002 Accumulated longitudinal displacement of the pipeline(pipeline walking) shall be considered. This may occur duringstart-up/shut-down for:

— pipeline shorter than two anchor lengths, or— pipeline parts with virtual anchor, and— pipeline laying on seabed slope, or— pipeline connected to pulling force (e.g. connected to

SCR).

D 1100 Fracture and supplementary requirement P1101 Pipeline systems shall have adequate resistance againstinitiation of unstable fracture. 1102 The safety against unstable fracture is considered satis-factory if the requirements in Table 5-10 are met.

1) The strain levels refers to after NDT.2) Total nominal strain in any direction from a single event.

1103 Pipeline systems transporting gas or mixed gas and liq-uids under high pressure shall have adequate resistance topropagating fracture. This may be achieved by using:

— material with low transition temperature and adequateCharpy V-notch toughness

— adequate DWTT shear fracture area— lowering the stress level— use of mechanical crack arrestors— by a combination of these methods.

(5.32)

Table 5-9 Allowable damage ratio for fatigueSafety Class Low Medium Highα fat 1/3 1/5 1/10

DfatniNi----- a fat≤

i l=

k

∑=

(5.33)

Table 5-10 Requirements to unstable fracture1)

Total nominal strain

Accumulated plastic strain

ε l,nom ≤ 0.4% Materials, welding, workman-ship and testing are in accord-ance with the requirements of this standardAs an alternative girth welds allowable defect sizes may be assessed according to Appendix A.

0.4% < ε l,nom The integrity of the girth welds shall be assessed in accordance with Appendix A

1.0% < ε l,nom2) Supplementary requirement (P)

shall be appliedor 2.0% < ε p

f0Dmax Dmin–

D-------------------------------- 0.03≤=

DET NORSKE VERITAS


Design solutions shall be validated by calculations based uponrelevant experience and/or suitable tests. Requirements to frac-ture arrest properties need not be applied when the pipelinedesign tensile hoop stress is below 40% of fy.1104 Material meeting the supplementary requirement forfracture arrest properties (F) (Sec.7 I200) is considered to haveadequate resistance to running propagating ductile fracture forapplications carrying essentially pure methane up to 80%usage factor, 15 MPa internal pressure and 30 mm wall thick-ness. For depths down to 10 metres and onshore, the requiredCharpy V-notch impact energy shall be specially considered.

D 1200 Ultimate limit state – Accidental loads1201 The design against accidental loads may be performedby direct calculation of the effects imposed by the loads on thestructure, or indirectly, by design of the structure as tolerableto accidents.1202 The acceptance criteria for ALS relate to the overallallowable probability of severe consequences.1203 Design with respect to accidental load must ensure thatthe overall nominal failure probability complies with the nom-inal failure probability target values in Sec.2. The overall nom-inal failure probability from accidental loads can be expressedas the sum of the probability of occurrence of the i'th damagingevent, PDi, times the structural failure probability conditionedon this event, Pf|Di. The requirement is accordingly expressedas:

where Pf,T is the relevant target nominal failure probabilityaccording to Sec.2. The number of discretisation levels mustbe large enough to ensure that the resulting probability is eval-uated with sufficient accuracy.1204 The inherent uncertainty of the frequency and magni-tude of the accidental loads, as well as the approximate natureof the methods for determination of accidental load effects,shall be recognised. Sound engineering judgement and prag-matic evaluations are hence required.1205 If non-linear, dynamic finite element analysis isapplied, it shall be ensured that system performance and localfailure modes (e.g. strain rate, local buckling, joint overloadingand joint fracture) are adequately accounted for by the modelsand procedures applied.1206 A simplified design check with respect to accidentalload may be performed as shown in Table 5-11 using appropri-ate partial safety factors. The adequacy of simplified designcheck must be assessed on the basis of the summation above inorder to verify that the overall failure probability complieswith the target values in Sec.2.

1) When failure mode is bursting the probability of occurrence should be 1-2 order of magnitudes lower, ref Table 2-5.

Note to table: Standard industry practice assumes safety factors equal to 1.0 foran accidental event with a probability of occurrence equal to 10, and survivalof the pipeline is merely related to a conservative definition of characteristicresistance. In this standard, accidental loads and events are introduced in amore general context with a link between probability of occurrence and actualfailure consequence. For combined loading the simplified design check pro-poses a total factor in the range 1.1-1.2, which is consistent with standardindustry practice interpreted as corresponding to safety class Medium for acci-dental loads with a probability of occurrence equal to 10-4.

E. Special Considerations E 100 General101 This subsection gives guidance on conditions that shallbe evaluated separately. Both the load effects and acceptancecriteria are affected.

E 200 Pipe soil interaction201 For limit states influenced by the interaction between thepipeline and the soil, this interaction shall be determined tak-ing due account for all relevant parameters and the uncertain-ties related to these.In general pipeline soil interaction depends on the characteris-tics of the soil, the pipeline, and the failure mode in question,which shall all be properly accounted for in the simulation ofthe pipeline soil interaction.202 The main soil characteristics governing the interactionare the shear strength and deformation properties. 203 Pipeline characteristics of importance are submergedweight, diameter stiffness, roughness of the pipeline surface,and initial embedment from installation which shall all beaccounted for as relevant for the limit state in question.204 All relevant load effects shall be considered. Thisincludes:

— load duration and history effects (e.g. varying verticalreactions from installation laying pressures)

— variations in the unit weight of the pipe (e.g. empty, waterfilled and operation conditions)

— cyclic loading effects (both directly from pipe as well ashydrodynamic loads)

205 Some soils have different resistance values for long termloading and for short term loading, related to the difference indrained and non-drained behaviour and to creep effects in drainedand non-drained condition. This shall be taken into account.206 For limit states involving or allowing for large displace-ments (e.g. lateral pull-in, pipeline expansion of expansionloops, global buckling or when displacements are allowed foron-bottom condition) the soil will be loaded far beyond failure,involving large non-linearities, remoulding of soil, ploughingof soil etc. Such non-linear effects and the uncertainties relatedto these shall be considered.207 For pipelines that are buried (trenched and/or covered bygravel) and susceptible to global buckling the uplift resistanceand possible increased axial resistance shall be considered.The possible effect of backfill material from trenching shall beconsidered.

Guidance note:Due to the uncertainties in governing soil parameters, load effectsetc., it is difficult to define universally valid methods for simulationof pipe soil interaction effects. The limitations of the methods used,whether theoretically or empirically based, shall be thoroughlyconsidered in relation to the problem at hand. Extrapolation beyonddocumented validity of a method shall be performed with care, asshall simplifications from the problem at hand to the calculationmodel used. When large uncertainties exist, the use of more thanone calculation approach shall be considered.


(5.34)

Table 5-11 Simplified Design Check versus Accidental loadsProb. of occurrence 1)

Safety Class Low

Safety Class Medium

Safety Class High

> 10-2 Accidental loads may be regarded similar to envi-ronmental loads and may be evaluated similar to

ULS design check10-2 – 10-3 To be evaluated on a case by case basis10-3 – 10-4 γC = 1.0 γC = 1.0 γC = 1.010-4 – 10-5 γC = 0.9 γC = 0.910-5 – 10-6 Accidental loads or events may

be disregardedγC = 0.8

< 10-6

pf Di PDi pf T,≤⋅∑

DET NORSKE VERITAS


E 300 Spanning risers/pipelines301 Spanning risers and pipelines shall have adequate safetyagainst local buckling, fatigue, fracture and ovality and theseshall be documented. 302 For design of free spanning pipelines, reference is madeto DNV-RP-F105 Free Spanning Pipelines. For fatigue designof risers, reference is given to DNV-RP-F204 Riser Fatigue.

E 400 On bottom stability401 The pipeline shall be supported, anchored in opentrench, or buried in such a way that under extreme functionaland environmental loading conditions, the pipeline will notmove from its as-installed position. This does not include per-missible lateral or vertical movements, thermal expansion, anda limited amount of settlement after installation.

Guidance note:The acceptance criterion on permissible movements may varyalong the pipeline route. Examples of possible limitations topipeline movements include:- local buckling, fatigue and fracture of pipe- deterioration/wear of coating- geometrical limitations of supports- distance from other pipelines, structures or obstacles.


402 Liquid or gas pipelines in the air- or gas-filled conditionshall have a specific gravity which is higher than that of thesurrounding sea water (negative buoyancy).403 When the pipeline is routed in areas that may be influ-enced by unstable slopes, that could lead to slope failure andflow of soil that will impact the pipeline, the probability ofsuch slope failures shall be evaluated. Any relevant slope fail-ure triggering effect, such as wave loading, earthquake loadingor man made activities (e.g. the pipe-laying itself), shall beconsidered. Possible flow rates and densities at the pipelineshall be evaluated for stability. If stability can not be guaran-teed by sufficient weight of the pipeline, by burial of the pipe-line or by other means, re-routing of the pipeline shall berequired.404 For weight calculations of the pipe, the nominal wallthickness shall be reduced to compensate for the expectedaverage weight reduction due to metal loss. For pipelines withminor corrosion allowance this reduction may be omitted andthe nominal thickness used.405 Buried pipelines shall have adequate safety against sink-ing or flotation. For both liquid and gas pipelines, sinking shallbe considered assuming that the pipeline is water filled, andflotation shall be considered assuming that the pipeline is gasor air filled (if relevant).406 If the specific submerged weight of the water-filled pipeis less than that of the soil, then no further analyses are requiredto document safety against sinking. If pipelines are installed insoils having a low shear strength, then the soil bearing resist-ance shall be documented. If the soil is, or is likely to be, liq-uefied, it shall be documented that the depth of sinking will besatisfactorily limited (either by the depth of liquefaction or bythe build-up of vertical resistance during sinking) meeting therequirements of D above.407 If the specific submerged weight of the gas- or air-filledpipe is less than that of the soil, it shall be documented that theshear strength of the soil is adequate to prevent flotation. Thus,in soils which are or may be liquefied, the specific weight ofthe buried gas- or air-filled pipeline is not to be less than thatof the soil.408 Pipelines resting directly on the sea bottom without anyspecial supporting structures or anchoring devices other than

weight coating, shall be designed against sinking as describedunder 405 above. Special considerations shall here be made tomechanical components such as valves and Tee's.409 It shall be documented that pipelines situated on the seabottom have adequate safety against being lifted off the bottomor moved horizontally. For assessment of horizontal (trans-verse) stability of pipelines exposed to wave and current loads,reference is made to DNV-RP-F109 On-bottom StabilityDesign of Submarine Pipeline.410 The most unfavourable combination of simultaneouslyacting vertical and horizontal forces on the pipeline shall beconsidered. When determining this unfavourable combination,the variation in forces along the line, including directionalityeffects of waves and current, shall be addressed.411 The transverse pipeline stability may be assessed usingthree-dimensional dynamic or two-dimensional static analysismethods. The dynamic analysis methods allow limited pipemovements, but require accurate three-dimensional modelling.The static analysis method may be expressed by:412 The coefficient of equivalent friction, µ, may varywithin a wide range depending on the seabed soil, surfaceroughness, weight and diameter of the pipeline. When thepipeline has some penetration into the soil, the lateral resist-ance includes both friction type resistance and resistance dueto mobilising the soil outside the contact surface. In such casesthe equivalent friction coefficient may vary with the verticalload level.413 Axial (longitudinal) stability shall be checked. Theanode structural connection (when exposed to friction, e.g.,pipelines without weight coating) shall be sufficient to sustainthe anticipated friction force.414 Pipeline movements due to thermal axial expansion,shall be allowed for near platforms/structures (e.g. at riser tie-in point) and where the pipeline changes direction (e.g. at off-set spools). The expansion calculations shall be based uponconservative values for the axial frictional resistance.415 In shallow water, the repeated loading effects due towave action may lead to a reduction of the shear strength of thesoil. This shall be considered in the analysis, particularly if theback fill consists of loose sand which may be susceptible to liq-uefaction.416 If the stability of the pipeline depends on the stability ofthe seabed, the latter should be checked.

E 500 Trawling interference501 The pipeline system shall be checked for all three load-ing phases due to trawl gear interaction, as outlined in Sec.4 F.For more detailed description, reference is made to DNV-RP-F111 Interference between Trawl Gear and Pipelines.502 The acceptance criteria are dependent on the trawlingfrequency (impact) and the safety classification (pull-over andhooking) given in Sec.2 C400.503 The acceptance criteria for trawl impact refer to anacceptable dent size. The maximum accepted ratio of perma-nent dent depth to the pipe diameter is:

where:

Hp = permanent plastic dent depthη = usage factor given in Table 5-12. Load effect factors

equal to unity.

(5.35)η05.0≤D

H P

DET NORSKE VERITAS


504 When allowing for permanent dents, additional failuremodes such as fatigue and collapse shall be taken into account.Any beneficial effect of internal over-pressure, i.e. "pop-out"shall not normally be included. The beneficial effects of pro-tective coating may be taken into account. The impact effec-tiveness of coating shall be documented.505 Pullover loads shall be checked in combination withother relevant load effects. All relevant failure modes for lat-eral buckling shall be checked. Accumulation of damage dueto subsequent trawling is not normally allowed.506 Hooking loads shall be checked in combination with otherrelevant load effects. All relevant failures modes shall be checked.

E 600 Third party loads, dropped objects601 The pipeline shall be designed for impact forces causedby, e.g. dropped objects, fishing gear or collisions. The designmay be achieved either by design of pipe, protection or meansto avoid impacts.602 The design criteria shall be based upon the frequency/likelihood of the impact force and classified as accidental,environmental or functional correspondingly, see D1200.603 For guidance on impacts, reference is made to DNV-RP-F107 Risk Assessment of Pipeline Protection.

E 700 Thermal Insulation701 When a submerged pipeline is thermally insulated, itshall be documented that the insulation is resistant to the com-bination of water, temperature and hydrostatic pressure.702 Furthermore, the insulation should be resistant to oil andoil-based products, if relevant. The insulation shall also have therequired mechanical strength to external loads, as applicable.703 Degradation of the insulation during construction andoperation should be considered.

E 800 Settings from Plugs801 For loads from plugs, reference is given to DNV-RP-F113 Pipeline Subsea Repair.

F. Pipeline Components and Accessories

F 100 General101 This Subsection is applicable to pressure containingcomponents (e.g. bends, flanges and connectors, Tee’s, valvesetc.) used in the submarine pipeline system. Supporting struc-ture requirements are given in G.102 Design of components may be based on the industry rec-ognised codes as listed in Table 5-13 but shall also complywith the structural design and functional requirements of thissub-section and with the material, manufacturing and test

requirements for components in Sec.8.

1) Other recognised equivalent codes may be used. 2) Required in case the code used in the design of a component does not take

into account forces other than the internal pressure, see 105.

103 All pressure containing components used in the subma-rine pipeline system shall generally represent at least the samesafety level as the connecting riser/pipeline section.104 The component shall be designed to accommodate theloading from connected the pipeline section and vice versawith appropriate safety.105 The design of pipeline components shall be according torecognised codes. If the code used in the design of a compo-nent does not take into account forces other than the internalpressure, additional evaluations, e.g. non-linear FE analysesaccording to; ASME VIII Division 2 / EN 13445 / PD 5500,are required in order to address the maximum forces that canbe transferred to the component from the connecting pipelinesections under installation and operation.The strength shall, as a minimum be:

— equivalent to the connecting pipeline, or— sufficient to accommodate the most probable maximum

100-year load effect that will be transferred to the compo-nent from the connecting pipeline under installation andoperation, see Sec.4.

106 The load scenarios as described in Sec.4 as well as par-ticular loads associated with the component shall be analysed.This implies that also external hydrostatic pressure shall beconsidered in the design with respect to both strength and inter-nal leakage when relevant.107 For material susceptible to HISC, see Sec.6 D500.108 Sealing systems should be designed to allow testingwithout pressurising the pipeline.109 The pigging requirements in B114 and B115 shall beconsidered for the component.

Table 5-12 Usage factor (η) for trawl door impactImpact frequency(per year per km)

Usage factorη

> 100 01-100 0.310-4-1 0.7

Table 5-13 Referenced standards for structural design of componentsComponent Design Code1) Additional design

requirementsAll Components listed below 2)

Non-linear FE analyses according to; ASME VIII Division 2 / EN 13445 / PD 5500

F100

Induction Bends

ISO 15590-1F200

Fittings Bends: F200Tees: ASME B31.4, B31.8 F600

Flanges 15590-3/ ISO 7005-1 or NORSOK L005 / EN 1591-1

Valves ISO 14723 F500Mechanical connectors

ASME VIII Division 2 / EN 13445 / PD 5500

Couplings and repair clamps, hot taps

DNV-RP-F113Hot taps: API RP 2201

Bolting ASME VIII Division 2 / EN 13445 / PD 5500

CP Insulating joints

ASME VIII Division 2 / EN 13445 / PD 5500

F300

Anchor flanges N.A. see Note 2) Buckle and fracture arres-torsPig traps ASME VIII Division 2 / EN

13445 / PD 5500F400

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110 Transitions in C-Mn and low alloy steels where the nom-inal material thickness or yield stress is unequal shall be inaccordance with ASME B 31.8 Appendix I, Figure 15 orequally recognised codes. Transition in C-Mn linepipe bymeans of an external or internal taper shall not be steeper than1 in 4. If transitions to these requirements are not feasible, atransition piece shall be inserted. 111 Transitions in duplex stainless steels and 13Cr marten-sitic stainless steels shall be such that the local stresses will notexceed 0.8 SMYS.112 Internal transitions between different wall thicknessesand internal diameters for girth welds in pipes of equal SMYSmay be made in the base material provided radiographic exam-ination only is specified.113 For welds to be examined by ultrasonic testing, transi-tion tapering in the base material should be avoided. If taperingis unavoidable the pipe ends shall be machined to provide par-allel external and internal surfaces before the start of the taper.The length of the parallel surfaces shall at least be sufficient toallow scanning from the external surface and sufficient for therequired reflection off the parallel internal surface. 114 Specifications for installation and make-up of the com-ponent shall be established.115 The pressure testing of components (i.e. Factory Accept-ance Test) to be in accordance with specified design code.

F 200 Design of bends201 This Standard does not provide any limit state criteriafor pipeline bends.

Guidance note:Bends exposed to bending moments behave differently fromstraight pipes. Ovalisation becomes the first order of deformationand changes the stress pattern considerably compared to straightpipes.


202 As an alternative to recognised codes the following sim-plified Allowable Stress Design (ASD) check may be usedprovided that:

— The pressure containment criterion in D200 is fulfilled.— The applied moment and axial load can be considered dis-

placement controlled.— The bend is exposed to internal over pressure or that the

bend has no potential for collapse. This can be consideredfulfilled if the system collapse design capacity is threetimes the external overpressure in question. The externalpressure differential for the collapse limit state, pe - pmin,shall hence be multiplied by a factor of 3 in Eq 5.14.

— That the imposed shape distortion (e.g. ovalisation) isacceptable.

The ASD criteria read:

where

η = usage factor as given by Table 5-13N = pipe wall force M = bending moment.

Guidance note:The ovalisation of the bend has typically to be determined byfinite element calculation. The acceptable distortion will typi-cally governed by the bullet points in D900.


F 300 Design of insulating joints301 CP insulating joints shall be of the boltless, monolithiccoupling type and shall be provided with a double seal system. 302 Insulating joints shall be fitted with pup pieces withmechanical properties and dimensions identical to that of theadjoining pipeline.303 Insulating joints shall be capable of meeting the testrequirements given in Sec.8 B900 and to withstand the effectsof the environment without loss of performance.304 To protect insulating joints and CP equipment fromlightning effects, lightning protection shall be installed. Surgearrestors should be mounted across insulating joints and outputterminals of D.C. voltage sources. Such measures should takeinto account the need for potential equalisation between thepipeline, anodes, power supplies, reference electrodes, etc.during lightning strikes. Alternative devices to the spark gaptype can be used if documented to be reliable.305 Bolting shall meet the requirements of Sec.6 C400.306 All elastomeric materials used shall have a documentedperformance. The sealing materials shall have documenteddecompression, creep and temperature properties. O-ring sealsshall be resistant to explosive decompression and AED certified.AED certification is not required for seals other than O-rings,provided they are enclosed in a completely confined space.Sealing surfaces exposed to sea water shall be made of materi-als resistant to sea water at ambient temperature.307 The insulating materials, including dielectric strength,compressive strength and suitability for use at the design tem-peratures shall be documented by testing in accordance withASTM D 695.

F 400 Design of pig traps401 The design of closures and items such as nozzle rein-forcements, saddle supports, vent- kick and drain branchesshall comply with the applied design standard.402 Closures shall be designed such that the closure cannotbe opened while the pig trap is pressurised. An interlockarrangement with the main pipeline valve should be provided.

F 500 Design of valves.501 The design shall ensure that internal gaskets are able toseal, and shall include a documented safety margin which isvalid during all relevant pipeline operating conditions. Sealingwill be sensitive to internal deflections, enlargement of gapsand changes in their support conditions. Valve operation willbe sensitive to friction and clearances.502 Consideration should be given to requirements for dura-bility when exposed to abrasive material (e.g. weld scale, sandetc.) or to fire loads.503 Valves with requirements for fire durability shall bequalified by applicable fire tests. Reference may be made to

σe ≤ η · fy (5.36)σl ≤ η · fy (5.37)

(5.38)

(5.39)

(5.40)

222 3 hllhlhe τσσσσσ ⋅+⋅−+≤

( )2

2

2 ttDpp eih ⋅

−−=σ

DtDD

MttD

Nl

⋅⋅−−⋅

+⋅−⋅

=

32))2(()( 4

24

22 ππσ

Table 5-14 Usage factors for equivalent stress checkSafety class

Low Medium Highη 1.00 0.90 0.80

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API 6FA and ISO 10497 for test procedures.504 Valve control systems and actuators shall be designedand manufactured in accordance with recognised standards.The valve actuator specification should define torque require-ments for valve operation, with a suitable safety margin toaccommodate deterioration and friction increase during serv-ice.505 If the code or standard used for design of a componentdoes not take into account the possibility for internal leakagedue to forces transferred to the component from the connectingpipeline sections, the additional calculations or qualificationtests shall be performed.

F 600 Pipeline fittings601 Tees shall be of the extruded outlet, integral reinforce-ment type. The design shall be according to ASME B31.4,B31.8 or equivalent. 602 Bars of barred tees should not be welded directly to thehigh stress areas around the extrusion neck. It is recommendedthat the bars transverse to the flow direction are welded to apup piece, and that the bars parallel to the flow direction arewelded to the transverse bars only. If this is impracticable,alternative designs should be considered in order to avoid peakstresses at the ends.603 Y-pieces and tees where the axis of the outlet is not per-pendicular to the axis of the run (lateral tees) shall not bedesigned to ASME B31.4 or B31.8, as these items require spe-cial consideration, i.e. design by finite element analysis. 604 The design of hot taps shall ensure that the use of and thedesign of the component will result in compliance with API RP2201, "Procedure for Welding and Hot Tapping on Equipmentin Service".605 Standard butt welding fittings complying with ANSIB16.9, MSS SP-75 or equivalent standards may be used pro-vided that:

— the actual bursting strength of the fitting is demonstratedto exceed that of the adjoining pipe

— the fitting is demonstrated to be able to accommodate themaximum forces that can occur in the pipeline in accord-ance with A105.

606 Branch welding fittings with a size exceeding 2 inchesor 20% of the pipe circumference shall not be used. Socketwelding fittings are not permitted.

G. Supporting StructureG 100 General101 Structural items such as support and protective struc-tures that are not welded onto pressurized parts are consideredas structural elements. 102 Steel structural elements shall be designed according toDNV-OS-C101 Design of Offshore Steel Structures, General(LRFD method).

G 200 Pipe-in-pipe and bundles201 For pipe-in-pipe and bundle configurations, advantagemay be taken of other loading conditions, e.g. pressure con-tainment for the outer pipe. When determining the safety class,advantage may also be taken on the reduced failure conse-quences compared to those of ordinary pipelines.202 The combined effective force for a pipe-in-pipe or abundle may be calculated using the expression in Sec.4 G300for each component and summing over all components. Theexternal pressure for each component shall be taken as thepressure acting on its external surface, i.e. the pressure in the

void for internal pipes. Release of effective axial force by endexpansions, lateral and/or vertical deformations or bucklingdepends on how the pipes may slide relatively to each other.Therefore, analysis of cases where the effective axial force isimportant, such as analysis of expansion, buckling and dynam-ics, requires accurate modelling of axial restraints such asspacers, bulkheads etc.

G 300 Riser supports301 The riser supports should be designed against the possi-ble forms of failure with at least the same degree of safety asthat of the riser they support. However, if safety considerationsindicate that the overall safety is increased by a reduction ofthe failure load of certain supports, such considerations maygovern the support design (weak link principle).302 For bolted connections, consideration shall be given tofriction factors, plate or shell element stresses, relaxation, pipecrushing, stress corrosion cracking, galvanic corrosion,fatigue, brittle failure, and other factors that may be relevant.303 For supports with doubler and/or gusset plates consider-ation shall be given to lamellar tearing, pull out, elementstresses, effective weld length, stress concentrations andexcessive rotation. See also B108 through B111.304 In clamps utilising elastomeric linings, the long-termperformance of the material with regard to creep, sea water andair or sun light resistance shall be determined.

G 400 J-tubes401 An overall conceptual evaluation shall be made in orderto define the required:

— safety class— impact design— pressure containment resistance.

402 The J-tube shall be designed against the failure modesgiven in D100.

Guidance note:301 above includes evaluation of whether the j-tube shall bedesigned for the full design pressure and to which safety class(i.e. hoop stress usage factors). The J-tube concept may e.g. bebased on "burst disc" which will imply that a lower pressure con-tainment resistance shall be governing. Other relevant evalua-tions may be J-tube pull-in forces, external impact, corrosion etc.


403 The J-tube spools should be joined by welding.

G 500 Stability of gravel supports and gravel covers501 This applies to all types of gravel supports and covers,such as free span supports for installation and operating phases(excessive bending and fatigue), separation and pipeline stabi-lisation at crossings, suppressing of upheaval buckling, axialrestraints/locking, stabilisation of pipeline etc.502 The design of the gravel supports and covers shall con-sider the consequence of failure.503 The design of the gravel supports and covers shall beperformed using recognised methods.504 The design of the gravel supports and covers shall consider:

— weight of gravel supports and/or covers and pipeline— loads imposed by pipeline (e.g. due expansion)— seabed slope, both longitudinal and horizontal— uncertainty in soil characteristics— resistance against hydrodynamic loads— slope failure (e.g. due to earthquakes)— uncertainty in survey data— subsea gravel installation tolerances, both horizontal and

vertical.

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H. Installation and RepairH 100 General101 The linepipe transportation should comply with therequirements of API5L and API5LW.102 The pipeline strength and stability shall be determinedaccording to D and E above.

Guidance note:According to this standard, equivalent limit states are used for allphases. Hence the design criteria in this section also apply to theinstallation phase. Installation is usually classified as a lowersafety class (safety class low) than operation, corresponding tolower partial safety factors (higher failure probability).


103 The design analysis for the submarine pipeline systemshall include both installation and repair activities, in order toensure that they can be installed and repaired without sufferingdamage or requiring hazardous installation or repair work.104 The design shall verify adequate strength during all rel-evant installation phases and techniques to be used, including:

— initiation of pipe laying operation— normal continuous pipe laying— pipe lay abandonment and pipeline retrieval— termination of laying operation— tow out operations (bottom tow, off-bottom tow, control-

led depth tow and surface tow)— pipeline reeling and unreeling— trenching and back filling— riser and spool installation— tie-in operations— landfalls.

105 The configuration of pipeline sections under installationshall be determined from the laying vessel to the final positionon the seabed. The configuration shall be such that the stress/strain levels are acceptable when all relevant effects are takeninto account. Discontinuities due to weight coating, bucklearrestors, in-line assemblies etc. shall be considered.106 The variation in laying parameters that affect the config-uration shall be considered. An allowed range of parametervariation shall be established for the installation operation.107 Critical laying parameters shall be determined for theinstallation limit condition, see Sec.4 C600 and Sec.10 D400.108 Configuration considerations for risers and pipelinesshall also be made for other installation and repair activities,and the allowed parameter variations and operating limit con-ditions shall be established.109 If the installation and repair analyses for a proposedpipeline system show that the required parameters cannot beobtained with the equipment to be used, the pipeline systemshall be modified accordingly.110 The flattening due to a permanent bending curvature,together with the out-of-roundness tolerances from fabricationof the pipe shall meet the requirements defined in D900.

H 200 Pipe straightness201 The primary requirement regarding permanent deforma-tion during construction, installation and repair is the resultingstraightness of the pipeline. This shall be determined and eval-uated with due considerations of effects on:

— instability— positioning of pipeline components e.g. valves and Tee-

joints— operation.

202 The possibility of instability due to out of straightnessduring installation (twisting) and the corresponding conse-quence shall be determined.203 If Tee-joints and other equipment are to be installed asan integrated part of the pipeline assembled at the lay barge, norotation of the pipe due to plastification effects shall be permit-ted. In this case the residual strain from bending at the over-bend shall satisfy the following during installation:

where

εr = residual strain from over bendγrot = 1.3 safety factor for residual strainεr,rot = limit residual strain from over bend.

204 The above equations only consider rotation due to resid-ual strain from installation along a straight path. Other effectscan also give rotation (curved lay route, eccentric weight,hydrodynamic loads, reduced rotational resistance during pullsdue to lateral play/elasticity in tensioners/pads/tracks etc.) andneed to be considered.205 Instability during operation, due to out of straightnesscaused by the installation method and the corresponding con-sequences, shall be determined. Residual stresses affectingpresent and future operations and modifications shall also beconsidered.206 The requirement for straightness applies to the assumedmost unfavourable functional and environmental load condi-tions during installation and repair. This requirement alsoapplies to sections of a pipeline where the strains are com-pletely controlled by the curvature of a rigid ramp (e.g. stingeron installation vessel), whether or not environmental loads areacting on the pipe.

Guidance note:Rotation of the pipe within the tensioner clamps of the pipe dueto elasticity of the rubber and slack shall be included in the eval-uation of the rotation.


H 300 Coating301 Concrete crushing due to excessive compressive forcesfor static conditions in the concrete during bending at the over-bend is not acceptable.

(5.41)rotrrrot ,εεγ ≤

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SECTION 6DESIGN - MATERIALS ENGINEERING

A. General

A 100 Objective101 This section provides requirements and guidelines to theselection of materials for submarine pipeline systems and tothe external and internal corrosion control of such systems.Also covered is the specification of linepipe, pipeline compo-nents, coatings and cathodic protection. Finally, general con-siderations for fabrication applicable to the design phase areaddressed. 102 The purpose of performing materials selection is toassess the feasibility of different candidate materials (includ-ing CRA’s) to meet functional requirements for linepipe andfor other components of a pipeline system. It may also includea cost comparison between candidate materials, including thecalculated costs for operation and any associated risk cost (seeD701). This activity is generally carried out during conceptualdesign of submarine pipeline systems.

A 200 Application201 This section is applicable to the conceptual and designphases for submarine pipeline systems. It contains both norma-tive requirements and information. (Sub-sections containingonly informative text are indicated ‘Informative’ in heading)202 Functional requirements for materials and manufactur-ing procedures for linepipe and pipeline components are con-tained in Sec.7 and 8, respectively. Manufacture andinstallation of systems for external corrosion control isaddressed in Sec. 9. Sec. 9 also contains functional require-ments to any concrete coating.

A 300 Documentation301 The selection of materials during conceptual and/ordetailed design shall be documented, preferably in a “MaterialsSelection Report”, referring to the requirements and recom-mendations in this section, including use of CRAs, corrosionallowance and provisions for internal corrosion control. In thematerial selection document design premises for materialsselection should be identified, making reference to the designbasis and any other relevant project documents, together withthe applicable codes and standards. 302 Any requirements and conditions on pipeline fabricationand operational procedures used as the basis for materialsselection shall be duly high-lighted in the document to ensurethat they are adequately transferred into these phases of thepipeline.

Guidance note:The internal corrosion control of pipelines carrying potentiallycorrosive fluids based on chemical treatment is much based onconditions for periodic cleaning, corrosion monitoring andinspection of the integrity of the pipeline which are not alwaysdefined in the project design basis and need to be verified by theoperator of the pipeline.


303 As a result of design activities, specifications of linepipematerial, pipeline components (including bolts and nuts), pipe-line coatings (including field joint coating and any concretecoating), anode manufacture and installation shall further beprepared as separate documents. Moreover, the design docu-mentation shall include a cathodic protection design report.

B. Materials Selection for Linepipe and Pipeline Components

B 100 General101 Materials for pipeline systems shall be selected with dueconsideration of the fluid to be transported, loads, temperatureand possible failure modes during installation and operation.The selection of materials shall ensure compatibility of allcomponents of the pipeline system. The following materialcharacteristics shall be considered:

— mechanical properties— hardness— fracture toughness— fatigue resistance— weldability— corrosion resistance.

102 Materials selection shall include identification of the fol-lowing supplementary requirements for linepipe given inSec.7 I as required:

— supplementary requirement S, sour service (see B200)— supplementary requirement F, fracture arrest properties

(see B406)— supplementary requirement P, linepipe exposed to plastic

deformation exceeding the thresholds specified in Sec.5D1102 (see B407-408)

— supplementary requirement D, more stringent dimensionalrequirements (see B402)

— supplementary requirement U, increased utilisation (seeB409).

103 The mechanical properties, chemical composition,weldability and corrosion resistance of materials used in com-ponents shall be compatible with the part of the pipeline sys-tem where they are located. Low internal temperatures due tosystem depressurisation shall be considered during the mate-rial selection.

B 200 Sour service201 Pipelines to route fluids containing hydrogen sulphide(H2S) shall be evaluated for ‘sour service’ according toISO 15156. For all pipeline components exposed to such inter-nal fluids, materials shall be selected for compliance with thisstandard. For materials specified for sour service inISO 15156, specific hardness requirements always apply.These are applicable both to manufactured materials as-deliv-ered after manufacture and after fabrication (e.g. welding). Forcertain materials, restrictions for manufacture (e.g. heat treat-ment) and fabrication (e.g. cold forming) apply).

Guidance note:ISO 15156-2/3 giving requirements for materials selection werefirst published in 2004. As per 2006, 4 (four) corrigenda had beenpublished with requirements and guidelines overruling the pub-lished standard and previous corrigenda. The user of this stand-ard shall ensure that the applicable corrigenda are used.


202 Any materials to be used which are not covered byISO 15156 (e.g. type 13Cr steels), shall be qualified accordingto the said standard. The same applies if a material specifiedfor sour service is to be used beyond the conditions specified(e.g. max. hardness). In accordance with ISO 15156-2/3, thepipeline owner shall verify and retain the qualification recordsin case the testing was initiated by a contractor or supplier.

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Guidance note:Purchaser may consider to specify SSC testing of material gradesmeeting all requirements for sour service in this standard, as apart of a program for pre-qualification of linepipe manufacturingor pipeline installation procedures. For such testing, the methodsand acceptance criteria in ISO 15156-2/3 apply.


203 The qualification and selection of materials according toISO 15156 are applicable to equipment designed and con-structed using conventional elastic design criteria. When otherdesign criteria are applied qualification testing shall be consid-ered, unless relevant documentation is provided.204 Supplementary requirements to sour service in thisstandard are given in Sec.7 I100 and Sec.8 C500.

B 300 Corrosion resistant alloys (informative)301 Type 13Cr martensitic stainless steels (i.e. proprietaryalloys developed for oil/gas pipelines) are generally consid-ered fully resistant to CO2-corrosion, provided welds haveadequate PWHT. 22Cr and 25Cr duplex stainless steel andaustenitic CRA’s are also fully resistant and do not requirePWHT. Duplex and martensitic stainless steels may be less tol-erant than C-Mn steel to well stimulation acids. Corrosioninhibitors for such acids and developed for the latter materialsmay not be effective for CRA’s.302 Under conditions when water, oxygen and chloride canbe present in the fluid, e.g. water injection, stainless steels canbe susceptible to localised corrosion. Hence the corrosionresistance shall be considered for each specific application. Forspecial applications, corrosion testing should be considered toqualify the material for the intended use.Alloy 625 (UNS N06625) is generally considered immune toambient temperature seawater. Also type 25Cr duplex (e.g.UNS S32750/S32760) are generally resistant to ambient tem-perature seawater but require more stringent control of micro-structure in base material and weld, consequently corrosiontesting are often included for the qualification of manufactur-ing and fabrication procedures of these materials. Type 22Crduplex, AISI 316 and Alloy 825 (UNS N08825) are not resist-ant to corrosion by raw seawater but are applicable for compo-nents exposed to treated seawater (deoxygenated to max.10 ppb and max. 100 ppb as max monthly and daily residualconcentrations of oxygen). For the latter materials, corrosiontesting is not normally included in specifications for manufac-ture and fabrication.303 Duplex and martensitic stainless steel linepipe and pipe-line components require special considerations of the suscepti-bility of environmentally assisted cracking, primarily (HISC),see E502, Guidance note. In particular this applies to materialsubjected to plastic straining during installation and/or opera-tion with cathodic protection applied. PWHT is known toreduce the HISC susceptibility of welds for 13Cr martensiticstainless steel. For duplex stainless steel, HISC design recom-mendations are given in DNV-RP-F112. 304 In addition to resistance to internal corrosion and envi-ronmentally assisted cracking, the following major parametersshall be considered:

— mechanical properties— ease of fabrication, particularly weldability.

Guidance note:Procurement conditions such as availability, lead times and costsshould also be considered.


B 400 Linepipe (informative)401 Acceptance criteria and inspection requirements forlinepipe are given in Sec.7, with supplementary requirements

specified in Subsection I. Additional information, relevant forthe selection and specification of linepipe is provided below.Dimensional tolerances402 When significant plastic straining is required duringinstallation or operation Supplementary requirement D is nor-mally specified. The most prominent benefit of specifyingSupplementary requirement D is the eased fit-up for welding.Improved fit-up implies reduced stress concentrations andimproved structural integrity. The tolerances specified inSec.7 I400 are considered to be in the uppermost range of whatmay be achieved by reputable pipe mills. Stricter tolerancesand additional requirements such as e.g. pipe eccentricity maybe specified for further improvements, but may be costly asmachining may be required.Corrosion testing of the CRA material of clad or lined linepipe403 For alloy 625 clad or lined pipe specified to be seawaterresistant, testing according to ASTM G48, Method C, shouldbe considered, with acceptance criteria as for 25Cr duplex, seeSec.7 C409.Gripping force of lined linepipe404 In accordance with Sec.7 D510 the gripping force shalldetermined with due consideration of the project requirements,especially the level of installation and operational bendingstresses. If no particular requirements are identified therequirement should be based on the gripping force obtainedduring MPQT.Influence of coating application on mechanical properties405 Pipe tensile properties may be affected by high temper-ature during coating application. During pipe coating, includ-ing field coating, the pipes might be exposed to temperaturesup to approximately 250ºC. For TMCP processed pipes andcold formed pipes not subjected to further heat treatmentmechanical properties may change due to strain aging, causinge.g. increased yield stress. This may further affect the criticaldefect size considerably if the pipe is strained above the yieldstress.Fracture arrest properties406 Supplementary requirements to fracture arrest proper-ties are given in Sec.7 I200 and are valid for gas pipelines car-rying essentially pure methane up to 80% usage factor, up to apressure of 15 MPa, 30 mm wall thickness and 1120 mm diam-eter.For conditions outside the above limitations the required frac-ture arrest properties should be based on calculations whichreflect the actual conditions or on full-scale tests. The fracturetoughness required to arrest fracture propagation for rich gas,i.e. gas mixtures that enter the two-phase state during decom-pression can be much higher than for essentially pure methane.Calculations should be carried out by use of the Battelle TwoCurve Method (TCM) and the appropriate correction factor forcalculated required Charpy values ≥ 95 J. It is strongly recom-mended that the Battelle TCM is calibrated by use of data fromfull-scale test which are as close as possible to the actual pipe-line conditions with regard to gas pressure, pipeline dimen-sions and gas composition. Although the Battelle TCM isbased on physical models of the speed of crack propagationand the speed of decompression, it includes constants that arebased on fitting data and calculations within a limited range oftest conditions.Reeling of longitudinally welded pipes and clad pipes407 Due to the limited field experience, special considera-tions should be made for longitudinally welded pipes to ensurethat both the longitudinal weld, heat affected zone and basematerial of such pipes are fit for intended use after significantstraining. 408 It is recommended that the weld metal strength of the

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pipe longitudinal weld overmatches the strength of the basematerial. It is further recommended to have a limited cap rein-forcement of the longitudinal weld in order to avoid strain con-centrations.Supplementary requirement U - Qualification in retrospect409 The Purchaser may in retrospect upgrade a pipe deliveryto be in accordance with Supplementary requirement U. Incase of more than 50 test units it must be demonstrated that theactual average yield stress is at least two (2.0) standard devia-tions above SMYS. If the number of test units are between 10and 20 the actual average yield stress shall as a minimum be2.3 standard deviations above SMYS, and 2.1 if the number oftest units are between 21 and 49.

B 500 Pipeline components (informative)501 Materials for components shall be selected to complywith internationally recognised standards meeting the require-ments given in Sec.7 and Sec.8. Modification of the chemicalcomposition given in such standards may be necessary toobtain a sufficient combination of weldability, hardenability,strength, ductility, toughness and corrosion resistance.502 A component should be forged rather than cast when-ever a favourable grain flow pattern, a maximum degree ofhomogeneity, and the absence of internal flaws are of impor-tance.503 For component material delivered in the quenched andtempered condition, the tempering temperature shall be suffi-ciently high to allow effective post weld heat treatment duringlater manufacture / installation. The minimum tempering tem-perature should, if lower than 610°C, be specified by the pur-chaser.If welds between the component and other items such as line-pipe are to be post weld heat treated at a later stage, or if anyother heat treatment is intended, a simulated heat treatment ofthe test piece should, if required, be specified by the purchaser.504 If the chemical composition and the delivery conditionof components require qualification of a specific welding pro-cedure for welding of the joint between the component and theconnecting linepipe, then the component should be fitted withpup pieces of the linepipe material in order to avoid field weld-ing of these components.Alternatively, rings of the component material should be pro-vided for welding procedure qualification of the field weld.505 Particular consideration shall be given to the suitabilityof elastomers and polymers for use in the specific applicationand service conditions.

B 600 Bolts and nuts601 Carbon and low alloy steel bolts and nuts for pressurecontaining and main structural applications shall be selected inaccordance with Table 6-1.

602 When bolts and nuts shall be used at elevated tempera-ture strength de-rating shall be applied, see Sec.5 C300.603 Stainless steel according to ASTM A193 grade B8M(type AISI 316) is applicable but requires efficient cathodicprotection for subsea use. UNS N06625 (Alloy 625) is appli-

cable as subsea bolting material without cathodic protectionbut should only be used in the solution annealed or annealedcondition (ASTM B446) or cold-worked to SMYS 550 MPamaximum, unless exposure to cathodic protection can beexcluded. Restrictions for sour service according to ISO 15156shall apply when applicable.604 To restrict damage by HISC for low alloy and carbonsteels, the hardness for any bolts and nuts to receive cathodicprotection shall not exceed 350 HV, as specified for the stand-ard grades in Table 6.1. The same restriction shall apply forsolution annealed or cold-worked type AISI 316 austeniticstainless steel and any other cold-worked austenitic alloys.Precipitation hardening Fe-or Ni-base alloys, duplex and mar-tensitic stainless steels should not be specified as bolting mate-rial if subject to cathodic protection. The hardness of bolts andnuts shall be verified for each lot (i.e. bolts of the same size andmaterial, from each heat of steel and heat treatment batch).605 Any coating of bolts shall be selected with due consider-ations of how such coatings affect tensioning and as-installedproperties.

Guidance note:Zinc coating, phosphating and epoxy based coatings are applica-ble; however, there have been concerns that hot-dip zinc coatingmay cause loss of bolt tensioning and that polymeric coatingsmay prevent efficient cathodic protection. PTFE coatings havelow friction coefficient and the torque has to be applied accord-ingly.


B 700 Welding consumables (informative)701 Requirements to welding, except for pipe mill manufac-turing welds, are covered in Appendix C. Requirements thatare specific for pipeline installation welding are given inSec.10. Below is provided guidance regarding the influence ofweld metal strength on allowable defect size as determined byECA (if applicable).702 The requirement for welds to have strength level equalto or higher than (overmatching properties) the base material isto minimise deformation in the area adjacent to any possibledefects.703 For pipes exposed to global yielding, i.e. when girthwelds are exposed to strain εl,nom ≥ 0.4%, it is required to per-form an ECA according to Appendix A. The ECA generallyrequires that the weld metal yield stress is matching or over-matching the longitudinal yield stress of the pipe. Due to thescatter in the pipe material yield stress, it is normally requiredthat the yield stress of the weld metal is 120-150 MPa higherthan SMYS of the base material (depending on the SMYS). AnECA involving undermatching weld metal will require specialconsiderations, see Appendix A. Temperature effects 704 It must be noted that the reduction in yield stress at ele-vated temperature may be higher for the weld metal than thebase material. Hence, undermatching may be experienced forhigh operation temperatures (e.g. snaking scenario). This isparticularly relevant when welding clad or lined linepipe.Whenever such situations occur, it will be required to performtransverse all weld tensile testing of the weld metal and frac-ture toughness testing at the relevant temperature.

C. Materials SpecificationC 100 General101 Requirements to the manufacture of linepipe and pipe-line components are covered in Sec.7 and Sec.8, respectively.This includes requirements to all relevant manufacturing stepsfrom steel making to dispatch from the pipe mill or component

Table 6-1 Carbon and low alloy steel bolts and nuts for pressure bearing or main structural applicationsTemperature range (oC)

Bolt Nut Size range

-100 to + 400 ASTM A320, Grade L7 / L7M

ASTM A194, Grade 4/S¤

< 65 mm

-46 to + 400 ASTM A193, Grade B7/B7M

ASTM A194, Grade 2H

All

-100 to + 400 ASTM A320, Grade L43

ASTM A194, Grade 7

< 100 mm

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manufacturing facility, but excluding any permanent external/internal coating.

C 200 Linepipe specification201 A specification reflecting the results of the materialsselection according to this section and referring to Sec.7, shallbe prepared by the Purchaser. The specification shall state anyoptions, additional requirements to and/or deviations from thisstandard pertaining to materials, manufacture, fabrication andtesting of linepipe.202 The material specification may be a Material Data Sheetreferring to this standard.203 The materials specification shall as a minimum includethe following (as applicable):

— quantity (e.g., total mass or total length of pipe)— manufacturing process (see Sec.7 A300)— type of pipe (see Sec.7 A201)— SMYS— outside or inside diameter— wall thickness— if data of the wall thickness variation (tmax and tmin ) or the

standard deviation in wall thickness variation shall be sup-plied to facilitate girth welds AUT (see Appendix E,B107)

— length and type of length (random or approximate)— application of supplementary requirements (S, F, P, D or

U), see B102-B103— delivery condition (see Sec.7, Table 7-1 and H201-H202)— minimum design temperature— range of sizing ratio for cold-expanded pipe— chemical composition for wall thickness > 25 mm (appli-

cable to C-Mn steel pipe with delivery condition N or Q)— chemical composition for wall thickness > 35 mm (appli-

cable to C-Mn steel pipe with delivery condition M)— if additional tensile testing in the longitudinal direction

with stress strain curves shall be performed— if additional tensile testing of base material at other than

room temperature is required, define; temperature (e.g.maximum design temperature), acceptance criteria andfrequency of tests

— CVN test temperature for wall thickness > 40 mm— liner/cladding material (UNS number)— mechanical and corrosion properties of liner/cladding

material— “type” of seal weld for lined linepipe— thickness of carrier pipe and liner/cladding material— any project specific requirements to gripping force of lined

linepipe— if the ultrasonically lamination checked zone at the pipe

ends shall be wider than 50 mm— if diameter at pipe ends shall be measured as ID or OD— if pipes shall be supplied with other than square cut ends

(see Sec.7 B336)— if criteria for reduced hydrostatic test pressure, as given in

Sec.7 E105, is fulfilled, and if it may be applied— if the outside weld bead shall be ground flush at least 250

mm from each pipe end to facilitate girth welds AUT (seeSec.7 B338)

— if inside machining of pipe ends is applicable, and the dis-tance from pipe end to tapered portion (see Sec.7 B339,and Appendix E, B108)

— if pipes shall be supplied with bevel protectors, and in caseof what type (see Sec.7 H300)

— if weldability testing is required— if qualification testing shall be conducted after the pipe

material has been heated to the expected coating tempera-ture when fusion bonded epoxy is used (see B406-B407)

— application of the alternative weld cap hardness of C-Mnsteel pipe according to supplementary requirement S (seeSec.7 I107)

— if SSC testing shall be performed during MPQT for pipes

conforming to supplementary requirement S— if supplementary requirement P apply, the relevant strain-

ing for the installation process, possible corrective actions(e.g. “reel on and reel off twice”) and post installation con-ditions/operations introducing plastic deformation shall bespecified.

C 300 Components specification 301 A specification reflecting the results of the materialsselection according to this section and referring to Sec.8, shallbe prepared by the Purchaser. The specification shall state anyoptions, additional requirements to and/or deviations from thisstandard pertaining to materials, manufacture, fabrication andtesting of the components.302 The materials specification shall as a minimum includethe following (as applicable):

— quantity (i.e the total number of components of each typeand size)

— design standard— required design life— material type, delivery condition, chemical composition

and mechanical properties at design temperature— nominal diameters, OD or ID, out of roundness and wall

thickness for adjoining pipes including required tolerances— bend radius, see Sec.8 B413— type of component, piggable or not piggable— gauging requirements, see Sec.10 O408— minimum design temperature (local)— maximum design temperature (local)— design pressure (local)— water depth— pipeline operating conditions including fluid characteris-

tics— details of field environmental conditions— external loads and moments that will be transferred to the

component from the connecting pipeline under installationand operation and any environmental loads

— functional requirements— material specification including, material type, delivery

condition, chemical composition and mechanical proper-ties at design temperature

— required testing— required weld overlay, corrosion resistant or hardfacing— if pup pieces of the linepipe material shall be fitted— coating/painting requirements.

C 400 Specification of bolts and nuts401 Bolts and nuts shall be supplied with certificates to EN10204 Type 3.1.402 Bolts and nuts for pressure containing and main struc-tural applications should be specified to have rolled threads. 403 Any coating of bolts shall be specified in the purchasedocument for bolting. In order to prevent hydrogen embrittle-ment of acid cleaned and/or electrolytically plated bolts andnuts, baking at 200°C for a minimum of 2 hours shall be spec-ified.

C 500 Coating specification501 As a part of detailed design, project specific require-ments to as-applied coating properties and to quality control ofthe manufacture of coating materials and of coating applica-tion (including risers, see D600) shall be defined in a purchasespecification for the applicable coating. DNV-RP-F102 andDNV-RP-F106 give detailed requirements and recommenda-tions to manufacture of field joint and linepipe coatings,respectively with emphasis of quality control of the applicationprocedure.502 The specification of linepipe coating, field joint coatingand any weight coating shall include requirements to the qual-

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ification of coating materials, coating application and repairprocedures, dimensions of the linepipe cut-back (including tol-erances) and to documentation of inspection and testing. Moredetailed requirements to the specification of pipeline coatingare contained in Sec. 9.

Guidance note:Cut-backs shall be defined to accommodate any AUT equipment


503 For pipeline components in CRA materials to receiveCP, detailed coating specifications shall be prepared with a pri-mary objective to prevent HISC.

C 600 Galvanic anodes specification601 As a part of design, specifications for manufacture andinstallation of galvanic anodes shall be prepared. These docu-ments shall define requirements to materials, properties ofanodes (as manufactured and as-installed, respectively) andassociated quality control. Detailed requirements are given inSec.9.

D. Corrosion Control

D 100 General101 All components of a pipeline system shall have adequatecorrosion control to avoid failures caused or initiated by corro-sion, both externally and internally.

Guidance note:Any corrosion damage may take the form of a more or less uni-form reduction of pipe wall thickness, but scattered pitting andgrooving corrosion oriented longitudinally or transversally to thepipe axis is more typical. Stress corrosion cracking is anotherform of damage. Uniform corrosion and corrosion grooving mayinteract with internal pressure or external operational loads, caus-ing rupture by plastic collapse or brittle fracture. Discrete pittingattacks are more likely to cause a pinhole leakage once the fullpipe wall has been penetrated


102 Pipeline systems may be exposed to a corrosive environ-ment both internally and externally. Options for corrosion mit-igation include use of corrosion protective coatings andlinings, cathodic protection (externally only), and chemicaltreatment or processing (internally only).

D 200 Corrosion allowance201 For submarine pipeline systems a corrosion allowancemay serve to compensate for internal and/or external corrosionand is mostly applied for control of internal or external pres-sure. For C-Mn steel components, a corrosion allowance maybe applied either alone or in addition to some system for cor-rosion mitigation.

Guidance note:A requirement for wall thickness determined by installationforces and exceeding that needed for pressure containment at theinitial design pressure, or wall thickness not needed for pressurecontainment due to a later down rating of operational pressurecan be utilised for corrosion control but is not referred to in thisdocument as a “corrosion allowance”A corrosion allowance is primarily used to compensate for formsof corrosion attack affecting the pipeline's pressure containmentresistance, i.e. uniform attack and, to a lesser extent, corrosiondamage as grooves or patches. Still, a corrosion allowance mayalso enhance the operational reliability and increase the usefullife if corrosion damage occurs as isolated pits; although suchdamage is unlikely to affect the pipeline's resistance, it will causea pinhole leak when the full wall thickness is penetrated. How-

ever, the extra wall thickness will then only delay leakage in pro-portion to the increase in wall thickness.


202 The needs for, and benefits of, corrosion allowance shallbe evaluated, taking into account the following factors as aminimum:

— design life and potential corrosivity of fluid and/or exter-nal environment

— expected form of corrosion damage (see Guidance noteabove)

— expected reliability of planned techniques and proceduresfor corrosion mitigation (e.g. chemical treatment of fluid,external coating, etc.)

— expected sensitivity and damage sizing capability of rele-vant tools for integrity monitoring, time to first inspectionand planned frequency of inspection

— consequences of sudden leakage, requirements to safetyand reliability

— any extra wall thickness applied during design for installa-tion forces and not needed for control of internal and exter-nal pressure

— any potential for down-rating (or up-rating) of operatingpressure.

203 An internal corrosion allowance of minimum 3 mm isrecommended for C-Mn steel pipelines of safety class Mediumand High carrying hydrocarbon fluids likely to contain liquidwater during normal operation. For nominally dry gas and forother fluids considered as non-corrosive, no corrosion allow-ance is required.204 An external corrosion allowance of minimum 3 mm isrecommended for C-Mn steel risers of safety class Mediumand High in the splash zone. An external corrosion allowanceshall further be considered for any landfalls. For risers carryinghot fluids (> 10oC above normal ambient seawater tempera-ture), a higher corrosion allowance should be considered, atleast for the splash zone (see E205). Any allowance for internalcorrosion shall be additional.

D 300 Temporary corrosion protection301 The need for temporary corrosion protection of externaland internal surfaces during storage and transportation shall beconsidered during design/engineering for later inclusion infabrication and installation specifications. Optional techniquesinclude end caps or bevel protectors, temporary thin film coat-ing and rust protective oil/wax.

Guidance note:Outdoor storage of unprotected pipes for a period of up to abouta year will not normally cause any significant loss of wall thick-ness. However, surface rusting may cause increased surfaceroughness affecting pipeline coating operations. Conditions forstorage should be such that water will not accumulate internally,or externally at any supports. End caps may retain water inter-nally if damaged or lost at one end, allowing entry of rain wateror condensation. Use of temporary coatings may interfere withlater external/internal coating.


302 The needs for corrosion protection during flooding shallbe assessed for inclusion in installation specifications. Specialprecautions are required to avoid corrosion damage to CRApipelines during system pressure testing using seawater. Type13Cr linepipe may suffer superficial corrosion attack duringoutdoor storage.

Guidance note:The use of a biocide for treatment of water for flooding is mostessential (even with short duration) as incipient bacterial growthestablished during flooding may proceed during operation andcause corrosion damage (pipelines for dry gas are excluded). Foruncoated C-Mn steel pipelines, an oxygen scavenger may be

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omitted since oxygen dissolved in seawater will become rapidlyconsumed by uniform corrosion without causing significant lossof wall thickness. Film forming or "passivating" corrosion inhib-itors are not actually required and may even be harmful. Type13Cr steel is highly susceptible to damage by raw seawater ormarginally treated seawater even at a short exposure period. Useof fresh water should be considered or seawater treated to a pHof 9 minimum.


D 400 External pipeline coatings (informative)401 “Linepipe coating” (also referred to as “factory coatingor “parent coating”) refers to factory applied external coatingsystems (mostly multiple-layer, with a total thickness of somemillimetres) with a corrosion protection function, either aloneor in combination with a thermal insulation function. Somecoating systems may further include an outer layer for mechan-ical protection, primarily during laying and any rock dumpingor trenching operations. Concrete coating for anti-buoyancy(weight coating, see Sec.9 C) is, however, not covered by theterm linepipe coating.402 “Field joint coating” (FJC) refers to single or multiplelayers of coating applied to protect girth welds and the associ-ated cut-back of the linepipe coating, irrespective of whethersuch coating is actually applied in the field or in a factory (e.g.pipelines for reel laying and prefabricated risers). “Coatingfield repairs” refers to repairs of factory coating performed inthe field (typically by the FJC contractor).403 The linepipe (external) coating system should beselected based on consideration of the following major items:

— general corrosion-protective properties dictated by perme-ability for water, dissolved gases and salts, adhesion, free-dom from pores, etc.

— resistance to physical, chemical and biological degrada-tion leading to e.g. cracking or disbondment, primarily inservice but also during storage prior to installation (tem-perature range and design life are decisive parameters)

— requirements for mechanical properties, primarily thoserelated to adhesion and flexibility, during installation(min. temperature) and operation (max. temperature)

— coating system’s compatibility with specific fabricationand installation procedures, including field joint coating)and coating field repairs

— coating systems compatibility with concrete weight coat-ing (see Sec.9 C), if applicable

— coating system’s compatibility with CP, and capability ofreducing current demand for CP, if applicable

— linepipe material’s compatibility with CP considering sus-ceptibility to HISC; see B303

— linepipe material’s susceptibility to corrosion in the actualenvironment, including stress corrosion cracking in theatmospheric zone and any onshore buried zone

— environmental compatibility and health hazards duringcoating application, fabrication/installation and operation.

404 For thermally insulating coatings, properties related toflow assurance also apply; e.g. specific heat capacity, thermalconductivity and the degradation of such properties by highoperating external pressure and internal fluid temperature.405 Pipeline components should have external coatings pref-erably matching the properties of those to be used for linepipe.If this is not practical, CP design may compensate for inferiorproperties. However, risks associated with HISC by CP shallbe duly considered (see B303 and E502 Guidance note).406 For the selection of FJC, the same considerations as forpipeline and riser coatings as in E403 and E605-E606 apply. Inaddition, sufficient time for application and cooling or curing

is crucial during barge laying of pipelines.407 For pipes with a weight coating or thermally insulatedcoating, the field joint coating (FJC) is typically made up of aninner corrosion protective coating and an in-fill. The objectiveof the in-fill is to provide a smooth transition to the pipelinecoating and mechanical protection to the inner coating. Forthermally insulated pipelines and risers, requirements for ade-quate insulating properties may also apply. The requirementsand guidelines to FJC are also applicable to any field repairs offactory coating408 The design and quality control of field joint coatings isessential to the integrity of pipelines in HISC susceptible mate-rials, including ferritic-austenitic (duplex) and martensiticstainless steel. Compliance with DNV-RP-F102 is recom-mended.

D 500 Cathodic Protection501 Pipelines and risers in the submerged zone shall be fur-nished with a cathodic protection (CP) system to provide ade-quate corrosion protection for any defects occurring duringcoating application (including field joints), and also for subse-quent damage to the coating during installation and operation.The design of submarine pipeline CP systems shall meet theminimum requirements in ISO15589-2. DNV-RP-F103 isbased on this standard, giving amendments and guidelines.

Guidance note:CP may be achieved using either galvanic ("sacrificial") anodes,or impressed current from a rectifier. Galvanic anodes are nor-mally preferred.


502 The CP systems should be capable of suppressing thepipe-to-seawater (or pipe-to-sediment) electrochemical poten-tial into the range -0.80 to -1.15 V rel. Ag/AgCl/ seawater. Aless negative potential may be specified for pipelines in CRAmaterials.

Guidance note:Potentials more negative than -1.15 V rel. Ag/AgCl/ seawatercan be achieved using impressed current. Such potentials maycause detrimental secondary effects, including coating disbond-ment and HISC of linepipe materials and welds. Pipeline systemcomponents in high-strength steel, and particularly in martensiticor ferritic-austenitic (‘duplex’) stainless steel, subject to highlocal stresses during subsea installation activities (e.g. pre-com-missioning) or operation can suffer HISC by CP, also within thepotential range given above. Such damage is primarily to beavoided by restricting straining subsea by design measures. Inaddition, special emphasis should be laid on ensuring adequatecoating of components that may be subject to localised straining.It is essential that the coating systems to be applied (i.e. factoryapplied coating and field joint coating) for materials that areknown to be susceptible to HISC have adequate resistance to dis-bonding by mechanical effects during installation as well aschemical/physical effects during operation. Overlay welding ofcritical areas with austenitic CRA filler materials may be consid-ered when organic coatings are not applicable. Thermallysprayed aluminium coating has also been applied for this pur-pose. Other measures to reduce or eliminate the risk of HISCinclude control of galvanic anodes by diodes and use of specialanode alloys with less negative closed circuit potential. (Thesetechniques require that the pipeline is electrically insulated fromconventional CP systems on electrically connected structures). Incase conventional bracelet anodes are still to be used, welding ofanodes to any pressure containing components in these materialsshould be avoided.


503 Galvanic anode CP systems should be designed to pro-vide corrosion protection throughout the design life of the pro-tected object.

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Guidance note:As retrofitting of galvanic anodes is generally costly (if practicalat all), the likelihood of the initial pipeline design life beingextended should be duly considered.


504 Pipeline systems connected to other offshore installa-tions shall have compatible CP systems unless an electricallyinsulating joint is to be installed. At any landfall of an offshorepipeline with galvanic anodes and impressed current CP of theonshore section, the needs for an insulating joint shall be eval-uated.

Guidance note:Without insulating joints, some interaction with the CP system ofelectrically connected offshore structures cannot be avoided. Asthe design parameters for subsea pipelines are typically moreconservative than that of other structures, some current drainfrom riser and from pipeline anodes adjacent to the pipeline can-not be avoided, sometimes leading to premature consumption.When the structure has a correctly designed CP system such cur-rent drain is not critical as the net current drain will decrease withtime and ultimately cease; i.e. unless the second structure hasinsufficient CP.


505 Unless otherwise specified by or agreed with the owner,pipelines shall be designed with a self-sustaining CP systembased on bracelet anodes installed with a maximum distance of300 m (in accordance with ISO 15589-2) and with electricalconnections to the pipeline by pin brazing or aluminothermicwelding of cable connections to the pipe wall. (see Appendix CE500).For shorter pipelines (up to 30 km approximately), CP may beachieved by anodes installed on structures at the end of thepipeline (e.g. platform sub-structure, subsea template or riserbase) electrically connected to the pipeline. This conceptrequires, however, that the design and quality control of fac-tory applied coatings, field joint coatings and coating fieldrepairs are closely defined (e.g. as in DNV-RP-F106 andDNV-RP-F102). A recommended procedure to calculate theprotective length of anodes on an adjacent structure is given inDNV-RP-F103 (ISO 15589-2 gives an alternative procedurebut, contrary to DNV-RP-F103, does not define the primaryparameters to be used for calculation of the protective length).

Guidance note:CP by anodes located on adjacent structures significantly reducesthe cost of anode installation in case the pipeline installation con-cept would otherwise require anode installation offshore. More-over, for buried pipelines in general and for hot buried lines inparticular, the anode electrochemical efficiency and current out-put capacity increases since anodes are located boldly exposed toseawater. The condition of such anodes can also be monitored.The concept of basing pipeline CP on anodes installed on adja-cent structures further reduces the risk of HISC damage to pipe-lines in susceptible materials (e.g. martensitic and ferritic-austenitic stainless steels).


506 Bracelet pipeline anodes are to be designed with dueconsiderations of forces induced during pipeline installation.For anodes to be installed on top of the pipeline coating, thismay require use of bolts for tensioning or welding of anodetabs with pressure applied on the bracelet assembly. Connectorcables shall be adequately protected; e.g. by locating the cablesto the gap between the anode bracelets and filling with amoulding compound.507 A calculation procedure for pipeline CP design usingconventional bracelet anodes and a maximum anode spacingof 300 m is given in ISO 15589-2 and in DNV-RP-F103. Thelatter document generally refers to ISO 15589-2 for designparameters and design procedures to be used and recommendssome default values which represent minimum requirements

that do not need to be verified by special considerations andtesting. DNV-RP-F103 emphasizes the importance of coatingdesign and quality control of coating application when defin-ing the CP current reducing effects of such coatings. It furthercontains additional guidance to the CP design. For alternativedesign procedures, see E505 and E506 above.508 The detailed engineering documentation of galvanicanode CP systems shall contain the following:

— design premises, including design life and reference to rel-evant project specifications, codes and standards

— calculations of average and final current demands for indi-vidual sections of the pipeline

— calculations of total anode net mass for the individual sec-tions, to meet the mean current demand

— calculation of final current anode output to verify that thefinal current demand can be met for the individual sectionsof the pipeline (applies to a conventional bracelet anodeconcept with max. 300 m anode spacing)

— number of bracelet anodes for the individual pipeline sec-tions, and resulting net anode mass to be installed on eachsection

— outline drawing(s) of bracelet anodes with fasteningdevices and including tentative tolerances

— calculations of pipeline metallic resistance to verify thefeasibility of CP by anodes on adjacent structure(s) or abracelet anode concept exceeding a spacing of 300 m incase any of these options apply (see DNV-RP-F103)

— documentation of CP capacity on adjacent installation(s)to be utilized for CP of pipeline, if applicable.

Guidance note:The above requirements for documentation of CP design is anamendment to ISO 15589-2


509 For CP design of pipeline system components withmajor surfaces in structural steel (e.g. riser bases), reference ismade to DNV-RP-B401.510 Design of any impressed current CP systems installed atland falls shall comply with ISO 15589-1. Requirements toelectrically insulating joints are given in Sec.8 B800.

Guidance note:Design of impressed current CP systems at landfalls is not cov-ered by this standard. Some general guidance is given in ISO15889.


D 600 External corrosion control of risers (informative)601 For a specific riser, the division into corrosion protectionzones is dependent on the particular riser or platform designand the prevailing environmental conditions. The upper andlower limits of the ‘splash zone’ may be determined accordingto the definitions in Sec.1.602 Adverse corrosive conditions occur in the zone abovelowest astronomical tide (LAT) where the riser is intermit-tently wetted by waves, tide and sea spray (‘splash zone’).Particularly severe corrosive conditions apply to risers heatedby an internal fluid. In the splash zone, the riser coating maybe exposed to mechanical damage by surface vessels andmarine operations, whilst there is limited accessibility forinspection and maintenance.603 The riser section in the ‘atmospheric zone’ (i.e. abovethe splash zone) is more shielded from both severe weatheringand mechanical damage. Furthermore, there is better accessi-bility for inspection and maintenance.604 In the ‘submerged zone’ and in the splash zone belowthe lowest astronomical tide (LAT), an adequately designed

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CP system is capable of preventing corrosion at any damagedareas of the riser coating. In the tidal zone, a CP system will bemarginally effective.605 Different coating systems may be applied in the threecorrosion protection zones defined above, provided they arecompatible. The considerations according to a), b), c), f), g)and h) in D403 above apply for all of the three zones. Fasteningdevices for risers are normally selected to be compatible witha specific riser coating rather than vice versa.606 The following additional considerations affecting selec-tion of coating system apply in the splash and atmosphericzones:

— resistance to under-rusting at coating defects— maintainability— compatibility with inspection procedures for internal and/

or external corrosion— compatibility with equipment/procedures for removal of

biofouling (if applicable)— fire protection (if required).

607 External cladding with certain Cu-base alloys may beused for combined corrosion protection and anti-fouling, pri-marily in the transition of the splash zone and the submergedzone (see D602). However, metallic materials with anti-foul-ing properties must be electrically insulated from the CP sys-tem to be effective. Multiple-layer paint coatings andthermally sprayed aluminium coatings are applicable to theatmospheric and submerged zones, and in the splash zone iffunctional requirements and local conditions permit.608 Mechanical and physical coating properties listed inD403 are also relevant for riser coatings, dependent on the par-ticular corrosion protection zone. The applicable requirementsto properties for each coating system and for quality controlshall be defined in a purchase specification. The generalrequirements and guidelines for quality control in DNV-RP-F106 are applicable. Some of the coating systems with func-tional requirements defined in coating data sheets are applica-ble also as riser coatings.609 In the submerged zone, the considerations for selectionof coating in D403 apply. In addition, resistance to biofoulingis relevant in surface waters of the submerged zone and thelowermost section of the splash zone may have to be consid-ered.610 Riser FJC’s shall have properties matching the selectedpipe coating. In the splash zone, field joint coatings should beavoided unless it can be demonstrated that their corrosion pro-tection properties are closely equivalent to those of the adja-cent coating.

D 700 Internal corrosion control (informative)701 Options for internal corrosion control should be evalu-ated aiming for the most cost-effective solution meeting theoverall requirements of safety and environmental regula-tions.The selection of the most cost-effective strategy for cor-rosion control requires that all major costs associated withoperation of the pipeline system, as well as investment costsfor corrosion control, are evaluated ("Life Cycle Cost Analy-sis"). When fluid corrosivity and efficiency of corrosion miti-gation cannot be assessed with any high degree of accuracy, a"risk cost" may be added for a specific option being evaluated.The risk cost is the product of estimated probability and conse-quences (expressed in monetary units) of a particular failuremode (e.g. rupture or pinhole leakage). The probability of suchfailures should reflect the designer's confidence in estimatingthe fluid corrosivity and the efficiency of options for corrosioncontrol being evaluated. Depending on the failure mode, con-sequences of failure may include costs associated withincreased maintenance, repairs, lost capacity and secondarydamage to life, environment and other investments.

702 The selection of a system for internal corrosion protec-tion of pipelines and risers has a major effect on detaileddesign and must therefore be evaluated during conceptualdesign. The following options for corrosion control may beconsidered:

a) processing of fluid for removal of liquid water and/or cor-rosive agents.

b) use of linepipe or internal (metallic) lining/cladding withintrinsic corrosion resistance (see B300).

c) use of organic corrosion protective coatings or linings(normally in combination with a) or d)).

d) chemical treatment, i.e. addition of chemicals with corro-sion mitigating function.

In addition, the benefits of a corrosion allowance (see D200)should be duly considered for a) and d).703 Corrosion control by fluid processing may involveremoval of water from gas/oil (dehydration), or of oxygenfrom seawater for injection (deoxygenation), for example.Consequences of operational upsets on material degradationshould be taken into account. The necessity for corrosionallowance and redundant systems for fluid processing shouldbe considered. On-line monitoring of fluid corrosion proper-ties downstream of processing unit is normally required. Foroil export pipelines carrying residual amounts of water, a bio-cide treatment should be considered as a back up for preven-tion of bacterial corrosion. Periodic pigging for removal ofwater and deposits counteracts internal corrosion in generaland bacterial corrosion in particular.704 If internal coatings or linings are to be evaluated as anoption for corrosion control, the following main parametersshall be considered:

— chemical compatibility with all fluids to be conveyed orcontacted during installation, commissioning and opera-tion, including the effects of any additives for control offlow or internal corrosion (see D706)

— resistance to erosion by fluid and mechanical damage bypigging operations

— resistance to rapid decompression— reliability of quality control during coating application— reliability of (internal) field joint coating systems, if appli-

cable— consequences of failure and redundant techniques for cor-

rosion mitigation.

705 Internal coating of pipelines (e.g. by thin film of epoxy)has primarily been applied for the purpose of friction reductionin dry gas pipelines ("flow coatings" or “anti-friction coat-ings”). Any such coatings should have a minimum specifiedthickness of 40 μm and should comply with the minimumrequirements in API RP 5L2. Although such coatings can notbe expected to be efficient in preventing corrosion attack ifcorrosive fluids are conveyed, any coating with adequate prop-erties may still be beneficial in reducing forms of attack affect-ing membrane stresses and hence, the pressure retainingcapacity of the pipeline.706 Chemical treatment of fluids for corrosion control mayinclude:

— corrosion inhibitors (e.g. "film forming")— pH-buffering chemicals— biocides (for mitigation of bacterial corrosion)— glycol or methanol (added at high concentrations for

hydrate inhibition, diluting the water phase)— dispersants (for emulsification of water in oil)— scavengers (for removal of corrosive constituents at low

concentrations).

707 The reliability of chemical treatment should be evalu-

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ated in detail during the conceptual design. Important parame-ters to be considered are:

— anticipated corrosion mitigating efficiency for the actualfluid to be treated, including possible effects of scales,deposits, etc. associated with this fluid

— capability of the conveyed fluid to distribute inhibitor inthe pipeline system along its full length and circumference

— compatibility with all pipeline system and downstreammaterials, particularly elastomers and organic coatings

— compatibility with any other additives to be injected,— health hazards and environmental compatibility— provisions for injection and techniques/procedures for

monitoring of inhibitor efficiency

— consequences of failure to achieve adequate protection,and redundant techniques.

For pipelines carrying untreated well fluid or other fluids withhigh corrosivity and with high requirements to safety and reli-ability, there is a need to verify the efficiency of chemical treat-ment by integrity monitoring using a tool allowing wallthickness measurements along the full length of the pipeline(see Sec.12). Corrosion probes and monitored spools are pri-marily for detection of changes in fluid corrosivity and are notapplicable for verification of the integrity of the pipeline.

DET NORSKE VERITAS


SECTION 7CONSTRUCTION – LINEPIPE

A. GeneralA 100 Objective101 This section specifies the requirements for, manufac-ture, testing and documentation of linepipe. All mechanicalproperties and dimensional tolerances shall be met after heattreatment, expansion and final shaping.102 Materials selection shall be performed in accordancewith Sec.6.103 This section does not cover any activities taking partafter the pipes have been dispatched from the pipe mill, e.g.girth welding and coating.104 The requirements stated herein for Carbon-Manganese(C-Mn) steel linepipe conform in general to ISO 3183 AnnexJ: “PSL 2 pipe ordered for offshore service”, with some addi-tional and modified requirements.105 Manufacturers of linepipe shall have an implementedquality assurance system according to ISO 9001.

A 200 Application201 The requirements are applicable for linepipe made of:

— C-Mn steel— clad or lined steel— corrosion resistant alloys (CRA) including ferritic - auste-

nitic (duplex) stainless steel, austenitic stainless steels,martensitic stainless steels (13Cr), other stainless steelsand nickel based alloys.

202 Materials, manufacturing methods and procedures thatcomply with recognised practices or proprietary specificationswill normally be acceptable provided they comply with therequirements of this section.

A 300 Process of manufacture301 C-Mn linepipe shall be manufactured according to oneof the following processes:Seamless (SMLS)Pipe manufactured by a hot forming process without welding.In order to obtain the required dimensions, the hot formingmay be followed by sizing or cold finishing.High Frequency Welded (HFW)Pipe formed from strip and welded with one longitudinal seamformed by electric-resistance welding applied by induction orconduction with a welding current frequency ≥70 kHz, withoutthe use of filler metal. The forming may be followed by coldexpansion or reduction.Submerged Arc-Welded (SAW)Pipe manufactured by forming from strip or plate and with onelongitudinal (SAWL) or helical (SAWH) seam formed by thesubmerged arc process, with at least one pass made on theinside and one pass from the outside of the pipe. The formingmay be followed by cold expansion or reduction.302 CRA linepipe may, in addition to SMLS and SAWL, bemanufactured according to one of the following processes:Electron Beam Welded (EBW) and Laser Beam Welded (LBW)Pipe formed from strip and welded with one longitudinal seam,with or without the use of filler metal. The forming may be fol-lowed by cold expansion or reduction to obtain the requireddimensional tolerances. These welding processes shall be sub-ject to pre-qualification testing according to Appendix C.

Multiple welding processes (MWP)Pipe formed from strip or plate and welded using a combina-tion of two or more welding processes. If the combination ofwelding processes has not been used previously, pre-qualifica-tion testing should be conducted according to Appendix C.303 The backing steel of lined linepipe shall comply withA301.304 The liner pipe of lined linepipe shall be manufactured inaccordance with API 5LC.305 Clad linepipe shall be manufactured from CRA clad C-Mn steel plate by application of a single longitudinal weld.With respect to the backing steel, the pipe manufacturing shallbe in general compliance with one of the manufacturing routesfor SAW pipe as given in Table 7-1. The longitudinal weldshall be MWP (see A302).

A 400 Supplementary requirements401 When requested by the Purchaser and stated in the mate-rials specification (as required in A500), linepipe to this stand-ard shall meet supplementary requirements given inSubsection I, for:

— sour service, suffix S (see I100)— fracture arrest properties, suffix F (see I200)— linepipe for plastic deformation, suffix P (see I300)— enhanced dimensional requirements for linepipe, suffix D

(see I400)— high utilisation, suffix U (see I500).

A 500 Linepipe specification 501 A linepipe specification reflecting the results of thematerials selection (see Sec.6 C200), referring to this section(Sec.7) of the offshore standard, shall be prepared by the Pur-chaser. The specification shall state any additional require-ments to and/or deviations from this standard pertaining tomaterials, manufacture, fabrication and testing of linepipe.

A 600 Manufacturing Procedure Specification and qualificationManufacturing Procedure Specification (MPS)601 Before production commences, the Manufacturer shallprepare a Manufacturing Procedure Specification (MPS). TheMPS shall demonstrate how the specified properties may beachieved and verified throughout the proposed manufacturingroute.The MPS shall address all factors that influence the quality andconsistency of the product. All main manufacturing steps fromcontrol of received raw material to shipment of finished pipe,including all examination and check points, shall be outlined indetail.References to the procedures established for the execution ofall the individual production steps shall be included.602 The MPS shall as a minimum contain the followinginformation (as applicable):

— steel producer— plan(s) and process flow description/diagram— project specific quality control plan— manufacturing process— target chemical composition— steel making and casting techniques— ladle treatments (secondary refining), degassing, details of

inclusion shape control, super heat

DET NORSKE VERITAS


— method used to ensure that sufficient amount of inter-mixed zones between different orders are removed

— details and follow-up of limiting macro, as well as microsegregation, e.g. soft reduction and electro magnetic stir-ring (EMS) used during continuous casting

— manufacturer and manufacturing location of raw materialand/or plate for welded pipes

— billets reheating temperature for seamless— allowable variation in slab reheating temperature, and start

and stop temperatures for finishing mill and acceleratedcooling

— methods for controlling the hydrogen level (e.g. stackingof slabs or plates)

— pipe-forming procedure, including preparation of edgesand control of alignment and shape (including width ofstrip for HFW)

— procedure for handling of welding consumable and flux— all activities related to production and repair welding,

including welding procedures and qualification— heat treatment procedures (including in-line heat treat-

ment of the weld seam) including allowable variation inprocess parameters

— method for cold expansion/reduction/sizing/finishing, tar-get and maximum sizing ratio

— hydrostatic test procedures— NDT procedures (also for strip/plate as applicable)— list of specified mechanical and corrosion testing— dimensional control procedures— pipe number allocation— pipe tracking procedure (traceability procedure)— marking, coating and protection procedures— handling, loading and shipping procedures.

Manufacturing Procedure Qualification Test (MPQT)603 The MPS shall be qualified for each nominal pipe diam-eter as part of first day production, unless as allowed in A609.For C-Mn steels with SMYS ≤ 485 MPa that are not intendedfor sour service, relevant documentation may be agreed in lieuof qualification testing providing all essential variables inA609 are adhered to.604 Each MPQT shall include full qualification of one pipefrom two different test units (a total of two pipes). If the entireproduction is limited to one heat the MPQT may be performedon a single pipe from that heat. The minimum type and extentof chemical, mechanical, and non-destructive testing are givenin this section. This includes all stated production tests plusadditional tests given in Table 7-8, Table 7-13 and Table 7-15.605 For C-Mn steels with SMYS 485 MPa, the qualificationof the MPS shall be completed prior to start of production,unless otherwise agreed.

Guidance note:Depending on the criticality of the project, it is recommended forall projects to carefully evaluate if the MPQT should be con-ducted prior to the start of production.


606 If the cold forming of C-Mn steel exceeds 5% strain afterheat treatment then ageing tests shall be performed as part ofthe qualification testing. The tests shall be performed on theactual pipe without any straightening and additional deforma-tion, see Appendix B A1201. The absorbed Charpy V-notchimpact energy in the aged condition shall meet the require-ments in Table 7-5.607 Additional MPS qualification testing may be required byPurchaser (e.g. weldability testing, analysis for trace elementsfor steel made from scrap, etc.), as part of the qualification ofthe MPS (see A603).608 The validity of the MPQT shall be limited to the steel-making, rolling, and manufacturing/ fabrication facilities usedduring the qualification.

609 In addition to the requirements stated above, the follow-ing changes (as applicable) to the manufacturing processeswill require re-qualification of the MPS (essential variables):

— any change in steelmaking practice— changes beyond the allowable variation for rolling prac-

tice, accelerated cooling and/or QT process— change in nominal wall thickness exceeding + 5% to -10%— change in ladle analysis for C-Mn steels outside ± 0.02%

C, ± 0.02 CE and/or ± 0.03 in Pcm— any change in pipe forming process, — any change in alignment and joint design for welding— change in welding heat input ± 15%.

The following additional essential variable applies to HFW,EBW and LBW pipe:

— any change in nominal thickness— change in welding heat coefficient

Q = (amps × volts) / (travel speed × thickness) ± 5%— addition or deletion of an impeder— change in rollers position and strip width outside agreed

tolerances.

610 If one or more tests in the MPQT fail, the MPS shall bereviewed and modified accordingly, and a complete re-qualifica-tion performed. Re-testing may be allowed subject to agreement.

B. Carbon Manganese (C-Mn) Steel LinepipeB 100 General101 C-Mn steel linepipe fabricated according to this standardgenerally conform to the requirements in ISO 3183 Annex J:“PSL 2 pipe ordered for offshore service”. Any additional ormodified requirements to ISO 3183 Annex J are highlighted inthis subsection (B200-B600) as described in B102 and B103.Additional or modified requirements102 Paragraphs containing additional requirements to ISO3183 are marked at the end of the relevant paragraph with AR.Paragraphs containing requirements that are modified com-pared to ISO 3183 are marked at the end of the relevant para-graph with MR.103 Additional or modified requirements when given intables are marked in accordance with B102 with AR and MRin the relevant table cells as applicable.

B 200 Pipe designation 201 C-Mn steel linepipe shall be designated with:

— DNV— process of manufacture— SMYS— supplementary requirement suffix (see Subsection I), as

applicable. MR

Guidance note:e.g. "DNV SMLS 450 SF" designates a seamless pipe withSMYS 450 MPa, meeting the supplementary requirements forsour service and fracture arrest properties.


B 300 ManufacturingStarting material and steel making301 C-Mn steel linepipe shall be manufactured in accord-ance with the processes given in A300 using the starting mate-rials and corresponding forming methods and final heattreatment as given in Table 7-1.302 All manufacturing including steel making and the raw

DET NORSKE VERITAS


materials used shall be in accordance with the qualified MPS,follow the same activity sequence, and stay within the agreedallowable variations.303 All steels shall be made by an electric or one of the basicoxygen processes. C-Mn steel shall be fully killed and made toa fine grain practice.General requirements to manufacture of seamless pipe304 SMLS pipe shall be manufactured from continuously(strand) cast or ingot steel.305 If the process of cold finishing is used, this shall bestated in the inspection document.306 Pipe ends shall be cut back sufficiently after rolling toensure freedom from defects. ARGeneral requirements to manufacture of welded pipe307 Unless otherwise agreed, strip and plate used for themanufacture of welded pipe shall be rolled from continuously(strand) cast or pressure cast slabs. Strip or plate shall not con-tain any repair welds.308 The strip width for spiral welded pipes should not be lessthan 0.8 and not more than 3.0 times the pipe diameter. Stripand plate shall be inspected visually after rolling, either of theplate, of the uncoiled strip or of the coil edges.309 If agreed, strip and plate shall be inspected ultrasonicallyfor laminar imperfections or mechanical damage, either beforeor after cutting the strip or plate, or the completed pipe shall besubjected to full-body inspection, including ultrasonic inspec-tion, see Table 7-16.310 Plate or strip shall be cut to the required width and theweld bevel prepared by milling or other agreed methods beforeforming. AR311 Cold forming (i.e. below 250°C) of C-Mn steel shall notintroduce a plastic deformation exceeding 5%, unless heattreatment is performed or ageing tests show acceptable results(see A606). AR312 Normalising forming of materials and weldments shallbe performed as recommended by the Manufacturers of theplate/strip and welding consumables. AR313 Welding personnel for execution of all welding opera-tions shall be qualified by in-house training. The in-housetraining program shall available for review on request by Pur-chaser. AR314 Welding procedures for the seam weld shall be qualifiedas part of MPQT. AR315 The weld metal shall, as a minimum, have strength, duc-tility and toughness meeting the requirements of the base mate-rial. AR316 Welds containing defects may be locally repaired bywelding. Weld deposit having unacceptable mechanical prop-erties shall be completely removed before re-welding. AR317 Arc stops during welding shall be repaired according toa qualified welding repair procedure. AR318 Low hydrogen welding consumables shall be used andshall give a diffusible hydrogen content of maximum 5 ml/100 g weld metal. AR319 Welding consumables shall be individually marked andsupplied with an inspection certificate according to EN 10204.Welding wire shall be supplied with certificate type 3.1. whilecertificate type 2.2 is sufficient for SAW Flux. AR320 Handling of welding consumables and the execution andquality assurance of welding shall meet the requirements of in-house quality procedures. ARSAW pipe321 Any lubricant and contamination on the weld bevel orthe surrounding areas shall be removed before making the

seam welds of SAWL pipes or SAWH pipes.322 Tack welds shall be made by: manual or semi-automaticsubmerged-arc welding, electric welding, gas metal-arc weld-ing, flux-cored arc welding; or shielded metal-arc welding usinga low hydrogen electrode. Tack welds shall be melted and coa-lesced into the final weld seam or removed by machining.323 Intermittent tack welding of the SAWL groove shall notbe used unless Purchaser has approved data furnished by Man-ufacturer to demonstrate that all mechanical properties speci-fied for the pipe are obtainable at both the tack weld andintermediate positions.324 Unless comparative tests results of diffusible hydrogenversus flux moisture content are provided (meeting therequirement in B318), the maximum residual moisture contentof agglomerated flux shall be 0.03%.Repair welding of SAW seam welds325 Repair welding of SAW pipe seam welds shall be qual-ified in accordance with ISO3183 Annex D and be performedin accordance with ISO3183 Annex C.4. Any repair weldingshall be carried out prior to cold expansion.326 Acceptance criteria and test requirements for Charpy V-notch impact properties for qualification of repair welding pro-cedures shall be in accordance with B409 through 411. ARHFW pipe327 The abutting edges of the strip or plate should be milledor machined immediately before welding.328 The width of the strip or plate should be continuouslymonitored. AR329 The weld seam and the HAZ shall be fully normalizedsubsequent to welding. MRHeat treatment 330 Heat treatments of SMLS and welded pipe shall be per-formed according to documented procedures used duringMPQT.331 The documented procedures shall be in accordance withany recommendations from the material Manufacturer withregard to heating and cooling rates, soaking time, and soakingtemperature. ARCold expansion and cold sizing332 The extent of cold sizing and cold forming expressed asthe sizing ratio sr, shall be calculated according to the follow-ing formula:sr = (Da - Db) / Dbwhere

Da is the outside diameter after sizingDb is the outside diameter before sizing.333 The sizing ratio of cold expanded pipe should be withinthe range 0.003 < sr ≤ 0.015. Expansion shall not introducehigh local deformations.334 Pipes may be cold sized to their final dimensions byexpansion or reduction. This shall not produce excessive per-manent strain. The sizing ratio, sr , shall not exceed 0.015 if nosubsequent heat treatment or only heat treatment of the weldarea is performed.335 The sizing ratio, sr , for cold sizing of pipe ends shall notexceed 0.015 unless the entire pipe ends are subsequentlystress relieved.Finish of pipe ends336 Unless otherwise agreed, pipe ends shall be cut squareand be free from burrs. MR337 The internal weld bead shall be ground to a height of 0to 0.5 mm for a distance of at least 100 mm at both pipe ends.

DET NORSKE VERITAS


338 If agreed, the outside weld bead shall be ground to aheight of 0 to 0.5 mm for a distance of at least 250 mm at bothpipe ends. The transition to the base material/pipe body shallbe smooth and without a noticeable step. MR339 If agreed internal machining or grinding may be carriedout. In case of machining, the following requirements shall beadhered to:

— if required in the purchase order the internal taper shall belocated at a defined minimum distance from future bevelto facilitate UT or AUT

— the angle of the internal taper, measured from the longitu-dinal axis shall not exceed 7.0º for welded pipe. For SMLSpipe the maximum angle of the internal taper shall be asgiven in Table 7-2. MR

Jointers and strip end welds340 Jointers shall not be delivered unless otherwise agreed.341 If used, the jointer circumferential weld shall be quali-fied according to the requirements for pipeline girth weldsgiven in Appendix C. Production testing requirements forjointers shall be in accordance with ISO 3183. Other manufac-turing requirements shall comply with Annex A of ISO 3183.342 Apart from linepipe supplied as coiled tubing, strip /plate end welds shall not be permitted unless otherwise agreed.MR343 If used, see B341, strip / plate end welds shall complywith all applicable requirements in ISO 3183.

Re-processing344 In case any mechanical tests fail during production ofQT or normalised pipe material, it is acceptable to conduct onere-heat treatment cycle of the entire test unit. All mechanicaltesting shall be repeated after re-heat treatment. ARTraceability345 A system for traceability of the heat number, heat treat-ment batch and test unit number and the records from allrequired tests to each individual pipe shall be established anddescribed in the MPS (see A602). Required repairs and recordsof dimensional testing and all other required inspections shallbe included. Care shall be exercised during storage and han-dling to preserve the identification of materials. MR

B 400 Acceptance criteriaChemical composition401 The chemical compositions given in Table 7-3 are appli-cable to pipes with delivery condition N or Q (normalised orquenched and tempered according to Table 7-1), with nominalwall thickness t ≤ 25 mm.402 The chemical compositions given in Table 7-4 are appli-cable to pipes with delivery condition M (thermo-mechanicalformed or rolled according to Table 7-1). The chemical com-positions given in Table 7-4 are applicable for pipes with t ≤ 35mm. MR403 For pipes with nominal wall thickness larger than thelimits indicated in B401 and B402, the chemical compositionshall be subject to agreement.404 For pipe with a carbon content ≤ 0.12% (product analy-sis), carbon equivalents shall be determined using the Pcm for-mula as given in Table 7-3 and Table 7-4. If the heat analysisfor boron is less than 0.0005%, then it is not necessary for theproduct analysis to include boron, and the boron content maybe considered to be zero for the Pcm calculation.405 For pipe with a carbon content > 0.12% (product analy-

Table 7-1 C-Mn steels, acceptable manufacturing routesType of pipe

Starting Material Pipe forming Final heat treatment Delivery condition 1)

SMLS Ingot, bloom or billet Normalising forming None NHot forming Normalising or QT 1) N or QHot forming and cold finishing N or Q

HFW Normalising rolled strip Cold forming Normalising of weld area NThermo-mechanical rolled strip Heat treating of weld area M

Heat treating of weld area and stress relieving of entire pipe

M

Hot rolled or normalising rolled strip Cold forming Normalising of entire pipe NQT 2) of entire pipe Q

Cold forming and hot reduction under controlled temperature, resulting in a normalised condition

None N

Cold forming followed by thermome-chanical forming of pipe

M

SAW Normalised or normalising rolled plate or strip

Cold forming None, unless required due to degree of cold forming

N

Thermo-mechanical rolled plate or strip MQT 2) plate or strip QAs-rolled, QT 2), normalised or normalis-ing rolled plate or strip

Normalising forming None N

Cold forming Normalising NQT 1) Q

Notes

1) The delivery conditions are: “Normalised” denoted N, “Quenched and tempered”, denoted Q, and “Thermomechanical rolled or formed”, denoted M.2) Quenched and Tempered.

Table 7-2 Maximum angle of internal taper for SMLS pipeWall thickness t [mm] Max. angle of taper [°]

< 10.5 7.010.5 ≤ t < 14.0 9.514.0 ≤ t < 17.0 11.0

≥ 17.0 14.0

DET NORSKE VERITAS


sis) carbon equivalents shall be determined using the CE for-mula as given in Table 7-3.Tensile properties406 The tensile properties shall be as given in Table 7-5.407 For transverse weld tensile testing, the fracture shall notbe located in the weld metal. The ultimate tensile strength shallbe at least equal to the SMTS.Hardness408 The hardness in the Base Material (BM), Weld Metal(WM) and the Heat Affected Zone (HAZ) shall comply withTable 7-5. ARCVN impact test409 Requirements for Charpy V-notch impact properties forlinepipe BM, WM and HAZ are given in Table 7-5. The valuesin Table 7-5 shall be met when tested at the temperatures givenin Table 7-6. MR410 Testing of Charpy V-notch impact properties shall, ingeneral, be performed on test specimens 10 × 10 mm. Wheretest pieces of width < 10 mm are used, the measured averageimpact energy (KVm) and the test piece cross-section meas-ured under the notch (A) (mm2) shall be reported. For compar-ison with the values in Table 7-5, the measured energy shall beconverted to the impact energy (KV) in Joules using the for-mula:

AR

411 From the set of three Charpy V-notch specimens, onlyone is allowed to be below the specified average value andshall meet the minimum single value requirement. ARFlattening test412 For HFW pipe with SMYS ≥ 415 MPa with wallthickness ≥ 12.7 mm, there shall be no opening of the weldbefore the distance between the plates is less than 66% of theoriginal outside diameter. For all other combinations of pipegrade and specified wall thickness, there shall be no opening ofthe weld before the distance between the plates is less than50% of the original outside diameter.413 For HFW pipe with a D/t > 10, there shall be no cracksor breaks other than in the weld before the distance betweenthe plates is less than 33% of the original outside diameter.

Guidance note:The weld extends to a distance, on each side of the weld line, of6.4 mm for D < 60.3 mm, and 13 mm for D ≥ 60.3 mm.


Guided-bend test414 The guided-bend test pieces shall not:

— fracture completely— reveal any cracks or ruptures in the weld metal longer than

3.2 mm, regardless of depth, or— reveal any cracks or ruptures in the parent metal, HAZ, or

fusion line longer than 3.2 mm or deeper than 12.5% of thespecified wall thickness.

However, cracks that occur at the edges of the test piece duringtesting shall not be cause for rejection, provided that they arenot longer than 6.4 mm.

(7.1)KV

8 10 KVm××A

---------------------------------=

Table 7-3 Chemical composition for C-Mn steel pipe with delivery condition N or Q, applicable for seamless and welded pipe.

SMYSProduct analysis, maximum. wt.% Carbon

equivalentsC1) Si Mn 1) P S V Nb Ti Other 2) CE 3) Pcm

4)

Pipe with delivery condition N (normalised according to Table 7-1)245 0.14 0.40 1.35 0.020 0.010 Note 5) Note 5) 0.04 Notes 6,7) 0.36 0.19 8)

290 0.14 0.40 1.35 0.020 0.010 0.05 0.05 0.04 Note 7) 0.36 0.19 8)

320 0.14 0.40 1.40 0.020 0.010 0.07 0.05 0.04 Notes 6,7) 0.38 0.20 8)

360 0.16 0.45 1.65 0.020 0.010 0.10 0.05 0.04 Notes 6) 0.43 0.22 8)

Pipe with delivery condition Q (quenched and tempered according to Table 7-1)245 0.14 0.40 1.35 0.020 0.010 0.04 0.04 0.04 Note 7) 0.34 0.19 8)

290 0.14 0.40 1.35 0.020 0.010 0.04 0.04 0.04 Note 7) 0.34 0.19 8)

320 0.15 0.45 1.40 0.020 0.010 0.05 0.05 0.04 Note 7) 0.36 0.20 8)

360 0.16 0.45 1.65 0.020 0.010 0.07 0.05 0.04 Notes 6,9) 0.39 0.20 8)

390 0.16 0.45 1.65 0.020 0.010 0.07 0.05 0.04 Notes 6,9) 0.40 0.21 8)

415 0.16 0.45 1.65 0.020 0.010 0.08 0.05 0.04 Notes 6,9) 0.41 0.22 8)

450 0.16 0.45 1.65 0.020 0.010 0.09 0.05 0.06 Notes 6,9) 0.42 0.22 8)

485 0.17 0.45 1.75 0.020 0.010 0.10 0.05 0.06 Notes 6,9) 0.42 0.23 8)

555 0.17 0.45 1.85 0.020 0.010 0.10 0.06 0.06 Notes 6,9) As agreedNotes

1) For each reduction of 0.01% below the specified maximum for carbon, an increase of 0.05% above the specified maximum for manganese is permissible, up to a maximum increase of 0.20%.

2) Al total ≤ 0.060%; N ≤ 0.012%; Al/N ≥ 2:1 (not applicable to titanium-killed steel or titanium-treated steel).

3)4)

5) Unless otherwise agreed, the sum of the niobium and vanadium contents shall be ≤ 0.06%.6) The sum of the niobium, vanadium, and titanium contents shall be ≤ 0.15%.7) Cu ≤ 0.35%; Ni ≤ 0.30%; Cr ≤ 0.30%; Mo ≤ 0.10%; B ≤ 0.0005%.8) For SMLS pipe, the listed value is increased by 0.03, up to a maximum of 0.25.9) Cu ≤ 0.50%; Ni ≤ 0.50%; Cr ≤ 0.50%; Mo ≤ 0.50%; B ≤ 0.0005%.

( ) ( )15

CuNi5

VMoCr6

MnCCE ++

++++=

B510V

15Mo

20Cr

60Ni

20Cu

20Mn

30SiCPcm ++++++++=

DET NORSKE VERITAS


Table 7-4 Chemical composition for C-Mn steel pipe with delivery condition M (thermo-mechanical formed or rolled according to Table 7-1).

SMYSProduct analysis, maximum. wt.% Carbon equivalent

C1) Si Mn 1) P S V Nb Ti Other 2) Pcm 3)

245 0.12 0.40 1.25 0.020 0.010 0.04 0.04 0.04 Note 4) 0.19290 0.12 0.40 1.35 0.020 0.010 0.04 0.04 0.04 Note 4) 0.19320 0.12 0.45 1.35 0.020 0.010 0.05 0.05 0.04 Note 4) 0.20360 0.12 0.45 1.65 0.020 0.010 0.05 0.05 0.04 Notes 5,6) 0.20390 0.12 0.45 1.65 0.020 0.010 0.06 0.08 0.04 Notes 5,6) 0.21415 0.12 0.45 1.65 0.020 0.010 0.08 0.08 0.06 Notes 5,6) 0.21450 0.12 0.45 1.65 0.020 0.010 0.10 0.08 0.06 Notes 5,6) 0.22485 0.12 0.45 1.75 0.020 0.010 0.10 0.08 0.06 Notes 5,6) 0.22 7)

555 0.12 0.45 1.85 0.020 0.010 0.10 0.08 0.06 Notes 5,6) 0.24 7)

Notes


2) Al total ≤ 0.060%; N ≤ 0.012%; Al/N ≥ 2:1 (not applicable to titanium-killed steel or titanium-treated steel).

3)4) Cu ≤ 0.35%; Ni ≤ 0.30%; Cr ≤ 0.30%; Mo ≤ 0.10%; B ≤ 0.0005%.5) The sum of the niobium, vanadium, and titanium contents shall be ≤ 0.15%.6) Cu ≤ 0.50%; Ni ≤ 0.50%; Cr ≤ 0.50%; Mo ≤ 0.50%; B ≤ 0.0005%.7) For nominal wall thickness t > 25 mm the carbon equivalent may be increased with 0.01.

Table 7-5 C-Mn steel pipe, mechanical propertiesYield strength

Rt0,5[MPa]

Tensile strengthRm

[MPa]

RatioRt0,5/Rm

Elongation in 50.8 mm

Af[%]

Hardness[HV10]

Charpy V-notch energy (KVT) 1)

[J]BM, WM HAZ

SMYS min. max. min.2) max. max. min. max. average min.245 245 450 3) 415 760 0.93 Note 4) 270 300 27 22290 290 495 415 760 270 30 24320 320 520 435 760 270 32 27360 360 525 460 760 270 36 30390 390 540 490 760 270 39 33415 415 565 520 760 270 42 35450 450 570 535 760 270 45 38485 485 605 570 760 300 50 40555 555 675 625 825 300 56 45Notes

1) The required KVL (longitudinal direction specimens) values shall be 50% higher than the required KVT values.2) If tested in the longitudinal direction, a minimum tensile strength 5% less than the required value is acceptable.3) For pipe with specified outside diameter < 219.1 mm, the yield strength shall be ≤ 495 MPa.4) The specified minimum elongation Af , in 50.8 mm, expressed in percent, rounded to the nearest percent shall be as determined using

the following equation: where:

C is 1940 for calculations using SI units;AXC is the applicable tensile test piece cross-sectional area, as follows:- for round bar test pieces, 130 mm2 for 12.5 mm and 8.9 mm diameter test pieces; and 65 mm2 for 6.4 mm test pieces- for full-section test pieces, the lesser of a) 485 mm2 and b) the cross-sectional area of the test piece, calculated using the specified outside diameter and- the specified wall thickness of the pipe, rounded to the nearest 10 mm2- for strip test pieces, the lesser of a) 485 mm2 and b) the cross-sectional area of the test piece, calculated using the specified width of the test piece and

the specified wall thickness of the pipe, rounded to the nearest 10 mm2, andU is the specified minimum tensile strength, in MPa.

B510V

15Mo

20Cr

60Ni

20Cu

20Mn

30SiCPcm ++++++++=

9,0

2,0

UA

CA XCf =

DET NORSKE VERITAS


Fracture toughness of weld seam415 The measured fracture toughness shall as a minimumhave a CTOD value of 0.15 mm, when tested at the minimumdesign temperature. ARMacro examination of weld seam416 The macro section shall show a sound weld mergingsmoothly into the base material without weld defects accord-ing to Appendix D, Table D-4. For SAW pipe complete re-melting of tack welds shall be demonstrated. For MPQT weldsshall meet the requirements of ISO 5817 Quality level C. AR417 The alignment of internal and external seams of SAWpipes shall be verified on the macro section, unless alternativemethods with demonstrated capabilities are used.Metallographic examination of HFW pipe418 The metallographic examination shall be documentedby micrographs at sufficient magnification and resolution todemonstrate that no detrimental oxides from the welding proc-ess are present along the weld line. AR419 It shall be verified that the entire HAZ has been appro-priately heat treated over the full wall thickness and that nountempered martensite remains.Hydrostatic test420 The pipe shall withstand the hydrostatic test withoutleakage through the weld seam or the pipe body.421 Linepipe that fails the hydrostatic test shall be rejected.AR422 For pipe classified as coiled tubing, the hydrostatic testof the finished coiled tubing shall be performed at a pressurecorresponding to 100% of SMYS calculated in accordancewith the Von Mises equation and considering 95% of the nom-inal wall thickness. Test pressure shall be held for not less thantwo hours. ARSurface condition, imperfections and defects423 Requirements to visual examination performed at theplate mill are given in Appendix D, Subsection G. Require-ments for visual inspection of welds and pipe surfaces aregiven in Appendix D H500. MR and ARDimensions, mass and tolerances424 Requirements to dimensions, mass and tolerances shallbe as given in Subsection G.Weldability425 If agreed, the Manufacturer shall supply weldability dataor perform weldability tests. The details for carrying out thetests and the acceptance criteria shall be as specified in the pur-chase order.426 If requested, the linepipe supplier shall provide informa-tion regarding the maximum Post Weld Heat Treatment(PWHT) temperature for the respective materials. AR

B 500 Inspection501 Compliance with the requirements of the purchase ordershall be checked by specific inspection in accordance with EN10204. Records from the qualification of the MPS and other doc-umentation shall be in accordance with the requirements inSec.12.

Inspection frequency502 The inspection frequency during production shall be asgiven in Table 7-7 and the extent of testing for MPQT as givenin Table 7-8. Reference to the relevant acceptance criteria isgiven in these tables. MR503 A test unit is a prescribed quantity of pipe that is madeto the same specified outside diameter and specified wallthickness, by the same pipe-manufacturing process, from thesame heat, and under the same pipe-manufacturing conditions.504 For coiled tubing, all required mechanical testing inTable 7-7 shall be performed at each pipe end or for each heat,whichever gives the highest number of tests. Strip end weldsfor coiled tubing shall be tested according to ISO 3183 AnnexJ. AR505 Sampling for mechanical and corrosion testing shall beperformed after heat treatment, expansion and final shaping.The number and orientation of the samples are given in Table7-9. The samples shall not be prepared in a manner that mayinfluence their mechanical properties.506 In case of large quantities of longitudinally welded largediameter and heavy wall thickness pipe, where the test unit isgoverned by the heat size, it may be agreed that pipes from sev-eral heats represents one test unit. The first 30 000 tons shall betested with a frequency according to normal practice of thisstandard. After exceeding 30 000 tons, the below testing phi-losophy may be applied:

— each test unit may consist of pipes from maximum 3 heats— in case of test failure, the test frequency shall revert to the

normal rate of testing until again 30 000 tons with satisfac-tory results are documented.

Re-testing507 In order to accept or reject a particular heat with an orig-inal heat release failure, re-testing shall be conducted inaccordance with B508 through B512.508 If a test fails to meet the requirements, two re-tests shallbe performed (for the failed test only) on samples taken fromtwo different pipes within the same test unit. Both re-tests shallmeet the specified requirements. The test unit shall be rejectedif one or both of the re-tests do not meet the specified require-ments.509 The reason for the failure of any test shall be establishedand the appropriate corrective action to prevent re-occurrenceof the test failures shall be taken accordingly.510 If a test unit has been rejected, the Manufacturer mayconduct individual testing of all the remaining pipes in the testunit. If the total rejection of all the pipes within one test unitexceeds 25%, the test unit shall be rejected. In this situation theManufacturer shall investigate and report the reason for failureand shall change the manufacturing process if required. Re-qualification of the MPS is required if the agreed allowablevariation of any parameter is exceeded (see A609 and A610).511 Re-testing of failed pipes shall not be permitted. If a pipefails due to low CVN values in the fusion line (HAZ) or weldline in HFW pipe, testing of samples from the same pipe maybe performed subject to agreement. Refer to B344 for re-processing of pipe.512 If the test results are influenced by improper sampling,machining, preparation, treatment or testing, the test sampleshall be replaced by a correctly prepared sample from the samepipe and a new test performed.Heat and product analysis513 Heat and product analysis shall be performed in accord-ance with Appendix B. MR514 If the value of any elements, or combination of elementsfails to meet the requirements, two re-tests shall be performed

Table 7-6 C-Mn steel linepipe, Charpy V-notch impact testing temperatures T0 (ºC) as a function of Tmin (ºC) (Minimum Design Temperature)Nominal wall Thickness (mm) PIPELINES and riserst ≤ 20 T0 = Tmin20 < t ≤ 40 T0 = Tmin – 10t > 40 T0 = to be agreed in each case

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on samples taken from two different pipes from the same heat.If one or both re-tests still fail to meet the requirements, theheat shall be rejected. MRMechanical testing515 All mechanical testing shall be performed according toAppendix B. MRMetallurgical testing516 Macro examination and metallographic examinationshall be performed in accordance with Appendix B.Hydrostatic test (mill pressure test)517 Hydrostatic testing shall be performed in accordance

with Subsection E. MRNon-destructive testing518 NDT, including visual inspection, shall be carried out inaccordance with Subsection F. AR and MRDimensional testing519 Dimensional testing shall be performed according toSubsection G. MRTreatment of surface imperfections and defects520 Surface imperfections and defects shall be treatedaccording to Appendix D H300. MR

Table 7-7 Inspection frequency for C-Mn steel linepipe during production 1 ,2)

Applicable to:

Type of test Frequency of testing Acceptance criteria

All pipe Heat analysis One analysis per heat Table 7-3 or Table 7-4Product analysis Two analyses per heat (taken from separate product

items)Tensile testing of the pipe body Once per test unit of not more than 50/1003) pipes with

the same cold-expansion ratio4)Table 7-5

CVN impact testing of the pipe body of pipe with specified wall thickness as given in Table 22 of ISO 3183

Once per test unit of not more than 50/1005) pipes with the same cold-expansion ratio4)

Table 7-5 and Table 7-6

Hardness testing Once per test unit of not more than 50/1003) pipes with the same cold-expansion ratio4) (AR)

Table 7-5

Hydrostatic testing Each pipe B420 to B422Pipe dimensional testing See Subsection G See Subsection GNDT including visual inspection See Subsection F (MR and AR) See Subsection F

(MR and AR)SAWL, SAWH, HFW

Tensile testing of the seam weld (cross weld test)

Once per test unit of not more than 50/1006) pipes with the same cold-expansion ratio4) (MR)

B406 and B407

CVN impact testing of the seam weld of pipe with specified wall thickness as given in Table 22 of ISO 3183



Hardness testing of hard spots Any hard spot exceeding 50 mm in any direction Appendix D H500Macrographic testing of seam weld At least once per operating shift7) B416

SAWL, SAWH

Guided-bend testing of the seam weld of welded pipe


B414

HFW Flattening test As shown in Figure 6 of ISO 3183 B412 and B413Metallographic examination At least once per operating shift7) B418 (MR)

Notes

1) Sampling of specimens and test execution shall be performed in accordance with Appendix B. For tensile, CVN, hardness, guided-bend and flattening testing Appendix B refers to ISO 3183 without additional requirements.

2) The number orientation and location of test pieces per sample for mechanical tests shall be in accordance with Table 7-9.3) Not more than 100 pipes with D ≤ 508 mm and not more than 50 pipes for D > 508 mm.4) The cold-expansion ratio is designated by the Manufacturer, and is derived using the designated before-expansion outside diameter or circumference and

the after-expansion outside diameter or circumference. An increase or decrease in the cold-expansion ratio of more than 0.002 requires the creation of a new test unit (for lined pipe this does not apply to the liner expansion process).

5) Not more than 100 pipes with 114.3 mm ≤ D ≤ 508 mm and not more than 50 pipes for D > 508 mm.6) Not more than 100 pipes with 219.1 mm ≤ D < 508 mm and not more than 50 pipes for D > 508 mm.7) At least once per operating shift plus whenever any change of pipe size occurs during the operating shift. If qualified alternative methods for detection of

misalignments is used, testing is only required at the beginning of the production of each combination of specified outside diameter and specified wall thickness.

where D = Specified outside diameter

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Table 7-8 Additional testing for Manufacturing Procedure Qualification Test for C-Mn steel pipe 1)

Applicable to: Type of test Extent of testing Acceptance criteriaAll pipe All production tests as stated in Table 7-7 One test for each pipe pro-

vided for manufacturing procedure qualification 4)

See Table 7-7SMLS pipe 2, 3) with t > 25 mm

CVN testing at ID of quenched and tempered seamless pipe with t > 25 mm AR


Welded pipe (all types) All weld tensile test AR Table 7-5 8)

Fracture toughness (CTOD) test of weld metal 5, 6) AR B415Ageing test 7), see A606 AR Table 7-5

Notes

1) Sampling of specimens and test execution shall be performed in accordance with Appendix B.2) Only applicable to pipe delivered in the quenched and tempered condition.3) Sampling shall be 2 mm from the internal surface, see Appendix B, A500.4) Two pipes from two different test units shall be selected for the MPQT, see A600.5) CTOD testing is not required for pipes with t < 13 mm.6) For HFW pipe the testing applies to the fusion line (weld centre line).7) Only when cold forming during pipe manufacture exceeds 5% strain.8) Only SMYS, SMTS and elongation applies.

where t = specified nominal wall thickness

Table 7-9 Number, orientation, and location of test specimens per tested pipe 1, 2)

Applicable to: Sample location Type of test Wall thickness≤ 25 mm > 25 mm

Specified outside diameter Specified outside diameter< 219.1 mm ≥ 219.1 mm < 219.1 mm ≥ 219.1 mm

SMLS, not cold expanded pipe

Pipe body Tensile 1L3) 1L 1L3) 1LCVN 3T 3T 3T 3T

Hardness 1T 1T 1T 1TSMLS, cold expanded pipe

Pipe body Tensile 1L3) 1T4) 1L3) 1T4)

CVN 3T 3T 3T 3THardness 1T 1T 1T 1T

HFW pipe Pipe body Tensile 1L903) 1T1804) 1L903) 1T1804)

CVN 3T90 3T90 3T90 3T90Seam weld Tensile — 1W — 1W

CVN 3W and 3HAZ 5) MR 6W and 6HAZ 5) MRHardness 1W 1W 1W 1W

Pipe body and weld Flattening As shown in Figure 6 of ISO 3183SAWL pipe Pipe body Tensile 1L903) 1T1804) 1L903) 1T1804)

CVN 3T90 3T90 3T90 3T90Seam weld Tensile — 1W — 1W

CVN 3W and 6HAZ 6) MR 6W and 12HAZ 6) MRGuided-bend 2W 2W 2W 2W

Hardness 1W 1W 1W 1WSAWH pipe Pipe body Tensile 1L3) 1T4) 1L3) 1T4)

CVN 3T 3T 3T 3TSeam weld Tensile — 1W — 1W

CVN 3W and 6HAZ 6) MR 6W and 12HAZ 6) MRGuided-bend 2W 2W 2W 2W

Hardness 1W 1W 1W 1WNotes1) See Figure 5 of ISO 3183 for explanation of symbols used to designate orientation and location.2) All destructive tests may be sampled from pipe ends.3) Full-section longitudinal test pieces may be used at the option of the manufacturer, see Appendix B.4) If agreed, annular test pieces may be used for the determination of transverse yield strength by the hydraulic ring expansion test inaccordance with ASTM A370.5) For the HF weld seam, W means that the notch shall be located in the FL, while HAZ means that the notch shall be located in FL +2 (see Figure 6 in Appen-dix B).6) HAZ means that the notch shall be located in FL and FL +2 (see Figure 5 in Appendix B).

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C. Corrosion Resistant Alloy (CRA) LinepipeC 100 General101 All requirements of this subsection are applicable towelded and seamless linepipe in duplex stainless steel andseamless martensitic 13Cr stainless steel.102 Austenitic stainless steel and nickel based CRA linepipeshall be supplied in accordance with a recognised standard thatdefines the chemical composition, mechanical properties,delivery condition and all the details listed in Sec.6 and asspecified in the following. If a recognised standard is not avail-able, a specification shall be prepared that defines theserequirements.

C 200 Pipe designation201 CRA linepipe to be used to this standard shall be desig-nated with:

— DNV— process of manufacture (see A300)— grade (see Table 7-10 or C102, as applicable)— supplementary requirement suffix (see A400).

Guidance note:e.g. “DNV SMLS 22Cr D” designates a seamless 22Cr duplexsteel linepipe meeting the supplementary requirements forenhanced dimensional requirements.


C 300 ManufactureStarting material and steel making301 CRA linepipe shall be manufactured in accordance withthe processes given in A302 using the raw materials stated inthe qualified MPS, follow the same activity sequence, and staywithin the agreed allowable variations. The manufacturingpractice and instrumentation used to ensure proper control ofthe manufacturing process variables and their tolerances shallbe described in the MPS.302 All steels shall be made by an electric or one of the basicoxygen processes.Requirements to manufacture of pipe303 In addition to the requirements in C304 and C305 below,the following requirements given for C-Mn steel pipe are alsoapplicable for CRA pipes:

— B304-306 for seamless pipe— B307-310 and B313-320 for all welded pipes— B321-326 for SAW and MWP pipe— B330-345 for all pipe.

304 Before further processing, the slabs/ingots shall beinspected and fulfil the surface finish requirements specified inthe MPS.

Supply conditions305 Duplex and austenitic stainless steel pipe shall be deliv-ered in solution-annealed and water-quenched condition.

C 400 Acceptance criteriaChemical composition401 The chemical composition of duplex stainless steel andmartensitic 13Cr stainless steel parent materials shall beaccording to Table 7-10. Modifications are subject to agree-ment. The limits and tolerances for trace elements for marten-sitic 13Cr stainless steels, i.e. elements not listed in Table 7-10,shall be subject to agreement.Mechanical properties402 Requirements for tensile, hardness and Charpy V-notchproperties are given in Table 7-11. Weldment shall meet therequirement for KVT impact properties.403 In addition to the requirements in C404 and C405 below,the following acceptance criteria given for C-Mn steel pipe arealso applicable to CRA pipe (as applicable):

— B407 for transverse weld tensile testing— B410 and 411 for Charpy V-notch impact testing— B414 for guided-bend testing— B415 for fracture toughness testing of the seam weld.

404 For the flattening test of pipe with wall thickness ≥ 12.7mm, there shall be no opening of the weld, including the HAZ,until the distance between the plates is less than 66% of theoriginal outside diameter. For pipe with wall thickness< 12.7 mm there shall be no opening of the weld, including theHAZ, until the distance between the plates is less than 50% ofthe original outside diameter.405 For pipe with a D/t > 10, there shall be no cracks orbreaks other than in the weld, including the HAZ, until the dis-tance between the plates is less than 33% of the original out-side diameter.Macro examination of weld seam406 The macro examination of weld seam shall meet therequirements in B416 and B417.Microstructure of duplex stainless steel407 The material shall be essentially free from grain bound-ary carbides, nitrides and intermetallic phases after solutionheat treatment. Essentially free implies that occasional stringsof detrimental phases along the centreline of the base materialis acceptable given that the phase content within one field ofvision (at 400X magnification) is < 1.0% (max. 0.5% interme-tallic phases).408 The base material ferrite content of duplex stainless steelshall be within the range 35-55%. For weld metal and HAZ,the ferrite content shall be within the range 35-65%. Corrosion resistance of duplex stainless steel409 The maximum allowable weight loss for 25Cr duplexstainless steel is 4.0 g/m2 for solution annealed material testedfor 24 hours at 50°C.

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C 500 Inspection501 Compliance with the requirements of the purchase ordershall be checked by specific inspection in accordance with EN10204. Records from the qualification of the MPS and otherdocumentation shall be in accordance with the requirements inSec.12.Inspection frequency502 The inspection frequency during production and MPQTshall be as given in Table 7-12 and Table 7-13, respectively.Reference to the relevant acceptance criteria is given in thetables. 503 A test unit is a prescribed quantity of pipe that is madeto the same specified outside diameter and specified wallthickness, by the same pipe-manufacturing process, from thesame heat, and under the same pipe-manufacturing conditions.504 Sampling for mechanical and corrosion testing shall beperformed after heat treatment, expansion and final shaping.The samples shall not be prepared in a manner that may influ-ence their mechanical properties. Refer to B506 for reducedfrequency of testing in case of large quantities of pipe.505 The number and orientation of the samples for SMLSand SAWL/SAWH pipe shall be according to Table 7-9.506 For EBW and LBW pipe, the number and orientation ofthe samples shall be as for HFW in Table 7-9.507 For MWP pipe, the number and orientation of the sam-ples shall be as for SAWL pipe in Table 7-9.

Retesting508 Requirements for retesting shall be according to B508 toB512.Heat and product analysis509 Heat and product analysis shall be performed in accord-ance with Appendix B.510 All elements listed in the relevant requirement/ standardshall be determined and reported. Other elements added forcontrolling the material properties may be added, subject toagreement. 511 If the value of any elements, or combination of elementsfails to meet the requirements, two re-tests shall be performedon samples taken from two different pipes from the same heat.If one or both re-tests fail to meet the requirements, the heatshall be rejected.Mechanical testing512 All mechanical testing shall be performed according toAppendix B.Metallurgical testing513 Macro examination and metallographic examinationshall be performed in accordance with Appendix B.Corrosion testing of duplex stainless steels514 Corrosion testing of 25Cr duplex stainless steels accord-ing to ASTM G48 shall be performed in accordance withAppendix B B200.

Table 7-10 Duplex- and martensitic stainless steel linepipe, chemical compositionElement 1) Product analysis, wt.%

Grade22Cr duplex

Grade25Cr duplex

Grade13Cr - 2 Mo

Grade13Cr - 2.5 Mo

C 0.030 max 0.030 max 0.015 max 0.015 maxMn 2.00 max 1.20 max - -Si 1.00 max 1.00 max - -P 0.030 max 0.035 max 0.025 max 0.025 maxS 0.020 max 0.020 max 0.003 max 0.003 maxNi 4.50 - 6.50 6.00 – 8.00 4.50 min 6.00 minCr 21.0 - 23.0 24.0 – 26.0 12.0 min 12.0 minMo 2.50 – 3.50 3.00 – 4.00 2.00 min 2.50 minN 0.14 – 0.20 0.20 – 0.34 - -PRE - min. 40 2) - -Notes

1) If other alloying elements than specified in this table are being used, the elements and the maximum content shall be agreed in each case.2) PRE = %Cr+3.3%Mo+16%N.

Table 7-11 Duplex- and martensitic 13Cr stainless steel linepipe, mechanical propertiesGrade SMYS SMTS Ratio Maximum

Hardness(HV10)

Elongation in 50.8 mm

Af[%]

Charpy V-notch energy (KVT) 1)min. J, tested: at T0 = Tmin - 20ºC for

duplex, and according to Table 7-6 for martensitic 13Cr

MPa MPa Rt0.5 / Rm 2)

BM WMHAZ

Mean Single

22Cr 450 620 0.92 290 350 Note 3) 45 3525Cr 550 750 0.92 330 350 45 3513Cr-2 Mo 550 700 0.92 300 na 60 4513Cr-2.5 Mo 550 700 0.92 300 na 60 45Notes

1) The required KVL (longitudinal direction specimens) values shall be 50% higher than the required KVT values.2) The YS/UTS ratio in the longitudinal direction shall not exceed the maximum specified value in the transverse direction by more than 0.020.3) Ref. Note 4) in Table 7-5.

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Hydrostatic test (mill pressure test)515 Hydrostatic testing shall be performed in accordancewith Subsection E.Non-destructive testing516 NDT, including visual inspection, shall be in accordancewith Subsection F.

Dimensional testing517 Dimensional testing shall be performed according toSubsection G.Treatment of surface imperfections and defects518 Surface imperfections and defects shall be treatedaccording to Appendix D, H300.

D. Clad or Lined Steel LinepipeD 100 General101 The requirements below are applicable to linepipe con-sisting of a C-Mn steel backing material with a thinner internalCRA layer.102 Linepipe is denoted "clad" if the bond between the back-ing material and internal CRA layer is metallurgical, and"lined" if the bond is mechanical.103 The backing steel of lined pipe shall fulfil the require-ments in Subsection B.104 The manufacturing process for clad or lined linepipeshall be according to A303 to A305.105 Cladding and liner materials shall be specified accordingto recognised standards. If a recognised standard is not availa-ble, a specification shall be prepared that defines chemicalcomposition. If agreed corrosion testing and acceptance crite-ria shall be specified.106 The cladding/liner material thickness shall not be lessthan 2.5 mm, unless otherwise agreed.

D 200 Pipe designation201 In addition to the designation of the backing material

(see A303 to A305) clad/lined pipes shall be designated with:

— C, for clad pipe, or— L, for lined pipe — UNS number for the cladding material or liner pipe.

Guidance note:e.g. “DNV SAWL 415 D C - UNS XXXXX” designates a longi-tudinal submerged arc welded pipe, with SMYS 415 MPa, meet-ing the supplementary requirements for dimensions, clad with aUNS designated material.


D 300 Manufacturing Procedure Specification MPS for clad linepipe301 In addition to the applicable information given in A600,the MPS for clad linepipe shall as a minimum contain the fol-lowing information (as applicable):

— slab reheating temperature and initial rolling practice ofcladding alloy and backing material prior to sandwichassembly

— method used to assemble the sandwich or one-sided-openpackage, as applicable, prior to reheating and rolling

— package (sandwich or one-side-open) reheating tempera-

Table 7-12 Inspection frequency for CRA linepipe 1)

Applicable to Type of test Frequency of testing Acceptance criteria

All pipe All tests in Table 7-7 applicable to “All pipe”

As given in Table 7-7 Table 7-10 and Table 7-11

SAWL and MWP pipe All tests in Table 7-7 applicable to “SAWL”

EBW and LBW pipe 2) Flattening test As shown in Figure 6 of ISO 3183 C404 and C405

Duplex stainless steel pipe Metallographic examination Once per test unit of not more than 50/100 3) C407 and C408

25Cr duplex stainless steel pipe Pitting corrosion test (ASTM G48) Once per test unit of not more than 50/100 3) C409Notes

1) Sampling of specimens and test execution shall be performed in accordance with Appendix B. The number orientation and location of test pieces per sample for mechanical tests shall be according to C505-507.

2) For EBW and LBW pipes the testing applies to the fusion line.3) Not more than 100 pipes with 114.3 mm ≤ D ≤ 508 mm and not more than 50 pipes for D > 508 mm.

where D = Specified outside diameter

Table 7-13 Additional testing for Manufacturing Procedure Qualification Test of CRA linepipe 1)

Applicable to Type of test Frequency of testing Acceptance criteria

All pipe All production tests as stated above One test for each pipe provided for manufacturing procedure qualification 3)

Subsection CWelded pipe (all types) All weld tensile test Table 7-11

Fracture toughness (CTOD) test of weld metal 2) B415

Notes

1) Sampling of specimens and test execution shall be performed in accordance with Appendix B. The number, orientation and location of test pieces per sample for mechanical tests shall be according to C505-507.

2) CTOD testing is not required for pipes with t < 13 mm.3) Two pipes shall be provided for MPQT. The two pipes provided shall be from two different test units.

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ture, start and stop rolling temperatures, means of temper-ature and thickness control, start and stop temperatures foraccelerated cooling (if applicable) and inspection

— final plate heat treatment, e.g. quench and tempering (ifapplicable)

— method used to cut and separate the metallurgically rollbonded plates after rolling (separation of the sandwichbetween the CRA layers

— details regarding any CRA clad welding to pipe ends.

MPS for lined linepipe302 In addition to the applicable information given in A600,the MPS for lined linepipe shall as a minimum contain the fol-lowing information (as applicable):

— details for fabrication of backing pipe and liner— quality control checks for the lining process— details of data to be recorded (e.g. expansion pressure/

force, strain, deformation)— procedure for cut back prior to seal welding or cladding to

attach liner to carrier pipe— seal welding procedures— details regarding any CRA clad welding to pipe ends.

303 The following additional essential variable applies to thequalification of the MPS for clad linepipe (see A610):

— sequence of welding.

D 400 Manufacture401 During all stages of manufacturing, contamination ofCRA with carbon steel shall be avoided. Direct contact of theCRA layer with carbon steel handling equipment (e.g. hooks,belts, rolls, etc.) is prohibited. Direct contact may be allowedproviding subsequent pickling is performed.402 All work shall be undertaken in clean areas and control-led environment to avoid contamination and condensation.403 In addition to the requirements stated in B300 and C300(as applicable), the following shall apply:Welding consumables404 The welding consumables for seam welds and liner sealwelds shall be selected taking into consideration the reductionof alloying elements by dilution of iron from the base material.The corrosion properties of the weld consumable shall be equalto or superior to the clad or liner material.General requirnacture of clad linepipe405 The cladding alloy shall be produced from plate, andshall be supplied in a solution or soft annealed condition, asapplicable. 406 The steel backing material and the cladding alloy shallbe cleaned, dried and inspected to ensure that the level ofhumidity and particles between the respective plates are equalto or less than for the MPQT plates. 407 Unless otherwise agreed, the mating plate surfaces shallas a minimum be blast cleaned to a surface cleanliness of ISO8501 Sa2. 408 A pre-clad rolling assembly procedure shall be part ofthe MPS. This procedure shall include details of all surfacepreparation to be performed just prior to the sandwich assem-bly (if applicable).409 The sandwich or one-side-open packages, as applicable,shall be hot rolled in order to ensure metallurgical bondingbetween the base and the cladding material.410 The package consisting of sandwich or one-side-open,shall be manufactured through a TMCP route, or receive a finalheat treatment (e.g. quench and tempering).

Welding of clad linepipe411 In addition to the applicable requirements given in B307to B331, the following requirements shall apply for welding ofclad linepipe:

— the corrosion properties of the CRA weld consumable (e.g.root and hot pass) shall be equal or superior to the cladmaterial

— the longitudinal weld shall be back purged with weldinggrade inert gas and be free from high temperature oxides

— tack welds shall be made using GTAW, GMAW, G-FCAW or SMAW using low hydrogen electrodes

— weld seam tracking of continuous welding shall be auto-matically controlled.

General requirements to manufacture of lined linepipe412 The liner pipe shall be manufactured according toAPI 5LC.413 The internal surface of the C-Mn steel backing pipe shallbe blast cleaned to a surface cleanliness of ISO 8501 Sa2 alongthe complete length of the pipe prior to fabrication of linedpipe. The external surface of the liner pipe shall be blastcleaned as specified above or pickled.414 The liner pipe shall be inserted into the backing C-Mnsteel pipe after both pipes have been carefully cleaned, driedand inspected to ensure that the level of humidity and particlesin the annular space between these two pipes are equal to orless than for the MPQT pipes. 415 The humidity during assembly shall be less than 80%,and the carbon steel and CRA surfaces shall be maintained atleast 5ºC above the dewpoint temperature. Temperature andhumidity shall continuously be measured and recorded.416 After having lined up the two pipes, the liner shall beexpanded by a suitable method to ensure adequate gripping.The carbon steel pipe shall not under any circumstancesreceive a sizing ratio, sr , exceeding 0.015 during the expansionprocess (See B331).Welding of lined linepipe417 The liner pipe shall be welded according to API 5LC.418 Subsequent to expansion, the liner or backing pipe shallbe machined at each end and further fixed to the backing pipeby a seal weld (clad or fillet weld, respectively) to ensure thatno humidity can enter the annulus during storage, transporta-tion and preparation for installation.419 In addition to the applicable requirements given in B307to B331, the following requirements shall apply for welding oflined linepipe:

— the corrosion properties of the CRA weld consumable (e.g.fillet or clad weld) shall be equal or superior to the linermaterial

— the weld shall be purged with welding grade inert gas andbe free from high temperature oxides.

D 500 Acceptance criteriaProperties of the backing material501 The backing material of the manufactured clad or linedlinepipe shall comply with the requirements for C-Mn steelgiven in Subsection B. Sour service requirements according toI100 shall not apply to the backing material unless requiredaccording to I115.502 The cladding/liner material shall be removed from thetest pieces prior to mechanical testing of the backing material.Hardness503 The hardness of the base material, cladding material,HAZ, weld metal and the metallurgical bonded area shall meetthe relevant requirements of this standard.

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Bonding strength of clad linepipe504 After bend testing in accordance with Appendix B A906(see Table 7-14), there shall be no sign of cracking or separa-tion on the edges of the specimens.505 After longitudinal weld root bend testing in accordancewith Appendix B A607 (see Table 7-15), the bend test speci-men shall not show any open defects in any direction exceed-ing 3 mm. Minor ductile tears less than 6 mm, originating at thespecimen edge may be disregarded if not associated with obvi-ous defects.506 The minimum shear strength shall be 140 MPa.Properties of the CRA of clad and lined linepipe507 The CRA material shall meet the requirements of the rel-evant reference standard, e.g. API 5LD.Chemical composition of welds508 The chemical composition of the longitudinal seam weldof clad pipes, pipe end clad welds, and the liner seal welds (ifexposed to the pipe fluid), shall be analysed during MPQT.Unless otherwise agreed the composition of the deposited weldmetal as analysed on the exposed surface shall meet therequirements of the base material specification.Unless otherwise agreed the calculated PRE (see Table 7-10,note no. 2) for alloy 625 weld metal shall not be less than forthe clad pipe base material or liner material.Microstructure509 The weld metal and the HAZ in the root area of the cladpipe seam welds, any pipe end clad welds and the seal welds oflined pipe shall be essentially free from grain boundary car-bides, nitrides and intermetallic phases.Gripping force of lined linepipe510 Acceptance criteria for gripping force production testingshall be agreed based on project specific requirements (seeSec.6 B400) and/or test results obtained during MPQT.Liner collapse511 After the test for presence of moisture in the annulusbetween the liner and the backing material, the pipe shall beinspected and no ripples or buckles in the liner or carbon steelpipe shall be in evidence when viewed with the naked eye.

D 600 Inspection601 Compliance with the requirements of the purchase ordershall be checked by specific inspection in accordance with EN10204. Records from the qualification of the MPS and other docu-mentation shall be in accordance with the requirements in Sec.12.Inspection frequency602 The inspection frequency during production and MPQTshall be as given in Table 7-14 and Table 7-15, respectively.603 For clad pipe, the number and orientation of the samplesshall be as for SAWL pipe in Table 7-9604 For lined pipe, the number and orientation of the sam-ples for the backing steel shall be according to Table 7-9. Test-

ing of the liner pipe shall be according to API 5LC.Retesting605 Requirements for retesting shall be according to B508 toB512.Heat and product analysis606 Heat and product analysis shall be performed in accord-ance with B500 and C500 for the backing steel and the CRAliner or cladding, respectively.Mechanical testing607 All mechanical testing of clad pipe and the backing steelof lined pipe shall be performed according to Appendix B.Mechanical testing of the liner pipe shall be according to API5LC.608 Hardness testing of welded linepipe shall be performedon a test piece comprising the full cross section of the weld.Indentations shall be made in the base material, cladding mate-rial and the metallurgical bonded area as detailed inAppendix B. Corrosion testing609 Unless otherwise agreed, corrosion testing of rollbonded clad pipes or any longitudinal weld seams is notrequired.Metallurgical testing610 Macro examination and metallographic examinationshall be performed in accordance with Appendix B. Liner collapse test611 To check for the presence of moisture in the annulusbetween the liner and the backing material, one finished pipeor a section thereof (minimum length of 6 m) shall be heated to200ºC for 15 minutes and air cooled. This pipe shall be withinthe first 10 pipes produced. Gripping force test612 Gripping force of lined pipe shall be measured inaccordance with API 5LD. Equivalent tests may be appliedsubject to agreement. Inspection frequency for production test-ing shall be agreed based on test results obtained during theMPQT (see D300).Hydrostatic test (mill pressure test)613 Hydrostatic testing shall be performed in accordancewith Subsection E.Non-destructive testing614 NDT, including visual inspection, shall be in accordancewith Subsection F.Dimensional testing615 Dimensional testing shall be performed according toSubsection G.Treatment of surface imperfections and defects616 Surface imperfections and defects shall be treatedaccording to Appendix D, H300.

Table 7-14 Additional production testing for clad or lined steel linepipeApplicable to Type of test Extent of testing Acceptance criteriaAll pipe All tests in Table 7-7 applicable to “All pipe” See Table 7-7 and D600 D501Clad pipe All tests in Table 7-7 applicable to “SAWL”

Bend tests (2 specimens) Once per test unit of not more than 50 pipes D505Shear strength D507

CRA material of clad pipe

According to reference standard (see D508

Liner pipe According to API 5LC (see D508)Lined pipe Macrographic examination of seal weld Once per test unit of not more than 50 pipes Appendix C, F405

Gripping force test To be agreed, see D612 D511

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E. Hydrostatic TestingE 100 Mill pressure test101 Each length of linepipe shall be hydrostatically tested,unless the alternative approach described in E107 is used.102 The test pressure (ph) shall, in situations where the sealis made on the inside or the outside of the linepipe surface, beconducted at the lowest value obtained by utilising the follow-ing formulae:

103 103In situations where the seal is made against the endface of the linepipe by means of a ram or by welded on endcaps, and the linepipe is exposed to axial stresses, the test pres-sure shall be calculated such that the maximum combinedstress equals:

based on the minimum pipe wall thickness tmin.Guidance note:The Von Mises Equivalent stress shall be calculated as:

where

(tmin is equivalent to t1 in Sec.5)---e-n-d---of---G-u-i-d-a-n-c-e---n-o-t-e---

104 For pipes with reduced pressure containment utilisation,the test pressure (ph) may be reduced as permitted inSec.5 B200.105 In case significant corrosion allowance has been speci-fied (as stated by the Purchaser in the material specification),or a large wall thickness is needed for design purposes other

than pressure containment, or significant temperature de-ratingof the mechanical properties take place, the mill test pressuremay be significantly higher than the incidental pressure. Forsuch conditions and where the mill pressure test capacity islimited, the mill test pressure may be limited to ph= 1.4·pli,(where pli is the local incidental pressure).106 The test configuration shall permit bleeding of trappedair prior to pressurisation of the pipe. The pressure test equip-ment shall be equipped with a calibrated recording gauge. Theapplied pressure and the duration of each hydrostatic test shallbe recorded together with the identification of the pipe tested.The equipment shall be capable of registering a pressure dropof minimum 2% of the applied pressure. The holding time attest pressure shall be minimum 10 seconds. Calibration recordsfor the equipment shall be available.107 Subject to agreement, the hydrostatic testing may beomitted for expanded pipes manufactured by the UOE process.It shall in such situations be documented that the expansionprocess and subsequent pipe inspection will:

— ensure that the pipe material stress-strain curve is linear upto a stress corresponding to E102

— identify defects with the potential for through-thicknesspropagation under pressure loading

— identify pipes subject to excessive permanent deformationunder pressure loading to a degree equivalent to that pro-vided by hydrostatic testing.

Workmanship and inspection shall be at the same level as forhydrostatically tested pipe.The expansion process parameters and inspection results shallbe recorded for each pipe.

F. Non-destructive TestingF 100 Visual inspection101 Visual inspection shall be in accordance with AppendixD H500.102 If visual inspection for detection of surface imperfec-tions is substituted with alternative inspection methods thenthe substitution shall conform to the requirements in AppendixD H505 and H506.

F 200 Non-destructive testing201 Requirements for Non-Destructive Testing (NDT) oflinepipe are given in Appendix D, Subsection H.202 Requirements for NDT (laminar imperfections) and vis-ual examination of plate, coil and strip performed at plate mill

Table 7-15 Additional testing for Manufacturing Procedure Qualification Test of clad or lined steel linepipe 1)

Applicable to Type of test Extent of testing Acceptance criteriaAll pipe All production tests in Table 7-14 One test for each pipe

provided for manufac-turing procedure quali-fication

See Table 7-14Corrosion testing of welds, if agreed, see D609 To be agreed

Clad pipe Chemical composition of seam weld and clad weld 2) D508Metallographic examination of the seam weld and clad weld 2) D509Longitudinal weld root bend test D505

Lined pipe Chemical composition of seal or clad welds 2) D508Metallographic examination of seal welds D509Liner collapse test D511

Notes

1) Sampling of specimens and test execution shall be performed in accordance with Appendix B. The number, orientation and location of test pieces per sample for mechanical tests shall be according to D603-604.

2) As applicable, according to D508 and D509.

(7.2)

(7.3)

N = True pipe wall force which depend on the test set up end restraints.

ph2 t⋅ minD tmin–-------------------- min SMYS[ 0.96 SMTS; 0.84 ]⋅⋅ ⋅=

s e min SMYS[ 0.96 SMTS; 0.84 ]⋅⋅=

s e s h2 s l

2+ s h s l⋅–=

s hph D tmin–( )⋅

2 tmin⋅-----------------------------------=

s lNAs-----=

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are given in Appendix D, Subsection G.203 Table 7-16 lists the required NDT of linepipe includinglamination check for welded linepipe. For welded pipe, lami-nation checks may be performed on linepipe or plate/strip at

the discretion of the Manufacturer.204 Alternative test methods may be accepted subject toagreement according to Appendix D, H401 and H402.

G. Dimensions, Mass and TolerancesG 100 General101 Linepipe shall be delivered to the dimensions specified inthe material specification, subject to the applicable tolerances.102 The pipe shall be delivered in random lengths or approx-imate length, as specified in the material specification.

G 200 Tolerances201 The diameter and out-of-roundness shall be within thetolerances given in Table 7-17. However, in areas where

defects have been completely removed by grinding, in accord-ance with Appendix D, H300, the minus tolerances for diame-ter and out-of-roundness tolerances shall not apply in theground area.202 The wall thickness shall be within the tolerances givenin Table 7-18.203 Geometric deviations, pipe straightness, end squarenessand weight shall be within the tolerances given in Table 7-19.204 Unless otherwise agreed, the minimum average lengthof pipe shall be 12.1 m, and the tolerances for length accordingto Table 7-19.

Table 7-16 Type and extent of non-destructive testing 1)

Applicable to Scope of testing Type of test 2) Extent of testing Reference (Appendix D)

All Visual inspection - 100% H500Residual magnetism - 5% 3) H500Imperfections in un-tested ends UT+ST 100% or cut off H600

Pipe ends of all pipe

Laminar imperfections pipe ends 4) UT 100% H700Laminar imperfections pipe end face/bevel ST 100%

SMLS Laminar imperfections in pipe body UT 100% H800Longitudinal imperfections in pipe body UT 100%Transverse imperfections in pipe body UT 100/10% 6)

Wall thickness testing UT 100% 7)

Longitudinal surface imperfections in pipe body 5) ST 100/10% 6)

HFW, EBW and LBW

Laminar imperfections in pipe body UT 100% H900Laminar imperfections in area adjacent to weld UT 100%Longitudinal imperfections in weld UT 100%

SAWL,SAWH and MWP

Laminar imperfections in pipe body UT 100% H1300Laminar imperfections in area adjacent to weld UT 100%Imperfections in weld UT 100%Surface imperfections in weld area 5) ST 100%/R 8)

Imperfections at weld ends RT 100%Clad pipe Lack of bonding in pipe body and pipe ends 9) UT 100% H1200

Laminar imperfections in pipe body UT 100%Longitudinal and transverse imperfections in weld UT 100%Laminar imperfections in area adjacent to weld UT 100%Surface imperfections in weld area ST 100%Imperfections in welds RT 100%

CRA liner pipe Longitudinal and transverse imperfections in weld EC or RT 100% H1000Lined pipe As required for the type of backing material used, see above - 100% -

Seal and clad welds ST 100% H1100Clad welds (bonding imperfections) UT 100%

Notes

1) The indicated test methods are considered to be industry standard. Alternative methods may be used as required in Appendix D, H400.2) Nomenclature: UT = ultrasonic testing, ST = surface testing, e.g. magnetic particle testing or EMI (flux leakage) for magnetic materials and liquid pene-

trant testing for non-magnetic materials, RT = radiographic testing and EC = eddy current testing, see Appendix D.3) 5% = testing of 5% of the pipes produced but minimum 4 pipes per 8-hour shift.4) Laminar inspection is not applicable to pipe with t ≤ 5 mm. Standard width of band to be tested is 50 mm, but a wider band may be tested if specified by

the Purchaser.5) Applicable to external surface only.6) 100/10% = 100% testing of the first 20 pipes manufactured and if all pipes are within specification, thereafter random testing (minimum five pipes per 8-

hour shift) during the production of 10% of the remaining pipes.7) The wall thickness shall be controlled by continuously operating measuring devices.8) 100%/R = 100% testing of the first 20 pipes manufactured. If all pipes are within specification, thereafter random testing of a minimum of one pipe per

8-hour shift.9) Applies to pipe ends irrespective if clad welds are applied to pipe ends or not.

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Tolerances for the weld seam205 Tolerances for the weld seam of welded pipe, i.e.:

— cap reinforcement MR*— root penetration MR*— cap and root concavity— radial offset— misalignment of weld beads for double sided welds— waving bead (dog-leg)— undercut— arc burns— start/stop craters/poor restart— surface porosity— cracks— lack of penetration/lack of fusion— systematic imperfections— burn through.

shall be within the tolerances given in Appendix D, Table D-4. *) MR indicates that the requirement is modified compared toISO 3183.206 Requirements for dents are given in Appendix D, H500.

G 300 Inspection301 The frequency of dimensional testing shall be accordingto Table 7-17 to Table 7-19.302 Suitable methods shall be used for the verification ofconformance with the dimensional and geometrical tolerances.Unless particular methods are specified in the purchase order,the methods to be used shall be at the discretion of the Manu-facturer.303 All test equipment shall be calibrated. Dimensional test-ing by automatic measuring devices is acceptable provided theaccuracy of the measuring devices is documented and found tobe within acceptable limits.304 Unless a specific method is specified in the purchaseorder, diameter measurements shall be made with a circumfer-ential tape, ring gauge, snap gauge, rod gauge, calliper, or opti-cal measuring device, at the discretion of the manufacturer.

Guidance note:For inspection of submerged arc welded pipe, ring gauges can beslotted or notched to permit passage of the gauge over the weldreinforcement. It is necessary that the pipe permit the passage ofthe ring gauge within (internal) or over (external) each end of thepipe for a minimum distance of 100 mm.


305 At pipe ends (unless otherwise agreed) inside measure-ments shall be used to determine diameter and out-of-round-ness. These measurements shall not be based oncircumferential measurements (e.g. tape). Out-of-roundnessshall be determined as the difference between the largest andsmallest inside diameter, as measured in the same cross-sec-tional plane. If agreed, tolerances may be applied to actualinternal diameter. MR (the requirement is modified comparedto ISO 3183).

306 The pipe body out-of-roundness shall be determined asthe difference between the largest and smallest outside diame-ter, as measured in the same cross-sectional plane.307 The wall thickness at any location shall be within the tol-erances specified in Table 7-18, except that the weld area shallnot be limited by the plus tolerance. Wall thickness measure-ments shall be made with a mechanical calliper or with a prop-erly calibrated non-destructive inspection device ofappropriate accuracy. In case of dispute, the measurementdetermined by use of the mechanical calliper shall govern. Themechanical calliper shall be fitted with contact pins having cir-cular cross sections of 6.35 mm in diameter. The end of the pincontacting the inside surface of the pipe shall be rounded to amaximum radius of 38.1 mm for pipe of size 168.3 mm orlarger, and up to a radius of d/4 for pipe smaller than size 168.3mm with a minimum radius of 3.2 mm. The end of the pin con-tacting the outside surface of the pipe shall be either flat orrounded to a radius of not less than 38.1 mm.308 Geometric deviations from the nominal cylindrical con-tour of the pipe, see Table 7-19, resulting from the pipe form-ing or manufacturing operations (i.e. not including dents), shallbe measured using a gauge with the correct curvature accord-ing to the specified internal/external diameter. The length ofthe gauge shall be 200 mm or 0.25 D, whichever is less.Internal measurements shall be taken within 50 mm of eachpipe end.External measurement shall be taken where indicated by visualinspection. MR (the requirement is modified compared to ISO3183).309 Straightness shall be measured according to Figure 1and Figure 2 in ISO 3183.310 Out-of squareness at pipe ends shall be measuredaccording to Figure 3 in ISO 3183.311 For pipe with D ≥ 141.3 mm, the lengths of pipe shall beweighed individually. For pipe with D < 141.3 mm, the lengthsof pipe shall be weighed either individually or in convenientlots selected by the Manufacturer.312 The mass per unit length, rl, shall be used for the deter-mination of pipe weight and shall be calculated using the fol-lowing equation:

where:

rl is the mass per unit length, in kg/mD is the specified outside diameter, expressed in mmt is the specified wall thickness, in mmC is 0.02466.313 All specified tests shall be recorded as acceptable ornon-acceptable.314 The minimum and maximum value for wall thicknessand the diameter of pipe ends and maximum out-of-roundnessat pipe ends, shall be recorded for 10% of the specified tests,unless a higher frequency is agreed. For weight and length100% of the actual measurement results shall be recorded.

rl = t(D-t) · C (7.4)

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Table 7-17 Tolerances for diameter and out-of-roundnessD [mm] Frequency

of inspection

Diameter Out-of-roundnessPipe body 1) Pipe end 2, 3)

Pipe body 2) Pipe end 3)SMLS Welded SMLS Welded

< 60.3 Once per test unit 4)

± 0.5 mm or ± 0.0075 D,whichever is greater

± 0.5 mm or ± 0.0075 D,whichever is greater, but max. ± 3.2 mm

± 0.5 mm or ± 0.005 D,whichever is greater, but max. ± 1.6 mm

Included in the diameter tolerance≥ 60.3 ≤ 610 0.015 D 0.01 D

> 610 ≤ 1422 ± 0.01 D ± 0.005 D, but max. ± 4.0 mm

± 2.0 mm ± 1.6 mm 0.01 D but max.10 mm for D/t ≤ 75By agreement for D/t > 75

0.0075 D but max. 8 mm for D/t ≤ 75By agreement for D/t > 75

> 1422 as agreedwhereD = Specified outside diametert = specified nominal wall thickness.

Notes

1) Dimensions of pipe body to be measured approximately in the middle of the pipe length.2) For SMLS pipe, the tolerances apply for t ≤ 25.0 mm, and the tolerances for heavier wall pipe shall be as agreed.3) The pipe end includes a length of 100 mm at each of the pipe extremities.4) Once per test unit of not more than 20 lengths of pipe. For D ≤ 168.3 mm; once per test unit of not more than 100 lengths of pipe, but minimum one (1)

and maximum 6 pipes per 8-hour shift. MR

Table 7-18 Tolerances for wall thicknessType of pipe Wall thickness [mm] Frequency of

inspectionTolerances 1)

SMLS

t < 4.0

100%

+ 0.6 mm - 0.5 mm4.0 ≤ t < 10.0 + 0.15 t - 0.125 t10.0 ≤ t < 25.0 ± 0.125 t

t ≥ 25.0 + 0.1 t or + 3.7 mm, whichever is greater- 0.1 t or - 3.0 mm, whichever is greater

HFW, EBW, LBW and MWP 2)t ≤ 6.0 ± 0.4 mm

6.0 < t ≤ 15.0 ± 0.7 mmt > 15.0 ± 1.0 mm

SAW 3)

t ≤ 6.0 ± 0.5 mm6.0 < t ≤ 10.0 ± 0.7 mm10.0 < t ≤ 20.0 ± 1.0 mm

t > 20.0 + 1.5 mm - 1.0 mmwheret = specified nominal wall thickness.

Notes

1) If the purchase order specifies a minus tolerance for wall thickness smaller than the applicable value given in this table, the plus tolerance for wall thick-ness shall be increased by an amount sufficient to maintain the applicable tolerance range.

2) Subject to agreement a larger plus tolerance for metallurgically clad pipes may be applied.3) The plus tolerance for wall thickness does not apply to the weld area.

Table 7-19 Tolerances for pipe geometric properties not covered in Table 7-17 and 7-18Characteristic to be tested Frequency of inspection TolerancesGeometric deviations (peaking and flats) 1) 10% 2) 0.005 D or 2.5 mm, whichever is lessStraightness, max. for full length of pipe 5% 2) ≤ 0.0015 LStraightness, max. deviation for pipe end region 3) 3 mmOut-of squareness at pipe ends ≤ 1.6 mm from true 90ºLength 100% min. 11.70 m and max. 12.70 m Weight of each single pipe / pipe bundle -3.5% / +10% of nominal weightTolerances for the pipe weld seam and dents see G205 and G206where L = actual length of pipe

Notes

1) Applicable to welded pipes only2) Testing of the required percentage of the pipes produced but minimum 4 pipes per 8-hour shift.3) The pipe end region includes a length of 1.0 m at each of the pipe extremities.

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H. Marking, Delivery Condition and Documentation

H 100 Marking101 All marking shall be easily identifiable and durable inorder to withstand pipe loading, shipping, and normal installa-tion activities.102 Marking shall include DNV linepipe designation (seeB200). Other type of marking shall be subject to agreement.103 Each linepipe shall be marked with a unique number.The marking shall reflect the correlation between the productand the respective inspection document.

H 200 Delivery condition201 The delivery condition of C-Mn steel pipe shall beaccording to Table 7-1.202 The internal surface of CRA pipes shall be pickled inaccordance with the purchase order. If agreed the external sur-face of CRA pipes shall be cleaned.

H 300 Handling and storage 301 On customer's request, each linepipe shall be protecteduntil taken into use.302 For temporary storage see Sec.6 D300.

H 400 Documentation, records and certification401 Linepipe shall be delivered with Inspection Certificate 3.1according to European Standard EN 10204 (Metallic Products -Types of Inspection Documents) or an accepted equivalent.402 Inspection documents shall be in printed form or in elec-tronic form as an EDI transmission that conforms to any EDIagreement between the Purchaser and the manufacturer.403 The Inspection Certificate shall identify the productsrepresented by the certificate, with reference to productnumber, heat number and heat treatment batch. The specifiedoutside diameter, specified wall thickness, pipe designation,type of pipe, and the delivery condition shall be stated.404 The certificate shall include or refer to the results of allspecified inspection, testing and measurements including anysupplementary testing specified in the purchase order. ForHFW pipe, the minimum temperature for heat treatment of theweld seam shall be stated.405 Records from the qualification of the MPS and otherdocumentation shall be in accordance with the requirements inSec.12 C100.

I. Supplementary RequirementsI 100 Supplementary requirement, sour service (S)101 Linepipe for sour service shall conform to the requirementsbelow. Sec.6 B200 provide guidance for material selection.102 All mandatory requirements in ISO 15156-2/3 shallapply, in combination with the additional requirements of thisstandard.

Guidance note:ISO 15156-1/2/3, Sec. 1, states that the standard is only applica-ble “to the qualification and selection of materials for equipmentdesigned and constructed using conventional elastic design crite-ria”. Any detrimental effects of induced strain will only apply ifthese are imposed during exposure to an H2S-containing envi-ronment; hence, for manufacture and installation of pipelines therestrictions imposed in the ISO standard are applicable also tostrain based design. Any restrictions for maximum allowablestrain during operation are beyond the scope of this standard.


C-Mn steel103 C-Mn steel linepipe for sour service shall conform toSubsection B, and to the modified and additional requirementsbelow, which conform to the requirements in ISO 3183 AnnexH: “PSL 2 pipe ordered for sour service”.104 The chemical compositions given in Table 7-3 andTable 7-4 shall be modified according to Table 7-20 and Table7-21, respectively.

105 Vacuum degassing or alternative processes to reduce thegas content of the steel should be applied.106 The molten steel shall be treated for inclusion shape control.

Table 7-20 Chemical composition for SMLS and welded C-Mn steel pipe with delivery condition N or Q for Supplementary requirement, sour service

SMYSProduct analysis, maximum. weight %

C 1) Mn 1) S 2) V Other 3,4)

Pipe with delivery condition N - according to Table 6-1245 - - 0.003 - -290 - - 0.003 - -320 - - 0.003 - -360 - - 0.003 - -Pipe with delivery condition Q - according to Table 6-1245 - - 0.003 - -290 - - 0.003 - -320 - - 0.003 - -360 - - 0.003 - -390 - - 0.003 - -415 - - 0.003 - Note 5,6)

450 - - 0.003 - Note 5,6)

485 0.16 1.65 0.003 0.09 Notes 5,6,7)

Notes


2) If agreed the sulphur content may be increased to ≤ 0.008% for SMLS and ≤ 0.006% for welded pipe, and in such cases lower Ca/S may be agreed.

3) Mo ≤ 0.15%. If agreed Cu ≤ 0.10%.4) Unless otherwise agreed, for welded pipe where calcium is intention-

ally added, Ca/S ≥ 1.5 if S > 0.0015%. For SMLS and welded pipe Ca ≤ 0.006%.

5) If agreed Mo ≤ 0.35%.6) If agreed Cr ≤ 0.45% and Ni ≤ 0.50%.7) The maximum allowable Pcm value shall be 0.22 for welded pipe and

0.25 for SMLS pipe.

Table 7-21 Chemical composition for welded C-Mn steel pipe with delivery condition M for Supplementary requirement, sour service

SMYSProduct analysis, maximum. weight %C1) Mn 1) S 2) Nb Other 3,4)

245 0.10 - 0.002 - -290 0.10 - 0.002 - -320 0.10 - 0.002 - -360 0.10 1.45 0.002 0.06 -390 0.10 1.45 0.002 - -415 0.10 1.45 0.002 - Note 5)

450 0.10 1.60 0.002 - Notes 5,6)

485 0.10 1.60 0.002 - Notes 5,6)

Notes1-5) See Table 7-20.6) If agreed Cr ≤ 0.45%.

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107 The requirements for mechanical properties in B400shall apply, except for the hardness.108 During MPQT and production, the hardness in the pipebody, weld and HAZ shall not exceed 250 HV10.If agreed, (see ISO 15156-2) and provided the parent pipe wallthickness is greater than 9 mm and the weld cap is not exposeddirectly to the sour environment, 275 HV10 is acceptable forthe weld cap area.109 Any hard spot larger than 50 mm in any direction, seeTable 7-7, shall be classified as a defect if its hardness, basedupon individual indentations, exceeds:

— 250 HV10 on the internal surface of the pipe, or— 275 HV10 on the external surface of the pipe.

Pipes that contain such defects shall be treated in accordancewith Appendix D H300.110 The acceptance criteria for the HIC test shall be the fol-lowing, with each ratio being the maximum permissible aver-age for three sections per test specimen when tested in Solution(Environment) A (see Table B.3 of ISO 15156-2):

— crack sensitivity ratio (CSR) ≤ 2%— crack length ratio (CLR) ≤ 15%, and— crack thickness ratio (CTR) ≤ 5%.

If HIC tests are conducted in alternative media (seeAppendix B B302) to simulate specific service conditions,alternative acceptance criteria may be agreed.111 By examination of the tension surface of the SSC speci-men under a low power microscope at X10 magnification thereshall be no surface breaking fissures or cracks, unless it can bedemonstrated that these are not the result of sulphide stresscracking.CRA linepipe112 CRA linepipe for sour service shall conform to SubsectionC, and the recommendations given in Sec.6 B200 and E700.113 Linepipe grades, associated hardness criteria, andrequirements to manufacturing/fabrication shall comply withISO 15156-3. Clad or lined steel linepipe114 Clad or lined steel or linepipe for sour service shall con-form to Subsection D, and to the modified and additional

requirements below.115 Materials selection for cladding/liner, the associatedhardness criteria, and requirements to manufacturing and fab-rication shall comply with ISO 15156-3. The same applies towelding consumables for weldments exposed to the internalfluid. For selection of the C-Mn steel base material the consid-erations in A13.1 of ISO 15156-3 shall apply.116 During qualification of welding procedures and produc-tion, hardness measurements shall be performed as outlined inAppendix B. The hardness in the internal heat-affected zoneand in the fused zone of the cladding/lining shall comply withrelevant requirements of ISO 15156-3.Specific inspection117 The frequency of inspection for shall be as given inTables 7-7, 7-8, 7-12 and 7-13, as relevant, and with additionaltesting given in Table 7-22.118 HIC testing during production shall be performed on onerandomly selected pipe from each of the three (3) first heats, oruntil three consecutive heats have shown acceptable testresults. After three consecutive heats have shown acceptabletest results, the testing frequency for the subsequent productionmay be reduced to one test per test unit of not more than ten(10) heats.119 If any of the tests during the subsequent testing fail,three pipes from three different heats of the last ten heats,selecting the heats with the lowest Ca/S ratio (based on heatanalysis), shall be tested, unless the S level is below 0.0015.For heat with S level greater than 0.0015 heats shall be selectedwith the lowest Ca/S ratio. Providing these three tests showacceptable results, the ten heats are acceptable. However, ifany of these three tests fail, then all the ten heats shall be tested.Further, one pipe from every consecutive heat shall be testeduntil the test results from three consecutive heats have beenfound acceptable. After three consecutive heats have shownacceptable test results, the testing frequency may again bereduced to one test per ten heats.SSC test120 If specified in the purchase order SSC testing shall beperformed in accordance with ISO 15156 2/3 as applicable.(see Sec. 6 B409).

I 200 Supplementary requirement, fracture arrest properties (F)201 The requirements to fracture arrest properties are validfor gas pipelines carrying essentially pure methane up to 80%usage factor, up to a pressure of 15 MPa, 30 mm wall thicknessand 1120 mm diameter.202 A Charpy V-notch transition curve shall be establishedfor the linepipe base material. The Charpy V-notch energyvalue in the transverse direction at Tmin shall, as a minimum,

meet the values given in Table 7-23. Five sets of specimensshall be tested at different temperatures, including Tmin, andthe results documented in the qualification report.Properties of pipe delivered without final heat treatment203 This paragraph does not apply to linepipes deliveredwith a final heat treatment (e.g. normalising or quench andtempering). A Charpy V-notch transition curve shall be estab-lished for the linepipe base material in the aged condition. Theplastic deformation shall be equal to the actual deformation

Table 7-22 Applicable testing for Supplementary requirement S 1)

Production tests

Type of pipe Type of test Extent of testing Acceptance criteriaWelded C-Mn steel pipe HIC test In accordance with I118 and I119 I110

Tests for Manufacturing Procedure Qualification TestType of pipe Type of test Extent of testing Acceptance criteriaWelded C-Mn steel pipe HIC test If agreed, one test (3 test pieces) for each pipe provided

for manufacturing procedure qualificationI110

All pipe (only if agreed, see Sec. 6 B202)

SSC test I111

Notes

1) Sampling of specimens and test execution shall be performed in accordance with Appendix B.

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introduced during manufacturing (no additional straining isrequired). The samples shall be aged for 1 hour at 250°C. Fivesets of specimens shall be tested at different temperatures,including Tmin. The Charpy V-notch energy value in the trans-verse direction, at Tmin, shallas a minimum, meet the valuesgiven in Table 7-23 in the aged condition. Values obtained atother test temperatures are for information.204 Drop Weight Tear Testing (DWTT) shall only be per-formed on welded linepipe with outer diameter > 500 mm, wallthickness > 8 mm and SMYS > 360 MPa. A DWTT transitioncurve shall be established for the linepipe base material. Mini-

mum five sets of specimens shall be tested at different temper-atures, including Tmin. Each set shall consist of two specimenstaken from the same test coupon. The test shall be performedin accordance with Appendix B. The specimens tested at theminimum design temperature shall as a minimum, meet anaverage of 85% shear area with one minimum value of 75%.205 If supplementary requirements for sour service as inI100 are specified for linepipe material with SMYS ≥ 450 MPathe acceptance criteria stated in I204 (average and minimumshear area) may be subject to agreement.

I 300 Supplementary requirement, linepipe for plastic deformation (P)301 Supplementary requirement (P) is applicable to linepipewhen the total nominal strain in any direction from a singleevent is exceeding 1.0% or accumulated nominal plastic strainis exceeding 2.0%. The required testing is outlined in Table 7-25 and detailed below. The requirements are only applicable tosingle event strains below 5%.302 For pipes delivered in accordance with supplementaryrequirement (P), tensile testing shall be performed in the lon-gitudinal direction using proportional type specimens inaccordance with Appendix B, in order to meet the require-ments in I303. Tensile testing in the longitudinal directionaccording to Table 7-9 is not required. Transverse tensile test-ing according to Table 7-9 is required.303 The finished pipe (for C-Mn steel the requirements areapplicable up to X65, otherwise subject to agreement) shall meetthe following requirements to tensile properties in longitudinaldirection (see I302) prior to being tested according to I304:

— the difference between the maximum and minimum meas-ured base material longitudinal yield stress shall notexceed 100 MPa

— the YS/TS ratio shall not exceed 0.90 unless otherwisespecified. This requirement does not apply to pipe speci-fied as coiled tubing.

— the elongation shall be minimum 20%.

Guidance note:A higher yield to tensile ratio may be specified in case the localbuckling utilisation is not fully utilised given by: ah = 1 - 0.2 · eF · gc ·1.2/ecBuckling of the pipeline during on-reeling is primarily caused bystrain concentrations in the pipeline. These strain concentrationsare primarily caused by variation in thickness and yield stressalong the pipeline. The strain hardening capability combinedwith a tighter tolerance on the yield stress are therefore goodmeasures to mitigate these buckles. The stated criteria alone doesnot prevent buckles, evaluations of the loading scenario is alsonecessary.


Table 7-23 Charpy V-notch Impact Test Requirements for Fracture Arrest Properties tested at Tmin (Joules; Transverse Values; Average value of three full size base material specimens) 1, 2)

Wallthickness

≤ 30 mm 3)

OD (mm) Notes

1) Minimum individual results to exceed 75% of these values, (max 1 specimen per set)

2) The values obtained in the longitudinal direction, when tested, shall be at least 50% higher than the values required in the transverse direction.

3) Fracture arrest properties for larger wall thick-nesses and diameters shall be subject to agreement (see Sec. 5 D1100)

SMYS ≤ 610 ≤ 820 ≤ 1120245 40 40 40290 40 43 52360 50 61 75415 64 77 95450 73 89 109485 82 100 124555 103 126 155

Table 7-24 Applicable testing for Supplementary requirement FType of pipe Type of test Extent of testing Acceptance criteriaAll pipe CVN impact testing of the pipe body for establishment of transition curve One test for each

pipe provided for manufacturing pro-cedure qualification

Table 7-23 1)

Welded pipe DWT testing I204 (see also I205)Welded pipe except CRA pipe

CVN impact testing of the pipe body for establishment of transition curve, aged condition 2)

Table 7-23 1)

Notes

1) The values obtained in the longitudinal direction, when tested, shall at least be 50% higher than the values required in the transverse direction.2) See I203

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304 As part of qualification of the pipe material, the finishedpipe shall be deformed either by full scale or simulated defor-mation (see Appendix B A1202-A1210) as stated by the Pur-chaser in the linepipe specification. After the deformation, specimens for mechanical testing (seeI306 and I307) shall be sampled in areas representative of thefinal deformation in tension, (see Appendix A). For full scalestraining the test specimens, which shall represent the strainhistory ending up in tension, shall be extracted from the sector5-7 o’clock of the pipe. 12 o’clock position is defined as thetop of the pipe when reeling on.The samples shall be artificially aged at 250°C for one hourbefore testing.305 Qualification for Supplementary requirement P may bebased on historical data to be documented by the Manufac-turer.306 The following testing shall be conducted of the basematerial after straining and ageing:

— longitudinal tensile testing— hardness testing in pipe mid wall thickness— Charpy V-notch impact toughness testing. Test tempera-

ture shall be according to Table 7-6 or Table 7-11 as rele-vant.

307 The following testing shall be performed of the longitu-dinal weld seam after straining and ageing:

— weld metal (all weld) tensile test— hardness testing (mid wall thickness)— Charpy V-notch test (transverse specimens).

308 The following requirements shall be met after strainingand ageing (see I306 and I307):

— SMYS, SMTS and hardness shall be according to Table 7-5 or 7-11, as relevant:

— the elongation shall be minimum 15%— Charpy V-notch impact toughness and hardness shall be

according to Table 7-5 or 7-11, as applicable.

309 If the supplementary requirement for sour service (S)and/or fracture arrest properties (F) is required, the testing forthese supplementary requirements shall be performed on sam-ples that are removed, strained and artificially aged in accord-ance with I304. The relevant acceptance criteria shall be met.

I 400 Supplementary requirement, dimensions (D)401 Supplementary requirements for enhanced dimensionalrequirements for linepipe (D) are given in Table 7-26.Requirements for tolerances should be selected by the Pur-chaser considering the influence of dimensions and toleranceson the subsequent fabrication/installation activities and thewelding facilities to be used.

Table 7-25 Additional testing for Supplementary requirement P 1)

Production testsType of pipe Type of test Extent of testing Acceptance criteriaAll pipe Tensile testing of the pipe body, longitudinal spec-

imen of proportional type 2)Once per test unit of not more than 50/100 3) pipes with the same cold-expansion ratio 4)

I303

Tests for Manufacturing Procedure Qualification Test (all testing on strained and aged samples)Type of pipe Type of test Extent of testing Acceptance criteriaAll pipe Tensile testing of the pipe body, longitudinal spec-

imen, strained and aged 2)One test for one of the pipes provided for manufacturing procedure qualification

I308

CVN impact testing of the pipe bodyHardness testing

Welded pipe Tensile testing of weld metal (all weld test) I308CVN impact testing of the seam weldHardness testing of the seam weld

Notes

1) Mechanical and corrosion testing shall be performed in accordance with Appendix B.2) Proportional type specimens according to ISO 6892 shall be tested, see Appendix B A408.3) Not more than 100 pipes with D ? 508 mm and not more than 50 pipes for D > 508 mm.4) The cold-expansion ratio is designated by the Manufacturer, and is derived using the designated before-expansion outside diameter or circumference and

the after-expansion outside diameter or circumference. An increase or decrease in the cold-expansion ratio of more than 0.002 requires the creation of a new test unit.

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I 500 Supplementary requirement, high utilisation (U)501 For welded pipes, supplementary requirement U doesonly consider the SMYS at ambient temperature in the trans-verse direction. For seamless pipes delivered in the quenchedand tempered condition testing may be conducted in the longi-tudinal direction.502 The test regime given in this sub-section intends toensure that the average yield stress is at least two standarddeviations above SMYS. The testing scheme applies to pro-duction in excess of 50 test units. Alternative ways of docu-menting the same based upon earlier test results in the sameproduction is allowed.

Guidance note:The outlined test regime is required to be able to meet Supple-mentary requirement U, but as stated above, even if all testedpipes fulfil the requirements for the grade in question the pipesdo not necessary fulfil the requirements for supplementaryrequirement U.


Mandatory mechanical testing503 The testing frequency shall comply with Table 7-7 orTable 7-12, as applicable.504 If the results from the mandatory testing meet therequirement SMYS × 1.03, no further testing is required inorder to accept the test unit.505 If the result from the mandatory testing falls belowSMYS, the re-test program given in I507 shall apply.Confirmatory mechanical testing506 If the mandatory test result falls between SMYS × 1.03and SMYS, then two (2) confirmatory tests taken from two (2)different pipes (a total of two tests) within the same test unit

shall be performed.If the confirmatory tests meet SMYS, the test unit is accepta-ble.If one or both of the confirmatory tests fall below SMYS, there-test program given in I508 shall apply.Re-testing507 If the result from the mandatory testing falls belowSMYS, four (4) re-tests taken from four (4) different pipes (atotal of 4 tests), within the same test unit, shall be tested. If thefour re-tests meet SMYS, the test unit is acceptable. If one ofthe re-tests fall below SMYS the test unit shall be rejected.508 If one or both of the confirmatory tests fail to meetSMYS, two (2) re-tests taken from each of two (2) differentpipes within the same test unit shall be tested (a total of 4 tests).If all re-tests meet SMYS, the test unit is acceptable. If any ofthe re-tests fall below SMYS, the test unit shall be rejected.509 Re-testing of failed pipes is not permitted.510 If the test results are influenced by improper sampling,machining, preparation, treatment or testing, the test sampleshall be replaced by a correctly prepared sample from the samepipe, and a new test performed.511 If a test unit has been rejected after re-testing (I507 andI508 above), the Manufacturer may conduct re-heat treatmentof the test unit or individual testing of all the remaining pipesin the test unit. If the total rejection of all the pipes within onetest unit exceeds 15%, including the pipes failing the manda-tory and/or confirmatory tests, the test unit shall be rejected.512 In this situation, the Manufacturer shall investigate andreport the reason for failure and shall change the manufactur-ing process if required. Re-qualification of the MPS is requiredif the agreed allowed variation of any parameter is exceeded.

Table 7-26 Supplementary requirements D, enhanced tolerances and/or increased frequency of inspection 1)

Type of pipe Characteristic to be tested Pipe diameter Frequency of inspection

Tolerances

All Diameter pipe ends - Each pipe end As per Table 7-17Out-of-roundness, pipe ends, D/t ≤ 75 610 < D ≤ 1422 0.0075 D, but max. 5.0 mm

SMLS Wall thickness 15.0 mm ≤ t < 25.0 mm - Each pipe +0.125 t – 0.1 tWall thickness t ≥ 25.0 mm - ± 0.1 t, but max. 3.0 mm

SAW pipe Wall thickness t ≤ 6.0 mm - ± 0.5 mmWall thickness t > 6.0 to ≤ 10.0 mm - ± 0.6 mmWall thickness t > 10.0 to ≤ 20.0 mm - ± 0.8 mmWall thickness t ≥ 20.0 mm - ± 1.0 mmGeometric deviations (peaking and flats)

- 10% of pipe ends

0.005 D or 1.5 mm, whichever is less

whereD = specified nominal outside diametert = specified nominal wall thickness.

Notes

1) For tolerances not specified in this table, the dimensional tolerances in Table 7-17 to Table 7-19 shall apply.2) Subject to agreement a larger plus tolerance for metallurgically clad pipes may be applied.

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SECTION 8CONSTRUCTION - COMPONENTS AND ASSEMBLIES

A. GeneralA 100 Objective101 This section specifies requirements to the constructionof pipeline components, and to the construction of assembliessuch as risers, expansion loops and pipe strings for reeling andtowing.

A 200 Application201 This Subsection is applicable to pressure containingcomponents (e.g. bends, flanges and connectors, Tee’s, valves

etc.) used in the submarine pipeline system.202 Design of components shall be in accordance withSec.5 F.203 Materials selection for components shall be in accord-ance with Sec.6 B500.

A 300 Quality assurance301 Requirements for quality assurance are given in Sec.2B500. Corresponding requirements for the material processingand the manufacture of components shall be specified.

B. Component RequirementsB 100 General101 Reference to requirements for manufacture and testingof components are listed in Table 8-1. Components covered by ISO standards102 The following types of components shall be manufac-tured and tested in accordance with the ISO standards listed inTable 8-1 and the additional and modified requirements givenin B400 - B700:

— induction bends— fittings— flanges— valves.

Components not covered by ISO standards103 Pipeline components not covered by any specific ISOstandard (see B201), shall comply with the general require-ments given in the following subsections:

— materials shall be in accordance with Subsection C— manufacture shall be in accordance with Subsection D— mechanical and corrosion testing of components covered

in this subsection shall be in accordance withSubsection E.

in addition to requirements for the different components inSubsection B according to Table 8-1.

B 200 Component specification201 A component specification reflecting the results of thematerials selection (see Sec.6 B200), and referring to this sec-tion of the offshore standard, shall be prepared by the Pur-chaser. The specification shall state any additionalrequirements to and/or deviations from this standard pertainingto materials, manufacture, fabrication and testing of linepipe.

B 300 Induction bends – additional and modified requirements to ISO 15590-1301 The ISO 15590-1 paragraph number is given in brackets.302 (8.1) The following additional requirements shall bestated in the MPS:

— the steel type and grade— the number and location of the pyrometers used (minimum

two, located 120-180° apart) and the allowable tempera-ture difference between them

— the centering tolerances for the coil— the number of water nozzles and flow rate.

303 (8.2) The chemical composition of C-Mn steel motherpipe, including the backing steel of clad mother pipe, shall bein agreement with the composition for the linepipe gradeslisted in Tables 7-3, 7-4, 7-20 or 7-21 in Sec.7. The maximumcarbon equivalent (CE) of quenched and tempered or normal-ised C-Mn steel mother pipe (delivery condition N or Q,respectively) shall be according to Table 8-2. The carbonequivalent (Pcm) of thermo-mechanical formed or rolled C-Mn

Table 8-1 Manufacture and testing of pipeline componentsComponents Requirements for manufacture and testing

given in this sectionReference code and applicable class or designation 1)

Bends B300 ISO 15590-1, Class C for non-sour and Class CS for sour service

Fittings2) B400 ISO 15590-2, Class C for non-sour and Class CS for sour service

Flanges B500 ISO 15590-3, Designation (L) for non-sour and desig-nation (LS) for sour service

Valves B600 ISO 14723Mechanical connectors B700 not covered by specific reference codeCP Insulating joints B800Anchor flanges B900Buckle and fracture arrestors B1000Pig traps B1100Repair clamps and repair couplings B1200Notes

1) The listed reference codes only cover C-Mn steels, for other materials reference is given to this section.2) Fittings include: Elbows, caps, tees, single or multiple extruded headers, reducers and transition sections.

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steel mother pipe (delivery condition M) shall be maximum0.02 higher than as required in Table 7-4.

304 The chemical composition of mother pipe for CRA mate-rials shall meet the applicable requirements for the relevantmaterial type and grade given in Sec.7. However, the supple-mentary requirements F, P, D or U are not applicable to bends.Mother pipe shall be subjected to NDT as required for linepipein Sec.7.Induction bends shall not be produced from CRA lined steelpipe.

Guidance note:Hot expanded mother pipe may experience dimensional instabil-ity after post bending heat treatment.Bends may be made from spare sections of normal linepipe. Itshould be noted that linepipe, particularly pipe manufacturedfrom TMCP plate, may not have adequate hardenability toachieve the required mechanical properties after induction bend-ing and subsequent post bending heat treatment.Mother pipe of CRA clad C-Mn steel should preferably be longi-tudinally welded pipe manufactured from roll bonded plate


305 All mother pipe shall be mill pressure tested in accord-ance with Sec.7, Subsection E, where Sec.7 E107 does notapply.306 (8.3 and Table 2) The following parameters shall beadditional to or modification of the essential variables given inTable 2:

— Heat of steel: This essential variable shall be replaced by:Change in ladle analysis for C-Mn steels outside ± 0.02%C, ± 0.02 CE and/or ± 0.03 in Pcm, or any change in nom-inal chemical composition for CRA's.

— Bending radius: Qualified MPS qualifies all larger radii,but not smaller.

— Forming velocity: ± 2.5 mm/min or ± 10%, whichever isthe greater.

— Any change in number and position of pyrometers usedand in the allowable temperature difference between thepyrometers.

— Any change in the stated tolerances for coil centring.— Any change in the number and size of cooling nozzles and

flow rate or water pressure.

307 (8.5) Heat treatment equipment and procedures shall bein accordance with D500.308 (9.4.4.2) For C-Mn steel bends intended for sour-serv-ice, hardness values up to 275 HV10 are acceptable in the out-side cap layer.309 (Table 3 and 9.4.3) For bends with wall thickness greaterthan 25 mm (intrados - after bending), additional CVN testingshall be performed during MPS qualification testing. In addi-tion to the test pieces sampled 2 mm below the outer surface,

the same number of specimens shall be sampled from the mid-wall thickness position in the following locations:

— transition zone base metal (if applicable)— bend extrados base metal— bend intrados base metal— bend weld metal.

310 (9.4.5) The three indicated surface hardness readings(per circumferential location) shall be located at the bendextrados, the neutral axis, and the bend intrados. Surface hard-ness testing using portable equipment shall be performed inaccordance with Appendix B.311 (9.4.6) For metallographic evaluation of CRA or cladinduction bends, the acceptance criteria shall be in accordancewith in Sec.7 C400 and C500.312 (9.5) The following additional NDT testing shall be per-formed in accordance with Appendix D (as applicable):

— H800, for RT of welds— H700 or H800, for UT of welds in C-Mn steel— H200, for UT of welds in duplex stainless steel— H800, for DP of welds in duplex stainless steel, and

Acceptance criteria for the additional testing shall be accord-ing Appendix D HOLD.313 (9.6) Ovality of cross sections shall be kept within thespecified tolerances. The bend radius shall be as specified bythe Purchaser, and large enough (e.g. 5x outer diameter) toallow passage of inspection vehicles when relevant.Dimensional control shall include the following additional ormodified tests and acceptance criteria:

— ID at bend ends (always measure ID) shall be within ± 3 mm— out-of-roundness of bend ends shall be maximum 1.5%

and maximum 3% for the body— the included angle between the centrelines of the straight

portions of the bend shall be within ±0.75°— identification of weld seam location, and— end squareness shall be within ± 0.5°, maximum 3 mm.

314 (9.7)Gauging shall be performed as specified in theComponent specification, see Sec.6 C300.315 (9.8) If hydrostatic testing of bends is specified, the test-ing shall be performed accordance with G100.316 (11) Marking requirements shall be specified to distin-guish between bends manufactured and tested to the require-ments above and unmodified ISO 15590-1 bends.

B 400 Fittings, tees and wyes - additional requirements to ISO 15590-2401 The following components shall be defined as fittings:Elbows, caps, tees, single or multiple extruded headers, reduc-ers and transition sections.402 The ISO 15590-2 paragraph number is given in brackets.403 (6.2) Tees and headers shall be of the integral (non-welded) reinforcement type. Outlets shall normally beextruded but other manufacturing methods may be used, ifagreed. Bars of barred tees and wyes shall not be weldeddirectly to the high stress areas around the extrusion neck. It isrecommended that the bars transverse to the flow direction arewelded to a pup piece, and that the bars parallel to the flowdirection are welded to the transverse bars only. If this isimpractical, alternative designs shall be considered in order toavoid peak stresses at the bar ends.404 (7) The information required in Sec.6 C302 shall be pro-vided.405 (8) The following additional information shall be pro-vided:

Table 8-2 Carbon equivalent values for mother pipeSMYS CE 1), max.245 0.36290 0.38320 0.40360 0.43390 0.43415 0.44450 0.45485 0.46555 0.47

Note

1) According to Table 7-3

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The MPS should specify the following items, as applicable:

a) For the starting material

— delivery condition— chemical composition, and— NDT procedures for examination of starting materi-

als.

b) For fitting manufacture

— NDT procedures— hydrostatic test procedures— dimensional control procedures— coating and protection procedures— handling, loading and shipping procedures, and— at-site installation recommendations.

For “one-off” fittings designed and manufactured for a specificpurpose, the following additional information shall be pro-vided:

— plan and process flow description/diagram— order specific quality plan including supply of material

and subcontracts, and— manufacturing processes including process- and process

control procedures.

406 (8.2) Starting material shall be subject to 100% NDT atan appropriate stage of manufacture according to:

— C-Mn steel and duplex stainless steel pipe shall be testedas required in Sec.7 or Appendix D C200.

— Appendix D B200, for RT of welds in starting materialsother than pipe

— Appendix D B300 or B400 as applicable, for UT of weldsin starting materials other than pipe

— Appendix D D200, for C-Mn steel forgings— Appendix D D300, for duplex stainless steel forgings— Appendix D C200, for UT of plate material

with acceptance criteria according to the correspondingrequirements of Appendix D.Subject to agreement, equivalent NDT standards with regard tomethod and acceptance criteria may be applied. 407 (8.3.2) Welding and repair welding shall be performedin accordance with qualified procedures meeting the require-ments in Appendix C. 408 (8.3.3) Heat treatment equipment and procedures shallbe in accordance with D500.409 (9.2) Test pieces shall be taken according to E101 andE103. Location of test specimens shall be in accordance withE100.410 (Table 2) Inspection, testing and acceptance criteriashall be in accordance with Class C with the following addi-tional requirements:

— the chemical composition for components shall be modi-fied according to C200

— the chemical composition of duplex stainless steel materi-als shall be according to C300

— Mechanical and hardness testing of weld seams asrequired by Appendix B

— the CVN test temperature shall be 10°C below the mini-mum design temperature

— Surface hardness testing of fittings of Class CS shall beperformed with acceptance criteria according to 9.4.4.2

— metallographic examination for welds and body of duplexstainless steel fittings shall be performed and in accord-ance with Appendix B and with acceptance criteriaaccording to E300

— HIC testing shall be performed on fittings in Class CSmanufactured from rolled material as required by inTable 8-4

— 25Cr duplex stainless steel fittings shall be corrosiontested as required in Table 8-4, and

— NDT of fitting bodies shall be performed according toB512.

411 (Table 3) The extent of testing and examination shallcomprise the following additional requirements:

— the test unit definition shall be amended to: Fitting or testpiece of the same designation, starting material wall thick-ness, heat, manufacturing procedure specification and heattreatment batch

— surface hardness tests shall be performed on two fittingsper test unit

— metallography of duplex stainless steel fittings with thelargest thickness exceeding 25 mm shall be performed asone per test unit

— HIC testing shall be performed for qualification of theMPS for fittings in Class CS manufactured from rolledmaterial, and

— 25Cr duplex stainless steel fittings shall be corrosiontested for qualification of the MPS, in accordance withTable 8-4.

412 (Table 2 and 9.5) NDT of each completed fitting shall beperformed in accordance with the Table 2, Class C with the fol-lowing additional requirements:

— the body of fittings manufactured from plates and pipesshall be subject to 100% magnetic particle testing for C-Mn steels and 100% dye penetrant/eddy current testing forduplex stainless steel

— the extrusion area for tees and headers with adjoining pipewall thickness ≥ 12 mm shall be subject to 100% volumet-ric ultrasonic and 100% magnetic particle testing for C-Mn steels and 100% volumetric ultrasonic and 100% dyepenetrant/eddy current testing for duplex stainless steel

— the extrusion area for tees and headers with adjoining pipewall thickness < 12 mm shall be subject to 100% magneticparticle testing for C-Mn steels and 100% dye penetrant/eddy current testing for duplex stainless steel

— overlay welds shall be tested 100%.

413 NDT shall be performed in accordance with Appendix D(as applicable):

— C400, for visual inspection— D200, for C-Mn/low alloy steel forgings— D300, for duplex stainless steel forgings— C206 through 213, for UT of a 50 mm wide band inside

ends/bevels— C221, for MT of ends/bevels— C222, for DP of ends/bevels— B200, for RT of welds— B300, for UT of welds in C-Mn/low alloy steel— B400, for UT of welds in duplex stainless steel— B500, for MT of welds in C-Mn/low alloy steel— B600, for DP of welds in duplex stainless steel— C300, for overlay welds— D400, for visual inspection of forgings— B800, for visual inspection of welds, and— C500, for residual magnetism.

Acceptance criteria shall be according to the correspondingrequirements of Appendix D. 414 (11) Marking requirements shall be specified to distin-guish between fittings manufactured and tested to the require-ments above and unmodified ISO 15590-2 fittings.

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B 500 Flanges and flanged connections - additional requirements to ISO 15590-3501 The ISO 15590-3 paragraph number is given in brackets.502 (7) The following additional information shall be pro-vided:

— required design life— nominal diameters, OD or ID, out of roundness and wall

thickness for adjoining pipes including required tolerances— dimensional requirements and tolerance if different from

ISO 7005-1— minimum design temperature (local)— maximum design temperature (local), and— external loads and moments that will be transferred to the

component from the connecting pipeline under installationand operation and any environmental loads (e.g. nominallongitudinal strain)

— material type and grade, delivery condition, chemicalcomposition and mechanical properties at design tempera-ture

— required testing, and— corrosion resistant weld overlay.

503 (8) Overlay welding shall be performed according toqualified welding procedures meeting the requirements ofAppendix C. 504 (8.1) The MPS shall be in accordance with D100.505 (8.2 & Table 4)

— The chemical composition for flanges shall be modifiedaccording to C200.

— The chemical composition of duplex stainless steel mate-rials shall be according to C300.

506 (8.4) Heat treatment equipment and procedures shall bein accordance with D500.507 (Table 3) Mechanical testing shall be performed inaccordance with the Table 3 with the following additionalrequirements:

— Tensile, impact and through thickness hardness shall beperformed once per test unit with the test unit defined as;Flanges of the same size, heat, manufacturing procedurespecification and heat treatment batch.

— Surface hardness testing shall be performed once per testunit for flanges in class LS.

— Mechanical, hardness and corrosion testing of flangesshall be performed as required by E100, acceptance crite-ria to E200 or E300.

— Metallographic examination for duplex stainless steelflanges shall be performed according to E100, withacceptance criteria according to E300.

508 (Table 5) The impact test temperature for C-Mn steeland low alloy flanges shall be 10°C below the minimum designtemperature for all thicknesses and categories.509 Hardness indentation locations shall be according toTable 8-4.510 (9.4.5) Metallographic examination of duplex stainlesssteel shall be performed in accordance with Appendix B, withacceptance criteria according to Sec.7 C400.511 (9.4.6 & 9.4.7)Corrosion testing of duplex stainless steel shall be according toTable 8-4.512 (9.5.4) The extent of NDT shall be100% magnetic parti-cle testing of ferromagnetic materials and 100% liquid pene-trant testing of non magnetic materials. A percentage test is notpermitted.(9.5.5) 100% ultrasonic testing of the final 50 mm of each end

of the flange shall be performed. 100% ultrasonic testing of thefirst 10 flanges of each type and size ordered. If no defects arefound during the testing of the first 10 flanges of each type andsize ordered the extent of testing may be reduced to 10% ofeach size and type. If defects are found in any tested flange, allflanges of the same size, heat, manufacturing procedure speci-fication and heat treatment batch shall be 100% tested.All flanges shall be subject to 100% visual inspection.513 Magnetic particle testing shall be performed in accord-ance with Appendix D, D200 or ISO 13664.Liquid penetrant testing shall be performed in accordance withAppendix D, D300 or ISO 12095.Ultrasonic testing of C-Mn/low alloy steel forgings shall beperformed in accordance with Appendix D, D200.Ultrasonic testing of duplex stainless steel forgings shall beperformed in accordance with Appendix D, D300.Testing of overlay welds shall be performed in accordancewith Appendix D C300.Visual examination shall be in accordance with Appendix DD400.Subject to agreement, equivalent NDT standards with regard tomethod and acceptance criteria may be applied. Acceptance criteria for forgings shall be in accordance with thecorresponding requirements of Appendix D, D500 and foroverlay welds only, in accordance with Appendix D, C600.514 (9.6) For flanges with specified dimensions and toler-ances different from ISO 7005-1, these specified requirementsshall be met.515 (9.9) Repair welding of flange bodies is not permitted.516 (11) Marking requirements shall be specified to distin-guish between flanges manufactured and tested to the require-ments above and unmodified ISO 15590-3 flanges.Flanged connections517 Sealing rings shall be compatible with the finish and sur-face roughness of the flange contact faces. 518 Sealing rings shall be capable of withstanding the maxi-mum pressure to which they could be subjected, as well asinstallation forces if flanges are laid in-line with the pipeline.Sealing rings for flanges shall be made from metallic materialsthat are resistant to the fluid to be transported in the pipelinesystem. Mechanical properties shall be maintained at the antic-ipated in service pressures and temperatures.519 Bolts shall meet the requirements given in Sec.6 C400.

B 600 Valves – Additional requirements to ISO 14723601 The ISO 14723 paragraph number is given in brackets.602 (Annex B) The following additional information shall beprovided:

— design standard— required design life— minimum design temperature (local)— maximum design temperature (local)— design pressure (local)— water depth, and— weld overlay, corrosion resistant and/or wear resistant.

Manufacturing procedure specification603 A manufacturing procedure specification in accordancewith D100 shall be documented.604 (7.1, 7.4 and 7.7) Materials shall be specified to meet therequirements given in subsection C.605 (7.5) The impact test temperature shall be 10°C belowthe minimum design temperature

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606 (7.6) Bolting shall meet the requirements of Sec.6 C400.607 (8) Welding shall be performed according to qualifiedwelding procedures meeting the requirements of Appendix C.608 (9.4) The extent, method and type of NDT of C-Mn/lowalloy steels shall be in accordance with ISO 14723, Annex E,QL 2 requirements. The extent and type of NDT of duplex stainless steels shall bein accordance with ISO 14723, Annex E, QL 2 requirements.Methods shall be according to Appendix D of this standard.The extent and type of NDT of weld overlay shall be in accord-ance with ISO 14723, Annex E, QL 2 requirements. themethod shall be according to Appendix D. Acceptance criteria for NDT shall be in accordance withISO 14723, Annex E with the following amendments:For UT 2, VT 2 and VT 3 the acceptance criteria shall be inaccordance with Appendix D of this standard.609 (9.5) Repair welding of forgings is not permitted.610 (10.2) Hydrostatic shell tests shall be performed inaccordance with ISO 14723, Clause 10, or according to speci-fied requirements.611 (11) Marking requirements shall be specified to distin-guish between valves manufactured and tested to the require-ments above and unmodified ISO 14723 valves.612 Valves with requirements for fire durability shall bequalified by applicable fire tests. Refer to API 6FA and BS6755 Part 2 for test procedures.

B 700 Mechanical connectors701 These requirements apply to manufacture and testing ofend connections such as hub and clamp connections connect-ing a pipeline to other installations.702 Bolting shall meet the requirements of Sec.6 C400.703 End connections shall be forged. NDT704 The extent of NDT shall be:

— 100% magnetic particle testing of ferromagnetic materialsand 100% liquid penetrant testing of non magnetic materi-als.

— 100% ultrasonic testing of forgings and castings— 100% RT of critical areas of castings— 100% ultrasonic or radiographic testing of welds— 100% magnetic particle testing / liquid penetrant testing of

welds — 100% visual inspection

NDT shall be performed in accordance with Appendix D (asapplicable):

— C400, for visual inspection— D200, for C-Mn/low alloy steel forgings— D300, for duplex stainless steel forgings— E200, for C-Mn/low alloy steel castings— E300, for duplex stainless steel castings— E400, for RT of castings — C221, for MT of ends/bevels— C222, for DP of ends/bevels— B200, for RT of welds— B300, for UT of welds in C-Mn/low alloy steel— B400, for UT of welds in duplex stainless steel— B500, for MT of welds in C-Mn/low alloy steel— B600, for DP of welds in duplex stainless steel— C300, for overlay welds— D400, for visual inspection of forgings— E500, for visual examination of castings— B800, for visual inspection of welds— C500, for residual magnetism.

Acceptance criteria shall be according to the correspondingrequirements of Appendix D.705 If hydrostatic testing is specified, the test shall be per-formed according to G100.

B 800 CP Insulating joints801 These requirements apply to manufacture and testing ofboltless, monolithic coupling type of insulating joints foronshore applications. 802 CP Insulating joints shall be manufactured from forg-ings803 Insulating joints shall be protected from electrical highcurrent high voltage from welding and lightening etc. in theconstruction period. If high voltage surge protection is not pro-vided in the construction period insulating joints shall be fittedwith a temporary short-circuit cable clearly tagged with theinstruction “not to be removed until installation of permanenthigh voltage surge protection.”804 For manufactures without previous experience in thedesign, manufacture and testing of insulating joints, one jointshould be manufactured and destructively tested for the pur-pose of qualifying the design and materials of the joint. The qualification programme should as a minimum contain thefollowing elements:

— bending to maximum design bending moment— Tension to maximum design tension— Pressure testing to 1.5 times the design pressure— Pressure cycling from minimum to maximum design pres-

sure 10 times at both minimum and maximum design tem-perature.

Before and after testing the resistance and electrical leakagetests should show the same and stable values.In addition, after full tests the joint should be cut longitudinallyinto sections to confirm the integrity of the insulation and fillmaterials and the condition of the O-ring seals.805 Insulation joint shall be forged close to the final shape (ifapplicable). Machining of up to 10% of the local wall thicknessat the outside of the component is allowed. 806 The extent of NDT shall be:

— 100% magnetic particle testing of ferromagnetic materialsand 100% liquid penetrant testing of non magnetic materials

— 100% ultrasonic testing of forgings — 100% ultrasonic or radiographic testing of welds— 100% magnetic particle testing / liquid penetrant testing of

welds — 100% visual inspection.


— C400, for visual inspection— D200, for C-Mn/low alloy steel forgings— D300, for duplex stainless steel forgings— C220, for MT of ends/bevels— C221, for DP of ends/bevels— B200, for RT of welds— B300, for UT of welds in C-Mn/low alloy steel— B400, for UT of welds in duplex stainless steel— B500, for MT of welds in C-Mn/low alloy steel— B600, for DP of welds in duplex stainless steel— C300, for overlay welds— D400, for visual inspection of forgings— B800, for visual inspection of welds, and— C500, for residual magnetism.

Acceptance criteria shall be according to the correspondingrequirements of Appendix D.

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807 Prior to hydrostatic testing, hydraulic fatigue test and thecombined pressure-bending test / electrical leakage tests shallbe performed and the results recorded. 808 Hydrostatic strength test of each insulating joint shall beperformed with a test pressure 1.5 times the design pressure,unless otherwise specified, and to the specified holding time ingeneral accordance with G100. 809 Hydraulic fatigue of each insulating joint shall be per-formed. The test shall consist of 40 consecutive cycles with thepressure changed from 10 barg to 85 percent of the hydrostatictest pressure. At the completion of the test cycles the pressureshall be increased to the hydrostatic test pressure and main-tained for 30 minutes. There shall be no leakage or pressureloss during the test.810 One insulating joint per size/design pressure shall alsobe tested to meet the specified bending moment requirements.The joint shall be pressurised to the specified hydrostatic testpressure and simultaneously be subjected to an external 4 pointbending load sufficient to induce a total (bending plus axialpressure effect) longitudinal stress of 90% of SMYS in theadjoining pup pieces. The test duration shall be 2 hours. Theacceptance criteria are no water leakage or permanent distor-tion.811 After hydrostatic testing, all isolating joints shall be leaktested with air or nitrogen. The joints shall be leak tested at 10barg for 10 minutes. The tightness shall be checked by immersionor with a frothing agent. The acceptance criterion is: no leakage. 812 The FAT shall be performed according to the acceptedFAT programme. The FAT shall consist of:

— dielectric testing— electrical resistance testing— electrical leakage tests.

813 Prior to testing insulating joints shall be stored for 48hours at an ambient temperature between 20 and 25°C and arelative humidity of 93%.814 Dielectric testing shall be performed by applying an ACsinusoidal current with a frequency of 50 - 60 Hz to the joint.The current shall be applied gradually, starting from an initialvalue not exceeding 1.2kV increasing to 5.0kV in a time notlonger than 10 seconds and shall be maintained at peak valuefor 60 seconds. The test is acceptable if no breakdown of theinsulation or surface arcing occurs during the test and a maxi-mum leakage of current across the insulation of 1 mA.815 Electrical resistance testing shall be carried out at 1000V DC. The test is acceptable if the electrical resistance is min-imum 25 MOhm. 816 Electrical leakage tests shall be performed to assess anychanges which may take place within a joint after hydrostatictesting, hydraulic fatigue test and the combined pressure-bend-ing test. No significant changes in electrical leakage shall beaccepted.

B 900 Anchor flanges901 Anchor flanges shall be forged. 902 The extent of NDT shall be:

— 100% magnetic particle testing of ferromagnetic materialsand 100% liquid penetrant testing of non magnetic materi-als

— 100% ultrasonic testing of forgings— 100% ultrasonic or radiographic testing of welds— 100% magnetic particle testing / liquid penetrant testing of

welds — 100% visual inspection


— C400, for visual inspection— D200, for C-Mn/low alloy steel forgings— D300, for duplex stainless steel forgings— C220, for MT of ends/bevels— C221, for DP of ends/bevels— B200, for RT of welds— B300, for UT of welds in C-Mn/low alloy steel— B400, for UT of welds in duplex stainless steel— B500, for MT of welds in C-Mn/low alloy steel— B600, for DP of welds in duplex stainless steel— D400, for visual inspection of forgings— B800, for visual inspection of welds, and— C500, for residual magnetism.

Acceptance criteria shall be according to the correspondingrequirements of Appendix D.

B 1000 Buckle- and fracture arrestors1001 The material for buckle and fracture arrestors and man-ufacture, inspection and testing shall be in accordance withSubsec.E or Sec.7.

B 1100 Pig traps1101 Materials shall comply with the requirements of thedesign code or with the requirements of this section, if morestringent.1102 Testing and acceptance criteria for qualification ofwelding procedures shall comply with the requirements of thedesign code or with the requirements of Appendix C, if morestringent.Essential variables for welding procedures shall comply withthe requirements of the design codeProduction welding shall comply with the requirementsAppendix C.1103 The extent, methods and acceptance criteria for NDTshall comply with the requirements of the design code. In addi-tion the requirements of Appendix D, subsection A and B100shall apply.1104 Hydrostatic testing shall comply with the requirementsof the design code

B 1200 Repair clamps and repair couplingsRepair clamps and repair couplings to be installed according toRP-F113 shall be manufactured and tested in general accord-ance with this section and based on materials selection accord-ing to Sec.6.

C. Materials for ComponentsC 100 General101 The materials used shall comply with internationallyrecognised standards, provided that such standards haveacceptable equivalence to the requirements given in Sec.7 andthis section. Modification of the chemical composition givenin such standards may be necessary to obtain a sufficient com-bination of weldability, hardenability, strength, ductility,toughness, and corrosion resistance.102 Sampling for mechanical and corrosion testing shall beperformed after final heat treatment, i.e. in the final condition.The testing shall be performed in accordance with Appendix Band E100.

C 200 C-Mn and low alloy steel forgings and castings201 These requirements are applicable to C-Mn and lowalloy steel forgings and castings with SMYS ≤ 555 MPa. Useof higher strength materials shall be subject to agreement.202 All steels shall be made by an electric or one of the basic

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oxygen processes. C-Mn steel shall be fully killed and made toa fine grain practice.203 The chemical composition for hot-formed, cast andforged components shall be in accordance with recognisedinternational standards. The chemical composition shall beselected to ensure an acceptable balance between sufficienthardenability and weldability.204 For materials to be quenched and tempered, a hardena-bility assessment shall be performed to ensure that the requiredmechanical properties are met.205 For C-Mn steels the maximum Carbon Equivalent (CE)shall not exceed 0.50, when calculated in accordance with:

206 Acceptance criteria for tensile, hardness and Charpy V-notch impact properties are given in E200.207 Forgings shall be delivered in normalised or quenchedand tempered condition. Minimum tempering temperatureshall be 610°C when PWHT will be applied, unless otherwisespecified.208 Castings shall be delivered in homogenised, normalisedand stress relieved or homogenised, quenched and temperedcondition.209 For C-Mn and low alloy materials delivered in thequenched and tempered condition, the tempering temperatureshall be sufficiently high to allow effective post weld heattreatment during later manufacture / installation (if applica-ble).

C 300 Duplex stainless steel, forgings and castings301 All requirements with regard to chemical compositionfor 22Cr and 25Cr duplex stainless steel shall be in accordancewith Sec.7 C400. 302 Acceptance criteria for tensile, hardness, Charpy V-notch impact properties and corrosion tests are given in E300.303 Duplex stainless steel castings and forgings shall bedelivered in the solution annealed and water quenched condi-tion.

C 400 Pipe and plate material401 Pipe and plate material shall meet the requirements inSec.7.402 For welded pipe it shall be assured that the mechanicalproperties of the material and longitudinal welds will not beaffected by any heat treatment performed during manufactureof components.403 In case post weld heat treatment is required, the mechan-ical testing should be conducted after simulated heat treatment.

C 500 Sour Service501 For components in pipeline systems to be used for fluidscontaining hydrogen sulphide and defined as “sour service”according to ISO 15156, all requirements to chemical compo-sition, maximum hardness, and manufacturing and fabricationprocedures given in the above standard shall apply. 502 The sulphur content of C-Mn and low alloy steel forg-ings and castings shall not exceed 0.010%. 503 Pipe and plate material used for fabrication of compo-nents shall meet the requirements given in Sec.7 I100.

D. ManufactureD 100 Manufacturing procedure specification (MPS) 101 The requirements of this subsection are not applicable toinduction bends and fittings that shall be manufactured inaccordance with B400 and B500102 Components shall be manufactured in accordance with adocumented and approved MPS.103 The MPS shall demonstrate how the fabrication will beperformed and verified through the proposed fabrication steps.The MPS shall address all factors which influence the qualityand reliability of production. All main fabrication steps fromcontrol of received material to shipment of the finished prod-uct(s), including all examination and check points, shall becovered in detail. References to the procedures and acceptancecriteria established for the execution of all steps shall beincluded.104 The MPS should be project specific and specify the fol-lowing items as applicable:

— starting materials— manufacturer— steel making process— steel grade— product form, delivery condition— chemical composition— welding procedure specification (WPS)— NDT procedures.— Manufacturing— supply of material and subcontracts— manufacturing processes including process- and process

control procedures— welding procedures— heat treatment procedures— NDT procedures— list of specified mechanical and corrosion testing— hydrostatic test procedures— functional test procedures— dimensional control procedures— FAT procedures— marking, coating and protection procedures— handling, loading and shipping procedures— at-site installation recommendations.

For “one-off” components and other components designed andmanufactured for a specific purpose, the following additionalinformation shall be provided:

— Plan and process flow description/diagram— Order specific quality plan including supply of material

and subcontracts— Manufacturing processes including process- and process

control procedures.

D 200 Forging201 Forging shall be performed in compliance with theaccepted MPS. Each forged product shall be hot worked as faras practicable, to the final size with a minimum reduction ratioof 4:1.202 The work piece shall be heated in a furnace to therequired working temperature. 203 The working temperature shall be monitored during theforging process.204 If the temperature falls below the working temperaturethe work piece shall be returned to the furnace and re-heatedbefore resuming forging.205 The identity and traceability of each work piece shall bemaintained during the forging process.206 Weld repair of forgings is not permitted.

CE C Mn6

-------- Cr Mo V+ +5

--------------------------------- Cu Ni+15

--------------------+ + +=

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D 300 Casting301 Casting shall be performed in general compliance withASTM A352.302 A casting shall be made from a single heat and as a sin-gle unit.303 Castings may be repaired by grinding to a depth of max-imum 10% of the actual wall thickness, provided that the wallthickness in no place is below the minimum designed wallthickness. The ground areas shall merge smoothly with the sur-rounding material.304 Defects deeper than those allowed by D303 may berepaired by welding. The maximum extent of repair weldingshould not exceed 20% of the total surface area. Excavationsfor welding shall be ground smooth and uniform and shall besuitably shaped to allow good access for welding.305 All repair welding shall be performed by qualified weld-ers and according to qualified welding procedures.

D 400 Hot forming401 Hot forming shall be performed to according to anagreed procedure containing:

— sequence of operations— heating equipment— material designation— pipe diameter, wall thickness and bend radius— heating/cooling rates— max/min. temperature during forming operation— temperature maintenance/control— recording equipment— position of the longitudinal seam— methods for avoiding local thinning— post bending heat treatment (duplex stainless steel: full

solution annealing and water quenching)— hydrostatic testing procedure— NDT procedures— dimensional control procedures.

402 Hot forming of C-Mn and low alloy steel, includingextrusion of branches, shall be performed below 1050°C. Thetemperature shall be monitored. The component shall beallowed to cool in still air.403 For duplex stainless steel material, the hot forming shallbe conducted between 1000 and 1150°C.

D 500 Heat treatment501 Heat treatment procedures for furnace heat treatmentshall as a minimum contain the following information:

— heating facilities— furnace— insulation (if applicable)— measuring and recording equipment, both for furnace con-

trol and recording of component temperature— calibration intervals for furnace temperature stability and

uniformity and all thermocouples— fixtures and loading conditions— heating and cooling rates— temperature gradients— soaking temperature range and time— maximum time required for moving the component from

the furnace to the quench tank (if applicable)— cooling rates (conditions)— type of quenchant (if applicable)— start and end maximum temperature of the quenchant (if

applicable).

502 If PWHT in an enclosed furnace is not practical, localPWHT shall be performed according to Appendix C, G400.503 The heat treatment equipment shall be calibrated at least

once a year in order to ensure acceptable temperature stabilityand uniformity. The uniformity test shall be conducted inaccordance with a recognised standard (e.g. ASTM A991).The temperature stability and uniformity throughout the fur-nace volume shall be within ± 10°C. 504 Whenever practical thermocouple(s) should be attachedto one of the components during the heat treatment cycle.505 Components should be rough machined to near finaldimensions prior to heat treatment. This is particularly impor-tant for large thickness components.

Guidance note:The extent and amount of machining of forgings and castingsprior to heat treatment should take into account the requirementsfor machining to flat or cylindrical shapes for ultrasonic exami-nation. See also Appendix D.


506 For components that shall be water quenched, the timefrom the components are leaving the furnace until beingimmersed in the quenchant shall not exceed 90 seconds for lowalloy steel, and 60 seconds for duplex stainless steels.507 The volume of quenchant shall be sufficient and shall beheavily agitated, preferably by cross flow to ensure adequatecooling rate. The maximum temperature of the quenchant shallnever exceed 40°C. Temperature measurements of the quen-chant shall be performed508 The hardness of the accessible surfaces of the compo-nent shall be tested. The hardness for C-Mn or low alloy steelsand duplex stainless steels shall be in accordance with E200and E300, respectively.

D 600 WeldingWelding and repair welding shall be performed in accordancewith qualified procedures meeting the requirements of Appen-dix C.

D 700 NDTNDT shall be performed in accordance with Appendix D.

E. Mechanical and Corrosion Testing of Hot Formed, Cast and Forged Components

E 100 General testing requirements101 Testing of mechanical properties after hot forming, cast-ing or forging shall be performed on material taken from oneprolongation or component from each lot (i.e. components ofthe same size and material, from each heat and heat treatmentbatch) shall be tested as given in Table 8-4, as applicable:102 All mechanical testing shall be conducted after final heattreatment.103 If agreed, separate test coupons may be allowed provid-ing they are heat treated simultaneously with the material theyrepresent, and the material thickness, forging reduction, andmass are representative of the actual component.104 A simulated heat treatment of the test piece shall be per-formed if welds between the component and other items suchas linepipe are to be PWHT at a later stage or if any other heattreatment is intended.105 The CVN test temperature shall be 10°C below the min-imum design temperature. 106 Sampling for mechanical and corrosion testing shall beperformed after final heat treatment, i.e. in the final condition.The testing shall be performed in accordance withAppendix B. 107 A sketch indicating the final shape of the component and

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the location of all specimens for mechanical testing shall beissued and accepted prior to start of production.108 For 25Cr duplex stainless steels corrosion testingaccording to ASTM G48 shall be performed in order to con-firm that the applied manufacturing procedure ensures accept-able microstructure. Testing shall be performed in accordancewith Appendix B, at 50°C. The test period shall be 24 hours.

E 200 Acceptance criteria for C-Mn and low alloy steels 201 Tensile, hardness and Charpy V-notch impact propertiesshall meet the requirements for linepipe with equal SMYS asgiven in Sec.7 B400.202 The hardness for components intended for non-sourservice shall not exceed 300 HV10. For components intendedfor sour service the hardness shall according to Sec.7 I100.

Figure 1 Location of tensile and CVN specimens, component with section thickness ≥ 25 mm

Table 8-4 Number, orientation, and location of test specimens per tested componentType of test No. of tests 1) Test location, e.g. as shown in Figure 1 2,3)

Tensile test 3 One specimen in tangential direction from the thickest section 1/4T below the internal surfaceOne mid thickness specimen in both tangential and axial direction from the area with highest utilisation (after final machining), e.g. the weld neck area 4)

CVN impact testing, axial and tan-gential specimens 5)

6 One set in each direction (axial and tangential) taken from the same locations as the two tensile specimens described above for the relevant wall thicknesses4) (thick sec-tion and high utilisation section, a total of 2 sets)

CVN impact testing of the thickest section of the component for section thickness ≥ 25 mm 5,6)

3 One set in the tangential direction 2 mm below the internal surface

Metallographic sample 3 As for the CVN impact testing setsHardness testing 7) 3 As for the CVN impact testing sets HIC and SSC test 8) 1 In accordance with ISO 15156ASTM G48 9) 1 See E109Notes

1) For CVN impact testing one test equals one set which consist of three specimens.2) For test pieces (components) having maximum section thickness, T ≤ 50 mm, the test specimens shall be taken at mid-thickness and the mid-length shall

be at least 50 mm from any second surface. For test pieces (components) having maximum section thickness, T > 50 mm, the test specimens shall be taken at least 1/4 T from the nearest surface and at least T or 100 mm, whichever is less, from any second surface. For welded components, the testing shall also include testing of the welds in accordance with Appendix C.

3) Internal and external surface refers to the surfaces of the finished component.4) For Tees and Wyes both main run and branch weld necks shall be tested.5) The notch shall be perpendicular to the component's surface.6) Only applicable to C-Mn and low alloy steel. The section thickness is in the radial direction in the as-heat treated condition.7) A minimum of 3 hardness measurements shall be taken on each sample.8) Only applicable for rolled C-Mn steels not meeting the requirements in C200.9) Only applicable for 25Cr duplex steels.

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203 Specimens for hardness testing shall be examined, priorto testing, at a magnification of not less than x100. Grain-sizemeasurement shall be performed in accordance with ASTME112. The type of microstructure and actual grain size shall berecorded on the materials testing report.

E 300 Acceptance criteria for duplex stainless steels301 Tensile, hardness and Charpy V-notch impact propertiesshall meet the requirements for linepipe as given in Sec.7, C400.302 The metallographic samples shall comply with therequirements of Sec.7 C400.303 For ASTM G48 testing the acceptance criteria is: maxi-mum allowable weight loss 4.0 g/m2.

F. Fabrication of Risers, Expansion Loops, Pipe Strings for Reeling and Towing

F 100 General101 The following requirements are applicable for the fabri-cation of risers, expansion loops, pipe strings etc. 102 The fabrication shall be performed according to a speci-fication giving the requirements for fabrication methods, pro-cedures, extent of testing, acceptance criteria and requireddocumentation. The specification shall be subject to agreementprior to start of production.

F 200 Materials for risers, expansion loops, pipe strings for reeling and towing201 Linepipe shall comply with the requirements, includingsupplementary requirements (as applicable) given in Sec.7.202 Forged and cast material shall as a minimum meet therequirements given in this section.

F 300 Fabrication procedures and planning301 Before production commences, the fabricator shall pre-pare an MPS.302 The MPS shall demonstrate how the fabrication will beperformed and verified through the proposed Fabricationsteps. The MPS shall address all factors which influence thequality and reliability of production. All main fabrication stepsfrom control of received material to shipment of the finishedproduct(s), including all examination and check points, shallbe covered in detail. References to the procedures and accept-ance criteria established for the execution of all steps shall beincluded.303 The MPS shall, as a minimum, contain the followinginformation:

— plan(s) and process flow description/diagram— project specific quality plan including supply of material

and subcontracts— fabrication processes used— supply of material, i.e. manufacturer and manufacturing

location of material— fabrication processes— fabrication process procedures— fabrication process control procedures— welding procedures— heat treatment procedures— NDT procedures— pressure test procedures— list of specified mechanical and corrosion testing— dimensional control procedures— marking, coating and protection procedures and— handling, loading and shipping procedures.

304 The MPS shall be submitted for acceptance prior to start

of fabrication305 Due consideration shall be given to the access and timerequired for adequate inspection and testing as fabrication pro-ceeds.306 Due consideration during fabrication shall be given tothe control of weight and buoyancy distribution of pipe stringsfor towing. 307 The procedures prepared by the fabricator shall be sub-mitted for acceptance prior to start of fabrication.

F 400 Material receipt, identification and tracking401 All material shall be inspected for damage upon arrival.Quantities and identification of the material shall be verified.Damaged items shall be clearly marked, segregated and dis-posed of properly.402 Pipes shall be inspected for loose material, debris, andother contamination, and shall be cleaned internally beforebeing added to the assembly. The cleaning method shall notcause damage to any internal coating.403 A system for ensuring correct installation of materialsand their traceability to the material certificates shall be estab-lished. The identification of material shall be preserved duringhandling, storage and all fabrication activities.404 A pipe tracking system shall be used to maintain recordsof weld numbers, NDT, pipe numbers, pipe lengths, bends,cumulative length, anode installation, in-line assemblies andrepair numbers. The system shall be capable of detectingduplicate records.405 The individual pipes of pipe strings shall be marked inaccordance with the established pipe tracking system using asuitable marine paint. The location, size and colour of themarking shall be suitable for reading by ROV during installa-tion. It may be required to mark a band on top of the pipe stringto verify if any rotation has occurred during installation.406 If damaged pipes or other items are replaced, thesequential marking shall be maintained.

F 500 Cutting, forming, assembly, welding and heat treatment501 The Contractor shall be capable of producing weldedjoints of the required quality. This may include welding ofgirth welds, other welds, overlay welding and post weld heattreatment. Relevant documentation of the Contractor's capabil-ities shall be available if requested by the Purchaser.502 Attention shall be paid to local effects on material prop-erties and carbon contamination by thermal cutting. Preheatingof the area to be cut may be required. Carbon contaminationshall be removed by grinding off the affected material.503 Forming of material shall be according to agreed proce-dures specifying the successive steps.504 The fabrication and welding sequence shall be such thatthe amount of shrinkage, distortion and residual stress is mini-mised.505 Members to be welded shall be brought into correctalignment and held in position by clamps, other suitabledevices, or tack welds, until welding has progressed to a stagewhere the holding devices or tack welds can be removed with-out danger of distortion, shrinkage or cracking. Suitable allow-ances shall be made for distortion and shrinkage whereappropriate.506 Welding shall meet the requirements given inAppendix C.

F 600 Hydrostatic testing601 Hydrostatic testing shall be performed to establishedprocedures meeting the requirements of G100.

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F 700 NDT and visual examination701 All welds shall be subject to 100% visual inspection.702 Welds where the acceptance criteria are based on theacceptance criteria in Appendix D shall be subject to 100%radiographic or ultrasonic testing based on the requirements toapplicable and preferred NDT methods is given inAppendix D.703 For welds where allowable defect sizes are based on anECA, ultrasonic testing shall supplement radiographic testing,unless automated ultrasonic testing is performed704 Requirements to automated ultrasonic testing systemsare given in Appendix E.705 All NDT shall be performed after completion of all coldforming and heat treatment.706 Requirements for personnel, methods, equipment, proce-dures, and acceptance criteria for NDT are given in Appendix D.

F 800 Dimensional verification801 Dimensional verification should be performed in orderto establish conformance with the required dimensions and tol-erances.802 Dimensional verification of pipe strings for towing shallinclude weight, and the distribution of weight and buoyancy.

F 900 Corrosion protection901 Application of coatings and installation of anodes shallmeet the requirements of Sec.9.

G. Hydrostatic TestingG 100 Hydrostatic testing101 Prior to the performance of the pressure test the testobject shall be cleaned and gauged.102 The extent of the section to be tested shall be shown ondrawings or sketches. The limits of the test, temporary blindflanges, end closures and the location and elevation of test instru-ments and equipment shall be shown. The elevation of the testinstruments shall serve as a reference for the test pressure.103 End closures and other temporary testing equipmentshall be designed, fabricated, and tested to withstand the max-imum test pressure, and in accordance with a recognised code.104 Testing should not be performed against in-line valves,unless possible leakage and damage to the valve is considered,and the valve is designed and tested for the pressure test con-dition. Blocking off or removal of small-bore branches andinstrument tappings should be considered in order to avoidpossible contamination. Considerations shall be given to pre-filling valve body cavitieswith an inert liquid unless the valves have provisions for pres-sure equalisation across the valve seats.105 Welds shall not be coated, painted or covered. Thinprimer coatings may be used where agreed.106 Instruments and test equipment used for measurement ofpressure, volume, and temperature shall be calibrated for accu-racy, repeatability, and sensitivity. All instruments and testequipment shall possess valid calibration certificates withtraceability to reference standards within the 6 months preced-ing the test. If the instruments and test equipment have been infrequent use, they should be calibrated specifically for the test.107 Gauges and recorders shall be checked for correct func-tion immediately before each test. All test equipment shall belocated in a safe position outside the test boundary area.108 The following requirements apply for instruments andtest equipment:

— Testers shall have a range of minimum 1.25 times thespecified test pressure, with an accuracy better than ± 0.1bar and a sensitivity better than 0.05 bar.

— Temperature-measuring instruments and recorders shallhave an accuracy better than ± 1.0°C, and

— Pressure and temperature recorders are to be used to pro-vide a graphical record of the pressure test for the totalduration of the test.

109 Where the test acceptance is to be based on observationof pressure variations calculations showing the effect of tem-perature changes on the test pressure shall be developed priorto starting the test. Temperature measuring devices, if used,shall be positioned close to the test object and the distancebetween the devices shall be based on temperature gradientsalong the test object.110 The test medium should be fresh water or adequatelytreated sea water, as applicable. Filling procedure shall ensureminimum air pockets.111 Pressurisation shall be performed as a controlled opera-tion with consideration for maximum allowable velocities inthe inlet piping up to 95% of the test pressure. The final 5% upto the test pressure shall be raised at a reduced rate to ensurethat the test pressure is not exceeded. Time shall be allowed forconfirmation of temperature and pressure stabilisation beforethe test hold period begins.112 The test pressure shall be according to the specifiedrequirement.113 Where the test acceptance is to be based on 100% visualinspection the holding time at test pressure shall be until 100%visual inspection is complete or 2 hours, whichever is longer.Where the test acceptance is to be based on pressure observationthe holding time at test pressure shall be not less than 2 hours.114 During testing, all welds, flanges, mechanical connec-tors etc. under pressure shall be visually inspected for leaks.115 The pressure test shall be acceptable if:

— During a 100% visual inspection there are no observedleaks and the pressure has at no time during the hold periodfallen below 99% of the test pressure. 100% visual inspec-tion shall only be acceptable where there is no risk that aleak may go undetected due to prevailing environmentalconditions, or

— The test pressure profile over the test hold period is con-sistent with the predicted pressure profile taking intoaccount variations in temperatures and other environmen-tal changes.

116 Documentation produced in connection with the pres-sure testing shall, where relevant, include:

— Test drawings or sketches— pressure and temperature recorder charts— log of pressure and temperatures— calibration certificates for instruments and test equipment— calculation of pressure and temperature relationship and

justification for acceptance.

G 200 Alternative test pressures201 For components fitted with pup pieces of material iden-tical to the adjoining pipeline, the test pressure can be reducedto a pressure that produce an equivalent stress of 96% ofSMYS in the pup piece. 202 If the alternative test pressure in G201 can not be usedand the strength of the pup piece is not sufficient:

— Testing shall be performed prior to welding of pup pieces.The weld between component and pup piece is regarded apipeline weld and will be tested during pipeline systemtesting.

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H. Documentation, Records, Certification and Marking

H 100 General101 All base material, fittings and, flanges, etc. shall bedelivered with Inspection Certificate 3.1 according to Euro-pean Standard EN 10204 or accepted equivalent.The inspection certificate shall include:

— identification the products covered by the certificate withreference to heat number, heat treatment batch etc.

— dimensions and weights of products— the results (or reference to the results) of all specified

inspections and tests— the supply condition and the temperature of the final heat

treatment.

102 Records from the qualification of the MPS and otherdocumentation shall be in accordance with Sec.12.103 Each equipment or component item shall be adequatelyand uniquely marked for identification. The marking shall, asa minimum, provide correlation of the product with the relatedinspection documentation.104 The marking shall be such that it easily will be identi-fied, and retained during the subsequent activities.105 Other markings required for identification may berequired.106 Equipment and components shall be adequately pro-tected from harmful deterioration from the time of manufac-ture until taken into use.

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SECTION 9CONSTRUCTION - CORROSION PROTECTION AND WEIGHT COATING

A. GeneralA 100 Objective101 This section gives requirements and guidelines on:

— manufacture (application) of external pipeline coatingsincluding field joint coatings

— manufacture (application) of concrete weight coatings— manufacture of galvanic anodes— installation of galvanic anodes.

102 The objectives are to ensure that the external corrosioncontrol system and any weight coating are manufactured andinstalled to provide their function for the design life of the sys-tems. As to the last item above, it is a further objective toensure that the fastening does not impose any damage or haz-ards affecting the integrity of the pipeline system.

A 200 Application201 This section is applicable to the preparation of specifica-tions for manufacture and installation of external corrosioncontrol systems and for the manufacture of concrete weightcoating during the construction phase. Such specificationsshall define the requirements to properties of the coatings andanodes, and to the associated quality control.202 Manufacture and installation of any impressed currentCP systems for landfalls is not covered by this standard. Therequirements in ISO 15589-1 shall then apply.

B. External Corrosion Protective CoatingsB 100 General101 Properties of the coating (as-applied) and requirementsto quality control during manufacture shall be defined in a pur-chase specification. DNV-RP-F106 and DNV-RP-F102 givedetailed requirements and recommendations to the manufac-ture of linepipe coatings and field joint coating, respectively,with emphasis on quality control procedures. DNV-RP-F102also covers field repairs of linepipe coating. These documentsare applicable to the preparation of coating specifications andcan also be used as a purchase document if amended to includeproject and any owner specific requirements.102 The design and quality control during manufacture offield joint coatings is essential to the integrity of pipelines inHISC susceptible materials, including ferritic-austenitic(duplex) and martensitic stainless steel. Compliance withDNV-RP-F102 is recommended.

B 200 Coating materials, surface preparation, coating application and inspection/testing of coating201 All coating work shall be carried out according to aproject specific “manufacturing procedure specification”(MPS, also referred to as “application procedure specifica-tion”). The following items shall be described in the procedurespecification:

— receipt, handling and storage of coating materials— surface preparation and inspection — coating application and monitoring of essential process

parameters— inspection and testing of coating— coating repairs and stripping of defect coating— preparation of cut-backs (for linepipe coating)

— marking, traceability and handling of non-conformities — handling and storage of coated pipes (for linepipe coating) — documentation.

Material data sheets for coating, blasting and any other surfacepreparation materials may either be included in the MPS or ina separate document. The purchaser may specify that the abovedocumentation shall be submitted for approval prior to the startof production and any PQT (see B202).202 A coating pre-production qualification test (PQT; alsoreferred to as an “application procedure qualification test”,“procedure qualification trial” or “pre-production trial”)should be executed and accepted by the purchaser before start-ing the coating work, especially for coating systems which relyon a curing process to achieve the specified properties. Thepurpose of the qualification is to confirm, prior to the start ofregular production, that the coating manufacturing procedurespecification (MPS), coating materials, tools/equipment andpersonnel to be used for production are adequate to achieve thespecified properties of the coating. 203 An inspection and testing plan (ITP; sometimes referredto as an “inspection plan” or “quality plan”) shall be preparedand submitted to the purchaser for acceptance. The ITP shallrefer to the individual manufacturing and inspection/testingactivities in consecutive order, define methods/standards, fre-quency of inspection/testing, checking/calibrations, andacceptance criteria. Reference shall be made to applicable pro-cedures for inspection, testing and calibrations. 204 Inspection and testing data, essential process parame-ters, repairs and checking/calibrations of equipment for qualitycontrol shall be recorded in a “daily log” that shall be updatedon a daily basis and be available to the purchaser on request atany time during coating production.

C. Concrete Weight CoatingC 100 General101 The objectives of a concrete weight coating are to pro-vide negative buoyancy to the pipeline, and to providemechanical protection of the corrosion coating during installa-tion and throughout the pipeline's operational life.102 Requirements to raw materials (cement, aggregates,water, additives, reinforcement), and coating properties (func-tional requirements) shall be defined in a purchase specifica-tion. The following coating properties may be specified asapplicable:

— submerged weight/negative buoyancy— thickness— concrete density— compressive strength— water absorption— impact resistance (e.g. over-trawling capability)— flexibility (bending resistance), and— cutbacks.

Recommended minimum requirements to some of the aboveproperties are given in C202 below. Some general require-ments to steel reinforcement are recommended in C203 andC204. Project specific requirements to quality control (includ-ing pipe tracking and documentation) and marking shall alsobe described in the purchase documentation.

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C 200 Concrete materials and coating manufacture201 All coating work shall be carried out according to a man-ufacturing procedure specification (MPS). The followingitems shall be described:

— coating materials, including receipt, handling and storage— reinforcement design and installation— coating application and curing— inspection and testing, including calibrations of equipment— coating repairs (see F209)— pipe tracking, marking and coating documentation— handling and storage of coated pipes.

The purchaser may specify that the MPS shall be subject toapproval prior to start of production and any PQT.Before starting coating production, the coating manufacturershall document that the materials, procedures and equipment tobe used are capable of producing a coating of specified prop-erties. The purchaser may specify a pre-production qualifica-tion test for documentation of certain properties such as impactresistance and flexibility (bending strength).202 The concrete constituents and manufacturing methodshall provide the following recommended minimum require-ments to as-applied coating properties:

— minimum thickness: 40 mm— minimum compressive strength (i.e. average of 3 core

specimens per pipe): 40 MPa (ASTM C39)— maximum water absorption: 8% (by volume), (testing of

coated pipe according to agreed method), and— minimum density: 1900 kg/m3 (ASTM C642).

203 The concrete coating shall be reinforced by steel barswelded to cages or by wire mesh steel. The following recom-mendations apply: For welded cages, the spacing between cir-cumferential bars should be maximum 120 mm. Steel barsshould have a diameter of 6 mm minimum. The average per-centage of steel to concrete surface area in circumferentialdirection and longitudinal direction sections should be mini-mum 0.5% and 0.08%, respectively.204 When a single layer of reinforcement is used, it shall belocated within the middle third of the concrete coating. Therecommended minimum distance from the corrosion protec-tive coating is 15 mm, whilst the recommended minimum cov-erage is 15 mm and 20 mm for coatings with specifiedminimum thickness ≤ 50 mm and > 50 mm respectively. Over-lap for wire mesh reinforcement should be minimum 25 mm.Electrical contact with anodes for CP shall be avoided.205 The concrete may be applied according to one of the fol-lowing methods:

— impingement application— compression coating— slip forming.

206 Rebound or recycled concrete may be used provided it isdocumented that specified properties are met and the purchaserhas accepted.207 The curing method shall take into account any adverseclimatic conditions. The curing process should ensure no sig-nificant moisture loss for 7 days and/or a minimum compres-sive strength of 15 MPa.208 Procedures for repair of uncured / cured coatings anddetailed criteria for repairs (e.g. max repair areas for differenttypes of coating damage) shall be subject to agreement. As aminimum, all areas with exposed reinforcement shall berepaired. Pipes with deficient coating exceeding 10% of thetotal coating surface shall be recoated, unless otherwise

agreed.

C 300 Inspection and testing301 An inspection and testing plan (ITP) shall be preparedand submitted to the purchaser for acceptance in due time priorto start of production. The plan shall define the methods andfrequency of inspection, testing and calibrations, acceptancecriteria and requirements to documentation. Reference shall bemade to applicable specifications and procedures for inspec-tion, testing and calibration. Handling of non-conforming coat-ing materials and as-applied coating shall be described.302 Inspection shall include weighing and measurements ofoutside concrete diameter for each individual pipe. The pur-chaser may further specify seawater adsorption tests after com-pleted curing and compression tests of core samples fromapplied coatings. Acceptance criteria for all inspection andtesting shall be subject to agreement.303 Inspection and testing data, repairs, essential processparameters and calibrations of equipment for quality controlshall be recorded in a “daily log” that shall be updated on adaily basis and be available to the purchaser on request at anytime during coating production.

D. Manufacture of Galvanic Anodes

D 100 Anode manufacture101 Requirements to anode manufacture shall be detailed ina purchase specification (‘anode manufacturing specifica-tion’). A manufacturing specification for pipeline braceletanodes shall cover all requirements in ISO 15589-2. DNV-RP-F103 refers to this document for anode manufacture and givessome additional requirements and guidance, primarily for pro-cedures and documentation associated with quality control.The manufacturer of bracelet anodes shall prepare a ‘manufac-turing procedure specification’ (MPS) describing anode alloy(e.g. limits for alloying and impurity elements) and anode corematerials, anode core preparations, anode casting, inspectionand testing, coating of bracelet anode surfaces facing the pipesurface, marking and handling of anodes, and documentation. 102 An “Inspection and Testing Plan” (ITP) for manufactureof bracelet anodes, shall be prepared and submitted to the pur-chaser for acceptance. It is further recommended that theinspection and testing results are compiled in a ‘daily log’.Requirements and guidance for preparation of these docu-ments and to a ‘pre-production qualification test’ are given inDNV-RP-F103. For manufacturing of other types of anodesthan pipeline bracelet anodes, reference is made to DNV-RP-B401.

Guidance note:The requirement for an ITP is an amendment to ISO 15589-2.


103 For each anode type/size, the manufacturer shall preparea detailed drawing showing location and dimensions of anodeinserts, anode gross weight and other details as specified in apurchase document104 A procedure for electrochemical testing of anode materialperformance during anode manufacturing is given in AppendixA of DNV-RP-B401 and in Annex D of ISO 15589-2.105 Marking of anodes shall ensure traceability to heatnumber. Anodes should be delivered according to ISO 10474,Inspection Certificate 3.1.B or EN 10204, Inspection Certifi-cate 3.1.

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E. Installation of Galvanic AnodesE 100 Anode installation101 Installation of anodes shall meet the requirements in ISO15589-2. DNV RP-F103 gives some additional requirementsand guidelines, primarily for quality control.102 For martensitic and ferritic-austenitic (duplex) stainlesssteels and for other steels with SMYS > 450 MPa, no weldingfor anode fastening (including installation of doubling plates)shall be carried out on linepipe or other pressure containingcomponents, unless specified by or agreed with the pipelineowner.

Guidance note:Guidance note: The requirement above is an amendment to ISO15589-2. Most CP related HISC damage to pipeline componentsin CRA’s have occurred at welded connections of galvanicanodes to the pipe walls. To secure adequate fastening of pipelinebracelet anodes for compatibility with the applicable installationtechniques, forced clamping of anodes is applicable in combina-

tion with electrical cables attached to anodes and pipeline bybrazing. However, for many applications, CP can be provided byanodes attached to other structures electrically connected to thepipeline (see Sec.6 D500). For installation of anodes on suchstructures, reference is made to DNV-RP-B401.


103 All welding or brazing of anode fastening devices andconnector cables shall be carried out according to a qualifiedprocedure (see Appendix C of this standard) to demonstratethat the requirements in ISO 13847 to maximum hardness(welding/brazing) and copper penetration (brazing including‘aluminothermic welding’) are met. 104 For linepipe to be concrete weight coated, electrical con-tact between concrete reinforcement and the anodes shall beavoided. The gaps between the anode half shells may be filledwith asphalt mastic, polyurethane or similar. Any spillage offilling compound on the external anode surfaces shall beremoved.

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SECTION 10CONSTRUCTION - INSTALLATION

A. GeneralA 100 Objective101 This section provides requirements as to which analyses,studies and documentation shall be prepared and agreed for theinstallation, and further to provide requirements for the instal-lation and testing of the complete pipeline system which arenot covered elsewhere in the standard.

A 200 Application201 This section is applicable to installation and testing ofpipelines and rigid risers designed and manufactured accord-ing to this standard.

A 300 Failure Mode Effect Analysis (FMEA) and Haz-ard and Operability (HAZOP) studies301 Systematic analyses of equipment and installation oper-ations shall be performed in order to identify possible criticalitems or activities which could cause or aggravate a hazardouscondition, and to ensure that effective remedial measures aretaken. Reference is given to DNV-RP-H101 Risk Managementin Marine and Subsea Operations. 302 The extent of analysis shall reflect the criticality of theoperations and the extent of experience available from previ-ous similar operations. The systematic analyses should be car-ried out as a failure mode effect analysis (FMEA) and hazardand operability studies (HAZOP). For FMEA, reference ismade to DNV Rules for Classification of High Speed, andLight Craft and Naval Surface Craft, Pt.0 Ch.4 Sec.2.303 Special attention shall be given to sections of the pipe-line route close to other installations or shore approacheswhere there is greater risk of interference from shipping,anchoring etc. For critical operations, procedural HAZOPstudies shall be performed.

A 400 Installation and testing specifications and draw-ings401 Specifications and drawings shall be prepared coveringinstallation and testing of pipeline systems, risers, protectivestructures etc.402 The specifications and drawings shall describe, in suffi-cient detail, requirements to installation methods and the proc-esses to be employed and to the final result of the operations.403 The requirements shall reflect the basis for, and theresults of, the design activities. The type and extent of verifi-cation, testing, acceptance criteria and associated documenta-tion required to verify that the properties and integrity of thepipeline system meet the requirements of this standard, as wellas the extent and type of documentation, records and certifica-tion required, shall be stated.404 Requirements to the installation manual and the extentof tests, investigations and acceptance criteria required forqualification of the installation manual shall be included.

A 500 Installation manuals501 Installation manuals shall be prepared by the variousContractors.502 The installation manual is a collection of the manualsand procedures relevant to the specific work to be performed.It is prepared in order to demonstrate that the methods andequipment used by the Contractor will meet the specifiedrequirements, and that the results can be verified. The installa-tion manual shall include all factors that influence the quality

and reliability of the installation work, including normal andcontingency situations, and shall address all installation steps,including examinations and check points. The manual shallreflect the results of the FMEA analysis or HAZOP studies,and shall state requirements for the parameters to be controlledand the allowable range of parameter variation during theinstallation.The following shall, as a minimum, be covered:

— quality system manual— mobilisation manual— construction manual— health, safety and environment manual— emergency preparedness manual.

The manuals should include:

— interface description— organisation, responsibilities and communication— description of and commissioning procedures for the

equipment and systems involved in the operation— limitations and conditions imposed by structural strength

in accordance with the design— limitations on operations imposed by environmental con-

ditions— references to the established operational and contingency

procedures.

503 The Contractor shall prepare procedures covering nor-mal and contingency situations. The procedures shall describe:

— purpose and scope of the activity— responsibilities— materials, equipment and documents to be used— how the activity is performed in order to meet specified

requirements— how the activity is controlled and documented.

504 The installation manual shall be updated/revised asneeded as installation proceeds.505 The installation manuals are subject to agreementthrough:

— review of methods, procedures and calculations— review and qualification of procedures— qualification of vessels and equipment— review of personnel qualifications.

506 Requirements to the installation manual and acceptanceare given in the various subsections. The results of the FMEAanalysis or HAZOP studies (see A300) shall also be used indetermining the extent and depth of verification of equipmentand procedures.507 In cases where variations in manner of performance ofan activity may give undesirable results, the essential variablesand their acceptable limits shall be established.

A 600 Quality assurance601 The installation Contractor shall as a minimum have animplemented quality assurance system meeting the require-ments of ISO 9001 Quality management systems – Require-ments or equivalent. Further requirements for qualityassurance are given in Sec.2 B500.

A 700 Welding701 Requirements for welding processes, welding procedurequalification, execution of welding and welding personnel are

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given in Appendix C.702 Requirements for mechanical and corrosion testing forqualification of welding procedures are given in Appendix B.703 The mechanical properties and corrosion resistance ofweldments shall at least meet the requirements given in theinstallation and testing specifications.704 For weld repair at weld repair stations where the pipelinesection under repair is subjected to tensile and bendingstresses, a weld repair analysis shall be performed. The analy-sis shall determine the maximum excavation length and depthcombinations that may be performed, taking into account allstresses acting at the area of the repair. The analysis shall beperformed in accordance with Appendix A.The analysis shall consider the reduction of yield and tensilestrength in the material due to the heat input from defect exca-vation, preheating, and welding and also dynamic amplifica-tion due to weather conditions and reduced stiffness effect atfield joints. 705 The weld repair analysis shall be subject to agreement.706 The root and the first filler pass shall, as a minimum, becompleted at the first welding station before moving the pipe.Moving the pipe at an earlier stage may be permitted if an anal-ysis is performed showing that this can be performed withoutany risk of introducing damage to the deposited weld material.This analysis shall consider the maximum misalignmentallowed, the height of the deposited weld metal, the possiblepresence of flaws, support conditions for the pipe and anydynamic effects.

A 800 Non-destructive testing and visual examination801 Requirements for methods, equipment, procedures,acceptance criteria and the qualification and certification ofpersonnel for visual examination and non-destructive testing(NDT) are given in Appendix D. Selection of non-destructivemethods shall consider the requirements in Appendix D, A400.802 Requirements to automated ultrasonic testing (AUT) aregiven in Appendix E.803 The extent of NDT for installation girth welds shall be100% ultrasonic or radiographic testing. Radiographic testingshould be supplemented with ultrasonic testing in order toenhance the probability of detection and/or characterisation/sizing of defects.804 For wall thickness > 25 mm, automated ultrasonic test-ing should be used.805 Ultrasonic testing (UT) shall be used in the followingcases:

— UT or automated ultrasonic testing (AUT) shall be per-formed whenever sizing of flaw height and/or determina-tion of the flaw depth is required

— 100% testing of the first 10 welds for welding processeswith high potential for non-fusion type defects, when start-ing installation or when resuming production after suspen-sion of welding and when radiographic testing is theprimary NDT method. For wall thickness above 25 mmadditional random local spot checks during installation arerecommended

— testing to supplement radiographic testing for wall thick-ness above 25 mm, to aid in characterising and sizing ofambiguous indications

— testing to supplement radiographic testing for unfavoura-ble groove configurations, to aid in detection of defects

— 100% lamination checks of a 50 mm wide band at ends ofcut pipe.

806 If ultrasonic testing reveals defects not discovered byradiography, the extent of ultrasonic testing shall be 100% forthe next 10 welds. If the results of this extended testing areunsatisfactory, the welding shall be suspended until the causes

of the defects have been established and rectified.807 For "Golden Welds" (critical welds e.g. tie-in welds thatwill not be subject to pressure testing, etc.) 100% ultrasonictesting, 100% radiographic testing, and 100% magnetic parti-cle testing or 100% liquid penetrant testing of non- ferromag-netic materials shall be performed. If the ultrasonic testing isperformed as automated ultrasonic testing, see Appendix E,the radiographic and magnetic particle/liquid penetrant testingmay be omitted subject to agreement.808 Magnetic particle testing or liquid penetrant testing ofnon-ferromagnetic materials shall be performed to verify com-plete removal of defects before commencing weld repairs, andfor 100% lamination checks at re-bevelled ends of cut pipe.809 Visual Examination shall include:

— 100% examination of completed welds for surface flaws,shape and dimensions

— 100% examination of the visible pipe surface, prior to fieldjoint coating

— 100% examination of completed field joint coating.

A 900 Production tests901 One production test is required for each Welding Proce-dure Specification (WPS) used for welding of the pipelinegirth welds.902 Production tests should not be required for welding pro-cedures qualified specifically for tie-in welds, flange welds,Tee-piece welds etc.903 Production tests may, subject to agreement, be omittedin cases where fracture toughness testing during welding pro-cedure qualification is not required by this standard, or for C-Mn steel linepipe with SMYS < 450 MPa.904 The extent of production tests shall be expanded if:

— the Contractor has limited previous experience with thewelding equipment and welding methods used

— the welding inspection performed is found to be inade-quate

— severe defects occur repeatedly— any other incident indicates inadequate welding perform-

ance— the installed pipeline is not subjected to system pressure

testing, see Sec.5 B203.

905 The extent of production testing shall be consistent withthe inspection and test regime and philosophy of the pipelineproject.906 Production tests shall be subject to the non-destructive,all weld tensile, Charpy V-notch fracture toughness (whenapplicable) and corrosion testing as required in Appendix C forWelding Procedure Qualification Testing (WPQT).907 If production tests show unacceptable results, appropri-ate corrective and preventative actions shall be initiated andthe extent of production testing shall be increased.

B. Pipeline Route, Survey and PreparationB 100 Pre-installation route survey101 A pre-installation survey of the pipeline route may berequired in addition to the route survey required for design pur-poses covered by Sec.3 if:

— the time elapsed since the previous survey is significant— a change in seabed conditions is likely to have occurred— the route is in areas with heavy marine activity— new installations are present in the area— seabed preparation work is performed within the route cor-

ridor after previous survey.

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102 The pre-installation survey, if required, shall determine:

— potential new/previously not identified hazards to thepipeline and the installation operations

— location of wrecks, submarine installations and otherobstructions such as mines, debris, rocks and boulders thatmight interfere with, or impose restrictions on, the instal-lation operations

— that the present seabed conditions confirm those of the sur-vey required in Sec.3

— any other potential hazards due to the nature of the suc-ceeding operations.

103 The extent of, and the requirements for, the pre-installa-tion route survey shall be specified.

B 200 Seabed preparation201 Seabed preparation may be required to:

— remove obstacles and potential hazards interfering withthe installation operations

— prevent loads or strains that occur as a result of seabedconditions such as unstable slopes, sand waves, deep val-leys and possible erosion and scour from exceeding thedesign criteria

— prepare for pipeline and cable crossings— infill depressions and remove high-spots to prevent unac-

ceptable free spans— carry out any other preparation due to the nature of the suc-

ceeding operations.

202 Where trench excavation is required before pipelaying,the trench cross-section shall be specified and the trench shallbe excavated to a sufficiently smooth profile to minimise thepossibility of damages to the pipeline, coating and anodes.203 The extent of, and the requirements for, seabed prepara-tion shall be specified. The laying tolerances shall be consid-ered when the extent of seabed preparation is determined.

B 300 Pipeline and cable crossings301 Preparations for crossing of pipelines and cables shall becarried out according to a specification detailing the measuresadopted to avoid damage to both installations. The operationsshould be monitored by ROV to confirm proper placement andconfiguration of the supports. Support and profile over the exist-ing installation shall be in accordance with the accepted design.302 The specification shall state requirements concerning:

— minimum separation between existing installation and thepipeline

— co-ordinates of crossing— marking of existing installation— confirmation of position and orientation of existing instal-

lations on both sides of the crossing— lay-out and profile of crossing— vessel anchoring— installation of supporting structures or gravel beds— methods to prevent scour and erosion around supports— monitoring and inspection methods— tolerance requirements— any other requirements.

B 400 Preparations for shore approach401 The location of any other pipelines, cables or outfalls inthe area of the shore approach shall be identified and clearlymarked.402 Obstructions such as debris, rocks and boulders thatmight interfere with or restrict the installation operations shallbe removed. The seabed and shore area shall be prepared to thestate assumed in the design such that over-stressing in the pipe-line during the installation and damage to coating or anodes isavoided.

C. Marine OperationsC 100 General101 These requirements are applicable for vessels perform-ing pipeline and riser installation and supporting operations.The requirements are applicable for the marine operations dur-ing installation work only. Specific requirements for installa-tion equipment onboard vessels performing installationoperations are given in the relevant subsections.102 The organisation of key personnel with defined respon-sibilities and lines of communication shall be established priorto start of the operations. Interfaces with other parties shall bedefined.103 All personnel shall be qualified for their assigned work.Key personnel shall have sufficient verbal communicationskills in the common language used during operations.104 Manning level should comply with IMO's Principles ofSafe Manning (IMO 23rd Session 2003 (Res. 936-965))"Prin-ciples of Safe Manning". Non-propelled vessels shall havesimilar manning and organisation as required for propelledunits of same type and size.

C 200 Vessels201 All vessels shall have valid class with a recognised clas-sification society. The valid class shall cover all systems ofimportance for the safety of the operation. Further require-ments to vessels shall be given in a specification statingrequirements for:

— anchors, anchor lines and anchor winches— anchoring systems— positioning and survey equipment— dynamic positioning equipment and reference system— alarm systems, including remote alarms when required— general seaworthiness of the vessel for the region— cranes and lifting appliances— pipeline installation equipment (see. D)— any other requirement due to the nature of the operations.

202 Vessels shall have a documented maintenance pro-gramme covering all systems vital for the safety and opera-tional performance of the vessel, related to the operation to beperformed. The maintenance programme shall be presented ina maintenance manual or similar document.203 Status reports for any recommendations or requirementsgiven by National Authorities and/or classification societies,and status of all maintenance completed in relation to the main-tenance planned for a relevant period, shall be available forreview.204 An inspection or survey shall be performed prior tomobilisation of the vessels to confirm that the vessels and theirprincipal equipment meet the specified requirements and aresuitable for the intended work.

C 300 Anchoring systems, anchor patterns and anchor positioning301 Anchoring systems for vessels kept in position byanchors (with or without thruster assistance) while performingmarine operations shall meet the following requirements:

— instruments for reading anchor line tension and length ofanchor lines shall be fitted in the operations control roomor on the bridge, and also at the winch station

— remotely operated winches shall be monitored from thecontrol room or bridge, by means of cameras or equiva-lent.

302 Anchor patterns shall be predetermined for each vesselusing anchors to maintain position. Different configurationsfor anchor patterns may be required for various sections of the

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pipeline, especially in the vicinity of fixed installations andother subsea installations or other pipelines or cables.303 Anchor patterns shall be according to the results of amooring analysis, using an agreed computer program, andshall be verified to have the required capacity for the proposedlocation, time of year and duration of operation. Distance toother installations and the possibility to leave the site in anemergency situation shall be considered.304 Station-keeping systems based on anchoring shall haveadequate redundancy or back-up systems in order to ensurethat other vessels and installations are not endangered by par-tial failure.305 Each anchor pattern shall be clearly shown on a chart ofadequate scale. Care shall be taken in correlating differentchart datum, if used.306 Minimum clearances are to be specified between ananchor, its cable and any existing fixed or subsea installationsor other pipelines or cables, both for normal operations andemergency conditions.

C 400 Positioning systems401 Requirements for the positioning system and its accu-racy for each type of vessel and application shall be specified.402 The accuracy of horizontal surface positioning systemsshall be consistent with the accuracy required for the operationand sufficient to perform survey work, placing of the pipeline,supporting structures or anchors within the specified toler-ances, and to establish reference points for local positioningsystems.403 Installation in congested areas and work requiring preciserelative location may require local systems of greater accuracy,such as acoustic transponder array systems. Use of ROV's tomonitor and assist the operations should be considered.404 The positioning system shall provide information relat-ing to:

— position relative to the grid reference system used— geographical position— offsets from given positions— offsets from antenna position— vertical reference datum(s).

405 Positioning systems shall have minimum 100% redun-dancy to allow for system errors or breakdown.406 Documentation showing that positioning systems arecalibrated and capable of operating within the specified limitsof accuracy shall be available for review prior to start of theinstallation operations.

C 500 Dynamic positioning501 Vessels using dynamic positioning systems for stationkeeping and location purposes shall be designed, equipped andoperated in accordance with IMO MSC/Circ.645 (Guidelinesfor Vessels with Dynamic Positioning Systems), or with earlierNMD requirements for consequence class, and shall have cor-responding class notations from a recognised classificationsociety as follows:

a) Vessels > 5 000 t displacement:

— Class 1 for operations > 500 m away from existinginstallations

— Class 3 for operations < 500 m away from existinginstallations and for tie-in/riser installation operations

— Class 3 for manned subsea operations or other opera-tions where a sudden horizontal displacement of thevessel may have fatal consequences for personnel.

b) Vessels < 5 000 t displacement:

— Class 1 for operations > 500 m away from existinginstallations,

— Class 2 for operations < 500 m away from existinginstallations and for tie-in/riser installation operations

— Class 3 for manned subsea operations or other opera-tions where a sudden horizontal displacement of thevessel may have fatal consequences for personnel.

502 Subject to agreement and on a case by case basis, vesselswith displacement > 5 000 t performing operations < 500 maway from existing installations or performing tie-in/riserinstallation operations may have Class 2 provided that the con-sequences of fire or flooding will not seriously affect the safetyof the installation or the integrity of the pipeline.

C 600 Cranes and lifting equipment601 Cranes and lifting equipment including lifting gear, lift-ing appliances, slings, grommets, shackles and pad-eyes, shallmeet applicable statutory requirements. Certificates for theequipment, valid for the operations and conditions underwhich they will be used, shall be available on board for review.

C 700 Anchor handling and tug management701 Anchor handling vessels shall be equipped with:

— a surface positioning system of sufficient accuracy foranchor drops in areas within 500 m of existing installa-tions and pipelines

— computing and interfacing facilities for interfacing withlay vessel, trenching vessel or other anchored vessels.

702 Procedures for the anchor handling shall be established,ensuring that:

— anchor locations are in compliance with the anchor patternfor the location

— requirements of owners of other installations and pipelinesfor anchor handling in the vicinity of the installation areknown, and communication lines established

— position prior to anchor drop is confirmed— anchor positions are monitored at all times, particularly in

the vicinity of other installations and pipelines— any other requirement due to the nature of the operations

is fulfilled.

703 All anchors transported over subsea installations shall besecured on deck of the anchor handling vessel.704 During anchor running, attention shall be paid to theanchor cable and the catenary of the cable, to maintain mini-mum clearance between the anchor cable and any subseainstallations or obstacles.

C 800 Contingency procedures801 Contingency procedures shall be established for themarine operations relating to:

— work site abandonment including emergency departure ofthe work location and when anchors cannot be recovered

— mooring systems failure— any other requirement due to the nature of the operations.

D. Pipeline InstallationD 100 General101 The requirements of this subsection are generally appli-cable to pipeline installation, regardless of installation method.Additional requirements pertaining to specific installationmethods are given in the following subsections.102 Interfaces shall be established with other parties thatmay be affected by the operations. The responsibilities of all

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parties and lines of communication shall be established.

D 200 Installation manual201 The laying Contractor shall prepare an installation man-ual. As a minimum, the installation manual shall include alldocumentation required to perform the installation, and shalldemonstrate that the pipeline can be safely installed and com-pleted to the specified requirements by use of the dedicatedspread.202 The installation manual shall cover all applicableaspects such as:

— spread, including modifications and upgrading, if any— supervisory personnel, inspectors, welders and NDT per-

sonnel— communications and reporting— navigation and positioning— anchor handling, anchor patterns and catenary curves (if

applicable)— dynamic positioning system (if applicable)— stress/strain and configuration monitoring, control, and

recording during all phases of installation activities— operating limit conditions— normal pipe-lay— anode installation (where applicable)— piggyback pipeline saddle installation (where applicable)— piggyback pipeline installation (where applicable)— pipe-lay in areas of particular concern, e.g. shipping lanes,

platforms, subsea installations, shore approach— vessel pull management system— abandonment and recovery— start-up and lay-down— method of buckle detection— installation of in-line assemblies and equipment— pipe handling, hauling, stacking and storage— maintaining pipeline cleanliness during construction— pipe tracking— repair of damaged pipe coating— internal coating repair— internal cleaning of pipe before and after welding— welder qualification— welding equipment, line-up clamps, bevelling procedures,

welding procedures, production welding, weld repair,welding production tests

— NDT equipment, visual examination and NDT proce-dures, visual examination and NDT of welds

— weld repair analysis extent of weld repair at repair station,determined by ECA (see A700)

— field joint coating and field joint coating repair— touchdown point monitoring— pipeline repair in case of wet or dry buckle— crossings— provisions for winter laying, prevention of ice build-up,

removal of ice, low temperature reservoirs in steel andconcrete coating, etc.

— vessel emergency bridging document describing co-ordi-nation of safety management systems between the vesselcontractor and the pipeline operator/licensee.

203 The installation manual shall be supported by calcula-tions and procedures, including contingency procedures, to anextent that adequately covers the work to be performed.

D 300 Review and qualification of the installation man-ual, essential variables and validity301 The review of methods, procedures and calculationsshall include:

— Failure mode effect analysis,— HAZOP studies,— installation procedures,— contingency procedures,

— engineering critical assessments for girth welds,— engineering critical assessments for weld repair lengths,— other calculations made as part of the installation scope.

302 Review and qualification of procedures shall as a mini-mum include:

— welding procedures for production and repair welding (seeAppendix C)

— non-destructive testing procedures and automated NDTequipment (see Appendix D, Appendix E)

— field joint coating and field joint coating repair procedures— internal and external coating repair procedures.

303 Qualification of vessels and equipment prior to start ofwork shall include:

— dynamic positioning system test— combined review and dynamic positioning system/ten-

sioner system tests (simulate vessel pull and tensioner fail-ures and redundancy tests during pull)

— tensioner system review test (test combinations of tension-ers, testing of single tensioner failure when running two orthree tensioners, test redundancy of single tensioners, sim-ulate main power loss and loss of signal power)

— abandonment and recovery winch test (fail safe actions,simulate main power loss and loss of signal power)

— friction clamp test (fail safe actions and test clamps duringvessel pull)

— remote operated buckle detector— pipeline support geometry— stinger configuration and control devices— review of calibration records of critical/essential equip-

ment, including welding machines and automated NDTequipment

— review of maintenance records for critical/essential equip-ment, including welding machines and automated NDTequipment

— maintenance/calibration records of critical/essentialequipment on support vessels.

304 Review of personnel qualifications shall include:

— welders qualification/certification records,— welding inspectors and QC personnel qualification/ certi-

fication records,— NDT operators qualification/certification records,— Lay barge survey party chief, and— Field coating personnel.

305 Records from vessel qualification, testing and calibra-tion shall be kept onboard and be available for review.306 Essential variables shall as minimum be established for:

— Allowable variations in stress/strain and configurationcontrol parameters where variations beyond establishedlimits may cause critical conditions during installation

— variations in equipment settings/performance that cancause or aggravate critical conditions

— changes in welding joint design and process parametersbeyond that allowed in Appendix C

— changes in NDT method, NDT equipment and NDTequipment calibration beyond that allowed in Appendix Dand Appendix E

— weld repair lengths/depths in areas where the pipe is sub-ject to bending moments/axial stress. The maximumlength/depth of excavation shall be determined by ECAcalculations (see A.704)

— changes in field joint coating procedure— operating limit conditions— any other requirement due to the nature of the operations.

307 The validity of the installation manual is limited to thelay-vessel/spread where the qualification was performed and

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to the pipeline or section of pipeline in question.

D 400 Operating limit conditions401 The installation operation shall be classified as weatherrestricted operation or temporary condition, see Sec.4 C600.402 For weather restricted operations, operating limit condi-tions shall be established and agreed.403 The operating limit conditions shall be based on stressand strain calculations, vessel station keeping capability,FMEA analysis or HAZOP study data, and shall refer to objec-tive, critical values indicated by measuring devices. The oper-ating limit conditions shall be referred to in the procedure forstress/strain and configuration control. Continuous monitoringand recording of the measuring devices required for control ofthe operating limit conditions shall be performed during allphases of installation activities.404 If a systematic deviation between the monitoredresponse and predicted response from a seastate is found thisshould be accounted for.405 Start of weather restricted operations is conditional to anacceptable weather forecast. 406 For weather restricted operations, planning of operationshall be based on an operational reference period. Further, theoperational criteria shall account for uncertainties in bothweather forecasts and monitoring of environmental conditions.Regular weather forecasts from a recognised meteorologicalcentre shall be available onboard the lay vessel, and shall besupplemented by historical environmental data. Reference ismade to DNV-OS-H101 Marine Operations (1).(1) This standard is not yet issued. Until issue, refer to:

— DNV Rules for planning and execution of marine Opera-tions, Pt. 1, Ch. 2, paragraph 3.1.

407 If the critical values are about to be exceeded, prepara-tions for lay-down shall commence. If the critical condition isweather dependent only, and if weather forecasts indicate thatthe weather condition will subside, the lay-down may be post-poned subject to agreement.408 Decision to recover the pipeline shall be based on com-parison of the actual seastate with the limiting seastate,together with weather forecasts.

D 500 Installation procedures501 Installation procedures meeting the requirements of thisstandard, including all requirements of the installation and test-ing specifications, shall be prepared by the Contractor foragreement.

D 600 Contingency procedures601 Contingency procedures meeting the requirements ofthis standard, including all requirements of the installation andtesting specifications, shall be prepared by the Contractor foragreement. The contingency procedures shall at least cover:

— failure of dynamic positioning system— failure of tensioner system

— failure of anchors and anchor lines— ROV breakdown— breakdown of positioning system— other critical or emergency situations identified in FMEA

analysis or HAZOP studies.

D 700 Layvessel arrangement, laying equipment and instrumentation701 The tensioners shall operate in a fail-safe mode and shallhave adequate pulling force, holding force, braking capacityand squeeze pressure to maintain the pipe under controlled ten-sion. The forces applied shall be controlled such that no dam-age to the pipeline or coating will occur.702 The installation vessel tensioning system arrangementshall therefore be such that:

— the tensioners, brakes and holding clamps shall be able tohold the pipeline throughout an accidental flooding, unlessit can be demonstrated that the flooded pipe can bereleased safely and without damage to the laying vesseland the risk of such a release is found acceptable

— the tensioning system shall have sufficient redundancy toprevent simultaneous breakdown of tensioners

— the tensioner capacity shall have sufficient redundancy toallow failure of individual tensioners, without compromis-ing the pipeline integrity

— in case of tensioner failure or failure in the tensioner sys-tem, the pipeline installation shall not re-start before thesystem has been repaired.

703 When applicable for the laying method, the pipelineshall be fully supported along the length of the vessel and onto the stinger by rollers, tracks or guides that allow the pipe tomove axially. Supports shall prevent damage to coating, fieldjoint coatings, anodes and in-line assemblies, and rollers shallmove freely. The vertical and horizontal adjustment of the sup-ports shall ensure a smooth transition from the vessel onto thestinger, to maintain the loading on the pipeline within the spec-ified limits. The support heights and spacing shall be related toa clear and easily identifiable datum. The pipeline supportgeometry shall be verified prior to laying, and the acceptedheight and spacing of supports shall be permanently marked orotherwise indicated.704 Stingers shall be adjusted to the correct configuration toensure a smooth transition from the vessel to the outboardstinger end, and to maintain the loading on the pipeline withinthe specified limits. The geometry shall be verified prior to lay-ing. If the stinger can be adjusted during laying operations, itshall be possible to determine the stinger position and config-uration by reference to position markings or indicators. Buoy-ant stingers shall be equipped with indication devices showingthe position of the rollers relative to the water surface.705 Buckle detection should normally be used continuouslyduring laying. The intention of the buckle detection is to iden-tify a buckle at an early stage. By adopting a higher safety classduring installation, the probability of a buckle event will bereduced, and subject to agreement, the guidance provided inTable 10-1below may be used.

Guidance note:The above implies, subject to agreement, that if buckle detection

is not used during laying a higher safety class may be applied.


Table 10-1 Safety class during installationBuckle detection requirement Additional requirements

Low Buckle detection required (e.g. by buckle detector or equip-ment providing similar degree of detection)

Medium Buckle detection not required Good control of installation parameters required (e.g. lay tension, touch down point etc.) and consequence of possible buckle is found acceptable

High Buckle detection not required Consequence of possible buckle is found acceptable

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Guidance note:The buckle detector (or equipment providing same degree ofdetect ability) shall be positioned in such a way that critical areasmonitored (normally a distance after the touch down point). If abuckle detector is used the diameter of the disc shall be chosenwith regard to the pipeline diameter and tolerances on ovality,wall thickness, misalignment and internal weld bead.


706 The abandonment and recovery (A & R) winch shouldbe able to recover the pipeline when waterfilled, or alternativemethods for recovering the pipeline should be available.707 A sufficient amount of instrumentation and measuringdevices shall be installed to ensure that monitoring of essentialequipment and all relevant parameters required for stress/strainand configuration control and control of the operating limitconditions can be performed.The following instrumentation is required:Tensioners:

— total pipeline tension recorders— tension at each tensioner— tensioner setting and variance to set point (dead band), and— indication of applied pulling, holding and squeeze pres-

sure.

Stinger:

— underwater camera(s) and video recorders for monitoringpipeline position with respect to the last roller on thestinger (if restricted underwater visibility is expected, asonar is required for monitoring pipeline position withrespect to the rollers on the stinger)

— reaction load indicators (vertical and horizontal) on thefirst roller on the stinger

— for installations that rely on a maximum force on the lastroller on the stinger this shall be monitored by reactionload indicators or documented by other means

— stinger configuration and tip depth for articulated stingers.

Buckle detector:

— pulling wire tension and length recorder, when applicable.

Winches:

— abandonment and recovery winches shall be equippedwith wire tension and length recorder

— anchor winches shall meet the requirements given inC300.

Vessel:

— vessel position— vessel movements such as roll, pitch, sway, heave— water depth— vessel draft and trim— current strength and direction— wind strength and direction— direct or indirect indication of sagbend curvature and

strain.

All measuring equipment shall be calibrated and adequate doc-umentation of calibration shall be available onboard the vesselprior to start of work. All measuring equipment used shall beprovided with an adequate amount of spares to ensure uninter-rupted operation.Essential equipment shall be provided with back-up.Direct reading and processing of records from all requiredessential instrumentation and measuring devices, shall be pos-sible at the vessels bridge.Correlation of recorded data and pipe numbers shall be possible.

708 Pipeline lay down point shall be monitored as well asother operations that are critical to the integrity of the pipelineor represent a risk for fixed installations or other subsea instal-lations and pipelines. ROVs shall be capable of operatingunder the seastates expected for the operation in question.709 Other measuring and recording systems or equipmentshall be required if they are essential for the installation oper-ation.

D 800 Requirements for installation801 Handling and storage of materials on supply and layingvessels shall ensure that damage to pipe, coatings, assembliesand accessories are avoided. Slings and other equipment usedshall be designed to prevent damage. Storage of pipes shall bein racks and suitable shoring shall be used. Maximum stackingheights shall be determined to avoid excessive loads on thepipe, coating or anodes. All material shipped for installationshall be recorded.802 All material shall be inspected for damage, quantity andidentification upon arrival. Damaged items shall be quaran-tined, repaired or clearly marked and returned onshore.803 Pipes and in-line assemblies shall be inspected for loosematerial, debris and other contamination and cleaned inter-nally before being added to the line. The cleaning method shallnot cause damage to any internal coating.804 A pipe tracking system shall be used to maintain recordsof weld numbers, pipe numbers, NDT, pipe lengths, cumula-tive length, anode installation, in-line assemblies and repairnumbers. The system shall be capable of detecting duplicaterecords.805 The individual pipes of the pipeline shall be marked inaccordance with the established pipe tracking system, using asuitable quick-curing marine paint. The location, size and col-our of the marking shall be suitable for reading by ROV duringinstallation and subsequent surveys. It may be necessary tomark a band on top of the pipeline to quantify any rotation thatmay have occurred during installation. If damaged pipes arereplaced, any sequential marking shall be maintained.806 Pipes shall be bevelled to the correct configuration,checked to be within tolerance, and inspected for damage.Internal line-up clamps shall be used, unless use of suchclamps is demonstrated to be impracticable. Acceptable align-ment, root gap and staggering of longitudinal welds shall beconfirmed prior to welding.807 In-line assemblies shall be installed and inspected asrequired by the specification, and shall be protected againstdamage during passage through the tensioners and over pipesupports.808 Field joint coating and inspection shall meet the require-ments given in Sec.9.809 The parameters to be controlled by measuring devices,and the allowable range of parameter variation during installa-tion, shall be established in a procedure for configuration con-trol, pipeline tension and stress monitoring. The function ofessential measuring devices shall be verified at regular inter-vals and defective or non-conforming devices shall repaired orreplaced.810 The buckle detector load chart, if a buckle detector isused (see 705) shall be checked at regular intervals. The buckledetector shall be retrieved and inspected if there is reason tobelieve that buckling can have occurred. If the inspectionshows indications of buckling or water ingress, the situationshall be investigated and remedial action performed.811 The position of pipeline start up and lay-down shall beverified as within their respective target areas prior to depar-ture of the lay vessel from site, and adequate protection ofpipeline and lay-down head shall be provided.

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812 Pipelaying in congested areas, in the vicinity of existinginstallations and at pipeline and cable crossings, shall be car-ried out using local positioning systems with specified accu-racy and appropriate anchor patterns (if used). Measures shallbe taken to protect existing installations, cables and pipelinesfrom damage. Such operations and the pipeline touch downpoint shall be monitored continuously by ROV.813 Other critical operations such as laying in short radiicurves, areas with steep slopes, use of very high or low pullingtension values etc. shall be identified and special proceduresfor the operation shall be prepared.814 In the event of buckling a survey of the pipeline shall beperformed before repair to establish the extent of damage andfeasibility of the repair procedure. After completion of therepair, a survey shall be performed of the pipeline over a lengthsufficient to ensure that no further damage has occurred.815 If loss or major damage to weight and corrosion coating oranodes and their cables/connectors are observed, repair shall beperformed and inspected according to established procedures.816 Prior to abandonment of the pipeline, all internal equip-ment except the buckle detector shall be removed and allwelds, including the abandonment and recovery head welds,shall be filled to a level that the pipe can be safely abandonedon and retrieved from the seabed. In the event that the cablewill have to be released from the vessel, a buoy and pennantwire should be attached to the abandonment and recoveryhead. The buoy shall be large enough to remain on the surfacewhen exposed to the weight of the pennant wire, as well as anyhydrodynamic loads from waves and current.Alternatively, seabed abandonment with a ROV friendly hook-ing loop may be used. Winch tension and cable lengths shall bemonitored, and the specified values shall not be exceeded dur-ing the abandonment and recovery operation.Before recovery the pipeline shall be surveyed over a lengthaway from the abandonment and recovery head, sufficient toensure that no damage has occurred.817 An as-laid survey shall be performed either by continu-ous touch down point monitoring or by a dedicated vessel, andshall, as a minimum, include the requirements given in J.

E. Additional Requirements for Pipeline Installation Methods Introducing Plastic

DeformationsE 100 General101 The additional requirements of this subsection are appli-cable to pipeline installation by methods which give total sin-gle event nominal strain ≥ 1.0% or accumulated nominalplastic strain ≥ 2.0%. 102 The specific problems associated with these installationmethods shall be addressed in the installation and testing spec-ifications.103 Pipes used for such installation methods shall meet thesupplementary requirement, pipe for plastic deformation (P),see Sec.7 I300.104 For installation welding, the sequence of pipes includedin the pipe string shall be controlled such that variations instiffness on both sides of welds are maintained within theassumptions made in the design. This may be achieved bymatching, as closely as possible, wall thickness/diameter of thepipes and the actual yield stress on both sides of the weld.105 100% automated ultrasonic testing (AUT) according tothe requirements given in Appendix E or manual ultrasonictesting according to the requirements given in Appendix Dshall be performed.

E 200 Installation manual201 An installation manual shall be prepared by the Contrac-tor for acceptance by the Purchaser and in addition to therequirements of A500 and applicable requirements of D200, itshall include:

— the amount of displacement controlled strain, both accu-mulated and maximum for each single strain cycle

— method for control of, and allowable variation in, curva-ture of the pipe between the point of departure from thereel and entry into the straighteners

— description of straighteners— proposed procedure for qualification of the installation

method by fracture mechanics assessment and validationtesting.

E 300 Qualification of the installation manual301 In addition to the applicable requirements of D300, qual-ification of the installation manual shall include:

— qualification of welding procedures according to the spe-cific requirements given in Appendix C, including δ-R orJ-R testing

— engineering critical assessments to determine the maxi-mum allowable weld defects

— validation of engineering critical assessment by testing, ifrelevant, see Appendix A

— testing of pipe coating durability— testing of straighteners and resulting pipe straightness.

302 A fracture assessment including testing shall be per-formed as specified in Appendix A. 303 Bending tests on pipe coating shall be performed todemonstrate that successive bending and straightening will notimpair the pipe coating and field coating. No degradation ofthe coating properties shall occur. For this test the coating testmay be carried out on plates. Alternatively, previous testresults may be used as documentation given that it is the samemanufacturer, chemical composition and strain level.304 The straighteners shall be qualified using pipe which isdelivered to the pipeline and bent corresponding to the mini-mum curvature fed into the straighteners. It shall be demon-strated that the strain resulting from the straightening is withinthe assumptions made for the validation testing, and that thespecified straightness is achieved. The straightening shall notcause damage to coating. The maximum deformation used dur-ing straightening to the specified straightness shall be recordedand regarded as an essential variable during installation.

E 400 Installation procedures401 In addition to the relevant applicable procedures of thissubsection, the following procedures are required as applica-ble:

— loadout/spooling of pipe onto reel — pipe straightening— anode and anode double plate installation— installation, welding and NDT of additional pipe strings— any other procedure needed due to the nature of the oper-

ations.

E 500 Requirements for installation501 Adequate support of the pipestring shall be providedwhen loading the reel. Tension shall be applied and monitoredduring reeling in order to ensure that the successive layers onthe reel are sufficiently tightly packed to prevent slippagebetween the layers. Adequate measures shall be taken to pro-tect the coating during reeling.502 If the reel is used for control of the pipeline tension dur-ing installation it shall be demonstrated that such use will giveacceptable redundancy and will not induce excessive stresses

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or have other detrimental effects.503 The curvature of the pipe, peaking and sagging, betweenthe point of departure from the reel and entry into the straight-eners shall not exceed the maximum values assumed in designand ECA and validated in the material testing of the girthwelded pipes.504 Anodes should be installed after the pipe has passedthrough the straightener and tensioner. The electrical connec-tion between anodes and pipe shall meet the specified require-ments and shall be verified at regular intervals, see Sec.9.

F. Pipeline Installation by TowingF 100 General101 The specific problems associated with pipeline towingoperations are to be addressed in the installation and testingspecifications. The weight and buoyancy distribution controlduring fabrication, launching of the pipestring, tow, ballastcontrol, environmental loads and contingencies shall beaddressed when the requirements are specified.102 Tows may be performed as:

— surface or near-surface tows, with the pipestring supportedby surface buoys

— mid-depth tows, where the pipestring is towed well clearaway from the seabed

— bottom tows, where the pipestring is towed in contactwith, or close to, the seabed.

103 For surface tows, all aspects pertaining to the tow aresubject to agreement in each case.104 For bottom or near bottom tows, the pipeline route shallbe surveyed prior to the tow and the route shall avoid roughseabed, boulders, rock outcrops and other obstacles that maycause damage to the pipeline, coating or anodes during the towand installation. During bottom and near bottom tows, ade-quate monitoring with ROVs and of the pipeline position atcritical phases is required. Satisfactory abrasion resistance ofthe pipeline coating shall be demonstrated. All aspects pertain-ing to bottom tows are subject to agreement in each case.105 For mid-depth tows, the requirements in F200 throughF800 are generally applicable.

F 200 Installation manual201 An installation manual shall be prepared by the Contrac-tor and, in addition to the requirements of A500 and applicablerequirements of D200, it shall include:

— description of towing vessel(s) including capacities,equipment and instrumentation

— description of pipestring instrumentation.

F 300 Qualification of installation manual301 Qualification of the installation manual shall include theapplicable requirements of D300.

F 400 Operating limit conditions401 Operating limit conditions with regard to weather win-dow for the tow, the seastate and current and allowed straingauge values (if installed) shall be established.

F 500 Installation procedures501 Installation procedures meeting the requirements of thisstandard and the installation specifications shall be preparedand agreed. In addition to the applicable procedures of D500,procedures are required for, but not limited to:

— control of weight- and buoyancy distribution

— launching of the pipestring— ballast control during tow— ballast control during installation— installation and joining of additional pipestrings.

F 600 Contingency procedures601 In addition to the applicable procedures of D600, contin-gency procedures are required for:

— weather conditions in excess of the operating limit condi-tions

— ballast system breakdown or partial failure— loss of towing tension— excessive towing tension— pre-designation of temporary mooring area(s) along the

tow route— third party marine activities.

F 700 Arrangement, equipment and instrumentation701 Vessels shall be equipped with:

— measuring equipment that continuously displays andrecords the towing speed and tensions

— measuring equipment that continuously displays and mon-itors the depth of the pipestring and its distance from theseabed

— measuring equipment that continuously display the posi-tion of any ballast valves. The flow rates during any bal-lasting and de-ballasting are to be displayed.

702 All measuring equipment shall be continuously moni-tored during the tow and installation.703 Installation of strain gauges to monitor the stresses in thepipestring during tow and installation shall be considered.

F 800 Pipestring tow and installation801 Launching of pipestrings shall be performed such thatover-stressing of the pipestring and damage to the coating andanodes are avoided. If pipestrings are moored inshore awaitingthe tow, adequate precautions shall be taken to avoid marinegrowth influencing pipestring buoyancy, weight and drag.802 Notification of the tow shall be given to the relevantauthorities, owners of subsea installations crossed by the tow-ing route and users of the sea.803 Towing shall not commence unless an acceptableweather window for the tow is available. During the tow astandby vessel shall be present to prevent interference with thetow by third party vessels.804 Tension in the towing line and the towing depth shall bekept within the specified limits during the tow. If required, bal-lasting or de-ballasting shall be performed to adjust the towingdepth to the specified values.805 Installation shall be performed by careful ballasting and de-ballasting. Care shall be exercised to prevent over-stressing of thepipestring. The use of drag chains during the installation is recom-mended. The installation operation shall be monitored by ROV.

G. Other Installation MethodsG 100 General101 Other installation methods may be suitable in specialcases. A thorough study shall be performed to establish the fea-sibility of the installation method and the loads imposed duringinstallation. Such methods are subject to agreement in each case.102 Installation of flexible pipelines, bundles and multiplepipelines shall be performed after a thorough study to establish thefeasibility of the installation method and the loads imposed duringinstallation. The installation is subject to agreement in each case.

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H. Shore PullH 100 General101 The requirements of this subsection are applicable to theexecution, inspection and testing of shore pull when pipes-trings are pulled either from a vessel onto the shore, or viceversa.102 Detailed requirements for the execution, inspection andtesting of shore pull shall be specified, considering the natureof the particular installation site. The specific problems associ-ated with shore pull shall be addressed in the installation andtesting specifications.

H 200 Installation manual201 An installation manual shall be prepared by the Contrac-tor and, in addition to the requirements of A500 and D200,shall cover,:

— description of offshore plant arrangement, equipment andinstrumentation

— description of onshore plant arrangement, equipment andinstrumentation

— special operations.

H 300 Qualification of installation manual301 Qualification of the installation manual shall include theapplicable requirements of D300.

H 400 Operating limit conditions401 Operating limit conditions with regard to the seastateand current shall be established if relevant.

H 500 Installation procedures501 Installation procedures meeting the requirements of thisstandard and the installation specifications, shall be preparedand agreed. In addition to the applicable procedures of D500,procedures are required for, but not limited to:

— installation of pulling head— tension control— twisting control— ROV monitoring where applicable— other critical operations— site preparation and winch set-up— buoyancy aids, where applicable— position control in trench, tunnels, etc., as applicable.

H 600 Contingency procedures601 Contingency procedures meeting the requirements ofthis standard and the installation and testing specification shallbe prepared.602 The contingency procedures shall cover:

— cable tension exceeding acceptable limits— excessive twisting of the pipestring— ROV breakdown— other critical or emergency situations.

H 700 Arrangement, equipment and instrumentation701 Cables, pulling heads and other equipment shall bedimensioned for the forces to be applied, including any over-loading, friction and dynamic effects that may occur.702 Winches shall have adequate pulling force to ensure thatthe pipe is maintained under controlled tension within theallowed stress/strain limits. The forces applied shall be con-trolled such that no damage to the pipeline anodes or coatingwill occur.703 The winches shall be equipped with wire tension andlength indicators and recorders. All measuring equipment shallbe calibrated, and an adequate amount of spares to ensure unin-

terrupted operation shall be provided.704 ROVs shall, if used, be equipped with video cameras,sonars, a bathymetric system, altimeter, adequate tooling suchas wire cutters or manipulator, transponders, responders etc. asneeded. It shall be documented that ROVs are able to operateunder the seastate expected for the operation in question.705 Other measuring and recording systems or equipment,such as strain gauges, should be provided if they are essentialfor the installation operation or the integrity of the pipeline.

H 800 Requirements for installation801 If necessary the seabed shall be prepared as required inB.802 Satisfactory abrasion resistance of the pipeline coatingshall be demonstrated for the installation conditions.803 Installation of the pulling head shall be made in a man-ner that prevents over-stressing of the pipeline and provides asecure connection.804 Buoyancy aids should be used if required to keep pullingtension within acceptable limits.805 During the operation, continuous monitoring of cabletension and pulling force is required. Monitoring with ROVsmay be needed.

I. Tie-in OperationsI 100 General101 The requirements of this subsection are applicable to tie-in operations using welding or mechanical connectors. Theoperations can be performed onboard a laying vessel (in whichcase welding is the preferred method) or underwater. The spe-cific problems associated with tie-in operations shall beaddressed in the installation and testing specifications.102 Tie-in operations, by means of hot or cold taps, are sub-ject to special consideration and agreement.

I 200 Installation manual201 An installation manual shall be prepared by the Contrac-tor and shall, in addition to the requirements of SubsectionA500 and Subsection D200, cover:

— description of diving plant arrangement, equipment andinstrumentation

— special operations.

I 300 Qualification of installation manual301 Qualification of the installation manual shall include theapplicable requirements of Subsection D300.

I 400 Operating limit conditions401 Operating limit conditions with regard to the seastate,current and vessel movements shall be established.

I 500 Tie-in procedures501 Tie-in procedures meeting the requirements of thisstandard and the installation specifications shall be preparedand agreed. In addition to the applicable procedures of Subsec-tion D500, the following procedures are required:

— lifting and deployment of the pipeline/riser section— configuration and alignment control— mechanical connector installation.

If underwater methods are used, additional procedures arerequired to cover the safety and operational aspects of theunderwater operations.

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I 600 Contingency procedures601 In addition to the requirements of Subsection D600, thefollowing contingency procedure is required:

— weather conditions in excess of the operating limit condi-tions before completion of tie-in

— If underwater methods are used, additional contingencyprocedures are required to cover the safety and operationalaspects of the underwater operations.

I 700 Tie-in operations above water701 The position of the tie-in shall be verified prior to startof operations. A survey shall be performed to establish that thelocation is free of obstructions and that the seabed conditionswill permit the tie-in to be performed as specified.702 To avoid overstressing during lifting and lowering of thepipeline sections, the winch tension shall be monitored contin-uously and shall not exceed the specified for operation. Liftingarrangements and equipment shall be designed, and liftingpoints attached, in a manner that prevents any over-stressing ofthe pipeline section during lifting and lowering into final posi-tion.703 ROV/diver monitoring of the operation should be per-formed to confirm correct configuration of the pipeline sec-tions from the seabed and onto the vessel.704 The alignment and position of the tie-in ends shall bewithin the specified tolerances before completing the tie-in.705 Installation of mechanical connectors shall be per-formed in accordance with the Manufacturer's procedure. Forflanged connections hydraulic bolt tension equipment shall beused. During all handling, lifting and lowering into the finalposition, open flange faces shall be protected against mechan-ical damage.706 A leak test to an internal pressure not less than the localincidental pressure should be performed for all mechanicalconnections whenever possible.707 Corrosion protection of the tie-in area shall be per-formed and inspected in accordance with accepted procedures.708 After completion of the tie-in, a survey of the pipeline onboth sides of the tie-in, and over a length sufficient to ensurethat no damage has occurred, should be performed709 It shall be verified that the position of the tie-in is withinthe target area prior to departure of the vessel from site. Thepipeline stability shall be ensured and adequate protection ofpipeline provided.

I 800 Tie-in operations below water801 In addition to the requirements in Subsection I700, therequirements in 802 and 803 are valid for tie-in operationsinvolving underwater activities.802 Diving and underwater operations shall be performed inaccordance with agreed procedures for normal and contin-gency situations covering applicable requirements.803 Requirements for underwater hyperbaric dry weldingare given in Appendix C.

J. As-Laid SurveyJ 100 General101 These requirements are applicable to as-laid surveysperformed by ROV either by continuous touch down pointmonitoring from the lay vessel or by a dedicated vessel.

J 200 Specification of as-laid survey201 The installation and testing specification shall contain

requirements to survey vessel, survey equipment, the extent ofsurvey, tolerances for the as-laid pipe line, and the maximumacceptable length and gap height of spans at various locations.The extent of procedures to be prepared and qualified shall bespecified.

J 300 As-laid survey301 The as-laid survey should include and not limited to thefollowing:

— determination of the position and depth profile of theentire pipeline

— identification and quantification of any spans with speci-fied accuracy to length and gap height

— determination of position of start-up and lay down heads,— determination of the presence of debris— as laid-video documentation of the pipeline to the extent

specified. Where video coverage cannot be obtained at anytime due to environmental reasons, alternate methodolo-gies should be utilised to ensure 100% coverage.

J 400 As-laid survey of corrosion protection systems401 Prior to any pipeline protection operations, a video sur-vey of the corrosion protection system shall be carried outalong the full length of the pipeline, including risers. Signifi-cant damage to the coating and sacrificial anodes shall be doc-umented.402 In the case of extensive damage to coating or sacrificialgalvanic anodes, consequences for long-term performanceshall be considered. Potential measurements at any bare sur-faces should be carried out to confirm adequate protection.Corrective actions may include retrofitting of anodes and coat-ing repairs, including risers. Satisfactory level of protectionshall be documented after the corrective action has been per-formed.

K. Span Rectification and Pipeline ProtectionK 100 General101 The requirements of this subsection are applicable tospan rectification and the protection of pipelines, e.g. bytrenching and backfilling, gravel dumping, grout bags, con-crete mattresses etc.102 A specific survey of the work area should be required inaddition to, or supplementing, the as-laid survey if:

— significant time has elapsed since the as-laid survey— a change in seabed conditions is likely— heavy marine activity is present in the area— new installations are present in the area— the as-laid survey does not provide sufficient information.

103 The survey of the work area, if required, shall as a min-imum include:

— a video inspection of the pipeline to identify any areas ofdamage to pipeline, coating and anodes

— cross profiles of the pipeline and adjacent seabed at regu-lar intervals

— depth profiles along the pipeline and the seabed at bothsides of the pipeline

— any existing subsea installations.

The undisturbed seabed level shall be included in the cross pro-files.

K 200 Span rectification and protection specification201 The requirements applicable to the specific methods ofspan rectification and protection regarding execution, monitor-ing and acceptance. Requirements for vessels, survey equip-

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ment etc. shall be addressed in the installation and testingspecifications. The extent of procedures to be prepared andqualified shall be specified.

K 300 Span rectification301 Span rectification is required for all spans exceeding thespecified acceptable length or height for the specific location.Rectification of other spans shall be considered if scour or sea-bed settlement could enlarge the span length and gap heightabove maximum acceptable dimensions before the firstplanned pipeline inspection.302 Adequate rectification of spans shall be documented bya video survey. All rectified spans shall be identified and thelength, gap and height shall be within the requirements.

K 400 Trenching401 Where trench excavation is performed after pipelaying,the trenching equipment shall be of a type that does not placesignificant loads on the pipeline and minimises the possibilityof damage to the pipeline.402 Trenching equipment shall be equipped with sufficientinstrumentation to ensure that damage and excessive pipe con-tact is avoided.403 Special care shall be taken during trenching operationsof piggy back / bundle pipelines, so that strapping arrange-ments will not be disturbed / damaged during trenching. Forsmall pipelines without any weight coating, trenching shall notdamage / dismantle the anodes.404 Where mechanical backfilling is required, it shall be car-ried out in a manner that minimises the possibility of damageor disturbance to the pipeline.405 The trenching equipment monitoring system shall becalibrated and include:

— devices to measure depth of pipe— a monitoring system and control system preventing hori-

zontal loads on the pipeline or devices to measure andrecord all vertical and horizontal forces imposed on thepipeline by trenching equipment, and devices to measurethe proximity of the trenching equipment to the pipeline,horizontally and vertically relative to the pipeline

— underwater monitoring systems enabling the trenchingequipment operator to view the pipeline and seabed profileforward and aft of the trenching equipment

— measuring and recording devices for trenching equipmenttow force

— devices monitoring pitch, roll, depth, height and speed ofthe trenching equipment.

406 Jet sleds shall have a control and monitoring system forthe position of the jetting arms and the overhead frame, hori-zontally and vertically relative to the pipeline. The location ofthe sled shall not be controlled by the force between sled andpipeline. Devices indicating tension in the tow line and show-ing the depth of the trench, shall be installed.407 The trench depth shall be referenced to the undisturbedseabed adjacent to the pipeline and to the top of the pipeline.408 An allowable range of values, indicated by the measur-ing devices of the trenching equipment, shall be established.The possibility of damage to coating shall be considered. Dur-ing trenching operations the measuring devices shall be contin-uously monitored.409 A post-trenching survey shall be performed immediatelyor as agreed after the trenching, in order to determine if therequired depth of lowering has been achieved and if any reme-dial work is required.

K 500 Post-installation gravel dumping501 Material used for gravel dumping shall meet the speci-fied requirements for specific gravity, composition and grad-ing.502 Gravel dumping shall be performed in a continuous andcontrolled manner, such that the required material is depositedover and under the pipeline, supports, subsea assemblies, etc.without disturbing their vertical or lateral position, and overthe adjacent seabed.503 The gravel dumping operation shall ensure rectificationof all spans to meet the specified requirements. Stabilisation offree spans should be carried out in a continuous operation,where the distance between spans to be stabilised is not toolarge, so as to avoid scouring and formation of free spansbetween gravel dumps.504 If the fall pipe technique is used for gravel dumping,minimum clearances shall be specified such that the fall pipecannot touch the pipeline, any other subsea installation or theseabed. Deployment operations shall be performed well awayfrom the pipeline or any other subsea installation. Before thefall pipe is moved to the dumping location, the clearancebeneath the fall pipe shall be verified. The clearance shall becontinuously monitored during dumping.505 The completed gravel dump shall leave a mound on theseabed with a smooth contour and profile and a slope notsteeper than specified. If the gravel dumping is performed overcable and pipeline crossings, the gravel mound shall providethe specified depth of cover over both the raised and thecrossed pipeline. During the dumping operations inspectionsshall be performed with a sonar survey system, or when visi-bility is restored, a video camera, to determine the complete-ness and adequacy of the dumping.506 Upon completion of the gravel dumping, a survey shallbe performed to confirm compliance with the specifiedrequirements. The survey shall, as a minimum, include:

— a video inspection of the pipeline length covered— cross profiles of the mound and adjacent undisturbed sea-

bed at regular intervals— length profiles of the mound— confirmation that minimum required buried depth is

achieved— any existing installations and their vicinity in order to

ensure that the installation(s) have not suffered damage.

K 600 Grout bags and concrete mattresses601 Concrete mattresses and grout bags shall meet the spec-ification with regard to size, shape and flexibility of the mate-rial, location of filling points, and the specific gravity,composition and grading of grout.602 Placing of grout bags and concrete mattresses shall beperformed in a controlled manner, such that the bags or mat-tresses are placed as required. Restrictions on vessel move-ments during the operation shall be given.603 During the placing operations, inspections shall be per-formed with a ROV-mounted video camera to determine thecompleteness and adequacy of the installation.604 Upon completion of the placing operation, a survey shallbe performed to confirm compliance with the specifiedrequirements. The survey shall as a minimum include:

— a video inspection of the completed work— cross profiles of the placed bags or mattresses and adjacent

undisturbed seabed at regular intervals— length profiles of the placed bags or mattresses and the

seabed at both sides of the area.

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L. Installation of Protective and Anchoring Structures

L 100 General101 Installation of protective and anchoring structures shallbe performed according to specifications and procedures meet-ing the requirements of the applicable design code.

M. Installation of RisersM 100 General101 The installation and testing specification shall cover theriser installation operations and address the specific problemsassociated with these operations. Diving and underwater oper-ations shall be performed in accordance with agreed proce-dures covering applicable requirements.102 The following methods may be used:

— integral installation by surface vessel, where the riser andpipeline are welded on deck of the vessel and the pipelineand riser lowered to the seabed. The riser is then posi-tioned in clamps installed on the structure

— installation by J-tube method, where the riser is pulledthrough a pre-installed J-shaped conduit on the structure,

— installation of prefabricated risers, where the riser isinstalled in clamps fitted on the structure by a surface ves-sel. Hyperbaric welding or mechanical connector are thenused to connect the riser and pipeline,

— stalk-on risers installed by a installation vessel, and— flexible, free-hanging risers.

M 200 Installation manual201 The installation manual should, in addition to the require-ments given in Subsection A500 and Subsection D200, cover:

— communication line and interface procedure with the plat-form where the riser is installed

— description of offshore plant arrangement, equipment andinstrumentation

— procedures for offshore riser fabrication— procedures for measurement and control of cut-off length

on the pipeline, riser bottom bend section, spool piece etc.— anchor pattern for installation vessel— diving and/or underwater operations procedures.

M 300 Qualification of the installation manual301 The installation manual shall be qualified. The qualifica-tion shall, as a minimum, include the requirements of Subsec-tion D300.

M 400 Operating limit conditions401 Operating limit conditions with regard to the seastateand current shall be established such that any over-stressing ofthe pipe material and weldments is avoided. When adverseweather conditions require shut-down of the installation work,the vessel shall move away from the platform.

M 500 Contingency procedures501 Contingency procedures shall be prepared for accept-ance, covering dynamic positioning system breakdown,anchor dragging and anchor line failure. If underwater meth-ods are used, additional contingency procedures are required tocover the safety and operational aspects of the underwateroperations.

M 600 Requirements for installation601 Offshore installation welding shall be performed inaccordance with Appendix C, and acceptance criteria for vis-

ual examination and non-destructive testing shall be estab-lished in accordance with Appendix D and Appendix E asapplicable.602 Transportation, storage and handling of riser pipe andappurtenances shall prevent any damage to coating and paint.In addition, special precautions shall be taken to protect flangefaces and other specially prepared surfaces from damage.603 All tolerances and measurements required in order toinstall the riser in accordance with drawings and specificationsshall be verified in the field before installation commences.Diameter, roundness and cleanness of J-tubes shall be checkedby gauging pigs, pulling a test pipe or similar to prevent thepulling head and riser from jamming.604 Adequate control shall be performed to ensure that theangularity and straightness of risers, the distance between ris-ers and bracing, the spacing between adjacent risers and othercritical dimensions meet the specified requirements.605 Tie-ins between riser and pipeline shall be performed inaccordance with I.606 Prior to pull-in of risers into J-tubes, it shall be verifiedthat the bellmouth is clear of debris and obstructions, that thebellmouth height above the seabed is within design limits, andthat no damage to the bellmouth, J-tube or J-tube clamps (ifapplicable) has occurred. Entry of the pipeline into the bell-mouth shall be monitored by ROV, and the tension in the pull-in cable shall be monitored by calibrated load cells and shallnot exceed the specified maximum. Proper sealing as specifiedshall be ensured at the bell-mouth for a riser in a J-tube in casethe corrosion protection system is designed with for a non-cor-rosive fluid in the annulus.607 All clamps, protection frames, anchor flanges etc., shallbe installed in accordance with specification and drawings,using appropriate bolt torque and to the specified tolerances.608 Repair of damage to coating and paint shall be per-formed in accordance with accepted procedures.609 Upon completion of the installation, a ROV or diver sur-vey shall be performed to confirm the position of the riser rel-ative to the platform, the position of any expansion loops,supports, etc., and the results of any trenching and protectionoperations.610 In case the riser has not been tested according to Sec.7 G,cleaning, gauging and system pressure testing shall be performedin general accordance with the requirements in O, except thatwire line pigs may be used, the holding time shall be at least 2hours and the pressure variation shall not exceed ± 0.4% unlessthe variation can be related to temperature variations during thetest period. Visual inspection of welds and flanged connectionsshall be performed whenever possible.

N. As-Built Survey

N 100 General101 All work on the pipeline, including crossings, trenching,gravel dumping, artificial backfill, subsea assemblies, riserinstallation, final testing etc., should be completed before theas-built survey is performed. The as-built survey of theinstalled and completed pipeline system is performed to verifythat the completed installation work meets the specifiedrequirements, and to document any deviations from the origi-nal design.

N 200 Specification of as-built survey201 The specification shall contain requirements to surveyvessel, survey equipment and the extent of survey. The extentof procedures to be prepared and qualified shall be specified.

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N 300 As-built survey requirements301 The as-built survey shall as a minimum include:

— detailed plot of the position of the pipeline, including loca-tion of in-line assemblies, anchoring and protective struc-tures, tie-ins, supports etc.

— out of straightness measurements as applicable— depth of cover or trench depth as applicable— quantification of span lengths and heights, including

length and height reporting tolerances— location of areas of damage to pipeline, coating and

anodes— location of any areas with observed scour or erosion along

pipeline and adjacent seabed— verification that the condition of weight coating (or

anchoring systems that provide for on-bottom stability) isin accordance with the specification

— description of wreckage, debris or other objects whichmay affect the cathodic protection system or otherwiseimpair the pipeline

— as-built video for the entire pipeline.

N 400 Inspection of impressed current cathodic corro-sion protection system401 Impressed current cathodic corrosion protection systemsshall be inspected, including cables, conduits, anodes and rec-tifiers. Readings from the corrosion monitoring system shall beverified by independent potential measurements, and adequateelectrical insulation from other installations (if applicable)shall be confirmed installed and commissioned according toISO 15589-2 Petroleum and natural gas industries - Cathodicprotection of pipeline transportation systems - Part 2: Off-shore pipelines...If the required protection level is not attained, the causes shallbe identified and adequate corrective actions performed. Satis-factory performance shall be documented after the correctiveaction.

O. Final Testing and Preparation for OperationO 100 General101 All work on the subsea pipeline system, including cross-ings, trenching, gravel dumping, artificial backfill, subseaassemblies, riser installation, as-built survey etc., should becompleted before the final testing commences.102 Disposal of cleaning and test fluids shall be performedin a manner minimising danger to the environment. Any dis-posal of fluids shall be in compliance with requirements fromNational Authorities.

O 200 Specification of final testing and preparation for operation201 The installation and testing specification shall containrequirements for equipment, the extent of testing and prepara-tion for operation, performance of tests and preparation foroperation and associated acceptance criteria. The extent of pro-cedures to be prepared and qualified shall be specified.

O 300 Procedures for final testing and preparation for operation301 All operations and tests shall be performed in accord-ance with agreed procedures.

O 400 Cleaning and gauging401 Cleaning and gauging may be combined with the initialflooding of the pipeline, be run as a separate operation, or becombined with the weld sphere removal after completion ofhyperbaric tie-in.

402 Appropriate measures shall be taken to ensure that anysuspended and dissolved substances in the fluid used for thisoperation are compatible with the pipe material and internalcoating (if applied), and that deposits are not formed within thepipeline.403 Water to be used for flooding should have a minimumquality corresponding to filtration through be filtered toremove suspended particles larger than a 50μm and filter, andshould have an average content of suspended matters notexceeding 20 g/m3.404 If water quality or the water source is unknown, watersamples shall be analysed and suitable actions shall be taken toremove and/or inhibit harmful substances.405 If water is to remain in the pipeline for an extendedperiod of time, consideration shall be given to control of bac-terial growth and internal corrosion by chemical treatment (seeSec.6 D302).406 Added corrosion inhibitors, any chemical additives likeoxygen scavengers, biocides, dyes, etc. shall be considered forpossible harmful interactions selected to ensure full compati-bility and their impact on the environment during and after dis-posal of the test watershall be considered.407 The pipeline cleaning concept shall consider:

— protection of pipeline components and facilities (e.g.valves) from damage by cleaning fluids and pigs

— testing devices such as isolation spheres etc.— removal of substances that may contaminate the product to

be transported— particles and residue from testing and mill scale— organisms and residue resulting from test fluids— chemical residue and gels— removal of metallic particles that may affect future inspec-

tion activities.

408 The main purpose of gauging a pipeline system is toestablish an internal diameter which is less than the minimuminternal diameter of the system in order to provide a basis forany future operational pigging activities. Selection of anappropriate gauging concept/method shall therefore be basedon a review of the operational pigging requirements.

a) As a minimum pipelines with a constant nominal internaldiameter should normally be gauged using a metallicgauge plate with a diameter that is 95% of the nominalinternal diameter. Alternatively the gauging plate mayhave a diameter that is 97% of the minimum internal diam-eter, taking into account the manufacturing tolerances forall system components and weld penetrations.

b) As a minimum pipelines with variations in the nominalinternal diameter should normally either be gauged in sec-tions in accordance with a) above or be gauged by use ofan “intelligent” gauging tool. In cases where this is consid-ered impractical or unnecessary, based on a review ofoperational pigging requirements, the system should begauged in accordance with a) above based on the smallestdiameter section.

Guidance note:The minimum internal diameter including uncertainties can beestablished as:Dmin,tot = Dmin(1-f0/2)-2tmax-2hbeadWhere hbead also allows for possible misalignment


409 Cleaning and gauging train design, number and type ofpigs, need for chemical cleaning, train velocity etc., shall bedecided based on type and length of pipeline, steep gradientsalong the pipeline route, type of service, construction method,downstream process etc.

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410 If cleaning and gauging are performed on separate sec-tions of the pipeline prior to tie-in, a minimum of one cleaningand gauging pig should be run through the completed pipelinesystem prior to, or during, product filling.

O 500 System pressure testing501 A pipeline system pressure test shall be performed basedupon the system test pressure determined according to Sec.5B 203 unless the test is waived as allowed by Sec.5 B204. Theextent of the test should normally be from pigtrap to pigtrap,including all components and connections within the pipelinesystem. The pressure test is normally performed as a leak test.502 The system may be tested as separate sections providedthat the tie-in welds between sections have been subject to100% radiographic, ultrasonic and magnetic particle testing, orby a combination of other methods which provide the same orimproved verification of acceptable weld quality.503 The pipeline section under test shall be isolated fromother pipelines and facilities. Pressure testing should not beperformed against in-line valves, unless possible leakage anddamage to the valve is considered, and the valve is designedand tested for the pressure test condition. Blocking off orremoval of small-bore branches and instrument tappings,should be considered to avoid possible contamination.504 End closures, temporary pigtraps, manifolds and othertemporary testing equipment, shall be designed and fabricatedaccording to a recognised code and with design pressure equalto the pipeline's design pressure. Such items shall be individu-ally pressure tested to at least the same test pressure as thepipeline.505 Filling of the pipeline with test water should be per-formed in a controlled manner, using water behind one or morepigs. The pig(s) shall be capable of providing a positive air/water interface. Considerations shall be given to pre-fillingvalve body cavities with an inert liquid, unless the valves haveprovision for pressure equalisation across the valve seats. Allvalves shall be fully open during line filling. A pig trackingsystem and the use of back-pressure to control the travel speedof the pig shall be considered if steep gradients occur along thepipeline route.506 Instruments and test equipment used for the measure-ment of pressure, volume and temperature shall be calibratedfor accuracy, repeatability and sensitivity. All instruments andtest equipment shall possess valid calibration certificates, withtraceability to reference standards within the 6 months preced-ing the test. If the instruments and test equipment have been infrequent use, calibration specifically for the test should berequired.507 Gauges and recorders shall be checked for correct func-tion immediately before each test. All test equipment shall belocated in a safe position outside the test boundary area.508 The test pressure should be measured using a deadweight tester. Dead weight testers shall not be used before astable condition is confirmed. When pressure testing is per-formed from a vessel, where a dead weight tester can not beutilised due to the vessel movements, the test pressure shall bemeasured by using one high accuracy pressure transducer inaddition to a high accuracy large diameter pressure gauge.509 The following requirements apply for instruments andtest equipment:

— dead weight testers shall have a range of minimum 1.25times the specified test pressure, and shall have an accuracybetter than ±0.1 bar and a sensitivity better than 0.05 bar

— the volume of water added or subtracted during a pressuretest shall be measured with equipment having accuracybetter than ± 1.0% and sensitivity better than 0.1%

— temperature measuring instruments and recorders shallhave an accuracy better than ±1.0°C, and a sensitivity bet-

ter than 0.1°C— pressure recorders and temperature recorders when

included shall be used to provide a graphical record of thepressure test continuously for the total duration of the test.

If a pressure transducer is used instead of a dead weight tester,the transducer shall have a range of minimum 1.1 times thespecified test pressure, and the accuracy shall be better than ±±0.2% of test pressure. Sensitivity shall be better than 0.1%.510 A correlation that shows the effect of temperaturechanges on the test pressure where relevant, shall be developedand accepted prior to starting the test. Temperature measuringdevices, if used, shall be positioned close to the pipeline, andthe distance between the devices shall be based on temperaturegradients along the pipeline route.511 The test medium should be water meeting the require-ments given in O400.512 The air content of the test water shall be assessed by con-structing a plot of the pressure against volume during the initialfilling and pressurisation, until a definite linear relationship isapparent, see Figure1. This should be done at 35% of test pres-sure. The assessed air content should not exceed 0.2% of thecalculated total volume of the pipeline under test. If the limit isexceeded, it shall be documented that the amount of air, notwill influence the accuracy of the test significantly.

Figure 1 Determination of volume of air

513 Pressurisation of the pipeline shall be performed as acontrolled operation with consideration for maximum allowa-ble velocities in the inlet piping. The last 5% up to the test pres-sure shall be raised at a reduced rate to ensure that the testpressure is not exceeded. Time shall be allowed for confirma-tion of temperature and pressure stabilisation before the testhold period begins.514 The pressure level requirement for the system pressuretest is given in Sec.5 B203.515 The test pressure hold period after stabilisation shall beheld for a minimum 24 hours.516 Subject to agreement shorter pressure hold periods maybe accepted for pipelines with test volumes less than 5 000 m3.In these cases the principles of Sec.7 G shall normally apply. 517 The pressure and temperatures where relevant, shall becontinuously recorded during the pressurisation, stabilisationand test hold periods.518 If possible, flanges, mechanical connectors etc. underpressure shall be visually inspected for leaks during the pres-sure test, either directly or by monitors.

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519 The pressure test is acceptable if the pipeline is free fromleaks, and the pressure variation is within ± ± 0.2% of the testpressure. A pressure variation up to an additional ±0.2% of thetest pressure is normally acceptable if the total variation (i.e. ±0.4%) can be documented to be caused by temperature fluctu-ations or otherwise accounted for. If pressure variations greaterthan ± 0.4% of the test pressure are observed, the holdingperiod shall be extended until a hold period with acceptablepressure variations has occurred.520 De-pressurisation of the pipeline shall be performed as acontrolled operation with consideration for maximum allowa-ble velocities in the pipeline and the discharge piping.

O 600 De-watering and drying601 De-watering is required before introducing the productfluid into the pipeline. Drying may be required in order to pre-vent an increase in the corrosion potential or hydrate forma-tion, or if omission of drying is deemed to have an adverseeffect on the product transported.602 Introduction of the fluid may be accepted in specialcases. The separation pig train between the test medium andthe fluid will then require special qualification in order to avoidcontact between the residual test water and the product.603 Selection of de-watering and drying methods and chem-

icals shall include consideration of any effect on valve and sealmaterials, any internal coating and trapping of fluids in valvecavities, branch piping, instruments etc.

O 700 Systems testing701 Prior to fluid product filling, safety and monitoring sys-tems shall be tested in accordance with accepted procedures.This includes testing of:

— corrosion monitoring systems— alarm and shutdown systems— safety systems such and pig trap interlocks, pressure pro-

tection systems etc.— pressure monitoring systems and other monitoring and

control systems— operation of pipeline valves.

P. DocumentationP 100 General101 The installation and testing of the pipeline system shallbe documented. The documentation shall, as a minimum,include that given in Sec.12.

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SECTION 11OPERATIONS AND ABANDONMENT

A. GeneralA 100 Objective101 The purpose of this section is to provide minimumrequirements for the safe and reliable operation of submarinepipeline systems (see Sec.11 A500) for the whole service lifewith main focus on pipeline integrity management (PIM).

A 200 Scope and application201 This section covers the submarine pipeline systemphases operations and abandonment. Operations consist ofcommissioning, operation and de-commissioning.202 Pipeline integrity is the ability of the submarine pipelinesystem to operate safely and withstand the loads imposed dur-ing the pipeline lifecycle. 203 The pipeline integrity management process is the com-bined process of threat identification, risk assessments, plan-ning, monitoring, inspection, maintenance etc. to maintainpipeline integrity.204 The equipment scope limits include pipeline and compo-nents according to the definition of a submarine pipeline sys-tem in Sec.1 C335. The PIM principles and methodology areapplicable to pipeline systems in general.

A 300 Responsibilities301 Pipeline integrity management is the responsibility ofthe operator. The operator needs to ensure that the integrity ofthe pipeline is not compromised.302 At all times during the operational life of the pipelinesystem, responsibilities must be clearly defined and allocated.

A 400 Authority and company requirements401 The relevant national requirements shall be identifiedand ensured that they are complied with.402 The relevant company requirements should be compliedwith when planning and performing pipeline integrity management.

A 500 Safety philosophy501 The safety philosophy adopted in design and consistentwith Sec.2 shall apply.502 Operating safely is interpreted as operating to meet theacceptance criteria as established in design and updatedthrough the project phases and service life.503 Design and operating premises and requirements shall beidentified prior to start of operation and updated during the serv-ice life. These premises and requirements may be linked to:

— pressure, temperature and flow rate— fluid composition (content of water, CO2, H2S etc.)— sand— cover depths— free spans length and height— pipeline configuration (e.g. snaking)— others.

A change in design basis will in general require a re-qualifica-tion, see Sec.11 E.504 It must be verified that design and operating premisesand requirements are fulfilled. If this is not the case, appropri-ate actions shall be taken to bring the pipeline system back toa safe condition.505 A risk based pipeline integrity management philosophy,

which takes into account probability of failure and conse-quence of failure, should be applied.

B. CommissioningB 100 General101 Commissioning is activities associated with the initialfilling of the pipeline system with the fluid to be transported,and is part of the operational phase. Documentation and proce-dures for commissioning are specified in Sec.12 E.

B 200 Fluid filling201 During fluid filling, care shall be taken to prevent explo-sive mixtures and, in the case of gas or condensate, to avoidhydrate formation. The injection rate shall be controlled so thatpressure and temperature do not exceed allowable limits forthe pipeline material or dewpoint conditions.

B 300 Operational verification301 After stable production has been reached it shall be ver-ified that the operational limits are within design conditions.Important issues can be:

— flow parameters (pressure, temperature, etc.)— CP-system— expansion— movement— lateral snaking— free span and exposure

302 Scheduling of the first inspection of the wall thicknessshall be evaluated based on the corrosivity of the fluid,expected operational parameters, robustness of the internalcorrosion protection system (inhibitor system), the corrosionallowance used in the design, the effectiveness of the QA/QCsystem applied during fabrication and construction, and thedefect sizing capabilities of the inspection tool that will beused during operation of the pipeline.

C. Integrity Management SystemC 100 General101 The operator shall establish and maintain an integritymanagement system which as a minimum includes the follow-ing elements:

— company policy— organisation and personnel— condition evaluation and assessment methods— planning and execution of activities— management of change— operational controls and procedures— contingency plans— reporting and communication— audit and review— information management.

The activity plans are the result of the integrity managementprocess by use of recognised assessment methods, see Sec.11 D.The core of the integrity management system is the integritymanagement process as illustrated in Figure 1. The other ele-ments mainly support this core process.

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Figure 1 Pipeline integrity management system

102 Specification of work processes should be the basis fordefinition of procedures. Documents and procedures for theoperational phase are specified in detail in Sec.12 H.103 The detailed procedures for operation, inspections andrepairs shall be established prior to start-up of operation.104 Procedures covering non-routine or special activities,shall be prepared as required, e.g. in case of major repairs,modifications etc.

C 200 Company policy201 The company policy for pipeline integrity managementshould set the values and beliefs that the company holds, andguide people in how they are to be realized.

C 300 Organisation and personnel301 The roles and responsibilities of personnel involved inintegrity management of the pipeline system shall be clearlydefined.302 Training needs shall be identified and training shall beprovided for relevant personnel in relation to management ofpipeline integrity.

C 400 Condition evaluation and assessment methods401 The condition evaluation of the pipeline system shall userecognised methods and be based on design data and opera-tional experience.

C 500 Planning and execution of activities501 This covers planning and execution of inspections, anal-yses, studies, interventions, repairs and other activities.

C 600 Management of change601 Modifications of the pipeline system shall be subject toa management of change procedure that must address the con-tinuing safe operation of the pipeline system. Documentationof changes and communication to those who need to know isessential.602 If the operating conditions are changed relative to thedesign premises, a re-qualification of the pipeline systemaccording to Sec.11 E shall be carried out.

C 700 Operational controls and procedures701 Relevant operational controls and procedures are:

— start-up and shutdown procedures— cleaning and other maintenance, e.g. pigging

— corrosion control— monitoring— safety equipment and pressure control system.

702 Measures shall be in place to ensure that critical fluidparameters are kept within the specified design limits. As aminimum, the following parameters should be controlled ormonitored:

— pressure and temperature at inlet and outlet of the pipeline— dew point for gas lines— fluid composition, flow rate, density and viscosity.

703 All safety equipment in the pipeline system, includingpressure control and over-pressure protection devices, emer-gency shutdown systems and automatic showdown valves,shall be periodically tested and inspected. The inspection shallverify that the integrity of the safety equipment is intact andthat the equipment can perform the safety function as speci-fied.704 Safety equipment in connecting piping systems shall besubject to regular testing and inspection.705 For pressure control during normal operations, see Sec.3B300.706 Operational control shall ensure that design temperaturelimits are not exceeded. If the design is based on a constanttemperature along the whole route, control of inlet temperaturewill be sufficient. If the design is based on a temperature pro-file for the pipeline, additional measures may be required.

C 800 Contingency plans801 Plans and procedures for emergency situations shall beestablished and maintained based on a systematic evaluation ofpossible scenarios.

C 900 Reporting and communication901 A plan for reporting and communication to employees,management, authorities, customers, public and others shall beestablished and maintained. This covers both regular reportingand communication, and reporting in connection with changes,special findings, emergencies etc.

C 1000 Audit and review1001 Audits and reviews of the pipeline integrity manage-ment system shall be conducted regularly.1002 The focus in reviews should be on:

— effectiveness and suitability of the system— improvements to be implemented.

1003 The focus in audits should be on:

— compliance with regulatory and company requirements— rectifications to be implemented.

C 1100 Information management1101 A system for collection of historical data, an in-servicefile, shall be established and maintained for the whole servicelife, see Sec.12 A103 and Sec.12 F201. The in-service file willtypically consist of documents, data files and data bases.1102 The in-service file, together with the DFI-resume, shallbe the basis for future inspection planning.1103 The in-service file and the DFI-resume shall be easilyretrievable in case of an emergency situation.1104 The documents, data and information shall be managedas described in Sec.12F and 12I.

Integrity management system

Integrity management processCompany policy

Organisation and personnel

Management of change

Contingency plans

Reporting and communication

Audit and review

- Evaluation of threats- Inspection and monitoring- Integrity assessment- Mitigation, intervention and repairs

Operational controls and procedures

Information management

- Condition evaluation and assessment methods

- Planning and execution of activities

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D. Integrity Management ProcessD 100 General101 The integrity management process consists of the fol-lowing steps:

a) Evaluation of threats and the condition of the pipeline system.b) Plan and conduct activities including inspection and mon-

itoring.c) Integrity assessment based on inspection and monitoring

results and other relevant information.d) Assess need for, and conduct if needed, intervention and

repair activities and other mitigating actions.

This process shall be performed periodically within regularintervals.102 The requirements for corrosion inspection and monitor-ing, and the capability of optional techniques, shall be evalu-ated at an early stage of pipeline system design.

Guidance note:Pipelines and risers manufactured from Corrosion ResistantAlloys (CRA) do not normally require inspection and monitoringof internal corrosion. This must be evaluated in each particularcase.


103 An inspection and monitoring philosophy shall be estab-lished, and shall form the basis for the detailed inspection andmonitoring program. The philosophy shall be evaluated every5 to 10 years.104 All inspection and monitoring requirements identifiedduring the design phase as affecting safety and reliability dur-ing operation shall be covered in the inspection and monitoringprogram, see Sec.3 B200 and Sec.5 B300.105 A special investigation shall be performed in case of anyevent which impairs the safety, reliability, strength or stabilityof the pipeline system. This investigation may initiate furtherinspections.106 If mechanical damage or other abnormalities aredetected during the periodic inspection, a proper evaluation ofthe damage shall be performed, which may include additionalinspections.

D 200 Evaluation of threats and condition201 Threats shall be systematically identified, assessed anddocumented throughout the operational lifetime. This shall bedone for each section along the pipeline and for components.Examples of typical threats are:

— internal corrosion— external corrosion— free spans— buckles— impact damage.

202 The condition assessment shall include an evaluation ofrelevant risks by using qualitative and/or quantitative methods.Data from design and operation is the basis for the conditionassessment.

D 300 External inspectionPipeline configuration survey301 A pipeline configuration survey is a survey to determinethe position, configuration and condition of the pipeline and itscomponents. 302 The start-up inspections should be completed within oneyear from start of production, see Sec.11 B300. In case of sig-nificant increase in temperature, pressure or flowrate after this

first inspection, the need of additional inspections should beconsidered.303 A long term inspection programme reflecting the overallsafety objective for the pipeline shall be established, and shallbe maintained/updated on a regular basis. The followingshould be considered:

— operation conditions of the pipeline— consequences of failure— likelihood of failure— inspection methods— design and function of the pipeline.

The long term program shall state the philosophy used formaintaining the integrity of the pipeline system and will formthe basis for the detailed inspection program in terms ofinspection methods and intervals.304 The long term inspection program shall include theentire pipeline system. The following items, at minimum,should be considered:

— pipeline— risers and their supports— valves— Tee and Y connections— mechanical connectors— flanges— anchors— clamps— protecting structures— anodes— coating.

305 A detailed inspection program including specificationsfor the inspections shall be prepared for each survey. Thedetailed inspection program should be updated based on previ-ous inspections as required.306 Pipeline systems that are temporarily out of service shallalso be subject to periodical survey.307 Inspection shall be carried out to ensure that the designrequirements remain fulfilled and that no damage hasoccurred. The inspection program should, as a minimum,address:

— exposure and burial depth of buried or covered lines, ifrequired by design, regulations or other specific require-ments

— free spans including mapping of length, height and end-support conditions

— condition of artificial supports installed to reduce free span— local seabed scour affecting the pipeline integrity or

attached structures— sand wave movements affecting the pipeline integrity— excessive pipe movements including expansion effects— identification of areas where upheaval buckling or exces-

sive lateral buckling has taken place— integrity of mechanical connections and flanges— integrity of sub-sea valves including protective structure— Y- and Tee connections including protective structure— pipeline settlement in case of exposed pipeline, particu-

larly at the valve/Tee locations— the integrity of pipeline protection covers (e.g. mattresses,

covers, sand bags, gravel slopes, etc.)— mechanical damage to pipe, coatings and anodes— major debris on, or close to, the pipeline that may cause

damage to the pipeline or the external corrosion protectionsystem

— leakage.

308 The risers shall be part of the long-term inspection pro-gramme for the pipeline system. In addition to the generallyapplicable requirements for pipeline inspection, special atten-

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tion shall be given to the following elements for riser inspec-tions:

— riser displacement due to pipeline expansion or foundationsettlement

— coating damage— technique for corrosion control of any risers in closed con-

duits or J-tubes— extent of marine growth— extent of any previous damage due to corrosion— integrity and functionality of riser supports and guides— integrity and functionality of protecting structure.

309 The frequency of future external inspections shall bedetermined based upon an assessment of:

— authority and company requirements— degradation mechanisms and failure modes— likelihood and consequences of failure— results from previous inspections— changes in the operational parameters— re-qualification activity and results— repair and modifications— subsequent pipelay operation in the vicinity.

310 Critical sections of the pipeline system vulnerable todamage or subject to major changes in the seabed conditionsi.e. support and/or burial of the pipeline, shall be inspected atshort intervals, normally on an annual basis. The remainingsections should also be inspected, ensuring a full coverage ofthe entire pipeline system within a suitable period, normallynot more than 5 years.311 For risers contained in J-tubes filled with non-corrosivefluid inspection of external corrosion may not be required ifadequate properties of the fluid is verified by periodic testing.Risers in the splash zone and the atmospheric zone312 In the splash zone and in the atmospheric zone, damagedand/or disbonded coatings can cause severe corrosion damage.Risers carrying hot fluids are most vulnerable to such damage.313 In the splash and atmospheric zones, visual examinationof the coating should be performed in order to assess the needsfor preventive maintenance. Besides visual indications ofdirect damage to the coating, effects such as rust discolorationand bulging or cracking of the coating are indicative of under-rusting. Coating systems which prevent close inspection ofunder-coating corrosion shall require special consideration.314 The frequency of the external inspection in the splashzone of risers shall be determined based on the fluid category,the line pipe material, coating properties and any corrosionallowance.Pipelines and risers in the submerged zone315 In the submerged zone, coating malfunctions are notcritical unless they are combined with deficiency in thecathodic protection system.316 To a large extent, inspection of external corrosion pro-tection of pipelines and risers with sacrificial anodes can belimited to inspection of the condition of anodes. Excessiveanode consumption is indicative of coating deficiencies,except close to platforms, templates and other structures wherecurrent drain may lead to premature consumption of adjacentpipe anodes.317 Potential measurements on anodes, and at any coatingdamage exposing bare pipe metal, may be carried out to verifyadequate protection. Electric field gradient measurements inthe vicinity of anodes may be used for semi-quantitativeassessments of anode current outputs.318 For pipelines with impressed current cathodic protectionsystems, measurements of protection potentials shall, at mini-mum, be carried out at locations closest to, and most remote

from, the anode(s).319 A survey of the external corrosion protection system,should be carried out within one year of installation.

D 400 In-line inspection401 In-line inspection is carried out in order to confirm theintegrity of the pipeline system, primarily by means of in situwall thickness measurements.

Guidance note:Un-piggable pipelines are subject to separate evaluations andalternative methods.


402 In-line inspection should be carried out with a carriertool ("inspection pig") capable of inspecting the internal andexternal surface of the pipeline along its full circumference andlength, or a critical part thereof.403 The technique for detection of internal and/or externalcorrosion shall be selected based on considerations of fluid,linepipe material, diameter and wall thickness, expected formof damage, and requirements to detection limits and defect siz-ing capability. The latter shall be determined based on pipelinedesign and operational parameters.404 Candidate operators of inspection tools should berequired to document the capability of their systems withrespect to detection limits and sizing of relevant corrosiondefects (including localised corrosion at girth welds) for thepipe dimensions considered.405 The frequency of in-line inspections shall be determinedbased on factors such as:

— authority and company requirements— likelihood and consequences of failure— potential corrosivity of fluid— potential for development of external corrosion at hot-

spots such as riser(s) and landfall/onshore pipeline sec-tions

— detection limits and accuracy of inspection system— results from previous surveys and monitoring— changes in pipeline operational parameters, etc.

See also Sec.11 B300.406 Inspection by special internal tools may be used to detectexternal corrosion of risers and pipelines in all three zones (seeD200) including risers contained in J-tubes, if required.

D 500 Corrosion monitoring501 The objective of monitoring internal corrosion is to con-firm that the fluid remains non-corrosive or, more often, to assessthe efficiency of any corrosion preventive measures, and accord-ingly to identify requirements for inspection of corrosion.502 Corrosion monitoring as defined above does not nor-mally give any quantitative information of critical loss of wallthickness. Although monitoring may be carried out as actualwall thickness measurements in a selected area, it cannotreplace pipeline inspection schemes that cover the pipelinesystem, or section thereof, in its full length and circumference.On the other hand, inspection techniques for internal corrosionare not normally sensitive enough to replace monitoring.503 The following major principles of corrosion monitoringmay be applied:

— fluid analyses; i.e. monitoring of fluid physical parametersand sampling of fluid for chemical analysis of corrosivecomponents, corrosion retarding additions or corrosionproducts

— corrosion probes; i.e. weight loss coupons or other retriev-able probes for periodic or on-line determination of corro-sion rates

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— in-situ wall thickness measurements, i.e. repeated meas-urements of wall thickness at defined locations using port-able or permanently installed equipment.

504 Techniques and equipment for corrosion monitoringshall be selected based upon:

— monitoring objectives, including requirements for accu-racy and sensitivity

— fluid corrosivity and the corrosion preventive measures tobe applied

— potential corrosion mechanisms.

505 A typical major objective of corrosion monitoring is todetect changes in either intrinsic corrosivity of the fluid, or inthe efficiency of the corrosion prevention measures. For pipe-lines carrying dry (i.e. fully processed) gas, inspection of inter-nal corrosion may be postponed provided that monitoringdemonstrates that no corrosive liquids have entered the pipe-line, or been formed by condensation downstream of the inlet.

D 600 Integrity assessment601 Pipeline systems with unacceptable defects may beoperated temporarily under the design conditions or reducedoperational conditions until the defect has been removed orrepair has been carried out. It must, however, be documentedthat the pipeline integrity and the specified safety level is main-tained, which may include reduced operational conditions and/or temporary precautions.602 When a defect is observed, an evaluation shall be per-formed including:

— quantify details of the defect— identify cause of defect— evaluate accuracy and uncertainties in the inspection

results.

If the defect is not acceptable, then further evaluations include:

— options for continued operation of the pipeline system— repair methods.

603 In each case a thorough evaluation of the defect and theimpact on safety and reliability for the operation of the pipelineshall be performed. The requirements given in the followingsections regarding required actions, e.g. grinding or replace-ment, may be waived if it can be documented that the specifiedsafety level for the pipeline system is not impaired.604 Defects that affect the safety or reliability of the pipelineshall either be removed by cutting out the damaged section ofthe pipe or repaired by local reinforcement. Alternatively, thepipeline may be permanently re-qualified to lower operationalconditions see Sec.11 E and Sec.5, e.g. reduced pressure,which may allow for omitting repair.Free spans605 For guidance, reference is made to DNV-RP-F105, FreeSpanning Pipelines.Global buckling606 If the design is based on controlled global bucklingincluding plastic strains, the pipeline should be verified basedon established design limits and conditions (curvatures,strains, bending moment). If unexpected global bucklingoccurs, utilisation of the pipeline should be evaluated based onrelevant failure modes. For guidance, reference is made toDNV-RP-F110, Global Buckling of Submarine Pipelines.Grooves, gouges, cracks and notches607 Sharp defects like grooves, gouges, and notches shouldpreferably be removed by grinding or other agreed repairmethods. For ground defects where all sharp edges are con-firmed as removed, the defect can be regarded as a smooth

metal loss defect, see D608.Metal loss defects608 Metal loss defects caused by e.g. corrosion, erosion, orgrind repair shall be checked for capacity. For guidance, refer-ence is made to DNV-RP-F101, Corroded Pipelines.Dents609 A dent is defined as a depression which produces a grossdisturbance in the curvature of the pipe wall. For dent accept-ance criteria, see Sec.5 E503.610 A dent affecting a weld can result in cracks, and removalof the damaged portion of the pipe should be considered. Thedamaged part can be cut out as a cylinder, or repaired byinstalling a full encirclement welded split sleeve or boltedclamp which is designed to take the full internal operatingpressure.

D 700 Mitigation, intervention and repairs701 Examples of mitigation, intervention and repairs are:

a) mitigation:

— restrictions in operational parameters (pressure, tem-perature, flow rate, fluid composition etc.)

— use of chemical injections.

b) intervention:

— rock dumps— pipeline protections— trenching.

c) repairs:

— local reinforcement (clamps etc.)— replacement of pipeline parts.

All mitigation, intervention and repairs shall be documented.702 Repair and modification shall not impair the safety levelof the pipeline system below the specified safety level.703 All repairs shall be carried out by qualified personnel inaccordance with agreed specifications and procedures, and upto the standard defined for the pipeline.If the repair involves welding, the personnel, method, andequipment shall be agreed upon according to Appendix C.For other types of repair the requirements for personnel,method and necessary equipment to carry out the work shall beagreed upon in each case.704 All repairs shall be tested and inspected by experiencedand qualified personnel in accordance with agreed procedures.NDT personnel, equipment, methods, and acceptance criteriashall be agreed upon in accordance with Appendix D.705 Depending upon the condition of the damage, a tempo-rary repair may be accepted until the permanent repair can becarried out. If a temporary repair is carried out, it shall be doc-umented that the pipeline integrity and safety level is main-tained either by the temporary repair itself and/or incombination with other precautions.Repair of leaks706 Prior to carrying out a permanent repair of any leak, thecause of the leak shall be established.707 The most suitable method for repairing a leak in the pipedepends upon e.g. the pipe material, pipe dimensions, locationof leak, load conditions, pressure, and temperature. The fol-lowing repair methods may be used:

a) The damaged portion is cut out of the pipe as a cylinderand a new pipe spool is installed either by welding or byan mechanical connector. For guidance, reference is made

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to DNV-RP-F113 Pipeline Subsea Repair.b) Clamps are installed, and tightness is obtained by either

welding, filler material, friction or other qualified mechan-ical means.

708 Leaking flanges and couplings may be sealed by install-ing a seal clamp covering the leaking flange or coupling,increasing the bolt pre-load, or replacing gaskets and seals.Prior to increasing the pre-load in bolts, it shall be documentedby calculation that no over-stressing occurs in bolts, flange orgasket/seals. In case the pre-load in the bolts is removed, e.g.due to changing of gasket, new bolts shall be used for theflange connection.709 All repair clamps, sleeves, pipe spools, and mechanicalconnectors shall be qualified prior to installation and leaktested after installation. For guidance, reference is made toDNV-RP-F113 Pipeline Subsea Repair.Repair by welding710 Repair welding procedures and welders shall be quali-fied as described in Appendix C.711 Repair welding above water shall be carried out asdescribed in Appendix C.712 Underwater welding shall be carried out in a dry habitat,see Appendix C.713 Repair welding may, in special cases, be carried out onpipelines while operating, depending on pipe material, pipewall thickness, fluid type, pressure and temperature. It shall bedocumented that safety for carrying out the repair is accepta-ble, and a safety procedure shall be established.714 All repair welds shall be subject to visual and non-destructive testing, see Appendix D. Following the repair,pressure testing may be required for the repaired section.

E. Re-qualificationE 100 General101 The purpose of this section is to define re-qualificationand to give requirements for re-qualification of pipeline sys-tems.102 Re-qualification is a re-assessment of the design underchanged design conditions.103 A re-qualification may be triggered by a change in theoriginal design basis, by not fulfilling the design basis, or bymistakes or shortcomings having been discovered during nor-mal or abnormal operation. Possible causes may be:

a) preference to use this standard, e.g. due to requirementsfor higher utilisation for existing pipelines

b) change of the premises:

— environmental loads— deformations— scour.

c) change of operational parameters:

— pressure or temperature— corrosivity of the medium.

d) deterioration mechanisms having exceeded the originalassumptions:

— corrosion rate, either internal or external— dynamic responses, contributing to fatigue, which

may be caused by lacking supports etc.

e) extended design life.

f) discovered damage:

— dents— damage to pipeline protection— weld defects— corrosion related defects— damage to anodes.

E 200 Application201 Within the original design life, and without essentialchanges in the manner of employment (repair etc.), the stand-ard under which the pipeline was built may apply when consid-ering incidents, minor modifications or rectification of designparameters exceeded during operation. This standard and asso-ciated DNV codes may alternatively be used.For major modifications or other instances not covered by theabove paragraph this standard shall apply.

Guidance note:The same safety level shall apply for lifetime extensions of anexisting pipeline as would apply for the design of a new pipeline.The reason for requiring use of this standard is in case the origi-nal standard used for design is less stringent than necessary tomeet the target safety levels specified in this standard.


E 300 Safety level301 A target safety level as defined in Sec.2 C500 shall applyfor a re-qualification assessment.302 Operational experience, e.g. change of operational con-ditions, inspection records and modifications, shall be consid-ered in a re-qualification assessment.

E 400 System pressure test401 System pressure testing may be required when:

— the original mill pressure test or system pressure test doesnot satisfy requirements according to this standard at thenew design pressure

— a significant part of the pipeline has not been system pres-sure tested e.g. new pipeline section. (for omission of sys-tem pressure test, see Sec.5 B204).

E 500 Deterioration501 All relevant deterioration and damage mechanisms shallbe evaluated. Typical mechanisms are:

a) corrosion:

— external corrosion— internal corrosion.

b) erosionc) accidental loadsd) development of free spanse) fatiguef) settlement.

502 Sufficient reliability or safety measures shall be appliedto account for the accuracy and uncertainties in the inspectionresults.503 Accumulated damage experienced prior to the re-quali-fication shall be included in the evaluation.

E 600 Design criteria601 The parameters that trigger the re-qualification and theimplication of changes in these parameters on different designconditions shall be clearly identified and documented. For re-design of these design conditions, reference is made to Sec.5.

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F. De-commissioningF 100 General101 Pipeline de-commissioning shall be planned and pre-pared.102 De-commissioning shall be conducted and documentedin such a way that the pipeline can be re-commissioned and putinto service again.103 De-commisioning evaluation shall include the followingaspects:

— relevant national regulations— environment, especially pollution— obstruction for ship traffic— obstruction for fishing activities— corrosion impact on other structures.

104 De-commissioned pipelines shall be preserved to reduce

effect from degradation mechanisms.

G. AbandonmentG 100 General101 Pipeline abandonment shall be planned and prepared.102 Pipeline abandonment evaluation shall include the fol-lowing aspects:

— relevant national regulations— health and safety of personnel, if the pipeline is to be

removed— environment, especially pollution— obstruction for ship traffic— obstruction for fishing activities— corrosion impact on other structures.

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SECTION 12DOCUMENTATION

A. GeneralA 100 Objective101 This section specifies the minimum requirements to doc-umentation needed for design, manufacturing / fabrication,installation, operation and abandonment of a pipeline system.The pipeline system phases are further described in Sec.3A 200.102 A Design Fabrication Installation (DFI) resumé, asdescribed in H, shall be established with the main objectivebeing to provide the operations organisation with a concen-trated summary of the most relevant data from the design, fab-rication and installation (incl. pre-commissioning) phase (seeB, C and D).103 An in-service file containing all relevant data achievedduring the operational phase of the pipeline system and withthe main objective to systemise information needed for integ-rity management and assessment of the pipeline system shallbe established and maintained for the whole service life (seeF200).104 For the design, fabrication and installation phase, allrequired documentation shall be reflected in a master docu-ment register (MDR).105 The required documentation for all phases of the pipe-line system’s lifetime shall be submitted to the relevant partiesfor acceptance or information as agreed.

B. DesignB 100 Structural101 A design basis for the pipeline system shall be estab-lished, including, but not limited to:

— safety objective— pipeline system description incl. location, general arrange-

ments, battery limits, inlet and outlet conditions— functional requirements including field development

restrictions, e.g. safety barriers and subsea valves— requirements to repair and replacement of pipeline sec-

tions, valves, actuators and fittings— project plans and schedule, including planned period of

the year for installation— design life including specification of start of design life,

e.g. installation, final commissioning, etc.— transport capacity and pipeline sizing data— attention to possible code breaks in the pipeline system— geometrical restrictions such as specifications of constant

internal diameter, requirement for fittings, valves, flangesand the use of flexible pipe or risers

— pigging requirements such as bend radius, pipe ovality anddistances between various fittings affecting design for pig-ging applications

— relevant pigging scenarios (inspection and cleaning)— pigging fluids to be used and handling of pigging fluids in

both end of pipeline including impact on process systems— topographical and bathymetrical conditions along the

intended pipeline route— geotechnical conditions— environmental conditions— operational conditions such as pressure, temperature, fluid

composition, flow rate, sand production etc. includingpossible changes during the pipeline system's design life

— principles for strength and in-place analysis

— corrosion control philosophy— second and third party activities.

102 The purpose of the design documentation is to ensure areliable pipeline system. The design shall be adequately docu-mented to enable second and/or third party verification. As aminimum, the following items shall be addressed:

— pipeline routing— physical and chemical characteristics of fluid— materials selection— temperature/pressure profile and pipeline expansion— strength analyses for riser and riser supports— all relevant strength and in-place stability analyses for

pipeline— relevant pipeline installation analysis— risk analysis as applicable— systematic review of threats in order to identify and eval-

uate the consequences of single failures and series of fail-ures (see Sec.2 B300)

— corrosion control (internal and external)— piggability— installation and commissioning.

103 Drawings shall be provided for the fabrication andinstallation of the pipeline system, including but not limited to:

— pipeline route drawings including information on, e.g. sea-bed properties and topology, existing and future platforms,pipelines/cables, subsea well heads, ship lanes, etc.

— alignment sheets— detailed pipeline crossing drawings— platform layout drawings with risers, riser protection sys-

tems, loading zones, boat landing areas, rescue areas, etc.as applicable

— spool fabrication drawing— other components within the pipeline system (connectors,

pigging loops etc.)— pipeline protection drawings— riser and riser clamp fabrication drawings— land ownership details.

B 200 Linepipe and pipeline components (including welding)201 The following documentation shall be established:

— material manufacturing specifications— welding and NDT specifications— material take off/data sheets.

B 300 Corrosion control systems and weight coating301 The following documentation shall be established, asapplicable:

— cathodic protection design report— anode manufacturing and installation specifications— anode drawings— coating manufacturing specifications— field joint coating specification(s)— corrosion monitoring system specification— material take off/data sheets.

Guidance note:The cathodic protection design report shall pay attention to thelandfall section (if any) and possible interaction with the relevantonshore CP-system.


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B 400 Installation401 The following documentation shall be established:

— Failure Mode Effect Analysis (FMEA) and HAZOP stud-ies (see Sec.10)

— installation and testing specifications and drawings— Welding Procedure Qualification (WPQ) records.

B 500 Operation501 Decisions and parameters having an impact on the oper-ational phase of the pipeline system such as:

— operation envelope— external and internal inspection strategies incl. piggability,

ROV surveys— measuring points for in-situ wall thickness measurements,

ER-probes, weight loss coupons, fluid monitoring etc.

shall be emphasised and documented in design.502 As a minimum, the following documentation shall beestablished:

— pipeline integrity management strategy covering strategiesfor corrosion control, inspection and maintenance

— emergency response strategy— emergency repair contingency strategy.

B 600 DFI-Resumé601 The Design part of the DFI-resumé shall be establishedand in accordance with the requirements given in H.

C. Construction - Manufacturing and Fabrication

C 100 Linepipe and pipeline component101 The documentation to be submitted for review prior tostart or during start-up of manufacturing shall include, but notbe limited to:

— Quality Plan (QP)— Manufacturing Procedure Specifications (MPS) including

test requirements and acceptance criteria— Manufacturing Procedure Qualification Test (MPQT)

results— manufacturing procedures (e.g. hydrostatic testing,

dimensional measurements, mechanical and corrosiontesting etc.)

— Welding Procedure Specifications (WPS), including pro-cedures for repair welding

— Welding Procedure Qualification (WPQ) records— Non Destructive Testing (NDT) procedures— Personnel qualification records (e.g. for welders and NDT

operators)— manufacturer's/fabricator's quality system manual.

102 The as built documentation to be submitted after manu-facturing shall include, but not be limited to:

— Quality Control (QC) procedures— Inspection and Test Plan (ITP)— traceability procedure— material certificates— Manufacturing Procedure Specifications (MPS) including

test requirements and acceptance criteria— results from MPQT— test procedures (e.g. hydrostatic testing, dimensional

measurements, mechanical and corrosion testing etc.)— mechanical test reports— hydrostatic testing report— weld log records

— consumable batch numbers— welder certificates — heat treatment records— NDT procedures and records— NDT operator certificates— dimensional reports— equipment calibration certificates/reports— storage procedures— release certificates— pipe tally sheet— complete statistics of chemical composition, mechanical

properties and dimensions for the quantity delivered.

C 200 Corrosion control system and weight coating 201 The documentation to be submitted for review prior tostart of manufacturing shall include, but not be limited to:

— manufacturing procedures, including inspection/testrequirements and acceptance criteria, repairs, documenta-tion, etc.

— documentation of materials and concrete mix design— Manufacturing Procedure Qualification Tests (MPQT)

results— quality plan with referenced procedures for inspection,

testing and calibrations — outline drawing of anodes.

202 The as built documentation to be submitted after manu-facturing shall include, but not be limited to:

— manufacturing procedures, including test requirementsand acceptance criteria, repairs, personnel qualificationrecords, etc.

— material certificates— production test records— complete statistics of coating dimensions, weight and neg-

ative buoyancy for the each joint delivered— repair log— electrical resistance test log.

C 300 DFI-resumé301 The Manufacturing / Fabrication part of the DFI-resuméshall be established and in accordance with the requirementsgiven in H.

D. Construction - Installation and Pre-Commissioning

D 100 General101 The documentation to be submitted for review prior tostart of installation shall include, but not be limited to:

— installation procedures for pipelines, risers, spools andcomponents including acceptance criteria, test certificatesfor equipment, qualification records for personnel (e.g.welding, coating), etc.

— installation procedures for protective structures (as mat-tresses etc.) and pipeline anchoring structures

— Installation Manuals (IM) procedures— trenching specification— intervention procedure— survey procedure— hydrotest procedures— pre-commissioning procedure, incl. procedures for dewa-

tering, cleaning, drying, flooding, mothballing,etc.:and— filling of fluid procedures

102 Documentation produced in connection with the pres-sure testing of the pipeline system shall include:

— pressure and temperature record charts

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— log of pressure and temperatures— calibration certificates for instruments and test equipment— calculation of air content— calculation of pressure and temperature relationship and

justification for acceptance— endorsed test acceptance certificate.

103 The as built documentation to be submitted after installa-tion and pre-commissioning shall include, but not be limited to:

— survey reports— updated drawings— intervention reports— pre-commissioning reports.

104 Records and documentations should include authorisa-tions and permits to operate.

D 200 DFI-Resumé201 The Installation (incl. pre-commissioning) part of theDFI-resumé shall be established and in accordance with therequirements given in H.

E. Operation - CommissioningE 100 General101 As a part of the commissioning (see Sec.11 B) the doc-umentation made available shall include, but not be limited to:

a) procedure and results from fluid filling operations withspecial emphasis on design parameters having an impacton the integrity of the pipeline system such as temperature,pressure and dew points

b) procedures and results from operational verification activ-ities (i.e. start-up inspection). Important parameters todocument are typically:

— expansion— movement— global buckling— wall thickness/metal loss.

c) inspection plans covering the future external and internalinspections of the pipeline system.

F. OperationF 100 General101 In order to maintain the integrity of the pipeline system,the documentation made available during the operationalphase shall include, but not be limited to:

— organisation chart showing the functions responsible forthe operation of the pipeline system

— personnel training and qualifications records— history of pipeline system operation with reference to

events which may have significance to design and safety— installation condition data as necessary for understanding

pipeline system design and configuration, e.g. previoussurvey reports, as-laid / as-built installation drawings andtest reports

— physical and chemical characteristics of transported mediaincluding sand data

— inspection and maintenance schedules and their records— inspection procedure and results covering the inspection

aspects described in Sec.11, including supporting records.

102 In case of mechanical damage or other abnormalities

that might impair the safety, reliability, strength and stabilityof the pipeline system, the following documentation shall, butnot be limited to, be prepared prior to start-up of the pipeline:

— description of the damage to the pipeline, its systems orcomponents with due reference to location, type, extent ofdamage and temporary measures, if any

— plans and full particulars of repairs, modifications andreplacements, including contingency measures

— further documentation with respect to particular repair,modification and replacement, as agreed upon in line withthose for the construction or installation phase.

103 In case of re-qualification of the pipeline system (seeSec.11 E), all information related to the re-assessment processof the original design shall be documented.

F 200 In-Service file201 The in-service file, as defined in Sec.11 C1100 shall asa minimum contain documentation regarding:

— results and conclusions from the in-service inspections— accidental events and damages to the pipeline system— intervention, repair, and modifications— operational data (fluid composition, flow rate, pressure,

temperature etc.) affecting corrosion and other deteriora-tion mechanisms.

G. AbandonmentG 100 General101 Records of abandoned pipelines shall be available andshall include but not be limited to:

— details of abandoned pipelines on land including routemaps, the size of the pipeline depth of burial and its loca-tion relative to surface features

— details of abandoned offshore pipelines, including naviga-tion charts showing the pipeline route.

H. DFI ResuméH 100 General101 A Design Fabrication Installation (DFI) Resumé shall beprepared to provide information for operation of the pipelinesystem. The DFI resumé shall clearly show the limits of thepipeline system, which shall be in accordance with Sec.1 C335or otherwise as agreed between Contractor and PipelineOwner. 102 The DFI Resumé shall reflect the as-built status of thepipeline system and shall provide information for preparationof plans for inspection and maintenance planning. 103 The DFI Resumé shall specify design and operatingpremises and requirements.104 The DFI Resumé shall contain all documentationrequired for normal operation, inspections and maintenanceand provide references to the documentation needed for anyrepair, modification or re-qualification of the pipeline system.105 The preparation of the DFI Resumé shall be carried outin parallel, and as an integrated part, of the design, fabricationand installation phase of the project.

H 200 DFI resumé content201 As a minimum, the DFI Resumé shall contain the belowlisted items:

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System description202 Shall include a description of the pipeline system includ-ing:

— final dimensions— final operational parameters— a table, for planning of future pigging operations, listing

all components in the system from pigtrap to pigtrap. Keydata like inner diameter (ID), bend radius and wall thick-ness (WT) should be included, as well as references toadditional documentation / drawings.

Document filing system203 Shall give an overview of as-built documentationincluding description of filing system and method.Design Basis204 Shall give a summary of the final design basis, on whichengineering, fabrication and installation is based. Designparameters of key importance for the operation of the pipelinesystem should be emphasised. The following parameters areconsidered important for the operation of the pipeline system:

— design life and limitations— design standards,— environmental conditions— tabulated geotechnical parameters as used in design— design pressure and temperature— flow rate— fluid composition— corrosion allowance— depth of cover— material specifications, covering pressure containing

equipment and structure— CP-system (i.e. anode details)— fatigue design assumptions incl. free span criteria— incidental pressure relief system— flow control techniques and requirements.

Design 205 Shall include a design activity resumé, all engineeringassumptions and assessments not listed in the design basis inaddition to applicable deviations and non-conformancesincluding a description of possible impact on the operationalphase.Fabrication206 Shall include a manufacturing / fabrication activityresumé, reference to specifications, drawings etc., discussionof problem areas and any deviations from specifications anddrawings of importance for the operational phase.Installation207 Shall include an installation activity resumé, referenceto specifications, drawings etc., discussion of problem areasand any deviations from specifications and drawings of impor-tance for the operational phase.Pre-commissioning208 Shall include a pre-commissioning activity resumé andany results from the pre-commissioning phase. All applicabledeviations and non-conformances shall be listed including a

description of possible impact on the operational phase. Certificate and Authority Approval209 Shall include a hierarchical overview of issued certifi-cates, release notes and authority approvals with reference toitems and nature of any conditional approvals. The certificates,release notes and authority approvals shall show unambiguousreference to applicable standards and documents, items cov-ered, accepted deviations, certification activities and conditionfor certificates.Surveys210 Shall give all engineering assumptions and assessmentsdrawn from the route and site surveys in addition to all appli-cable as-installed route drawings.Inspection, Maintenance and Repair211 Shall include an overview of:

— identified areas deemed to require special attention duringnormal operation of the pipeline system

— operational constraints

Deviations and Non-Conformances212 Shall include a complete list of waivers, deviations andnon-conformances with special emphasis on identified areasdeemed to require special attention during normal operation ofthe pipeline system.Selected Drawings213 Shall include a complete as-built drawing list, includingdrawings from sub-vendors and contractors, with reference tothe as-built filing system. Selected drawings from the design,fabrication and installation phase, as:

— drawings of special components— alignment sheets— as-installed route drawings

shall be included.

I. Filing of DocumentationI 100 General101 Maintenance of complete files of all relevant documen-tation during the life of the pipeline system is the responsibilityof the Owner, or for the operational phase the Operator.102 The DFI-resumé (see H200) and all documentationreferred to in the DFI Resumé shall by filed for the lifetime ofthe system. This includes also documentation from possiblemajor repair or re-construction of the pipeline system.103 The engineering documentation not mentioned in I102shall be filed by the Owner or by the engineering Contractorfor a minimum of 10 years. 104 Files to be kept from the operational phase of the pipe-line system shall as a minimum include final in-service (F200)inspection reports from start-up, periodical and special inspec-tions, condition monitoring records, and final reports of main-tenance and repair.

DET NORSKE VERITAS


SECTION 13COMMENTARY (INFORMATIVE)

A. GeneralA 100 ObjectiveThe objective of this section is to:

— give an overview of the standard by giving cross refer-ences to subjects covered in different sections

— give background information to the requirements in thestandard

— give guidance reflecting good engineering practice.

The section is informative only, and some of the recommenda-tions may not be founded on thorough work but engineeringjudgement only.

B. Cross References

Table 13-1 Index and cross references Key word Reference Comment or aspectCrossing Sec.2 B302 Evaluation of risks

Sec.3 C204 SurveySec.5 B105 Minimum vertical distanceSec.10 B300 Specification

Golden weld Sec.10 A807 RequirementsInstallation Sec.2 C400 Safety class

Sec.5 H102 Design criteriaSec.5 H200 Pipe straightnessSec.9 Installation

Material strength Sec.5 C302 fcTable 5-6 Relation to supplementary requirement UFigure 2 in Sec.5 Proposed (conservative) de-rating stressesTable 5-7 Reduction due to the UO/UOE process

Mill pressure test Sec.1 C200 DefinitionSec.5 B200 Link between mill pressure test and designSec.5 D201 Reduced mill test pressure implication on pressure containment capacitySec.7 E100 Basic RequirementSec.7 E105 Maximum test pressureSec.7 E107 Waiving of mill test – UOE-pipes, conditions

Minimum wall thickness Table 5-3 Minimum 12 mm and when it appliesTable 5-2 When to use minimum wall thickness, relation to nominal thickness and corrosion

allowanceOvality Eq. (5.13) Minimum allowed ovality for collapse

Sec.5 D901 Maximum allowed ovality, as installedTable 7-17 and Table 7-26 Maximum allowed ovality (Out-of roundness), line pipe specification

Pressure - general Sec.1 C200 DefinitionsSec.3 B300 Pressure protection systemTable 4-1 Pressure termsTable 4-3 Characteristic values

Pressure – incidental Sec.13 E500 Benefit of lower incidental pressureSec.3 B300 Pressure protection systemTable 3-1 Incidental to design pressure ratios

Reeling Table 5-10 Fracture assessment – when supplementary requirement P comes into forceAppendix A Engineering critical assessmentEq. (5.31) Capacity formulaTable 4-5 Condition factorSec.7 I300 Supplementary requirement PSec.7 I400 Supplementary requirement DSec.10 E Testing

Spiral welded Sec.5 A205 Requirements

DET NORSKE VERITAS


C. Design PhilosophyC 100 Safety Class discussionSafety class shall be specified for each part of the pipeline andfor each phase. The classification shall be based on the require-ments in Sec.2.The safety class concept allows the owner some flexibility interms of risk which is both a reasonable and rational approach,e.g. this allows the owner to differentiate between the designconservatism for a flow line with a 5 year design life and atrunk line with 40 years design life.The main aspect when determining the safety class is the con-sequence, typically to people, environment and cost. Note thatthis consequence not necessarily is limited to failure of theconsidered pipeline itself, but also to its impact on the totalexploration. One such example may be reduction in productionif a water injection line or a system for waste water fails whichfrom an isolated point of view could be defined as safety classlow.Another example is differentiation of temporary phases. A fail-

ure during installation, normally considered as safety classlow, will have a significantly smaller consequence than a fail-ure during a shut-down period of the pipeline, where both pol-lution and time for repair are significantly more expensive andtime consuming.However, the total safety may not always be increased by spec-ifying a higher safety class. This may be the case when themost probable cause of failure would be draught of vessel,where the emphasis should be put on operating procedures andback-up. During such circumstances, it may not be requiredwith a higher safety class.The above clearly illustrates that Table 2-4 is for “Nor-mal”classification only, as stated.

C 200 Structural reliability analysesStructural reliability methods consider structural analysismodels in conjunction with available information regardingthe involved variables and their associated uncertainties. Thereliability as assessed by reliability methods is not an objectivephysical property of the pipeline itself in the given operationaland environmental condition, but rather a nominal measure of

Strain hardening Eq. 5.30, Eq. 5.31 In capacity formula; strainEq. 5.19 (through Eq. 5.22) Capacity formula SMYS/SMTS - (in αc)Table 7-5 and Table 7-11 SMYS and SMTSTable 7-5 and Table 7-11 αh (YS/UTS)

System pressure test Sec.1 C200 DefinitionSec.5 B200 Link to designSec.5 B203 RequirementsTable 5-1 Waiving of system pressure testSec.5 B205 Safety class during system pressure testSec.5 D200 Limit state check - pressure containmentSec.5 D300 Limit state check - local bucklingSec.10 O500 Execution of the test (filling, holding time etc.)

Weld onto pipe Sec.5 B108 Requirements for doubler plates etc.

Table 13-2 Characteristic material properties for designSymbol Description Reference Pressure

containmentLocal buckling

Collapse Load Controlled

Displacement Controlled

Propagating buckling

Elastic propertiesE Young’s modulus Xν Poisson’s ratio Xα Temperature expansion, as

function of the temperature (within the actual temperature range)

X

Plastic propertiesSMYS Specified minimum yield stress Table 7-5 and Table

7-11X X X X X

fy, temp Yield stress temperature derat-ing value

Figure 2in Sec.5

X X X X X

SMTS Specified minimum tensile strength


X - X - -

fu, temp Tensile strength temperature derating value

Sec.5 C304 GN X - X - -

α fab Fabrication factor Table 5-7 - X (X) (X) XPlastic properties depending on additional requirementsαu(U) increased utilisation Table 5-6 X X X X Xαh(P) Strain hardening value Table 7-5 and

Table 7-11- - - X -

αc(U) Flow stress parameter Eq 5.22 - - X - -

Table 13-1 Index and cross references (Continued) Key word Reference Comment or aspect

DET NORSKE VERITAS


the reliability given a particular physical and probabilisticmodelling and analysis procedure applied.Structural reliability analysis is only one part of a total safetyconcept as gross errors are not included. A gross error isdefined as a human mistake during the design, construction,installation or operation of the pipeline that may lead to asafety level far below what is normally aimed for by use of apartial safety factor design format or specific reliability analy-sis. In the following only natural variability are discussed andthe corresponding probabilities are referred to as Nominalthroughout this standard.Nominal target reliabilities have to be met in design in order toensure that certain safety levels are achieved. A probabilisticdesign check can be performed using the following design for-mat:Pf,calculated < Pf,,T Pf,calculated is the calculated nominal probability of failureevaluated by a recognised (accepted) reliability method andpf,T is a nominal target value that should be fulfilled for adesign to be accepted.Acceptable nominal failure probabilities depend in general onthe consequence and nature of failure, the risk of human injury,economic losses, social (political) inconvenience and theexpense and effort required to reduce the failure probability.Failure statistics may be used as guidance on relative failureprobability levels but only limited information about specificfailure probability for SLS, ULS and FLS can be deduced fromfailure statistics. Structural (nominal) failure probability froma SRA is a nominal value and cannot be interpreted as anexpected frequency of failure.

C 300 Characteristic valuesIn a LRFD format, so called characteristic values are used.These are often lower fractiles for strength and resistance, notalways however, and upper fractiles for loads. Typical exam-ples of these may be SMYS for the yield stress and 100-yearwaves for loads.The characteristic value in the resistance formulas is a lowerfractile and the expected yield stress is typically in the order of8% higher. On commonly overlooked implication of this isthat it is not allowed to replace the fy based upon a certificateor test. Such a replacement requires a thorough evaluation bya reliability specialist.

D. LoadsD 100 Conversion of pressuresThe governing pressure for design is the incidental pressure.The incidental pressure is normally defined as the pressurewith an annual probability of exceedance of 10-2

If the design pressure is given, the incidental pressure shall bedetermined based on the pressure control system and the pres-sure safety system tolerances and capabilities to ensure that thelocal incidental pressure meets the given annual probability ofexceedance above. If the pressure not can exceed the design pressure, e.g. fullshut-in pressure is used, the incidental pressure may bereduced to the design pressure, see Table 3-1. It is expectedthat the operating pressure of a well stream designed for theshut-in pressure is at least 5% less than the shut-in pressure. i.e.only incidental operations are expected to be in the upper 5%of the incidental pressure.Different systems may have different definitions of designpressure and incidental pressure, e.g. between topside and apipeline system. When converting the defined pressures in onesystem to pressure in another system, the conversion shall be

based on pressure having an annual probability of exceedanceless than 10-2. This pressure shall then be defined as the inci-dental pressure in the pipeline system. Determination of designpressure shall then be made based on the above principles.For pipeline systems with a two peak annual extreme pressuredistribution, special considerations are required. Reference isgiven to E600.

E. Design Criteria

E 100 GeneralThe basis for most of the given limit states were developedwithin the joint industry project SUPERB and the reports maybe bought from Sintef, Norway. Some results have been pub-lished, e.g. Jiao et al (1996) and Mørk et al (1997).The SUPERB results were incorporated in DNV Rules forSubmarine Pipeline Systems, 1996 (DNV'96) and modified inorder to allow for additional aspects, not necessarily to be con-sidered in a research project. Hence, all limit states may nothave identical partial factors as in the SUPERB reports.In the 2000 revision of this standard, the LRFD format wasmodified on the resistance side as described in Sec.2 and thelimit states from DNV'96 modified correspondingly. The localbuckling formulation included some results from the Hotpipeproject, allowing a higher utilisation of pressurised pipes. Seee.g. Vitali et al (1999). In this revision, this has been furtherimproved to allow for higher utilisation for pressurised pipes.The characteristic pressure is now incidental pressure for alllimit states.A table specifying the combinations of characteristic loadshave been included in Sec.4. This is not intended to be differ-ent from the 2000 revision (with exception of use of the inci-dental pressure and that interference loads is a separate loadcategory), only a interpretation given explicitly.

E 200 Condition load effect factorsThe load condition factor γC = 1.07, pipeline resting on unevenseabed refers to the load effect uncertainty due to variation inweight, stiffness, span length or heights. This implies that it isnot applicable for the sag bend evaluation during installationon uneven seabed.A γC lower than unity is e.g. used in DNV-RP-F110 GlobalBuckling of Submarine Pipelines – Structural Design due toHigh Temperature/High Pressure, to represent the degree ofdisplacement control and uncertainties in, primarily, the pipe-soil properties.

E 300 Calculation of nominal thicknessThe negative fabrication tolerance is normally given as a per-centage of the nominal thickness for seamless pipes, and as anabsolute measure for welded pipes.The pressure containment criterion gives a minimum requiredminimum wall thickness, t1. Depending on the fabrication tol-erance format, the implication of the corrosion allowance willbe different. For a fabrication tolerance given as a percentage,% tfab, Eq. (13.1) applies.

Correspondingly, the nominal thickness based on an absolutefabrication tolerance, tfab, is given by Eq. (13.2).

(13.1)

(13.2)

tt1 tcorr+1 %tfab–----------------------=

t t1 tcorr tfab+ +=

DET NORSKE VERITAS


E 400 Pressure containment - equivalent formatThe format of the pressure containment resistance in Sec.5 isgiven in a LRFD format. This corresponds to the traditionalformat, which usually is expressed in terms of allowable hoopstress, is given in Eq. (13.3).

The differential pressure is here given as a function of the localincidental pressure. Introducing a load factor, γinc, reflectingthe ratio between the incidental pressure and the design pres-sure, the formula can be rearranged for the reference pointabove water, as given in Eq. (13.4).

Introducing a usage factor as given in (13.5), the criteria can begiven as in Eq. (13.6) and Eq. (13.7).

The corresponding usage factors for γinc = 1.10 (10% inciden-tal pressure) are given in Table 12-3.

E 500 Pressure containment criterion, incidental pressure less than 10% above the design pres-sure.The governing pressure when determining the wall thickness isthe local incidental pressure. The pipeline system shall have apressure safety system which ensures that there is a low life-time probability for exceeding the local incidental pressure atany point in the system. If this is achieved for an incidentalpressure which is 10% above the design pressure, this givesone wall thickness.However, a better control system which can guarantee thesame probability for an incidental pressure 5% above thedesign pressure, a correspondingly smaller wall thickness isrequired. This is reflected by a lower γinc in (13.5) and will typ-ically apply to hydraulicly “softer” systems like gas trunklines.

E 600 HIPPS and similar systemsA pipeline will always have an operating pressure lower thanthe design pressure due to the pressure drop caused by the flowof the fluid.For high pressure wells, this downstream pressure may be

reduced on purpose by a choke in order to enable a lower pres-sure pipeline downstream. This reduced pressure is dependenton a constant flow and will increase to the shut-in pressure incase of blockage downstream.A High Integrity Pressure Protection System (HIPPS) servethe purpose to protect the downstream pipeline from the shut-in pressure by stopping the flow in case a pressure increase isexperience (due to some blocking down-stream). The closerthis blockage is to the HIPPS, the faster will the pressureincrease occur. Hence, the speed of this HIPPS will determinehow long part of the pipeline downstream that not can be pro-tected but designed for the full shut-in pressure. This part isreferred to as the fortified zone.In case of failure of this HIPP system, the downstream pipelinewill experience the full shut-in pressure. In order to takeadvantage of a HIPP system, the annual probability of this tohappen must be less than 10-2. The resulting annual extreme pressure distribution will then besimilar to Figure 1, a two peak distribution where the rightpeak describes the pressure distribution in case of failure of theHIPPS.

Figure 1

From the example in the figure, it is evident that the over pres-sure scenario will burst the pipeline (a factor 2.5 times the inci-dental pressure).For a failure probability less than 10-2 this over-pressure maybe considered as an accidental limit state and the methodologyin Sec.5 D1200 may be used. The wall thickness will then bethe larger of the pressure containment criterion based:

— on the choke pressure and — the accidental scenario of the shut-in pressure.

With the example in Figure 1 the accidental scenario will gov-ern the wall thickness design. If the over pressure would havebeen less than 20-30% above the incidental pressure, the chokepressure may govern the design.The accidental criterion is:

where pf|Di is the failure probability given that the scenariohappens and PDi is the probability of the scenario to happen. Inthe following, it is assumed that the over pressure scenario willbe the overall contributing accidental scenario and the summa-tion sign is neglected.

(13.3)

(13.4)

(13.5)

(13.6)

(13.7)

Table 13-3 "Usage factors" μ for pressure containmentUtilisation factor,αU

Safety Class Pressure testLow Medium High

1.00 0.8473(0.843)

0.802 0.6981 0.96

0.96 0.8133(0.838)

0.77 0.672 0.96

In location class 1, 0.802 may be usedIn location class 1, 0.77 may be usedEffectively this factor since the pressure test is governing

)(3

22

)( ,1

1tempy

SCm

Ueli fSMYS

ttD

pp −⋅⋅⋅

⋅≤

⋅−

−γγ

α

)(3

22 ,

1

1tempy

incSCm

Ud fSMYS

ttD

p −⋅⋅⋅⋅

⋅≤

⋅−

γγγα

incSCm

U

γγγα

η⋅⋅⋅

⋅=

32

)(2 ,

1

1tempyd fSMYS

ttD

p −⋅≤⋅−

η

)(15.12 ,

1

1tempud fSMTS

ttD

p −⋅≤⋅− η

(13.8)

0 1 2 3 4

Normalised pressure

Prob

abili

ty D

ensi

ty

TfDiDif pPp ,| ≤⋅∑

DET NORSKE VERITAS


For the HIPPS scenario outlined above, the probability of thescenario, PDi, will be equal to the probability of a blockage tohappen times the on-demand-failure of the HIPPS.

The resulting wall thickness for the accidental scenario willthen be the wall thickness giving the failure probabilityrequired in accordance with 13.8Note that the target failure probability in accordance withSec.2 primarily shall be equal to similar limit states. The fail-ure probability of the pressure containment criterion is at leastone order of magnitude less than the target values in Table 2-5.

E 700 Local buckling - CollapseThe collapse pressure, pc, is a function of the:

— elastic capacity— plastic capacity— the ovality.

The formulation adopted in this standard is identical as inBS8010, apart from the safety margin. The formula is given inEq. (13.10) with the defined elastic and plastic capacities inEq. (13.11) and Eq. (13.12).

This third degree polynomial has the following analytical solu-tion:

where:

E 800 Buckle arrestorThe buckle arrestor formula in Sec.5 is taken from Torsellettiet al.

E 900 Local buckling - MomentThe given formula is valid for 15 < D/t < 60 for yielding andovalisation failure modes. Up to D/t equal to 45, these failuremodes will occur prior to other failure modes, e.g. elastic buck-ling, and hence do not need to be checked.Over D/t 45, elastic buckling has to be checked separately, typ-ically through FE analysis, with D/t a sufficient "safety mar-gin" above the actual D/t in order to account for bothuncertainty as well as natural thickness variations.In addition to check for elastic buckling, a thinner pipebecomes more susceptible to imperfections. Special consider-ations shall be made to

— girth welds and mismatch at girth welds, and— point loads, e.g. point supports.

If both the elastic buckling has been documented to occurbeyond the valid range and the implications of imperfectionshas found to be acceptable, the criteria may be extended to D/t = 60.

E 1000 Local buckling - Girth weld factorResearch on buckling of pipes including girth welds has shownthat the girth weld has a significant impact on the compressivestrain capacity, see Ghodsi et al (1994). A reduction in theorder of 40% was found for D/t = 60. There are no other knownexperiments on the impact from girth welds for lower D/t.It is assumed that the detrimental effect is due to on-set ofbuckling due to imperfections at the weld on the compressiveside. If this is true, this effect will be more pronounced forhigher D/t's. The girth weld factor should be established by testand/or FE-calculations.If no other information exists and given that the reduction isdue to the misalignment on the compressive side, the reductionis expected to negligible at D/t = 20. A linear interpolation isthen proposed up to D/t = 60.If no other information exists then the following girth weld fac-tor is proposed.

Figure 2 Proposed girth weld factors

E 1100 OvalisationPipe ovalisation is mentioned in three different places withinthis standard:Sec.5 D900, where the maximum allowable ovalisation f0 =3%. This applies for the pipeline as installed condition. Thislimitation is due to the given resistance formulations which notincludes the ovality explicitly, as well as other functionalaspects as stated in the paragraph.Sec.5 D401, where the minimum ovalisation f0 = 0.5% to beaccounted for in the system collapse check; and the combinedloading. The collapse formula includes the ovality explicitlygiving a lower resistance for a larger ovality, hence a minimumovality is prescribed.

PDi = Pblockage · Pfailure on demand(HIPPS) (13.9)

(13.10)

(13.11)

(13.12)

(13.13)

( ) ( )( ) ( ) ( )( ) ( ) ( ) ( )tptptptptptptp pelcpcelc ⋅⋅⋅=−⋅− 22

( ) 2

3

1

2

ν−

⎟⎠⎞

⎜⎝⎛⋅⋅

= DtE

tpel

( )D

tftp fabyp⋅

⋅⋅=2α

pc y 13---

b–=

( )tpb el−=

2)()( tptpd pel=

u 13--- -1

3---b2 c+⎝ ⎠

⎛ ⎞=

v 12---

227------b3 1

3---bc d+–⎝ ⎠

⎛ ⎞=

Φ cos 1– v–

u– 3-------------

⎝ ⎠⎜ ⎟⎛ ⎞

=

⎟⎠⎞

⎜⎝⎛ +

Φ−−=

18060

3cos2 πuy

DET NORSKE VERITAS


Table 7-17, dimensional requirements, where the maximumallowable out of roundness to be delivered from Manufactureris specified.The ovality of a pipe exposed to bending strain may be esti-mated by Eq. (13.14). This is a characteristic formula withoutany safety factors.

For further information, reference is made to Murphey (1985)

F. API Material GradesF 100 API material gradesThe API requirements to the Grades X42 through X80 arelisted in Table 13-4. For full details see the API Specificationfor Line Pipe (API Specification 5L). The SMYS and SMTSvalues given in MPa in the table below are converted from theAPI specification (in ksi), and differ slightly from the mechan-ical properties in Sec.7 Table 7-5, which apply for this stand-ard.

G. Components and AssembliesG 100 Riser SupportsRiser Supports are to be designed to ensure a smooth transitionof forces between Riser and support.Inspection/control methods are to be specified so that properInstallation is ensured, in accordance with the design assump-tions.Where the Riser Support relies on friction to transfer load,appropriate analytical methods or experimental test results areto be used to demonstrate that adequate load transfer will bedeveloped and maintained during the life of the structure. Thedesign of the studbolts is to be such that it is possible to moni-tor the remaining bolt tension during the design life time. Thiscan be done by utilising mechanical bolt load indicators insome of the studbolts in each connection.The minimum remaining pretension level in the studbolts atwhich pre-tensioning must be performed is to be determinedduring the design phase.The design is to be such that all the studbolts in one connectioncan be pre-tensioned simultaneously by means of bolt tension-ing jacks.All relevant loads are to be considered when calculating the

fatigue life of the Riser Supports.

G 200 J-tubesThe J-tube system is to be designed to perform satisfactorilyduring its entire planned life. It is to be designed against rele-vant failure modes.The routing is to be based on the following considerations:

— platform configuration and topsides layout— space requirements— movements of the J-tube— cable/Pipeline approach— J-tube protection— in-service inspection and maintenance— Installation considerations.

The J-tube spools are normally to be joined by welding.For J-tubes, loads during Installation include:

— load-out— transportation— lifting— launching— upending— docking— pressure testing— temporary supporting.

The effect of deflections due to a connected Pipeline's thermalexpansion or contraction is to be taken into account.Loads caused by deflections of the J-tube, or the structure towhich the support is attached, are to be considered.Loads on the J-tube and supports as a result of foundation set-tlements are to be considered. Accidental loads are loads towhich the J-tube and support system may be subjected in con-nection with incorrect operation or technical failure such asfire, explosions and impact loads. The relevant accidentalloads and their magnitude are to be determined on the basis ofa risk analysis.The effect of impact by vessels is to be considered for the J-tube and support system within the splash zone. Normally theJ-tubes and supports are to be routed inside the structure toavoid vessel impact.Consideration is to be given to accidental loads caused by fall-ing objects such as:

— falling cargo from lifting gear— falling lifting gear— unintentionally swinging objects.

H. InstallationH 100 Safety class definitionInstallation of pipeline and pipeline components is normallydefined as safety class Low. However, if the installation activ-ity impose a higher risk to personnel, environment or theassets, a higher "safety class" should be used. Such activitiesmay typically be repair, where the system is shut down, but theproduction medium is still within the system, modifications toexisting system or installation operations where failure maylead to extensive economic loss.

H 200 CoatingIn case no other data is available the following criterion shouldbe used. The mean overbend strain:

(13.14)

Table 13-4 API Material GradesAPI Grade

SMYS SMTSksi MPa ksi MPa

X42 42 289 60 413X46 46 317 63 434X52 52 358 66 455X56 56 386 71 489X60 60 413 75 517X65 65 448 77 530X70 70 482 82 565X80 80 551 90 620ksi = 6.895 MPa; 1 MPa = 0.145 ksi; ksi = 1000 psi (lb f/in2)

f0′f0 0.030 1 D

120t-----------+⎝ ⎠⎛ ⎞ 2εc

Dt----⎝ ⎠

⎛ ⎞ 2+

1PePc-----–

------------------------------------------------------------------------------=

(13.15)emeanD2R------- eaxial+–=

DET NORSKE VERITAS


should satisfy:

where

D = outer steel diameterR = stinger radiusεmean = calculated mean overbend strainεaxial = axial strain contributionεcc = 1.05 safety factor for concrete crushingεcc = limit mean strain giving crushing of the concrete.

Positive strain denotes tensile strain.The mean overbend strain at which concrete crushing firstoccurs depends on the pipe stiffness, the concrete strength andthickness, the axial force and the shear resistance of the corro-sion coating. Crushing occurs at lower mean overbend strainsfor lower concrete strength, lower axial force, higher pipe stiff-ness and higher shear resistance. If no other information isavailable, concrete crushing may be assumed to occur whenthe strain in the concrete (at the compressive fibre in the mid-dle of the concrete thickness) reaches 0.2%.For concrete coating of 40 mm thickness or more, togetherwith asphalt corrosion coating, a conservative estimate of εccis 0.22% for 42" pipelines and 0.24% for 16" pipelines, withlinear interpolation in between.Reference is made to Endal (1995) or Ness (1995).

H 300 Simplified laying criteriaThis simplified laying criteria may be used as a preliminarysimplified criterion of the local buckling check during earlydesign stages. It does not supersede any of the failure modechecks as given in the normative part of the standard.In addition to the simplified stress criteria given below, thelimit states for Concrete Crushing (K200), Fatigue (Sec.5D700) and Rotation (Sec.5 H203) shall be satisfied. Referenceis further made to Endal et. al. (1995) for guidance on the Rota-tion limit state.OverbendFor static loading the calculated strain shall satisfy Criterion Iin Table 13-5. The strain shall include effects of bending, axialforce and local roller loads. Effects due to varying stiffness(e.g. strain concentration at field joints or buckle arrestors)need not be included.For static plus dynamic loading the calculated strain shall sat-isfy Criterion II in Table 13-5. The strain shall include alleffects, including varying stiffness due to field joints or bucklearrestors.

SagbendFor combined static and dynamic loads the equivalent stress inthe sagbend and at the stinger tip shall be less than

with all load effect factors set to unity.Effects due to varying stiffness or residual strain from the over-bend may be ignored.For the sagbend in deeper water, where collapse is a potentialproblem, the normative buckling criteria in the standard shallalso be satisfied.

Calculation requirementsThe following requirements to the lay analysis apply bothwhen using Limit State Criteria and Simplified Criteria:

— The analysis shall be conducted using a realistic non-linearstress-strain (or moment-curvature) representation of thematerial (or cross-section).

— For calculation of strain concentration at field joints, non-linear material properties of the steel, the concrete and thecorrosion coating shall be considered.

— The characteristic environmental load during installationis to be taken as the most probable largest value for thesea-state (Hs, Tp) considered with appropriate current andwind conditions. The sea-state duration considered is notto be less than 3 hrs.

— If the dynamic lay analysis is based on regular waves, itshall be documented that the choice of wave heights andperiods conservatively represents the irregular sea-state(Hs, Tp).

H 400 ReelingA pipeline that is reeled onto a spool will be subjected to largeplastic strains. When two abutting pipe joints have dissimilartangential stiffness, e.g. due to different wall thickness or var-ying material properties, a discontinuity will occur. The resultof this is a concentration of compressive strains in the softerjoint in an area close to the weld. Experience has shown thatvariations in properties (within fabrication tolerances) maycause the pipe to buckle.Figure 4 and Figure 5 attempt to illustrate the reeling situationfrom two different points of view. It is recognised that theseillustrations, and the description below, are simplified and onlytake into account global effects.In Figure 4 the sudden increased curvature is visualised bylooking at the moment curvature relationship for the two abut-ting joints. It is seen that the required moment equilibriumacross the weld will lead to an increase in curvature in theweaker pipe. This figure also shows clearly that an increasedstiffness difference will increase the sudden increase in curva-ture in the weaker joint.

Figure 3 Moment curvature relationship for plastic bending of pipes withdifferent stiffness.

Figure 3 provides a different illustration: The distribution ofmoment and corresponding tangential stiffness is schemati-cally plotted along the pipeline.At the left hand side of the figure the pipe is assumed to lietight onto the reel with a constant bending moment well intothe plastic regime. From the point where the pipe first touchesthe reel, to the point at the right hand side where back tensionis applied, the moment is assumed to decay linearly to zero.

(13.16)

Table 13-5 Simplified criteria, overbendCriterion X70 X65 X60 X52I 0.270% 0.250% 0.230% 0.205%II 0.325% 0.305% 0.290% 0.260%

σeq < 0.87 times fy (13.17)

γccemean ecc≥

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(Note that this moment will not vanish if the caterpillars,through which the back tension is applied, restrain rotation.)Furthermore, Figure 4 illustrates the scenario where a fieldjoint approaches the reel and a weak/soft joint follows astronger/stiffer one.

The lower part of this figure shows the tangential stiffnessalong the pipeline. Attention should be paid to the sudden dropin stiffness at the weld. It is obvious that this loss of stiffnesswill attract deformations, i.e. increased curvature in the weakerpipe close to the weld.

Figure 4 Schematic illustration of bending moment and stiffness along the pipe

FE analyses have shown that the most important parameters,with respect to stiffness variations are variations, in yield stressand wall thickness. Under disadvantageous circumstances,variations within normal fabrication tolerances may lead tobuckling of the pipe cross section.Over-matching (girth) weld materials are often used in pipes.These will introduce stiffness variations, however the effect ofthese are not normally significant from a buckling point of view.If a thick and relatively stiff coating is applied with gaps acrossfield joints, stress concentrations due to variations in yieldstress and wall thickness will be amplified.Analyses have also shown that accurate non-linear materialmodelling is essential for the accuracy of FE analyses. Espe-cially important in this respect is the tangential material stiff-ness, often defined through the yield stress to ultimate stressratio, SMYS/SMTS. High ratios increase significantly the

cross section's tendency to buckle. Obviously a high D/t ratiowill have a similar effect.During reeling, application of a high back tension is the majorremedy available for reducing the possibility for pipe buckling,and both practical experience and FE analyses have shown thatthis is a viable and mitigating measure in this context.Hence: in order to reduce the probability of buckling duringreeling, one should:

— specify a low thickness fabrication tolerance,— specify a low variation in yield stress,— specify a low yield stress to ultimate stress ratio— apply a high and steady back tension during reeling.

For further information, reference is made to Crome (1999),Brown et al (2004).

Moment moment at reel curvature

weld

elastic moment for stiffer pipe elastic moment for softer pipe

on reel plastified elastic plastified elastic

Stiffness

Pipe axis

on reel plastified elastic plastified elastic

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I. ReferencesBrown G., Tkaczyk T., Howard B. “Reliability based assess-ment of minimum reelable wall thicknesss for reeling” Pro-ceedings of IPC04-0733, IPC Calgary, Alberta, Canada 2004Crome, Tim; "Reeling of Pipelines with Thick Insulating Coat-ing, Finite Element Analyses of Local Buckling", OTC, Hou-ston, 1999.Endal G., Ness O. B., Verley R., Holthe K. and Ramseth S;"Behaviour of Offshore Pipelines Subjected to Residual Cur-vature During Laying", Proceedings of OMAE'95 conference,Copenhagen, DenmarkGhodsi Nader Yoosef-, Kulak G. L. and Murray D. W.;"Behaviour of Girth Welded Line-pipe", University of Albertadepartment of Civil Engineering, Structural EngineeringReport No. 23, 1994Jiao G., Sotberg T., Bruschi R., Verley R. and Mørk K; "TheSUPERB Project: Wall Thickness Design Guideline for Pres-sure Containment of Offshore Pipelines", Proceedings ofOMAE'96 conference, Florence, Italy

Murphey D.E. and Langner C. G. "Ultimate pipe strengthunder bending collapse and fatigue", Offshore Mechanics andArctic Engineering symposium, New Orleans 1985.Mørk. K, Spiten J., Torselletti E., Ness O. B., and Verley R.;"The SUPERB Project and DNV'96: Buckling and CollapseLimit State", Proceedings of OMAE'97 conference, Yoko-hama, JapanNess O. B. and Verley R.; "Strain Concentrations in Pipelineswith Concrete Coating: An Analytical Model", Proceedings ofOMAE'95 conference, Copenhagen, DenmarkSriskandarajah T. and Mamendran, I. K.; "Parametric consid-erations of design and installation of deepwater pipelins", Off-shore Oil and Gas Pipeline Technology, London, 1987Torseletti E., Bruschi R., Marchesani F., Vitali L. “BucklePropagation and its Arrest: Buckle Arrestor Design VersusNumerical Analyses and Experiments” OMAE2003-37220Vitali L., Bruschi R., Mørk K., Verley R.(1999); "Hotpipeproject - Capacity of pipes subjected to internal pressure, axialforce and bending moment", Proc. 9th Int. Offshore and PolarEngineering Conference, Brest 1999.

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Offshore Standard DNV-OS-F101, October 2007 – App.A

APPENDIX A STRUCTURAL INTEGRITY OF GIRTH WELDS IN OFFSHORE PIPELINES

A. GeneralA 100 Objective101 The objective of this Appendix is to:Provide detailed procedures and recommendations for evalua-tion of the integrity of girth welds considering weld disconti-nuities during installation and operationReferenced Standards102 The following standards are referred to in this appendix:BS 7448BS 7910DNV-RP-C203DNV-RP-F108

A 200 Introduction201 The purpose of the structural integrity evaluation ofwelds in pipelines is to avoid failure during the installation andoperation stages by determining the criticality of flaws. Theprocedures described are based on fracture mechanics and theterm “Engineering Critical Assessment” (ECA) is used. Bothstatic and dynamic strains (fatigue) are considered as relevant.Typically the assessments are used to:

a) Derive flaw acceptance criteria from the ECA results(where applicable) in line with Appendix D andAppendix E.

b) Perform fitness-for-purpose evaluations, e.g.:

— to avoid failures during installation and/or operation— to assess the effect of changed operational conditions

(temperature, strain level, lifetime extension etc.)— to assess the significance of weld flaws or damage

incurred after installation.

202 For girth welds, it is the pipeline longitudinal stress-strain condition that is of relevance during installation. Allstrain requirements/limitations for girth welds are defined asthe total nominal strain (elastic plus plastic), εl,nom in the pipelongitudinal direction. The total nominal strain may be inclu-sive of global stiffness disruption effects such as concrete coat-ing discontinuity (if applicable) at the field joint. However, anyother local effects, such as wall thickness mismatch and jointmisalignment effects, etc., shall be considered/analysed withthe methodology presented herein. For assessments of theoperational stage, the effect of circumferential stresses alsoneed to be considered, see B103, C104, D103 and E206.203 Failures are assumed to be avoided if:

— the maximum longitudinal strain, εl,nom is not larger than0.4%

— the maximum size of weld defects is in accordance withAppendix D

— the material is in accordance with Sec.6 and 7— the girth welds have acceptable fatigue capacity according

to Sec.5 D800, or— an ECA is performed as specified in this Appendix and

acceptance criteria are determined in accordance withAppendix D and Appendix E as relevant.

204 The fracture toughness requirements specified in thisAppendix is expressed in terms of the J value. However, theECA may be expressed in terms of the crack tip opening dis-placement (CTOD) provided that the assessment procedure

can be demonstrated to be conservative. G106 shows a con-servative way of estimating the corresponding CTOD fracturetoughness from a J fracture toughness test.205 The fatigue assessment procedure described in thisAppendix (Subsection F) is supplementary to the fatiguedesign guidance described in the main body of this document(the S-N approach). Assessment of the fatigue life should sat-isfy the requirement listed here and described in Sec.5 D800.

A 300 Application301 The ECA procedures described in this Appendix areonly applicable to C-Mn steels with SMYS up to 555 MPa,13Cr martensitic stainless steel, 22Cr and 25Cr duplex stain-less steels. Special advice must be sought if any other type ofpipeline materials is used.302 In general, procedures for assessing girth welds underload- and strain-based conditions are described. The proce-dures are also applicable for assessing flaws in parent pipe.303 This Appendix is not applicable to flexible pipes ordynamic or compliant risers.304 The integrity of welds in lined and clad pipelines may beevaluated according to the procedures described in this appen-dix, but special considerations apply, see C105, D103, E206,F108, H101 and Appendix B.305 Some materials are sensitive to environmentally inducedembrittlement, e.g. due to hydrogen from sour service orcathodic protection. In such cases the choice of toughness andfatigue properties shall reflect the actual environment. See alsoG105.306 This Appendix is not applicable where the yield and/ortensile stress of the weld is under-matched with respect to theparent pipe material. In such cases specialist advice shall besought.307 It is possible to estimate KIC from Charpy V-notch testresults using correlation formulas. The results are howeverconsidered to be less reliable and it is not acceptable to assessthe integrity of pipeline girth welds in accordance with thisAppendix based on Charpy V-notch testing only. Such assess-ments are only considered as indications.308 The fracture toughness properties will normally bedetermined from a fracture toughness test programme usingsingle edge notched tensile (SENT) specimens in accordancewith Subsection G, Appendix B and DNV-RP-F108. However,other fracture toughness test methods and specimengeometries may be used provided that it can be demonstratedthat these test techniques are conservative in relation to theirapplication.

Guidance note:The ECA procedures described in this Appendix requires thatfracture toughness testing is performed. Hence, the pipe dimen-sions which may be assessed according to this Appendix dependon the limitations with respect to the fracture toughness testing.It is recommended that the dimensions of SENT specimens arenot less than W = 8 mm and B shall be at least equal to W, seeFigure 1. It is possible that B = 2W and the specimens shall be aslarge as possible, see DNV-RP-F108 for further details. Hence, itis normally not possible to perform ECA of pipelines with nom-inal wall thickness less than about 10 mm. If fracture toughness testing is not possible and the εl,nom exceeds0.4%, full scale testing or pipe segment testing shall be per-formed to prove the integrity of the girth welds including worstcase weld defects. The testing shall reflect the worst case loadingcondition, relevant temperature, unfavourable material proper-ties and unfavourable girth weld geometry.

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Offshore Standard DNV-OS-F101, October 2007 App.A –

Figure 1 SENT geometry


B. Assessment Categories

B 100 General101 Pipeline systems shall have adequate resistance againstfailure during the whole of its design life. This shall beachieved by selecting materials and welds with adequate frac-ture toughness, tensile properties and weld defect acceptancecriteria. 102 The various assessment procedures provided in thisAppendix are based on BS 7910. Hence the recommendationsand requirements are only applicable if BS 7910 is the basis forthe assessment with amendments and adjustments as describedin this Appendix. It is acceptable to base the integrity of welds on finite element(FE) analyses or other suitable standards, but in such cases theassessment procedure must be thoroughly described and docu-mented. Such procedures shall be compared with the proce-dures described in this standard.103 The ECA procedures described in this standard gener-ally consider uni-axial loading conditions. However, the oper-ation of pipelines normally involves both internal pressure andaxial strain, i.e. a bi-axial stress-strain state. ECA of the oper-ational stage under biaxial stresses is described in E206 (lastpart).

Guidance note:Recent full-scale testing has indicated that the fracture capacityfor circumferentially aligned defects (such as those at girthwelds) subject to an applied longitudinal strain is reduced if thepipeline is pressurized. This phenomenon is mainly caused byincreased crack driving force. Assessment procedures consider-ing internal overpressure combined with longitudinal tensilestrains are under development, but are not implemented in thisstandard. Analysis for such situations must be well documented

and based on well proven engineering principles e.g. 3D FE frac-ture mechanics analysis.


104 The assessment temperature is defined as the tempera-ture representative for the stress-strain condition considered. Itmay be ambient (typically installation), elevated (e.g. lateralbuckling) or sub-zero (e.g. shut-down). All testing shall nor-mally be performed at the assessment temperature, see Subsec-tion G and 109. If other test temperatures are chosen it must be substantiatedthat the testing gives conservative results as compared to test-ing at the assessment temperature.105 Depending on the level of monotonic and cyclic defor-mations, the assessment procedure and required testing isdivided in categories as follows:

a) Maximum longitudinal strain, εl,nom, less than 0.4%. Max-imum number of strain cycles limited to 10, suffix ECAstatic - low. ECA static – low, may further be “generic” or“full”:

— generic ECA, see Subsection C, requires less testingand assessments are not required as maximum allow-able flaw sizes are extracted from tables. GenericECA is only applicable if specified requirements arefulfilled

— full ECA, see Subsection E, requires more testing andassessments. Full ECA is performed if generic ECA isnot acceptable because all requirements are not ful-filled or if larger maximum allowable flaw sizes arerequired.

b) Maximum longitudinal strain, εl,nom, equal to or largerthan 0.4%. Maximum number of strain cycles limited to10, suffix ECA static - high. ECA static – high, may fur-ther be “generic” (see Subsection D) or “full” (see Subsec-tion E) as specified above.

c) More than 10 strain cycles with Δσl,nom larger than200 MPa or more than 10 000 stress cycles suffix ECAfatigue, see Subsection F.

However, if A203 is fulfilled, no further assessments arerequired.106 A pipeline may either be defined according to “ECAstatic - low”, “ECA static – high”, “ECA fatigue” or as a com-bination of “static” and “fatigue”. All phases during manufac-turing, fabrication, installation and operation shall beevaluated and included in the assessment of maximum allow-able flaw sizes. If the size of weld defects indicates potentialfailures during installation or operation based on ECA, theallowable weld defect sizes shall be reduced. A typical ECAprocess is illustrated in Figure 2. The actual assessment proce-dures for girth welds are illustrated in Figure 3.

Figure 2 Illustration of a typical ECA process

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Figure 3 Flowchart of girth weld integrity assessment

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107 It shall be evaluated if the loading mode in considerationis displacement controlled or load controlled and the assess-ment methodology shall reflect this. Normally offshore sub-marine pipelines are displacement controlled duringinstallation (e.g. bending controlled by curvature.) and it isacceptable to follow the displacement controlled (strain-based)procedure which is presented in this standard. Where the pipeline is load-controlled (e.g. some operationalconditions or whilst in the lay catenary) the special considera-tions specified in 108 apply.108 If the loading mode is load controlled and it is natural tospecify the applied load as a tension stress, the assessmentmethodology specified in this Appendix can be used with thefollowing changes:

— if pre-straining is relevant (see Subsection G), the finalstrain cycle applied to the test specimen blanks shall endin compression. Tensile test results and fracture toughnessresults from this material shall be used in the assessment

— if pre-straining is not relevant, as-received material usedfor testing shall as far as possible have documented“lower-bound” tensile properties. For the assessmentseither a “lower-bound” stress-strain curve shall be con-structed or a tensile stress-strain curve shall be establishedfrom testing which shall represent “lower-bound” proper-ties

— Lr,max (Lr cut-off), see E208, shall be defined as:

where UTS is the engineering tensile strength and YS isthe engineering yield stress of the parent pipe.

109 The effect of plastic deformation, possible ageing andthe assessment temperature shall be taken into account whenfracture toughness testing and tensile testing is performed, seeSubsection G.110 The maximum defect size resulting from the ECA shallbe adjusted for the probability of detection, flaw sizing errorand potential flaw interaction relevant to the specific NDTequipment used for inspection see Appendix D and E (Note theprobability of detection and sizing error is normally specific tothe NDT method, pipe material, geometry and welding proce-dures)

C. Generic ECA for Girth Welds Subject to Strains Less than 0.4%

Assessed According to ECA Static – LowC 100 General101 If larger weld defect acceptance criteria than specified inAppendix D, are requested, the maximum allowable flawsspecified in Table A-2 to A-4, suitably adjusted to account forsizing accuracy, may be used for the final weld defect accept-ance criteria. This is only acceptable if all requirements speci-fied in A300 and 104 are fulfilled.102 The ECA does not provide acceptance criteria for UT/AUT. The intention of an ECA is to provide critical flaw

dimensions for given material properties and loading condi-tions in a conservative way. The derivation of flaw acceptancecriteria for UT/AUT can be based upon the critical flaw dimen-sions obtained from the ECA in accordance with the recom-mendations and limitations of Appendix D and Appendix E. 103 The generic ECA is performed based on Level 2Baccording to BS 7910 with amendments and adjustments asdescribed in this Appendix. It is recommended that the J frac-ture toughness parameter is established by testing of SENTspecimens. The specimens shall be tested to maximum loadand the J value shall be judged either as Jm, Jc or Ju accordingto BS 7448: Part 1 and Part 2. The characteristic fracturetoughness value shall be defined according to E211.104 If the ECA is performed for the operational phase con-sidering a combination of internal overpressure and longitudi-nal loading, the fracture toughness testing shall be performedon SENB specimens.105 This “generic ECA” is not applicable for the followingsituations:

— clad or lined pipelines (special advice must be sought)— where the girth welds have under-matching strength com-

pared to the parent pipe, see E108— if the girth welds are not tested according to Table A-1,

Subsection G and Appendix B— if the linepipes have not been tested and designed accord-

ing to Sec.6 and Sec.7— if experimentally determined values of J do not meet the

requirements specified in Table A-2 to Table A-4— the geometry, applied strain and misalignment is not

within the limitations specified in Table A-2 to Table A-4— if the stress-strain curve exhibit a Lüder plateau (yield dis-

continuity in the stress-strain curve) and the maximumlength of the plateau seen during production tensile testingand tensile testing according to Table A-1 exceeds 2%

— if significant pop-ins, see BS 7448: Part 2, or unstablefracture occur prior to maximum load during fracturetoughness testing

— if the material testing does not satisfy the requirementsspecified in Subsection G and Appendix B

— if the following YS/UTS ratios are not met during the pro-duction qualification tests for the line pipe according toTable A-1:YS/UTS ≤ 0.90 for C-Mn with SMYS ≤ 555 MPaYS/UTS ≤ 0.85 for 13Cr

— if the following Lr cut-off values determined from theSENT testing according to C208 are not met:Lr cut-off ≥ 1.20 for C-Mn with SMYS ≤ 450 MPaLr cut-off ≥ 1.15 for C-Mn with 450 < SMYS ≤ 485 MPaLr cut-off ≥ 1.10 for C-Mn with 485 < SMYS ≤ 555 MPaLr cut-off ≥ 1.20 for 13Cr.

106 If not all the requirements in 105 are fulfilled either a fullECA shall be performed or the acceptance criteria shall be inaccordance with Appendix D and Appendix E.107 Where the linepipe is subjected to fatigue during opera-tion or installation the maximum allowable flaw sizes deter-mined from Tables A2 to A4 should be adjusted to account forpossible fatigue crack growth in accordance with Subsection F.

YSUTSYSLr 2max,

+=

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Table A-1 Testing required for use of “generic ECA” for strain conditions less than 0.4% 1), 2)

Type of test Location Test quantityTransverse all weld tensile testing 4), 5) Transverse girth weld 3Tensile testing 4), 5) Parent pipe, longitudinal 3J testing of SENT specimens 5) 6) Main line 3 specimens for each notch position, see Appendix BJ testing of SENT specimens 5) 6) Double joint 3 specimens for each notch position, see Appendix BJ testing of SENT specimens 5) 6) Through thickness repair (TTR) 3 specimens for each notch position, see Appendix BJ testing of SENT specimens 5) 6) Partial repair 3) 3 specimens for each notch position, see Appendix B 1) All weld procedures which have different essential variables according to Appendix C, Table C-2 shall be tested2) The test temperatures and material condition to be tested shall be as specified in Subsection G3) If the welding procedure and heat input is equal to the through thickness repair procedure, this testing may be omitted4) If production tensile testing is performed at the assessment temperature and full stress-strain curves are established, additional tensile testing is not

required5) The specimen geometry and test requirements are specified in Appendix B6) The blunting shall be included in the tearing length

Table A-2 Characteristic J requirements for different maximum allowable flaw sizes 1) [N/mm = kJ/m2]Max allowable flaw,a × 2c [mm] 2)

Nominal outer diameter, 8” ≤ OD ≤ 12”, WT = nominal wall thicknessC-Mn; SMYS ≤ 450 C-Mn; SMYS = 485 C-Mn; SMYS = 555 13Cr

15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 253 × 50 440 310 480 340 530 460 250 2504 × 50 750 450 Full 500 Full 570 440 2505 × 50 Full 640 Full 700 Full 780 Full 3003 × 100 730 430 790 470 Full 680 480 2504 × 100 Full 720 Full 790 Full Full Full 4003 × 200 Full 650 Full 710 Full Full Full 4204 × 200 Full Full Full Full Full Full Full Fullδmax [mm], see E206 1.8 2.5 1.8 2.5 1.8 2.5 1.8 2.5a > 5 mm Full ECA required2c > 200 mm Full ECA requiredWT < 15 mm Full ECA requiredWT < 10 mm See A3081) Only acceptable if testing as specified in Table A-1 has been performed2) Maximum allowable flaw size, a × 2c refers to height and length respectively of both surface breaking and embedded flaws. If the embedded flaw is

located close to the surface (ligament height less than half the flaw height) the ligament height between the flaw and the surface shall be included in the flaw height. The UT/AUT flaw sizing error must be subtracted from the maximum allowable flaw height to establish the UT/AUT weld defect acceptance criteria, see Appendix D and Appendix E

WT = nominal wall thickness


Nominal outer diameter, 12” < OD ≤ 16”, WT = nominal wall thicknessC-Mn; SMYS ≤ 450 C-Mn; SMYS = 485 C-Mn; SMYS = 555 13Cr

15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 253 × 50 370 250 400 250 460 250 250 2504 × 50 600 410 660 440 740 500 310 2505 × 50 Full 540 Full 590 Full 670 550 2503 × 100 560 350 610 390 680 440 310 2504 × 100 Full 570 Full 620 Full 690 740 2703 × 200 Full 510 Full 550 Full 610 Full 2704 × 200 Full Full Full Full Full Full Full 580δmax [mm], see E206 1.8 2.5 1.8 2.5 1.8 2.5 1.8 2.5a > 5 mm Full ECA required2c > 200 mm Full ECA requiredWT < 15 mm Full ECA requiredWT ≤ 10 mm See A3081) Only acceptable if testing as specified in Table A-1 has been performed2) Maximum allowable flaw size, a × 2c refers to height and length respectively of both surface breaking and embedded flaws. If the embedded flaw is



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D. Generic ECA for Girth Welds Subjected to Strains Equal to or Larger than

0.4% but Less Than 2.25% Assessed According to ECA Static – High

D 100 General101 The maximum allowable flaws specified in Table A-6 to A-9, suitably adjusted to account for sizing accuracy, may be usedfor the final weld defect acceptance criteria. This is only accepta-ble if all requirements specified in A300 and 103 are fulfilled.102 The generic ECA is based on Level 3B (fracture resist-ance curve needed) according to BS 7910 with amendmentsand adjustments as described in this Appendix. The ductiletearing including blunting, Δa, shall be measured for all theSENT tests. For each set (3 specimens) one test shall be testedbeyond maximum load (notch opening displacement (V) atmaximum load multiplied by 1.1), one test shall be tested tomaximum load and one test shall be unloaded before maxi-mum load.103 This generic ECA is not applicable for the following sit-uations:

— clad or lined pipelines (special advice must be sought)— pipelines subjected to a combination of internal overpres-

sure and εl,nom> 0.4%, see E206 (last part) — where the girth welds have under-matching strength com-

pared to the parent pipe, see E108— if more than 5 tensile strain cycles are applied (e.g. one

contingency operation during reeling installation isacceptable)

— if the girth welds are not tested in accordance with TableA-5, Subsection G and Appendix B

— if the linepipes have not been tested and designed accord-ing to Sec.6 and Sec.7

— if the difference in yield stress between adjacent linepipes

exceeds 100 MPa— if experimentally determined values of J do not meet the

requirements specified in Table A-6 to Table A-9 (see Figure 4)— if significant pop-ins, see BS 7448: Part 1 and 4, or unsta-

ble fracture occur prior to maximum load during fracturetoughness testing

— if geometry, applied strain, fracture toughness and maxi-mum misalignment are not within the limitations specifiedin Table A-6 to Table A-9

— if the following YS/UTS ratios are not met during the pro-duction qualification tests or the parent pipe tensile testingspecified in Table A-5:YS/UTS ≤ 0.90 for C-Mn with SMYS ≤ 450 MPaYS/UTS ≤ 0.90 for C-Mn with 450 < SMYS ≤ 485 MPaYS/UTS ≤ 0.90for C-Mn with 485 < SMYS ≤ 555 MPaYS/UTS ≤ 0. 85 for 13Cr

— if the following Lr cut-off values determined from theSENT testing according to E208 are not met:Lr cut-off ≥ 1.20 for C-Mn with SMYS ≤ 450 MPaLr cut-off ≥ 1.15 for C-Mn with 450 < SMYS ≤ 485 MPaLr cut-off ≥ 1.10 for C-Mn with 485 < SMYS ≤ 555 MPaLr cut-off ≥ 1.20 for 13Cr.

104 If any of the requirements specified in 103 are not met,a full ECA shall be performed according to Subsections E.105 Where the linepipe is subject fatigue during operation orinstallation the maximum allowable flaw sizes determinedfrom Tables A6 to A9 should be adjusted to account for possi-ble fatigue crack growth in accordance with Subsection F.106 If ECA is performed for the operational phase based ongeneric ECA for the installation phase, the crack height shallbe increased by 0.5 mm if 0.4% < εl,nom ≤ 1.0% during instal-lation. If εl,nom exceeded 1% during installation the crackheight shall be increased by 1.0 mm.


Nominal outer diameter, OD > 16”, WT = nominal wall thicknessC-Mn; SMYS ≤ 450 C-Mn; SMYS = 485 C-Mn; SMYS = 555 13Cr

15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 253 × 50 350 250 380 250 430 250 250 2504 × 50 540 280 590 370 670 370 260 2505 × 50 Full 510 Full 550 Full 630 450 2503 × 100 490 330 540 360 600 410 250 2504 × 100 Full 510 Full 560 Full 630 580 2503 × 200 800 440 Full 490 Full 540 Full 2504 × 200 Full 770 Full Full Full Full Full 440δmax [mm], see E206 1.0 1.5 1.0 1.5 1.0 1.5 1.0 1.5a > 5 mm Full ECA required2c > 200 mm Full ECA requiredWT < 15 mm Full ECA requiredWT ≤ 10 mm See A3081) Only acceptable if testing as specified in Table A-1 has been performed2) Maximum allowable flaw size, a × 2c refers to height and length respectively of both surface breaking and embedded flaws. If the embedded flaw is



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Figure 4 No J Δa test results shall end-up inside the area indicated

Table A-5 Testing required for use of “generic ECA” for strain conditions equal to or larger than 0.4% 1), 2)

Type of test Location Test quantityTransverse all weld tensile testing 4), 5) Transverse girth weld 3Tensile testing 4), 5) Parent pipe, longitudinal 5J R testing of SENT specimens 5), 6) Main line 3 specimens for each notch position, see Appendix B J R testing of SENT specimens 5), 6) Double joint 3 specimens for each notch position, see Appendix B J R testing of SENT specimens 5), 6) Through thickness repair (TTR) 3 specimens for each notch position, see Appendix B J R testing of SENT specimens 5), 6) Partial repair 3) 3 specimens for each notch position, see Appendix B 1) All weld procedures which have different essential variables according to Appendix C, Table C-2 shall be tested2) The test temperatures and material condition to be tested shall be as specified in Subsection G3) If the welding procedure and heat input is equal to the through thickness repair procedure, this testing may be omitted4) If production tensile testing is performed at the assessment temperature and full stress-strain curves are established, additional tensile testing is not required5) The specimen geometry and test requirements are specified in Appendix B6) The blunting shall be included in the tearing length

Table A-6 Maximum allowable flaw sizes, a × 2c [mm], maximum strain, 0.4% ≤ εl,nom < 1% 1), 2)

J[N/mm = kJ/m2]

Nominal outer diameter, 8” ≤ OD ≤ 12”, WT = nominal wall thicknessC-Mn; SMYS ≤ 450 C-Mn; SMYS = 485 C-Mn; SMYS = 555 13Cr; SMYS = 550

15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25J0.5 = 400 3 × 25 3 × 55 3 × 25 3 × 40 3 × 20 3 × 30 3 × 30 3 × 60and 4 × 20 4 × 25 4 × 15 4 × 25 4 × 15 4 × 20 4 × 20 4 × 35J1.0 = 600 5 × 15 5 × 20 5 × 15 5 × 20 5 × 10 5 × 15 5 × 15 4 × 25J0.5 = 600 3 × 50 3 × 100 3 × 45 3 × 90 3 × 35 3 × 80 3 × 45 3 × 95and 4 × 30 4 × 50 4 × 25 4 × 45 4 × 20 4 × 40 4 × 25 4 × 55J1.0 = 800 5 × 20 5 × 35 5 × 20 5 × 30 5 × 15 5 × 25 5 × 20 5 × 40J0.5 = 800 3 × 70 3 × 150 3 × 65 3 × 145 3 × 55 3 × 115 3 × 50 3 × 100and 4 × 40 4 × 80 4 × 35 4 × 70 4 × 30 4 × 60 4 × 30 4 × 70J1.0 = 1000 5 × 25 5 × 50 5 × 25 5 × 45 5 × 20 5 × 40 5 × 25 5 × 50δmax [mm], see E206

1.8 2.5 1.8 2.5 1.8 2.5 1.8 2.5

2c ≥ 100 mm Full ECA requiredWT < 15 mm Full ECA requiredWT ≤ 10 mm See A3081) Only acceptable if testing as specified in Table A-5 has been performed2) Maximum allowable flaw size, a × 2c refers to height and length respectively of both surface breaking and embedded flaws. If the embedded flaw is



DET NORSKE VERITAS



J[N/mm = kJ/m2]

Nominal outer diameter, 12” < OD ≤ 16”, WT = nominal wall thickness

C-Mn; SMYS ≤ 450 C-Mn; SMYS = 485 C-Mn; SMYS = 555 13Cr; SMYS = 55015 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25

J0.5 = 400 3 × 35 3 × 75 3 × 30 3 × 55 3 × 25 3 × 40 3 × 40 3 × 90and 4 × 20 4 × 30 4 × 20 4 × 30 4 × 15 4 × 25 4 × 25 4 × 45J1.0 = 600 5 × 15 5 × 25 5 × 15 5 × 20 5 × 15 5 × 20 5 × 20 5 × 30J0.5 = 600 3 × 65 3 × 150 3 × 60 3 × 135 3 × 50 3 × 115 3 × 65 3 × 145and 4 × 35 4 × 75 4 × 30 4 × 65 4 × 25 4 × 50 4 × 35 4 × 80J1.0 = 800 5 × 25 5 × 45 5 × 20 5 × 40 5 × 20 5 × 30 5 × 25 5 × 50J0.5 = 800 3 × 95 3 × 150 3 × 85 3 × 150 3 × 80 3 × 150 3 × 75 3 × 150and 4 × 50 4 × 115 4 × 45 4 × 100 4 × 40 4 × 85 4 × 45 4 × 105J1.0 = 1000 5 × 35 5 × 70 5 × 30 5 × 60 5 × 25 5 × 50 5 × 30 5 × 70δmax [mm], see E206

1.8 2.5 1.8 2.5 1.8 2.5 1.8 2.5





J[N/mm = kJ/m2]

Nominal outer diameter, OD > 16”, WT = nominal wall thicknessC-Mn; SMYS ≤ 450 C-Mn; SMYS = 485 C-Mn; SMYS = 555 13Cr; SMYS = 550

15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25J0.5 = 400 3 × 40 3 × 90 3 × 30 3 × 70 3 × 25 3 × 50 3 × 50 3 × 125and 4 × 20 4 × 35 4 × 20 4 × 35 4 × 15 4 × 30 4 × 30 4 × 60J1.0 = 600 5 × 15 5 × 25 5 × 15 5 × 25 5 × 15 5 × 25 5 × 20 5 × 40J0.5 = 600 3 × 80 3 × 150 3 × 70 3 × 150 3 × 60 3 × 140 3 × 85 3 × 150and 4 × 40 4 × 90 4 × 35 4 × 75 4 × 30 4 × 60 4 × 45 4 × 105J1.0 = 800 5 × 25 5 × 50 5 × 25 5 × 45 5 × 20 5 × 35 5 × 20 5 × 65J0.5 = 800 3 × 120 3 × 150 3 × 105 3 × 150 3 × 95 3 × 150 3 × 100 3 × 150and 4 × 60 4 × 145 4 × 50 4 × 125 4 × 45 4 × 105 4 × 60 4 × 145J1.0 = 1000 5 × 35 5 × 80 5 × 35 5 × 70 5 × 30 5 × 60 5 × 40 5 × 90δmax [mm], see E206

1.5 2.0 1.5 2.0 1.5 2.0 1.5 2.0




DET NORSKE VERITAS


E. Girth Welds under Strain-based Loading Assessed According to ECA Static - Full

E 100 General101 For load-controlled conditions, this procedure may befollowed provided B108 is followed. 102 If the generic ECA is not applicable a full ECA staticshall be performed. If the maximum allowable flaw sizesassessed by ECA generic are not as required/desirable a fullECA shall be performed which may improve the results.103 The ECA does not provide acceptance criteria for UT/AUT. For determination of acceptance criteria, see AppendixD and Appendix E.104 The linepipes shall be tested and designed according toSec.6 and Sec.7 and the girth welds shall be tested accordingto Table A-10, Subsection G and Appendix B.

105 The ECA static – full procedure is only acceptable iflimitations specified in A300 applies.106 Full ECA requires more testing than the generic ECA,see Table A-1 and Table A-5. Tests already performed for ageneric ECA may be used when constructing the J R-curvesrequired for the full ECA.107 The crack growth including blunting (total a minus a0)shall be measured for all the SENT tests. A minimum of 6SENT specimens are normally required to construct a J R-curve for each weld procedure considered. It is suggested thatone specimen is tested beyond maximum load (notch openingdisplacement (V) at maximum load multiplied by 1.1), that twospecimens are tested to maximum load and that the remaining3 specimens are unloaded prior to maximum load at differentV values.

Table A-9 Maximum allowable flaw sizes, a × 2c [mm], maximum strain, 1.0% < εl,nom < 2.25% 1), 2)

J[N/mm = kJ/m2]

Nominal outer diameter, 8” ≤ OD ≤ 16”, WT = nominal wall thicknessC-Mn; SMYS ≤ 450 C-Mn; SMYS = 485 C-Mn; SMYS = 555 13Cr; SMYS = 550

15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25 15 ≤ WT < 25 WT ≥ 25J0.5 = 400 3 × 20 3 × 35 3 × 20 3 × 30 3 × 15 3 × 25 3 × 15 3 × 25and 4 × 15 4 × 20 4 × 15 4 × 20 4 × 10 4 × 15 4 × 10 4 × 20J1.0 = 600 5 × 10 5 × 15 5 × 10 5 × 15 4 × 10 5 × 10 5 × 15J0.5 = 600 3 × 35 3 × 85 3 × 35 3 × 75 3 × 30 3 × 60 3 × 30 3 × 60and 4 × 20 4 × 40 4 × 20 4 × 35 4 × 20 4 × 30 4 × 20 4 × 30J1.0 = 800 5 × 15 5 × 30 5 × 15 5 × 25 5 × 15 5 × 20 5 × 15 5 × 25J0.5 = 800 3 × 45 3 × 95 3 × 45 3 × 95 3 × 45 3 × 95 3 × 35 3 × 75and 4 × 30 4 × 65 4 × 30 4 × 60 4 × 25 4 × 50 4 × 25 4 × 50J1.0 = 1000 5 × 20 5 × 40 5 × 20 5 × 40 5 × 20 5 × 30 5 × 15 5 × 30δmax [mm], see E206

1.5 2.0 1.5 2.0 1.5 2.0 1.5 2.0

2c ≥ 100 mm Full ECA requiredWT < 15 mm Full ECA requiredWT ≤ 10 mm See A3081) Only acceptable if testing as specified in Table A-5 has been performed2) Maximum allowable flaw size, a × 2c refers to height and length respectively of both surface breaking and embedded flaws. If the embedded flaw is located

close to the surface (ligament height less than half the flaw height) the ligament height between the flaw and the surface shall be included in the flaw height. The UT/AUT flaw sizing error must be subtracted from the maximum allowable flaw height to establish the UT/AUT weld defect acceptance criteria, see Appendix D and Appendix E


Table A-10 Testing required for girth welds in pipelines with category ECA static – Full ECA1), 2)

Type of test Location Test quantityTransverse all weld tensile testing 4), 5) Girth weld 3Tensile testing 4), 5) Parent pipe, longitudinal 5J-R testing of SENT specimens 5), 6) Main line One J R-curve (minimum 6 SENT) for each notch posi-

tion, see Appendix B J-R testing of SENT specimens 5), 6) Double joint One J R-curve (minimum 6 SENT) for each notch posi-

tion, see Appendix B J-R testing of SENT specimens 5), 6) Through thickness repair (TTR) One J R-curve (minimum 6 SENT) for each notch posi-

tion, see Appendix BJ-R testing of SENT specimens 5), 6) Partial repair 3) One J R-curve (minimum 6 SENT) for each notch posi-

tion, see Appendix B1) All weld procedures which have different essential variables according to Appendix C, Table C-2 shall be tested2) The test temperatures and material condition to be tested shall be as specified in Subsection G3) If the welding procedure and heat input is equal to the through thickness repair procedure, this testing may be omitted4) If production tensile testing is performed at the assessment temperature and full stress-strain curves are established, additional tensile testing is not required5) The specimen geometry and test requirements are specified in Appendix B6) The blunting shall be included in the tearing length

DET NORSKE VERITAS


108 The parent pipe tensile properties and the weld metaltensile properties shall be assumed to be even-matching in theassessment, i.e. the stress-strain curve of the parent pipe mate-rial shall be used. Because of the assumption of even-match-ing, it is assumed that the primary stresses are equal for defectslocated at the Fusion Line (FL) border and for defects locatedwithin the weld metal, see A307.If weld metal strength overmatch is not obtained for all mate-rial conditions, the procedure for determination of appliedstresses specified in E206 is not acceptable and special advicemust be sought. Girth welds with less thickness than the parentpipe wall thickness is not acceptable (counter-boring is notacceptable).A strength overmatching weld is obtained if the tensile stress-strain curves for the weld metal are higher than the tensilestress-strain curve of the parent pipe for all material conditionsand strain levels under consideration.109 Weld residual stresses shall in general be assumed to beuniform and equal to the yield stress of the parent pipe. Relax-ation according to BS 7910 is acceptable. If the weld residualstress distribution is documented by sufficient simulations, it isacceptable to define the stress distribution more accurately.110 Where the linepipe is subjected to fatigue loading duringinstallation or operation the maximum allowable flaw sizesdetermined from the ECA shall be adjusted to account for pos-sible fatigue crack growth in accordance with Subsection F.

E 200 Assessment methodology201 Strain based assessments with εl,nom exceeding 0.4%during installation shall be carried out in accordance with BS7910 at assessment Level 3B with amendments and adjust-ments as described in this Appendix. However, for assessmentof critical flaw size at the end of design life with εl,nom equalto or less than 1% Level 2B in accordance with this Appendixis acceptable. Both assessments based on the Level 2B and 3Bprocedures require that material specific stress-strain curvesare established. Fracture resistance curves (J R- or CTOD R-curve) is further required for assessments according to Level3B while single parameter fracture toughness is required forLevel 2B (CTOD or J).It is recommended that the fracture resistance curves are pre-sented as J R-curves established from SENT testing accordingto DNV-RP-F108, and Appendix B (see also Subsection G forfurther details). This is to ensure that a possible weld defectwill not lead to failure due to ductile tearing. Further, anassessment at Level 3B for the installation phase providesinformation about the defect size after installation which isneeded for assessing possible fatigue crack growth and frac-ture during operation.However, for the operational phase considering a combinationof internal overpressure and longitudinal loading the fracturetoughness testing shall be performed by testing of SENB spec-imens, see also last part of 206. 202 Assessment procedures, other than specified in thisAppendix may be acceptable, but must be justified, welldescribed, documented and accepted by all parties.203 If an ECA is performed, the following requirements andrecommendations are applicable:

— The nominal wall thickness minus the manufacturing tol-erance of the pipe shall be used in assessments consideringinstallation.If ECA is performed for only a limited amount of girthwelds it is acceptable to determine the wall thickness to beused in the ECA using probabilistic methods.

— A suitable corrosion allowance shall be included in theassessments during the operational life of the pipeline. Atthe end of design life the whole corrosion allowance shallbe subtracted.In case of fitness-for-purpose evaluations it is acceptableto base the thickness on inspected values.

— The assessments shall be thoroughly defined and pre-sented such that the assessment results are reproducible bya 3rd. party.

— The sensitivity of different input parameters and the con-servatism of the results should be evaluated and discussed.

204 Required inputs for an assessment according to a fullECA as specified in this Appendix:

— pipe dimensions, weld dimensions and dimensional toler-ances (e.g. high lows acceptable for manufacture)

— tensile properties in the form of complete engineeringstress-strain curves for the parent pipe material and evi-dence that the weld metal stress-strain curve over-matchesthe parent pipe in the region of interest, see E108

— fracture toughness data for specimens with notcheslocated both within the weld metal and at or near the fusionboundary as specified in this Appendix and Appendix B

— the Lr cut-off value (see E208)— maximum acceptable tearing (stable crack extension/

growth) (see E209)— applied strain history during the installation phase and sec-

ondary stresses (e.g. residual stresses from the welding orinstallation processes)

— applied maximum design stress (tensile) applicable to theoperational life

— cyclic stress history applicable to the pipeline whilst it isin the lay catenary configuration and during the opera-tional life.

205 Determination of tensile properties and stress-straincurve shall be performed as follows:

— tensile testing performed during production or qualifica-tion shall be issued to the ECA contractor and the resultsshall be considered when the material specific stress-straincurve is constructed

— the tensile properties used in the ECA shall describe anupper-bound stress-strain curve with low strain hardening

— assumptions of local displacement control involvingrelaxation of the stress level due to crack growth are notacceptable

— for load controlled conditions see 101 and B108.

206 Determination of the applied stresses shall follow thefollowing procedure:

— For uniaxial loading the nominal stress shall be deter-mined from the nominal strain from the actual engineering“upper-bound” stress-strain curve. This stress is defined asthe primary membrane stress, Pm, according to BS 7910.For operational cases considering combined internal over-pressure and longitudinal strain see the instructions at theend of this paragraph.

— The nominal stress shall be increased because of anassumed stress concentration factor (SCF) due to mis-alignment at the girth weld. The Neuber approach may beapplied. The stress magnification is defined as a primarybending stress, Pb, according to BS 7910.

DET NORSKE VERITAS


The SCF used in the ECA calculation may be calculatedaccording to DNV-RP-C203:

where

and:

It is acceptable to calculate the SCF with the following as-sumptions, see Figure 5:

The hi/lo shall in general be less than 0.15tnom and maxi-mum 3 mm, see Appendix D, Table D-3. However, weldcontractors often specify a maximum value of hi/loROOTwhich is smaller than the allowable hi/lo. This is accepta-ble but must be documented. Note that hi/loROOT may beless than the misalignment.

Figure 5 Illustration of how the maximum SCF may be assumed

The Neuber method was originally developed to assessstrains at notches. It has been extensively used for pipelinegirth welds subjected to plastic strains with good experi-ence and has been adopted for use in this Appendix.The Neuber method is defined by the following equation:

where

An illustration of the Neuber rule is shown in Figure 6.

Figure 6 Illustration of the Neuber rule

— Normally, the local stress intensity magnification factorMk is applied to welded connections. This increases thestress intensity factor to account for the presence of theweld toe. It is normally acceptable to exclude the Mk fac-tor for pipeline girth welds if εl,nom is exceeding 0.4% pro-

vided the applied stress is defined according to theprocedure specified above.If actual surface breaking defects with a height less than10% of the wall thickness must be expected, the criticalityof surface breaking flaws shall be assessed and an appro-priate Mk shall be applied.

— If the difference in yield stress between adjacent pipesexceeds 100 MPa, see Sec.7, I303, or the wall thickness

T and t = Wall thickness of the pipes on each side of the girth weld, T > t

δ = Eccentricities (wall thickness differ-ences, out-of-roundness, centre eccentricities etc.)

L = Length of weld capD = Outside diameter of pipe

δ =

αδ −⋅

⎟⎟⎟

⎠

⎞

⎜⎜⎜

⎝

⎛

⎟⎟⎠

⎞⎜⎜⎝

⎛+

⋅⋅

+= e

tTt

SCF5.2

1

161

⎟⎟⎠

⎞⎜⎜⎝

⎛⎟⎠⎞

⎜⎝⎛+

⋅=5.2

1

182.1

tTDt

Lα

2// CAPROOT lohilohi + SCF = elastic stress concentration factor

σ1 = nominal stress (excluding SCF)ε1 = nominal strain (excluding SCF)σ2 = actual stress (including SCF)ε2 = actual strain (including SCF)

21122 SCF×⋅=⋅ εσεσ

DET NORSKE VERITAS


tolerances specified in Sec.7, Table 7-17 to Table 7-19, arenot fulfilled, non-linear FE analyses shall be performed,either to determine correct applied stresses or to perform aLevel 3C (3D FE fracture mechanics) assessment.

— The relation between strains, concentrations, residualstresses and applied stresses is complex. Hence, theapplied stress in the ECA may alternatively be calculatedby non-linear FE analysis (without a crack) consideringthe nominal design strain, relevant geometry and materialproperties. The stress distribution across the girth weld isdefined as accurately as possible using the combination ofPm and Pb, see BS 7910. In such cases, identical materialtensile properties shall be applied to the FE analyses andto the ECA’s.

— For lined and clad pipelines, the applied stresses shall bedefined based on such FE analysis. Alternatively a Level 3assessment may be performed or other well documentedprocedures agreed by all parties.

— Weld residual stresses shall be assumed for girth welds inthe as-welded condition. Normally the weld residual stressshall be defined as a uniform secondary membrane stress,Qm, equal to the lowest yield stress of the weld metal andthe parent pipe material. In case of PWHT or high appliedstrain it is acceptable to reduce the weld residual stressaccording to BS 7910.

Recent research has shown that the combination of internalover-pressure and longitudinal loading may be more onerousthan longitudinal loading alone. However, there is currently novalidated and generally accepted procedure for assessing thecombined loading and each case shall be evaluated separatelyand the procedure accepted by all parties.The research results indicate that the reduction in strain capac-ity is caused by and increase in the crack driving force (appliedJ or applied CTOD) but that the material fracture toughness isnot influenced. This means that if the crack driving force isdetermined from dedicated 3D FEA or well documented andvalidated research results it is acceptable to use SENT testingto determine the fracture resistance also for the combination ofinternal over-pressure and longitudinal loading.For assessments of situations with longitudinal strains, εl,nom,equal to or less than 0.4% under internal over-pressure is itacceptable to apply the procedure specified above to determineapplied stresses. However, in such cases fracture toughnesstesting shall be performed on SENB specimens to compensatefor the under-estimated crack driving force.207 Determination of the reference stress, σref:It is recommended that the Kastner, see BS 7910 (P.12), solu-tion is used to determine the reference stress (σref) for theassessment of surface flaws. For the assessment of embedded flaws, BS 7910 uses a refer-ence stress solution developed for a flat plate. This is howeverconsidered to be too conservative where the critical defectheight of the embedded flaw may be predicted to be less thanthat of a surface breaking flaw of a corresponding length. Nor-mal practice is to assess the critical flaw height of a surfacebreaking flaw and to regard the results as valid for embeddedflaws of the same length, i.e. the height 2a of an embeddedflaw is equal to the height a of the equivalent surface breakingflaw.If the embedded flaw is located close to the surface (ligamentheight less than half the flaw height) the ligament heightbetween the flaw and the surface shall be included in the flawheight.The use of other, less conservative, reference stress solutions,whether for embedded or surface defects, must be justified anddocumented. 208 The Failure Assessment Diagram (FAD) cannot beextended to arbitrarily large plastic deformations and a cut-off

limit (referred as Lr cut-off or Lr,max) for the Lr (Lr = σref/YS)axis must be defined.In cases with large plastic strain, the maximum allowable flawsizes are often strongly dependant on the Lr cut-off value.Hence, this value should be chosen carefully.It is recommended that the Lr cut-off is calculated directlyfrom the SENT tests for the correct material condition.The Lr cut-off value, corresponding to the recorded maximumloads and the net-section area is as follows:

where

Alternatively, if SENT test data is not available, it is acceptablefor strain-based assessment to define the Lr cut-off value asUTS/YS, where UTS is the engineering tensile stress and YSis the yield stress of the parent pipe for the correct materialcondition, see Subsection G.209 The J R-curves (or CTOD R-curves) to be used in aLevel 3B assessment according to this Appendix shall be alower bound to all J-Δa test data. It is not acceptable for exper-imentally derived J-Δa points to be lower than the J R-curveapplied in the assessment.210 The maximum tearing permitted during the whole instal-lation process should not exceed 1 mm. However, the tearingmust not exceed the maximum tearing measured in the SENTspecimens.211 If a Level 2B assessment is performed (no fracturetoughness resistance curve), the critical J (or CTOD) shall bechosen according to BS 7910, Annex K, K.2.3.2:

All test results shall represent one homogeneous group (iden-tical microstructure and testing conditions etc.) and therequirements of BS 7910 Annex K.2.3 shall be satisfied. Theequivalent fracture toughness values are valid for both SENBand SENT testing.

F. Girth Welds Assessed According to ECA Fatigue

F 100 General101 If A203 is fulfilled, no further assessments are required.102 If allowable defect sizes are determined by ECA inaccordance with Subsections C, D or E, or for any other reasonare larger than specified in Appendix D, the fatigue life assess-ment shall be based on S-N curves validated for the allowabledefect sizes (see Sec.5 D808) or assessed based on fracturemechanics in accordance with this Subsection. As crack initiation is not included in the fracture mechanicsapproach, shorter fatigue lives are normally derived from frac-ture mechanics than by S-N data. However, a well defined andvalidated procedure for including a possible initiation period in

Pmax = minimum value of the maximum load from the SENT test programme

B, W and a0 = dimensions associated with the relevant SENT specimen (see Figure 1). a0 is the original crack height

Number of fracture toughness results

Equivalent fracture toughness value

3 to 5 Lowest6 to 10 Second lowest11 to 15 Third lowest

)( 0

maxmax. aWBYS

PLr −⋅=

DET NORSKE VERITAS


the fracture mechanics fatigue approach does currently notexist, see also 204.103 Possible stable crack growth (ductile tearing) andfatigue crack growth shall be considered in the assessment.The assessment shall confirm that the largest weld defectsexpected to remain after NDT and repair will not increase dur-ing pipe laying to an extent such that fracture or fatigue failurewill occur during operation of the pipeline.104 The critical flaw size shall be determined according toSubsection D and E as relevant and considered when thefatigue life is determined. The fatigue assessment shall be per-formed using the relevant fatigue loading and fatigue crackgrowth law to determine the fatigue life from the initial defectsize and until the critical defect size is reached.If satisfactory fatigue life can not be demonstrated or there is arisk of unstable fracture before or at the end of the operationallife, either the weld defect acceptance criteria shall be reducedor actions to reduce the fatigue loading shall be taken. Wherefatigue crack growth is predicted to be less than 0.2 mm, it canbe assumed to be negligible.105 The fatigue assessment shall consider all loading rele-vant to the design case, e.g. vortex induced vibration (VIV),bending stresses due to spanning, and varying longitudinalstresses due to thermal expansion and contraction. Due to possible residual stresses from welding or plastic defor-mation during installation or operation the compressive part ofcyclic stresses may contribute to the fatigue crack growth andthe whole stress range shall be considered in the assessment.106 It is acceptable to define the fatigue stress distributionthrough the wall thickness based on FE analyses provided thatthe analyses are well documented.107 The thickness of the pipe wall shall be defined accordingto E203, first and second bullet points. In case of life extensionassessments the wall thickness of the pipe shall be reduced bythe full corrosion allowance. If reliable wall thickness meas-urements are available it is acceptable to base the assessmenton such measurements.108 For lined or clad pipelines, the fatigue life shall beassumed equal to the time necessary to grow through the clad/liner thickness. Possible initial weld defects shall be assumedas relevant.109 If the NDT probability of detection (PoD) and sizingerror is in accordance with Appendix D and E it is acceptableto increase the fatigue damage ratio for the fracture mechanicsbased fatigue assessment in accordance with this Subsection todouble that of an S-N based fatigue assessment as described inSec.5 D810.

F 200 High-cycle fatigue201 Fracture mechanics based fatigue assessments in thehigh-cycle regime shall be based on BS 7910 or equivalentprocedures.

Guidance note:High-cycle loading is normally understood to be cycles of morethan around 1000 and stress ranges in the elastic regime.


202 Mean plus two standard deviation fatigue crack growthcurves representing the relevant environment shall be used.

For embedded defects it is acceptable to use air data until thecrack extends through the ligament and becomes a surfacecrack when the relevant environmental data shall be used.Residual stresses shall be included by applying the fatiguecrack growth curves for R≥0.5.203 Fatigue crack growth from possible flaws at the weldcap toe shall include an allowance for the increase in stressintensity factor due to the weld cap geometry as well as anylocal increase of bending due to girth weld misalignment. For the weld cap stress concentration it is acceptable toincrease the stress intensity factor by the Mk factor accordingto BS 7910 or to use other well documented relevant stressintensity factor solutions.

Guidance note:Large surface breaking defects normally do not occur in modernhigh quality pipeline girth welds. If it can be substantiated thatsurface breaking defects are not present it is acceptable to assumethe defects to be embedded with ligament height of 3 mm in thefracture mechanics based fatigue assessment. If the actual defect location can be determined it is acceptable tobase the integrity assessment on the actual location.


204 If the NDT probability of detection (PoD) and sizingerror is in accordance with Appendix D and E it is acceptableto increase the fatigue damage ratio for the fracture mechanicsbased fatigue assessment in accordance with this Subsection todouble that of an S-N based fatigue assessment as described inSec.5 D810.

F 300 Low-cycle fatigue301 Possible low-cycle fatigue shall be assessed. However,there does currently not exist any well defined, validated andgenerally accepted procedure for the assessment of low-cyclefatigue in pipeline girth welds.Any method used for assessing low-cycle fatigue shall there-fore be justified, well documented and agreed by all parties.

Guidance note:Low-cycle loading is normally understood to be cycles less thanaround 1000 and stress/strain ranges in the elastic-plastic regime.


G. Testing Requirements

G 100 General101 Fracture toughness testing shall be performed on thematerials and material conditions specified in Table A-11. 102 Tensile testing shall be performed on the materials andthe material conditions specified in Table A-12.103 Mechanical testing, fracture mechanics testing and pre-straining shall be performed according to this Subsection andAppendix B.104 The extent of fracture mechanics testing and tensile test-ing for the different ECA categories shall be as specified inTable A-1, Table A-5 and Table A-10 respectively. All notchpositions specified in Appendix B shall normally be tested andexceptions must be thoroughly evaluated and documented.

DET NORSKE VERITAS


Guidance note:The tensile properties and the shape of the stress-strain curve areimportant and have a strong effect on the critical flaw dimen-sions. Experience shows that for strain based assessments thetensile properties are sensitive to test temperature and pre-strain-ing and ageing history. Conservative values of the critical flawdimensions are determined using higher yield strengths and lowstrain hardening.


105 For pipeline materials susceptible to environmentallyinduced embrittlement the mechanical, fracture toughness andfatigue properties shall reflect the actual environment, see alsoA306. If tensile testing, fracture toughness testing and crackgrowth testing is performed under representative environmen-tal and loading condition, the assessment procedure describedin Subsection E and F are applicable.106 The corresponding CTOD fracture toughness can con-servatively be estimated from the J fracture toughness accord-ing to the following formulas:

where

This is a conservative way of calculating CTOD from J and,hence, it is not acceptable to use the formulas the other wayaround to calculate the J fracture toughness to be used in Sub-section C and D.

G 200 Straining and ageing201 For strain-based ECAs, upper-bound tensile propertieswith low strain hardening shall be assessed and tested. Forstress-based ECAs, lower-bound tensile properties shall beassessed and tested. To achieve this it may be necessary to pre-strain and age the material prior to testing. Pre-straining andageing is normally not required for ECA Static consideringinstallation, see also 204.If aging is relevant, artificial ageing at 250°C for one hour shallbe performed prior to any tensile testing. The ageing shall beperformed after the pre-straining but before the tests are per-formed.202 There are three important material mechanisms thatmust be considered when the pre-straining and aging proce-dure is established. These are:

Table A-11 Required material condition and test temperature fracture toughness testingECA Category Material condition to be

testedTest temperatures

A B CECA Static - low, εl,nom < 0.4% during both installation and operation As-received Tmin RT TmaxECA Static - high, εl,nom ≥ 0.4% during installation1) As-received Tmin RT TmaxECA Static – high, εl,nom ≥ 0.4% during operation Pre-strained and aged 2) Tmin RT TmaxAssessment temperatures in consideration:

A Minimum temperature, Tmin < 0oCB Minimum temperature, 0oC ≤ Tmin ≤ 50oC for C-Mn and 13Cr pipelinesB Minimum temperature, 0oC ≤ Tmin ≤ 20oC for 22Cr and 25Cr pipelinesC Maximum temperature, Tmax > 50 for C-Mn and 13Cr pipelinesC Maximum temperature, Tmax > 20 for 22Cr and 25Cr pipelines1) If pipelines are installed as illustrated in Figure 9 b), it is acceptable to pre-compress all material prior to testing2) See G204

Table A-12 Required material condition and test temperature for tensile testing ECA Category Material condition to be

testedTest temperatures

A B CECA Static - low, εl,nom < 0.4% during both installation and operation As-received Tmin RT TmaxECA Static - high, εl,nom ≥ 0.4% during installation1) As-received Tmin RT TmaxECA Static – high, εl,nom ≥ 0.4% during operation Pre-strained and aged Tmin RT TmaxAssessment temperatures in consideration:A Minimum temperature, Tmin < 0oCB Minimum temperature, 0oC ≤ Tmin ≤ 50oC for C-Mn and 13Cr pipelinesB Minimum temperature, 0oC ≤ Tmin ≤ 20oC for 22Cr and 25Cr pipelinesC Maximum temperature, Tmax > 50 for C-Mn and 13Cr pipelinesC Maximum temperature, Tmax > 20 for 22Cr and 25Cr pipelines1) If pipelines are installed as illustrated in Figure 9 b), it is acceptable to pre-compress all material prior to testing

⎟⎠⎞

⎜⎝⎛ +

=

2UTSYSm

Jδ

Wann

Wam 418.1751.2793.0221.1 −++=

32

965.3326.8098.6724.1 ⎟⎠⎞

⎜⎝⎛−⎟

⎠⎞

⎜⎝⎛+⎟

⎠⎞

⎜⎝⎛−=

UTSYS

UTSYS

UTSYSn

YS = The engineering yield stress at test temperatureUTS = The tensile strength at the test temperaturem = Constraint parameter according to ASTM

E1290-02n = The strain-hardening parameter accordinga = The original crack sizeW = The specimen width

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— The “Bauschinger effect”, as illustrated in Figure 7— Strain hardening, as illustrated in Figure 8— Aging.

Figure 7 The Baushinger effect is a phenomenon which occurs when mate-rials are strained into the non-linear stress-strain area in one di-rection followed by straining in the opposite direction. The effectof such cycling is that the reversed yield stress is decreased

Figure 8 Cyclic strain hardening is the effect seen if a material is strainedin one direction followed by unloading before the material isstrained in the same direction once more, see Figure 7. The effectof such cycling is that the yield stress is increased and that thestrain-hardening is decreased

203 Figure 9 illustrates the moment/curvature cycles for twodifferent installation methods introducing large plastic strains. For reeling installation, Figure 9 a), the most critical situationis theoretically reeling-on at 12 o’clock because the tensileproperties are represented by the highest stress-strain curvewith little strain hardening. However, the strain increment maybe larger at the 6 o’clock location in the straightener and thissituation shall also be considered. For other installation methods, it is important that the wholeinstallation sequence is evaluated in order to determine thelargest strain increment. In some cases it may be acceptable topre-compress the material prior to tensile and fracture mechan-

ics testing, e.g. the strain increment marked in Figure 9 b). Insuch cases ageing is not required. 204 If the ECA includes situations where the pipeline hasalready been subject to plastic strains, the tensile testing andfracture mechanics testing shall be performed on material rep-resenting strained material with ageing if relevant. If it can bedocumented based on earlier experience that the fracturetoughness properties are not reduced because of pre-strainingand aging it is acceptable to perform fracture toughness testingin the as-received condition.If the loading situation to be evaluated takes place more thanone week after the material was plastically deformed duringinstallation or operation, the tensile testing shall be performedon pre-strained and aged material.If the load condition is strain-based, the pre-straining cyclingshall end in tension because this will give upper-bound tensileproperties and little strain hardening.If the load condition is stress-based, the pre-straining cyclingshall end in compression because this will give lower-boundtensile properties.205 The pre-straining shall simulate one complete strain his-tory (i.e. the whole installation sequence, but not contingencyetc.) if ECAs are required for the operational phase.

H. ECA Validation Testing

H 100 General101 Segment specimen testing or full scale testing shall beperformed for the following situations where “ECA static” isapplicable and more than one strain increments are applied:

— Clad or lined pipelines.— C-Mn linepipe materials with SMYS larger than 450 MPa

and εl,nom > 1.5%.— 13Cr martensitic steels and εl,nom > 1.5%.— 22Cr and 25Cr duplex stainless steels if εl,nom > 1.5%.— If maximum total strain, εl,nom exceeds 2.25%.

102 The segment testing shall be performed based on theprocedure described in DNV-RP-F108 and Appendix B. Theamount of testing and the strain cycles applied shall be agreed.103 It is recommended that where a segment test is requiredthe dimensions of the starter flaw should be determined by anECA tailored to the segment test prior to testing and based onthe lower bound fracture toughness curve. The tip of the starterflaw should be in the lowest toughness material consistent withthe ECA. The dimensions of the starter flaw should be suchthat approximately 0.5 mm of tearing (or as agreed) at thedeepest point is predicted. Upper bound values of tensilestrength consistent with the values used in ECA should beused. If less tearing than estimated in the ECA is measured inthe segment specimens and the stress capacity is at least aslarge as estimated by ECA, the ECA is considered validated.

σ

ε

σ

ε

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a) Reeling installation

b) Installation method introducing large plastic strain incrementFigure 9 Examples of installation methods introducing large plastic strain increments

Reel drum

Aligner

Straightener

-600

-500

-400

-300

-200

-100

0

100

200

300

400

500

600

-2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5

Curvature

Mom

ent

12 o'clock6 o'clock

Crack driving force

Crack driving force

Straightener

Aligner

Bending on vessel

Curvature

Mom

ent

6 o'clock12 o'clock

Crack driving force 12 o'clock over ramp

Crack driving force no. 1, 6 o'clockCrack driving force no. 2, 6 o'clock

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Offshore Standard DNV-OS-F101, October 2007 – App.B

APPENDIX B MECHANICAL TESTING AND CORROSION TESTING

A. Mechanical Testing and Chemical Analysis A 100 General101 This appendix addresses methods for mechanical test-ing, chemical analysis and corrosion testing of materials andproducts.102 Test laboratories shall meet the requirements of ISO17025, General requirements for the competence of testingand calibration laboratories, or an accepted equivalent.103 The following standards are referred to in this Appen-dix:

— API 5LD— API RP 5L3— ASTM A264— ASTM A 956— ASTM A 1038— ASTM E110— ASTM E1820— ASTM G48— BS 7448— BS 7910— DNV-RP-F108— ISO 148— ISO 377— ISO 3183— ISO 4136— ISO 5173— ISO 5178— ISO 6507— ISO 6892— ISO/TR 9769— ISO 14284— ISO 15156— ISO 17025— NACE TM0284

A 200 General requirements to selection and prepara-tion of samples and test pieces201 Selection of samples and preparation of test pieces shallas far as applicable be in accordance with the general condi-tions of ISO 377. In addition the following requirements apply.202 For any of the mechanical tests, any test piece that showsdefective preparation or material imperfections unrelated tothe intent of the particular mechanical test, whether observedbefore or after testing, may be discarded and replaced byanother test piece from the same pipe.Samples and test pieces from linepipe203 For tensile tests, CVN impact tests, DWT tests, guided-bend tests, and flattening tests, the samples shall be taken, andthe corresponding test pieces prepared, in accordance with theapplicable reference standard.204 Samples and test pieces for the various test types forlinepipe shall be taken from alternating pipe ends in the loca-tions as shown in Figure 5 and Figure 6 in ISO 3183 and asgiven in Sec.7 Table 7-9, and the details stated below.Samples and test pieces from components205 Unless otherwise stated the location of samples and testpieces from components shall be according to Sec.8 E100.206 For induction bends and bolts the location of samplesand test pieces shall be according to the recognised standard orspecification used for manufacture, as specified for the rele-vant component in Sec.8.

Samples and test pieces for welds not performed at pipe mills207 For welds not performed as part of linepipe fabrication,including girth welds, samples shall be taken in accordanceAppendix C Figure 1 and 2.

A 300 Chemical analysis301 Samples for heat and product analyses shall be taken andprepared in accordance with ISO 14284. Methods and proce-dures for chemical analysis shall be according to recognisedindustry standards, of acceptable uncertainty. Results fromchemical analyses shall be given with the same number of dig-its (or more) as given in the specification of the product and/orin this standard.

Guidance note:ISO/TR 9769 gives a list of available international standards pro-viding chemical analysis methods, with information on the appli-cation and precision of the various methods.


Chemical analysis of weld overlay302 The chemical composition of the weld overlay shall beobtained at the surface of the overlay after machining of theoverlay such that the minimum distance from the surface to thefusion line is either 3 mm or the minimum thickness specifiedfor the finished component, whichever is the lesser.

A 400 Tensile testing401 Tensile testing shall be carried out in accordance withthe requirements in this appendix and ISO 6892 or ASTMA370. The test piece configuration and possible test piece flat-tening shall be the same for all the delivered items. The exten-someter shall be attached to a machined surface. Double sidedextensometers should be used.402 Base material tensile properties may be determinedusing rectangular or round test pieces at the manufacturers dis-cretion, see A403 and A404, respectively.403 Rectangular test pieces shall represent the full wallthickness. Longitudinal/axial test pieces shall not be flat-tended. Transverse/tangential test pieces shall be flattened.Test piece grip ends may be flattened or machined to fit the testmachine's grips. Weld beads may be ground flush and localimperfections may be removed.404 Round test pieces shall be obtained from non-flattenedsamples. For longitudinal/axial tensile tests when t ≥ 19.0 mm,such test pieces shall be 12.7 mm in diameter. For transverseor tangential tensile tests the diameter of such test pieces shallbe as given in Table 21 in ISO 3183, except that the next largerdiameter may be used at the option of the manufacturer.405 For testing when D < 219.1 mm, full-section longitudi-nal/axial test pieces may be used at the option of the manufac-turer.406 If agreed, ring expansion test pieces may be used for thedetermination of transverse yield strength.407 All weld tensile tests shall be carried out using round testpieces.408 For pipes to be tested according to supplementaryrequirement P specimens shall be of proportional type withgauge length of value 5.65 S0, where S0 is the cross sectionarea of the specimen.Transverse weld (cross weld) tensile test409 Test pieces shall be rectangular and in accordance with

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Offshore Standard DNV-OS-F101, October 2007 App.B –

A403. The weld reinforcement shall be removed on the faceand root sides by machining or grinding. The tensile strengthshall be determined (yield stress and elongation is notrequired).410 Transverse weld tensile test pieces of clad or lined line-pipe shall be performed on the full thickness of the carbonsteel, after removal of the CRA, taking care not to reduce theC-Mn steel wall thickness.All-weld tensile testing of load bearing weld overlay411 Test pieces shall be round with maximum obtainablediameter. The test pieces shall be machined from the weldoverlay transverse to the welding direction.Transverse all-weld tensile test for girth welds412 The geometry of the test pieces shall be according toFigure 13. The test requires that the width of the weld is at least6 mm. The test pieces shall be round with maximum obtainablediameter and be instrumented with strain gauges on thereduced section representing the weld metal.

A 500 Charpy V-notch impact testing501 The test pieces shall be prepared in accordance with ISO148-1 without any prior flattening of the material. Testingaccording to ASTM A370 is acceptable if agreed. Each setshall consist of three specimens taken from the same test cou-pon. Full size test pieces shall be used whenever possible. 502 The size, orientation, and source of the test pieces fromlinepipe shall be as given in Table 22 in ISO 3183, except thatthe next smaller test piece size may be used if the absorbedenergy is expected to exceed 80% of the full-scale capacity ofthe impact testing machine. Additional sets of HAZ test piecesshall be sampled compared to ISO 3183, see Table 7-7 andTable 7-8 in Sec.7. The notch locations shall be according toA508-513.

Guidance note:It is not necessary to impact-test linepipe with combinations ofspecified outside diameter and specified wall thickness not cov-ered by Table 22 in ISO 3183.


503 During MPQT, for seamless pipe with t > 25 mm anddelivered in the quenched and tempered condition, one set oftransverse direction CNV test pieces shall be sampled 2 mmabove the internal surface.504 The locations of test pieces taken from components shallbe according to Sec.8 E100. 505 The locations of test pieces taken from girth welds shallbe according to Appendix C Figure 1 and Figure 2. 506 The test pieces shall be sampled 2 mm below the exter-nal surface, except for testing of the root of double sided welds.A smaller distance than 2 mm shall be used if necessary (dueto the dimensions of the material) to make specimens with thelargest possible cross section. The axis of the notch shall beperpendicular to the surface.507 For weld metal and HAZ tests, each test piece shall beetched prior to notching in order to enable proper placement ofthe notch.Notch positioning for weld metal test pieces508 For production welds other than HFW pipe the axis ofthe notch of the weld metal sample shall be located on, or asclose as practical to, the centreline of the outside weld bead.509 For test pieces taken in the weld of HFW pipe, the axisof the notch shall be located on, or as close as practical to theweld line.Notch positioning for HAZ test pieces510 The HAZ notch positions comprise the fusion line (FL)test pieces, the FL+2 mm test pieces and the FL+5 mm Test

pieces shall be sampled in the positions given in Figure 3 toFigure 8, with the notch positions as applicable. FL test piecesshall always be located such that 50% of weld metal and 50%of HAZ is sampled.511 Impact testing of clad/lined pipes shall be performed inthe carbon steel portion of the material.512 When dissimilar materials are welded, both sides of theweld shall be tested.513 For weld overlay material contributing to the transfer ofload across the base material/weld overlay fusion line, impacttesting of the weld overlay and HAZ shall be performed (i.e.when the overlay is a part of a butt joint or acts as a transitionbetween a corrosion resistant alloy and a carbon steel). Thelongitudinal axis of the specimen shall be perpendicular to thefusion line and the notch parallel to the fusion line.

A 600 Bend testingGuided-bend testing of the seam weld of welded pipe 601 The test pieces shall be prepared in accordance with ISO7438 or ASTM A370, and Figure 8 in ISO 3183.602 For pipe with t > 19.0 mm, the test pieces may bemachined to provide a rectangular cross-section having athickness of 18.0 mm. For pipe with t ≤ 19.0 mm, the testpieces shall be full wall thickness curved-section test pieces.603 For SAW pipes, the weld reinforcement shall beremoved from both faces.604 The guided-bend test shall be carried out in accordancewith ISO 7438. The mandrel dimension shall not be larger thanthat determined using the following equation, with the resultrounded to the nearest 1 mm:

where:Agb is the mandrel dimension, expressed in millimetres

(inches)D is the specified outside diameter, expressed in millime-

tres (inches)t is the specified wall thickness, expressed in millimetres

(inches)e is the strain, as given in Table 231.15 is the peaking factor.605 Both test pieces shall be bent 180° in a jig as shown inFigure 9 in ISO 3183. One test piece shall have the root of theweld directly in contact with the mandrel; the other test pieceshall have the face of the weld directly in contact with the man-drel.Bend testing of clad linepipe606 Weld clad or roll bonded clad pipe shall be subjected tobend testing (the longitudinal weldment shall not be included).Specimens shall be of full thickness, including the full thick-ness of the clad layer. The width of the specimens shall beapproximately 25 mm. The edges may be rounded to a radiusof 1/10 of the thickness.The specimens shall be bent 180° around a former with a diam-eter 5x the pipe wall thickness.607 Longitudinal weld root bend test shall include the corro-sion resistant alloy.

— The longitudinal axis of the weld shall be parallel to thespecimen, which is bent so that the root surface is in ten-sion.

— The width of the longitudinal root bend specimen shall beat least twice the width of the internal weld reinforcementor maximum 25 mm. The edges may be rounded to a

te

tDe

tDAgb −−−

−=

)12(

)2(15.1

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radius of 1/10 of the thickness.— The internal and external weld reinforcement shall be

removed flush with the original surfaces.— The thickness of the specimen shall be equal to the base

material thickness or a maximum of 10 mm, as shown inFigure 2.

— The specimen shall be bent to an angle of 180° using aformer with diameter 90 mm.

Bend testing for WPQT according to Appendix C608 Bend testing shall be performed in accordance with ISO5173. Bend test specimens shall have full wall thickness. Thewidth of root and face bend specimens shall be approximately25 mm. The width of side bend specimens shall be 10 mm. Theedges may be rounded to a radius of 1/10 of the thickness.609 Bend test of clad pipes shall be performed on full thick-ness of the pipe, including the corrosion resistant alloy.610 The weld reinforcement on both faces shall be removedflush with the original surfaces, as shown in Figure 1. The weldshall be located in the centre of each specimen.611 The specimens shall be bent to an angle of 180° using aformer with diameter depending on the specified minimumyield stress SMYS for the parent material. For materials withSMYS up to 360 MPa, the former diameter shall be 4x thick-ness of the test specimen. For materials with SMYS equal to orexceeding 415 MPa, the former diameter shall be 5x thicknessof the test specimen.612 If necessary, e.g. if one of the materials to be joined hasa lower yield stress than the other, guided bend testing inaccordance with ISO 5173 may be applied, using the sameroller diameter as for the conventional bend testing.613 After bending, the welded joint shall be completelywithin the tensioned region.Bend testing of weld overlay614 Side bend test specimens shall be used. The test speci-mens shall be sampled perpendicular to the welding direction.

— For pipes, the test specimens shall sample the full thick-ness of the weld overlay and the base material. For heavysection components, the thickness of the base material inthe specimen shall be at least equal to 5x the thickness ofthe overlay.

— The thickness of side bend specimens shall be 10 mm. Theedges may be rounded to a radius of 1/10 of the thickness.The central portion of the bend test specimen shall includean overlap area.

— The specimens shall be bent to an angle of 180°. For basematerials with SMYS up to 415 MPa the former diametershall be 4x thickness of the test specimen. For base mate-rials with SMYS equal to or exceeding 415 MPa theformer diameter shall be 5x thickness of the test specimen.

A 700 Flattening test701 The test pieces shall be taken in accordance with ISO8492, except that the length of each test piece shall be ≥ 60mm. Minor surface imperfections may be removed by grind-ing.702 The flattening test shall be carried out in accordancewith ISO 8492. As shown in Figure 6 in ISO 3183, one of thetwo test pieces taken from both end-of-coil locations shall betested with the weld at the 6 or 12 o’clock position, whereas theremaining two test pieces shall be tested at the 3 or 9 o’clockposition. Test pieces taken from crop ends at weld stops shallbe tested at the 3 or 9 o’clock position only.

A 800 Drop weight tear test801 Drop weight tear test shall be carried out in accordancewith API RP 5L3.

802 Full thickness specimens shall be used where possible.Reduced thickness specimens may be used subject to Pur-chaser agreement. If reduced thickness specimens are used,both surfaces shall be equally machined to the thickness of19.0 mm. The testing temperature reduction given in API RP5L3 shall apply.The specimens shall be taken transverse to the rolling directionor pipe axis, with the notch perpendicular to the surface.For high toughness steels ductile crack initiation from thenotch tip shall be acceptable (contrary to API RP 5L3,Clause 7.1).

A 900 Fracture toughness testing901 For qualification testing of linepipe weld metal, see 904and 913 to 916:

— for qualification testing of girth welds, see 917 to 920.

902 The fracture toughness testing applicable to this Stand-ard is:

— Fracture toughness testing, J or CTOD (δ), a minimum of3 specimens is required for each notch position.

— Fracture toughness resistance curve testing, J-Δa (J R-curve) or δ-Δa (δ R-curve), a minimum of 6 specimens isrequired for each notch position.

903 Unless otherwise agreed fracture toughness testing shallbe performed using one of the following type of specimens:

— Single Edge Notched Tension (SENT), or— Single Edge Notched Bend (SENB) specimen

Pipeline walls are predominately loaded in tension independ-ent of the loading mode. The recommended specimen for suchconditions is the SENT specimen, as shown in Figure 12. Referalso to DNV-RP-F108 for further guidance.

Guidance note:Commonly used testing standards, e.g. BS 7448 and ASTME1820, describe methods for determining the fracture resistancefrom deeply notched SENB (Single Edge Notched Bend) or CT(Compact Tension) specimens. These specimens, both predomi-nantly loaded in bending, have high crack tip constraint and willhence give lower bound estimates for the fracture resistance thatcan be used for conservative fracture assessments for a largerange of engineering structures. The SENB specimen can also beused but this is likely to result in unnecessarily conservative frac-ture toughness.


904 Fracture toughness testing as required in Sec.7 for weldmetal shall be CTOD testing of SENB specimens.905 Other test specimen configurations may be used forderiving the fracture toughness for use in an ECA provided thatthe fracture toughness can be derived from experimental meas-urement, e.g. load vs. clip gauge displacement and that it is jus-tified that the crack tip constraint of the test specimen is notsmaller than for the most severe pipeline weld defect assessedin the ECA. 906 Testing of SENB specimens shall be carried out in gen-eral compliance with the latest revisions of the relevant partsof BS 7448 or an equivalent standard.All SENT testing shall be performed in accordance with DNV-RP-F108.907 Post-test metallography shall be applied to the speci-mens designated for FL/HAZ testing in order to establish if thecrack tip has been successfully located in the target microstruc-ture. The specimen is considered qualified if:

— the pre-crack tip is not more than 0.5 mm from fusion line

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— grain coarsened heat affected zone (GCHAZ) micro-struc-ture is present within a region confined by a plane perpen-dicular to the crack plane through the crack tip and aparallel plane 0.5 mm ahead of the crack tip.

Relevant for testing of SENB specimens 908 Testing of SENB specimens are acceptable, see 903,also with reduced notch length. However, for use in an ECAthe specimen notch length shall not be chosen shorter than theheight of the most severe weld defect assessed in the ECA. The fracture toughness for SENB test specimens can bederived from the load vs. clip gauge displacement recordaccording to the following formulae:

where Ap is the area under the load vs. crack mouth displace-ment (CMOD) curve. For definitions of the other parameters itis referred to BS 7448. 909 If the total displacement, Vg, is measured at a distancez ≤ 0.2a from the physical crack mouth then the CMOD can becalculated from:

910 The CTOD-value, δ, can be calculated from J accordingAppendix A, G106. Reporting of fracture toughness testing:911 The following information shall be reported from J/CTOD testing:

— load vs. crack mouth opening displacement curves of all tests— crack measurements (a0)— j or δ results— test temperature— material condition (possible pre-straining and aging his-

tory)— welding procedure and weld metal designation— parent pipe designation.

912 The following information shall be reported from J R-curve or δ R- curve testing:

— load vs. crack mouth opening displacement curves of all tests— crack measurements (a0 and Δa)— J-Δa or δ-Δa results— test temperature— material condition (possible pre-straining and aging history)— welding procedure and weld metal designation— parent pipe designation.

Fracture toughness testing of linepipe913 The following applies to fracture toughness testing oflinepipe as required during MPQT:

δ fracture toughness testing of the weld metal shall be per-formed using SENB specimens.

914 Testing shall be conducted on through thickness notchedspecimens with the specimen orientated transverse to the welddirection (The corresponding notation used by BS 7448 is NP).The notch shall be located in the weld metal centre line.

915 The number of valid CTOD or J tests for each locationshall be minimum 3. The characteristic CTOD or critical Jvalue shall be taken as the lowest from 3 valid tests or selectedin accordance with BS 7910. Only specimens that are qualifiedwith respect to crack tip location by post-test metallographicexamination shall be considered valid.916 If fracture toughness testing of the FL/HAZ of the seamweld is performed, surface notched specimens shall be tested.It is acceptable to test SENT specimens. It is important that theweld metal is not mechanically deformed during fabrication ofspecimens. For SENB specimens the instructions specified inBS 7448-2 shall be followed. For SENT specimens it is nor-mally required to cut out the seam weld and at least 10 mm ofthe parent pipe on each side of the seam weld. Extensions arebutt welded until required specimen length before the speci-men is finally machined to a SENT specimen.Validation of the crack tip shall be performed, see A907.Qualification of girth welds (ECA)917 The recommended specimen for fracture toughness test-ing of girth welds is the SENT (Single Edge Notched Tension)specimen. The calculation and performance of SENT testingshall be according to DNV-RP-F108.918 The SENT specimens shall be designed with a SurfaceNotch (SN), since this is the relevant orientation for defects inthe welds. The notch may be introduced either from the outersurface or from the inner surface.919 The notch positions and welding procedures to be testedshall be agreed. Typically the main line procedure(s), thethrough thickness procedure(s) and the partial repair proce-dure(s) shall be tested as illustrated in Figure 9 and specified inAppendix A Tables A-1, A-5 and A-7 as relevant.

Guidance note:It is recommended that the FL/HAZ is notched from the outersurface. Such notching is empirically more successful becausethe crack growth tends to grow towards the base material. Hence,a crack tip at the FL boundary is typically growing through theHAZ if it is notched from the outer surface.


920 For situations involving plastic deformation and possi-bility of unstable fracture caused by tearing, crack resistancecurve testing (preferably J R-curve) shall be performed of thegirth weld. If the SENT specimen is tested, which is recom-mended, the testing shall be in accordance with DNV-RP-F108.921 If segment testing is required, see Appendix A, H101,testing shall be performed based on DNV-RP-F108. Theamount of testing and test procedure shall be adjusted to theloading considered.

A 1000 Specific tests for clad and lined linepipe1001 Shear testing shall be performed in accordance withASTM A264 (Standard Specification for Stainless Chromium-Nickel Steel-Clad Plate, Sheet and Strip).1002 Gripping force of lined pipe shall be measured by theresidual compressive stress test, in accordance with Clause 7.3b of API 5LD.

A 1100 Metallographic examination and hardness testingMacro examination1101 Macro examination shall be performed at 5X to 10Xmagnifications (for HFW the examination shall be performedat minimum 40X and be documented at least 20X magnifica-tion). Macro examination shall be conducted on specimensgiven in Figures 10 and 11, as applicable. The macro sectionshall include the whole weld deposit and in addition include atleast 15 mm of base material on each side measured from anypoint of the fusion line. The macro-section shall be prepared by

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grinding, polishing, and etched on one side to clearly reveal thefusion line and HAZ.The macro examination of weld overlay shall be sampledtransverse to the welding direction. The width of the macrosection shall be minimum 40 mm. The face exposed by sec-tioning shall be prepared by grinding, polishing and etched bya suitable etchant to clearly reveal the weld and heat affectedzone.Microstructure examination1102 Samples for optical metallography shall be preparedusing standard procedures, and further etched using a suitableetchant in order to reveal the microstructure.Micro examination of duplex stainless steels shall be per-formed and documented at a minimum magnification of 400X.The ferrite content of the base material and weld metal shall bemeasured according to ASTM E562.Hardness testing1103 Hardness testing of base material and weld cross-sec-tion samples shall be carried out using the Vickers HV10method according to ISO 6507-1.1104 For pipe base material tests, individual hardness read-ings exceeding the applicable acceptance limit may be consid-ered acceptable if the average of a minimum of three andmaximum of six additional readings taken within close prox-imity does not exceed the applicable acceptance limit and if nosuch individual reading exceeds the acceptance limit by morethan 10 HV10 units.1105 Hardness test locations for SMLS pipe shall be asshown in Figure 10 a), except that:

— when t < 4.0 mm, it is only necessary to carry out the mid-thickness traverse

— for pipe with 4.0 mm ≤ t < 6 mm, it is only necessary tocarry out the inside and outside surface traverses.

1106 Hardness testing of welds shall be performed on thespecimens used for macro examination, and as shown in Fig-ures 10 b) and c), and Figure 11.1107 For SAW, HFW and MWP the following applies:

— for pipe with t < 4.0 mm, it is only necessary to carry outthe mid-thickness traverse

— for pipe with 4.0 mm ≤ t < 6 mm, it is only necessary tocarry out the inside and outside surface traverses.

1108 In the weld metal of SAW and MWP welds, a mini-mum of 3 indentations equally spaced along each traverse shallbe made. In the HAZ, indentations shall be made along thetraverses for each 0.5 - 1.0 mm (as close as possible but pro-vided indentation is made into unaffected material, and startingas close to the fusion line as possible according to Figure 10 b).1109 Hardness testing of clad/lined pipes shall have oneadditional hardness traverse located in the thickness centre ofthe CRA material. See Figure 11.1110 For hardness testing of weld overlay hardness testingshall be performed at a minimum of 3 test locations: in the basematerial, in the HAZ and in each layer of overlay up to a max-imum of 2 layers.Surface hardness testing1111 Surface hardness testing, e.g. of suspected hard spotsdetected by visual inspection, shall be carried out in accord-ance with ISO 6506, ISO 6507, ISO 6508, or ASTM A370using portable hardness test equipment. Depending on themethod used the equipment shall comply with ASTM A956,ASTM A1038 or ASTM E110.

A 1200 Straining and ageingAgeing test1201 This test is applicable if the cold forming during pipemanufacture of C-Mn and clad/lined steels exceeds 5% strainand for Supplementary requirement F. This test does not applyto linepipe delivered with a final heat treatment (e.g. normalis-ing or quench and tempering).A test coupon shall be machined from the pipe material andaged at 250°C for one hour. Thereafter, the specified numberof Charpy V-notch specimens shall be machined from the mid-dle of the coupon. The orientation of the specimens shall belongitudinal to the coupon centreline, with the notch perpen-dicular to the surface of the test coupon.Pre-straining and ageing of materials1202 Pre-straining is applicable to:

— Linepipe material to be qualified in accordance with Sup-plementary requirement P.

— Girth welds to be qualified in accordance withAppendix A (ECA).

1203 Pre-straining can be carried out as full scale (reversed)bending of whole pipes sections or as tension/compressionstraining of material cut from the pipe wall.1204 When full scale bending is applied whole pipes sec-tions they shall be instrumented with strain gauges on the out-side of the pipe wall in the 12 and 6 o'clock positions, seeFigure 14 a). A sufficient number of strain gauges shall be fit-ted along the length of the test section to ensure an efficientmonitoring of the strain along the whole test section.1205 When pre-straining cut material such material shall befitted with strain gauges on each of the opposite sides withrespect to the smallest measure on the cross section, seeFigure 14 b). A sufficient number of strain gauges shall be fit-ted along the length of the test section to ensure an efficientmonitoring of the strain along the whole test section. If the testmachine is not sufficiently rigid, strain gauges shall also be fit-ted either sides along the long cross section.1206 The strain gauges shall be logged with sufficient fre-quency during the straining cycle to ensure efficient monitor-ing of the cycle.1207 The pre-straining shall be carried out in such a way thatthe characteristic strain (see below) does not deviate by morethan ±0.10% of units of strain from the specified cycle whenmeasured at the corners of the pre-straining cycle where thestrain rate changes sign.1208 The characteristic strain shall for cut material bedefined as the mean value of the strains measured on the out-side and inside of the pipe wall for pre-straining materialencompassing the full pipe wall thickness. See Figure 14 b).For pre-straining material not encompassing the full pipe wallthickness the average strain shall be defined as the mean valueof the strains measured on the two opposite sides of the mate-rial of the smallest thickness. For full scale bending of spoolpieces the characteristic strain is defined as the strain measuredon the outside of the pipe wall.1209 The difference between the average strain and eachstrain gauge shall not exceed ±20% of the specified strainwhen measured at the corners of the pre-straining cycle wherethe strain rate changes sign. If the difference is larger, the fullstraining cycle as measured on each strain gauge shall bereported and it shall be ensured that test pieces fabricated arefabricated from pre-strained material that complies with therequirement to the straining cycle. If this is not possible addi-tional material shall be pre-strained or acceptance from the cli-ent be obtained.1210 After straining for Supplementary requirement P, thesamples shall be artificially aged at 250°C for one hour before

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testing. Regarding artificial ageing for ECA, see Appendix AG200.

A 1300 Testing of pin brazings and aluminothermic weldsCopper penetration1301 2 test specimens shall the sectioned transverse to theanode lead and 2 test specimens parallel with the anode lead.The specimens shall be prepared and etched for metallographicexamination. The examination shall be performed at a magni-fication of 50X. The fusion line of the weld/brazing shall at anypoint not be more than 1.0 mm below the base material surface.Intergranular copper penetration of the base material shall notat any point extend beyond 0.5 mm from the fusion line.Hardness1302 HV10 hardness tests shall be made on each of the spec-imens for copper penetration measurements. A traverse shallbe made across the weld/brazing zone. The traverse shall con-sist of minimum 6 indentations; two in the heat affected zone(HAZ) on each side of the weld/brazing, two in the HAZ underthe weld/brazing and two in the base material on each side ofthe weld/brazing. The HAZ indentations shall be made as closeto the fusion line as possible.1303 The maximum hardness shall not exceed the limitsgiven in Appendix C as applicable for the intended service andtype of material.Pull test1304 The test specimen shall be mounted in a tensile testingmachine and secured in the cable in one end and the base mate-rial in the other end. Force shall be applied until the specimenbreaks. The specimen shall break in the cable.

B. Corrosion TestingB 100 General101 For certain material and fluid combinations whereimproper manufacture or fabrication can cause susceptibilityto corrosion related damage, the need for corrosion testing dur-ing qualification and/or production of materials shall beassessed. Certain corrosion tests are further applicable to ver-ify adequate microstructure affecting toughness in addition tocorrosion resistance. This subsection describes test require-ments and methods for corrosion testing.

B 200 Pitting corrosion test201 This test is applicable to verify CRAs’ resistance to pit-ting and crevice corrosion by oxidising and chloride contain-ing fluids, e.g. raw seawater and other water containing fluids(including treated seawater) with high residual contents ofoxygen and/or active chlorine. For duplex stainless steels, thistest is further applicable to verify adequate microstructure aftermanufacturing or fabrication (see B101).202 Testing shall be carried out according to ASTM G48"Standard Test Methods for Pitting and Crevice CorrosionResistance of Stainless steels and Related Alloys by the Use ofFerric Chloride solutions", Method A.203 Location of specimens is given in Appendix C, Figures1 and 2.204 The minimum recommended size of test specimens is 25mm wide by 50 mm long by full material thickness (except asallowed by 205). For welds, at least 15 mm of the base materialon each side of the weld shall be included in the test specimen.205 Test specimens from clad/lined pipe shall be machinedto remove the carbon steel portion and are to contain the fullweld and any heat affected zone in the corrosion resistantalloy. The specimen thickness shall as a minimum be 1 mm

where one of the surfaces is representing the inside of the pipe.206 Rolled surfaces shall be tested "as-received", i.e. with-out mechanical preparation. The root and the cap side of thewelds are only to be prepared with the intention of removing"loose material" that will interfere with weighing prior to andafter testing. Cut faces shall be ground (500 grid) and sharpedges smoothed off. The specimen shall subsequently be pick-led to reduce the susceptibility of cut surfaces to end-grainattack. For duplex stainless steels and austenitic grades withPRE > 30, 20% nitric acid + 5% hydrofluoric acid, 5 minutesat 60°C is adequate.207 The test solution shall be prepared according to the ref-erenced standard. Corrosion testing of weld overlay208 Specimens for corrosion testing of the weld overlayshall be machined from the base material side. The remainingsurface of the specimen shall be representative for the weldoverlay at the minimum distance from the fusion line (equal to3 mm or the minimum weld overlay thickness specified for thefinished machined component, whichever is the lesser). Theopposite surface of the specimen shall be machined such thatthe thickness of the specimen is 2 mm. The size of the speci-men shall be 25 × 25 mm in length and width.

B 300 Hydrogen Induced Cracking test301 Testing for Hydrogen Induced Cracking (HIC), alsoreferred to as StepWise Cracking (SWC), as defined in ISO15156 is applicable to rolled C-Mn steel linepipe and pipelinecomponents. Testing shall be according to ISO 15156-2, B.5(referring to NACE TM0284 "Evaluation of Pipeline Steels forResistance to Stepwise Cracking II). 302 Unless otherwise agreed tests shall be conducted in amedium complying with NACE TM0284, Solution A.If agreed, tests may be conducted:

— in an alternative medium (see ISO 15156-2:2003, TableB.3) including NACE TM 0284 Solution B

— with a partial pressure of H2S appropriate to the intendedapplication

— with acceptance criteria that are equal to or more stringentthan those specified in Sec.7 I110.

Values of crack length ratio, crack thickness ratio, and cracksensitivity ratio shall be reported. If agreed, photographs ofany reportable crack shall be provided with the report.

B 400 Sulphide Stress Cracking testQualification of new materials401 For qualification of new materials (i.e. not listed for sourservice in ISO 15156-2/3), testing shall be conducted on spec-imens from at least 3 heats of material. Qualification testingshall include testing of simulated girth welds and for weldedpipe also seam welds, in addition to longitudinal samples of thebase material. Specimen preparation, testing procedures andacceptance criteria shall comply with ISO 15156, using tripli-cate specimens for each testing condition (i.e. heat of materialand environment).402 Materials listed for sour service in ISO 15156 but notmeeting the requirements in Sec.7 I100, (e.g. maximum hard-ness or contents of alloying or impurity elements) may be qual-ified by testing for resistance to Sulphide Stress Cracking(SSC) as specified in B401, except that testing shall be carriedout on material representing the worst case conditions to bequalified (e.g. max. hardness or max. sulphur content).Qualification of pipe manufacturing403 As an option to Purchaser, SSC testing may be carriedout for qualification of pipe manufacturing. One longitudinalbase material sample shall be taken from each test pipe.

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404 For welded linepipe, testing shall include one additionalsample transverse to the weld direction (samples W or WSaccording to Figure 5 in ISO 3183) and shall contain a sectionof the longitudinal or helical seam weld at its centre.405 Three test pieces shall be taken from each sample.Unless otherwise agreed, test pieces for four-point bendingSSC tests shall be ≥ 115 mm long × 15 mm wide × 5 mm thick.Samples may be flattened prior to machining test pieces fromthe inside surface of the pipe.406 Unless otherwise agreed tests shall be performed inaccordance with NACE TM0177, using Test Solution A. Afour-point bend test piece in accordance with ISO 7539-2 shallbe used and the test duration shall be 720 h. The test piecesshall be stressed to a fraction of SMYS appropriate for thepipeline design, see Table 13-3, however minimum 72% of thematerial SMYS.

Figure 1 Bend test specimens

Figure 2 Longitudinal root bend test specimens

— The "FL" specimen shall sample 50% WM and 50% HAZ— The "FL+5 mm" sample is applicable to WPQT only.

Figure 3 Charpy V-notch impact testing specimen positions for single sid-ed welds with t ≤ 25 mm

— The "FL" specimen shall sample 50% WM and 50% HAZ — The "FL+ 5 mm" sample is applicable to WPQT only.

Figure 4 Charpy V-notch impact test specimen positions for single sidedwelds with t > 25 mm

W

t

l ≥ 200 mm W

r ≤ 0.1 t. max. 3.0 mm (all edges)

t = Specimen thickness, t = 10 mm. W = Width of specimen = Base material thickness The weld reinforcement is to be machined / ground flush with the base material

b) FACE/ROOT BEND TEST SPECIMEN (Pl./pipe mat. thickness t < 20 mm.

t l ≥ 200 mm r ≤ 0.1 t. max. 3.0 mm

(all edges)

W

t = Specimen thickness = Base material thickness. W = Width of specimen, W = 1.5 t, min. 20 mm The weld reinforcement is to be machined / ground flush with the base material

t

a) SIDE BEND TEST SPECIMEN (Pl./pipe mat. thickness t ≥ 20 mm.

t

l ≥ 200 mm

T

W

t = Specimen thickness = 10 mm W = Width of specimen = 30 mm T = Base material thickness The weld reinforcement is to be machined / ground flush with the base material

t

r ≤ 0.1 t. max. 3.0 mm (all edges)

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— The specimens indicated in the root area are only applica-ble when t > 25 mm)

— The "FL" specimen shall sample 50% WM and 50% HAZ— The "FL+5 mm" samples are applicable to WPQT only

(not at pipe mill).

Figure 5 Charpy V-notch impact test specimen positions for double sidedwelds

— The specimens indicated in the root area are only applica-ble when t > 25 mm).

Figure 6 Charpy V-notch impact test specimen positions for HF welds

— The "FL" specimen shall sample 50% WM and 50% HAZ — The "FL+5 mm" sample is applicable to WPQT only.

Figure 7 Charpy V-notch impact test specimen positions for full thicknessrepair welding of narrow gap welds

— The "FL" specimen shall sample 50% WM and 50% HAZ — The "FL+5 mm" sample is applicable to WPQT only.

Figure 8 Charpy V-notch impact test specimen positions for partial thick-ness repair welding

Figure 9 Illustration of typical notch positions for fracture toughness testing of girth welds

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Figure 10 Hardness locations in a) seamless pipes, b) HFW pipe, and c) fusion welded joints.

Figure 11 Hardness locations clad materials

Figure 12 The clamped SENT (Single Edge Notched Tension) specimen

Figure 13 Tensile specimen for determination of stress/strain curves of weldmetals in the weld transverse direction

Figure 14 Instrumentation of pipe section of samples for pre-straining ofmaterials

p

p

p = 1.5 mm ± 0.5 CENTRE OF CLAD

W

P

P

a

B

Gripped area

Gripped area

'Day-light'between grips, H

H = 10W

Strain gauges

Strain gauges

a) b)

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Offshore Standard DNV-OS-F101, October 2007 App.C –

APPENDIX C WELDING

A. Application

A 100 General101 This appendix applies to all fabrication involving shop-, site- or field welding including post weld heat treatment.Welding of longitudinal welds in pipe mills is covered inSec.7.102 The base materials covered by this appendix are:

— C-Mn and low alloy steels— corrosion resistant alloys (CRA) including ferritic auste-

nitic (duplex) steel, austenitic stainless steels, martensiticstainless steels (13Cr), other stainless steels and nickelbased alloys

— clad/lined steel.

The base material requirements are specified in Sec.7 andSec.8.

A 200 Welding processes201 Welding may be performed with the following processesunless otherwise specified:

— Shielded Metal Arc Welding, SMAW (Process ISO 4063-111)

— Flux Cored Arc Welding with active gas shield, G-FCAW(Process ISO 4063-136)

— Flux Cored Arc Welding with inert gas shield, G-FCAW(Process ISO 4063-137)

— Gas Metal Arc Welding with inert gas shield, GMAW(Process ISO 4063-131)

— Gas Metal Arc Welding with active gas shield, GMAW(Process ISO 4063-135)

— Tungsten Inert Gas Arc Welding, GTAW (Process ISO4063-141)

— Submerged Arc Welding, SAW (Process ISO 4063-12)— Plasma arc welding, PAW (Process ISO 4063-15) may be

used for specific applications.

Guidance note:GMAW and FCAW are regarded as methods with high potentialfor non-fusing type defects.


202 The following processes may be used for specific appli-cations subject to agreement:

— Laser beam welding, LBW (Process ISO 4063-52)— Electron beam welding, EBW(Process ISO 4063-51)— Electro slag welding— Plasma transferred arc welding, PTA.

203 Mechanised and automatic welding systems where pre-vious experience is limited, or where the system will be usedunder new conditions, shall be subject to a more extensive pre-qualification programme or documentation before they may beused. The extent and the contents of a pre-qualification pro-gramme for such mechanised welding systems shall be agreedbefore start up. The Contractor shall prove and document thatthe welding systems are reliable and that the process can becontinuously monitored and controlled.

A 300 Definitions301 The following definitions are used in this appendix:

A 400 Quality assurance401 Requirements for quality assurance are given in Sec.2B500.

B. Welding Equipment, Tools and Personnel

B 100 Welding equipment and tools101 Inspection of the workshop, site or vessel prior to start ofwelding shall be required. This shall include verification ofcalibration and testing of all tools and welding equipment usedduring qualification/production welding.102 Welding equipment shall be of a capacity and type suit-able for the work. The equipment shall be calibrated and main-tained in good working condition. 103 The control software for mechanised and automaticwelding systems shall be documented. The name and uniqueversion number of control software and the executable pro-gramme in use shall be clearly observable, e.g. on displaysand/or printouts.104 All welding equipment shall have a unique marking foridentification.105 Calibration status and the validity of welding, monitor-ing and inspection equipment shall be summarised giving ref-erence to the type of equipment, calibration certificate andexpiry date.106 Welding return cables shall have sufficient cross sectionarea to prevent concentration of current and shall be securelyattached to prevent arc burns.

Welder: Person who performs the welding.Manual welder:

Welder who holds and manipulates the elec-trode holder, welding gun, torch or blowpipe by hand.

Welding operator:

Welder who operates welding equipment with partly mechanised relative movement between the electrode holder, welding gun, torch or blowpipe and the work piece.

Manual welding:

Welding where the welding parameters and torch guidance are controlled by the welder.

Partly-mechanised welding:

Welding where the welding parameters and torch guidance are controlled by the welder, but where the equipment incorporates wire feeding.

Mechanised welding:

Welding where the welding parameters and torch guidance are fully controlled mechani-cally or electronically but where minor man-ual adjustments can be performed varied during welding to maintain the required welding conditions.

Automatic welding:

Welding where the welding parameters and torch guidance are fully controlled mechani-cally or electronically and where manual adjustment of welding variables during weld-ing is not possible and where the task of the welding operator is limited to preset, start and stop the welding operation.

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Offshore Standard DNV-OS-F101, October 2007 – App.C

B 200 Personnel201 All personnel involved in welding related tasks shallhave adequate qualifications and understanding of weldingtechnology. The qualification level shall reflect the tasks andresponsibilities of each person in order to obtain the specifiedquality level.Welding co-ordinator202 The organisation responsible for welding shall nominateat least one authorised welding co-ordinator in accordancewith ISO 14731 to be present at the location where welding isperformed. The welding co-ordinator shall have comprehen-sive technical knowledge according to ISO 14731, paragraph6.2. a.Welding operators and welders 203 Through training and practise prior to qualification test-ing, the welding personnel shall have a understanding of (seeAnnex D of ISO 9606-1):

— fundamental welding techniques— welding procedure specifications— relevant methods for non-destructive testing— acceptance criteria.

204 Welding operators performing automatic welding shallbe qualified according to EN 1418 or ISO14732.205 Welders performing manual, partly-mechanised weld-ing and mechanised welding shall be qualified for single sidebutt welds of pipes or plates in the required principal positionin accordance with ISO 9606-1, EN 287-1 or other relevantand recognised standards, for the respective positions, materialgrades and welding processes. These requirements are alsoapplicable for welders performing temporary welds and tackwelds.206 Welders shall be qualified for single side butt welding ofpipes in the required principal position. Welders may be qual-ified for part of the weld, root, fillers or cap by agreement.Repair welders may be qualified for partial thickness repair ona representative test configuration provided only such weldrepairs are made.207 The qualification test shall be carried out with the sameor equivalent equipment to be used during production welding,and should be at the actual premises, i.e. work shop, yard, andvessel. Use of other premises shall be specially agreed.208 Qualification NDT shall be 100% visual examination,100% radiographic or ultrasonic testing, and 100% magneticparticle or liquid penetrant testing. Test requirements andacceptance criteria shall be in accordance with Appendix D,subsection B.209 When using processes which have high potential fornon-fusing type defects, including G-FCAW (Process ISO4063-137) bend testing shall be performed with the number ofbend tests according to ISO 9606-1.210 A welder or welding operator who has produced a com-plete and acceptable welding procedure qualification isthereby qualified.Retesting211 A welder may produce additional test pieces if it is dem-onstrated that the failure of a test piece is due to metallurgicalor other causes outside the control of the welder/ welding oper-ator.212 If it is determined that the failure of a test is due towelder’s lack of skill, retesting shall only be performed afterthe welder has received further training.Period of validity213 The period of validity of a welder qualification shall bein accordance with the standard used for qualification. A qual-

ification can be cancelled if the welder/welding operator showinadequate skill, knowledge and performance.214 When a qualification testing of recent date is transferredto a new project, the welding personnel shall be informedabout particular project requirements for which their weldingperformance will be especially important.Identification of welders 215 Each qualified welder shall be assigned an identifyingnumber, letter or symbol to identify the work of that welder.216 Qualified welders shall be issued with and be carryingan ID card displaying the identifying number, letter or symbol. 217 The Welding Coordinator shall maintain a list of weld-ers ID stating the qualification range for each welderThermal cutters and air-arc gougers218 Personnel to perform air-arc gouging shall be trainedand experienced with the actual equipment. Qualification test-ing may be required.Operators for pin brazing and aluminothermic welding219 Operators that have performed a qualified procedure testare thereby qualified220 Other operators shall each complete three test piecesmade in accordance with the procedure specification prior tocarrying out operation work. Each test piece shall pass the testfor electrical resistance and mechanical strength according toTable C-6.

B 300 Qualification and testing of welding personnel for hyperbaric dry welding 301 Requirements for qualification and testing of weldingpersonnel for hyperbaric dry welding are given in subsection I.

C. Welding ConsumablesC 100 General101 Welding consumables shall be suitable for their intendedapplication, giving a weld with the required properties and cor-rosion resistance in the finally installed condition.102 Welding consumables for arc welding shall be classifiedaccording to recognised classification schemes.103 Welding consumables and welding processes shall givea diffusible hydrogen content of maximum 5 ml/100g weldmetal unless other requirements are given for specific applica-tions in this Appendix. Hydrogen testing shall be performed inaccordance with ISO 3690.104 For the FCAW welding processes it shall be docu-mented that the hydrogen content of the deposited weld metalwill be below 5 ml diffusible hydrogen per 100 g weld metalunder conditions that realistically can be expected for produc-tion welding.105 Welding consumables for processes other than manualor mechanised arc welding may require special considerationwith respect to certification, handling and storage.106 Depletion of alloying elements during welding per-formed with shielding gases other than 99.99% argon shall beconsidered.107 All welding consumables shall be individually markedand supplied with an inspection certificate type 3.1 accordingto EN 10204 or equivalent. Certificate type 2.2 is sufficient forSAW flux.Cellulose coated electrodes108 Cellulose coated electrodes may be used only subject toagreement for welding of pipeline girth welds in C-Mn linepipewith SMYS ≤ 450 MPa. If used the delay between completion

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of the root pass and the deposition of the hot pass is simulatedduring welding procedure qualification according to E108.109 Use of cellulose coated electrodes is not permitted for:

— repair welding of pipeline girth welds— welding of other than pipeline girth welds in C-Mn line-

pipe with SMYS ≤ 450 MPa.

Data Sheet110 Each batch of welding consumables shall be delivered inaccordance with a Manufacturer’s data sheet, which shall state:

— guaranteed maximum value for diffusible hydrogen in thedeposited weld metal

— the guaranteed minimum and maximum levels of C, alloy-ing elements and any other intentionally added elements

— guaranteed mechanical properties (tensile and impact)— determined under defined reference conditions. The data

sheet shall, when relevant, also give recommendations forhandling/recycling of the welding consumables in order tomeet the guaranteed maximum value for diffusible hydro-gen in the deposited weld metal.

Guidance note:The Contractor responsible for the welding and the welding con-sumable manufacturer should agree on the content and the spec-ified limits in the data sheets.


C 200 Chemical composition201 All welding consumables shall be delivered in accord-ance with Manufacturer's data sheets, which shall state theminimum and maximum levels of C, Mn, Is, P, S, micro-alloy-ing elements and any other intentionally added elements.202 For solid wire and metal powders, the chemical analysisshall represent the product itself. The analysis shall include allelements specified in the relevant classification standard andthe relevant data sheet.203 For coated electrodes and cored wires, the analysis shallrepresent the weld metal, deposited according to EN 26847(ISO 6847). The analysis shall include all elements specified inthe relevant classification standard and the relevant data sheet204 When sour service is specified, the chemical composi-tion of the deposited weld metal shall comply with ISO 15156.The Ni-content in welding consumables for girth welds in C-Mn steel may be increased up to 2% Ni, provided that otherrequirements in ISO 15156 are fulfilled, and that the weldingprocedure has been tested for resistance to SSC.205 The selection of welding consumables shall be givenspecial attention in order to avoid any types of preferentialweld corrosion. This applies particularly to material withenhanced corrosion properties, and for selection of weldingconsumable for the root pass in systems for seawater service.206 The chemical composition of the weld overlay materialsshall comply with the material requirements specified for theapplicable type of overlay material or with a project specifica-tion.

C 300 Mechanical propertiesPipeline girth welds301 For weld metal in pipeline girth welds shall, as a mini-mum have strength, ductility and toughness meeting therequirements of the base material.302 For girth welds exposed to strain εl,nom< 0.4%, the yieldstress (Rt0.5) of the weld metal should be minimum 80 MPaabove SMYS of the base material. If two grades are joined, therequirement applies to the SMYS of the lower strength basematerial, see Sec.6 D200.

303 For girth welds exposed to strain εl,nom≥ 0.4%, the yieldstress (Rt0.5) of the weld metal requires special attention withregard to straining and ageing and, when applicable, also to theproperties at elevated temperatures. ECA shall be conductedfor all girth welds exposed to a strain εl,nom ≥ 0.4% (seeAppendix A). Further details regarding to the requirements forweld metal tensile properties are given in Sec.6 B700. 304 Whenever an ECA is performed, the tensile properties ofthe weld metal shall be at least be equal to the properties used asinput to the ECA. If the properties of the weld metal do not meetthese requirements, it shall be validated that the assumptionsmade during design and/or the ECA have not been jeopardised.305 Whenever an ECA is performed and for steels withSMYS ≥ 450 MPa, any batch intended for use in productionwelding that was not qualified during welding procedure qual-ification, shall be qualified according to C400. 306 For girth welds, all batches of consumables used in pro-duction including possible wire / flux combinations should bequalified by testing during welding procedure qualification.307 Batch testing is not required for steels withSMYS < 450 MPa and when ECA is not performed if the ten-sile or impact properties stated on the Inspection Certificatesare not less than 90% of the batch used for welding procedurequalification.Pipeline components308 For welds in pipeline components the weld metal shall, asa minimum, have ductility and toughness meeting the require-ments of the base material and the actual yield stress (Rt0.5) ofthe deposited weld metal shall at least be 80 MPa above SMYSof the base material. If two grades are joined, the requirementapplies to the SMYS of the lower strength base material.

C 400 Batch testing of welding consumables for pipeline girth welds401 A consumable batch is defined as the volume of productidentified by the supplier under one unique batch/lot number,manufactured in one continuous run from batch/lot controlledraw materials.402 Batch testing shall be conducted to verify that consuma-bles that were not tested during qualification of the weldingprocedure will give a deposited weld metal nominally equiva-lent to those batches used for welding procedure qualification,with respect to chemistry and mechanical properties.403 The batch testing shall be performed for all welding con-sumables, including possible wire/flux combinations.404 Each individual product (brand name and dimensions)shall be tested once per batch/lot, except for solid wire origi-nating from the same heat, where one diameter may representall. SAW fluxes do not require individual testing but SAWwires shall be tested in combination with a selected, nominalbatch of flux of the same classification as used for the weldingof the girth welds.Mechanical testing405 The testing shall be performed on samples taken fromgirth welds welded according to the welding procedure to beused in production. Three samples shall be removed from the12 and 6 o'clock position and from the 3 or 9 o'clock position.The testing of each sample shall be performed as required inAppendix B, and include:

— 1 transverse all weld metal tensile test.— 1 macro section taken adjacent to the all-weld metal ten-

sile test. The macro section shall be hardness tested(HV10) vertically through the weld centre line with inden-tations spaced 1.5 mm apart

— 1 set of Charpy V-notch test at weld centre line at in the samelocations as tested during WPQT. Test temperature shall be thesame as for qualification of the relevant welding procedure.

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406 If an ECA in not performed, the mechanical propertiesshall meet the specified minimum requirements.407 If an ECA is used as basis for establishing acceptancecriteria for pipeline girth welds (see Appendix A), fracturetoughness testing shall be performed with the same type ofspecimens and test conditions as for qualification of the rele-vant welding procedure, whenever:

— average impact test values are not within 80% of the aver-age value obtained during WPQT

— the transverse all weld metal yield stress is not within 90%of the value obtained during WPQT or the transverse allweld metal yield stress results in undermatching weldmetal strength

— the relevant mechanical properties of the weld metal doesnot meet the properties used as input in the ECA.

Chemical analysis408 For solid wire and metal powders the analysis shall rep-resent the product itself. For coated electrodes and cored wires,the analysis shall represent the weld metal, deposited accord-ing to EN 26847 (ISO 6847). The analysis shall include:

— all elements specified in the relevant classification stand-ard and the relevant data sheet, see 201

— the N content.

409 The chemical analysis shall be in accordance with thecomposition ranges stated in the Manufacturer's data sheets,see C201.

C 500 Shielding, backing and plasma gases501 The classification and designation and purity of shield-ing, backing and plasma gases shall be in compliance with EN439. 502 Gases shall be delivered with a certificate stating theclassification, designation, purity and dewpoint of the deliv-ered gas.503 The gas supply/distribution system shall be designedand maintained such that the purity and dewpoint is maintainedup to the point of use. 504 Shielding, backing and plasma gases shall be stored inthe containers in which they are supplied. Gases shall not beintermixed in their containers.505 If gas mixing unit systems are used, the delivered gascomposition shall be verified and regularly checked.

C 600 Handling and storage of welding consumables601 A detailed procedure for storage, handling, recyclingand re-baking of welding consumables to ensure that thehydrogen diffusible content of weld metal is maintained at lessthan 5 ml per 100 g weld metal shall be prepared. The proce-dure shall, as a minimum, shall be in accordance with the Man-ufacturer's recommendations. The procedure shall be reviewedand agreed prior to start of the production.602 The Manufacturer's recommendations may be adaptedfor conditions at the location of welding provided the follow-ing requirements are met:

— solid and flux cored wire shall be treated with care in orderto avoid contamination, moisture pick-up and rusting, andshall be stored under controlled dry conditions. Ranges oftemperature and relative humidity for storage shall bestated

— if vacuum packed low hydrogen SMAW welding consum-ables are not used, low hydrogen SMAW consumablesshall be stored, baked, handled and re-baked in accordancewith the Manufacturer’s recommendation. Re-bakingmore than once should not be permitted

— flux shall be delivered in moisture proof containers/bags.

The moisture proof integrity of bags shall be verified upondelivery and when retrieving bags for use. The flux shallonly be taken from undamaged containers/bags directlyinto a hopper or storage container

— the temperature ranges for heated hoppers, holding boxesand storage containers shall be in accordance with the fluxmanufacturer’s recommendations

— whenever recycling of flux is applied, the recycling proc-ess shall ensure a near constant ratio of new/recycled fluxand the ratio of new/recycled flux shall be suitable to pre-vent any detrimental degradation of the flux operatingcharacteristics, e.g. moisture pick-up, excessive build-upof fines and change of grain size balance.

D. Welding Procedures

D 100 General101 Detailed Welding Procedure Specifications shall be pre-pared for all welding covered by this Appendix. 102 All welding shall be based on welding consumables,welding processes and welding techniques proven to be suita-ble for the type of material and type of fabrication in question.

D 200 Previously qualified welding proceduresGeneral201 A qualified welding procedure of a particular manufac-turer is valid for welding only in workshops or sites under theoperational technical and quality control of that manufacturer.202 For welding procedures developed qualified and kept onfile for contingency situations such as hyperbaric welding pro-cedures intended for pipeline repair and other contingency sit-uations, the restrictions below shall not apply. Pipeline girth welds203 Previously qualified welding procedures shall not beused for:

— welding of girth welds when the SMYS of C-Mn linepipeis > 450 MPa

— welding of girth welds in clad or lined, duplex stainlesssteel or 13Cr martensitic stainless steel linepipe.

204 Excepts as limited by 203 above, a WPS for new produc-tion may be based on a previously qualified WPQR. The typeand extent of testing and test results for the previously quali-fied WPQR shall meet the requirements of this Appendix. AWPS for the new production shall be specified within theessential variables of this Appendix.205 For WPQRs older than 5 years the validity shall be doc-umented through production tests.Pipeline components206 Previously qualified welding procedures shall not beused for welding of steels with SMYS ≥ 450 MPa. 207A WPSfor new production may otherwise be based on a previouslyqualified WPQR. The type and extent of testing and test resultsfor the previously qualified WPQR shall meet the require-ments of this Appendix and a WPS for the new productionshall, based the previously qualified WPQR, be specifiedwithin the essential variables of this Appendix.207 For a WPQR where the actual qualification is more than5 years old, it shall be documented through production teststhat a WPS based on the qualifying WPQR have been capableof producing welds of acceptable quality over a period of time.Alternatively a limited confirmation welding may be per-formed to demonstrate that the WPS is workable and produc-ing welds of acceptable quality.

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D 300 Preliminary welding procedure specification301 A preliminary Welding Procedure Specification(pWPS) shall be prepared for each new welding procedurequalification. The pWPS shall contain the relevant informationrequired for making a weld for the intended application whenusing the applicable welding processes, including tack welds.

D 400 Welding procedure qualification record401 The Welding Procedure Qualification Record (WPQR)shall be a record of the materials, consumables, parameters andany heat treatment used during qualification welding and thesubsequent non-destructive, destructive and corrosion testresults. All essential variables used during qualification weld-ing that are relevant for the final application of the WPQR shallbe documented and the welding parameters recorded in rele-vant positions for each pass.

D 500 Welding procedure specification501 A Welding Procedure Specification (WPS) is a specifi-cation based on one or more accepted WPQRs. One or moreWPSs may be prepared based on the data of one or moreWPQRs provided the essential variables are kept within theacceptable limits and other requirements of this Appendix aremet. A WPS may include one or a combination of weldingprocesses, consumables or other variables. All limits andranges for the applicable essential variables for the welding tobe performed shall be stated in the WPS. 502 The WPS shall be submitted together with the refer-enced supporting WPQR(s) for review and acceptance prior tostart of production.

D 600 Welding procedure specification for repair weld-ing601 Repair welding procedure specifications shall be prepared,

based on WPQRs for the type of weld repair to be applied.

D 700 Contents of pWPS701 The pWPS shall contain the relevant informationrequired for the applicable welding processes, including anytack welds. A pWPS for production welding shall include theinformation given in Table C-1 and 702 through 705, as rele-vant for the welding to be performed.Additional requirements to pWPS for mechanised welding ofpipeline girth welds702 For mechanised welding of pipeline girth welds the fol-lowing additional information shall be included in the pWPS:

— control software (programme and/or software version)— list of pre-set welding parameters that can not be adjusted

by the welder— list of welding parameters that can be adjusted by the

welder. (“hot-key limits”)— minimum number of welders for each pass.

703 A pWPS for mechanised GMAW welding shall in addi-tion include:

— wire feed— oscillation width and frequency— side wall dwell time.

704 A pWPS for mechanised GTAW/PAW welding shall inaddition include:

— programmed arc voltage— wire feed including pulsing pattern and timing diagram— oscillation width and frequency— side wall dwell time— shielding gas timing diagrams and pulse pattern.

Table C-1 Contents of pWPSManufacturer Identification of manufacturerpWPS Identification of the pWPSWelding process Welding process and for multiple processes; the order of processes used

Manual, partly-mechanised, mechanised and automatic weldingWelding equipment Type and model of welding equipment. Number of wiresBase materials Material grade(s), supply condition, chemical composition and manufacturing process.

For steels with SMYS > 450 MPa; Steel supplier and For CRAs; UNS and PRE numbers. Material thickness and diam-eter

Material thickness of test piece. Nominal ID of pipe

Groove configuration Groove design/configuration; dimensions and tolerances of angles, root face, root gap and when applicable; diameters. Backing and backing material.

Alignment and tack welding Tack welding (removal of tack welds or integration of tack welds in the weld) Type of line-up clamp. Stage for removal of line-up clamp

Welding consumables Electrode or filler metal diameter or cross section area. Type, classification and trade name. Shielding, backing and plasma gases

Designation, classification and purity according to EN 439. Nominal composition of other gases and gas mix-tures. Gas flow rate

Electrical characteristics and pulsing data

Polarity. Type of current (AC, DC or pulsed current). Pulse welding details (machine settings and/or pro-gramme selection)

Arc Characteristics Spray arc, globular arc, pulsating arc or short circuiting arcWelding techniques Welding position according to ISO 6947. Welding direction. Stringer/weave beads. Sequence of deposition of

different consumables. Number of passes to be completed before cooling to below preheats temperature. Accelerated weld cooling (method and medium).For double sided welding: Sequence of sides welded first and last and number of passes welded from each side.For cellulose coated electrodes: Time lapse between completion of root pass and start of hot pass and number of welders on each side.

Preheating Method of preheat and minimum preheat temperature. Minimum initial temperature when preheat is not used.Interpass temperature Maximum and minimum interpass temperatureHeat input Heat input range for each passPost weld heat treatment Method, time and temperature for post heating for hydrogen release

Method of post weld heat treatment (holding time and heating and cooling rates)Specific for the SMAW welding process

Run-out length of electrode or travel speed

DET NORSKE VERITAS


Additional requirements to pWPS for repair welding705 A pWPS for repair welding shall in addition to therequirements applicable for a pWPS for production weldinginclude the following information:

— type of repair— method of removal of the defect, preparation and design of

the repair weld excavation— minimum repair depth and length— visual examination and NDT to be performed of the exca-

vated area according to Appendix D, Subsection B to con-firm complete removal of defect before welding as well asvisual examination and NDT of the final repaired weld.

— In cases when through thickness or partial thicknessrepeated repairs are permitted or agreed (see Table C-7)the location of additional Charpy V-notch tests, in additionto the tests required by Table C-4, shall be shown onsketches in the pWPS.

D 800 Essential variables for welding procedures801 A qualified welding procedure remains valid as long asthe essential variables are kept within the limits specified inTable C-2.802 For special welding processes as stated in A202 andwelding systems using these processes other essential parame-ters and acceptable variations need to be applied and shall besubject to agreement.803 The limits and ranges for essential variables for a WPSshall be based on the on documented records in one or moreWPQRs.804 The essential variables given in Table C-2 shall, whenapplicable, be supplemented with the requirements in 805through 814 below.Dissimilar material joint805 If two different materials are used in one test piece, theessential variables shall apply to each of the materials joined.A WPQR qualified for a dissimilar material joint will alsoqualify each material welded to itself, provided the applicableessential variables are complied with.

Multiple test pieces 806 A number of test pieces may be required for qualifyinga pWPS where the size of the test piece will not allow extrac-tion of test specimens in the correct locations according to Fig-ure 2. In such cases the maximum variation in heat input duringwelding of different the test pieces shall be within 25% of theheat input of the test piece welded with the lowest heat input.This will qualify welding with a heat input range between thelow and high heat input values, provided:

— hardness test specimens are taken from the test piecewelded with the lowest heat input

— impact test specimens are taken from the test piece weldedwith the highest heat input.

807 When it is intended to qualify a pWPS with a high andlow input in order to allow welding within this heat inputrange, the maximum difference in heat input shall not exceed30%. All required mechanical testing shall be performed ontest pieces welded with both high and low heat input.808 The minimum preheat or work piece temperature to bestated in the WPS shall not be below that of the test piece withthe recorded highest preheat.809 The maximum interpass temperature of any pass to bestated in the WPS shall not be higher than that of the test piecewith the recorded lowest interpass temperature +25oC or therecorded highest interpass temperature, whichever is thelower.Multiple filler metals810 When multiple filler metals are used in a test joint, thequalified thickness for each deposited filler metal shall bebetween 0.75 to 1.5 times the deposited thickness of that fillermaterial.Number of welders811 If welders have been working on opposite sides of a testpiece, the maximum difference in heat input between the weld-ers shall not exceed 15%. The allowable variation in heat inputshall be based on the average of the heat inputs used by thewelders.

Specific for the SAW weld-ing process

Number and configuration of wire electrodes. Flux, designation, manufacturer and trade name. Additional filler metal. Contact tip - work piece distance. Arc voltage range.

Specific for the FCAW weld-ing process

Mode of metal transfer (short circuiting, spray or globular transfer)

Specific for the GMAW welding process

Shielding and backing gas flow rate. Additional filler metal. Contact tip - work piece distance. Arc voltage range.

Specific for the GTAW welding process

Shielding and backing gas flow rate. Nozzle diameter. Diameter and codification of tungsten electrode (EN 26848). Hot or cold wire.

Specific for the PAW weld-ing process

Shielding, backing and plasma gas flow rate. Nozzle diameter. Type of torch. Contact tip - work piece distance. Hot or cold wire

Table C-1 Contents of pWPS (Continued)Manufacturer Identification of manufacturer

Table C-2 Essential variables for welding of pipeline girth weldsVariable Changes requiring re-qualification1 ManufacturerManufacturer a Any change in responsibility for operational, technical and quality control2 Welding processThe process(es) used a Any changeThe order of processes used b Any change when multiple processes are usedManual, partly-mechanised, mechanised or automatic weld-ing

c Any change between manual, partly-mechanised, mechanised and automatic welding

3 Welding equipmentWelding a Any change in make, type and model for partly-mechanised, mechanised and automatic weldingWelding equipment b Any change in type for manual weldingNumber of wires c Change from single wire to multiple wire system and vice versa

DET NORSKE VERITAS


4 Base materialsMaterial grade a A change from a lower to a higher strength grade but not vice versaSupply condition b A change in the supply condition (TMCP, Q/T or normalised)Steel supplier c For SMYS ≥ 450 MPa; a change in base material origin (steel mill) (pipeline girth welds only)Chemical composition d An increase in Pcm of more than 0.020, CE of more than 0.030 and C content of more than 0.02% for

C-Mn and low alloy steelManufacturing process e A change in manufacturing process (rolled, seamless, forged, cast)UNS numbers. f A change in the UNS number for CRAs5 Material thickness and diameterMaterial thickness (t = nominal thickness of test joint.)

a For non sour service:

— t < 25 mm: A change outside 0.75 t to 1.5 t— t > 25 mm: A change outside 0.75 t to 1.25 t

For sour service:

— A change outside the thickness interval 0.75 t to 1.25 tNominal ID of pipe b A change of pipe ID outside the range 0.5 ID to 2 ID 6 Groove configuration Groove design/configuration. a Any change in groove dimensions outside the tolerances specified in the agreed WPSBacking and backing material. b Addition or deletion of backing or change of backing material7 Alignment and tack weldingTack welding a Any change in removal of tack welds or integration of tack welds in the weld.Line-up clamp b Omission of a line-up clamp and a change between external and internal line-up clamp.Removal of line-up clamp c Any reduction in length of each section of root pass welded; the spacing of sections, number of sections

and percentage of circumference welded for external line-up clampd Any change in number of completed passes and length of passes for internal line-up clamp

Internal misalignment e Any increase for clad and lined pipe8 Welding consumablesElectrode or filler metal a Any change of diameter or cross section area

b Any change of type classification and brand (brand not applicable for bare wire)c Any use of a non tested welding consumables batch when batch testing is requiredd Any use of a welding consumables batch with a reduction in tensile or impact properties of more than –

10% from the batch used for WPQR when batch testing is not requiredFlux e Any change of type, classification and brand

f Any increase in the ratio of recycled to new flux9 Shielding, backing and plasma gasesGases according to EN 439 a Any change in designation, classification and purity according to EN 439Other gases and gas mixtures b Any change in nominal composition, purity and dew point.Oxygen content of backing gas c Any increaseShielding gas flow rate d For processes 131, 135 136, 137 and 141: Any change in flow rate beyond ± 10%10 Electrical characteristics and pulsing dataPolarity a Any change in polarityAC, DC or pulsed current b Any change in type of current and a change from normal to pulsed current and vice versa. Pulse frequency range in pulsed manual welding

c Any change in: Pulse frequency for background and peak current exceeding ± 10% and pulse duration range exceeding ± 10%.

11 Arc CharacteristicsMode of metal transfer a A change from spray arc, globular arc or pulsating arc to short circuiting arc and vice versa 12 Welding techniquesAngle of pipe axis to the hori-zontal

a A change of more than ± 15°from the position welded. The L045 position qualifies for all positions pro-vided all other essential variables are fulfilled

Welding direction b A change from upwards to downwards welding and vice versaStringer/weave c A change from stringer to weave of more than 3X electrode/wire diameter or vice versaSequence of deposition of dif-ferent consumables

d Any change in the sequence

Sequence of sides welded first and last (double sided welds)

e Any change in the sequence

Passes welded from each side f Change from single to multi pass welding and vice versa.Number of welders g Any decrease in number of welders for welding of root and hot pass for cellulose coated electrodes.Time lapse between completion of root pass and start of hot pass

h For cellulose coated electrodes: Any increase above maximum time qualified

Weld completion i Any reduction in the number of passes completed before cooling to below preheat temperature.

Table C-2 Essential variables for welding of pipeline girth welds (Continued)Variable Changes requiring re-qualification

DET NORSKE VERITAS


Additional essential variables for mechanised and automaticwelding of pipeline girth welds812 For mechanised and automatic welding of pipeline girthwelds the following additional essential variables apply:

— any change of control software— any change of pre-set parameters (parameters that can not

be adjusted by the welder) for automatic welding— any change in programmed parameters and their variation,

except that necessary variation in oscillation width forwelding of thinner/ heavier wall than used during qualifi-cation shall be allowed for mechanised GMAW, GTAWand PAW.

— any change in limits for parameters that can be adjusted bythe welder. (“hot-key limits”).

Essential variables for repair welding813 For repair welding the following essential variablesapply:

— the essential variables given in Table C-2— a change from internal to external repairs and vice versa

for pipeline girth welds— a change from multi pass to single pass repairs and vice

versa— a change from cold to thermal method for removal of the

defect but not vice versa— any increase in the depth of excavation for partial thick-

ness repairs.

Post weld heat treatment814 If CRA or clad welds are subject to solution annealingheat treatment after welding a slight variation in weldingparameters outside those in Table C-2, items 10 through 15may be agreed.

E. Qualification of Welding ProceduresE 100 General101 Qualification welding shall be performed based upon theaccepted pWPS, using the type of welding equipment to be usedduring production welding, and under conditions that are repre-sentative of the actual working environment for the work shop,site, or vessel where the production welding will be performed.Test joints102 The number of test joints shall be sufficient to obtain therequired number of specimens from the required locationsgiven in Figure 1 and Figure 2. Allowance for re-testing shouldbe considered when deciding the number of test joints to bewelded.103 The test joints for qualification welding shall be of suf-ficient size to give realistic restraint during welding.104 The base material selected for the qualification testingshould be representative of the upper range of the specifiedchemical composition for C-Mn and low alloy steels, and ofthe nominal range of the specified chemical composition forcorrosion resistant alloys.

Accelerated weld cooling j Any change in method and medium and any increase in maximum temperature of the weld at start of cooling.

13 PreheatingPreheat temperature a Any reduction. Initial temperature when pre-heat is not used

b Any reduction.

14 Interpass temperatureMaximum and minimum inter-pass temperature

a Any increase above 25°C for C-Mn and low alloy steel. Any increase for CRAs. Any reduction below the preheat temperature.

15 Heat inputHeat input range for each pass a For C-Mn and low alloy steels with SMYS ≤ 450 MPa in non sour service:

Any change exceeding ± 15% b For C-Mn and low alloy steels with SMYS > 450 MPa: Any change exceeding ± 10%c For CRAs: Any change exceeding ± 10%

16 Post weld heat treatmentPost heating; hydrogen release a Any reduction in the time and temperature and deletion but not addition of post heating.Post weld heat treatment b Addition or deletion of post weld heat treatment.

Any change in holding temperature exceeding ± 20°C.Any change in holding time and any change in heating and cooling rates outside ± 5%

17 Specific for the SAW welding processWire electrode configuration. a Each variant of process 12 (121 to125) shall be qualified separatelyFlux b Any change of type, classification and brand.Arc voltage range. c Any change beyond ± 10%18 Specific for the FCAW welding processMode of metal transfer a A change from short circuiting transfer to spray or globular transfer.

Qualification with spray or globular transfer qualifies both spray or globular transfer 19 Specific for the GMAW welding processArc voltage range a Any change beyond ± 10%20 Specific for the GTAW welding processDiameter and codification of tungsten electrode (EN 26848)

a Any change

Hot or cold wire. b A change from hot to cold wire and vice versa21 Specific for the PAW welding processHot or cold wire a A change from hot to cold wire and vice versa

Table C-2 Essential variables for welding of pipeline girth welds (Continued)Variable Changes requiring re-qualification

DET NORSKE VERITAS


105 The material thickness shall be the same for both pipes/components/plates to be welded, except to qualify joining oftwo base materials with unequal thickness and for fillet end T-joint test pieces.Qualification welding106 Certificates for materials and consumables, includingshielding, backing and plasma gases, shall be verified, andvalidity and traceability to the actual materials shall be estab-lished prior to start of qualification welding. The records fromqualification welding shall include all information needed toestablish a WPS for the intended application within the essen-tial variables and their allowable ranges. 107 The following requirements apply:

— the welding qualification test shall be representative forthe production welding with respect to welding positions,interpass temperature, application of preheat, heat conduc-tion, time between each layer, etc.

— if multiple welding arcs are combined in a single weldinghead the parameters for each welding arc shall be recorded

— the direction of plate rolling (when relevant) and the 12o’clock position (for fixed pipe positions) shall be markedon the test piece

— when more than one welding process or filler metal is usedto weld a test piece, the parameters used and the approxi-mate thickness of the weld metal deposited shall berecorded for each welding process and filler metal

— if tack welds are to be fused into the final joint during pro-duction welding, they shall be included when welding thetest piece

— heating of test pieces in addition to that generated by thewelding is not permitted, with the exception of heatingrequired to obtain and maintain the minimum preheat tem-perature and post heating stated in the pWPS

— backing gas oxygen content and the duration of backinggas application before, during and after welding shall berecorded

— each test piece shall be uniquely identified by hard stamp-ing or indelible marking adjacent to the weld and therecords made during test welding, non-destructive testingand mechanical testing shall be traceable to each testpiece.

Pipeline girth welds

— the welding qualification test shall be representative forthe production welding with respect to angle of pipe axis,interpass temperature, application of preheat, heat conduc-tion, time between each layer, etc.

— for girth welds in welded pipe in all positions, except 1G(PA) and 2G (PC), it is recommended that one of the pipesused for the welding procedure qualification test be fixedwith the longitudinal weld in the 6 or 12 o'clock position

— for welding of pipe with diameter ≥ 20” in fixed positionsthe weld circumference shall be divided in 90° sectorsaround the circumference, with one sector centred at the12 o’clock position. The welding parameters shall berecorded for each pass in each sector and for each weldingarc. The heat input for each sector may be recorded as theaverage value in the sector

— for welding of pipe with diameter < 20” the heat inputshall be recorded as the average value for each pass

— the release of external line-up clamps shall be simulatedduring qualification welding. Clamps shall normally notbe released until the completed sections of the root passcovers a minimum of 50% of the circumference with evenspacing. The length of each section, the spacing of the sec-tions, the number of sections welded and the percentage ofwelded sections of the circumference shall be recorded

— cooling of the test piece to below preheat temperature shallbe simulated during qualification welding for at least onetest piece. The number of passes completed before cooling

to below preheat temperature shall be recorded— accelerated cooling of the weld shall be performed during

qualification welding if accelerated weld cooling, e.g. forAUT will be performed in production. The coolingmethod and the weld temperature at the start of the coolingshall be recorded.

Cellulose covered electrodes108 If the use of cellulose covered electrodes has beenagreed, the following additional requirements shall apply:

— preheat shall be minimum 100°C— delay between completion of the root pass and the start of

depositing the hot pass shall be minimum 6 minutes— immediately upon completion of welding during welding

procedure qualification the test pieces shall be waterquenched as soon as the temperature of the test piece isbelow 300°C

— non destructive testing of the test piece shall be by Auto-mated Ultrasonic Testing (AUT) or Radiographic testingand Manual Ultrasonic Testing.

E 200 Repair welding procedures201 Repair welding shall be qualified by a separate weldrepair qualification test.202 Preheat for repair welding shall normally be minimum50°C above minimum specified preheat for production weld-ing.203 When a heat treated pipe or component is repaired bywelding, a new suitable heat treatment may be required to beincluded in the qualification of the weld repair procedure,depending on the effect of the weld repair on the properties andmicrostructure of the existing weld and base material.204 Qualification of repair welding procedures shall bemade by excavating a repair groove in an original weld weldedin accordance with a qualified welding procedure.205 The excavated groove shall be of sufficient length toobtain the required number of test specimens + 50 mm at eachend. Repeated repairs206 Repeated weld repairs shall be qualified separately, ifrepeated weld repairs are permitted or agreed.207 In case of repeated repairs, the test piece shall contain arepair weld of a qualified repaired original weld. For repeatedin-process root repair, single pass cap repair and/or single passroot sealing repairs the repair weld shall be removed prior tore-repair.Qualification welding208 The qualification test shall be made in a manner realisti-cally simulating the repair situation to be qualified.209 Qualification welding shall be performed in accordancewith E101 through E108.210 For pipeline girth welds the repair qualification weldingshall be performed in the overhead through vertical positions.211 For roll welding the length of the repair weld may becentred at the 12 o’clock location for external repairs and at the6 o’clock location for internal repairs, in which case repairwelding is qualified for repair welding in these locations only.

E 300 Qualification of longitudinal and girth butt welds welding procedures 301 Qualification of welding procedures for pipeline systemgirth welds and welds in pipeline components may be per-formed by any of the arc welding processes specified in A200.302 The WPS shall be qualified prior to start of any produc-tion welding.

DET NORSKE VERITAS


303 The type and number of destructive tests for weldingprocedure qualification are given in Table C-3, with methodsand acceptance criteria as specified in subsection F below.304 For pipeline girth welds exposed to strain ≥ 0.4% it may

be required to perform testing to determine the properties ofweld metal in the strained and aged condition after deforma-tion cycles and also at elevated temperature. See Sec.6 D207and Appendix A, Subsection G.

Qualification of repair welding procedures 305 Qualification of repair welding procedures for pipelinesystem girth welds and welds in pipeline components may beperformed by any of the arc welding processes specified inA200.306 The WPS for repair welding shall be qualified prior tostart of any production welding.307 The following types of repairs shall be qualified to theextent that such repairs are applicable and for pipe, also if thetype of repair is feasible for the size of pipe in question:

— through thickness repair— partial thickness repair— in-process root repair— single pass cap repair— single pass root sealing repair.

308 The type and number of destructive tests for qualifica-tion or repair welding procedure are given in Table C-4, withmethods and acceptance criteria as specified in subsection Fbelow.Repeated repairs309 If it has been agreed to permit through thickness or par-tial thickness repeated repairs (see Table C-7), and a HAZ isintroduced in the weld metal from the first repair, then addi-tional Charpy V-notch sets (in addition to the tests required byTable C-4) shall be located in the re-repair weld metal and inFL, FL+2 mm and FL+5 mm of the weld metal from the firstrepair and/or the base material as applicable and as shown inthe accepted pWPS, see E705.310 If it has been agreed to permit repeated in-process rootrepair, single pass cap repair and/or single pass root sealingrepair, see Table C-7, the extent of testing shall be as testsrequired by Table C-4.

Table C-3 Qualification of welding procedures for longitudinal and girth butt weldsTEST JOINT MINIMUM NUMBER OF EACH SPECIFIED TEST

Wall thickness (mm)

D (mm)

Transverse weld Tensile

Transver-seall-weld Tensile 1)

All-weld tensile 2)

Root bend 10)

Face bend 10)

Side-bend 10)

Charpy V-notch sets

4,5,6,7)

Macro and hardness 11)

Other tests12)

Fracture toughness

≤ 25 ≤ 300> 300

22

22

22

2 3)4 3)

2 3)4 3)

00

4 8)4 8)

22

13)13)

13) 13)

> 25 ≤ 300> 300

22

22

22

00

00

44

6 8,9)6 8,9)

22

13)13)

13,14)13,14)

Notes:

1) Transverse all weld tensile are required if an ECA is performed.2) All weld tensile tests are not required for OD ≤ 200 mm and not if transverse all-weld tests are performed.3) For welding processes GMAW and FCAW, side bend tests shall be performed instead of root and face bend tests.4) Impact testing is not required for t < 6 mm.5) Each Charpy V-notch set consists of 3 specimens.6) The notch shall be located in the weld metal, the fusion line (FL) sampling 50% of HAZ, FL+2 mm and FL+5 mm, see Appendix B,

Figure 3 through Figure 5.7) For double sided welds on C-Mn and low alloy steels, four additional sets of Charpy V-notch test specimens shall be sampled from the

weld metal, FL (sampling 50% of HAZ), FL+2 mm and FL+5 mm in the root area, see Appendix B Figure 5.8) If several welding processes or welding consumables are used, impact testing shall be carried out in the corresponding weld regions, if

the region tested cannot be considered representative for the complete weld.9) When the wall thickness exceeds 25 mm for single sided welds, two additional sets of Charpy V-notch test specimens shall be sampled

from the weld metal root and FL in the root area.10) Bend tests on clad/lined pipes shall be performed as side bend tests.11) For girth welds in welded pipe, one macro and hardness shall include an intersection between a longitudinal/girth weld.12) Requirements for corrosion tests, chemical analysis and microstructure examination are specified in F.13) Fracture toughness testing is only required when a generic or full ECA is performed for pipeline girth butt welds. Extent of testing shall

be in accordance with Appendix A.14) For nominal wall thickness above 50 mm in C-Mn and low alloy steels fracture toughness testing is required unless PWHT is performed.

DET NORSKE VERITAS


E 400 Qualification of welding procedures for corrosion resistant overlay weldingQualification of welding procedures401 Qualification of welding procedures for corrosion resist-ant overlay welding shall be performed with GMAW or pulsedGTAW. Other methods may be used subject to agreement. 402 The chemical composition of test pieces shall be repre-sentative for the production conditions.403 Qualification of weld overlay shall be performed on atest sample which is representative for the size and thicknessof the production base material. The minimum weld overlaythickness used for the production welding shall be used for thewelding procedure qualification test.404 The dimensions of, or the number of test pieces shall besufficient to obtain all required tests.

405 The test pieces used shall be relevant for the intendedapplication of the weld overlay:

— forging or casting for overlay welding of ring grooves— pipe with the overlay welding performed externally or

internally, or— plate or pipe with a prepared welding groove for qualifica-

tion of buttering and when the weld overlay strength is uti-lised in the design.

406 If a buffer layer will be used in production welding, itshall also be used in welding the test piece.407 The WPS shall be qualified prior to start of any produc-tion welding.408 The type and number of destructive tests for weldingprocedure qualification are given in Table C-5 with methodsand acceptance criteria specified in F below.

Table C-4 Qualification of repair welding procedures for longitudinal and girth butt welds TEST JOINT MINIMUM NUMBER OF EACH SPECIFIED TESTType of repair) Transverse

weld TensileTransverse

all-weld Tensile 1)

All-weld Tensile 2)

Root Bend

Face Bend

Side bend

Charpy V-notch sets

Macro and hardness

Other tests

Fracture toughness

Through thickness repair

1 1 1 1 3) 1 3) 2 4) 4, 5, 6,7, 8) 1 9) 10,11)

Partial thickness repair

1 1 1 1 3) 1 3) 2 4) 4) 1 9) 10,11)

In-process root repair

1 1 9)

Single pass cap repair

1 1 9)

Single pass root sealing repair

1 1 9)

Notes:

1) Transverse all weld tensile are only required if an ECA is performed.2) All weld tensile tests are not required for OD ≤ 200 mm and not if transverse all-weld tests are performed.3) 1 root and 1 face bend test for t < 25 mm4) For welding processes GMAW and FCAW, for clad/lined pipes and for all pipes when t > 25 mm, side bend tests shall be performed

instead of root and face bend tests.5) For partial penetration and through thickness repairs where a new HAZ is introduced in the original weld metal, Charpy V-notch sets of

3 specimens shall be located according to Appendix B, Figures 7 and 8. 6) The notch shall be located in the repair weld metal, the fusion line (FL) sampling 50% of HAZ, FL+2 mm and FL+5 mm of the base

material.7) If several welding processes or welding consumables are used, impact testing shall be carried out in the corresponding weld regions, if

the region tested cannot be considered representative for the complete weld.8) Requirements for corrosion tests, chemical analysis and microstructure examination are specified in Subsection F.9) Fracture toughness testing is only required when a generic or full ECA is performed for pipeline girth butt welds. Extent of testing shall

be in accordance with Appendix A.10) For nominal wall thickness above 50 mm in C-Mn and low alloy steels fracture toughness testing is required unless PWHT is performed

DET NORSKE VERITAS


Qualification of repair welding procedures409 Unless the production welding procedure can beapplied, the repair welding procedure shall be qualified. Weldrepair performed on weld overlay machined to the final thick-ness shall be separately qualified.410 The type and number of destructive tests for qualifica-tion of repair welding procedure are given in Table C-5. Incases when qualification is performed using a pipe, componentor plate with a prepared welding groove, and a new HAZ isintroduced in the original weld metal, additional Charpy V-notch sets shall be located according to Appendix B, Figures 7,and 8.

E 500 Qualification of procedures for Pin Brazing and Aluminothermic welding of anode leadsQualification of procedures

501 Attachment of anode leads shall be by pin brazing or alu-minothermic welding methods. Other methods may be usedsubject to agreement. Full details of the technique used andassociated equipment shall be available prior ton qualificationof procedures.502 The chemical composition of test pieces shall be repre-sentative for the production conditions and be selected in theupper range of the chemical composition.503 Qualification for brazing/welding of anode leads shallbe performed on test samples which is representative for thesize and thickness of the production base material and thenumber of test pieces shall be minimum 4 and sufficient toobtain all required tests.504 The WPS shall be qualified prior to start of any produc-tion.

505 The type and number of destructive tests for procedurequalification are given in Table C-6 with methods and accept-ance criteria specified in F below.

E 600 Qualification of welding procedures for temporary and permanent attachments and branch welding fittings to linepipeQualification of welding procedures601 Qualification of welding procedures for temporary andpermanent attachments and branch welding fittings to linepipemay be performed by any of the arc welding processes speci-fied in A200, but use of cellulose coated electrodes is not per-mitted.602 The WPS shall be qualified prior to start of any produc-tion welding.603 The type and number of destructive tests for weldingprocedure qualification are given in 604 to 614 with methodsand acceptance criteria as specified in subsection F.Longitudinal welds in doubler sleeves604 Longitudinal welds in doubler sleeves shall be madewith backing strips and qualified as required in E300 and TableC-3, but with the extent of testing modified to:

— transverse weld tensile — Charpy V-notch impact testing — macro and hardness testing,

Fillet welds in doubler sleeves and anode pads605 The fillet weld qualification test shall comprise two testpieces welded in the PD and PF plate positions to qualify thewelding procedure for welding in all positions. 606 The extent of testing for each test piece shall be 3 macroand hardness specimens taken from the start, end and middleof each test weld with methods and acceptance criteria as spec-ified in F.Branch welding fittings607 The branch fitting qualification test welds shall bewelded in the PF or PD pipe positions to qualify welding in allpositions.608 The extent of testing shall be 4 macro and hardness spec-imens taken from the 12, 3, 6 and 9 o’clock locations of eachtest weld.609 Charpy V-notch impact testing with the notch in theweld metal, FL, FL+2 mm and FL+5 mm using full size orreduced size specimens shall always be performed whenever

Table C-5 Qualification of corrosion resistant overlay welding proceduresTEST JOINT MINIMUM NUMBER OF EACH SPECIFIED TEST

Thickness of base material

Side bend Macro and hardness tests

Chemical Analy-sis

All-weld Ten-sile

Charpy V-notch Impact tests

Other tests

All 4 1) 1 1 2 2) 2,3,4,5) 6)

Notes:

1) Side bend specimens shall be taken transverse to the welding direction.2) Only required when the weld overlay strength is utilised in the design of the welded joint.3) Only required when the weld overlay is load bearing across the overlay/base material fusion line.4) Sets shall be tested with the notch in the overlay weld metal, Fl, and FL+2 mm and FL+5 mm in the base material. For t > 25 mm the

weld metal root and FL shall also be tested.5) If several welding processes or welding consumables are used, impact testing shall be carried out in the corresponding weld regions if

the region otherwise required to be tested cannot be considered representative for the complete weld.6) Requirements for corrosion tests and microstructure examination are specified in subsection F.

Table C-6 Qualification of Pin Brazing and Aluminothermic welding proceduresTEST JOINT MINIMUM NUMBER OF EACH SPECIFIED TEST 1)

Thickness of base material

Electrical resistance Mechanical strength Copper penetration 2) Hardness3) Pull test

All 4 4 4 4 4Notes

1) The number of tests refer to the total number of tests from all pieces.2) 2 test specimens shall the sectioned transverse to the anode lead and 2 test specimens parallel with the anode lead.3) The hardness tests shall be made on the specimens for copper penetration measurements.

DET NORSKE VERITAS


the material thickness allows. Charpy V-notch specimens shallbe taken from both test welds.Qualification of repair welding procedures for longitudinalwelds in doubler sleeves610 Repair welding procedures for longitudinal welds indoubler sleeves shall be qualified as required in E300 andTable C-4, but with the extent of testing modified according to604. Qualification of repair welding procedures for fillet welds611 Qualification welding shall be performed in the PD andPF plate positions. The extent of qualification of repair weld-ing procedures shall at as a minimum consist of:

— through thickness repair— single pass repair against the pipe material— single pass repair against the sleeve material.

612 Methods of testing and acceptance criteria shall be asspecified in F.Qualification of repair welding procedures for branch weldingfittings613 Qualification welding shall be performed in the PD andPF pipe positions. The extent of qualification of repair weldingprocedures shall at as a minimum consist of:

— through thickness repair— single pass cap repair against the fitting— single pass cap repair against the pipe.

614 Methods of testing and acceptance criteria shall be asspecified in F.

E 700 Qualification of welding procedures for struc-tural components701 Welding procedures for structural components, suppliedas a part of the pipeline systems, shall be qualified in accord-ance with ISO 15614-1. The requirements shall be appropriatefor the structural categorisation of the members and stresses inthe structure. The extent of tensile, hardness and impact testingand the testing conditions should be in compliance with thisAppendix.

E 800 Qualification of welding procedures for hyper-baric dry welding801 Requirements for qualification of welding proceduresfor hyperbaric dry welding are given in subsection I.

F. Examination and Testing for Welding Procedure Qualification

F 100 General101 All visual examination, non-destructive testing,mechanical testing and corrosion testing of test pieces shall beperformed in the as welded or post weld heat treated condition,

whatever is applicable for the final product.Visual examination and non-destructive testing102 Visual examination and non-destructive testing shall beperformed no earlier than 48 hours after the completion ofwelding of each test piece.103 If a test piece does not meet the acceptance criteria forvisual examination and NDT one further test piece shall bewelded and subjected to the same examination. If this addi-tional test piece does not meet the requirements, the WPQ isnot acceptable.Destructive testing104 The type and number of mechanical tests and micro-structure evaluations for qualification tests are given in E300to E700.105 Test specimens shall be taken from the positions shownin Figure 1 and Figure 2 for longitudinal welds and girth weldsrespectively.Re-testing106 A destructive test failing to meet the specified require-ments may be re-tested. The reason for the failure shall beinvestigated and reported before any re-testing is performed. Ifthe investigation reveals that the test results are influenced byimproper sampling, machining, preparation, treatment or test-ing, then the test sample and specimen (as relevant) shall bereplaced by a correctly prepared sample or specimen and a newtest performed.107 A destructive test failing to meet the specified require-ments shall be rejected if the reason for failure can not berelated to improper sampling, machining, preparation, treat-ment or testing of specimens.108 Re-testing of a test failing to meet the specified require-ments should only be performed subject to agreement. This re-testing shall consist of at least two further test specimens/setsof test specimens. If both re-tests meet the requirements, thetest may be regarded as acceptable. All test results, includingthe failed tests, shall be reported.109 If there are single hardness values in the different testzones (weld metal, HAZ, base material) that do not meet therequirement, retesting shall be carried out on the reverse sideof the tested specimen or after t grinding and re-preparation ofthe tested surface. None of these additional hardness valuesshall exceed the maximum value.110 Specific for Charpy V-notch impact testing the follow-ing requirements apply:

— if two out of three test specimens in any set fail or the aver-age requirement is not met, the WPQ is not acceptable.

— if more than one set of specimens includes a failed speci-men the WPQ is not acceptable.

— retest may, subject to agreement, be performed with twotest specimen sets. All re-tested specimens shall meet thespecified minimum average toughness.

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Figure 1 Welding procedure qualification test - sampling of test specimensfor longitudinal butt welds.

Note: The indicated location of the test specimens are not required for qualifi-cation of welding in the PA (1G) and PC (2G) positions, where sampling posi-tions are optional.

Figure 2 Welding procedure qualification test - sampling of test specimensfor girth butt welds.

Note 1: For pipeline girth welds, if applicable, one macro and hardness speci-men shall include a pipe longitudinal seam weld.

Note 2: The indicated location of the test specimens are not required for qual-ification of welding in the PA (1G rotated) where sampling positions areoptional.

F 200 Visual examination and non-destructive testing requirements201 Each test weld shall undergo 100% visual examinationand 100% ultrasonic and 100% radiographic testing and 100%magnetic particle or liquid penetrant testing. Testing shall be inaccordance with Appendix D, subsection B.202 Acceptance criteria for visual examination and non-destructive testing shall be in accordance with Appendix D,B900 for welds exposed to strains < 0.4%. For welds exposedto strains ≥ 0.4%, the acceptance criteria shall be as for the pro-duction welding or according to Appendix D, B900, whicheveris the more stringent.203 Weld overlay shall be non-destructively tested accord-ing to Appendix D, C300 with acceptance criteria according toAppendix D, C600. The surface and weld thickness shall berepresentative for the production welding, i.e. after machiningof the overlay thickness or the thickness representative for thethickness on the finished component.

F 300 Testing of butt welds301 All testing shall be performed in accordance withAppendix B.Transverse weld tensile testing302 The fracture shall not be located in the weld metal. Theultimate tensile strength shall be at least equal to the SMTS forthe base material. When different material grades are joined,the ultimate tensile strength of the joint shall be at least equalto the SMTS for the lower grade.All-weld tensile testing303 For longitudinal welds and girth welds exposed to strainεl,nom <0.4% and where no ECA is performed, the upper yieldor the Rt0.5 of the deposited weld metal should be at least be 80MPa above SMYS of the base material and the elongation notless than 18%. If two grades are joined the requirement appliesto the lower strength material.Transverse all-weld tensile testing304 For pipeline girth welds where generic ECA acceptancecriteria. (see Appendix A, HOLD) are applied, the upper yieldor the Rt0.5 of the deposited weld metal shall at least match theupper maximum of the permitted yield stress of the base mate-rial. The elongation shall not be less than 18%.When differentmaterial grades are joined, the yield stress requirementsapplies to the lower grade.305 For pipeline girth welds exposed to strain εl,nom ≥ 0.4%and where full ECA acceptance criteria shall be applied, theupper yield or the Rt0.5 of the deposited weld metal shall atleast match the upper maximum of the permitted yield stress ofthe base material or the assumptions made during design and/or the ECA. The elongation shall not be less than 18%.Bend testing306 The end tests shall not disclose any open defects in anydirection exceeding 3 mm. Minor ductile tears less than 6 mm,originating at the specimen edge may be disregarded if notassociated with obvious defects.Charpy V-notch impact testing307 The average and single Charpy V-notch toughness ateach position shall not be less than specified for the base mate-rial in the transverse direction (KVT values). Requirement forfracture arrest properties does not apply.C-Mn and low alloy steels shall meet the requirements givenin Sec.7 B400.Duplex and martensitic stainless steels shall meet the require-ments given in Sec.7 C400.The C-Mn steel backing material in clad and lined linepipeshall meet the requirements given in Sec.7 B400.

12 3

4

6 5

7

3

5

5

6 3 2

1 2

3

4

7

1 2

5

5

8

6

7

1: Cross weld tensile specimens 2: All weld tensile specimens 3: Bend test specimens 4: Impact test specimens 5: Macro and hardness test specimens 6: Corrosion test specimens 7: Micro examination and chemical analysis 8: Fracture toughness specimens

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308 When different steel grades are joined the requiredimpact tests shall be performed on both sides of the weld. Theweld metal shall meet the more stringent energy requirement.Macro section309 The macro section shall be documented by photographs(magnification of at least 5X).310 The macro section shall show a sound weld mergingsmoothly into the base material and meeting Quality level C ofISO 5817.311 For girth welds in welded pipe, one macro section shallinclude a longitudinal weld.Hardness testing312 The maximum hardness in the base material, HAZ andweld metal is:

— 325 HV10 for C-Mn and low alloy steels in non-sour serv-ice

— 250 HV10 for C-Mn and low alloy steels in sour service(for weld caps not exposed to the sour service media, max-imum of hardness of 275 HV10 may be agreed for basematerial thickness > 12 mm)

— 325 HV10 for 13Cr martensitic stainless steels— 350 HV10 for duplex stainless steels— 325 HV10 for clad or lined material in non-sour service.

For clad or lined materials in sour service special considera-tions are required, see ISO 15156.313 For girth welds in welded pipe, one hardness test speci-men shall include a longitudinal weld.Corrosion testing314 Sulphide stress cracking testing (SSC) is only requiredfor C-Mn and low alloy steels with SMYS > 450 MPa, 13Crmartensitic stainless steels and other materials not listed forsour service in ISO 15156. Acceptance criteria shall be according to ISO 15156.315 Pitting corrosion test according to ASTM G48 is onlyrequired for 25Cr duplex stainless steel. (see Sec.5 E302.). Themaximum weight loss shall be 4.0 g/m2 when tested at 40°Cfor 24 hours.Microstructure examination316 Welds in duplex stainless steel materials, CRA materialsand clad/lined materials shall be subject to microstructureexamination. The material shall be essentially free from grainboundary carbides, nitrides and intermetallic phases. Essen-tially free implies that occasional strings of detrimental phasesalong the centreline of the base material is acceptable giventhat the phase content within one field of vision (at 400X mag-nification) is < 1.0% (max. 0.5% intermetallic phases).For duplex steel the ferrite content of the weld metal and HAZshall be within the range 35-65%.The ferrite content of austenitic stainless steel weld depositshall be within the range 5-13%.Micro cracking at the fusion line is not permitted.Chemical analysis317 For welds in clad or lined materials a chemical analysisshall be performed. The analysis shall be representative of theCRA composition at a point at the centreline of the root pass0.5 mm below the surface. The chemical composition shall bewithin the specification limits according to the UNS numberfor the specified cladding/lining material or, if the weld metalis of a different composition than the cladding/liner, within thelimits of chemical composition specified for the welding con-sumable.Fracture toughness testing318 For girth welds fracture toughness testing shall per-

formed when acceptance criteria are established by an ECA.The extent of testing shall be in accordance with Appendix A. 319 For nominal wall thickness above 50 mm in C-Mn andlow alloy steels fracture toughness testing is required unlessPWHT is performed.

F 400 Testing of weld overlay401 When the weld overlay is not contributing to strength,tensile testing and Charpy V-notch testing of the weld overlaymaterial are not required. When the weld overlay strength isconsidered as a part of the design, such mechanical testing ofthe weld overlay material is required.402 The base material shall retain the minimum specifiedmechanical properties after any post weld heat treatment. Thebase material properties in the post weld heat treated conditionshall then be documented by additional testing and recorded asa part of the welding procedure qualification.403 The testing in 404 through 408 shall, as a minimum, beperformed when the overlay material is not considered as partof the design and when the base material has not been affectedby any post weld heat treatment.Bend testing of weld overlay404 The bend testing shall be performed in accordance withAppendix B, A614. The bend tests shall disclose no defectsexceeding 1.6 mm. Minor ductile tears less than 3 mm, origi-nating at the specimen edge may be disregarded if not associ-ated with obvious defects.Macro examination of weld overlay405 The macro sections shall be documented by photographs(magnification of at least 5X). The macro section shall show asound weld merging smoothly into the base material and meet-ing Quality level C of ISO 5817.Hardness testing of weld overlay406 The maximum hardness for base material and HAZ shallnot exceed the limits given in F312 above as applicable for theintended service and type of material. The maximum hardnessfor the overlay material shall not exceed any limit given in ISO15156 for sour service, unless otherwise agreed.Chemical analysis of weld overlay407 The chemical composition shall be obtained in accord-ance with Appendix B. Specimens for chemical analysis shalleither be performed directly on the as welded or machined sur-face or by taking specimen or filings/chips from:

— the as welded surface— a machined surface— from a horizontal drilled cavity.

The location for the chemical analysis shall be considered asthe minimum qualified thickness to be left after any machiningof the corrosion resistant weld overlay. 408 The chemical composition of overlay shall be shall bewithin the specification limits according to the UNS for thespecified overlay material. The iron content of alloy UNSN06625 overlay shall be < 10%. Microstructure examination of weld overlay409 The surface to be used for microstructure examinationshall be representative of a weld overlay thickness of 3 mm orthe minimum overlay thickness specified for the finishedmachined component, whichever is less. Microstructure exam-ination shall be performed after any final heat treatment.410 Metallographic examination at a magnification of 400X ofthe CRA weld metal HAZ and the base material shall be per-formed. Micro cracking at the CRA to the C-Mn/low alloy steelinterface is not permitted. The material shall be essentially freefrom grain boundary carbides, nitrides and inter-metallic phasesin the final condition (as-welded or heat treated as applicable).

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411 The ferrite content of austenitic stainless steel weldoverlay deposit shall be within the range 5-13%. The ferritecontent of duplex stainless steel weld overlay in the weld metaland HAZ shall be within the range 35-65%.All-weld tensile testing of load bearing weld overlay412 All-weld tensile testing shall be performed in accord-ance with Appendix B A400.413 The yield stress and ultimate tensile strength of the welddeposit shall be at least equal to the material tensile propertiesused in the design.Charpy V-notch impact testing of load bearing weld overlay414 When the weld overlay material is designed to transferthe load across the base material/weld overlay fusion line,impact testing of the weld overlay and HAZ shall be performed(i.e. when the overlay is a part of a butt joint or acts as a tran-sition between a corrosion resistant alloy and a C-Mn/lowalloy steel).415 Testing shall be with the notch in the overlay weldmetal, FL, FL+2 mm and FL+5 mm in the base material. Fort > 25 mm the weld metal root and FL shall also be tested.416 Where several welding processes or welding consuma-bles are used, impact testing shall be carried out in the corre-sponding weld regions if the region otherwise required to betested cannot be considered representative for the completeweld.417 The average and single Charpy V-notch toughness ateach position shall not be less than specified for the base mate-rial. When different steel grades are joined, a series of impacttests shall be considered in the HAZ on each side of the joint.The weld metal shall meet the more stringent energy require-ment.Corrosion testing of weld overlay418 Corrosion testing and microstructure examination ofstainless steel and nickel base weld overlay materials shall beconsidered.

F 500 Testing of pin brazing and aluminothermic welds Electrical resistance501 The electrical resistance of each test weld/brazing shallnot exceed 0.1.Mechanical strength502 Each test weld/brazing shall be securely fixed and testedwith a sharp blow from a 1.0 kg hammer. The weld/brazingshall withstand the hammer blow and remain firmly attachedto the base material and show no sign of tearing or cracking.Copper penetration503 2 test specimens shall the sectioned transverse to theanode lead and 2 test specimens parallel with the anode lead.The fusion line of the weld/brazing shall at any point not bemore than 1.0 mm below the base material surface. Intergran-ular copper penetration of the base material shall not at anypoint extend beyond 0.5 mm from the fusion line.Hardness504 HV10 hardness tests shall be made on each of the spec-imens for copper penetration measurements. 505 The maximum hardness shall not exceed the limits givenin F312 as applicable for the intended service and type of mate-rial.Pull test506 The specimen shall break in the cable.

F 600 Testing of welds for temporary and permanent attachments and branch outlet fittings to linepipe601 Welds shall be tested to the extent required in E600 and

meet the relevant requirements given in F300 above.

G. Welding and PWHT RequirementsG 100 General101 All welding shall be performed using the type of weld-ing equipment and under the conditions that are representativefor the working environment during procedure qualificationwelding.102 Pre-qualification testing shall be performed for weldingsystems where the Contractor has limited previous experience,or where the system will be used under new conditions. Allwelding equipment shall be maintained in good condition inorder to ensure the quality of the weldment.103 All welding shall be performed under controlled condi-tions with adequate protection from detrimental environmentalinfluence such as humidity, dust, draught and large tempera-ture variations.104 All instruments shall have valid calibration certificatesand the adequacy of any control software shall be documented.105 Welding and welding supervision shall be carried out bypersonnel qualified in accordance with the requirements givenin B200.

G 200 Production welding, general requirements201 All welding shall be carried out strictly in accordancewith the accepted welding procedure specification and therequirements in this subsection. If any parameter is changedoutside the limits of the essential variables, the welding proce-dure shall be re-specified and re-qualified. Essential variablesand variation limits are specified in D800.202 The preparation of bevel faces shall be performed byagreed methods. The final groove configuration shall be asspecified in the WPS and within the tolerances in the WPS. 203 After cutting of pipe or plate material for new bevelpreparation, a new lamination check by ultrasonic and mag-netic particle/dye penetrant testing is normally required. Pro-vided it can be demonstrated that the cut has been made insidea zone where a lamination check was performed at the plate/pipe mill the check may be omitted. Procedures for ultrasonicand magnetic particle/dye penetrant testing and acceptance cri-teria shall be in accordance with Appendix D.204 For welding processes using shielding, backing andplasma gases, the gas classification moisture content and dewpoint shall be checked prior to start of welding. Gases in dam-aged containers or of questionable composition, purity anddew point shall not be used. All gas supply lines shall beinspected for damage on a daily basis. All gas supply linesshall be purged before the welding is started.205 The weld bevel shall be free from moisture, oil, grease,rust, carbonised material, coating etc., which may affect theweld quality. 206 The alignment of the abutting ends shall be adjusted tominimise misalignment. Misalignment shall not exceed thetolerances in the WPS.207 The weld area shall be heated to the minimum preheattemperature specified in the WPS. Pre-heating shall also beperformed whenever moisture is present or may condense inthe weld area and/or when the ambient temperature or materialtemperature is below 5°C. Welding below 20°C shall not beperformed unless otherwise agreed.208 If applicable pre-heating shall be applied prior to anywelding, including tack welding. The pre-heating temperatureshall be measured at a distance of minimum 75 mm from theedges of the groove at the opposite side of the heating sourcewhen practically possible. If this is not possible, the adequacy

DET NORSKE VERITAS


of the performed measurement shall be demonstrated.209 Tack welding shall only be performed if qualified duringwelding procedure qualification. The minimum tack weldlength is 2t or 100 mm, whichever is larger. Temporary tackwelds using bridging or bullets shall only be performed usingmaterials equivalent to the base material and using a WPSbased on a qualified welding procedure. All such tack weldsand any spacer wedges shall be removed from the final weld-ment. Tack welds to be fused into the weld shall be made in theweld groove only and the ends of the tack welds shall havetheir ends ground and feathered and examined for cracks by anadequate NDT method. Defective tack welds shall be removedor repaired prior to production welding.210 Removal of tack welds shall be by grinding and cleaningfollowed by examination of the ground area by visual inspec-tion. Where temporary tack welds are removed, the bevel con-figuration and root gaps specified in the WPS shall bemaintained for the subsequent pass and the groove visuallyinspected prior to resuming welding of the root pass.211 The interpass temperature shall be measured at the edgeof the groove immediately prior to starting the following pass.212 Earth connections shall be securely attached to avoid arcburns and excessive resistance heating. Welding of earth con-nections to the work piece is not permitted.213 The number of welders and the weld sequence shall beselected in order to cause minimum distortion of the pipelineor the components.214 Start and stop points shall be distributed over a length ofweld and not "stacked" in the same area.215 Welding arcs shall be struck on the fusion faces only.Weld repair of base material affected by stray arcs is not per-mitted.216 Arc burns shall be repaired by mechanical removal ofaffected base material followed by NDT to verify absence ofcracks and ultrasonic wall thickness measurements to verifythat the remaining material thickness is not below the mini-mum allowed.

217 Surface slag clusters, surface porosity and high pointsshall be removed by grinding and the weld visually inspectedprior to deposition of the next weld pass.218 After weld completion, all spatter, scales, slag, porosity,irregularities and extraneous matter on the weld and the adja-cent area shall be removed. The cleaned area shall be sufficientfor the subsequent NDT. Peening is not permitted.219 Welding shall not be interrupted before the joint has suf-ficient strength to avoid plastic yielding and cracking duringhandling. Prior to restart after an interruption, preheating to theminimum interpass temperature of the pass in question shall beapplied.220 Welds shall only be left un-completed if unavoidable.Welding of fittings shall always be completed without inter-ruption. If welding is interrupted due to production restraints,the minimum number of passes specified in the WPS shall becompleted before stopping welding. If the WPS does not spec-ify a minimum number of passes, at least 3 passes or half thethickness of the joint should be completed before the weldingis interrupted. When interruption of welding is imposed byproduction restraints interrupted welds shall be wrapped in dryinsulating material and allowed to cool in a slow and uniformmanner. Before restarting welding of an interrupted weld thejoint shall be reheated to the interpass temperature recordedduring qualification of the welding procedure.221 Maximum root gap for fillet welds should be 2 mm.Where the root gap is > 2 mm but ≤ 5 mm, this shall be com-pensated by increasing the throat thickness on the fillet weld by0.7 mm for each mm beyond 2 mm gap. Welding of fillet weldswith root gap > 5 mm is subject to repair based on an agreedprocedure.

G 300 Repair welding, general requirements301 The allowable repairs and re-repairs are given in TableC-7 and are limited to one repair in the same area. Repeatedrepairs shall be subject to agreement and are limited to onerepeated repair of a previously repaired area.

302 Repair welding procedures shall be qualified to theextent that such repairs are feasible and applicable for therepair situation in question. Qualification of repair weldingprocedures denoted “if agreed“, need only be done if perform-ing such repairs is agreed and are feasible for the repair situa-tion in question.303 Cellulosic coated electrodes shall not be used for repairwelding.304 Repair welding of cracks is not permitted unless thecause of cracking by technical evaluation has been established

not to be a systematic welding error (cracks in the weld is causefor rejection).305 Defects in the base material shall be repaired by grindingonly.306 Defective welds that cannot be repaired with grindingonly may be repaired locally by welding. Repair welding shallbe performed in accordance with a qualified repair weldingprocedure. For welding processes applying large weld pools,e.g. multi-arc welding systems, any unintended arc-stops shallbe considered as defects.

Table C-7 Types of weld repairsType of repair Type of material

C-Mn and low alloy steel

13Cr MSS Clad/lined CRA/Duplex SS

Through thickness repair Permitted Permitted If agreed If agreedPartial thickness repair Permitted Permitted Permitted PermittedIn-process root repair Permitted Permitted Permitted PermittedSingle pass cap repair Permitted Permitted Permitted PermittedSingle pass root sealing repair If agreed If agreed If agreed If agreedThrough thickness repeated repair If agreed Not permitted Not permitted Not permittedPartial thickness repeated repair If agreed Not permitted Not permitted Not permittedIn-process root repeated repair Not permitted Not permitted Not permitted Not permittedSingle pass cap repeated repair Not permitted Not permitted Not permitted Not permittedSingle pass root sealing repeated repair Not permitted Not permitted Not permitted Not permittedNote

1) Provided solution annealing is performed after welding, all repairs are allowed.

DET NORSKE VERITAS


307 Weld seams may only be repaired twice in the samearea. Repeated repairs of the root in single sided welds are notpermitted, unless specifically qualified and accepted in eachcase. Weld repairs shall be ground to merge smoothly into theoriginal weld contour.308 Repairs of the root pass in a single-sided joint for mate-rial meeting sour service requirements shall be carried outunder constant supervision.309 A local weld repair shall be at least 50 mm long or 4times the material thickness, whichever is longest. If the lengthat the bottom of the excavation is 50 mm this may be ok if thetaper required in 310 gives adequate access for welding.310 The excavated portion of the weld shall be large enoughto ensure complete removal of the defect, and the ends andsides of the excavation shall have a gradual taper from the bot-tom of the excavation to the surface. Defects can be removedby grinding, machining or air-arc gouging. Air-arc gougingshall be controlled by a documented procedure including theallowed variables according to AWS C5.3. If air-arc gougingis used, the last 3 mm through the root of the weld shall beremoved by mechanical means and the whole excavated areashall be ground to remove any carbon enriched zones. Thewidth and the profile of the excavation shall be sufficient toensure adequate access for re-welding. Complete removal ofthe defect shall be confirmed by magnetic particle testing, orby dye penetrant testing for non ferromagnetic materials.Residuals from the NDT shall be removed prior to re-welding.311 Weld repairs shall be ground to merge smoothly into theoriginal weld contour.312 Repair by welding after final heat treatment is not per-mitted.

G 400 Post weld heat treatment401 Welds shall be subjected to PWHT as specified in thepWPS or WPS and to a documented procedure.402 Post weld heat treatment shall be performed for weldedjoints of C-Mn and low alloy steel having a nominal wall thick-ness above 50 mm, unless fracture toughness testing showsacceptable values in the as welded condition. In cases wherethe minimum design temperature is less than -10°C, the thick-ness limit shall be specially determined.403 If post weld heat treatment is used to obtain adequateresistance of welded joints against sulphide stress cracking,this shall be performed for all thicknesses.404 Whenever possible, PWHT shall be carried out by plac-ing the welded assembly in an enclosed furnace. Requirementsto PWHT in an enclosed furnace are given in Sec.8 D500.405 If PWHT in an enclosed furnace is not practical, localPWHT shall be performed by means of electric resistance heat-ing mats or other methods as agreed or specified. The PWHTshall cover a band over the entire length of the weld. The bandshall be centred on the weld and the width of the heated bandshall not be less than 5 times the thickness of the thicker com-ponent in the assembly.406 Unless otherwise agreed temperatures shall be measuredby thermocouples in effective contact with the material and ata number of locations to monitor that the whole length of theweld is heated within the specified temperature range. In addi-tion temperature measurements shall be made to confirm thatundesired temperature gradients do not occur.407 Insulation shall be provided if necessary to ensure thatthe temperature of the weld and the HAZ is not less than thetemperature specified in the pWPS or WPS. The width of theinsulation shall be sufficient to ensure that the material temper-ature at the edge of the insulation is less than 300°C.408 The rate of heating for C-Mn and low alloy steels above300°C shall not exceed 5500/t °C · h1 and the rate of cooling

while above 300°C shall not exceed 6875/t °C · h1 with texpressed in mm. During heating and cooling at temperaturesabove 300°C the temperature variation shall not exceed 35°Cin any weld length of 1000 mm.The holding time at temperature should be minimum 30 min-utes +2.5 minutes per mm thickness. Below 300°C the coolingmay take place in still air.409 The holding temperature for C-Mn low alloy steels shallnormally be within 580°C to 620°C unless otherwise specifiedor recommended by the material/welding consumable sup-plier. The maximum PWHT temperature for quenched andtempered low alloy steels shall be 25°C less than the temperingtemperature of the material as stated in the material certificate.410 The heat treatment temperature cycle charts shall beavailable for verification if requested.411 For materials other than C-Mn and low alloy steels thePWHT heating and cooling rates, temperature, and holdingtime shall be as recommended by the material manufacturer.

G 500 Welding of pipeline girth weldsProduction welding501 These requirements apply to welding of girth welds inpipelines regardless of whether the welds are made onboard alaying vessel or at other locations, onshore or offshore. Girthwelds in expansion loops, pipe strings for reeling or towingand tie-in welds are considered as pipeline girth welds. 502 The type of welding equipment and the welding proce-dure shall be qualified prior to installation welding.503 In addition to the requirements given in G100 and G200the requirements below shall apply for production welding ofpipeline girth welds.504 Bevels shall be prepared by machining. Bevelling bythermal cutting shall be performed only when bevelling bymachining is not feasible e.g. for tie-in and similar situations.Bevels prepared by thermal cutting shall be dressed to obtainthe final configuration. The bevelling operator shall check thebevel configuration for compliance with suitable tools orgauges at regular intervals.505 When welds are to be examined by manual or automatedultrasonic testing, reference marking shall be made on bothsides of the joint as a scribed line around the pipe circumfer-ence. The reference marking shall be at a uniform and knowndistance from the root face of the bevel preparation. The dis-tance from the root face and the tolerances shall be established,See also Appendix E, B108 and B1000.506 All pipes shall be cleaned on the inside to remove anyand all foreign matters and deposits in accordance with a doc-umented procedure.507 For S-lay welding, longitudinal welds shall be located inthe top quadrant.508 The longitudinal welds shall be staggered at least 50mm. Girth welds shall be separated at least 1.5 pipe diametersor 500 mm, whichever is larger. Whenever possible girthwelds shall be separated by the maximum possible distance.509 Excessive misalignment may be corrected by hydraulicor screw type clamps. Hammering or heating for correction ofmisalignment is not permitted. Root gaps shall be even aroundthe circumference. The final fit-up shall be checked withspacer tools prior to engaging line-up clamps or tack welding.510 Correction of angular misalignment of the pipe axis bymitre welds is not permitted.511 Power operated internal line-up clamps shall be usedwhenever possible. Internal line-up clamps shall not be released unless the pipe isfully supported on each side of the joint.

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External line-up clamps shall not be removed unless the pipe isfully supported on each side of the joint and not before thecompleted parts of the root pass meet the requirements tolength of each section, the spacing of the sections, the numberof sections and the percentage of circumference required bythe WPS.512 Line-up clamps should not be removed before the firsttwo passes are completed513 If cables are present inside the pipeline, e.g. buckledetector cables, and radiographic testing is used, the starts andstops shall be made away from the six o’clock position to avoidmasking of starts and stops on radiographs.514 Copper contact tips and backing strips shall be checkedon a regular basis for damage that could introduce copper con-tamination in welds. Damaged contact tips and backing stripsshall be replaced.515 Procedures shall be established for pre-cleaning, inprocess cleaning and post cleaning of welds.516 If a pipe is to be cut for any reason, the cut shall be at aminimum distance of 25 mm from the weld toe.517 The root and the first filler pass shall be completed at thefirst welding station before moving the pipe. Moving the pipeat an earlier stage may be permitted if an analysis demonstratesthat the pipe can be moved without any risk of introducingdamage to the deposited weld metal. See Sec.10 A706.Repair welding518 In addition to the requirements given in G300 the belowrequirements shall apply for repair welding of pipeline girthwelds.519 For through thickness repairs where the defects to berepaired are less than 150 mm apart, they shall be consideredand repaired as one continuous defect.520 The location of repair of burn through and other in proc-ess root repairs shall be marked on the outside of the pipe toinform NDT personnel that a root repair has been made.521 If the pipe and the area of repair is not exposed to bend-ing and/or axial stresses at the repair location the length of arepair excavation shall not exceed 30% of the pipe circumfer-ence for partial penetration repairs and 20% of the pipe circum-ference for through thickness repairs.522 Long defects may require repair in several steps to avoidyielding and cracking. The maximum length of allowablerepair steps shall be calculated based on the maximum stressespresent in the joint during the repair operation, and shall notexceed 80% of SMYS.523 If the repair is performed at a location where the pipeand the area of repair is exposed to bending and axial stressesthe allowable length of the repair excavation shall be deter-mined by calculations, see Sec.10 A704 and 705.524 If repairs can not be executed according to the require-ments above, or are not performed successfully, the weld shallbe cut out.525 Full records of all repairs, including in-process rootrepairs, shall be maintained.Production tests526 Production tests (see Sec.10 A900) shall be performed ina manner which, as far as possible, reproduces the actual weld-ing, and covers the welding of a sufficient large pipe section inthe relevant position. Production welds cut out due to NDTfailure may be used.

G 600 Welding and PWHT of pipeline components601 The Manufacturer shall be capable of producing pipelinecomponents of the required quality.602 Welding and PWHT shall be performed in accordance

with G100 through G400 above.603 Production tests shall be performed in a manner which,as far as possible, reproduces the actual welding, and coversthe welding of a sufficient large test section in the relevantposition. Production welds cut out due to NDT failure may beused.

H. Material and Process Specific RequirementsH 100 Internally clad/lined carbon steel and duplex stainless steelWPS101 In addition to the applicable data given in Table C-1 theWPS shall specify the following, as recorded during the weld-ing procedure qualification:

— the minimum time period of backing gas application priorto start of welding

— the minimum time period of backing gas application dur-ing welding

— the minimum time period of backing gas application after— description of the back-purge dam type and method.

Essential variables102 The following essential variables shall apply in additionto those in Table C-2:

— any reduction of the time of backing gas application priorto start of welding

— any reduction in the number of passes completed beforestopping back-purging.

Welding consumables for clad/lined carbon steel103 For single sided (field) joints, the same type of weldingconsumable should be used for all passes needed to completethe joint. Alternative welding consumables may be consideredfor fill and capping passes after depositing a weld thickness notless than 2 times thickness of the cladding/lining. The alterna-tive welding consumables shall be documented to be compati-ble with the welding consumables used for the root area, thebase material and the applicable service conditions. Weldingconsumables shall be segregated from consumables for C-Mnsteel.Welding consumables for duplex steel104 Welding consumables with enhanced nickel and nitro-gen content shall be used unless full heat treatment after weld-ing is performed. Sufficient addition of material from thewelding consumables is essential for welding of the root passand the two subsequent passes. Welding consumables shall besegregated from consumables for C-Mn steel.Backing and shielding gases105 Backing and shielding gases shall not contain hydrogenand shall have a dew point not higher than 30°C. The oxygencontent of the backing gas shall be less than 0.1% during weld-ing of the root pass. Backing gas shall be used for welding ofroot pass and succeeding passes. (Exception from this require-ment may be tie-in welds when stick electrodes are used forroot bead welding, subject to agreement.)Production106 Welding of clad/lined carbon steel and duplex stainlesssteel may be performed by the welding processes listed inA200. The welding shall be double sided whenever possible.Welding of the root pass in single sided joints will generallyrequire welding with Gas Tungsten Arc Welding (GTAW /141) or Gas Metal Arc Welding (GMAW / 135).107 Onshore fabrication of clad/lined carbon steel andduplex stainless steel shall be performed in a workshop, or part

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thereof, which is reserved exclusively for this type of material.During all stages of manufacturing, contamination of CRA andduplex steel with carbon steel and zinc shall be avoided. Directcontact of the CRA with carbon steel or galvanised handlingequipment (e.g. hooks, belts, rolls, etc.) shall be avoided. Toolssuch as earthing clamps, brushes etc, shall be stainless steelsuitable for working on type of material in question and notpreviously used for carbon steel. Contamination of weld bevelsand surrounding areas with iron and low melting point metalssuch as copper, zinc, etc. is not acceptable. The grindingwheels shall not have previously been used for carbon steel.Parts of internal line-up clamps that come in contact with thematerial shall be non-metallic or of a similar alloy as the inter-nal pipe surface. Thermal cutting shall be limited to plasma arccutting.108 The weld bevel shall be prepared by milling or otheragreed machining methods. The weld bevel and the internaland external pipe surface up to a distance of at least 25 mmfrom the bevels shall be thoroughly cleaned with an organicsolvent.109 Welding consumables shall be segregated from consum-ables for C-Mn / low alloy steels.110 The backing gas composition shall be monitored usingan oxygen analyser immediately prior to starting or re-startingwelding. The flow rate of the back purge gas shall be adjustedto prevent gas turbulence and possible air entrainment throughopen weld seams.111 Inter-run cleaning shall be by grinding to bright, defectfree material for all passes.112 Internal high-low of clad/lined pipes shall not exceed1 mm unless otherwise qualified or if the cladding at pipe endshas a thickness increase allowing larger misalignment. In anycase the internal high-low shall not reduce the thickness of theCRA below the specified thickness. Internal high-low ofduplex stainless steel linepipe shall not exceeded 2 mm or 1%of the pipe internal diameter, whichever is less, unless other-wise qualified.113 Welds shall be multipass and performed in a continuousoperation.114 The interpass temperature shall be measured directlywhere a weld run will start and terminate. The weld zone shallbe kept below the maximum interpass temperature before awelding run is started. Unless post weld heat treatment is per-formed the maximum interpass temperature shall not exceed100°C for nickel based CRAs and 150°C for all other CRAs.115 When clad/lined C-Mn linepipe is cut and/or re-bevelleda lamination check by through thickness ultrasonic testing anddye penetrant testing on the bevel face shall be performed. If alaminar discontinuity is detected on the bevel face the clad-ding/liner shall be removed and a seal weld shall be overlaywelded at the pipe end.Additional for welding of duplex steel116 The heat input must be controlled to avoid detrimentalweld cooling rates. For optimum control of the heat input fasterwelding speeds and associated higher welding current shouldbe used. Stringer beads shall be used to ensure a constant heatinput, and any weaving of the weld bead shall be limited tomaximum 3X filler wire/electrode diameter. For girth weldsthe heat input shall be kept within the range 0.5- 1.8 kJ/mm andavoiding the higher heat input for small wall thicknesses. Forwall thickness > xx mm and provided post weld heat treatmentis performed a maximum heat input of 2.4 kJ/mm is accepta-ble. For the root pass the heat input shall be higher than for sec-ond pass. For SAW welding small diameter wire and modestwelding parameters (high travel speed and low arc energy)shall be used. The depth to width ratio of the weld deposit shallbe less than 1.0.117 Any post weld heat treatment shall be performed in

accordance with the qualified post weld heat treatment proce-dure.118 Excavation of repair grooves shall be by chipping,grinding or machining. Air-arc gouging shall not be used.Entire welds shall be removed by plasma cutting or machining.119 All operations during welding shall be carried out withadequate equipment and/or in a protected environment toavoid carbon steel contamination of the corrosion resistantmaterial. Procedures for examination of surfaces and removalof any contamination shall be prepared.

H 200 13Cr martensitic stainless steelWPS and essential variables201 The additional data for the WPS and the essential varia-bles given in H101 and 102 also applies to 13Cr martensiticstainless steels.Welding consumables 202 The requirements to backing and shielding gases inH105 also applies to 13Cr MSS.Production 203 Welding of 13Cr MSS may be performed by the weldingprocesses listed in A200, except active gas shielded methods.The welding shall be double sided whenever possible. Weldingof the root pass in single sided joints will generally requirewelding with Gas Tungsten Arc Welding (GTAW / 141). 204 During all stages contamination of 13Cr MSS with car-bon steel and zinc shall be avoided. Direct contact with carbonsteel or galvanised handling equipment (e.g. hooks, belts, rolls,etc.) shall be avoided. Tools such as earthing clamps, brushesetc., shall be stainless steel suitable for working on type ofmaterial in question and not previously used for carbon steel.Contamination of weld bevels and surrounding areas with ironand low melting point metals such as copper, zinc, etc. is notacceptable. The grinding shall not have previously been usedfor carbon steel. Parts of internal line-up clamps that come incontact with the material shall be non-metallic or of a similaralloy as the internal pipe surface. Thermal cutting shall be lim-ited to plasma arc cutting.205 The weld bevel shall be prepared by milling or otheragreed machining methods. The weld bevel and the internaland external pipe surface up to a distance of at least 25 mmfrom the bevels shall be thoroughly cleaned with an organicsolvent.206 Welding consumables shall be segregated from consum-ables for C-Mn steel.207 The backing gas composition shall be monitored usingan oxygen analyser immediately prior to starting or re-startingwelding. Care shall be taken to adjust the flow rate of the backpurge gas to prevent gas turbulence and possible air entrain-ment through open weld seams.208 Inter-run cleaning shall be by grinding to bright, defectfree material for all passes using designated tools.209 Internal high-low of 13Cr MSS linepipe shall notexceeded 2 mm or 1% of the pipe internal diameter, whicheveris less, unless otherwise qualified.210 Welds shall be multipass and performed in a continuousoperation.211 The interpass temperature shall be measured directly atthe points where a welding run will start and terminate. Theweld zone shall be below the maximum interpass temperaturebefore a welding run is started. The maximum interpass tem-perature shall not 150oC. 212 Unless otherwise agreed PWHT (e.g.≈ 5 minutesat≈ 630oC) shall be performed in accordance with the PWHTprocedure qualified during welding qualification

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213 Excavation of repair grooves shall be by chipping,grinding or machining. Air-arc gouging shall not be used.Entire welds shall be removed by plasma cutting or machining.214 All operations during welding shall be carried out withadequate equipment and/or in a protected environment toavoid carbon steel contamination of the corrosion resistantmaterial. Procedures for examination of surfaces and removalof any contamination shall be prepared.

H 300 Pin brazing and aluminothermic welding301 Anode leads may be attached by pin brazing or alumino-thermic welding according to qualified procedures includingfull details of the technique used and associated equipment.Qualification of operators302 Operators that have performed a qualified procedure testare thereby qualified.303 Other operators shall prior to carrying out operationwork, each complete three test pieces made in accordance withthe procedure specification under realistic conditions. Eachtest piece shall pass the test for electrical resistance andmechanical strength according to Table C-6 and F500.Essential variables304 Essential variables for pin brazing and aluminothermicwelding shall be:Base material grade and chemical composition:

— a change in grade— a change in the supply condition (TMCP, Q/T or normal-

ised)— any increase in Pcm of more than 0.02, CE of more than

0.03 and C content of more than 0.02% for C-Mn linepipe.

For both methods a change in:

— cable dimension— process (brazing or aluminothermic welding)— make, type and model of equipment— method for cleaning and preparation of cable ends and

cable attachment area.

For Aluminothermic welding a change in:

— type, classification and brand of start and welding powder— type, make and model of other consumables— volume (cartridge, packaging type) and type of start and

welding powder that will change the heat input by morethan ± 15%.

For Pin brazing a change in:

— type, composition, make and model of pin for pin brazing— the minimum preheat or working temperature— range of equipment settings for pin brazing— the equipment earth connection area.

Production requirements for welding/brazing of anode leads305 The anode cable attachments shall be located at least 150mm away from any weld.306 For cable preparation cable cutters shall be used. Theinsulation shall be stripped for the last 50 mm of the cable tobe attached. The conductor core shall be clean, bright and dry.Greasy and oily conductor cores shall be cleaned with residuefree solvent or dipped in molten solder. Corroded conductorcores shall be cleaned to bright metal with brush or othermeans. Wet conductor cores shall be dried by rapid drying res-idue free solvent, alcohol or hand torch.307 The cable attachment area, and for pin brazing also theequipment earth connection area, shall be cleaned for an areaof minimum 50 mm × 550 mm. All mill scale, rust, grease,paint, primer, corrosion coating, and dirt shall be removed and

the surface prepared to finishing degree St 3 according to ISO8501-1. The surface shall be bright, clean and dry when weld-ing/brazing is started. Production testing308 Each welded/brazed anode lead shall be subjected toelectrical resistance test and mechanical strength test accord-ing to Table C-6 with acceptance criteria according to F500.Repair of welded/brazed anode leads309 Welded/brazed anode leads not meeting the require-ments in F500 shall be removed and the affected area shall beremoved by grinding.310 For welded/brazed anode leads that are attached directlyonto pressure containing parts the ground areas shall blendsmoothly into the surrounding material. Complete removal ofdefects shall be verified by local visual inspection and polish-ing and etching to confirm removal of copper penetration. Theremaining wall thickness in the ground area shall be checkedby ultrasonic wall thickness measurements to verify that thethickness of the remaining material is more than the specifiedminimum. Imperfections that encroach on the minimum per-missible wall thickness shall be classified as defects.

I. Hyperbaric Dry WeldingI 100 General101 Underwater welding on pressure containing componentsfor hydrocarbons shall be carried out utilising a low hydrogenprocess, in a chamber (habitat) where the water has been dis-placed. Other methods can be used on non-pressure containingcomponents subject to special acceptance by Purchaser.102 All relevant welding parameters shall be monitored andrecorded at the surface control station under supervision by awelding co-ordinator. The welding area shall have continuouscommunication with the control station. All operations includ-ing welding shall be monitored by a video system that can beremotely controlled from the control station.

I 200 Qualification and testing of welding personnel for hyperbaric dry welding Hyperbaric welding co-ordinator201 The welding co-ordinator for hyperbaric dry weldingshall have EWE or IWE qualifications. In addition the weldingco-ordinator shall be familiar with and have adequate experi-ence with welding procedure qualification and offshore opera-tions for the hyperbaric welding system used.202 The welding co-ordinator shall, when applicable, havecompleted the training programme required for mechanisedwelding required in I204 to I206.Welders for hyperbaric welding203 Prior to qualification testing for underwater (hyperbaric)dry welding of girth welds, welders shall have passed a weld-ing test for pipeline girth welds as specified in B200 above.Training programme204 The hyperbaric welders shall be informed on all aspectsof the work related to the welding operation, the qualifiedwelding procedures, the applicable technical specificationsand layout of the welding and habitat system.205 Hyperbaric welders shall receive a training programmeand pass an examination upon completion of the programme.The training programme shall be structured according toAnnex B of ISO 15618-2.206 In addition, for mechanised welding the training pro-gramme shall include:

— software structure of welding programme and loading of

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any welding programme prior to start of welding— perform a complete butt weld, from programming of the

welding parameters to welding of the cap passes— repair welding— daily maintenance of the welding equipment— knowledge about the functions of the welding heads and

how to replace consumables such as welding wire, contacttubes, gas nozzles and tungsten electrodes.

Test welding207 The hyperbaric welders shall perform a qualification testusing welding equipment identical or equal in function to thehyperbaric welding equipment used for production welding. 208 The qualification welding for hyperbaric welding shallbe performed in accordance with ISO 15618-2. Qualification testing of welders209 For welder qualification for dry hyperbaric welding ofgirth welds and other butt weld configurations the test piecesshall be subject to same the testing and acceptance criteria asfor pipeline girth welds in B200.210 A welder is deemed qualified for the applicable rangesof approval stated in Clause 6 of ISO 15618-2 when the fol-lowing requirements for inspection and testing of test pieces,as applicable, are met:

— 100% visual examination and 100% ultrasonic testingwith test requirements and acceptance criteria in accord-ance with Appendix D

— macro-examination according to Appendix B. The speci-men shall meet the requirements of ISO 15618-2,Chapter 8

— if 100% radiographic testing with test requirements andacceptance criteria in accordance with Appendix D is per-formed in lieu of 100% ultrasonic testing, bend testing asrequired in ISO 9606 shall be performed for all weldingprocesses.

Retesting211 See ISO 15618-2, Chapter 9.Period of validity and prolongation212 The period of validity shall be in accordance with ISO15618-2, paragraph 10.1 and prolongations in accordance withparagraph 10.2.

I 300 Welding processes for hyperbaric dry welding301 The allowable welding processes are:

— SMAW (Process ISO 4063-111)— G-FCAW (Process ISO 4063-137)— GMAW (Process ISO 4063-131)— GTAW (Process ISO 4063-141).

I 400 Welding consumables for hyperbaric dry welding401 In addition to the requirements given in C100 to C400the following shall apply:

— consumables should be of a type that is tested or developedfor dry hyperbaric welding with respect to arc stability andmetal transfer behaviour and mechanical properties

— procedures for transfer of consumables to the hyperbaricchamber and for consumable handling in the chamber,including disposal of unused exposed consumables. Theprocedure shall particularly consider the maximumhumidity expected during production welding

— all consumables for qualification of the welding procedureshall be from the same batch, a consumable batch beingdefined as the volume of product identified by the supplierunder one unique batch/lot number, manufactured in onecontinuous run from batch/lot controlled raw materials.

I 500 Shielding and backing gases for hyperbaric dry welding501 In addition to the requirements given in C500 the fol-lowing shall apply:

— the purity of shielding and backing gases shall be 99.995for Ar and 99.997% for He. The maximum allowablemoisture content in the gas used in the actual welding isgoverned by the moisture content of the gas used duringthe qualification welding.

Guidance note:The dew point temperature at atmospheric pressure (1 bar) isoften used to specify the upper level acceptance criteria for themoisture content in shielding gases. However, for hyperbaricconditions, even a low dew-point temperature (e.g. -30°C for anArgon gas) can result in condensation of water at the relevantworking depth/pressure and temperature (e.g. at 165 m at 5°C).This means that the gas is saturated with water when used at thisdepth and condensed water will be present at greater depths. Ingeneral the acceptance level for the water content in the shieldgas must be specified precisely. The use of “ppm” alone is notsufficient. It must be related either to volume or weight of thegas. It is the water concentration in the gas at the working depth/pres-sure which is essential. This can be specified as weight of thewater per volume unit (mg H2O/m3) or partial pressure of theH2O (millibar H2O).


I 600 Welding equipment and systems for hyperbaric dry welding601 In addition to the requirements given in B100 the fol-lowing shall apply unless the voltage is measured at the arcduring both qualification and production welding:

— Welding cables shall have the same dimension andapproximately the same resistance during the welding pro-cedure qualification and production welding. If necessaryartificial resistance to simulate the full cable length used inproduction should be used during qualification welding.

I 700 Welding procedures for hyperbaric dry weldingContents of pWPS 701 A pWPS shall be prepared for each welding and repairwelding procedure that will be qualified for use during weldingof pipeline girth welds. 702 The pWPS shall contain the information required for theapplicable welding processes, including any tack welds andshall be prepared in accordance with Table C-1 and shall pro-pose limits and ranges for the applicable essential variables forwelding and repair welding procedures given in Tables C-2and C-8.703 In addition the pWPS shall address the following:

— part of the root to be left open, number of runs to be depos-ited before closing the root and methods for closing theroot

— conditions for release of external line-up clamps includingthe percentage of the circumference for the welded rootsections, the length of each section and spacing of the sec-tions

— water depth (minimum/maximum)— pressure inside the chamber— gas composition inside the chamber— humidity, maximum level— temperature inside the chamber (minimum/maximum)— length, type and size of the welding umbilical— position for voltage measurements— welding equipment.

704 The welding procedures for closing possible vent holes

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shall also be qualified. This qualification test shall as a mini-mum include impact testing of weld metal, FL, FL+2, FL+5,hardness testing and for CRA also metallographic examina-tion. The qualification may be performed as a "buttering" testproviding considerations are made to start/stop and that accesslimitations for the actual production welding is simulated.

Essential variables705 The essential variables for hyperbaric dry welding shallbe according to Table C-2 with additional requirementsaccording to Table C-8 below.

I 800 Qualification welding for hyperbaric dry welding801 Qualification welding shall be performed in the habitatat a water depth selected in accordance with the intended rangeof qualification, or under appropriately simulated conditions.The qualification test program shall consist of a minimum ofone completed joint for manual welding, and a minimum ofthree joints for mechanised welding systems.802 Qualification welding shall comply with E100 and thefollowing additions:

— for SMAW welding shall be performed at the maximumexpected humidity in the chamber during productionwelding

— the power source and the technical specification for thewelding system shall be equivalent to the production sys-tem

— the pipes shall be rigidly fixed to simulate restraint duringwelding

— method and position/point for monitoring of electricalparameters shall be as for production welding

— with increasing pressure the voltage gradient will increase.Accordingly may small changes in arc length and or oper-ating depth result in considerable changes in the monitoredvalues of arc voltage. For calculations of the heat input, thearc voltage shall be recorded at the position/point of weld-ing during qualification of the welding procedure and thedifference between these values and remote monitoredvalues recorded for use during production welding.

Repair welding procedures803 Qualification welding shall be performed in compliancewith the requirements given in E200.

I 900 Qualification of welding procedures for hyper-baric dry welding901 The requirements given in E300 shall apply.

I 1000 Examination and testing1001 Examination and testing shall be in accordance withF100, F200 and F300.

I 1100 Production welding requirements for dry hyper-baric welding1101 In addition to the applicable requirements given in G,H100 and H200, the requirements below shall apply for dryhyperbaric production welding:

1102 The habitat shall be of adequate size to allow access forwelding and for all necessary welding, safety and life supportequipment. Further the habitat shall be lighted and be fittedwith remote cameras for surveillance. Welding fumes shall notprevent the use of the remote cameras in the welding area.1103 A function test of the habitat, habitat equipment and themonitoring and communication equipment shall be performedto a written and agreed procedure, and accepted before lower-ing the habitat to the working position. The function test shallalso include verification of that the welding parameters areapplied correctly on the actual equipment.1104 If used shielding and/or backing gas shall be of quali-fied purity including moisture limit. Gas purity and composi-tion in all containers shall be certified and traceable to the gasstorage containers. The gas purity and moisture content shallbe verified after purging the gas supply system prior to start ofwelding. The moisture content of the shielding gas shall bemonitored at/near the torch during welding operation.1105 Any pup pieces shall be bevelled at the surface andchecked for correct length, laminations at cut ends and square-ness of ends.1106 At completion of positioning of the two pipe sectionsto be welded, the following information, as a minimum, shallbe reported to the surface:

— pipe sections to be connected (pipe number, heat numberif possible)

— approximate distance from the girth weld to the pipeextremity

— position of the longitudinal welds.

1107 If the requirement for staggering of welds can not bemet, any reduction in the separation of welds shall be limitedto two pipe lengths.1108 All operations including welding shall be monitored bya video system that can be remotely controlled from the controlstation and the welding area shall have continuous communi-cation with the control station. All relevant data shall be mon-itored and recorded at the surface control station undersupervision by the welding co-ordinator, including:

— environmental conditions (humidity, temperature, atmos-phere composition)

— welding parameters (mechanised and automatic welding)— gas moisture content— preheat and interpass temperature

Table C-8 Additional essential variables for hyperbaric dry weldingA Qualified water depth for SMAW and GTAW 1) Water depth (WD) in metres: 1 WD ≤ 200 m: Any increase in excess of + 20% or 10 m or whichever is greater.

2 200 m < WD ≤ 300 m: ± 10%3 300 m < WD ≤ 500 m: ± 10%

B Habitat environmentGas composition (argon, heliox, air or nitrox), and humidity

1 For water depth ≤ 200 m: A change from argon or heliox to air or nitrox but not vice versa2 For water depth > 200 m: Any change in gas composition3 Any increase in relative humidity for SMAW and G-FCAW flux based welding processes oth-

erwise any increase in excess of + 10%C Monitoring of electrical parametersMethod and point of monitoring 1 Any changeNote

1) For other processes the depth of qualification shall be agreed.

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— information transmitted by the welders.

1109 The following records shall be presented as part of thedocumentation:

— chart recordings of welding current, arc voltage, filler wirespeed, welding speed

— video recording from the weld observation cameras.

Weld repair1110 The applicable requirements given Table C-7 shallapply. In addition repairs exceeding 30% of pipe OD shall beperformed only if agreed.

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Offshore Standard DNV-OS-F101, October 2007 App.D –

APPENDIX D NON-DESTRUCTIVE TESTING (NDT)

A. General

A 100 Objective101 This Appendix specifies the requirements for methods,equipment, procedures, acceptance criteria and the qualifica-tion and certification of personnel for visual examination andnon-destructive testing (NDT) of C-Mn steels, low alloy steels,duplex steels, other stainless steels and clad steel materials andweldments for use in pipeline systems.102 This Appendix does not cover automated ultrasonic test-ing (AUT) of girth welds. Specific requirements pertaining toAUT of girth welds are given in Appendix E. 103 Requirements for NDT and visual examination of othermaterials shall be specified and be in general agreement withthe requirements of this Appendix.

A 200 Applicability of requirements201 The requirements in this Appendix are given in severalsubsections with each subsection dealing with the non-destruc-tive testing of specific objects.202 The requirements given in subsection A are applicablefor the whole of this Appendix.203 The requirements given within the other subsections areapplicable only to the scope of the subsection as indicated inthe title of the subsection, unless specific references to othersubsections are made.

A 300 Quality assurance301 NDT Contractors and organisations shall as a minimumhave an implemented quality assurance system meeting thegeneral requirements of ISO 9001 and supplemented with therequirements given in ASTM E1212.

A 400 Non-destructive testing methods401 Methods of NDT shall be chosen with due regard to theconditions influencing the sensitivity of the methods. The abil-ity to detect imperfections shall be considered for the material,joint geometry and welding process used.402 As the NDT methods differ in their limitations and/orsensitivities, combination of two or more methods shall beconsidered since this is often required in order to ensure opti-mum probability of detection of harmful defects.403 Magnetic particle, eddy current or magnetic flux leakagetesting is preferred for detection of surface imperfections inferromagnetic materials. For detection of surface imperfec-tions in non-magnetic materials, either liquid penetrant testingor eddy current testing shall be preferred.404 Ultrasonic and/or radiographic testing shall be used fordetection of internal imperfections. It may be necessary to sup-plement ultrasonic testing by radiographic testing or viceversa, in order to enhance the probability of detection or char-acterisation/sizing of the type of flaws that can be expected.Radiographic testing is preferred for detection of volumetricimperfections. For material thicknesses above 25 mm radio-graphic testing should always be supplemented by ultrasonictesting.Ultrasonic testing shall be preferred for detection of planarimperfections. Whenever determination of the imperfectionheight and depth is necessary, e.g. as a result of an ECA, ultra-sonic testing is required.

Guidance note:The detectability of cracks with radiographic testing depends onthe crack height, the presence of branching parts of the crack, thedirection if the X-ray beam to the orientation of the crack andradiographic technique parameters. Reliable detection of cracksis therefore limited.Lack of sidewall fusion will probably not be detected unless it isassociated with volumetric imperfections or if X-ray beam is inthe direction of the side-wall.


405 When manual non-destructive testing in special cases isused as a substitute for automated ultrasonic testing for pipe-line girth welds, both radiographic and ultrasonic testing of thegirth weld shall be performed.406 Alternative methods or combination of methods fordetection of imperfections may be used if the methods aredemonstrated as capable of detecting imperfections with anacceptable equivalence to the preferred methods.

A 500 Personnel qualificationsManual or semi-automatic NDT501 Personnel performing manual or semi-automated NDTand interpretation of test results shall be certified to Level 1 orLevel 2 by a Certification Body or Authorised QualifyingBody in accordance with EN 473, ISO 9712 or the ASNT Cen-tral Certification Program (ACCP). Personnel qualification toan employer based qualification scheme as SNT-TC-1A maybe accepted if the employer’s written practice is reviewed andfound acceptable and the Level 3 is ASNT Level III or ACCPProfessional Level III and certified in the applicable method.Automated NDT, general502 Personnel calibrating equipment and interpreting resultsfrom automated equipment for NDT shall be certified to anappropriate level according to a certification scheme meetingthe requirements of 501. In addition, they shall be able to doc-ument adequate training and experience with the equipment inquestion, and shall be able to demonstrate their capabilitieswith regard to calibrating the equipment, performing an oper-ational test under production/site/field conditions, and evaluat-ing size and location of imperfections.Automated NDT, linepipe manufacture503 Personnel operating automated equipment for NDT dur-ing manufacture of linepipe shall be certified according to ISO11484 or equivalent certification scheme.Preparation of NDT procedures504 Preparation of NDT procedures and execution of allNDT shall be carried out under the responsibility of Level 3personnel and shall be performed by personnel holding at leastLevel 2 qualifications. Personnel holding Level 1 qualifica-tions may carry out NDT under the direct supervision of Level2 personnel.Visual examination505 Personnel performing visual examination of welds shallhave documented training and qualifications according to NS477 or minimum IWIS or equivalent certification scheme. Per-sonnel performing visual examination of other objects shallhave training and examination according to a documented in-house standard.Visual acuity506 Personnel interpreting radiographs, performing ultra-sonic testing, interpreting results of magnetic particle and liq-

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Offshore Standard DNV-OS-F101, October 2007 – App.D

uid penetrant testing and performing visual examination shallhave passed a visual acuity test such as required by EN 473,paragraph 6.3 or a Jaeger J-w test at 300 mm, within the previ-ous 12 months.

A 600 Timing of NDT601 Whenever possible, NDT of welds shall not be per-formed until 24 hours has elapsed since completion of weld-ing.602 If welding processes ensuring a diffusible hydrogen con-tent of maximum 5 ml/100 g of weld metal are used, adequatehandling of welding consumables is verified, shielding gascontent of H2 is controlled, or measures (such as post heatingof the weldment) are taken to reduce the contents of hydrogen,the time in 601 above can be reduced, subject to agreement.603 NDT of pipeline installation girth welds and longitudi-nal welds in linepipe can be performed as soon as the weldshave cooled sufficiently to allow the NDT to be performed.

B. Manual Non-Destructive Testing and Visual Examination of Welds

B 100 General101 Manual non-destructive testing of welds shall be per-formed in compliance with the standards listed below and asrequired in the following:

Radiography ISO 17636Ultrasonic ISO 17640 Magnetic Particle ISO 17638Liquid Penetrant ASTM E 1417Eddy Current ISO 17643Visual examination ISO 17637Non-destructive testing procedures102 Non-destructive testing shall be performed in accord-ance with written procedures that, as a minimum, give infor-mation on the following aspects:

— applicable code(s) or standard(s)— welding method (when relevant)— joint geometry and dimensions— material(s)— method— technique— equipment main and auxiliary— consumables (including brand name)— sensitivity— calibration techniques and calibration references— testing parameters and variables— assessment of imperfections— reporting and documentation of results— reference to applicable welding procedure(s),— example of reporting forms— acceptance criteria.

103 If alternative methods or combinations of methods areused for detection of imperfections, the procedures shall beprepared in accordance with an agreed code or standard. Theneed for procedure qualification shall be considered in eachcase based on the method's sensitivity in detecting and charac-terising imperfections and the size and type of defects to bedetected.104 All non-destructive testing procedures shall be signed bythe responsible Level III person.Reporting105 All NDT shall be documented such that the tested areasmay be easily identified and such that the performed testingcan be duplicated. The reports shall identify the defects present

in the weld area and state if the weld satisfies the acceptancecriteria or not.106 The report shall include the reporting requirements of theapplicable standard, NDT procedure and acceptance criteria.At least the following minimum information must be given:

— Name of the company and operator carrying out the testingincluding certification level of the operator

— Object and drawing references— Place and date of testing— Material type and dimensions— Post weld heat treatment, if required— Location of examined areas, type of joint— Welding process used— Surface conditions— Temperature of the object— Number of repairs if specific area repaired twice or more— Contract requirements e.g. order no., specifications, spe-

cial agreements etc.— Example of reporting forms— Sketch showing location and information regarding

detected defects— Extent of testing— Test equipment used— Description of the parameters used for each method— Description and location of all recordable indications— Testing results with reference to acceptance level— Other information related to the specific method may be

listed under each method.

B 200 Radiographic testing of welds201 Radiographic testing shall be performed in compliancewith ISO 17636 and as required below.202 Radiographic testing shall be performed by use of X-rayaccording to accepted procedures. Use of radiographic iso-topes (gamma rays) may be required in some situations and issubject to agreement in each case. If use of radiographic iso-topes is agreed, Se 75 as gamma ray source shall be preferred.Radiographic testing procedures 203 Radiographic testing procedures shall be according toB102 through B104 and include:

— radiographic technique class — radiation source— technique— geometric relationships— film type— intensifying screens— exposure conditions— processing— Image Quality Indicator sensitivities in percent of the wall

thickness, based on source and film side indicators respec-tively

— backscatter detection method— density— film side Image Quality Indicator (IQI) identification

method— film coverage— weld identification system.

Classification of radiographic techniques204 The radiographic techniques used shall be according toClass B and the requirements below.205 Class B techniques shall also be used when usinggamma ray sources, unless otherwise agreed. 206 If, for technical reasons, it is not possible to meet one ofthe conditions specified for Class B, the note to Chapter 5 of ISO 17636 shall apply.Image Quality Indicators

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207 Image Quality Indicators (IQIs) shall meet the require-ments given in ISO 19232. The wire material shall have a coef-ficient of absorption as close as possible to the material tested.If the absorption coefficients of the IQI material and the mate-rial tested differ by more than 20%, an experimental evaluationaccording to ISO 19232-4 shall be performed to establish theacceptable image quality values.Sensitivity208 The sensitivities obtained during production radiogra-phy shall at least meet the requirements of ISO 17636, AnnexA except for double wall techniques with the IQI on the filmside. For this technique, the sensitivity of the film side IQIfrom the procedure qualification shall be used as acceptancecriterion for film sensitivity.Radiographic procedure qualification209 Each radiographic procedure and the consumables usedshall be qualified by making radiographic exposures of awelded joint or base material with the same or typical config-uration and dimensions, and of material equivalent to thatwhich shall be used in production radiography. For procedures using source side IQIs, the sensitivity shallmeet the applicable criterion in ISO 17636, Annex A and theaverage density at the sound weld metal image shall be mini-mum 2.0. The maximum density allowed shall be according tothe capabilities of the available viewing equipment, but notmore than 4.0.210 For procedures using film side IQIs, the IQIs shall forradiographic procedure qualification purposes be placed onboth the film side and the source side.The sensitivity of the source and film side IQIs shall both sat-isfy the applicable criteria in ISO 17636, Annex A and the den-sity shall meet the requirements of 208. If the sensitivity of the film side IQI is better than required bythe applicable criterion in ISO 17636, Annex A the film sidesensitivity obtained during procedure qualification shall berecorded and be acceptance criterion for the sensitivity of thefilm side IQI during production radiography.Processing and storage211 Processing of radiographs shall conform to ISO 17636.Storage shall be such that the radiographs maintain their qual-ity for a minimum of 5 years without deterioration. Thiosul-phate tests shall be performed at regular intervals.If radiograph storage time in excess of 5 years is required, theradiographs should be digitised using methods giving adequateresolution and stored in electronic media in an agreed manner.Reporting212 Reports shall be in accordance with B105 and B106. Inaddition to the items listed in ISO 17636 the following shall beincluded in the radiographic testing report:

— radiographic procedure reference— geometric unsharpness.

Radioscopic testing213 Radioscopic testing techniques in accordance with EN13068 may be used provided the equipment has been demon-strated, in accordance with Subsection F, to give sensitivityand detection equivalent to conventional x-ray according toISO 12096.Specific requirements to radiography of installation girthwelds214 For radiography the following additional requirementsshall apply for installation girth welds:

— Panoramic (single wall single image) exposures shall beused whenever possible

— Fluormetallic screens may be used in combination with X-

ray based on a satisfactory procedure qualification testwhere all requirements to sensitivity are met. Films usedwith fluormetallic screens shall be designed for use withthis screen type

— For pipe with internal diameter < 250 mm gamma ray andpanoramic (single wall single image) exposures may beused. The gamma ray source shall preferably be Se 75used with a film system class better than C4 according toISO 17636, Table 3 unless otherwise agreed. Other typesof radiation sources may be used for small wall thick-nesses in combination with other film types. The use ofgamma ray sources shall always be based on a satisfactoryprocedure qualification test where all requirements to sen-sitivity are met

— Where no internal access is possible, a double wall tech-nique shall be applied

— For the double wall double image technique x-ray shall beused. Fluormetallic screens may be used based on a satis-factory procedure qualification test where all requirementsto sensitivity are met. Films for use with fluormetallicscreens shall be suitable for this screen type

— For the double wall single image technique both X-ray andgamma ray may be used. The choice of radiation source,film and screen types shall be based on a satisfactory pro-cedure qualification test where all requirements to sensi-tivity are met.

B 300 Manual ultrasonic testing of welds in C-Mn/low alloy steel with C-Mn/low alloy steel weld deposits301 Ultrasonic testing shall be performed in compliance withISO 17640 and as required below.302 Ultrasonic testing shall be performed according toaccepted procedures.Ultrasonic testing procedures 303 Ultrasonic testing procedures shall be according to B102through B104 and include:

— type of instrument— type and dimensions of probes— range of probe frequencies— description of reference block— calibration details, range and sensitivity— surface requirements, including maximum temperature— type of coupling medium— scanning techniques supplemented with sketches, show-

ing the probes used and area covered— recording details.

304 Typical applications, which require specific UT proce-dures, are:

— Estimation of defect size (height) using conventionalbeam spread diagram (20 dB drop), Time-Of-Flight-Dif-fraction (TOFD) technique or the back diffraction tech-nique.

— Testing of objects with temperature outside the range 0 ºCto 40 ºC.

The ultrasonic testing procedure shall be submitted for accept-ance.305 No special procedure qualification test should berequired when manual methods are used. Ultrasonic testing techniques306 Ultrasonic testing techniques shall be in accordance withISO 17640 and the requirements below.

Guidance note:Manual or semi- automated ultrasonic phased array systems maybe used provided it is demonstrated that such systems will givethe same sensitivity, resolution and detection ability as conven-tional ultrasonic testing performed according to the requirements

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given in B300 and that specific ultrasonic testing procedures aredeveloped and accepted.


Manual ultrasonic testing equipment307 Manual ultrasonic testing equipment shall:

— be applicable for the pulse echo technique and for the dou-ble probe technique

— cover as a minimum the frequency range from 2 to 6 MHz— have a calibrated gain regulator with maximum 1 dB per

step over a range of at least 60 dB— have a flat screen accessible from the front for direct plot-

ting of reference curves or be equipped with digital DAC-display presentation of user-defined curves

— allow echoes with amplitudes of 5 per cent of full screenheight to be clearly detectable under test conditions.

308 Calibration of ultrasonic equipment shall be undertakenaccording to procedures established according to a recognisedcode or standard, e.g. EN 12668-1-2-3 or ASME V. Verifica-tion of Screen Height Linearity and Amplitude Linearity shallbe performed at the beginning of each period of extended use(or every 3 months, whichever is less). Calibration recordsshall be made available upon request.Probes309 Probes used for testing of welds with C-Mn steel welddeposits shall be characterised as required by ISO 10375 andISO 12715.Angle beam shear-wave probes shall be available in anglesallowing effective testing of the actual weld connections. Fortesting of girth welds or welds in plate probe angles of 45°, 60°and 70° will normally be sufficient but additional probes of 35°and 55° are recommended. Other applications may requireprobes covering the range of 35° to 80º to allow effective testing. Straight beam probes shall be single or twin crystal probes.Twin crystal probes shall be used when testing is performed onmaterial with nominal thickness t < 60 mm. Single crystalprobes may be used when testing is performed on material withnominal thickness t ≥ 60 mm.Probes shall, if necessary, be suitable for use on hot surfaces(100 to 150°C).310 Additional probes for time-of-flight diffraction (ToFD)and double probe techniques are recommended.

311 Probe frequencies shall be selected according toISO 17640.

Guidance note:The nominal angle of probes used are normally valid for C-Mnsteels with compression wave velocity of approximately 5900 m/s and shear wave velocity of approximately 3200 m/s at 20oC.


Coupling medium312 The same coupling medium as used for calibration andsetting of gains and amplification shall be used during testing.Calibration of range scale and angle determination313 The IIW or ISO calibration blocks (V1 – V2) accordingto ISO 2400 or ISO 7963 respectively, shall be used for cali-bration of range scale and for angle determination. These cali-bration blocks shall, as near as practicable, have the sameacoustic properties as the material to be tested. Reference blocks for setting of reference levels314 For testing of welds reference blocks shall be used forgain calibration and construction of the reference curves. Thereference block shall be manufactured from the actual materialto be examined. Reference blocks manufactured from othermaterials may be acceptable provided that the material is doc-umented to have acoustic properties similar to the actual mate-rial to be examined. The reference block shall have length andwidth dimensions suitable for the sound beam path for allprobe types and the material dimension(s) to be tested.For testing of welds in plate and similar geometries a referenceblock with side drilled holes shall be used. The thickness of thereference block, diameter and position of the drilled holes shallbe as shown in Figure 1 and Table D-1.For testing of welds in pipe when testing can be performedfrom one side only, and the DAC reference signals can only beobtained from the side where the inspection shall be per-formed, i.e. the OD side, the reference blocks shall have sidedrilled holes at T/4, T/2 and 3/4T.When ultrasonic testing is to be performed on TMCP steel ref-erence blocks shall, when required, be produced perpendicularto and/or parallel to the direction of rolling. The rolling direc-tion shall be clearly identified.315 For testing of longitudinal welds in pipe and similargeometries the reference block shall in addition to the featuresrequired above, have a curvature equal to the pipe to be tested.

Figure 1 Reference block dimensions

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316 All reference blocks shall be marked with an identifica-tion that relates to the specific application of each blockGain calibration 317 The DAC- curve shall be constructed using referenceblocks with side-drilled holes as described in 315.318 Reference blocks not made from the actual material tobe tested shall be checked for variation in acoustic propertiesbetween the reference block and the actual material. The vari-ation can be checked by calibrating the range scale on the ISO2400 block with a normal probe and subsequently measure aknown material thickness with this calibration.319 Whenever ultrasonic testing of welds in TMCP steel is per-formed, the difference in attenuation between transverse and lon-gitudinal rolling direction shall be checked when the scanningdirection changes between transverse and parallel to the rollingdirection. This requires DAC constructed by use of calibrationblocks taken from transverse and parallel to the rolling direction.Difference in gain setting must be noted and taken into consider-ation when evaluation of indications is performed.320 When testing is carried out of welds in TMCP steel theactual beam angle shall be determined. The angle can be cal-culated using trigonometric functions as long as the distanceand depth to the reflectors in the TMCP steel reference blockis known. Alternatively the method described in Appendix E,subsection J can be used.Construction of the reference curves (DAC)321 The echo reflected from the drilled hole in the calibra-tion block shall be maximised and the amplitude set at 80% offull screen height. 322 The first point of DAC must be selected such that thedistance in sound path from the probe index to the drilled holeis not less than 0.6 N where N is the near field length of the rel-evant probe. The DAC shall be constructed by obtaining atleast 3 points on the curve. The gain setting shall be recordedand comprises the primary gain.The recorded gain following all corrections for surface conditionand attenuation is the corrected primary gain. Alternatively, aTime Corrected Gain calibration can be used if the ultrasonicapparatus is fitted with a time corrected gain (TCG) correction.The echo amplitude reflected from the drilled hole in the calibra-tion can be adjusted to 80% of full screen height over the wholerange in question. DAC will thus be a horizontal line. Periodical checks of equipment, re-calibration and re-exami-nation323 At approximately four-hourly intervals and at the end oftesting, the range scale, probe angle and primary gain must bechecked and confirmed. If deviation is found to be larger than 2% of range scale, or 4dB of primary gain setting or 2º of nominal probe angle, theequipment shall be re-calibrated and the testing carried outwith the equipment over the previous period shall be repeated. Re-calibration shall be performed whenever the equipment hasbeen out function for any reason including on-off and when-ever there is any doubt concerning proper function of the

equipment. Contact surface324 For ultrasonic testing the contact surface shall be cleanand smooth, i.e. free from dirt, scale, rust, welding spatter, etc.which may influence the result of the testing. Correction fordifferences in surface conditions and attenuation between thereference block and the actual work piece shall be performedand the maximum correction allowed on flat surfaces is 6 dB.Testing levels325 The testing level shall be in accordance with ISO 17640,chapter 11, testing level B and the requirements below.Probe selection326 In addition to straight beam probe minimum two angleprobes shall be used for the testing, see the guidance given inTable D-2. It is emphasised that this table is for guidance andthat the actual choice of angle probes must be made carefullyand depending on material thickness, weld bevel and type ofdefects likely to occur with the welding method used.

327 The choice of optimum probe angle for initial full scan-ning of the weld shall be chosen such that incident angle of thesound beam centre is perpendicular to the side of the weldbevel. If this angle does not comply with any standard probeangle, the nearest larger probe angle shall be selected. 328 In addition to the probe used for initial scanning twoadditional angle probes shall be used when possible. 329 These additional probes shall have a larger and smallerangle than the probe used for initial scanning. The differencesin angle shall be more than 10o. 330 If only one additional probe can be used the angle forthis probe should be:

— ≥ 10° different— Larger than the initial probe if the sound beam centre of

the initial probe is perpendicular to the side of the weldbevel

— Smaller than the initial probe if the nearest larger probeangle was selected for the initial probe

Testing of welds331 When scanning, the gain shall be increased by a mini-mum of 6 dB above the corrected primary gain. Testing ofwelds shall be performed in accordance with ISO 17640. 332 The scanning zone for angle probes in the base materialshall be examined with straight beam (normal) probes for fea-tures that might influence the angle beam testing. The scanningzone is defined as 1.25 × full skip distance. Features interferingwith the scanning shall be reported.

Table D-1 Reference Block DimensionsMaterial thickness (t) Thickness

of referenceblock (T)

Diameter ofside drilledhole (mm)

Position ofside drilledhole

Note

T < 15 mm 15 mm or t 2.4 ± 0.2T/2

Additional holes are required for testing of pipe when the DAC can be constructed from one side only. Additional holes are generally allowed and recommended

15 mm ≤ t < 35 mm 20 mm or t 3.0 ± 0.235 mm ≤ t < 50 mm 38 mm or t50 mm ≤ t < 100 mm 75 mm or t 3.0 ± 0.2

T/4100 mm ≤ t < 150 mm 125 mm or t

Table D-2 Guidance for angle probesParent material thickness, T Probe angle8 – 20 mm 60º and 70º20 – 40 mm 45º, 60º, 70ºT > 40 mm 45º, 60º 70º

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333 The welds shall whenever feasible be tested from bothsides on the same surface and include scanning for both trans-verse and longitudinal indications. For T-joints and plate thick-ness above 70 mm, scanning from both surfaces and allaccessible sides shall be performed. Evaluation of indications334 For evaluation of indications the gain shall be reducedby the increased dB level used during scanning.335 All indications equal to or exceeding 33% of the refer-ence curve (evaluation level) shall be evaluated. The indica-tions shall be investigated by maximising the echoes byrotating the probes and by using different angle probes withDAC established according to 321 and 322. 336 The length of an indication shall be determined by meas-uring the distance between the points where the echo ampli-tude exceeds the evaluation level using the fixed leveltechnique.337 The final evaluation against the acceptance criteria shallbe based on the echo amplitude and length measured with theprobe angle giving the maximum response.Reporting338 Reports shall be in accordance with B105 and B106. Inaddition to the items listed in ISO 17640 the following shall beincluded in the ultrasonic testing report:

— identification of the ultrasonic testing procedure used— the length of acceptable indications with amplitude

exceeding 50% of the reference curve.

B 400 Manual ultrasonic testing of welds with CRA (duplex, other stainless steels and nickel alloy steel) weld depositsGeneral401 Ultrasonic testing shall be performed in compliance withB300, ISO 17640, and as required below.402 Weld deposits in duplex, austenitic stainless steels andnickel alloys have a coarse grain structure with variations ingrain size and structure resulting in unpredictable fluctuationsin attenuation and ultrasonic beam patterns. Duplex and auste-nitic stainless steel base materials, in particular forgings andcastings, will have the same characteristics. Ultrasonic testing of welds with CRA (duplex, other stainlesssteels and nickel alloy steel) weld deposits will in order toachieve an adequate detection of imperfections require thatspecial calibration blocks and probes are used for testing ofwelds in these materials. Angle probes generating compression

waves must normally be used in addition to straight beamprobes, angle shear wave probes and creep wave probes. Ultrasonic testing procedures 403 Specific ultrasonic testing procedures shall be developedfor this testing in compliance with this chapter and including theinformation required in B102 and B303. The procedure shall besubmitted for acceptance prior to start of testing.Personnel qualifications 404 In addition to the requirements given in A500 personnelperforming testing of welds with duplex, other stainless steelsand nickel alloy steel weld deposits shall be qualified for ordocument adequate experience and training for this type ofultrasonic testing.Manual ultrasonic testing equipment405 The requirements given in B307 and B308 shall applyProbes406 In addition to the requirements given in B309, B310 andB311, the requirements below shall apply.407 Probes used for testing shall normally be straight beamtransducers and twin crystal (transmitter/receiver) compres-sion wave probes of 45º, 60º and 70º. In addition similar shear-wave angle probes shall be used, if found suitable.408 In general, using a combination of shear and compres-sion wave angle probes is recommended since the detection of"open to surface" imperfections on the opposite surface of thescanning surface, e.g. incomplete penetration or lack of fusion,may increase by using shear wave probes. It must, however, beverified by using calibration blocks with actual weld connec-tions, see 418 below, that angle shear wave probes are suitable.409 Creep wave probes shall be used for detection of sub sur-face defects close to the scanning surface, unless testing can beperformed from opposite sides.Reference blocks for setting of reference levels410 In addition to the reference blocks as described in B314,B315 and B316, reference blocks prepared from the actual testmaterial and containing welds produced in accordance with theactual WPS shall be used for establishing the DAC. These ref-erence blocks shall have the weld ground flush and the surfacecondition of the calibration blocks shall be typical of the con-dition of the parent material(s) in the scanning areas. 411 The reference block for construction of DAC shall haveside drilled holes with dimensions according to Table D-3 andlocated as shown in Figure 2. The length and width of the ref-erence blocks shall be sufficient to allow the scanning neededfor construction of the DAC.

Figure 2 Reference block for construction of DAC, dimensions

Notes:

1) Side drilled holes shall be drilled in the fusion line and in the base mate-rial. Holes in the base material shall be in the same relative position as

the fusion line holes. 2) Holes shall be drilled in both fusion lines and base material when two dis-

similar materials are welded to each other.3) For double sided welds, side drilled holes shall be located in the fusion

line for the full thickness of the weld.4) For hole positions when t ≥ 50 mm, see Table D-3.

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412 The reference block for sensitivity setting for creepwave probes shall have 0.5-1.0 and 2.0 mm spark erodednotches with a minimum length of 20 mm as shown in

Figure 3. The location of notches shall allow setting againsteach individual notch.

Figure 3 Reference block for sensitivity setting for creep wave probes, di-mensions

Construction of the reference curves (DAC) for angle com-pression wave probes413 Angle compression wave probes shall and can only beused for scanning without skipping. The construction of theDAC curves using angle compression wave probe shall be per-formed according to:

— when the ultrasonic beam is passing through the parentmetal only

— when ultrasonic beam is passing through the weld metal.

414 When the ultrasonic beam is passing through the parentmetal only the DAC curve shall be constructed from the drilledholes in the parent material of the calibration blocks, seeFigure 2. Next, a maximum response shall be obtained from theholes in the weld fusion line and if necessary, the gain settingshall be adjusted such that this response reach the DAC con-structed against drilled holes in the parent material. This shall bethe primary gain to be used when locating indications on thefusion line on the side of the weld nearest to the scanning side.415 When the ultrasonic beam is passing through the weldmetal, the DAC curve shall be constructed from the holesdrilled in the fusion line on the side of the weld opposite to thescanning side. See Figure 2. This DAC shall be verified againstthe holes drilled in the base material. Any variations must benoted so that echoes reflected from indications within the weldzone can be evaluated for amplitude response.Transfer correction416 Since compression wave angle probes can only be usedwithout skipping, transfer correction can not be performed.The calibration blocks must therefore have a surface finish

similar to the production material.Sensitivity setting for creep wave probes417 The reference block shown in Figure 3 shall be used forsensitivity setting for creep wave probes. The echo responsefrom the 1.0 mm notch shall be set to 75% of FSH.Shear wave angle probes418 If shear angle probes are considered for skipped scanningor in the root area of single sided welds, it must be verified on thereference blocks with welds, see Figure 2, if it is possible toobtain a DAC with a shear wave angle probe that is comparableto the DAC obtained with an angle compression wave probe.Preparation of weld and scanning surfaces for testing419 Prior to starting the testing the external weld cap shall beground flush with the adjacent base material. The surface fin-ish of the weld and the scanning areas shall be as that on thereference blocks to be used or better.Probe selection420 In addition to the straight beam probe minimum twoangle probes shall be used for the testing, see the guidancegiven in Table D-2 and B326 through B330.421 Where the weld configuration or adjacent parts of theobject are such that scanning from both sides is not possible,two additional probes shall always be used.

B 500 Manual magnetic particle testing of weldsGeneral501 Magnetic particle testing shall be performed in compli-ance with ISO 17638 and as required below.502 Magnetic particle testing shall be performed accordingto accepted procedures.Magnetic particle testing procedures503 Magnetic particle testing procedures shall be according

Table D-3 Reference Block DimensionsMaterial thickness (t) Thickness of reference block (T) in Diameter of side drilled hole in mm Position of side drilled holes.T < 15 mm 15 mm or t 2.4 ± 0.2 T/4, T/2 and T3/415 mm ≤ t < 35 mm 25 mm or t 3.0 ± 0.235 mm ≤ t < 50 mm 45 mm or t50 mm ≤ t < 100 mm 75 mm or t 3.0 ± 0.2 The distance between the two outer

holes and the nearest surface shall not exceed 12 mm.

100 mm ≤ t < 150 mm 125 mm or t

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to B102 through B104 and include:

— type of magnetisation— type of equipment— surface preparation— wet or dry method— make and type of magnetic particles and contrast paint— magnetising current (for prod magnetising, the prod type

and spacing shall be stated)— demagnetisation— description of the testing technique.

504 No special procedure qualification tests is required.Magnetising equipment505 The equipment shall be tested at maximum 6 monthsinterval to verify that the required field strength is establishedat the maximum leg spread/prod spacing to be used. Theresults shall be recorded.506 Prods shall be soft tipped with lead or similar. Sparksbetween the prods and the material tested shall be avoided.507 Electromagnetic AC yokes shall develop a minimumlifting force of 5 kg at maximum leg spread. The lifting forceshall be checked prior to start of any testing and at regularintervals during testing.508 Use of permanent magnets is not permitted. DC yokesmay only be used for specific applications if required bynational regulations.Application techniques509 Magnetic particle testing shall not be performed on partswith surface temperatures exceeding 300°C. Between 60°Cand 300°C, only dry magnetic particle testing shall be used.Detection media510 Testing using fluorescent wet magnetic particles shouldbe the preferred method.511 If non-fluorescent wet or dry particles are used they shallprovide adequate contrast with the background or the surfacebeing tested.Viewing conditions512 Testing with fluorescent magnetic particles shall be con-ducted in a darkened area with maximum 20 lux backgroundlight, using filtered ultraviolet light with wave lengths in therange of 3200 to 3900 Å. Operators/interpreters shall allowsufficient time for eyesight to adjust to the dark surroundings.Interpreters shall not wear photo-chromatic viewing aids.Reporting513 Reports shall be in accordance with B105 and B106. Inaddition to the items listed in ISO 17638 the following shall beincluded in the testing report:

— Identification of the testing procedure used.

B 600 Manual liquid penetrant testing of weldsGeneral601 Liquid penetrant testing shall be performed in compli-ance with ASTM E 1417 and as required below602 Liquid penetrant testing shall unless otherwise agreed,only be used on non-ferromagnetic materials or materials withgreat variation in magnetic permeability.603 Liquid penetrant testing shall be performed according toaccepted proceduresProcedures604 Liquid penetrant testing procedures shall be according toB102 through B104 and include:

— surface preparation— make and type of penetrant, remover, emulsifier and

developer— details of pre-testing cleaning and drying, including mate-

rials used and time allowed for drying— details of penetrant application: the time the penetrant remains

on the surface, the temperature of the surface and penetrantduring the testing (if not within the 15°C to 35°C range)

— details of developer application, and developing timebefore evaluation

— method for post-test cleaning.

Application techniques605 The penetration and developing times shall be longenough to allow effective detection of the smallest indicationsallowed. Demonstration of adequate detection shall be per-formed for short penetration times.

Guidance note:The penetration time for water washable penetrants should nor-mally not be less than 40 - 60 minutes and for post-emulsifiedpenetrants not less than 15 - 20 minutes.


606 When the temperature of the surface and the penetrant iswithin the range 15°C to 35°C, no special procedure qualifica-tion tests should be required. Outside the temperature range 15°C to 35°C, the procedureshall be qualified and a suitable comparator block shall be usedto compare indications from surface defects tested within andoutside the range during the procedure qualification.Reporting607 Reports shall be in accordance with B105 and B106.

B 700 Manual eddy current testing of weldsGeneral701 Eddy current testing shall be performed in compliancewith ISO 17643. The limitations given in ISO 17643, para-graph 6.3, notes 1 and 2 shall apply. 702 Eddy current testing shall be performed according toaccepted proceduresProcedure703 Eddy current testing procedures shall contain the infor-mation in B102 and:

— type of instrument— type of probe— frequency setting— calibration blocks and calibration details— surface condition requirements— scanning details— recording details.

Equipment704 Eddy current equipment, including probes and cables,shall be calibrated at maximum 6 months intervals and shallhave calibration certification pertaining to the characteristicsof the equipment.705 Functional checks of the eddy current equipment shallbe carried out whenever it has been out of function for any rea-son including on/off, and whenever there is any doubt concern-ing proper functioning of the equipment.706 All calibration blocks shall be marked with an identifi-cation that relates to the specific application of each block.Surface conditions707 Excess weld spatter, scale, rust and loose paint shall beremoved before the inspection.

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Application techniques708 ISO 17643 shall apply.Reporting709 Reports shall be in accordance with B105 and B106. Inaddition to the items listed in ISO 17643 the following shall beincluded in the testing report:


B 800 Visual examination of weldsGeneral801 Visual examination of welds shall be performed inaccordance with ISO 17637 and accepted procedures.802 Reports shall be in accordance with ISO 17637. In addi-tion to the items listed in ISO 17637 the following shall beincluded in the testing report:


B 900 Acceptance criteria for manual non-destructive testing of welds with nominal strains < 0.4% and no ECAGeneral901 The acceptance criteria given in Table D-4, Table D-5and Table D-6 are applicable for manual non-destructive test-ing of welds exposed to nominal strains < 0.4%.902 The acceptance criteria use the term defect to define animperfection/indication that has exceeded given dimensionsand thus is deemed unacceptable.903 The acceptance criteria given in Table D-5 assume thatmulti-pass welds are used and that the height of defects will notexceed 0.25 t or the height of a welding pass. The height of thewelding pass shall be assumed not to be more than 3 mm. Ifwelding methods resulting in higher welding passes are used(SAW, "one-shot" welding etc.), flaw indications equal orlarger than the length limits given in the tables shall be heightdetermined with ultrasonic testing. If the height exceeds 0.2 t,the defect is not acceptable unless proven to meet the accept-ance criteria for ultrasonic testing in Table D-6.Pipeline girth welds904 The acceptance criteria given in Table D-4, Table D-5and Table D-6 are generally applicable for manual non-destructive testing of pipeline girth welds exposed to totalnominal strains < 0.4%. 905 If the allowable defect sizes are established by an ECAfor pipeline girth welds exposed to total nominal strains≥ 0.4%, the provisions according to B1000 shall apply.Welds in pipeline components906 The acceptance criteria given in Table D-4, Table D-5 andTable D-6 are generally applicable for manual non-destructivetesting of welds in pipeline components. For girth welds con-necting a component to the pipeline or for pup-pieces welded tothe component, the acceptance criteria for pipeline girth weldsshall apply, unless other acceptance criteria are given in thedesign, manufacture and testing data for the component. 907 For welds exposed to total nominal strains ≥ 0.4%, theallowable defect sizes shall be established by an ECA and theprovisions according to B1000 shall apply.

B 1000 ECA based non-destructive testing acceptance criteria for pipeline girth weldsGeneral1001 Acceptance criteria for pipeline girth welds can bebased on an Engineering Critical Assessment (ECA)1002 Whenever acceptance criteria for NDT are establishedby an ECA, the ECA shall be performed in accordance with therequirements given in Appendix A.1003 If acceptance criteria for weld defects are based on anECA and hence involves sizing of indication height andlengths, manual ultrasonic testing or automated ultrasonic test-ing shall be performed.1004 Sizing of indication height and length by manual orautomated ultrasonic testing will have inherent inaccuracies.The allowable defect sizes derived from an ECA must accord-ingly be corrected for the ultrasonic testing uncertainty (sizingerror) as follows:

— If the ECA gives the allowable defect size the sizing errorshall be subtracted from the calculated allowable defectheight and length to establish the acceptance criteria fornon-destructive testing.

— If the ECA gives the material properties and stresses/strains allowed to tolerate a given defect size the sizingerror shall be added to the defect height and length used asinput into the ECA to establish the acceptance criteria fornon-destructive testing.

1005 If an embedded defect is located close to a surface,such that the ligament height is less than half the defect height,the ligament height between the defect and the surface shall beincluded in the defect height.Automated ultrasonic testing uncertainty data1006 If automated ultrasonic testing (AUT) is used for test-ing of pipeline girth welds, the uncertainty data used shall beobtained from the qualification testing of the automated ultra-sonic testing system required in Appendix E. Manual ultrasonic testing uncertainty data1007 For manual ultrasonic testing the data used for quanti-tative estimates of uncertainty performance and reliability inthe sizing of indication length and height, shall preferably beof the "measured response versus actual flaw size" type. Theestimates shall be based on published results from comprehen-sive studies into the reliability of manual ultrasonic testing. 1008 If adequate data for manual ultrasonic testing are notavailable, the sizing error shall not be taken as less than2.5 mm.Acceptance criteria based on ECA assessment1009 Appendix A gives requirements for establishing allow-able defect sizes based on an ECA assessment.1010 Acceptance criteria shall be established by correcting theallowable defect sizes derived from the ECA with the ultrasonictesting uncertainty in accordance with 1005 or 1006 and 1007.

Guidance note:Acceptance criteria based on ECA will frequently allow signifi-cantly larger indications than workmanship based acceptance cri-teria. In order to maintain a high standard of welding ECA basedallowable defect sizes may be used as a weld repair criterionrather than as acceptance criterion. Criteria that are more restric-tive are then used as a measure of the welding standard obtained.If these more restrictive criteria are exceeded, it should berequired that preventative or corrective actions are performed tomaintain the required welding standard.


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Table D-4 Acceptance criteria for visual examination and surface method testing of welds 1) 2)

Visual examinationExternal profile Welds shall have a regular finish and merge smoothly into the base material and shall not extend

beyond the original joint preparation by more than 3 mm (5 mm for SAW welds). Fillet welds shall be of specified dimensions and regular in form.

Cap and root reinforcement height(Longitudinal welds)

External welds: For t < 13 mm: max. 3.0 mm.For t ≥ 13 mm: max. 4.0 mm Internal welds: max. 3.5 mm

The radial offset of HFW linepipe shall not reduce the thickness at to weld to less than tmin.

Weld flash (HFW pipe longitudinal welds only)

The external flash shall be trimmed essentially flush with the pipe surface.The internal flash shall not extend above the contour of the pipe by more than 1.5 mm. The trim-ming shall not reduce the wall thickness to below tmin,and the groove resulting from the trimming shall have a smooth transition to the base material without notches and the depth shall be max. 0.3 mm + 0.05 t.

Cap and root reinforcement height(Double sided girth welds)

Height < 0.2 t, but max. 4 mm

Cap reinforcement (Single sided welds) Height < 0.2 t, but max. 4 mmRoot penetration (Single sided welds) Height < 0.2 t, but max. 3 mm. Length of excess penetration: max 25 mm Cap concavity Not permitted.Root concavity At no point shall the weld thickness be less than tmin Offset of strip/plate edges(Longitudinal welds)

For t ≤ 15 mm max. 1.3 mm For 15 mm < t ≤ 25 mm max. 0.1 tFor t > 25 mm max. 2.0 mm

For welds in clad/lined material the offset shall not reduce the effective thickness of the cladding/lining in the root area

High/low on root side of single sided girth welds

For t ≤ 13 mm max. 1.3 mmFor 13 mm < t ≤ 20 mm max. 0.1 t For t > 20 mm max. 2.0 mm

For welds in clad/lined material the offset shall not reduce the effective thickness of the cladding/lining in the root area

Transverse misalignment of weld beads for double sided welds

max. 3.0 mm for t ≤ 20 mm max. 4.0 mm for t > 20 mm

Waving bead (deviation of weld toe from a straight line)

max. 0.2 t, but max. 4 mm

Undercut Individual undercuts Accumulated length of undercuts in any 300 mm length of weld: Depth d Permitted length

d > 1.0 mm Not permitted None1.0 mm ≥ d > 0.5 mm 50 mm < 4 t, max. 100 mm.0.5 mm ≥ d > 0.2 mm 100 mmd < 0.2 mm unlimited unlimited

Cracks, Arc burns, Start/stop craters/ poor restart, Surface porosity

Not permitted.

Lack ofpenetration/lack offusion

Not permitted for welds in duplex stainless steel, CRAs and clad/lined steelIndividual acceptable length: t, max. 25 mm.Accumulated length in any 300 mm length of weld: t, max. 50 mm.

Systematic imperfections Imperfections that are distributed at regular distances over the length of the weld are not permit-ted even if the size of any single imperfection meets the requirements above

Burn through Not permitted for welds in duplex stainless steel, CRAs and clad/lined steel. Acceptable for welds in C-Mn and low alloy steels provided that weld thickness at no point is less than t and:

— Individual length/width: t/4, max. 4 mm in any dimension.— Accumulated length in any 300 mm length of weld: t/2, max. 8 mm.

Surface testing (MP, LP and EC)Wall thicknessmm

Type of indicationsRounded LinearNumber Dimension mm Number

≤ 16 2 4.0 2> 16 2 4.0 2Notes:

1) Any two imperfections separated by a distance smaller than the major dimension of the smaller imperfection shall be considered as a single imperfection.2) Detectable imperfections are not permitted in any intersection of welds.

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Table D-5 Acceptance criteria for radiographic testing of weldsType of defect Acceptance criteria 1) 2) 3)10)11)

Individual discontinuities Maximum accumulated size of in any 300 mm weld length for each type of discontinuity

Porosity1) 2)ScatteredCluster 5)WormholeHollow beadIsolated 6)On-line 7)

Diameter: < t/4, but max. 3 mmIndividual pore: <2 mm, cluster diameter max. 12 mmLength: t/2, but max. 12 mm, Width: t/10, but max. 3 mmLength: t, but max. 25 mm, Width: max. 1.5 mmDiameter: < t/4, max 3 mmDiameter: <2 mm group length: 2t, but max. 50 mm

See Note 4One cluster or total length < 12 mm2 wormholes or total length < 12 mmLength 2 t, but max. 50 mm-Length 2 t, but max. 50 mm

Slag 1) 2) 3) 8)IsolatedSingle linesParallel lines

Width < 3 mmWidth: max 1.5Individual width: max 1.5

Length 12 mm, but max. 4 off separated by min 50 mmLength 2 t, but max. 50 mmLength 2 t, but max. 25 mm

InclusionsTungstenCopper, wire

Diameter < 0.5 t, but max. 3 mmNot permitted

Max 2 off separated by min 50 mm-

Lack ofpenetration 1) 2) 3) 8)RootEmbedded 9)

Not permitted for welds in duplex stainless steel, CRAs and clad/lined steel -Length: t, but max. 25 mmLength: 2t, but max. 50 mm

Length t, but max. 25 mmLength 2 t, but max. 50 mm

Lack of fusion1) 2) 3) 8)

SurfaceEmbedded

Not permitted for welds in duplex stainless steel, CRAs and clad/lined steel

-

Length: t, but max. 25 mmLength: 2 t, but max. 50 mm

Length t, but max. 25 mmLength 2 t, but max. 50 mm

Cracks Not permitted -Shrinkage cavities and crater pipes

Not permitted -

Root concavity Length: 2t, but max. 50 mm Length: 2 t, but max. 50 mmRoot undercutExcess penetrationBurn through

See Table D-6 See Table D-6

Total accumulation of discontinuities (excluding porosity)

— Maximum accumulation of discontinuities in any 300 mm weld length 3 t, max 100 mm. — Maximum accumulation of discontinuities: 12% of total weld length.— Any accumulation of discontinuities in any cross sections of weld that may constitute a leak path or may reduce the effective weld thick-

ness with more than t/3 is not acceptable.Notes:

1) Refer to the additional requirements in 903 for welding methods that produce welding passes exceeding 0.25 t.2) Volumetric imperfections separated by less than the length of the smallest defect or defect group shall be considered as one imperfection.3) Elongated imperfection situated in a line and separated by less than the length of the shortest defect shall be considered as one imperfection.4) For single layer welds: 1.5% of projected area, for multi layer welds with t < 15 mm 2% of projected area, for multi layer welds with t ≥ 15 mm 3% of

projected area. 5) Maximum 10% porosity in cluster area.6) "Isolated" pores are separated by more than 5 times the diameter of the largest pore.7) Pores are "In a line" if not "Isolated" and if 4 or more pores are touched by a line drawn through the outer pores and parallel to the weld. "On-line" pores

shall be checked by ultrasonic testing. If ultrasonic testing indicates a continuous defect, the criteria for lack of fusion defect shall apply.8) Detectable imperfections are not permitted in any intersection of welds.9) Applicable to double sided welding where the root is within the middle t/3 only.10) Acceptance criteria of Table D-4 shall also be satisfied.11) Systematic imperfections that are distributed at regular distances over the length of the weld are not permitted even if the size of any single imperfection

meets the requirements above.

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B 1100 Repair of welds1101 A repaired weld shall normally be subject to the sametesting requirements and acceptance criteria as the original weld.1102 In cases when the acceptance criteria are based on anECA, specific acceptance criteria for repair welds shall be estab-lished by an ECA based on the fracture toughness propertiesobtained during qualification of the repair welding procedure. 1103 Repair welding of cracks is not permitted unless thecause of cracking has been established not to be a systematicwelding error. (If there is a crack in the weld, the weld is perdefinition considered rejected. This means a technical evalua-tion of the cause of cracking shall be performed. If it can bedemonstrated that the crack is a “one off” situation, then repairwelding may be performed subject to agreement).

C. Manual Non-destructive testing and Visual Examination of Plate, Pipe and Weld Overlay

C 100 General101 All non-destructive testing, visual inspection of plate,pipe and weld overlay shall be according to accepted proce-dures. Note that the requirements of C200 are not applicable toplate or pipe mills, see 201.102 Manual non-destructive testing and visual examinationprocedures shall be prepared as required in B102 through B104to reflect the requirements of the applied standard.103 Acceptance criteria for manual non-destructive testingand visual examination of plate, pipe and weld overlay aregiven in C600.

104 Manual non-destructive testing of plate, pipe and weldoverlay shall be performed in compliance with the standardslisted below and as required in the following:

ISO 10124 Seamless and welded (except submergedarc-welded) steel tubes for pressure pur-poses - Ultrasonic testing for the detec-tion of laminar imperfections

ISO 12094 Welded steel tubes for pressure purposes- Ultrasonic testing for the detection oflaminar imperfections in strips or platesused in manufacture of welded tubes

ASTM E165 Standard Test method for Liquid Pene-trant Inspection

ASTM E309 Standard Practice for Eddy-CurrentExamination of Steel Tubular productsUsing Magnetic Saturation

ASTM E426 Standard Practice for Electromagnetic(Eddy Current) of Welded and SeamlessTubular Products, Austenitic StainlessSteel and Similar Alloys

ASTM A578/578 Standard Specification for Straight-Beam Ultrasonic Examination of Plainand Clad Steel Plates for Special Appli-cations

ASTM A577/577 Standard specification for UltrasonicAngle-Beam Examination of Steel Plates

ASTM E 709 Standard Guide for Magnetic ParticleExamination

ASTM E 1417 Standard Practice for Liquid PenetrantExamination

ASTM E 1444 Standard Practice for Magnetic ParticleExamination.

Table D-6 Acceptance criteria for manual ultrasonic testing of welds 1) 2) 3) 4) 5) 6)

Base material thickness 8 mm ≤ t < 15 mm Base material thickness 15 mm ≤ t ≤ 150 mmMax. echo amplitude Corresponding acceptable indication

length, L (mm)Max. echo amplitude Corresponding acceptable indication

length, L (mm)Reference level (DAC) L ≤ t (but max. 8 mm) DAC + 4 dB L ≤ 0,5t (but max. 12,5 mm)DAC – 6 dB L > t (but max. 8 mm) DAC – 2 dB 0,5 t < L ≤ t (but max. 25 mm)- - DAC – 6 dB L > t (but max. 25 mm in both outer t/3)- - DAC – 6 dB L > t (but max. 50 mm in middle t/3)Cracks are not permitted.For welds in duplex stainless steel, CRAs and clad/lined steel: Lack of fusion and lack of penetration are not permitted.Transverse indications: Indications shall be considered as transverse if the echo amplitude transversely exceeds the echo amplitude from the same indication longitudinally with more than 2 dB. Transverse indications are unacceptable unless proven not to be planar, in which case the acceptance criteria for longitudinal indications apply.For indications approaching the maximum permitted length, it shall be confirmed that the indication height is less than 0.2 t or maximum 3 mm (see 903).If an embedded defect is located close to a surface, such that the ligament height is less than half the defect height, the ligament height between the defect and the surface shall be included in the defect height.Total accumulation of discontinuities: The total length of acceptable indications with echo amplitude of reference level – 6 dB and above shall not exceed 3 t, maximum 100 mm in any weld length of 300 mm nor more than 12% of total weld length. Any accumulation of defects in any cross section of weld that may constitute a leak path or reduce the effective thickness of weld more than t/3 is not acceptable.If only one side of the weld is accessible for testing 6 dB shall be subtracted from the maximum echo permitted above.Notes:

1) Reference level is defined as the echo amplitude corresponding to the echo from the reflector in the reference blocks described in Figure 1, Figure 2 and Figure 3 of this appendix, or equivalent reflector.

2) All indications exceeding 20% of the reference level shall be investigated to the extent that the operator determines the shape, length and location of the imperfection.

3) Indications that cannot be established with certainty shall whenever possible be tested with radiography. Indications that are type determined in this way shall meet the acceptance criteria in Table D-5.

4) Longitudinal imperfections where the echo height intermittently is below and above the acceptance level shall if possible be investigated with radiogra-phy. Indications that are determined in this way shall meet the acceptance criteria in Table D-5. If radiography cannot be performed, the length shall not exceed 3 t, maximum 100 mm in any weld length of 300 mm.

5) Length and depth shall be determined by an appropriate method, see B335 and B336.6) Detectable imperfections are not permitted in any intersection of welds.7) Systematic imperfections that are distributed at regular distances over the length of the weld are not permitted even if the size of any single imperfection

meets the requirements above.

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C 200 Plate and pipeGeneral201 These requirements are not applicable for plate and coilexamined at the plate/coil mill as covered by subsection G, orfor linepipe examined at the pipe mill as covered bysubsection H.General requirements for ultrasonic testing202 Ultrasonic equipment shall meet the requirements givenin B307 and B308.203 Probes used for testing of pipe and plate shall be charac-terised as required by ISO 10375 and ISO 12715. Angle shear-wave probes of 45º and 60º shall be used for C-Mn and low alloy steels. Angle probes for duplex stainlesssteel and austenitic steels shall be twin crystal (transmitter/receiver) compression-wave probes of 45º and 60º. Anglecompression wave probes shall and can only be used for scan-ning without skipping.Straight beam probes shall be single or twin crystal. Twin crys-tal probes shall be used when testing is performed on materialwith nominal thickness t < 60 mm. The focusing zone of thetwin crystal probes shall be adapted to the material thickness tobe examined. Single or twin crystal probes can be used when testing is per-formed on material with nominal thickness t ≥ 60 mm. The sin-gle crystal probes shall have a dead zone as small as possible,e.g. 10% of the material thickness or 15 mm whichever is thesmaller. Selected probes shall have a nominal frequency in therange of 2 MHz to 5 MHz and dimensions Ø 10 mm to Ø 25mm.204 The IIW or ISO calibration blocks (V1 – V2) accordingto ISO 2400 or ISO 7963 shall be used for calibration of rangescale and for angle determination. These calibration blocksshall, as near as practicable, have the same acoustic propertiesas the material to be tested.Manual ultrasonic thickness measurements205 Manual ultrasonic thickness measurements shall bedone in accordance with ASTM E797 or equivalent standard.Ultrasonic testing for detection of laminar flaws206 Manual ultrasonic testing for detection of laminar flawsin steel other than clad/lined steel shall be performed accordingto ISO 10124, ISO 12094 or equivalent standard.207 Manual ultrasonic testing for detection of laminar flawsin clad/lined steel shall be done in accordance with ASTMA578/578M or equivalent standard.208 The surface condition of the material shall permit at leasttwo successive back-wall echoes to be distinguished when theprobe is placed on any area free from internal imperfections. 209 The range scale shall be selected such that there arealways at least two back-wall echoes (reflections) on thescreen.210 The sensitivity shall be based on echoes reflected fromØ 6 mm flat bottom holes in reference blocks of the materialused or of a material with similar with acoustic properties. 211 DGS diagram or DGS- scales can be used provided theyare developed for the probe used and can be correlated to a Ø6 mm flat bottom hole.212 The pitch of the scanning grid shall be small enough toensure detection of the smallest defect allowed according tothe applicable acceptance criteria.213 Sizing of indications shall be performed according toISO 12094, Annex A.Manual ultrasonic testing for detection of transverse and lon-gitudinal flaws214 Manual ultrasonic testing for detection of transverse and

longitudinal flaws in plate and pipe shall be done in generalaccordance with ASTM A577 or equivalent standard.215 Probes shall meet the requirements of 203. Additionalangle probes will be required for testing of pipe. 216 Sensitivity for C-Mn and low alloy steel shall be a DACcurve based on reference blocks with a rectangular notch withdepth 3% of the material thickness on both sides.217 Reference blocks for duplex stainless steel and auste-nitic steels shall have one Ø 3 mm flat bottom hole perpendic-ular to the angle of incidence of the probe and at the largestpossible depth from the scanning surface of the block. Refer-ence blocks shall be of the actual material tested or of a mate-rial with similar with acoustic properties.218 Low frequency shear wave angle probes may be used forduplex stainless steel and austenitic steels instead of twin crys-tal (transmitter/receiver) compression-wave probes. Foracceptance, it shall be verified on the reference blocks that it ispossible to obtain a DAC with a shear wave angle probe that iscomparable to the DAC obtained with an angle compressionwave probe.219 The pitch of the scanning grid shall small be enough toensure detection of the smallest defect allowed according tothe applicable acceptance criteria.220 All reference blocks shall be marked with an identifica-tion that relates to the specific application of each block.Magnetic particle testing221 Manual magnetic particle testing of:

— plate— pipe— edges— bevels

shall be done in accordance with ASTM E 709, ASTM E1444or equivalent standard.Liquid penetrant testing222 Manual liquid penetrant testing of:

— plate— pipe— edges— bevels

shall be done in accordance with ASTM E165 or ASTM E1417or equivalent standard. The penetration and developing timesshall be long enough to allow effective detection of the small-est indications allowed.

Guidance note:The penetration time for water washable penetrants should nor-mally not be less than 20 - 30 minutes and for post-emulsifiedpenetrants not less than 10 - 15 minutes.


Eddy current testing223 Manual eddy current testing of C-Mn steel Pipe shall bedone in accordance with ASTM E309 or equivalent standard.Manual eddy current testing of duplex stainless steels andaustenitic stainless steels shall be done in accordance withASTM E426 or equivalent standard.

C 300 Weld overlay301 Manual magnetic particle testing of ferromagnetic weldoverlay deposits shall be performed in accordance with ASTME 709, ASTM E1444 or equivalent standard.302 Manual liquid penetrant testing of non-magnetic weldoverlay deposits shall be performed in accordance with ASTME 1417 or equivalent standard.

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303 Manual eddy current testing of weld overlay depositsshall be performed in accordance with ASTM E309 or equiva-lent standard.304 Manual ultrasonic testing of weld overlay shall be per-formed according to ISO 12094 or equivalent standard and:

— Straight beam probes shall be twin crystal. The focusingzone of the twin crystal probes shall be adapted to thematerial thickness to be examined.

— The surface condition of the material shall permit at leasttwo successive back-wall echoes to be distinguished whenthe probe is placed on any area free from internal imper-fections.

— The calibration of range scale shall be carried out using anIIW calibration block, a V2 calibration block or on adefect free area of known thickness in the material to beexamined. The range scale is to be selected such that thereare always at least 2 back-wall echoes (reflections) on thescreen.

— The sensitivity shall be based on echoes reflected from aØ 3 mm flat bottom hole in reference blocks made from abase material with similar acoustic properties of the actualbase material with overlay deposited according to thesame WPS as the actual overlay. The Ø 3 mm flat bottomhole shall be placed approximately at the fusion linebetween overlay and base material. If the testing shall beperformed of machined overlay, the scanning surface shallbe machined to the same surface requirements as the over-lay.

— All reference blocks shall be marked with an identificationthat relates to the specific application of each block.

Reporting 305 Reports shall be in accordance with B105 and B106.

C 400 Visual examination 401 Visual examination shall be carried out in a sufficientlyilluminated area; minimum 350 lx, but 500 lx is recommended.If required to obtain good contrast and relief effect betweenimperfections and background additional light sources shall beused. 402 For direct examination the access shall generally permitplacing the eye within 600 mm of the surface to be examinedand at an angle of not less than approximately 30°. If this is notpossible then the use of mirrors, boroscopes, fibre optics orcameras shall be considered.403 A sufficient amount of tools, gauges, measuring equip-ment and other devices shall be available at the place of exam-ination.404 The objects to be examined shall be cleaned to removeall scale and processing compounds prior to examination. Thecleaning process shall not injure the surface finish or mask pos-sible imperfections.405 Reporting of visual examination shall include:

— Name of manufacturer— Name of examining company— Identification of examined object(s)— Material— Imperfections exceeding the acceptance criteria and their

location— Extent of examination— Supplementary sketches/drawings.

C 500 Residual magnetism501 Residual magnetism shall be measured with a calibratedHall effect gauss meter or equivalent equipment. The residualmagnetism the residual magnetism shall not exceed an averagevalue (out of 4 measurements) of 2.0 mT (20 Gauss), with amaximum single value of 2.5 mT (25 Gauss). Some welding

methods may require a more stringent acceptance criterion. 502 Four readings shall be taken 90° apart around the cir-cumference of each end of the pipe, and at equal spacing forplate ends. The average of the four readings shall be ≤ 2.0 mT(20 Gauss), and no one reading shall exceed 2.5 mT (25Gauss). 503 Any product that does not meet the requirements of 502shall be considered defective. 504 All defective products shall be de-magnetized fulllength, and then their magnetism shall be re-measured until atleast three consecutive pipes meet the requirements of 502.505 The requirements for residual magnetism shall applyonly to testing at the specific location since the residual mag-netism in products may be affected by procedures and condi-tions imposed during and after handling and shipment.

C 600 Acceptance criteria for manual non-destructive testing of plate, pipe and weld overlayThickness measurements601 For manual ultrasonic thickness measurements accept-ance criteria shall be according to applicable specification orproduct standard.Laminar flaws602 Acceptance criteria for manual ultrasonic testing forlaminar flaws in C-Mn, low alloy, duplex, other stainless steelsand nickel based corrosion resistant alloys (CRA) are given inTable D-12.603 Acceptance criterion for manual ultrasonic testing fordetection of laminar flaws in clad steel is given in ASTMA578, S7. In addition, no areas with laminations or lack ofbonding are allowed over a width extending at least 50 mminside the location of future weld preparations.Transverse and longitudinal flaws604 For manual ultrasonic testing for detection of transverseand longitudinal flaws in C-Mn and low alloy steel, the accept-ance criterion shall be that no indications exceed the DACcurve established against the rectangular notch with depth 3%of the thickness.For manual ultrasonic testing for detection of transverse andlongitudinal flaws in duplex stainless steel, the acceptance cri-terion shall be that no indications exceed the DAC curve estab-lished against the Ø 3 mm flat bottom hole.Magnetic particle testing of plate / pipe bevels and edges605 Acceptance criterion for manual magnetic particle test-ing of plate / pipe bevels and edges shall be:

— No indications longer than 6 mm are permitted.

Liquid penetrant testing of plate / pipe bevels and edges606 Acceptance criterion for manual liquid penetrant testingof plate / pipe bevels and edges shall be:

— no indications longer than 6 mm are permitted.

Eddy current testing of plate / pipe bevels and edges607 Acceptance criterion for manual eddy current testing ofpipe / pipe bevels and edges shall be:

— no indications longer than 6 mm are permitted.

Disposition of defects at plate / pipe bevels and edges608 Defects at pipe bevels and edges shall be examinedultrasonically as required in this subsection and the pipes cutback until no defects are present in the tested area.Weld overlay609 Acceptance criteria for as-welded surfaces of magnetic

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and non magnetic weld overlay for visual examination, mag-netic particle testing, liquid penetrant and eddy current testingare:

— no round indications with diameter above 2 mm and noelongated indications

— indications separated by a distance less than the diameteror length of the smallest indication, shall be considered asone indication

— accumulated diameters of round indications in any100 × 100 mm shall not exceed 10 mm.

610 Acceptance criteria for ultrasonic testing of as-weldedsurfaces of magnetic and non-magnetic weld overlay shall beno loss of back wall echo and no echo from an indication shallexceed 66% of the echo reflected from Ø 3 mm flat bottomholes in reference blocks.611 For machined surfaces, acceptance criteria shall be espe-cially agreed upon.612 Defects shall be ground out, re-welded and re-tested tomeet the acceptance criteria above.

D. Non-destructive Testing and Visual Examination of Forgings

D 100 General101 All non-destructive testing of forgings shall be per-formed according to accepted procedures. 102 Manual non-destructive testing and visual examinationprocedures shall be prepared as required in B102 through B104to reflect the requirements of the applied standard.103 Acceptance criteria for manual non-destructive testingand visual examination forgings are given in D500.104 Manual non-destructive testing of forgings shall be per-formed in compliance with the standards listed below and asrequired in the following:

— ASTM E165Standard Test method for Liquid PenetrantInspection

— ASTM A388Specification for Ultrasonic Examination ofHeavy Steel Forgings

— ASTM E709 Standard Guide for Magnetic Particle Exam-ination

— ASTM A 961Standard Specification for CommonRequirements for Steel Flanges, Forged Fittings, Valves,and Parts for Piping Applications

— ASTM E 1417Standard Practice for Liquid PenetrantExamination

— ASTM E1444Standard Practice for Magnetic ParticleExamination

D 200 Ultrasonic and magnetic particle testing of C-Mn and low alloy steel forgingsUltrasonic testing201 Ultrasonic testing of forgings shall be performed inaccordance with ASTM A388 and the requirements below.Ultrasonic testing procedures202 Ultrasonic testing procedures shall contain the informa-tion in B102 and:

— type of instrument— type and dimensions of probes— range of probe frequencies— description of reference blocks— calibration details, range and sensitivity— surface requirements, including maximum temperature— type of coupling medium

— scanning techniques supplemented with sketches, show-ing the probes used and area covered by each probe

— description of methods for recheck of areas with reductionor loss of back reflection

— recording details.

Ultrasonic Apparatus203 Verification of Screen Height Linearity and AmplitudeLinearity shall be performed at the beginning of each period ofextended use (or every 3 months, whichever is less). Recordsshall be made available upon request.Probes204 Straight beam probes with frequency 2-5 MHz anddimension Ø 10-30 mm shall be used. The probes shall be sin-gle or twin crystal. Twin crystal probes shall be used when test-ing is performed on material with nominal thicknesst < 60 mm. The focusing zone of the twin crystal probes shallbe adapted to the material thickness to be examined. Single or twin crystal probes can be used when testing is per-formed on material with nominal thickness t ≥ 60 mm. The sin-gle crystal probes shall have a dead zone as small as possible,e.g. 10% of the material thickness or 15 mm whichever is thesmaller.205 Angle beam probes shall be used for testing on rings,hollow and cylindrical sections. Angle beam probes shall beavailable in angles, or be provided with wedges or shoes, rang-ing from 30° to 75°, measured to the perpendicular of the entiresurface of the forging being tested.Reference blocks for straight beam testing206 Supplementary requirement S1 of ASTM A388 shallapply, but with the following additional requirements:

— For material thickness t ≤ 38 mm the flat bottom holesshall be Ø 1.6 mm

— For material thickness 38 mm < t < 60 mm the flat bottomholes shall be Ø 3 mm

— For material thickness t ≥ 60 mm the flat bottom holesshall be Ø 6 mm.

Reference blocks for angle beam testing207 The reference notches shall be rectangular OD and IDnotches with a depth of:

— For material thickness t ≤ 38 mm, 3% of the thickness — For material thickness 38 mm < t < 100 mm, 5% of the

thickness— For material thickness t ≥ 100 mm, 10% of the thickness.

208 A separate reference block shall have the same configu-ration, nominal composition, forging ratio, heat treatment andthickness as the forgings it represents. 209 Where a group of identical forgings is made, one of theforgings may be used as the separate reference block.210 All reference blocks shall be marked with an identifica-tion that relates to the specific application of each block.Preparation of forgings for ultrasonic testing211 For forgings of uncomplicated geometry, the require-ments of ASTM A388, chapter 6 shall apply.Forgings of complex geometry212 Forgings are required to be forged and/or to be roughmachined to near final dimensions prior to heat treatment inorder to obtain the required properties. This machining of forg-ings shall consider that cylindrical shapes and faces that are flatand parallel to one another shall be obtained in order to provideadequate conditions for ultrasonic testing. In the case of forg-ings with complex geometry, machining shall provide inter-secting

DET NORSKE VERITAS


cylindrical and/or flat faces. The machining shall be such thatareas where adequate ultrasonic testing is not possible will beremoved during the final machining. A sketch shall be pro-vided for acceptance showing the areas of the forging whereadequate ultrasonic testing will not be achieved.Calibration of amplification and testing procedure213 The IIW or ISO calibration blocks (V1 – V2) accordingto ISO 2400 or ISO 7963 shall be used for calibration of rangescale and for angle determination. These calibration blocksshall, as near as practicable, have the same acoustic propertiesas the material to be tested. Calibration of range scale can alter-natively be done on a defect free area of known thickness in thematerial to be examined. The range scale is to be selected suchthat there are always at least 2 back-wall echoes (reflections)on the screen.214 The calibration of the required amplification shall beperformed according to ASTM A388, chapter 7. The probesize and frequency that provides optimum response shall beused for the testing.215 Notes 2 and 3 of, chapter 7 in ASTM A388 shall beadhered to.216 When scanning, the gain shall increased by minimum6 dB above the corrected primary gain. For evaluation of indi-cations the gain shall be reduced by the increased dB level usedduring scanning.217 The method for re-check of areas with reduction or lossof back reflection, ASTM A 388, paragraph 7.2.4, shall bedescribed.218 Different frequencies, types, angles and diameter ofprobes shall be employed to obtain additional informationabout detected indication.Sizing of indications219 In general, the area containing imperfections shall besized (area and length) using the 6 dB drop technique. The arearefers to the surface area on the forgings over which a contin-uous indication exceeds the acceptance criteria. This area willbe approximately equal to the area of the real defect providedthe defect size is larger than the 6 dB beam profile of the probe.220 If the real imperfection size is smaller than the 6 dBbeam profile, the 6 dB drop technique is not suited for sizing.The area measured on the surface will be measured too largeand not represent the real indication size. A guide to classify ifthe revealed indications are greater or smaller than the 6 dBdrop profile is given in EN 10228-3, part 13. 221 If the size of the indication is evaluated to be smallerthan the 6 dB drop profile at the depth of discontinuity agraphic plot, that incorporates a consideration of beam spreadshould be used for realistic size estimation.

Periodical checks of equipment222 At approximately four-hourly intervals and at the end oftesting, the range scale, probe angle and primary gain must bechecked and if necessary, corrected. Checks shall also be car-ried out whenever a system parameter is changed or changes inthe equivalent settings are suspected. If deviation is found to belarger than 2% of range scale, or 3 dB of primary gain settingor 2º of nominal angle probe, the testing carried out with theequipment over the previous period shall be repeated. Reporting223 Reports shall be in accordance with B105 and B106 andASTM A388, chapter 9.Manual magnetic particle testing of C-Mn steel forgings224 Manual magnetic particle testing of C-Mn steel forgingsshall be performed in accordance with ASTM E 709, ASTME1444 or equivalent standard.

D 300 Ultrasonic and liquid penetrant testing of duplex stainless steel forgingsUltrasonic testing301 Ultrasonic testing of duplex stainless steel forgings shallbe performed in accordance with D200, but with the followingadditions to the requirements to:

— probes— reference blocks for angle beam testing— preparation of forgings for ultrasonic testing — testing procedure.

Angle probes302 Angle probes for duplex stainless steel shall be twincrystal (transmitter/receiver) compression-wave probes. Anglecompression wave probes shall and can only be used withoutskipping.303 Low frequency shear wave angle probes may be used forduplex stainless steel instead of twin crystal (transmitter/receiver) compression-wave probes, provided it is verified onthe reference blocks that it is possible to obtain a DAC with ashear wave angle probe that is comparable to the DACobtained with an angle compression wave probe.304 Creep wave probes shall be used for detection of sub sur-face defects close to the scanning surface, unless testing can beperformed from both sides.Reference blocks for angle beam testing305 Reference blocks for angle beam testing of duplex stain-less steel with angle compression wave probes shall have sidedrilled holes and a 1 mm deep and 20 mm wide spark erodednotch according to Figure 4 and Table D-7.

Figure 4 Reference block for construction of DAC, duplex stainless steel

DET NORSKE VERITAS


Preparation of forgings for ultrasonic testing306 The machining of duplex stainless steel forgings forultrasonic testing shall take into account that angle compres-sion wave probes shall and can only be used without skipping.Testing procedure307 The testing procedure for duplex stainless steel forgingsshall take into account that angle compression wave probesshall and can only be used without skipping. The testing shallhence be performed from as many faces that access permits.Manual liquid penetrant testing of duplex stainless steel forg-ings308 Manual liquid penetrant testing of duplex stainless steelforgings shall be performed in accordance with ASTM E 1417or equivalent standard. Post-emulsified penetrants should bepreferred. The penetration and developing times shall be longenough to allow effective detection of the smallest indicationsallowed.

Guidance note:The penetration time for water washable penetrants should not beless than 35 - 45 minutes and for post-emulsified penetrants notless than 10 - 15 minutes.


309 Reports shall be in accordance with B105 and B106 andASTM A388, chapter 9.

D 400 Visual examination of forgings401 Visual examination of forgings shall be performed inaccordance with C400, with acceptance criteria according toD500.

D 500 Acceptance criteria for forgings501 Acceptance criteria for manual ultrasonic testing offorgings shall be:Straight beam testing

— No single indication shall be larger than the indicationreceived from the flat bottom holes in the reference blockrequired in D200.

Angle beam testing of C-Mn and low alloy steel forgings

— No single indication shall exceed a DAC curve establishedusing the notches in the reference block required in D200.

Angle beam testing of duplex stainless steel forgings

— No single indication shall exceed a DAC curve establishedusing the side drilled holes in the reference Multiple indi-cations

— No indications within 13 mm of each other in any directionshall exceed 50% of the reference curve.

Acceptance criteria for manual magnetic particle testing of C-Mn and low alloy steel forgings502 Acceptance criteria for manual magnetic particle testingof C-Mn and low alloy steel forgings shall be according toTable D-8.Acceptance criteria for manual liquid penetrant testing ofduplex stainless steel forgings503 Acceptance criteria for manual liquid penetrant testingof duplex stainless steel forgings done in accordance withASTM E1417 or equivalent standard shall be according toTable D-8.

Acceptance criteria for visual examination504 Acceptance criteria for visual examination of forgingsshall be in accordance with ASTM A 961, Chapter 15. If thesurface imperfections acceptable under 15.5 are not scattered,i.e. more than 3 off in any 100 x 150 mm area, such imperfec-tions shall be considered injurious.

E. Non-destructive Testing and Visual Examination of Castings

E 100 General101 All non-destructive testing of castings shall be doneaccording to accepted procedures. 102 Manual non-destructive testing and visual examinationprocedures shall be prepared as required in B102 through B104to reflect the requirements of the applied standard.103 Acceptance criteria for manual non-destructive testingand visual examination of castings are given in E600.104 Manual non-destructive testing of castings shall be per-formed in compliance with the standards listed below and asrequired in the following:

E 200 Ultrasonic and magnetic particle testing of C-Mn and low alloy steel castings201 Manual ultrasonic testing of castings shall be doneaccording to ASTM A609, procedure A, and Supplementary

Table D-7 Reference Block DimensionsMaterial thickness (t) Thickness

of referenceblock (T)

Diame-ter ofside drilledhole mm

Position ofside drilledholes

T < 20 mm 15 mm or t 2.4 ± 0.2 T/4, T/2 and T3/420 mm ≤ t < 35 mm 20 mm or t 3.0 ± 0.235 mm ≤ t < 75 mm 50 mm or t75 mm ≤ t < 100 mm 90 mm or t 6.0 ± 0.2 The distance

between the two outer holes and the nearest surface shall not exceed 12 mm

100 mm ≤ t < 150 mm 125 mm or tTable D-8 Acceptance criteria for manual magnetic particle and liquid penetrant testing of forgings A Crack-like indications: not permittedB Linear indications with length more than 2 mm or three times

the width: not permitted. Linear indications with length < 1.5 mm may be deemed irrelevant

C Rounded indications: Diameter < 3 mm, accumulated diame-ters in any 100 x150 mm area < 8 mm.

ASTM E165 Standard Test method for Liquid Penetrant Inspection

ASTM A609 Standard Practice for Castings, Low Alloy, and Martensitic Stainless Steel, Ultrasonic Examination Thereof.

ASTM E709 Standard Guide for Magnetic Particle Exam-ination

ASTM E 1417 Standard Practice for Liquid Penetrant Examination

ASTM E1444 Standard Practice for Magnetic Particle Examination

ASME Boiler and Pressure Vessel Code, Section V, Article 2.

MSSSP-55 Quality standard for steel castings for valves, flanges, and fittings and other piping compo-nents (visual method).

DET NORSKE VERITAS


requirement S1. In addition the requirements below apply.Ultrasonic testing procedures202 Ultrasonic testing procedures shall contain the informa-tion in B102 and:

— type of instrument— type and dimensions of probes— range of probe frequencies— description of reference blocks— calibration details, range and sensitivity— surface requirements, including maximum temperature— type of coupling medium— scanning techniques supplemented with sketches, show-

ing the probes used and area covered by each probe — description of methods for re-check of areas with reduc-

tion or loss of back reflection— recording details.

Ultrasonic Apparatus203 Verification of Screen Height Linearity and AmplitudeLinearity shall be performed at the beginning of each period ofextended use (or every 3 months, whichever is less). Recordsshall be made available upon request.Probes204 Straight beam (normal) probes with frequency 1-5 MHzand dimension Ø 10-30 mm shall be used. Straight beam, nor-mal probes shall be single or twin crystal. Twin crystal probesshall be used when testing is performed on material with nom-inal thickness t < 60 mm. The focusing zone of the twin crystalprobes shall be adapted to the material thickness to be exam-ined. 205 Single or twin crystal probes can be used when testing isperformed on material with nominal thickness t ≥ 60 mm. Thesingle crystal probes shall have a dead zone as small as possi-ble, e.g. 10% of the material thickness or 15 mm whichever isthe smaller.Reference blocks 206 All reference blocks shall be marked with an identifica-tion that relates to the specific application of each block.Casting conditions for ultrasonic testing207 Castings shall as far as possible be machined accordingto D211 and D212.Calibration of amplification and testing procedure208 The IIW or ISO calibration blocks (V1 – V2) accordingto ISO 2400 or ISO 7963 shall be used for calibration of rangescale and for angle determination. These calibration blocksshall, as near as practicable, have the same acoustic propertiesas the material to be tested. Calibration of range scale can alter-natively be done on a defect free area of known thickness in thematerial to be examined. The range scale is to be selected suchthat there are always at least 2 back-wall echoes (reflections)on the screen.209 The calibration of the required amplification shall beperformed according to ASTM A609, chapter 8 and S1. Theprobe size and frequency that provides optimum response shallbe used for the testing.210 Note 3 of ASTM A609, chapter 8: When scanning, thegain shall be increased by minimum 6 dB above the correctedprimary gain. For evaluation of indications the gain shall bereduced by the increased dB level used during scanning.211 Rechecks shall be performed if the loss of back reflec-tion is 50% or greater. The method for further investigation ofareas with reduction or loss of back reflection, ASTM A 609paragraph 8.5, shall be described.212 Different frequencies, types, angles and diameter ofprobes shall be employed to obtain additional information

about detected indicationSizing of indications213 In general, the area containing imperfections, shall besized (area and length) using the 6 dB drop technique. The arearefers to the surface area on the castings over which a continu-ous indication exceeds the acceptance criteria. This area willbe approximately equal to the area of the real defect providedthe defect size is larger than the 6 dB beam profile of the probe.214 If the real imperfection size is smaller than the 6 dBbeam profile, the 6 dB drop technique is not suited for sizing.The area measured on the surface will be measured too largeand not represent the real indication size. A guide to classify ifthe revealed indications are greater or smaller than the 6 dBdrop profile is given in EN 10228-3, part 13. 215 If the size of the indication is evaluated to be smallerthan the 6 dB drop profile at the depth of discontinuity, agraphic plot that incorporates a consideration of beam spreadshould be used for realistic size estimation.Periodical checks of equipment216 At approximately four-hourly intervals and at the end oftesting, the range scale, probe angle and primary gain must bechecked and corrected. Checks shall also be carried out when-ever a system parameter is changed or changes in the equiva-lent settings are suspected. If deviation is found to be largerthan 2% of range scale, or 3 dB of primary gain setting or 2º ofnominal angle probe, the testing carried out with the equip-ment over the previous period shall be repeated. Reporting217 Reports shall be in accordance with B105, B106, andASTM A609, chapters 9 and 19. All indications exceeding50% of the DAC shall be reported.Manual magnetic particle testing of C-Mn and low alloy steelcastings218 Manual magnetic particle testing of C-Mn steel castingsshall be performed in accordance with ASTM E 709, ASTME1444 or equivalent standard.219 Reports shall be in accordance with B105 and B106.

E 300 Ultrasonic and liquid penetrant testing of duplex stainless steel castingsUltrasonic testing301 Ultrasonic testing of duplex stainless steel castings shallbe performed in accordance with E200, but with the followingadditions to the requirements to:

— probes— reference blocks for angle beam testing— casting conditions for ultrasonic testing — testing procedure.

Angle probes302 Angle probes for duplex stainless steel shall be twincrystal (transmitter/receiver) compression-wave probes. Anglecompression wave probes shall and can only be used withoutskipping.303 Low frequency shear wave angle probes may be used forduplex stainless steel instead of twin crystal (transmitter/receiver) compression-wave probes, provided it is verified onthe reference blocks that it is possible to obtain a DAC with ashear wave angle probe that is comparable to the DACobtained with an angle compression wave probe.304 Creep wave probes shall be used for detection of sub sur-face defects close to the scanning surface, unless testing can beperformed from both sides.Reference blocks for angle beam testing305 Reference blocks for angle beam testing of duplex stain-

DET NORSKE VERITAS


less steel with angle compression wave probes shall have sidedrilled holes and a 1 mm deep and 20 mm wide spark erodednotch according to Figure 4 and Table D-7. Casting conditions for ultrasonic testing 306 Duplex steel stainless castings shall be machinedaccording to D211 and D212.307 The machining of duplex stainless steel castings forultrasonic testing shall take into account that angle compres-sion wave probes shall and can only be used without skipping.Testing procedure308 The testing procedure for duplex stainless steel castingsshall take into account that angle compression wave probesshall and can only be used without skipping. The testing shallhence be performed from as many faces that access permits.Manual liquid penetrant testing of duplex stainless steel cast-ings309 Manual liquid penetrant testing of duplex stainless steelcastings shall be performed in accordance with ASTM E 1417or equivalent standard. Post-emulsified penetrants should beused on precision castings only. The penetration and develop-ing times shall be long enough to allow effective detection ofthe smallest indications allowed.

Guidance note:The penetration time for water washable penetrants should not beless than 35 - 45 minutes and for post-emulsified penetrants notless than 10 - 15 minutes.


310 Reports shall be in accordance with B105 and B106.

E 400 Radiographic testing of castingsGeneral401 Radiographic testing of castings shall be done accordingto ASME Boiler and Pressure Vessel Code, Sec.7, article 2 orequivalent standard. In addition, the applicable requirementsof B200 and the requirements below shall apply.Procedures402 Radiographic procedures shall in addition to the require-ments of B203, give the following information:

— shooting sketches— coverage— source location— location of IQI— acceptance criteria.

E 500 Visual examination of castings501 Visual examination of castings shall be performed inaccordance with C400 and MSS SP-55. 502 Reports shall be in accordance with C405.

E 600 Acceptance criteria for castingsGeneral601 Acceptance criteria shall apply for the entire casting orportions of the casting. If different acceptance criteria shallapply for different portions of the casting, the critical areas ofthe casting shall be defined.

Guidance note:Critical areas shall include abrupt changes of sections and at thejunctions of risers, feeders and gates to the casting. Highlystressed areas such as weld necks shall be considered as criticalareas.


602 Acceptance criteria for manual ultrasonic straight beamtesting of castings shall be:

— No crack-like indications are acceptable, and— According to Table D-9.

603 Acceptance criteria for manual radiographic testing ofcritical areas of castings shall be according to Table D-10:

604 Acceptance criteria for manual magnetic particle testingand manual liquid penetrant testing of castings shall be accord-ing to Table D-11.

605 Acceptance criteria for visual inspection of castingsshall be in accordance with MSS SP-055.

— Type 1: Not acceptable— Types 2 through 12: A and B.

Repairs by welding606 Complete removal of the defect shall be confirmed bymagnetic particle testing, or liquid penetrant testing for non-ferromagnetic materials, before re-welding.607 Repair welds of castings shall meet the acceptance crite-ria designated for the particular portion of the casting.

F. Automated Non-Destructive TestingF 100 General101 These requirements are applicable to all automated NDTprocesses except automated ultrasonic testing of girth weldswhere specific requirements are given in Appendix E. Therequirements given in this subsection are additional to therequirements of any code or standard where automated NDTmethods are prescribed or optional.102 Automated non-destructive testing can replace manualnon-destructive testing or one automated non-destructive testingmethod/system can replace another automated non-destructivetesting method/system provided the equivalence of systems isdocumented with regard to function, operation, ability in detec-

Table D-9 Ultrasonic testing acceptance criteria for castingsStraight beam testingASTM A609, 10.2.1, 10.2.2 and 10.2.3 Critical areas Other areasTable 2, Quality Level 1 Table 2, Quality Level 3Angle beam testingASTM A609 S1.4.1 and Table 2Critical areas Other areasTable 2, Quality Level 1 Table 2, Quality Level 3

Table D-10 Radiographic acceptance criteria for castingsType of defect Acceptance criteria

Standard Maximum Severity LevelGas porosity

ASTM E280

2Inclusions 2Shrinkage 2Cracks 0Hot tears 0Inserts 0

Table D-11 Acceptance criteria for manual magnetic particle and liquid penetrant testing of castingsA Crack-like defects: not permittedB Linear indications with length more than three times the

width: not permitted. Linear indications with length < 1.5 mm may be deemed irrel-evant.

C Rounded indications: Diameter < 3 mm, accumulated diame-ters in any 100 × 150 mm area < 8 mm.

DET NORSKE VERITAS


tion and sizing and performance.103 Documentation of capability/performance and qualifica-tion of automated NDT systems in pipe mills will normally notbe required for systems meeting the documentation require-ments given in H404.

F 200 Documentation of function and operationThe automated NDT equipment shall be documented withregard to function and operation. Items subject to documenta-tion include:

— brief functional description of the equipment— detailed equipment description— operation manual including type and frequency of func-

tional checks— calibration— limitations of the equipment with regard to material or

weld features including size, geometry, type of flaws, sur-face finish, material composition etc.

— repeatability.

F 300 Documentation of performance301 The capability and performance of automated NDTequipment shall be documented by statistical records covering,as relevant:

— accuracy in indication sizing (random and systematicdeviation)

— accuracy in positioning / location— defect characterisation abilities compared to the results of

other NDT performed— repeatability, and— probability of detection values or data for different thresh-

old settings to determine the threshold to be used forrequired detection during testing.

Guidance note:Automated non-destructive testing equipment can generally bedivided into two groups. One group consists of equipmentintended for detection, sizing and positioning of indications (typ-ically real time radiography) and one group consisting of equip-ment intended for detection only and where sizing andpositioning of indications is performed by other means (typicallyultrasonic testing of the weld seam according to ISO 9765). Forthe latter types of equipment, documentation of performancemay be limited to demonstration of adequate detection of defectstypical for the manufacturing process, threshold setting parame-ters and repeatability.


F 400 Qualification401 A full qualification programme for automated NDTequipment will in general comprise the following stages:

— initial evaluation and conclusions based on availableinformation

— identification and evaluation of significant parameters andtheir variability

— planning and execution of a performance test programme— reference investigations.

F 500 Evaluation of performance documentation501 As a minimum a qualification will involve an assess-ment of the automated NDT equipment technical documenta-tion, including the quality assurance system, and availableinformation on equipment capability and performance. Lim-ited practical tests must be performed in many cases.

G. Non-Destructive Testing at Plate and Coil Mill

G 100 General101 The non-destructive testing during manufacture of plateand coil shall be performed according to documented proce-dures.102 The testing shall include testing of a band along the fouredges of plate for laminar imperfections. A suitable allowancein the width of the band shall be made to compensate for pos-sible oversized plates and subsequent edge milling and endbevelling. 103 Testing of coil, e.g. for HFW pipe, may alternatively besubstituted with testing of finished pipe at the pipe mill.104 The width of the band at the longitudinal plate edgesshall extend:

— at least 50 mm inside the location of future welding prep-arations for SAW longitudinal welds

— At least 15 mm inside the location of future welding prep-arations for HFW longitudinal welds.

105 The width of the band at the transverse plate edges shallnormally extend:

— at least 50 mm inside the location of future welding prep-arations for girth welds.

Additional non-destructive testing106 Any additional non-destructive testing shall be specifiedby the purchaser.107 If automated ultrasonic testing of girth welds duringinstallation will be performed the width of the band shouldextend at least 150 mm inside the location of future weldingpreparations for girth welds.108 If allowance for re-bevelling of pipe shall be included,the width of the band should extend at least 100 mm inside thelocation of future welding preparations for girth welds.109 For detection of cracks angle probes shall be used to sup-plement the straight beam probes. Testing shall be in generalaccordance with ASTM A577 or equivalent standard and:

— Probes shall meet the requirements of C203.— Sensitivity for C-Mn steel shall be a DAC curve based on

reference blocks with a rectangular notch with depth 3%of the material thickness on both sides.

— Reference blocks for duplex stainless steel and austeniticsteels shall have one Ø3 mm flat bottom hole perpendicu-lar to the angle of incidence of the probe and at the largestpossible depth from the scanning surface of the block. Ref-erence blocks shall be of the actual material tested or of amaterial with similar with acoustic properties.

— Low frequency shear wave angle probes may be used forCRA material instead of twin crystal (transmitter/receiver)compression-wave probes. For acceptance, it shall be ver-ified on the reference blocks that it is possible to obtain aDAC with a shear wave angle probe that is comparable tothe DAC obtained with an angle compression wave probe.

110 The acceptance criterion is:

— No indications shall exceed the DAC.

G 200 Ultrasonic testing of C-Mn steel and CRA plates201 Ultrasonic testing for laminar imperfections shall be inaccordance with ISO 12094 amended as follows:

— the distance between adjacent scanning tracks shall be suffi-ciently small to ensure detection of the minimum imperfec-tion size to be considered in the plate body and all four edges

DET NORSKE VERITAS


202 Acceptance criteria for ultrasonic testing of C-Mn andduplex steel plate for laminar imperfections are given in TableD-12.

203 Subject to agreement the acceptance criteria for the bodyof plate and coil can be limited to an allowed permitted area of100 mm2 and a population density of 5 and with the minimumimperfection size area 30 mm2, length and width 5 mm. Allother requirements in Table D-12 shall apply.

G 300 Ultrasonic testing of CRA clad C-Mn steel plate 301 For ultrasonic testing of the backing material therequirements of G100 and G200 shall apply.302 Ultrasonic testing for the detection of lack of bondbetween the C-Mn backing material and CRA shall be per-formed in accordance with ASTM A578, S7 amended as fol-lows:

— the distance between adjacent scanning tracks shall be suf-ficiently small to ensure detection of the minimum imper-fection size to be considered in the plate body and all fouredges.

303 Acceptance criteria are:

— ASTM A578, S7. In addition, no areas with laminations orlack of bond are allowed in the plate edge areas.

G 400 Alternative test methods401 If agreed alternative methods of testing may be accepta-ble, if the alternative test method is documented as required inH402 and the alternative test method is demonstrated to give atleast the same sensitivity and capability in detection of imper-fections.

402 The demonstration of the alternative test method shall bebased on the principles given in Subsection F and using sam-ples of plate similar to those ordered. The plates shall containa representative and agreed size range of natural and/or artifi-cial defects of types that are typical for the manufacturingprocess in question.

G 500 Disposition of plate and coil with unacceptable laminations or inclusions501 Plates and coil that contain unacceptable laminations orinclusions shall be rejected or, if possible, be cut back until nolamination or inclusion exceeding the acceptance criteria ispresent in the plate/coil.

G 600 Visual examination of plate and coil601 Visual examination shall be carried out in a sufficientlyilluminated area, minimum 350 lx, but 500 lx is recommended.If required to obtain good contrast and relief effect betweenimperfections and background additional light sources shall beused. 602 For direct examination the access shall generally permitplacing the eye within 600 mm of the surface to be examinedand at an angle of not less than approximately 30°. 603 A sufficient amount of tools, gauges, measuring equip-ment and other devices shall be available at the place of exam-ination.604 The objects to be examined shall be cleaned to removeall scale and processing compounds prior to examination. Thecleaning process shall not injure the surface finish or mask pos-sible imperfections.

G 700 Acceptance criteria and disposition of surface imperfectionsAcceptance criteria701 Plate/coil shall meet the acceptance criteria specified bythe pipe mill. The acceptance criteria shall under no circum-stance be less stringent than the applicable requirements forpipe, as specified in H500.702 Imperfections shall be dressed out by grinding. Groundareas shall blend smoothly into the surrounding material. Com-plete removal of defects shall be verified by local visualinspection and, if necessary, aided by suitable NDT inspectionmethods. The remaining wall thickness in the ground area shallbe checked by ultrasonic wall thickness measurements to ver-ify that the thickness of the remaining material is more than thespecified minimum. Imperfections that encroach on the mini-mum permissible wall thickness after grinding shall be classi-fied as defects.Disposition of plate with defects703 Plate and coil that contain defects shall be rejected or, ifpossible, be cut back until no defect is present in the plate/coil.

H. Non-Destructive Testing of Linepipe at Pipe Mills

H 100 General101 The extent of non-destructive testing during manufac-ture of linepipe shall be as required in Sec.7 F.102 The types of testing required are defined as:

— ultrasonic testing— surface imperfection testing— radiographic testing.

Whenever the choice of non-destructive testing methods isoptional, this is indicated in this subsection.

Table D-12 Ultrasonic testing, acceptance criteria for laminar imperfections

Acceptance criteria for bodyService Maximum

allowed imperfection

Minimum imperfection size to be considered

Size of reference area

Maximum population density

Non-sour

Area:1 000 mm2

Area: 300 mm2Length: 35 mmWidth: 8 mm

1 000 mm × 1 000 mm

10within thereference area

Sour Area: 500 mm2

Area: 150 mm2Length: 15 mmWidth: 8 mm

500 mm×500 mm


Acceptance criteria for edgesService Maximum

allowedimperfection

Minimum size of imperfection to be considered

Size of reference area

Maximum population density

All Area: 100 mm2Width: 6 mm

Length: 10 mm 1 000 mm length


Notes:

1) For an imperfection to be larger than the minimum imperfection to be considered, all dimensions, e.g. min area, min length and min width, will have to be exceeded (for body).

2) Two or more adjacent imperfections shall be considered as one imper-fection if they are separated by less than the smaller dimension of either indication.

3) The population density shall be the number of imperfections smaller than the maximum allowed and larger than the minimum imperfection size to be considered

4) The reference area for plate/coil when the plate width is less than one side of the square reference area shall be 1.00 m2 for non-sour and 0.25 m2 for sour service.

5) The width of an imperfection is the dimension transverse to the longi-tudinal edge of the plate/coil or for pipe the longitudinal axis.

DET NORSKE VERITAS


103 Non-destructive testing shall be performed in compli-ance with the standards listed below and as required in thissubsection:Electromagnetic (flux leakage)

ISO 9402 Seamless and welded (except submerged arcwelded) steel tubes for pressure purposes - Fullperipheral magnetic transducer/ flux leakagetesting of ferromagnetic steel tubes for thedetection of longitudinal imperfections

ISO 9598 Seamless steel tubes for pressure purposes - Fullperipheral magnetic transducer/flux leakagetesting of ferromagnetic steel tubes for thedetection of transverse imperfections

Electromagnetic (eddy current)

ISO 9304 Seamless and welded (except submerged arc-welded) steel tubes for pressure purposes - Eddycurrent testing for the detection of imperfections

Radiographic

ISO 12096 Submerged arc-welded steel tubes for pressurepurposes - Radiographic testing of the weldseam for the detection of imperfections.

Ultrasonic

ISO 9303 Seamless and welded (except submerged arc-welded) steel tubes for pressure purposes - Fullperipheral ultrasonic testing for the detection oflongitudinal imperfections

ISO 9305 Seamless tubes for pressure purposes - Fullperipheral ultrasonic testing for the detection oftransverse imperfections

ISO 10124 Seamless and welded (except submerged arc-welded) steel tubes for pressure purposes -Ultrasonic testing for the detection of laminarimperfections

ISO 10543 Seamless and hot-stretch reduced welded steeltubes for pressure purposes - Full peripheralultrasonic thickness testing

ISO 11496 Seamless and welded steel tubes for pressurepurposes - Ultrasonic testing of tube ends for thedetection of laminar imperfections

ISO 13663 Welded steel tubes for pressure purposes - Ultra-sonic testing of the area adjacent to the weldseam body for detection of laminar imperfec-tions

ISO 12094 Welded steel tubes for pressure purposes - Ultra-sonic testing for the detection of laminar imper-fections in strips or plates used in manufactureof welded tubesUltrasonic (weld seam)

ISO 9764 Electric resistance welded steel tubes for pres-sure purposes - Ultrasonic testing of the weldseam for longitudinal imperfections

ISO 9765 Submerged arc-welded steel tubes for pressurepurposes - Ultrasonic testing of the weld seamfor the detection of longitudinal and/or trans-verse imperfections

Liquid penetrant

ISO 12095 Seamless and welded steel tubes for pressurepurposes - Liquid penetrant testing

Magnetic particle

ISO 13664 Seamless and welded steel tubes for pressurepurposes - Magnetic particle inspection of tubeends for the detection of laminar imperfections

ISO 13665 Seamless and welded steel tubes for pressurepurposes - Magnetic particle inspection of tubebody for the detection of surface imperfections

104 All NDT shall be performed according to documentedprocedures that, as a minimum, give information on the fol-lowing aspects:

— applicable code(s) or standard(s)— welding method (when relevant)— joint geometry and dimensions (when relevant)— material— NDT method— technique— equipment, main and auxiliary— consumables when relevant (including brand name)— coverage calculation supplemented with sketches— sensitivity— calibration references and technique— trigger or alarm settings— for ultrasonic testing equipment the procedure shall

describe the method for setting and checking the lack ofcoupling alarm

— assessment of imperfections— method for demonstrating compliance of equipment with

the assumptions in the procedure— reporting and documentation of results.

105 Personnel performing NDT shall be qualified accordingto A500.106 All NDT for final acceptance of pipe shall be performedafter completion of any cold expansion and heat treatmentoperations. For seamless pipe, the NDT for final acceptance may be per-formed prior to cropping, bevelling and end sizing. Coldstraightening and cold sizing of seamless pipe ends imposing amaximum strain of 1.5% may be performed after surface test-ing of the pipe body but prior to testing of pipe ends.All NDT for "in-house" purposes may be performed at anytime at the Manufacturer's discretion.107 If NDT of plate in accordance with subsection G is per-formed at the plate mill, ultrasonic testing for laminar imper-fections may be omitted at the pipe mill. 108 Reporting of NDT shall be according to the require-ments of the applicable ISO standard unless otherwise agreed.

H 200 Suspect pipe201 In all cases when pipe inspection results in the auto-mated NDT system is giving signals equal to or greater thanthe threshold level or when surface imperfections are disclosedby visual examination, the pipe shall be deemed suspect.Suspect pipe can be dealt with according to one of the follow-ing options:

— the suspect pipe can re-inspected using the automatedNDT equipment in the static mode. Pipes passing thesetests are deemed acceptable

— the suspect area of the pipe can be re-tested by manualNDT using the same NDT method and sensitivity as theautomated NDT, and using appropriate techniques. Pipespassing these tests are deemed acceptable

— the suspect area of welds, except HFW welds, can be radi-ographed to determine if the indication is caused by slagor porosity type indications. Pipes meeting the require-ments of ISO 12096 are deemed acceptable

— defective welds, except HFW welds, can be repaired bywelding according to H301 through 307

— defects can be removed by grinding according to H308 — the suspect area can be cut off if the minimum specified

length is met after cutting— the pipe can be scrapped.

If the suspect area is cut off, then all NDT requirements per-taining to pipe ends shall be performed on the new pipe end.

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H 300 Repair of suspect pipeRepair welding301 Repair welding of pipe body or repair welding of weldsin HFW pipe is not permitted.302 Repair welding of cracks is not permitted unless thecause of cracking has been established not to be a systematicwelding error. (If there is a crack in the weld the pipe is per def-inition considered rejected.) This means a technical evaluationof the cause of cracking shall be performed. If it can be dem-onstrated that the crack is a “one off” situation, repair weldingmay be performed subject to agreement)303 Repair welding shall be performed according to quali-fied repair welding procedures. Each repair shall be performedwith a minimum of two passes over a length not less than 50mm.304 The total length of weld repair in any single pipe shallnot exceed 5% of the weld length.305 Weld defects separated by less than 100 mm shall berepaired as a single continuous repair. 306 Re-inspection of repair welds shall be 100% visualexamination and 100% ultrasonic and/or 100% radiographictesting as required for the original weld. 307 Acceptance criteria for weld repairs shall be as for theoriginal weld.Repair of welds by grinding308 Surface defects may be dressed out by cosmetic grind-ing. Ground areas shall blend smoothly into the surroundingmaterial. Complete removal of defects shall be verified bylocal visual inspection and, if necessary, aided by suitableNDT inspection methods. The remaining wall thickness in theground area shall be checked by ultrasonic wall thicknessmeasurements to verify that the thickness of the remainingmaterial is more than the specified minimum. Imperfectionsthat encroach on the minimum permissible wall thickness and/or weld thickness shall be classified as defects. Repair of pipe body by grinding309 Repair of pipe body by grinding shall be performedaccording to H525 through 527.Disposition of pipe containing defects310 Disposition of pipe containing defects after repair shallbe according to H528.

H 400 General requirements for automated NDT sys-temsAlternative methods of testing401 Subject to agreement, alternative methods of testingmay be accepted if the alternative test method is documentedas required in H402 and the alternative test method is demon-strated to give at least the same sensitivity and capability indetection of imperfections. 402 The demonstration of the alternative test method shall bebased upon the principles given in Subsection F and usingsample lengths of pipe similar to those ordered. The pipes shallcontain a representative and agreed size range of natural and/or artificial defects of types that are typical for the manufactur-ing process in question.System calibration403 All automated NDT systems shall have a full system cal-ibration with intervals not exceeding 12 months. Documenta-tion shall be available. Documentation of system capabilities404 Documentation of automated NDT systems shall beavailable to demonstrate that the systems are capable of detect-ing the reference indicators used to establish the specified test

sensitivity. The documentation shall, as a minimum cover:

— NDT system operating procedures— capability for the intended wall thickness— capability for the intended material— repeatability— detection of defects typical for the manufacturing process

with the equipment in question— threshold level setting parameters— dynamic test data demonstrating the systems capability

under production test conditions.

Reference standards for ultrasonic and electromagneticinspection405 Reference standards shall meet the requirements of theapplicable ISO standard and the requirements given in thisappendix.406 The reference standard shall be a length of pipe with thesame outside diameter and wall thickness tolerances and withsimilar acoustic properties as the pipe tested during produc-tion. For welded pipe the reference standard shall contain aweld typical for the production weld to be tested.407 Reference standards may be of any convenient length asdecided by the manufacturer.408 Reference standards shall contain reference indicationsas required by this Appendix for the pipe to be tested.409 Verification of the dimensions and shape of all referenceindications shall be performed according to a documented pro-cedure. Documentation shall be available. All reference stand-ards shall be marked with an identification that relates to thespecific application of each reference standard.Validation of length of pipe tested 410 When automated non-destructive testing equipment isused, a short area at both pipe ends will normally not be tested.A sample pipe shall be fitted with a suitable reference indicatorat each end. The distance from the pipe end to the referenceindicator shall be equal to the length not covered by the auto-mated testing equipment during production testing. Prior tostart of production the sample pipe shall be passed through thetesting equipment at the operational scanning velocity. Foracceptance of the equipment, both reference indicators shall bedetected. At the manufacturer’s option, these reference indica-tors may be included in the reference standard.Scanning velocity411 The scanning velocity shall be selectable. The scanningvelocity shall be set low enough so that the length between theactivation of each probe (spatial resolution) is sufficientlyshort, i.e. the distance the probe travels while inactive, shall besignificantly less than the maximum length of allowableimperfections. 412 The scanning velocity VC for inspection of longitudinalwelds shall be determined according to:

Where WC is the narrowest - 6 dB effective beam width at theappropriate distance of all probes within the array and PRF isthe effective pulse repetition frequency per probe.413 The circumferential scanning velocity for inspection ofseamless pipe and helical welds shall be decided depending oneffective pulse spacing (pulse density) and on circumferentialscanning speed and helical pitch. The effective pulse spacing(EPS) is specified as follows:

— EPS = circumferential scanning speed/PRF— EPS shall not exceed 1 mm/pulse.— The helical pitch (mm/revolution) shall not exceed the narrow-

est - 6 dB effective beam width of all probes within the array.

VC WC PRF 3⁄•≤

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Lack of coupling414 Automated ultrasonic testing systems shall incorporate asystem for detection of lack of coupling. The settings for lackof coupling alarm and check of the settings shall be describedin the manufacturer’s written procedure. Initial sensitivity and threshold settings (calibration)415 The sensitivity and threshold settings shall be estab-lished according to a documented procedure. The system shallbe optimised in the static mode. When the settings are opti-mised, the relevant parameters shall be recorded and the refer-ence standard shall be passed 3 times through the equipment atthe operational velocity. Any change in settings required tomaintain the static mode settings shall be recorded as an aver-age of the 3 runs. For acceptance of the settings, all referencereflectors need to be detected at or above the threshold. 416 During production testing the relative speed of move-ment between the pipe and the test assembly shall not exceedthat used for the sensitivity and/or alarm settings duringdynamic calibration. Verification of sensitivity and threshold settings (calibration)417 The sensitivity of sensitivity and/or alarm settings shallbe verified every fourth hour or once every 10 pipes tested,whichever is the longer period, and:

— at the start and end of each shift— at any change of equipment operator (for continuous shifts

the end and start verification can be combined) — whenever a malfunction of the equipment is suspected.

The verification frequency when manufacturing HFW pipefrom coil shall be agreed upon. As a minimum the frequencyshall be at the beginning and end of an inspection and at anystops in production.Resetting of sensitivity and threshold settings (recalibration)418 Resetting of sensitivity and threshold settings shall beperformed whenever:

— the standard reflectors do not trigger the alarm during ver-ification of sensitivity and threshold settings

— a change of component affecting the sensitivity and/oralarm setting is made in the system

— the verification of sensitivity and/or alarm settings fails tomeet the requirements for the particular equipment.

For re-setting of sensitivity and threshold settings during pro-duction the settings shall be optimised in the static mode.When the settings have been optimised, the reference standardshall be passed once through the equipment at the operationalvelocity. Any change in settings required to maintain the staticmode settings shall be recorded. For acceptance of the settings,all reference reflectors need to be detected at or above thethreshold. Retesting of pipes419 If the verification of sensitivity and threshold settingsfails to meet the requirements for the particular equipment, allpipes inspected since the previous successful verification shallbe retested.Specific requirements for ultrasonic testing equipment forwelds420 The equipment shall be capable of inspecting the entirethickness of the weld seam.421 Before starting production testing, the range scale andangle of all probes shall be demonstrated to comply with thedocumented procedure. 422 Equipment for testing of welds shall have a weld track-ing system. The system should be capable of tracking the weldcentreline with an accuracy of ± 2 mm or better. For systemsnot meeting this requirement it shall be documented that:

— the sensitivity during production testing will not beaffected by the lower accuracy of the tracking system

— that the lower accuracy is compensated by system sensitiv-ity and gate settings.

423 The gates shall be set wide enough to cover 3 mm of thebase material outside the fusion line and to compensate for:

— the tolerances of weld tracking system— variations in the width of external and internal caps— offsets between the external and internal weld bead.

Ultrasonic testing of CRA pipes and welds with CRA welddeposits424 Ultrasonic testing of welds with CRA (duplex, otherstainless steels and nickel alloy steel) weld deposits will inorder to achieve an adequate detection of imperfections, nor-mally require that special reference blocks and probes are usedfor testing of these materials. 425 Angle probes for duplex stainless steel and austeniticsteels shall be twin crystal (transmitter/receiver) compression-wave probes. Angle compression wave probes shall and canonly be used for scanning without skipping and creep waveprobes must therefore be used for detection of sub-surfacedefects close to the scanning surface. 426 Reference blocks for duplex stainless steel and auste-nitic steels materials and the weld deposits shall have a specificlocation and type of reference reflectors in general compliancewith B400. Surface notches will not be suitable due to themode conversions at base material and a surface notch. Thiswill result in multiple echoes with different arrival timeappearing from the same notch. The actual reflection from thereflector will be weak and distinguishing this echo from othersignals will often not be possible. 427 Specific ultrasonic testing procedures shall be devel-oped for this testing. The procedures shall be developed con-sidering the requirements B400 and addressing the specificfeatures and characteristics of the equipment to be used. 428 It is recognised that not all equipment will be adaptableto meet the requirements above.429 Low frequency shear wave angle probes may be used forduplex stainless steel and austenitic steels instead of the anglecompression wave probes, provided it is verified on referenceblocks made in accordance with B400 that it is possible toobtain a DAC with shear wave angle probe(s) that is compara-ble to a DAC obtained from angle compression-wave probes.The shear wave angle probes used for this verification shall beidentical to the probes used in the production testing equip-ment. 430 If it is not possible to demonstrate adequate performanceof low frequency shear wave angle probes for ultrasonic test-ing of duplex stainless steel and austenitic steels, other meth-ods or combination of methods shall be used and the adequacyof the method(s) demonstrated.431 Notches and through drilled holes are not considered asuitable reflector for compression wave angle probes due to themode conversion and unpredictable arrival times of mode con-verted signals. When compression wave angle probes are used,other types of reflectors shall be used and the acceptance crite-ria specified accordingly.Specific requirements for radiographic testing432 Radiographic testing shall be performed in accordancewith ISO 12096, image class R1 using wire type Image QualityIndicators (IQI) in accordance with ISO 19232. 433 Radioscopic testing techniques in accordance with EN13068 may be used provided the equipment has been demon-strated, in accordance with Subsection F, to give sensitivityand detection equivalent to conventional x-ray according toISO 12096.

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434 If radioscopic testing techniques are used, the quality ofthe ray image has to be verified as required in 417.

H 500 Visual examination and residual magnetismGeneral 501 Visual examination shall be carried out in a sufficientlyilluminated area; minimum 350 lx, but 500 lx is recommended.If required additional light sources shall be used to obtain goodcontrast and relief effect between imperfections and back-ground. 502 In accordance with Sec.7, Table 7-16, each linepipeshall be subject to 100% visual inspection. This implies 100%visual inspection of the outside of the pipe body. The interiorof the pipe shall be inspected from both ends as far as accesspermits. The interior of duplex stainless steel and clad/linedmaterial should be 100% visually inspected.503 A sufficient amount of tools, gauges, measuring equip-ment and other devices shall be available at the place of exam-ination.504 The pipes to be examined shall be cleaned to removeloose scale and processing compounds that may interfere withthe examination. The cleaning process shall not affect the sur-face finish or mask possible imperfections.505 Subject to agreement, alternative methods of testingmay be accepted. It shall be demonstrated that the alternativetest method give at least the same sensitivity and capability indetection of imperfections. The demonstration of the alterna-tive test method shall be based upon the principles given inSubsection F on similar pipes to those ordered. The pipes shallcontain a representative and agreed size range of natural and/or artificial defects of types that are typical for the manufactur-ing process in question. Visual examination of all linepipe506 End preparation such as bevelling shall meet the speci-fied requirements.507 The internal weld bead shall be removed by grinding fora distance of at least 100 mm from each pipe end. The transi-tion between base material and weld metal shall be smooth andthe height of the remaining weld bead shall not extend abovethe adjacent pipe surface by more than 0.5 mm. 508 If specified, the external weld bead shall be removed bygrinding for a distance of at least 250 mm from each pipe end.The transition between base material and weld metal shall besmooth and the height of the remaining weld beads shall notextend above the adjacent pipe surface by more than 0.5 mm.Visual examination of welds in linepipe509 Each linepipe weld shall be subject to 100% visualexamination in accordance with ISO 17637. For C-Mn steellinepipe with internal diameter (ID) ≥ 610, the internal weldshall be 100% visually inspected. The internal weld of C-Mnlinepipe with ID < 610 mm shall be inspected from both endsas far as access permits. 510 The internal weld and adjacent surfaces in duplex stain-less steel, CRA and clad linepipe shall be inspected full length.If necessary, the inspection of the internal weld shall beassisted by a boroscope, video endoscope or similar equip-ment.511 Welds shall meet the requirements of Table D-4. 512 Line pipe containing welds not meeting the require-ments above shall be classified as suspect pipe according toH200, and treated according to H300.Surface conditions, imperfections and defects513 The surface finish produced by the manufacturing proc-ess shall be such that surface defects can be detected by visualinspection.

514 All pipes shall be free from defects in the finished con-dition. The manufacturer shall take adequate precautions toprevent pipe damage and minimise the presence of imperfec-tions.515 Cracks, sweats or leaks are not acceptable and shall beclassified as defects.516 Surface imperfections evident by visual inspection shallbe investigated, classified and treated as according to H517 toH522. H519 applies to surface imperfections at the internalsurface of clad or lined pipes.517 Imperfections with depth ≤ 5% of the specified wallthickness, or 0.5 mm, whichever is greater, but maximum 0.7mm for t ≤ 25 mm, and maximum 1.0 mm for t > 25 mm, andwhich do not encroach upon the specified minimum wall thick-ness, shall be classified as acceptable imperfections. Theimperfections may remain in the pipe or be dressed out by cos-metic grinding.518 Imperfections with depth larger than stated in H517, andwhich do not encroach upon the specified minimum wall thick-ness, shall be classified as dressable defects and shall either beremoved by grinding in accordance with H525 or treated inaccordance with H528, as appropriate.519 For the internal surface of clad or lined pipes the follow-ing applies: Imperfections with depth ≤ 0.5 mm, and which donot encroach upon the specified minimum wall thickness, shallbe classified as acceptable imperfections. The imperfectionsmay remain in the pipe or be dressed out by cosmetic grinding.Imperfections with larger depth, and which do not encroachupon the specified minimum wall thickness, shall be classifiedas dressable defects and shall either be removed by grinding inaccordance with H525 or treated in accordance with H528, asappropriate.520 Imperfections which encroach upon the specified mini-mum wall thickness shall be classified as defects.521 Two or more adjacent imperfections shall be consideredas one imperfection if they are separated by less than thesmaller dimension of either indication.522 Imperfections with depth according to H517 or H519 ofwhich the depth can not be assessed by suitable gauges or alter-native means, shall either be removed by grinding in accord-ance with H525 or treated in accordance with H528, asappropriate.Dents523 For dents without any cold formed notches and sharpbottom gouges, the length in any direction shall be ≤ 0.5 D andthe depth, measured as the gap between the extreme point ofthe dent and the prolongation of the normal contour of the pipe,shall not exceed 6.4 mm.

— For dents with cold-formed notches and sharp bottomgouges with depth according to H517 the depth of dentsshall not exceed 3.2 mm.

— Dents > 1 mm are not acceptable at the pipe ends, i.e.within a length of 100 mm at each of the pipe extremities.

— Dents exceeding these dimensions shall be classified asdefects.

Hard spots524 Hard spots, as identified e.g. due to irregularities in thepipe curvature of cold-formed welded linepipe, shall be inves-tigated to determine the hardness and dimensions of the area. For linepipe intended for non sour service the hardness shallnot exceed:

— 300 HV10 for C-Mn steels— the values given in Sec.7 Table 7-11, for the material in

question.

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For linepipe intended for sour service (Supplementary require-ment S) the hardness shall not exceed:

— 250 HV10 C-Mn steel— for other steels, maximum allowable hardness according

to ISO 15156-3.

Hard spots outside the hardness requirements for the applica-ble material larger than 50 mm in any direction and within 100mm of the pipe ends regardless of size shall be classified asdefects. Grinding525 Imperfections or defects according to H518 or H519may be dressed-out by grinding. Ground areas shall blendsmoothly into the surrounding material. Complete removal ofdefects shall be verified by local visual inspection and, if nec-essary, aided by suitable NDT inspection methods. Theremaining wall thickness in the ground area shall be checkedby ultrasonic wall thickness measurements to verify that thethickness of the remaining material is more than the specifiedminimum.526 The sum of the ground area shall not exceed 10% of thesum of the external and internal surface area of each pipe.Ground areas which have been smoothly blended into the sur-rounding material and classified as cosmetic grinding shall notbe counted in the calculation.527 Full length machining of pipes is acceptable if machin-ing is performed according to a qualified procedure thatensures freedom from circumferential grooves or other defectswith depth > 0.5 mm. H526 does not apply to pipe that aremachined full length.Disposition of pipe containing defects528 Linepipe containing defects shall be rejected or the areacontaining defects can be cut off. If pipes are cut, the minimumspecified length shall be met after cutting and all NDT pertain-ing to pipe ends shall be performed on the new pipe end.Residual magnetism529 The longitudinal magnetic field shall be measured onpipe with OD ≥ 168.3 mm and all smaller pipes that areinspected full length by magnetic methods or are handled bymagnetic equipment prior to loading.

— The measurements shall be taken on the root face or squarecut face of finished pipe. Measurements made on pipe instacks are not considered valid.

— Measurements shall be made on each end of a pipe, for 5%of the pipes produced but at least once per 4 hr per operat-ing shift using a Hall-effect gauss-meter or other type ofcalibrated instrument. In case of dispute, measurementsmade with a Hall-effect gauss-meter shall govern. Meas-urements shall be made in accordance with a written pro-cedure demonstrated to produce accurate results.

— Pipe magnetism shall be measured subsequent to anyinspection that uses a magnetic field, prior to loading forshipment from the pipe mill.

— Four readings shall be taken 90° apart around the circum-ference of each end of the pipe.

530 The average of the four readings shall be less or equal to2.0 mT (20 Gauss), and no single reading shall exceed 2.5 mT(25 Gauss). Any pipe that does not meet this requirement shallbe considered defective. 531 All pipes produced between the defective pipe and thelast acceptable pipe shall be individually measured unless theprovisions of H530 can be applied.532 If the pipe production sequence is documented, pipemay be measured in reverse sequence, beginning with the pipeproduced immediately prior to the defective pipe, until at leastthree consecutively produced pipes meet the requirements.

— Pipe produced prior to these three acceptable pipes neednot be measured

— Pipe produced after the defective pipe shall be measuredindividually until at least three consecutive pipes meet therequirements.

533 All defective pipe shall be de-magnetized full length,and then their magnetism shall be re-measured until at leastthree consecutive pipes meet the requirements of H530.534 For pipe handled with electromagnetic equipment aftermeasurement of magnetism, such handling shall be performedin a manner demonstrated not to cause residual magnetismexceeding the acceptance criteria in H530.535 The requirements for residual magnetism shall applyonly to testing within the pipe mill since the residual magnet-ism in pipe may be affected by procedures and conditionsimposed on the pipe during and after shipment.

H 600 Non-destructive testing of pipe ends not tested by automated NDT equipmentUntested pipe ends601 When automated non-destructive testing equipment isused, a short area at both pipe ends will normally not be tested(see H410). Either the untested shall be cut off or the ends sub-jected to manual or automated NDT to the same extent asrequired for the full length of pipe602 The methods, sensitivity and acceptance criteria for test-ing of untested ends shall be the same as used for retesting ofpipes having signals equal to or greater than the threshold levelfrom the automated non-destructive testing equipment.603 The manufacturer shall prior to start of productionpresent for acceptance the proposed extent, methods, sensitiv-ity and acceptance criteria for testing of untested ends with ref-erence to applicable procedures.

H 700 Non-destructive testing of pipe endsGeneral701 These requirements apply to both seamless and weldedpipe. Pipes not meeting the acceptance criteria below shall bedeemed as “suspect pipe” according to H200 and shall betreated according to H300.Testing of pipe ends for laminar imperfections702 Both ends of each pipe shall be tested for laminar imper-fections in accordance with ISO 11496 and the additionalrequirements in H400 over a band at least 50 mm inside thelocation of future welding preparations for girth welds.703 If additional non-destructive testing is specified by thepurchaser, the width of the band should be:

— at least 150 mm inside the location of future welding prep-arations for girth welds if automated ultrasonic testing ofgirth welds during installation will be performed

— at least 100 mm inside the location of future welding prep-arations for girth welds if allowance for re-bevelling ofpipe shall be included.


— according to Table D-12 or, if agreed, G203— G300 for clad pipe.

Testing of end face or bevel for laminar imperfections705 Magnetic particle testing or eddy current testing, manualor automated, of both end faces or bevels of each pipe in ferro-magnetic steel for the detection of laminar imperfections shallbe performed in accordance with the requirements in H400and:

— ISO 13664 for magnetic particle testing

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— ISO 9304 for eddy current testing.

706 Liquid penetrant or eddy current testing, manual or auto-mated, of the end face or bevel of each pipe in non-ferromag-netic steel for the detection of laminar imperfections shall beperformed in accordance with the requirements in H400 and:

— ISO 12095 for liquid penetrant testing— ISO 9304 for eddy current testing.


— Imperfections longer than 6 mm in the circumferentialdirection are not permitted.

H 800 Non-destructive testing of seamless pipePipe ends 801 Pipe ends shall be tested as required by H600 and 700.Ultrasonic inspection for laminar imperfections in the pipebody 802 Ultrasonic inspection of the pipe body shall be per-formed in accordance with the requirements in H400 and ISO10124 amended as follows:

— the distance between adjacent scanning tracks shall be suf-ficiently small to ensure detection of the minimumallowed imperfection size.

803 The acceptance criteria are:

— according to Table D-12 or, if agreed, G203.

Ultrasonic inspection for longitudinal imperfections in thepipe body804 Ultrasonic inspection of the pipe body shall be per-formed in accordance with the requirements in H400 and ISO9303. The probe angles shall be chosen to obtain the best testresult for the wall thickness/diameter ratio of the pipe to betested.For pipes in CRA materials it shall be verified that the presenceof any possible coarse, anisotropic zones will not impede thetesting, see H424 through H431.805 The acceptance criterion is:

— Acceptance level L2/C according to ISO 9303.

Ultrasonic inspection for transverse imperfections in the pipebody806 Ultrasonic inspection of the pipe body shall be per-formed in accordance with the requirements in H400 and ISO9305. The probe angles shall be chosen to obtain the best testresult for the wall thickness/diameter ratio of the pipe to betested.For pipes in CRA materials it shall be verified that the presenceof any possible coarse, anisotropic zones will not impede thetesting, see H424 through H431.807 The acceptance criterion is:

— Acceptance level L2/C according to ISO 9305.

Ultrasonic thickness testing of the pipe body808 Ultrasonic thickness testing of the pipe body shall beperformed in accordance with the requirements in H400 andISO 10543.809 The acceptance criterion is:

— The specified maximum and minimum wall thicknessshall be met.

Surface testing for longitudinal and transverse imperfectionsin the pipe body of ferromagnetic pipe810 Testing of ferromagnetic seamless pipe for the detectionof longitudinal and transverse surface imperfections shall beperformed in accordance with the requirements in H400 andone of the following standards:

— ISO 9304 (eddy current testing)— ISO 9402 (flux leakage testing for longitudinal indica-

tions)— ISO 9598 (flux leakage testing for transverse indications)— ISO 13665 (magnetic particle testing).

811 For detection of internal indications ISO 9304, ISO 9402or ISO 9598 shall be preferred provided adequate signal ampli-tudes from the internal surface reflector are documented andused for sensitivity setting.812 The acceptance criteria are:

— ISO 9304: Alarm level/acceptance level L2— ISO 9402: Alarm level/acceptance level L2— ISO 9598: Alarm level/acceptance level L2— ISO 13665: Alarm level/acceptance level Table 2, M2.

Surface testing for longitudinal and transverse indications inpipe body of non-magnetic pipe813 Testing of non-magnetic seamless pipe for the detectionof longitudinal and transverse surface imperfections shall beperformed in accordance with the requirements in H400 andone of the following standards:

— ISO 9304 (eddy current testing)— ISO 12095 (liquid penetrant testing).

814 For detection of internal indications ISO 9304 shall bepreferred provided adequate signal amplitudes from the inter-nal surface reflector are documented and used for sensitivitysetting.815 The acceptance criteria are:

— ISO 9304: Alarm level/acceptance level L2— ISO 12095: Alarm level/acceptance level P2.

Suspect pipe816 Pipes not meeting the acceptance criteria above shall bedeemed as “suspect pipe” according to H200 and shall betreated according to H300.

H 900 Non-destructive testing of HFW pipePipe ends901 Pipe ends shall be tested as required by H600 and H700Ultrasonic testing of the pipe body for detection of laminarimperfections902 Ultrasonic testing of the pipe body for detection of lam-inar imperfections need not be performed at the pipe mill iftesting of the coil edges was performed at the coil mill accord-ing to subsection G. 903 If performed at the pipe mill, ultrasonic testing of thepipe body for detection of laminar imperfections shall be per-formed in accordance with the requirements in H400 and ISO10124 amended as follows:




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Ultrasonic testing of the area adjacent to the weld seam fordetection of laminar imperfections905 Ultrasonic testing of the area adjacent to the weld seambody for detection of laminar imperfections shall be performedat the pipe mill if the strip is made by splitting of coil. If thestrip is not made by splitting of coil and is tested for laminarimperfections at the coil mill according to subsection G, notesting for detection of laminar imperfections need to be per-formed at the pipe mill906 If performed at the pipe mill, the testing shall be per-formed according to the requirements in H400 and ISO 13663.907 Acceptance criteria are:

— according to Table D-12 or, if agreed G203.

Ultrasonic testing for longitudinal imperfections in the weldseam908 Ultrasonic testing of the full length of the weld seam ofHFW pipe for the detection of longitudinal imperfections shallbe performed in accordance with the requirements in H400 andISO 9764 with modifications as described in 909 through 918.909 Accurate weld tracking with a tolerance ± 2 mm withrespect to the centreline of the weld is essential due to thewidth of the weld.910 The reference standard shall contain a typical weld, withthe external flash removed and including tracks resulting fromremoval of the internal flash.The reference reflectors shall be:

— external and internal reference notches located parallel toand in the centre of the weld. The notches shall be “N”type with a depth of 5% of the wall thickness notches witha depth of minimum 0.3 mm and maximum 1.2 mm.

911 One or more of the following probe configurations shallbe used:

— Single pulse echo probes shall be selected such as theangle of incidence is as perpendicular to the radial cen-treline of the weld as possible.

— Tandem probes on each side of the weld with the angle ofincidence as perpendicular to the radial centreline of theweld as possible.

— Probes alternating as transmitter-receiver with the angle ofincidence as perpendicular to the radial centreline of theweld as possible.

The probe configuration shall provide a sufficient number ofprobes to cover the entire wall thickness from both sides of theweld. 912 The equipment shall include devices for weld tracking/centering and provide checking of adequate coupling for allprobes.913 Each probe shall be calibrated against the referencereflector located in the area of the weld to be covered by thatprobe.914 For single pulse echo probes and tandem probes thethreshold settings shall be as follows:

— If the testing is performed with one probe pair covering theentire wall thickness, the response from the intersectionsbetween the reference notches and the external and inter-nal pipe surface shall optimised and the threshold level setat 80% of full screen height of the lowest of the obtainedresponses.

— If the testing is performed with probe pairs each coveringa part of the wall thickness, the threshold level shall be setat 80% of full screen height.

915 For probes alternating as transmitter-receiver the thresh-

old level shall be set corresponding to a loss of 75% of thetransmitted signal.916 For each probe, the following shall be recorded:

— type, frequency, angle and dimension— the distance from the index point to the weld centreline— the angle between the ultrasound direction and the major

pipe axis.— amplitudes and gain settings.

917 Gates shall be set such that reflections from the tracksresulting from removal of the internal flash are avoided butsufficiently wide to ensure that the tolerances in the weld track-ing system will result in responses from indications inside theweld and the HAZ.918 The settings for lack of coupling alarm shall be set andchecked.919 The acceptance criterion is:

— Pipes producing signals below the threshold shall bedeemed to have passed the test.

Plate/strip end welds920 Testing of plate/strip end welds (when such welds areallowed) shall, unless otherwise agreed be performed by ultra-sonic testing according to this standard. The testing shall com-ply with the requirements of this standard and methods and aset-up suitable for the applied welding method shall be used.Suspect pipe921 Pipes not meeting the acceptance criteria above shall bedeemed as “suspect pipe” according to H200 and shall betreated according to H300.

H 1000 Non-destructive testing of CRA liner pipe1001 Testing of CRA pipe for the detection of longitudinaland transverse surface imperfections and the longitudinal weldshall be performed in accordance with the requirements inH400 and ISO 9304 (eddy current testing).

— The acceptance criterion for eddy current testing is:— The response shall not exceed half the response of alarm

level/acceptance level L2 according to ISO 9304.

1002 Testing of the weld seam can alternatively be per-formed in accordance with the requirements in H400 and ISO12096 (radiographic testing).1003 The acceptance criteria for radiographic testing are:

— No cracks, lack of fusion, lack of penetration or pore clus-ters. Individual circular imperfections shall not exceed1.5 mm or ¼ t, whichever is smaller. Accumulated diame-ters of permitted imperfections shall not exceed 3 mm or½ t, whichever is smaller. No other discernable indicationsare allowed.

Untested pipe ends1004 Untested pipe ends shall be tested as required by H600.Suspect pipe1005 Pipes not meeting the acceptance criteria above shallbe deemed as “suspect pipe” according to H200 and shall betreated according to H300.

H 1100 Non-destructive testing of lined pipeNon-destructive testing of the backing pipe1101 Non-destructive testing of the outer C-Mn steel back-ing pipe shall be performed prior to insertion of the CRA linerpipe. The backing pipe shall be subjected to the same testingwith the same acceptance criteria that are required in thisAppendix for the type of backing pipe used.

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Pipe ends1102 After insertion of the liner pipe and performing sealand/or clad welding the ends of lined pipe shall be tested forlaminar imperfections in accordance with the requirements inH400 and ISO 11496 or ASTM A578 S7 in a band at each pipeend. For clad welded pipe ends this includes testing for bond-ing defects. The band shall be sufficiently wide to cover thewidth of the seal/clad weld between the C-Mn steel backingpipe and the CRA liner pipe. Manual or automated methodsmay be used.1103 The acceptance criterion is:

— No indications are allowed within the tested areas.

Seal and clad welds1104 The seal and/or clad welds at pipe ends shall be subjectto manual liquid penetrant testing according to B600 or eddycurrent testing according to B700.1105 The acceptance criteria are:

— No round indications with diameter above 2 mm and noelongated indications.

— Indications separated by a distance less than the diameteror length of the smallest indication, shall be considered asone indication.

— Accumulated diameters of round indications in any 100mm length of weld shall not exceed 6 mm.

H 1200 Non-destructive testing of clad pipePipe ends1201 Pipe ends shall be tested as required by H600 andH700.Ultrasonic testing of the pipe body for detection of laminarimperfections1202 Ultrasonic testing of the pipe body for detection of lam-inar imperfections in the backing pipe need not be performedat the pipe mill if testing of the plate was performed at the platemill according to subsection G. 1203 If performed at the pipe mill, ultrasonic testing of thepipe body for detection of laminar imperfections shall be per-formed in accordance with the requirements in H400 and ISO10124 amended as follows:

— The distance between adjacent scanning tracks shall besufficiently small to ensure detection of the minimumallowed imperfection size.



1205 Ultrasonic testing of the pipe body for detection of lackof bond between the cladding and backing pipe shall be per-formed in accordance with the requirements in H400 andASTM 578 S7 amended as follows:

— The distance between adjacent scanning tracks shall besufficiently small to ensure detection of the minimumallowed imperfection size.


— ASTM A578 - S7. In addition, no areas with laminationsor lack of bond are allowed in the plate edge areas.

Ultrasonic testing for longitudinal and transverse imperfec-tions in the weld seam1207 For ultrasonic testing of the CRA part of the weld seamit must be demonstrated that low frequency shear wave angleprobes are adequate for detection as required in H424 throughH431. If it is not possible to demonstrate adequate perform-

ance of low frequency shear wave angle probes other methodsor combination of methods shall used and the adequacy of themethodology demonstrated.Ultrasonic testing of the weld seam of clad pipe for the detec-tion of longitudinal and transverse imperfections, when dem-onstrated to give acceptable results, shall be in accordancewith the requirements in H400 and ISO 9765 with modifica-tions as described in 1208 through 1219.1208 The reference standard shall contain a typical produc-tion weld. The weld surface shall be ground flush with the orig-inal pipe contour in an area around each reference reflectorsufficient to obtain signals without interference from un-ground weld reinforcements.1209 The reference reflectors shall be:

— One 1.6 mm diameter through-drilled hole at the weld cen-treline for detection of transverse indications.

— Longitudinal external and internal notches on both sides,parallel and adjacent to the weld seam for detection of lon-gitudinal imperfections outside the root area. The notchshall be the “N” type with 5% of the wall thickness, but notmore than 1.5 mm or less than 0.3 mm.

— One notch on each side of the internal weld cap locatedimmediately adjacent to and parallel with the weld fordetection of longitudinal imperfections in the root area.The notch shall be the “N” type with 3% of the wall thick-ness, but not more than 1.2 mm or less than 0.3 mm.

— If agreed, the reference reflectors for detection of trans-verse imperfections can be internal and external notches,“N” type with 3% of the wall thickness, positioned at rightangles to, and centred over, the weld seam.

— Additional reflectors may be used to define the weldextremities and aiding in the gate settings. The use, typeand numbers of such reflectors shall be at the manufac-turer’s option.

The length of the notches shall be 1.5 times the probe (crystal)element size or 20 mm, whichever is shorter. The length doesnot include any rounded corners. The width of the notchesshall not exceed 1 mm.1210 The probe angles shall be chosen to obtain the best pos-sible test result for wall thickness and diameter of the pipe tobe tested. The probe angle shall be chosen such that the angleof incidence is as perpendicular as possible to the weld bevelin the area covered by the probe. 1211 The frequency of the probes used in the root area shallbe as low as possible and not above 2 MHz.1212 The probe configuration for detection of the longitudi-nal indications shall provide a sufficient number of opposingprobe pairs to cover the entire wall thickness. E.g. one pair ofprobes for the external and internal N5 notches and one pair forthe internal N3 notches in the root area.1213 The probe configuration for detection of transverseindications shall be two wide beam, opposing probes travelling“on bead”. An X type configuration of the probes for detectionof transverse indications may be used, subject to agreement.1214 The gates shall be set wide enough to compensate for:

— The tolerances of weld tracking system— Variations in the width of external and internal caps— Offsets between the external and internal weld bead.

1215 Each probe shall be calibrated against the referencereflector located in the area of the weld to be covered by thatprobe. The response from the reference reflectors shall be opti-mised for each probe and probe pair:

— For detection of longitudinal imperfections in the root areathe optimised response for each probe shall be obtainedfrom the internal notch on the opposite side of the weld.

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The threshold level for each of the internal notches shall beset no higher than 50% of full screen height from the max-imised response.

— For detection of longitudinal imperfections outside theroot area the response from the external and internalnotches shall optimised and the threshold level set to 80%of full screen height for each of the maximised responses.

— For detection of transverse imperfections the thresholdlevel for the 1.6 mm through drilled hole or transversenotches shall be set no higher than 80% of full screenheight.

— If the use of transverse notches is agreed for detection oftransverse indications, the response from the external andinternal notches shall optimised and the threshold level setto 80% of full screen height for each of the maximisedresponses.

— The additional reflectors allowed in 1209 shall not be usedfor threshold settings.

1216 For each probe, the following shall be recorded:


pipe axis— amplitudes and gain settings.

1217 Gates shall be set such that reflections from the weldcaps are avoided but sufficiently wide to ensure that, with thegiven tolerances of the weld tracking system, responses areobtained from indications located inside the weld and theHAZ. 1218 The settings for lack of coupling alarm shall be set andchecked.1219 The acceptance criterion when using shear waveprobes is:

— Pipes producing signals below the threshold shall bedeemed to have passed the test.

When compression wave angle probes are used, other types ofreflectors shall be used and the acceptance criteria shall bespecified and agreed accordingly.Ultrasonic testing of the area adjacent to the weld seam fordetection of laminar imperfections1220 Ultrasonic testing of the area adjacent to the weld seambody for detection of laminar imperfections need not be per-formed at the pipe mill if testing of the plate edges was per-formed at the plate mill according to subsection G. 1221 If performed at the pipe mill, the testing shall be per-formed according to the requirements in H400 and ISO 13663.1222 Acceptance criteria are:


Testing for the detection of surface imperfections in the weldarea1223 Testing for the detection of longitudinal and transversesurface imperfections in the weld area shall be performed inaccordance with the requirements in H400 and one of the fol-lowing standards:



1224 The acceptance criteria are:

— ISO 9304: Alarm level/acceptance level L2— ISO 9402: Alarm level/acceptance level L2

— ISO 9598: Alarm level/acceptance level L2— ISO 13665: Alarm level/acceptance level Table 3, M2.

Radiographic testing of welds1225 Full length radiographic testing of the weld shall beperformed in accordance with the requirements in H400 andISO 12096.1226 For pipe subject to full length ultrasonic testing of theweld, radiographic testing of the weld at each pipe end shallinclude the area not covered by the automated ultrasonic test-ing and shall at least cover a weld length of 300 mm. The test-ing shall be performed in accordance with the requirements inH400 and ISO 12096.1227 The acceptance criteria are:

— according to ISO 12096.

Suspect pipe1228 Pipes not meeting the acceptance criteria above shallbe deemed as “suspect pipe” according to H200 and shall betreated according to H300.

H 1300 Non-destructive testing of SAWL and SAWH pipePipe ends1301 Pipe ends shall be tested as required by H600 andH700.Ultrasonic testing of the pipe body for detection of laminarimperfections1302 Ultrasonic testing of the pipe body for detection of lam-inar imperfections need not be performed at the pipe mill iftesting of the plate/coil edges was performed at the plate/coilmill according to subsection G. 1303 If performed at the pipe mill, ultrasonic testing of thepipe body for detection of laminar imperfections shall be per-formed in accordance with the requirements in H400 and ISO10124 amended as follows:




Ultrasonic testing of the area adjacent to the weld seam fordetection of laminar imperfections1305 Ultrasonic testing of the area adjacent to the weld seambody for detection of laminar imperfections need not be per-formed at the pipe mill if testing of the plate/coil edges wasperformed at the plate/coil mill according to subsection G. 1306 If performed at the pipe mill, the testing shall be per-formed according to the requirements in H400 and ISO 13663.1307 Acceptance criteria are:


Ultrasonic testing for longitudinal and transverse imperfec-tions in the weld seam1308 Ultrasonic testing of the weld seam of SAW pipe forthe detection of longitudinal and transverse imperfections shallbe in accordance with the requirements in H400 and ISO 9765with modifications as given in 1309 through 1320.1309 The reference standard shall contain a typical produc-tion weld. The weld surface shall be ground flush with the orig-inal pipe contour in an area around each reference reflectorsufficient to obtain signals without interference from un-ground weld reinforcements.

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1310 The reference reflectors shall be:

— One 1.6 mm diameter through drilled hole at the weld cen-treline for detection of transverse indications

— Longitudinal external and internal notches on both sides,parallel and adjacent to the weld seam for detection of lon-gitudinal imperfections. The notch shall be the “N” typewith 5% of the wall thickness, but not more than 1.5 mmor less than 0.3 mm. The length of the notches shall be 1.5times the probe (crystal) element size or 20 mm, which-ever is shorter. The length does not include any roundedcorners. The width of the notches shall not exceed 1 mm.

— For wall thickness ≥ 19 mm a longitudinal referencereflector, e.g. a side-drilled hole, shall be located at midthickness of the weld and parallel to the weld. This reflec-tor shall provide a return signal comparable to that from aN5 notch. The Manufacturer shall propose a type of reflec-tor suitable for the purpose, and the type of reflector usedis subject to agreement.

— If agreed, the reference reflectors for detection of trans-verse imperfections can be internal and external notches,positioned at right angles to, and centred over, the weldseam.

— Both internal and external weld reinforcements shall beground flush to match the pipe contour in the immediatearea and on both sides of the reference notches.

— Additional reflectors may be used to define the weldextremities and aiding in the gate settings. The use, typeand numbers of such reflectors shall be at the manufac-turer’s option and shall be described in the documentedprocedure.

1311 The probe angles shall be chosen to obtain the best pos-sible test result for wall thickness and diameter of the pipe tobe tested. The probe angle should be chosen such that the angleof incidence is as perpendicular as possible to the weld bevelin the area covered by the probe. 1312 The probe configuration for detection of the longitudi-nal indications shall provide a sufficient number of opposingprobe pairs to cover the entire wall thickness. Each referencereflector shall have a dedicated probe pair.1313 The probe configuration for detection of transverseindications shall be two wide beam, opposing probes travelling“on bead”. An X type configuration of the probes for detectionof transverse indications may be used, subject to agreement.1314 Each probe shall be calibrated against the referencereflector located in the area of the weld to be covered by thatprobe. The response from the reference reflectors shall be opti-mised for each probe and probe pair:

— For detection of longitudinal imperfections the responsefrom the longitudinal external and internal notches shalloptimised and the threshold level set to 80% of full screenheight for each of the obtained responses.

— If a separate reflector is positioned at mid thickness, theresponse from this reflector shall optimised and the thresh-old level set to 80% of full screen height for each of theobtained responses.

— For detection of transverse imperfections the thresholdlevel for the 1.6 mm through drilled hole or transversenotches shall be set no higher than 80% of full screenheight.

— If the use of transverse notches is agreed for detection oftransverse imperfections, the response from the transverseexternal and internal notches shall be optimised and thethreshold level set to 80% of full screen height for each ofthe obtained responses.

— The additional reflectors allowed in 1310 shall not be usedfor threshold settings.

For each probe, the following shall be recorded:


pipe axis— amplitudes and gain settings.

1315 The gates shall be set wide enough to compensate for:

— the tolerances of weld tracking system— variations in the width of external and internal caps— offsets between the external and internal weld bead.

1316 The settings for lack of coupling alarm shall be set andchecked.1317 When the settings are optimised, the relevant parame-ters shall be recorded and the reference standard shall bepassed 3 times through the equipment at the operational veloc-ity. Any change in settings required to maintain the static modesettings shall be recorded as an average of the 3 runs. Foracceptance of the settings, all reference reflectors need to bedetected at or above the threshold and there shall be no signif-icant relative changes in amplitudes between any opposinglongitudinal probes. Gate settings shall not deviate more than2.5 mm from the reference position.1318 The acceptance criterion is:Pipes producing signals below the threshold shall be deemedto have passed the test.Additional requirements for SAWH pipe strip/plate end welds1319 For SAWH pipe the full length of strip/plate end welds(when such welds are allowed) shall be ultrasonically tested asrequired above for the helical seam. Alternatively manualultrasonic testing in accordance with Subsection H1400 maybe used for testing of test strip/plate end welds. In addition, the joints where the extremities of the helical andstrip/plate end welds meet shall be subject to radiographic test-ing in accordance with the requirements in H400 and ISO12096.1320 Acceptance criteria for these tests are:

— For automated ultrasonic testing: according to H1319above

— For manual ultrasonic testing: according to H1400— For radiographic testing: According to ISO 12096.

Additional requirements for testing of SAW CRA pipes andwelds with CRA weld deposits1321 Ultrasonic testing of welds in CRA materials withCRA (duplex, other stainless steels and nickel alloy steel) welddeposits will, in order to achieve an adequate detection ofimperfections, normally require that special reference blocksand probes are used. 1322 The requirements given in H424 through H431 shall befulfilled and special reference is made to H430 and H431.1323 When compression wave angle probes are used, othertypes of reflectors shall be used and the acceptance criteriaspecified accordingly.Testing of ferromagnetic pipe for the detection of surfaceimperfections in the weld area1324 Testing of ferromagnetic pipe for the detection of lon-gitudinal and transverse surface imperfections shall be per-formed in accordance with the requirements in H400 and oneof the following standards:



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The acceptance criteria are:

— ISO 9304: Acceptance level L2— ISO 9402: Acceptance level L2— ISO 9598: Acceptance level L2— ISO 13665: Acceptance level Table 3, M2.

Testing of non magnetic pipe for the detection of surfaceimperfections in the weld area1325 Testing of non-magnetic SAW pipe for the detection oflongitudinal and transverse surface imperfections shall be per-formed in accordance with the requirements in H400 and oneof the following standards:

— ISO 9304 (eddy current testing)— ISO 12095 (liquid penetrant testing).

The acceptance criteria are:

— ISO 9304: Acceptance level L2— ISO 12095: Acceptance level P2.

Radiographic testing1326 Radiographic testing of the weld at each pipe end shallinclude the area not covered by the automated ultrasonic test-ing and shall at least cover a weld length of 300 mm. The test-ing shall be performed in accordance with the requirements inH400 and ISO 12096 The acceptance criteria are:


Suspect pipe1327 Pipes not meeting the acceptance criteria above shallbe deemed as “suspect pipe” according to H200 and shall betreated according to H300.

H 1400 Manual NDT at pipe millsGeneral1401 In all cases when the automated NDT system give sig-nals equal to or greater than the threshold level, or surfaceimperfections are disclosed by visual examination, manualNDT may be performed in order to confirm the presence orabsence of a defect. Automated or semi-automated NDT maybe used as substitution of the manual NDT required in H1400provided the method is demonstrated to provide the same orbetter sensitivity in detection of imperfections. 1402 In addition, manual NDT may be performed on pipeends that are not tested by the automated equipment. See H600.1403 The requirements in H1400 are only applicable to man-ual NDT performed at pipe mills only.Radiographic testing1404 Radiographic testing shall be performed in accordancewith the requirements in H400 and ISO 12096 to cover the fullweld length or to supplement other NDT methods when thetype of or severity of an indication in weld can not be deter-mined with certainty.The acceptance criteria are:


All pipe; manual ultrasonic testing for laminar imperfectionsand thickness testing1405 Manual ultrasonic thickness testing and testing for lam-inar imperfections shall be performed on untested pipe endsand to confirm the presence or absence of a defect when auto-mated NDT systems gives signals equal to or greater than thethreshold level.Manual ultrasonic testing of pipe ends, laminar imperfections

1406 Any additional non-destructive testing shall be as spec-ified by the purchaser.1407 If automated ultrasonic testing of girth welds duringinstallation will be performed the width of the band shouldextend at least 150 mm inside the location of future weldingpreparations for girth welds.1408 If allowance for re-bevelling of pipe shall be included,the width of the band should extend at least 100 mm inside thelocation of future welding preparations for girth welds.1409 Acceptance criteria are:

— according to table d-12 or, if agreed, g203.

Manual ultrasonic testing of pipe ends, radial cracks1410 For detection of cracks angle probes shall be used tosupplement the straight beam probes. Testing shall be in gen-eral accordance with ASTM A577 or equivalent standard and:

— Probes shall meet the requirements of C203.— Sensitivity for C-Mn steel shall be a DAC curve based on

reference blocks with a rectangular notch with depth 3%of the material thickness on both sides.

— Reference blocks for duplex stainless steel and austeniticsteels shall have one Ø 3 mm flat bottom hole perpendic-ular to the angle of incidence of the probe and at the largestpossible depth from the scanning surface of the block. Ref-erence blocks shall be of the actual material tested or of amaterial with similar with acoustic properties.

— Low frequency shear wave angle probes may be used forCRA material instead of twin crystal (transmitter/receiver)compression-wave probes. For acceptance, it shall be ver-ified on the reference blocks that it is possible to obtain aDAC with a shear wave angle probe that is comparable tothe DAC obtained with an angle compression wave probe.


— no indications shall exceed the DAC.

Manual ultrasonic testing of the pipe body for detection oflaminar imperfections1412 Manual ultrasonic testing of the pipe body for detectionof laminar imperfections need not be performed at the pipe millif testing of the plate/coil edges was performed at the plate/coilmill according to subsection G. 1413 If performed at the pipe mill, manual ultrasonic testingof the pipe body for detection of laminar imperfections shall beperformed in accordance ISO 10124 amended as follows:




Manual ultrasonic testing of the area adjacent to the weldseam for detection of laminar imperfections1415 Manual ultrasonic testing of the area adjacent to theweld seam body for detection of laminar imperfections neednot be performed at the pipe mill if testing of the plate/coiledges was performed at the plate/coil mill according to Sub-section G. 1416 If performed at the pipe mill, the manual NDT shall beperformed according to ISO 13663.1417 Acceptance criteria are:


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Manual ultrasonic thickness testing of the pipe body1418 Manual ultrasonic thickness testing of the pipe body shallbe performed in accordance with the requirements ISO 10543.1419 The acceptance criterion is:

— the specified maximum and minimum wall thickness shallbe met.

Seamless pipe; manual ultrasonic testing for longitudinal andtransverse imperfections1420 Manual ultrasonic testing and testing of seamless pipefor longitudinal and transverse imperfections shall performedon untested pipe ends and to confirm the presence or absenceof a defect when automated NDT systems gives signals equalto or greater than the threshold level.1421 For pipes in CRA materials it shall be verified that thepresence of any possible coarse, anisotropic zones will notimpede the testing, see H424 through H431.1422 Manual ultrasonic testing of the pipe body for longitu-dinal imperfections shall be performed in accordance with ISO9303. The probe angles shall be chosen to obtain the best testresult for the wall thickness/diameter ratio of the pipe to betested.The acceptance criterion is:

— acceptance level L2/C according to ISO 9303.

1423 Manual ultrasonic inspection of the pipe body fortransverse imperfections shall be performed in accordancewith the requirements in ISO 9305. The probe angles shall bechosen to obtain the best test result for the wall thickness/diameter ratio of the pipe to be tested.The acceptance criterion is:

— acceptance level L2/C according to ISO 9305.

Welded pipe; manual ultrasonic testing of welds1424 Manual ultrasonic testing and testing of welds inwelded pipe for longitudinal and transverse imperfections shallbe performed on untested pipe ends and to confirm the pres-ence or absence of a defect when automated NDT systemsgives signals equal to or greater than the threshold level.1425 Manual ultrasonic testing of welds in C-Mn steel mate-rial with C-Mn steel weld deposits shall be performed inaccordance with B300 except that B314, B317, B321, B322and B338 shall not apply. Manual ultrasonic testing of welds in HFW pipe 1426 The reference block shall be according to H910.1427 One or more of the following probe configurationsshall be used:

— Single pulse echo probes with the angle of incidence asperpendicular to the radial centreline of the weld as possi-ble.

— Tandem probes with the angle of incidence as perpendic-ular to the radial centreline of the weld as possible.

1428 The probe angle for the initial scanning shall be chosento obtain the best possible test result for wall thickness anddiameter of the pipe to be tested and such that the angle of inci-dence is as perpendicular as possible to the weld bevel. 1429 The DAC shall be constructed using the notches in thereference block. A 2-point DAC shall only be used if scanningis limited to one full skip or less. If scanning is performedusing more than one full skip, a 3-point DAC shall be estab-lished as a minimum.1430 The acceptance criterion is:

— no maximised echo from any probe shall exceed the DAC.

Manual ultrasonic testing of welds in CRA materials and inclad pipe1431 Ultrasonic testing of welds in CRA materials withCRA (duplex, other stainless steels and nickel alloy steel) welddeposits will in order to achieve an adequate detection ofimperfections normally require that special reference blocksand probes are used for testing of these materials. Unless it canbe demonstrated as required in B418 and H429 that use of lowfrequency shear wave angle probes gives acceptable detection,manual ultrasonic testing of the CRA weld deposit in the rootshall be performed as required in B4001432 Angle beam probes shall be available in angles, or beprovided with wedges or shoes, ranging from 30° to 75°, meas-ured to the perpendicular of the surface of the pipe beingtested. Probe angles shall be selected as required in B300. Theprobe angles shall be chosen to obtain the best possible testresult for wall thickness and diameter of the pipe to be testedand such that the angle of incidence is as perpendicular as pos-sible to the weld bevel in the area covered by the probe. If shearwave angle probes are used for testing of the root the frequencyshall be 2 MHz or lower.1433 The reference standard for testing with shear angleprobes shall be according to H1208 and H1209.Testing sensitivities shall be established as follows:

— For testing of longitudinal imperfections in the weld vol-ume outside the root area, the DAC shall be constructedusing the longitudinal external and internal notches. A 2-point DAC shall only be used if scanning is limited to onefull skip or less. If scanning is performed using more thanone full skip, a 3-point DAC shall be established as a min-imum.

— For testing of the root area longitudinal imperfections sen-sitivity setting shall be against the notch in the root area onthe opposite side of the weld and the response set to 50%of full screen height.

— For testing of transverse imperfections, the DAC shall beconstructed using the 1.6 mm diameter through drilledholes at the weld centreline with 2 points (e.g. ½ and fullskip).

1434 Scanning for transverse indications shall be performed"on bead". Probes with beam angles of 45° and 60° shall beavailable. 1435 The acceptance criteria are:

— No maximised indications exceeding DAC for longitudi-nal and transverse indications.

— No maximised indications in the root area exceeding 50%of full screen height.

When compression wave angle probes are used, other types ofreflectors are used and the acceptance criteria shall be speci-fied and agreed accordingly.Manual ultrasonic testing of welds in SAWL and SAWH pipe1436 The reference standard shall be according to H1309and H1310.1437 Angle beam probes shall be available in angles, or beprovided with wedges or shoes, ranging from 30° to 75°, meas-ured to the perpendicular of the surface of the pipe beingtested. Probe angles shall be selected as required in B300.1438 Testing sensitivities shall be established as follows:

— For testing of longitudinal imperfections in the weld vol-ume, the DAC shall be constructed using the longitudinalexternal and internal notches. A 2-point DAC shall only beused if scanning is limited to one full skip or less. If scan-ning is performed using more than one full skip, a 3-pointDAC shall be established as a minimum

— For testing of transverse imperfections, the DAC shall be

DET NORSKE VERITAS


constructed using the 1.6 mm diameter through drilledholes at the weld centreline with 2 points (e.g. ½ and fullskip).

1439 Scanning for transverse indications shall be performed"on bead". Probes with beam angles of 45° and 60° shall beavailable. Use of 4 MHz probes shall be preferred.1440 Acceptance criterion is:

— no maximised indications exceeding DAC

Manual ultrasonic testing of welds in CRA materials and CRAweld deposits/materials.1441 Refer to H424 through H431. Ultrasonic testing ofCRA materials and welds with CRA (duplex, other stainlesssteels and nickel alloy steel) weld deposits will in order toachieve an adequate detection of imperfections require thatspecial calibration blocks and probes are used for testing ofwelds in these materials. Angle probes generating compressionwaves must normally be used in addition to straight beamprobes, angle shear wave probes and creep wave probes. 1442 Unless it can be demonstrated as required in B418 andH429 that use of low frequency shear wave angle probes onlygives acceptable detection, manual ultrasonic testing of CRAmaterials and welds with CRA weld deposits shall be per-formed as required in B400.1443 Acceptance criteria manual ultrasonic testing of CRAmaterials and welds with CRA weld deposits performed withangle compression wave probes are:

— according to Table D-6.

Manual magnetic particle testing1444 Manual magnetic particle surface testing shall be per-formed in accordance with B500 and ISO 13665. 1445 Manual magnetic particle testing of pipe ends shall beperformed in accordance with B500 and ISO 13664.

1446 Manual magnetic particle testing of welds shall be per-formed as required by B500. 1447 Acceptance criteria shall be according to the relevantrequirements of this subsection.Manual liquid penetrant testing1448 Manual liquid penetrant surface testing and testing ofpipe ends shall be performed in accordance with ISO 12095.1449 Manual liquid penetrant testing of welds shall be per-formed in accordance with B600, paragraphs 602 through 605. 1450 Acceptance criteria shall be according to the relevantrequirements of this subsection.Manual eddy current testing1451 Manual eddy current surface testing and testing of pipeends shall be performed in accordance with ISO 9304. 1452 Manual eddy current testing of welds shall be per-formed in accordance with B700, paragraphs 702 through 708and ISO 9304 (eddy current testing)1453 Acceptance criteria shall be according to the relevantrequirements of this subsection.

H 1500 Non-destructive testing of weld repair in pipe 1501 Weld repair of the body of any pipe and of the weld inHFW pipe is not permitted.1502 Before re-welding, complete removal of the defectsshall be confirmed by magnetic particle testing, or liquid pen-etrant testing for non- ferromagnetic materials.1503 A repaired weld shall be completely re-tested usingapplicable NDT methods in accordance with H800 through1300. Alternatively, manual NDT may be performed in accordancewith H1400 and with acceptance criteria in accordance withthe requirements in H1400. In this case, manual ultrasonic test-ing shall be governing for embedded defects.

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Offshore Standard DNV-OS-F101, October 2007 App.E –

APPENDIX E AUTOMATED ULTRASONIC GIRTH WELD TESTING

A. GeneralA 100 Scope101 This Appendix details the examination requirements forthe automated ultrasonic testing of pipeline girth welds.102 The Appendix applies when automated ultrasonic test-ing (AUT) is performed on pipeline girth welds.

A 200 References

a) American Society for Testing Materials - E 317-94: Stand-ard Practice for Evaluating Performance Characteristics ofPulse Echo Testing Systems Without the Use of ElectronicMeasurement Instruments

b) EN12668-1 Non destructive testing - Characterisation andverification of ultrasonic examination equipment- Part 1:Instruments

c) EN12668-2 Non destructive testing - Characterisation andverification of ultrasonic examination equipment- Part 2:Transducers

d) EN12668-3 Non destructive testing - Characterisation andverification of ultrasonic examination equipment- Part: 3:Combined equipment

e) EN583-6 Non destructive testing - Ultrasonic examinationPart 6 - Time-of-flight diffraction as a method for defectdetection and sizing

B. Basic RequirementsB 100 General101 The primary requirement to any AUT system is that itsperformance is documented in terms of adequate detection andsizing, or rejection abilities in relation to specified / deter-mined acceptable defects.102 The ultrasonic system to be used shall be acceptedthrough qualification, see Subsection H.103 The ultrasonic system may use pulse echo, tandem,time-of-flight diffraction (TOFD) and/or through transmissiontechniques employing either fixed or phased arrays. It shallhave a fully automatic recording system to indicate the loca-tion of defects and the integrity of acoustic coupling. If a zonalapproach is used, the recommended maximum zone height is 3mm. The zonal approach shall be combined with root and weldvolume mapping channels, and preferably TOFD. The zonalconcept may be deviated from. This requires an adequate tech-nical description of the alternative approach, and a systemqualification according to Subsection H.104 The information provided by all AUT channel typesshall be actively used in order to ensure adequate defect detec-tion and sizing.105 The ultrasonic system may include scanner heads andsystem set-up specifically configured for testing of repairs. Asa minimum the AUT system with its normal set-up, but withwider gates shall be used to confirm that AUT detected defectshave been removed. During this special attention shall also bemade to TOFD channel indications, and indications outside thenormal gate settings.Due to the wide variation in repair weld groove shapes thatmay limit the detection capabilities of the system, manual UT,or a dedicated semi-automatic UT system, shall support theAUT on weld repairs unless the groove shape is controlled to

be within given tolerances and the scanner head is configuredaccordingly. For supplementary UT, the provisions of Appen-dix D apply.Supplementary UT support is not required if weld repairgrooves are made with mechanical equipment that consistentlyprepares the same groove geometry, and the repair AUT isqualified according to Subsection H.106 The ultrasonic system shall incorporate facilities fordetection of transverse defects, when it is clearly identified thatthe weld process, parent material, application and environmen-tal condition may increase the risk for transversal type flaws.107 For variations from nominal wall thickness outside astandard deviation value (SD) of 0.7 mm, additional valida-tions or qualification tests are required. These tests shall reflectthe total expected wall thickness variation, and provide evi-dence of 100% coverage of the fusion face and the root area.The (SD) is calculated as follows:SD = (tmax – tmin)/ The tmax and tmin should be based on data from the pipe man-ufacture. If data from pipe manufacture are not available, SDshould be calculated based on the specified wall thickness tol-erance.108 Counter bores may be used to compensate for largethickness variations if the counter bore is machined to provideparallel external and internal surfaces before the start of thetaper. The length of the parallel surfaces shall at least be suffi-cient to allow scanning from the external surface and sufficientfor the required reflection off the parallel internal surface. 109 Weld deposits in duplex, austenitic stainless steels andnickel alloys have a coarse grain structure with variations ingrain size and structure resulting in unpredictable fluctuationsin attenuation. Duplex and austenitic stainless steel base mate-rials will have the same characteristics. Ultrasonic testing of welds with CRA (duplex, other stainlesssteels and nickel alloy steel) weld deposits will in order toachieve an adequate detection of imperfections require thatspecial calibration blocks and transducers are used for testingof welds in these materials. Angle transducers generating com-pression waves, must normally be used in addition to angleshear wave transducers and creep wave transducers.Creep wave transducers should be used for detection of subsurface defects close to the scanning surface. In general, using a combination of shear and compressionwave angle transducers is recommended since the detection of"open to surface" imperfections on the opposite surface of thescanning surface, e.g. incomplete penetration or lack of fusion,may increase using shear wave transducers. It must, however,be verified by using calibration blocks with actual weld con-nections that angle shear wave transducers are suitable.110 An operating Quality Assurance system shall be usedcovering the development of ultrasonic examination systems,testing, verification and documentation of the system and itscomponents and software against given requirements, qualifi-cation of personnel and operation of ultrasonic examinationsystems. The Quality Assurance system employed shall bedocumented in sufficient detail to ensure that AUT systemsused for field inspection will be designed, assembled and oper-ated within the essential variables established during the qual-ification and in all significant aspects will be equal to thequalified AUT system. ISO 9000 and ASTM E 1212 shallapply as basic requirements to the Quality Assurance system.The following shall be documented:

12

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Offshore Standard DNV-OS-F101, October 2007 – App.E

— document control— system development including establishing performance— requirements to the system, its components and calibration

blocks— selection/qualification/follow-up/auditing of suppliers/

subcontractors— procurement of system components and calibration blocks— verification of delivered system components and calibra-

tion blocks against given requirements— marking/identification of system components and calibra-

tion blocks complying with given requirements— control and verification of software development/changes— design of AUT system(s) set-up for specific field opera-

tion conditions/requirements— assembly of AUT systems for field operation from verified

components in stock, including identification of the sys-tem and identification/documentation of its components,calibration block(s) and spare parts

— verification/testing of AUT systems for field operation— operational checks and field maintenance of AUT systems— documentation/verification of in field modifications of

AUT systems— return of field systems, dismantling, check/repair/upgrad-

ing of system components— verification of repaired/upgraded system components

against given requirements— AUT operator training and qualification.

B 200 Documentation201 The configuration of the ultrasonic system shall for eval-uation purposes be described and documented with regard to:

— brief functional description of the system— reference to the code, standard or guideline used for design

and operation of the system— description of the Quality Assurance system— equipment description— limitations of the system with regard to material or weld

features including sound velocity variations, geometry,wall thickness, size, surface finish, material composition,etc.

— number and type of transducers, or phased array set upwith description of characteristics and set-up

— number of and height of examination zones, where rele-vant

— gate settings— function of scanning device— ultrasonic instrument, number of channels and data acqui-

sition system— recording and processing of data— calibration blocks— coupling monitoring method— temperature range for testing and limitations— coverage achieved— maximum scanning speed and direction— reporting of indications and documentation of calibration

and sensitivity settings.

B 300 Qualification301 Automated ultrasonic systems shall be qualified and theperformance of the system shall be documented.Further guidance is given in Subsection H.For applications other than ferritic steel girth weld examina-tions, specific qualifications programs shall be designed andagreed upon.

B 400 Ultrasonic system equipment and componentsGeneral requirements

401 The system shall be capable of examining a completeweld including the heat affected zone in one circumferentialscan. This requirement may, as agreed, be deviated from forvery thick / small diameter pipe, if it is not possible to coverthe whole depth range in one scan.402 There shall be recordable signal outputs for at least each2 mm of weld length.403 The ultrasonic instrument shall provide a linear A-scanpresentation. The instrument linearity shall be determinedaccording to the procedures detailed in ASTM-317-01 orEN12668. Instrument linearity shall not deviate by more than5% from ideal.The assessment of ultrasonic instrument linearity shall havebeen performed within 6 months of the intended end use date.For production AUT with an expected duration exceeding 6months, but less than one year, the assessment of instrumentlinearity may be performed immediately before the start ofwork.A calibration certificate shall be made available upon request.Specific requirements for ultrasonic instruments using multi-ple channels, pulse echo, tandem and/or through transmissiontechniques.404 The instrument shall provide an adequate number ofinspection channels to ensure the examination of the completeweld through thickness in one circumferential scan, if possible(see B401). Each inspection channel shall provide:

— pulse echo or through transmission modes— one or more gates, each adjustable for start position and

length— gain adjustment— recording threshold between 5 and 100% of full screen

height— recording of either the first or the largest signal in the gated

region— signal delay to enable correlation to distance marker posi-

tions (real time analogue recording only)— recordable signal outputs representing signal amplitude

and sound travel distance— specific requirements to ultrasonic instruments using the

ToFD technique

405 The instrument shall provide a ToFD B-scan image.ToFD function software shall incorporate adequate facilitiesfor online indication assessment using range calibrated cur-sors. A-scan reference and numerical translation of time offlight positions shall be incorporated.Depth range efficiency shall be identified for each ToFD setup. It may be required to employ two or more ToFD channelsin order to increase reliability over the through thickness rangebeing inspected. For thicknesses above 50 mm at least twoTOFD channels are recommended.406 The instrument shall fulfil the requirements to ultrasonicinstruments described in EN12668-1 and EN583-6, Chapter 6"Equipment requirements"Specific requirements to ultrasonic instruments using phasedarrays.407 The phased array system shall incorporate means forperiodical verification of the function of required active ele-ments necessary to maintain a specific focal law.408 A system preventing any unqualified alterations toagreed focal laws shall be implemented for the phased arrayAUT system.409 If additional conventional transducers to the phasedarray ones are used, for example for transverse inspection andToFD, the information for all transducers shall be available inthe same set up and recording system.

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The recording system410 The recording or marking system shall clearly indicatethe location of imperfections relative to the 12 o'clock positionof the weld, with a ± 1% accuracy or 10 mm, whichever isgreater. The system resolution shall be such that each segmentof recorded data from an individual inspection channel doesnot represent more than 2 mm of circumferential weld dis-tance.Acoustic coupling411 Acoustic coupling shall be achieved by contact or cou-plant column using a liquid medium suitable for the purpose.An environmentally safe agent may be required to promotewetting, however, no residue shall remain on the pipe surfaceafter the liquid has evaporated.The method used for acoustic coupling monitoring and the lossin signal strength defining a "loss of return signal" (loss of cou-pling) shall be described.Transducers412 Prior to the start of field weld examination, details of thetypes and numbers of transducers or focal laws shall be speci-fied. Once agreed, there shall not be any transducer or focallaw design changes made without prior agreement. Transduc-ers other than phased arrays shall be characterised according toEN12668-2. Transducers shall be documented with respect tomanufacturer, type, characteristics and unique identification(serial number).Transducer characteristics shall include (not all parameters areapplicable to phased array transducers):

— frequency— beam angle— wedge characteristics— beam size— pulse shape— pulse length— signal to noise— focus point and length for focused transducers.

413 Transducers used for zonal discrimination shall give sig-nals from adjacent zones (overtrace) at least 6 dB lower andnot more than 10 dB lower than the peak signal from the cali-bration reflector representing the zone of interest. 414 TOFD transducers shall be optimised for the wall thick-ness to be tested and the refracted angle shall be the same fortransmitter and receiver. Frequency, damping and incidentangle shall be chosen to limit the dead zone formed by the lat-eral wave.415 When required, transducers shall be contoured to matchthe curvature of the pipe.

B 500 Calibration (reference) blocks501 Calibration blocks shall be used to set AUT system sen-sitivity, and to verify the inspection system for field inspectionand to monitor the ongoing system performance. Calibrationblocks shall be manufactured from a section of pipeline spe-cific linepipe. The wall thickness of the pipe used for calibra-tion blocks shall preferably correspond to the average wallthickness of the pipes used, unless a number of calibrationblocks are needed to cover wall thickness variations outsidethe limitations given in B108.502 For examination of austenitic or austenitic/ferritic welddeposits the calibration block shall contain a weld. The weldshall be made using the welding procedure and bevel prepara-tion to be applied during construction. Reference reflectorsshall normally be positioned opposite to the scanning side suchthat the ultrasonic beams pass through the weld metal beforereaching the reference reflectors. Notches shall not be used asreference reflectors for compression wave angle transducers.

503 Acoustic velocity and attenuation measurements shallbe performed on material from all sources of pipe material sup-ply to be used. These measurements shall be performedaccording to Subsection J100 unless an equivalent method isagreed. If differences in acoustic velocity for the same nominalwall thickness from any source of supply results in a beamangle variation of more than 1.5°, specific calibration blocksshall be made for material from each source of supply showingsuch variations.504 Details of the specific weld bevel geometries includingrelevant dimensions and tolerances shall be provided in orderto determine the particulars and numbers of calibration blocksrequired. 505 Type and size of calibration reflectors shall be deter-mined by the required sensitivity to achieve the necessaryProbability of Detection (PoD) and sizing capability as deter-mined by the smallest allowable defect deriving from theagreed acceptance criteria. The preferred principal calibrationreflectors are normally flat bottom holes (FBHs) and surfacenotches. Other reflector dimensions and types may be used, ifit is demonstrated during the system qualification that thedefect detection and sizing capabilities of the system is accept-able. Specific notches for ToFD may be incorporated, to checkTOFD system functionality.506 The calibration blocks shall be designed with sufficientsurface area so that the complete transducer array will traversethe target areas in a single pass.507 Drawings showing the design details for each type ofcalibration block shall be prepared. The drawings shall show:

— the specific weld bevel geometry, dimensions and toler-ances

— the height and position of examination zones— the calibration reflectors required and their relative posi-

tions — the ultrasonic path associated with each reflector.

508 The calibration block shall be identified with a hardstamped unique serial number providing traceability to theexamination work and the material source of supply for whichthe standard was manufactured. Records of the correlationbetween serial number and wall thickness, bevel design, diam-eter, and ultrasound velocity shall be kept and be available.The machining tolerances for calibration reflectors are:

509 The lateral position of all calibration reflectors shall besuch that there will be no interference from adjacent reflectors,or from the edges of the blocks.510 Holes shall normally be protected from degradation bycovering the hole with a suitable sealant. Filling of surfacenotches and other near surface reflectors may influence thereflecting ability of the reference reflector and shall beavoided.511 Dimensional verification of all calibration reflectors andtheir position shall be performed and recorded according to adocumented procedure.512 Whenever possible, an AUT system similar to that usedduring field inspection shall be successfully calibrated againstthe calibration block after dimensional verification of theblock. The set-up data shall be recorded and the same data used

(a) Hole diameters ± 0.2 mm(b) Flatness of FBH ± 0.1 mm(c) All pertinent angles ± 1°(d) Notch depth ± 0.1 mm(e) Notch length ± 0.5 mm(f) Central position of reference reflectors ± 0.1 mm(g) Hole depth ± 0.2 mm

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to verify that any additional/spare calibration blocks will notgive significantly different calibration results.513 A calibration block register shall be established. Theregister shall include all calibration blocks, including spareblocks, to be used, identified with a unique serial number andinclude the drawings, dimensional verification records, ultra-sound velocity, name of the plate/pipe manufacturer and theheat number.

B 600 Recorder set-up601 Channel output signals shall be arranged on the record-ing media in an agreed order. The function of each channelshall be clearly identified. The hard copy recording shall becorrected to account for any difference introduced due to dif-ferent circumferential positions of the transducers.602 Distance markers shall be provided on the recording atintervals not exceeding 100 mm of circumferential weldlength.603 The scanning direction (clockwise or anti-clockwise)shall be clearly described and referred to an identifiable datum,and shall be maintained throughout the duration of the fieldweld examination.

B 700 Circumferential scanning velocity701 The maximum allowable circumferential scanningvelocity shall be determined so that there are at least 3 pulsefirings within each 6 dB beam width at the appropriate operat-ing distance of all transducers within the an array.

B 800 Power supply801 The ultrasonic system shall have a dedicated power sup-ply. There shall be provisions for alternative power supply incase of failure in the main power supply. There shall be no lossof inspection data as a result of a possible power failure.

B 900 Software901 All recording, data handling and presenting software,including changes thereto, shall be covered by the QualityAssurance system and all software versions shall be identifia-ble by a unique version number.902 The software version number, and for phased arrayequipment also each identified set-up (executable focal lawprogramme) in use, shall be clearly observable on all displayand printout presentations of calibration and examinationresults.903 For phased array equipment, each identified set-up (exe-cutable focal law programme) shall be available for review. 904 Changes to an executable focal law programme shall notbe possible without a simultaneous change in the versionnumber.905 Software updates shall not be performed on systems dur-ing field examination use.

B 1000 Reference line, band position and coating cut-backReference line1001 Prior to welding a reference line shall be scribed on thepipe surface at a fixed distance from the centreline of the weldpreparation on the inspection band side. This reference lineshall be used to ensure that the band is adjusted to the same dis-tance from the weld centreline as to that of the calibrationblock.Guiding band positioning1002 The tolerance for band positioning is ± 1 mm relativeto the weld centreline. The band can be positioned either wholly on the bare pipe oron the corrosion coating.

Positioning of the band on the corrosion coating will requirethat the coating thickness is not excessive and that the coatingis sufficiently flat and will remain hard enough at the temper-atures in the pipe resulting from preheat and welding to avoidthat the band supports slips or penetrates the coating.Positioning of the band partly on bare pipe and partly on thecorrosion coating may result in instability problems for thescanner and should be avoided.Coating cut back1003 The cut-back of the corrosion coating to bare pipe shallbe wide enough to accommodate the footprint of all transduc-ers at the required stand-off distance + minimum 20 mm. Thecut-back of any weight coating shall allow placing the bandwholly on the bare pipe or on the corrosion coating, as appli-cable, and sufficient to avoid interference between weightcoating and scanner.The coating cut back required allowing for scanner mountingand movement shall be clearly identified in the operating man-uals.

B 1100 Reference line tools1101 The tool used to align the scanning band to the refer-ence line shall be adjusted to account for weld shrinkage.Shrinkage is determined by marking the reference line on bothpipe ends during WPQ or for the first 25 welds, and then meas-uring the distance between them after welding.The tools used for marking the reference line for band position-ing, shall give accuracy in the position of the scribe line of ±0.5 mm relative to the bevel root face. The accuracy of eachscribe line tool shall be documented and each tool shall beuniquely identified.

B 1200 Operators1201 Details of each AUT operator shall be provided prior tostart of field weld examination.1202 Operators performing interpretation shall be certifiedto Level 2 by a Certification body or Authorised qualifyingbody in accordance with EN 473, ISO 9712 or the ASNT Cen-tral Certification Program (ACCP). In addition they shall doc-ument adequate training and field experience with theequipment in question, by passing a specific and practicalexamination. If requested, they shall be able to demonstratetheir capabilities with regard to calibrating the equipment, per-forming an operational test under field conditions and evaluat-ing size, nature and location of imperfections.1203 Operators who are not accepted shall not be used, andoperators shall not be substituted without prior approval. Incase additional operators are required, details of these shall beaccepted before they start to work.1204 One individual shall be designated to be responsible forthe conduct of the ultrasonic personnel, the performance ofequipment, spare part availability and inspection work, includ-ing reports and records.1205 The operators shall have access to technical supportfrom one individual qualified to Level 3 at any time duringexecution of the examination work.

B 1300 Spares1301 There shall be a sufficient number of spare parts avail-able at the place of examination to ensure that the work canproceed without interruptions. The type and number of sparesshall be agreed.

B 1400 Slave monitors1401 The system shall include the possibility to provideslave monitors for use by supervising personnel, if agreed.

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C. ProcedureC 100 General101 A detailed AUT Procedure shall be prepared for eachweld joint geometry to be examined prior to the start of anywelding. The procedure is as a minimum, and as relevant forthe equipment in question, to include:

— functional description of equipment— reference standards and guidelines controlling equipment

maintenance— instructions for scanning device, ultrasonic instrument,

ultrasonic electronics, hard- and software for recording,processing, display, presentation and storage of inspectiondata

— number of examination zones for each wall thickness to beexamined, as relevant

— transducer configuration(s), characteristics, types, cover-age; and/or focal law details

— description/drawings of calibration block(s), includingtype, size and location of all calibration reflectors

— pre-examination checks of equipment— methodology for sensitivity setting and for fusion zone

transducers; overtrace (signal amplitude from adjacentzones) requirements consistent with the overtrace used asbasis for establishing height sizing corrections for ampli-tude sizing

— gate settings— equipment settings— threshold settings— the added gain above PRL (D102) to be used for mapping

channels— dynamic verification of set-up— signal strength defining a "loss of return signal" (loss of

coupling)— visual examination of scanning area, including surface

condition and preparation— identification of inspection starting point, scanning direc-

tion, and indication of length inspected— method for scanner alignment and maintenance of align-

ment— verification of reference line and guide band positioning— maximum allowed temperature range— control of temperature differentials (pipe and calibration

block)— calibration intervals— calibration records— couplant, coupling and coupling control— operational checks and field maintenance— transducer and overall functional checks— height, depth and length sizing methodology— acceptance criteria, or reference thereto— instructions for reporting including example of recorder

chart and forms to be used— spare part philosophy.

102 The AUT procedure shall be submitted for acceptance.

D. Calibration (Sensitivity Setting)D 100 Initial static calibrationTransducer positioning and Primary Reference Sensitivity 101 The system shall be optimised for field inspection inaccordance with the details given in the AUT procedure andusing the relevant calibration block(s). The calibration blockshall have the same orientation (vertical/horizontal) as the pipeto be tested, unless it has been proven through the qualificationtests that differences in response are negligible.102 The gain level required to produce the peak signal

response is the Primary Reference Level (PRL) for that reflec-tor. Fusion zone channels103 Pulse echo and tandem transducers shall be positioned atits operating (stand-off) position and adjusted to provide apeak signal from its calibration reflector. In the case of phasedarrays, the focal laws shall be designed to provide a peak signalfrom each of the calibration reflectors as appropriate. This sig-nal shall be adjusted to the specified percentage of full screenheight (FSH). TOFD channels104 For single TOFD channels, the transducer spacing shallbe selected to place the theoretical crossing of beam centres atthe weld centreline at 66 to 95% of the wall thickness. For double TOFD channels the theoretical crossing of beamcentres at the weld centreline shall be at 66 to 95% of the wallthickness for one channel and approximately 33% of the wallthickness for the other channel.The amplitude of the lateral wave shall be between 40 and 80%of full screen height (FSH). In cases when use of the lateralwave is not applicable, e.g. surface conditions and steep beamangles, the amplitude of the back wall signal shall be set atbetween 12 to 24 dB above FSH. When use of neither the lat-eral wave nor the back wall signal is applicable, the sensitivityshould be set such that the noise level is between 5 and 10% ofFSH. Mapping channels105 Each transducer shall be positioned at its operating(stand-off) position and adjusted to provide a peak signal fromits calibration reflector. In the case of phased arrays, the focallaws shall be designed to provide a peak signal from each ofthe calibration reflectors as appropriate. This signal shall beadjusted to the specified percentage of FSH. Normally a gain increase in the range of 4 to 10 dB over thegain necessary to obtain the specified percentage of FSH isrequired to obtain the production scanning sensitivity. Thisgain shall not be added during sensitivity setting, dynamic cal-ibration and calibration verification during field examination.

D 200 Gate settings201 With each transducer positioned for a peak signalresponse from the calibration reflector the detection gates shallbe set as detailed in the agreed AUT procedure and as detailedbelow.Fusion zone channels202 The detection gates are to be set with each transducer /focal law positioned for the peak signal response from the cal-ibration reflector. The gate shall start before the theoreticalweld preparation and a suitable allowance shall be included toallow for the width of the heat affected zone, so that completecoverage of the heat affected zone is achieved. The gate endsshall at least be after the theoretical weld centreline, includinga suitable allowance for offset of the weld centreline afterwelding. 203 For specific applications, e.g. for austenitic/duplexweldments with angle compression waves with the referencereflectors positioned at the far side of the weld, an extension ofthe gate onto the far bevel and HAZ may be required. Similar considerations may apply in the root area related tomonitoring of guidance band offset. ToFD technique204 Ideally the time gate start should be at least 1 µs prior tothe time of arrival of the lateral wave, and should at leastextend up to the first back wall echo. Because mode convertedechoes can be of use in identifying defects, it is recommendedthat the time gate also includes the time of arrival of the first

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mode converted back wall echo.205 As a minimum requirement, the time gate shall at leastcover the depth region of interest.206 Where a smaller time gate is appropriate, it will be nec-essary to demonstrate that the defect detection capabilities arenot impaired.Mapping channels207 For mapping channels the gates shall be set to cover theHAZ and the total weld volume dedicated to the transducer orfocal law.

D 300 Recording ThresholdThreshold level301 It shall be verified that the threshold level, based on datafrom the AUT system qualification, is set low enough to detectthe minimum height critical defect identified in the acceptancecriteria (see Subsection H300).302 The threshold levels shall in any case not be set higherthan required in the following.Fusion zone channels303 The recording threshold for fusion zone channels shallbe at least 6 dB more sensitive than the reference reflector,unless a different sensitivity is required for detection of indica-tions depending upon the size of reflectors used and the appli-cable acceptance criteria.TOFD technique304 The recording threshold for ToFD is normally not rec-ommended to be changed from the calibration threshold. How-ever, a change of threshold may be prescribed in the procedure.Mapping channels305 The recording threshold for mapping channels shall beat least 14 dB more sensitive than the reference reflector sig-nal.306 Sufficient data shall be recorded on a “set-up sheet” toenable a duplication of the original set-up at any stage duringfield inspection.As a minimum the PRL, the signal to noise (S/N) ratio, thestand-off distance for each transducer, the transducer caseheight at each corner for each transducer (with an accuracy of0.1 mm) and settings for gate start and gate length for eachchannel shall be recorded.

D 400 Dynamic calibrationDetection channels401 With the system optimised, the calibration block shall bescanned. The position accuracy of the recorded reflectors rela-tive to each other shall be within ± 2 mm, and with respect tothe zero start within ± 10 mm.402 For all phased array focal laws or transducers the record-ing media shall indicate the required percentage of FSH andlocate signals from each calibration reflector in its correctlyassigned position. The overtrace shall be in accordance withthe requirements given in the AUT procedure.Coupling monitor channels403 The coupling monitor channels shall indicate no loss ofreturn signal as required by the procedure.

D 500 Recording of set-up data501 The calibration qualification chart shall be used as theinspection quality standard to which subsequently producedcalibration charts may be judged for acceptability. This record-ing shall be kept with the system Log Book. For phased arrayequipment also the identified set-up (executable focal law pro-gramme) used shall be recorded.

502 In addition to the qualification chart required above, anychanges in the data records made in accordance with D306above shall be recorded.The “set-up sheet” shall after dynamic calibration include as aminimum:

— PRL and the signal to noise (S/N) ratio for each transducer— the stand-off distance for each transducer and alignment of

tandem transducers— the settings for gate start and gate length for each channel — the gain to be added to any channel during field examina-

tion— filtering settings, when applicable— the order of transmitters and receivers— the transducer case height at each corner for each trans-

ducer and the protrusion of each “carbide tip” with anaccuracy of 0.1 mm

— calibration block identification.

E. Field InspectionE 100 Inspection requirementsGeneral requirements101 The ultrasonic system used for examination during pro-duction shall in all essential aspects be in compliance with theset-up and configuration of the system used for system qualifi-cation (see Subsection H).Documentation102 The following documentation shall be available at theplace of field examination:An AUT system dossier for each operating AUT systemincluding performance/characteristics data and identificationof at least:

— pulser/receiver— transducers— umbilical — encoder— software version and executable focal law programmes

(when applicable)— other essential equipment.

An AUT system spare parts dossier including:

— performance/characteristics data and identification ofessential spare parts.

A calibration block register including:

— the documentation for each calibration block, includingspares, as required by B513.

An AUT personnel qualification dossier including:

— certificates for all AUT personnel.

An AUT procedures dossier including:

— AUT procedures to be applied— AUT system check and maintenance instructions— work instructions for AUT personnel.

Additional information including:

— other NDT procedures— AUT and NDT acceptance criteria.

103 The AUT system dossier shall be updated when changesof parts/components are made and shall at all times reflect thecurrent configuration of the AUT system in use.

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The AUT system spare parts dossier shall be updated when-ever parts/components are replaced or new parts/componentsarrive and shall at all times reflect the number of spares avail-able.System Log Book104 The System Log Book shall be kept at the place ofinspection, and be made available for review upon request.The system log book shall be continuously updated and at leastinclude the following information:

— set-up data as required in D500— the calibration qualification chart(s)— replacement of main components with spares from stock— replacement of calibration block— results from operational checks— results of periodical verifications (linearity checks, cali-

bration block wear, element verification for phased arraytransducers etc.)

— weld inspection- and calibration charts.

105 Hard copy recordings for each calibration scan (andphased array set up file, if appropriate) shall be includedsequentially with the weld inspection charts. The last weldnumber examined before calibration and the time at which thecalibration was performed shall appear on each calibrationchart.Pre- examination tests106 Before the ultrasonic system is used for field examina-tion of production welds the system shall be tested. After cali-bration of the complete system using the applicable “set-upsheet” parameters, the calibration block shall be scanned. Ifany of the echo amplitudes from the reflectors of the calibra-tion block deviate more than 2 dB from the initial calibration,corrections shall be made.The system shall not be used until 5 successive satisfactoryscans are obtained.At least one scan shall be performed with the scanning surfacewiped dry. The coupling monitor channels shall indicate lossof return signal as required by the procedure.In addition, a power failure shall be simulated and operation ofthe system on the alternative power source with no loss or cor-ruption of examination data shall be verified.Verification of Calibration 107 The calibration of the system shall be verified by scan-ning the calibration block before and after inspection of eachweld. The gain added to any channel for field examinationshall be removed during verification scans.108 If agreed, the frequency of verification scans may bereduced to a minimum of 1 scan for each 10 consecutive welds.109 The verification scans shall not show amplitude changesin any channel outside ± 2 dB from the reference calibrationchart (see D501).110 The peak signal responses from each verification scanshall be recorded. Any gain changes required to maintain thePRL in the set-up sheet (see D502) shall be recorded. Re-calibration111 The system shall be re-calibrated and a new referencecalibration chart shall be established according to SubsectionD if a verification scans shows amplitude changes in any chan-nel outside ± 2 dB from the reference calibration chart or ifgain changes outside ± 2 dB are required to maintain the PRLin the set-up sheet.112 The system shall also be re-calibrated and a new refer-ence calibration chart and a new set-up sheet established:

— at any change of calibration block— at any change of nominal wall thickness

— at any change of components, transducers, wedges or afterresurfacing of transducers

— before and after examination of repairs— after any adjustments to scanner head or transducers— after any change in the order of transmitters and receivers

and filtering settings.

Weld identification113 Each weld shall be numbered in the sequence used in thepipe tracking system.114 The starting point for each scan shall be clearly markedon the pipe and the scan direction shall be clearly marked usingan arrow. If the scanning direction is changed from the regulardirection, this shall be noted on the records of the scan.

E 200 Operational checks201 Operational checks shall be performed according to adocumented procedure. The execution of and the results of theoperational checks shall be recorded in the system log book.202 The following operational checks shall be performed forevery weld inspected:

— reference line shall be within required tolerance andclearly marked around the pipe circumference

— the scanning surface shall be free of weld spatter and otherthat may interfere with the movement of transducers

— physical damage and loose connections in the band. bandposition shall be within a tolerance of maximum ± 1.0 mm

— the pipe surface temperature and the difference betweencalibration block temperature and pipe temperature shallbe within the required tolerance.

203 The following operational checks shall be performeddaily or at least once per shift:

— the scanner head shall be checked for physical damage andloose connections

— the bevel prepared at the bevelling station shall be of thespecific weld bevel geometry, dimensions and tolerancesshown on the drawings of the calibration block in use

— the calibration block in use shall be checked for physicaldamage and scanning tracks

— transducers shall not be rocking in the scanner and shall bein firm contact with the scanning surface. the transducersshall be firmly screwed onto the wedges. the transducerwear faces (wedges) shall be checked for scores whichmay cause local loss of contact

— the transducer stand-off distance shall be as recorded inthe set-up sheet within ± 0.5 mm

— the transducer case height and the difference between theprotrusions of carbide tips shall be as recorded in the set-up sheet within ± 0.2 mm

— the position accuracy of the chart distance markers shall beshall be ± 1 cm or better.

204 Other operational checks such as linearity checks andtransducer element verification checks (when applicable) andfield maintenance shall be performed according to the AUTsystem check and maintenance instructions.

Guidance note:Checking of transducer angles may require a custom made blacksince the standard V1 block may not be wide enough to includethe carbide tips during checks and due to that the gap between theV1 block and transducers with radiused surfaces will be too largefor adequate checks.


205 A verification scan shall be performed prior to resuminginspection after the operational checks required in E203 andany field maintenance. The verification scan shall meet therequirements given in E109.

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If necessary, a re-calibration shall be performed and a new ref-erence calibration chart shall be established according to Sub-section D.

E 300 Adjustments of the AUT system301 Adjustments to the AUT system other than correctingdeviations from the qualified set-up sheet following opera-tional checks and maintenance shall not be performed. Fineadjustments to the sensitivity settings by changing the gain set-tings to optimise the peak signal response to accommodatemechanical wear can be made within a window of ± 1.0 dB. 302 Practices such as changing transducer angles by liftingtransducer front and back by adjusting of carbides, changingstand-off distances and changing the order of transmitter/receivers etc. are not permitted.

F. Re-examination of WeldsF 100 General101 Welds shall be re-examined whenever any of the follow-ing occur:Sensitivity102 Welds examined at a sensitivity outside ± 2 dB from thePRL shall be re-examined.Coupling loss103 Welds exhibiting a loss of acoustic coupling over a cir-cumferential distance which exceeds the minimum allowabledefect length for the affected channel shall be re-examined.Out of calibration104 If a verification scan shows that the system is in any way"out of calibration", all welds examined since the last success-ful verification scan shall be re-examined.

G. Evaluation and ReportingG 100 Evaluation of indications101 Indications from weld imperfections shall be evaluatedagainst the defect acceptance criteria.102 Indications shall be evaluated following the height,depth and length sizing methodology given in the AUT proce-dure. All information available shall be used in the evaluationto avoid undersizing, - and excessive oversizing of indications.103 Indications recorded from sources other than weldimperfections shall be evaluated. Their nature shall be clearlyidentified in the examination report.104 All evaluations shall be completed immediately afterexamination of the weld.

G 200 Examination reports201 The examination results shall be recorded on a standardultrasonic report form. The reports shall be made available ona daily basis or on demand.202 The following items are as a minimum to be reported foreach indication found to be not acceptable or at the boundaryof acceptability:

— project reference— pipeline identification— weld identification/number— date— ultrasonic procedure number with associated revision— circumferential position of indication— height, depth and length of indication

— transverse location of defects/indications (US, DS, Cen-tral)

— maximum amplitude for each reported indication— indication type.

G 300 Inspection records301 The following inspection records shall be provided:

— a hard copy record of each weld examined— an assessment of the weld quality according to the accept-

ance criteria— hard copy records of all calibration scans— examination data in electronic form.

302 In lieu of hard copy records an alternative recordingmedia is acceptable. Where weld interpretation has been per-formed using digitally processed signals, the data files shall bestored and backed up immediately following the examinationof each weld. The stored data shall be in the same format asused by the operator to assess the acceptability of welds at thetime of examination.303 It agreed, a software package and one set of compatiblehardware shall be provided in order to allow the weld data fileto be retrieved in the same manner as the operator viewed thedata at the time of inspection.

H. QualificationH 100 General101 The AUT system shall be qualified for the applicationsit is intended used for. The qualification shall be based on therequired performance as identified by the requirements forProbability of Detection (PoD) and sizing ability; or, alterna-tively a requirement to defect rejection. The qualification levelshall be documented and independently verified.102 The qualification is AUT system specific and shall onlybe valid when all essential variables remain nominally thesame as covered by the documented qualification. This stand-ard does not require a new qualification to be performed pro-vided that the documented performance i.e. PoD and sizingability meets or exceeds the requirements for the specificapplication being considered.103 Qualification involves a technical evaluation of the AUTsystem and application in question combined with anyrequired practical tests.104 The qualification shall be based on a detailed and agreedqualification programme.

H 200 Scope201 A qualification programme shall document the follow-ing:

— fulfilment of the requirements to AUT systems accordingto this Appendix

— the repeatability of the AUT system under variable exam-ination conditions

— the sensitivity of the AUT system to the temperature oftested objects

— the ability of the AUT system to detect defects of relevanttypes and sizes in relevant locations

— the accuracy in sizing and locating defects.

H 300 RequirementsDetection301 The detection ability of an AUT system shall be deemedsufficient if the probability of detecting a defect of the smallestallowable height determined by an Engineering CriticalAssessment (ECA) or by other considerations is 90% shown at

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a 95% confidence level (i.e. a 90%|95% PoD). Sizing accuracy302 Sizing accuracy shall be established during the qualifi-cation programme. For this purpose it is required to demon-strate the accuracy over the range of expected defect sizes.Based on the determined sizing errors, the undersizing errortolerances giving less than or equal to 5% probability of under-sizing shall be determined and used in relation to any ECAspecified defect sizes. No specific tolerance is required for oversizing of indications.Oversizing of indications should however be within reasonablelimits since excessive oversizing will result in unnecessaryrepairs during pipeline construction. Rejection303 The detection criterion of H301 and the undersizing tol-erance specified in H302 may be combined into one rejectioncriterion: There shall be more than 85% probability of reject-ing a defect, which is not acceptable according to determinedECA criteria. This shall be shown at a 95% confidence level,i.e. a Probability of Rejection (PoR) of 85%|95% is required.This rejection criterion approach may be preferable when thetwo step process detection-sizing is not followed, e.g. whenacceptance or rejection is based directly on echo amplitudes, orsolely on AUT reported defect sizes.304 The AUT system shall be deemed unqualified for itspurpose with respect to ECA determined non-acceptabledefects if it is not possible to document adequate detection andsizing abilities according to H301 and H302, or adequate rejec-tion abilities according to H303.

H 400 Variables401 Variables, which must be taken into account during aqualification, include, but are not necessarily limited to:

— welding method and groove geometry— root and cap channels transducer set-up— transducer set-up for other channels (the number of these

channels may be increased or decreased provided there areno set-up changes)

— reference reflectors— system, data acquisition and data treatment— software version (except changes affecting viewing or dis-

play only).

H 500 Qualification programmeGeneral501 A full qualification programme for a specific applicationof an AUT system will in general comprise the followingstages:

1) Collection of available background material, includingtechnical description of the AUT system and its perform-ance.

2) Initial evaluation and conclusions based on availableinformation.

3) Identification and evaluation of significant parameters andtheir variability.

4) Planning and execution of a repeatability test programme,see H705 and H706.

5) Planning and execution of a temperature sensitivity testprogramme, see H707 and H708.

6) Planning and execution of detection ability and sizingaccuracy test programme, see H709 and H710.

7) Reference investigations.8) Evaluation of results from repeatability, temperature sen-

sitivity and detection ability and sizing accuracy trials.

502 The extent of each of these stages will be dependent onthe prior available information and documentation, and may betotally omitted if the prior knowledge is sufficient.503 As a minimum, a qualification will involve an assess-ment of the AUT system technical documentation, includingthe quality assurance system, and available information ondetection abilities and defect sizing accuracy. In many cases practical tests of the AUT system must be per-formed. Information pertaining to these practical tests is givenin H700.

H 600 Test welds601 Qualification testing shall be performed using test weldscontaining intentionally induced defects typical of thoseexpected to be present in welds produced with the weldingmethods to be used.602 The material and the weld geometry shall be as for theactual use of the equipment. Minor variations to for instancethe weld root groove, which are regarded irrelevant in relationto the AUT system, may be acceptable.If repair welds are to be covered by the qualification, a repre-sentative selection of these should also be included.603 The intentionally introduced defects shall vary in length,height and location. Too close spacing and stacking of thedefects shall be avoided. The number of defects in simulatedproduction welds shall be sufficiently high for each weldingand method/joint geometry to be used. 604 As a minimum 29 defects, or ultrasonically independentparts of defects, is required. Ultrasonically independent parts ofdefect are those several beam widths apart. For PoD/PoR deter-mination the required number of defects may be substantiallyhigher, in order to ensure sufficient statistical confidence.605 The locations where defects were intentionally inducedshall be recorded. The presence and sizes of the induceddefects in the test welds shall be confirmed. For this purposethe test welds shall be subject to supplementary NDT: Radiog-raphy and manual ultrasonic and preferably magnetic particleor eddy current testing. The reference point for all testing shallbe the same and shall be indicated by hard stamping on the testwelds. The techniques used for this testing shall be optimisedfor the weld geometries in question. The interpretation of radi-ographs and other test results should at least be performed bytwo individuals, initially working independently of each otherand later reporting their findings jointly.606 The report shall identify the identified defects from thesupplementary NDT in the test welds with respect to circum-ferential position, length, and height. The report shall be keptconfidential.

H 700 Qualification testing 701 The testing described in the following is required for afull qualification. If limited practical testing is performed thetesting and documentation requirements given shall apply asapplicable to the actual testing performed702 The test welds shall be subjected to testing by the AUTsystem.For testing, a low echo amplitude recording threshold shall beused. This threshold should be selected somewhat above thenoise level and the recording of echo amplitudes may be usedfor possible later determination of the examination thresholdsetting to achieve sufficient detection.703 The reference point for circumferential positioning shallbe a hard stamped on the test welds.704 The AUT system shall be set-up, calibrated and subjectto test runs before starting the formal qualification.

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Repeatability testing705 The testing shall include:

— one initial scan of the calibration block in the horizontalposition

— minimum 3 scans of the calibration block(s) with the cen-tre of the calibration block(s) in the 12 o’clock, 3 o’clockand 6 o’clock positions

— if relevant for the application of the AUT system the scansabove shall be repeated with the calibration block(s) in thevertical position

— minimum 3 scans of the calibration block with the bandoffset 1 mm to the DS side

— minimum 3 scans of the calibration block with the bandoffset 1 mm to the US side

— minimum 3 scans of the calibration block with the bandremoved and reset between each scan. The calibrationblock shall be in the least favourable position as deter-mined in 2 and 3 above.

706 All scans shall be given a unique number and the docu-mentation of the test scans shall include:

— hard copy and electronic output of all scans— a table for repeatability test scans showing for each scan

the maximum amplitude response of each transducer to itsdedicated calibration reflector and the deviation for eachscan from the initial calibration scan.

Temperature sensitivity testing 707 Typical test welds containing at least 6 clearly identifia-ble and distinct AUT indications each shall be used for scan-ning with the pipe axis in the horizontal position. The test welds shall after the initial scans be heated to the ele-vated temperature expected during field work and maintainedat this temperature during scanning. The calibration block(s)shall be kept at environmental temperature or be heated to anagreed temperature and maintained at this temperature duringscanning.The testing shall include:

— one initial scan of the calibration block— one initial scan of the non-heated weld— one scan of the heated test weld immediately followed by

a scan of the calibration block(s)— repeat with 5 minutes intervals several scans of the heated

test weld each immediately followed by a scan of the cal-ibration block(s).

If the AUT system shows unacceptable temperature sensitivitythe test can be repeated with agreed different test conditions.708 All scans shall be given a unique number and the docu-mentation of the test scans shall include:

— hard copy and electronic output of all scans— a table for the temperature sensitivity test scans showing

the maximum amplitude response for each identified indi-cation for each scan.

Detection ability and sizing accuracy testing709 The test welds shall normally be scanned with the pipeaxis horizontal. If the AUT system shall be qualified for scan-ning with the pipe axis vertical, the testing shall be performedin this position only or in both positions. The scanning directions identified as clockwise or counterclockwise (CW or CCW) shall be hard stamped on the testweld. The calibration block shall be in the least favourableposition as determined by the repeatability testing. See H705.The testing shall include:

— one initial scan of the calibration block

— minimum 2 scans of the test weld in the CW direction withre-setting of the band between each scan

— one scan of the calibration block(s)— minimum 2 scans of the test weld in the CCW direction

with resetting of the band between each scan— one scan of the calibration block(s)— assessment and sizing of indications.

710 All scans shall be given a unique number indicatingweld number, the scan sequence and the scanning directionand the documentation of the test scans shall include:

a) hard copy and electronic output of all scansb) defect/indication number with reference to sizing method

and for each defect/indication the dimensions:

— circumferential position— length— height — depth to bottom of indication— transverse location of defects/indications (US, DS,

C(entral))— maximum amplitude for each scan and variations in

maximum amplitude between scans— main AUT zone— defect type.

It may further be required to report height, location, depth andecho amplitude at certain additional local defect positions (seealso H603).In addition the following information shall be provided:

— weld identification— pipe material— pipe thickness/diameter— welding method— groove geometry— calibration block documentation.

Verification of coupling alarm settings711 Scans shall be performed on different test welds. Thecouplant flow shall be reduced and the surface wiped drybetween scans until the coupling alarm level/coupling monitorchannels indicates loss of return signal. The level at which thecoupling alarm/ coupling monitor channels indicates loss ofreturn signal shall be recorded. The final level for couplingalarm /coupling monitor channels settings shall be at least 4 dBlower than the recorded value.

H 800 Reference destructive testing801 The reports from the AUT qualification testing shall bevalidated for accuracy in the determination of defect circum-ferential position, length, height and depth by referencedestructive testing.802 The testing shall be by cross-sectioning, preferably bythe "salami method", by making more cross-sections aroundeach location chosen. The defects as reported in the AUTreports shall be used when selecting the areas for cross section-ing. In addition, locations where the AUT shows indications nearthe threshold level, locations where indications are identifiedby the supplementary NDT (see H605), locations where inten-tionally induced defects was planned and randomly chosenlocations shall be included. Alternatives to macro sectioning such as C-scan immersiontesting of the girth weld may be acceptable. However, anyother methods other than macro sectioning need to be sepa-rately qualified to establish the degree of accuracy.803 The cross sections shall be referenced to and validatedagainst the recording chart positions.

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804 The weld sections containing defects shall be machinedin increments of maximum 2.0 mm. Each machined cross sec-tion of the weld shall be polished with 600 grit and etched andthe defect location, height and depth measured with accuracybetter than ± 0.1 mm. Each cross section shall be documentedby a photograph with 5 - 10x magnification.805 The extent of sectioning shall be sufficient to ensure thatthe defect height/length sizing analysis will be based on a suf-ficient number of different defects and/or ultrasonically inde-pendent parts of defects (i.e. at locations many beam widthsapart). Indications with small and large heights shall beincluded.

H 900 AnalysisRepeatability 901 The data from the repeatability test programme shall beanalysed with respect to system repeatability and stability. Themaximum deviations in amplitude from each reference reflec-tor between the initial scan and:

— the scans performed with each calibration block position— the scans performed with the band offset— the scans performed with removal and resetting of the

band.

shall be determined. Temperature sensitivity 902 The data from the temperature sensitivity test pro-gramme shall be analysed with respect to the influence of tem-perature build-up in the transducers over time. The maximumvariations in amplitude from each selected indication betweenthe initial scan and the scans performed with heated test weldand with or without or heated calibration blocks shall be deter-mined.Based upon an acceptable variation in amplitude of ± 2 dB, theanalysis shall determine the:

— acceptable maximum temperature of welds— the sum of transducer inactive time on weld and scanning

time— the minimum time between scanning of hot welds— the maximum temperature difference between weld and

calibration block.

Detection ability and sizing accuracy 903 The data recorded during the tests and reference investi-gations shall be analysed with respect to:

— accuracy in height sizing (random and systematic devia-tion, and 5% fractile)

— accuracy in length sizing— accuracy in circumferential positioning / location— AUT defect characterisation abilities compared to the

results of the destructive tests and the other NDT per-formed

— as relevant, determination of PoD/PoR values or curvesfor different assumed echo amplitude or other employedthreshold settings to determine the threshold to be usedduring examination.

904 The analysis shall be performed by recognised andapplicable statistical methods, e.g. according to Nordtest NTTechn. Report 394 (Guidelines for NDE Reliability Determi-nation and Description, Approved 1998-04). The omission ofany reported indication in the analysis shall be justified.

H 1000 Reporting1001 A qualification report shall as a minimum contain:

— a technical documentation of the AUT system— outcome of the technical evaluation of the AUT system

according to this Appendix— description of the specimens and tests performed, includ-

ing sensitivities used— definitions of the essential variables (see I200) for the

welds and equipment used during qualification testing— data recorded for each defect and each defect cross-section

(sizes, locations, types, measured and determined duringreference investigation, echo amplitudes)

— outcome of the analysis of data (H900)— conclusion of the qualification.

I. Validity of QualificationI 100 Validity101 A qualification is AUT system, weld method and groovegeometry specific.A qualification of an AUT system will remain valid on the con-dition that no changes are made in the essential variablesdefined in I200 that would influence on AUT performance.

I 200 Essential variables201 The following essential variables apply:

— welding method and groove geometry (including repairwelds, if relevant)

— root and cap transducer set-up— transducer set-up for other channels (the number of these

channels may be increased or decreased to accommodatechanges in wall thickness provided there are no set-upchanges)

— focal laws— reference reflectors— working temperature range— system, data acquisition and data treatment— software version (except changes affecting viewing, dis-

play or bug-fixing only).

202 Changes in the essential variables for an existing quali-fied system will require a demonstration of the ability of thenew or modified system to detect and accurately size and posi-tion weld imperfections.

J. Determination of Wave Velocities in Pipe Steels

J 100 GeneralThe procedure defined covers methods that may be used todetermine acoustic velocity of ultrasonic waves in linepipesteels. Equivalent methods may be used subject to agreement.Linepipe used in oil and natural gas transmission exhibit vary-ing degrees of anisotropy with varying acoustic velocitiesdepending on the propagation direction with resultant changesin the refracted angle of the sound in the steel. This is espe-cially critical where focused beams are used for zonal discrim-ination. It is thus required to determine the ultrasonic shear orlongitudinal (as appropriate) wave velocity for propagation indifferent directions.

J 200 EquipmentTo determine the wave velocity (shear or compression) direc-tional dependency an ultrasonic wave transducer of the samefrequency used in the inspection with a crystal diameter of 6 -10 mm should be used in combination with an ultrasonic appa-ratus with bandwidth at least up to 10 MHz and a recom-mended capability of measuring ultrasonic pulse transit timeswith a resolution of 10 ns and an accuracy of ± 25 ns. Devicesfor measuring mechanical dimension of the specimens should

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have a recommended accuracy of ± 0.1 mm. As couplant aneasily removable glue or special high viscosity shear or com-pression wave couplant (as appropriate) is recommended.

J 300 SpecimensA specimen is cut from a section of pipe to be tested and thecorresponding results are specific for a particular pipe diame-ter, wall thickness and manufacturer. Specimen dimensionsshould be a minimum of 50 × 50 mm.A similar arrangement can also be used for measuring veloci-ties in a plane normal to pipe axis.

Figure 1 Test specimen and transducer placement

A minimum of three parallel surfaces are machined for the

plane to be evaluated; one pair of surfaces is made in the radialdirection (perpendicular to the OD surface) and the other pairmade 20° from the perpendicular to the OD surface, seeFigure 1. Additional pairs of parallel surfaces may bemachined at other angles in the plane to be evaluated if moredata points are desired.The machined surfaces should be smooth to a 20 μm finish orbetter. Minimum width of the specimen surface to be measuredshould be 20 mm and the minimum thickness between the par-allel surfaces to be measured should be 10 mm. Vertical extentof the test surface will be limited by the pipe wall thickness.

J 400 Test methodUsing the machined slots as reflectors for the wave pulses withthe transducer in the appropriate positions and measuring thepulse transit times determines together with the mechanicallymeasured pulse travelling distances the wave velocities in theaxial and 20° direction (Figure 1).A similar measurement in the through thickness directiondetermines the radial velocity. Pulse transit times shall bemeasured between the forefront parts of 1st and 2nd back wallecho, or, alternatively, using more multiple echoes.A minimum of three readings shall be made for each plane inwhich testing shall be done.

J 500 AccuracyErrors in velocity determination shall not be greater than± 20 m/s.

J 600 RecordingValues for the velocities determined can be tabulated andgraphed. By plotting velocities on a two dimensional polargraph for a single plane, velocities at angles other than thosemade directly can be estimated.The effect of temperature on velocity can be significant underextreme test conditions; therefore the temperature at whichthese readings have been made should also be recorded.

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Offshore Standard DNV-OS-F101, October 2007 App.F –

APPENDIX F REQUIREMENTS FOR SHORE APPROACH

AND ONSHORE SECTIONS

A. ApplicationA 100 Objective101 The objective of this appendix is to provide the comple-mentary requirements to the onshore part of the submarinepipeline system compliant with the safety philosophy for theoffshore part. This appendix specifies the requirements fordesign, construction and operation of parts of pipeline systemsgoing onshore. This appendix is meant to ease the project execution of subma-rine pipeline developments where parts are going onshore.

Guidance note:A submarine pipeline system is defined to end at weld beyond thefirst flange/valve onshore or to the pigging terminal. This impliesthat a, sometimes significant, part of the pipeline system can belocated onshore. This part of the pipeline system may have dif-ferent legislations, failure modes and failure consequences com-pared to the submarine part. The exact limit of the submarine pipeline system at the onshoreend may differ from this definition herein based on different stat-utory regulations which may govern.Onshore codes may also take precedence of this part due to leg-islation aspects.


102 The appendix also covers requirements to shoreapproach.

A 200 Scope and limitation201 The limitations found in Sec.1 A300 are in general alsoapplicable for this Appendix. 202 The onshore section is limited by the definition of sub-marine pipeline system.

203 This appendix does not cover regular onshore pipelines,i.e. pipelines starting and ending onshore not having any sub-marine parts. River crossings or crossing of fresh water lakesare not considered as submarine sections.

Guidance note:This appendix is not meant to replace current industry practiceonshore codes or any national requirements.


204 Specific requirements for the onshore parts given in thisappendix overrule requirements given elsewhere in the stand-ard.

A 300 Other codes 301 This Appendix is fully aligned with the requirementsgiven in ISO 13623

Guidance note:ISO 13623 requires a specific utilisation for landfall. Accordingto this code the assessment of risk will constitute selection ofsafety class for each specific pipeline and pipeline sections. Nor-mally the safety class classification for a landfall will give thesame utilisation as required by ISO 13623 however this does notalways need to be the case. This implies that the utilisation inlandfall may differ from the ISO 13623 requirements and careshould be taken when stating compliance with ISO 13623 for aspecific pipeline development.


302 Onshore pipelines are normally regulated by nationalregulations and cover a wide range of areas from public safety,traffic and roads, water ways, environmental impact, etc. Someof these regulations may be stricter than the requirementsgiven in this code and care shall be exercised when assuringcompliance with different national regulations.

Figure 1 Maximum application extent of OS-F101 with Appendix F.

A 400 Definitions401 Battery limit - the limit at which the scope of work ends.The battery limit can be different for designer, installation con-tractor, verifier and owners. Normally defined at as ‘including’or ‘up to’ a certain weld.402 Code break - the exact point at which the design codechanged from submarine to onshore code. Normally defined atas ‘including’ or ‘up to’ a certain weld. This is often defined at

the location of the first flange or valve onshore. Note that thismay differ based on different statutory regulations. 403 First (or last) valve onshore - valve separating the off-shore and onshore pipeline. Often the position of the batterylimit and the code break. Often an emergency shut downvalves (ESDV)404 Isolation joint - a special component separating (isolat-ing) the offshore cathodic protection from the onshorecathodic protection system and installed within the onshorepart of the offshore pipeline. It is normally positioned veryclose to the landfall as the offshore cathodic protecting system

Offshore section

Nearshore section Shore approach

Onshore section

Isol

atio

n jo

int

Firs

t (or

last

) va

lve

Application of OS-F101 withAppendix F

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Offshore Standard DNV-OS-F101, October 2007 – App.F

has limited protection capabilities when the pipeline is not sub-merged in water.405 Landfall - where the pipeline comes on shore. Oftendefined by a point called LTE; Land Terminal End. 406 Near shore - the transition from the offshore pipeline tothe shore approach area. Often not well defined, but can be thearea in where the pipeline goes from laying on the sea-bed tobeing positioned in an open trench to where it is buried. Some-times the extent of the areas is defined by the reach of theinstallation vessel or trenching equipment, and sometimes thisarea is given special attention by the fishing industry. 407 Onshore part of offshore pipeline - the first part of thepipeline on shore. It is distinct as the offshore design code isstill applied, while the pipeline is not offshore. The length isnormally short, up to some kilometres.408 Onshore pipeline - the pipeline on shore followingonshore codes and normally subject to different authority reg-ulations 409 Right-of-way – corridor of land within which the pipe-line operator has the right to conduct activities in accordancewith the agreement with the land owner.410 Shore approach - the last part of the pipeline before itcomes on shore. The need for burying the pipeline in the shoreapproach area should be evaluated and include:

— environmental loading (breaking waves, current and tide), — requirements to a ‘clean beach’ for recreation, — shipping activity or — protection (reduced access by 3rd parties).

B. Safety PhilosophyB 100 General101 The design philosophy for the shore approach and theonshore pipeline shall comply with Sec.2. This implies that theconsequences of failure (economical, environmental andhuman) shall be quantified by the concept of safety class. Thesafety class is normally determined by fluid category, locationclass and phase (construction, operation) of the pipeline. 102 The presence of people and facilities necessitates a fur-ther refinement of the location classes used offshore. In highlypopulated areas the consequences may be more severe than foroffshore, requiring a higher safety class, Very High. These complementary issues are described in this sub-section.

Guidance note:It should be noted that ISO 13623 contain even more stringentutilisation requirements than safety class Very High. However,as this code is meant to only cover onshore parts of an offshorepipeline system it is not foreseen that such a line will be locatedin areas with even higher population densities.


B 200 Safety philosophy201 The safety philosophy outlined in Sec.2 B is applicablefor shore approach and onshore sections.

Guidance note:In particular is it important to perform a systematic review of allhazards to identify consequences as third party presence is moresignificant onshore.


202 The quality assurance outlined in Sec.2 B is applicablefor shore approach and onshore sections.203 The health, safety and environmental aspects outlined inSec.2 B is applicable for shore approach and onshore sectionsalso.

B 300 Quantification of consequence 301 Fluids shall be categorised in line with Sec.2 of thisstandard.302 A location class shall be determined for each part of thepipeline as shown in Table F-1.

303 The population density in Table F-1, expressed as thenumber of persons per square kilometre, shall be determinedby laying out zones along the pipeline route, with the pipelinein the centreline of this zone having a width of:

— 400 m for category D fluids, and— to be determined for category E fluid pipelines, but not

less than 400 m. The determination shall include the pos-sibility of very low temperature during a leakage of highpressure pipelines, giving high density gas that may“float” significant distance prior to ignition.

304 Half the zone width shall not be less than the effectivedistance of fluid release.305 The length of the zones shall be 1.5 km and located atany location along the pipeline. The length of the random sec-tions may be reduced where physical barriers or other factorsexist, which will limit the extension of the more densely pop-ulated area to a distance less than 1.5 km.306 The possible increase in population density and level ofhuman activity from planned future developments shall bedetermined and accounted for when determining populationdensity.307 Additional considerations shall be given to the possibleconsequences of a failure near a concentration of people suchas found in a church, school, multiple-dwelling unit, hospital,or recreational area of an organised character in locationclasses 2 and 3.308 Pipeline design according to this standard is based onpotential failure consequence and is quantified by the concept

Table F-1 Location Classes OnshoreLocation Class Description1 (Equivalent to Location class 1 as defined in Sec.2)

Locations subject to infrequent human activity with no permanent human habitation. Location Class 1 is intended to reflect inaccessible areas such as deserts and tundra regions

2 Locations with a population density of less than 50 persons per square kilometre. Location Class 2 is intended to reflect such areas as wasteland, grazing land, farmland and other sparsely popu-lated areas

3 (Equivalent to Location class 2 as defined in Sec-tion 2)

Locations with a population density of 50 per-sons or more but less than 250 persons per square kilometre, with multiple dwelling units, with hotels or office buildings where no more than 50 persons may gather regularly and with occasional industrial buildings. Locations Class 3 is intended to reflect areas where the popula-tion density is intermediate between location Class 2 and Location Class 4, such as fringe areas around cities and towns, and ranches and country estates.

4 Locations with a population density of 250 per-sons or more per square kilometre, except where a Location Class 5 prevails. A Locations Class 4 is intended to reflect areas such as suburban housing developments, residential areas, indus-trial areas and other populated areas not meeting Location Class 5.

5 Location with areas where multi-storey build-ings (four or more floors above ground level) are prevalent and where traffic is heavy or dense and where there may be numerous other utilities underground.

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of safety class. These may vary for different phases and loca-tions and are defined in Table F-2.

309 The acceptable failure probability of safety class VeryHigh is one order of magnitude lower than for safety classHigh as given in Sec.2 of this standard.310 The safety class determined by the crossing shall applyfrom:

— for road crossings— the road right-of-way boundary— if this boundary has not been defined, to 10 m from the edge

of the hard surface of major roads and 5 m for minor roads— for railways— 5 m beyond the railway boundary or— if this boundary has not been defined, to 10 m from the

rail.

311 The safety class can often be determined based on thelocation class and fluid category. Typical selection of safetyclass is given in Table F-3.

1) Installation until commissioning (temporary) will normally be classifiedas safety Class low. During temporary conditions after commissioning ofthe pipeline, special considerations shall be made to the consequences offailure, i.e. giving a higher safety class than Low.

2) This code is not applicable for areas in location Class 5.

C. Design PremiseC 100 General101 The basis for design premises for the shore approachshall be as given in Sec.3. Special attention shall be given toaspects related to installation, on-bottom stability, fatigue dueto direct wave loading and 3rd party activities. Statutoryrequirements apply.102 The shore approach should be constructed by either

— a tunnel, — horizontal directional drilled (HDD) guide tube,— cofferdam, — trench, — dredging, or — combinations of the above.

C 200 Routing201 The requirements in Sec.3 C apply to the shore approachsection. Additional requirements are given below.202 The routing shall be selected and prepared so that risk offire, explosions and un-intended occurrences is at an accepta-ble level. Spacing between pipelines, associated equipment,harbours, ship traffic and buildings shall be evaluated by riskassessments considering the service of the pipeline.

Guidance note:The preferred means of routing for shore approach pipeline willbe to bury them. Examples of additional protective means areConcrete coating or cover, additional steel wall thickness, deepertrenching, additional marking and means to minimize the possi-bility for impacts from ship traffic and vehicles.


203 Special focus shall be on:

— safety of public— protection of environment— 3rd party activities— access— other property and facilities.

204 Pipeline conveying category B, C, D and E fluids shouldavoid built-up areas or areas with frequent human activity.205 In absence of public safety statutory requirements, asafety evaluation shall be performed in accordance with thegeneral requirements for:

— Pipeline conveying category D fluids in locations wheremulti-storey buildings are prevalent, where traffic is heavyor dense, and where there may be numerous other utilitiesunderground

— Pipelines conveying category E fluids.

206 An Environmental Impact Assessment (EIA) shall beperformed. The EIA shall consider as a minimum:

— temporary works during construction and operation (e.g.repair, modifications etc.)

— the long-term presence of the pipeline— leakage.

207 The route shall permit the required access and workingwidth for the construction and operation (including anyreplacement), of the pipeline. The availability of utilities nec-essary for construction and operation should also be reviewed.208 The route shall be tidy and free from flammable materialson and in the vicinity of the pipeline system. A safety area alongthe pipeline shall be defined which may restrict public accessand activities. The extent of the area shall be established basedon risk analyses and shown on the plan for the pipeline system.209 Facilities along the pipeline route should be identifiedand their impact evaluated in consultation with the operator ofthese facilities. Facilities should not be allowed closer than 4m from the pipeline.210 A wider restriction zone compared to public access mayapply to future development (buildings etc.).

C 300 Environmental data301 Environmental data shall be collected as described inSec.3. Long term shore profile shall be considered. Specialattention shall be given to tidal variations.

C 400 Survey401 Route and soil surveys shall be carried out to identifyand locate with sufficient accuracy the relevant geographical,geological, geotechnical, corrosive, topographical and envi-ronmental features, and other facilities such as other pipelines,

Table F-2 Definition of safety classesSafety Class DescriptionLow Where failure implies low risk of human

injury and minor environmental and eco-nomic consequences

Medium Where failure implies risk of human injury, significant environmental pollution or very high economic or political consequences

High Where failure during operating conditions implies high risk of human injury, significant environmental pollution or very high eco-nomic or political consequences

Very High Where failure during operating conditions implies very high risk of human injury.

Table F-3 Classification of safety classesPhase Fluid

CategoryLocation Class

1 2 3 4 52

Temporary1 All Low - Operating Onshore

A,C Low Medium -B Medium Medium High Very

High-

D,E Medium Medium High Very High

-

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cables and obstructions, which may impact the pipeline routeselection. The surveys shall be continuous, and the accuracyand tolerance should be selected with regard to the adjoiningland and offshore surveys.402 Inshore survey coverage should be continuous and inagreement within specified tolerances and accuracies of bothadjoining land and offshore route surveys.

C 500 Marking501 The pipeline system shall be marked in such a way thatits location in the terrain is clearly visible. Provisions shall bemade to restrict public access to pipelines that are not buried.502 Warning signs shall be placed within visible distanceand at each side of crossings with rivers, roads and rail waysgiving information on:

— content— owner— phone number to nearest manned station which may be

alerted in the event of fault on the pipeline.

D. Design

D 100 General101 The pigging requirements in Sec.5 B114 and B115applies to the pipeline system.

D 200 System design201 Any electrical equipment within the location class areasshall comply with the location class requirements.202 The need for lightening rod and means to avoid build upof static electricity shall be considered.203 Branch connections for pipelines on land shall be supportedby consolidated backfill or provided with adequate flexibility. 204 Braces and damping devices required to prevent vibration ofpiping shall be attached to the pipe by full encirclement members.205 Structural items should not be welded directly to pres-sure containing parts or linepipe due to the increased localstress on the linepipe. External supports, attachments etc. shallbe welded to a doubler plate or ring. The double plate or ringshall be designed with sufficient thickness to avoid stresses onthe linepipe. In case structural items are integrated in the pipe-line, e.g. pipe in pipe bulkheads, and are welded directly to thelinepipe, detailed stress analyses are required in order to docu-ment sufficiently low stress to ensure resistance againstfatigue, fracture and yielding.

D 300 Design loads301 The loads shall be established as described in Sec.4.Special attention shall be given calculations of loads from 3rdparty activities such as traffic (potential cyclic loading) andother construction work.302 The loads shall be classified into functional, environ-mental, interference or accidental loads as per Sec.4 of thisstandard with the additional requirements below.303 Traffic axle loads and frequency shall be established inconsultation with the appropriate authorities or other relevantsources and with recognition of existing and forecast residen-tial, commercial and industrial developments.

D 400 Design criteria401 The design should comply with the requirements in Sec.5.Special attention shall be given to statutory requirements.402 For safety class Very High the safety class factors in

Table F-4 apply.

403 Buried pipelines on land should be installed with a coverdepth not less than shown in Table F-5.

1) Cover depth shall be measured from the lowest possible ground surfacelevel to the top of the pipe, including coatings and attachments.

2) Special consideration for cover may be required in areas with frost heave.3) River crossings, road crossings and railway crossing shall in this context

be classified as safety class High.4) Cover shall not be less than the depth of normal cultivation +0.3 m.5) For river crossings; to be measured from the lowest anticipated bed.6) For roads and railway crossings; to be measured from the bottom of the

drain ditches7) The top of pipe shall be at least 0.15 m below the surface of the rock.

404 The effect of cover depth shall be considered in theexpansion evaluations. 405 If the pipeline is not laid at a frost free depth, the massbelow the pipe’s centre line must be frost proof.406 Pipelines may be installed with less cover depth thanindicated in Table F-5, provided a similar level of protection isprovided by alternative methods. The design of alternative pro-tection methods should take into account:

— any hindrance caused to other users of the area— soil stability and settlement— pipe stability cathodic protection— pipeline expansion— access for maintenance.

407 Pipelines running parallel to a road or railway should berouted outside the corresponding right-of-way.408 The vertical separation between the top of the pipe andthe top of the rail should be a minimum of 1.4 m for open-cutcrossings and 1.8 m for bored or tunnelled crossings.409 Protection requirements for pipeline crossings of canals,rivers and lakes should be designed in consultation with localwater and waterways authorities.410 Crossings of flood defences can require additionaldesign measures for prevention of flooding and limiting thepossible consequences.411 Crossing pipelines and cables should be kept separatedby a minimum vertical distance of 0.3 m.412 Pipeline bridges may be considered when buried cross-ings are not practicable. Pipe bridges shall be designed inaccordance with structural design standards, with sufficientclearance to avoid possible damage from the movement of traf-fic, and with access for maintenance. Interference between thecathodic protection of the pipelines and the supporting bridgestructure shall be considered. 413 Provisions shall be made to restrict public access to pipebridges.

Table F-4 Partial safety class resistance factor for safety class Very HighLimit state γSCPressure containment 1.593Other limit states 1.5

Table F-5 Minimum cover depth for buried pipelines on land (alternative, preferred formulation to the table above)Safety Class 3) Cover depth [m] 1) 2) 4) 5) 6) 7)

Trench blasted in rock OtherLow 0.5 0.8Medium 0.8High 1.2Very High 1.2

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414 If other criteria are used, the nominal failure probabili-ties shall be demonstrated to be as specified in Sec.2.

E. ConstructionE 100 General101 The same requirements as for the Offshore part of thepipeline system shall be applied to the onshore part, if applica-ble. Where this is not applicable, the requirements ofISO 13623 should be complied with.

Guidance note:This is applicable for e.g. welding and NDT in Appendixes C, Dand E


E 200 Linepipe201 The manufacture of linepipe should comply with therequirements in Sec.6.

E 300 Components and assemblies301 The requirements to components and structural items aswell as assemblies should comply with Sec.7.

E 400 Corrosion protection & coatings401 The corrosion protection shall comply with Sec.8.402 All metal pipelines should be provided with an externalcoating and, for buried or submerged sections, cathodic protec-tion. Corrosion protection should normally be provided byimpressed current.403 The design of the impressed current protection systemshall strive for a uniform current distribution along the pipe-lines and shall define the permanent location for the measure-ment of the protection potentials. 404 Protected pipelines should be electrically isolated fromother structures, such as compressor stations and terminals, bysuitable in-line isolation components.405 Isolation joints should be provided with protectivedevices to prevent damage from lightning or high-voltageearth current where possible. Low-resistance grounding toother buried metallic structures shall be avoided. Electricalcontinuity shall be provided across components, other thancouplings/flanges, which would otherwise increase the longi-tudinal resistance of the pipeline. Spark gaps shall be installedbetween protected pipelines and lightning protection systems.

406 Test points for the routine monitoring and testing of thecathodic protection should be installed at the following loca-tions:

— crossings with DC tractions systems— road, rail and river crossings and large embankments — sections installed in sleeve pipes or casings— isolated couplings— where the pipeline runs parallel to high-voltage cables— sheet piles— crossings with other major metallic structures with, or

without, cathodic protection.

407 The primary corrosion control for internal corrosion isidentical with the submarine part, see Sec.8.

F. OperationF 100 General101 The requirements to safe and reliable operation of thepipeline systems and the pipeline integrity management (PIM)as described in Sec.10 apply.102 The whole route shall regularly be checked for:

— any required re-classification of location class due tochanges in premises like populations etc.

— new facilities— new intruders or changed configurations that may cause

increase risk of threats.

G. DocumentationG 100 General101 In addition to the requirements in Sec.11, the followingapply:

— crossing locations related to lakes, straits, rivers, streams,transport communication arteries and similar

— maps necessary to evaluate the proposed route classifica-tion

— relevant drawings on bridges etc.— maps with any crossing services (cables, sewage etc.).

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