Norsok M101 Structural Steel Fabrication

NORSOK STANDARD

STRUCTURAL STEEL FABRICATION

M-101

Rev.4. Dec. 2000

This NORSOK standard is developed by NTS with broad industry participation. Please note that

whilst every effort has been made to ensure the accuracy of this standard, neither OLF nor TBL or

any of their members will assume liability for any use thereof. NTS is responsible for the

administration and publication of this standard.

Norwegian Technology Center

Oscarsgt. 20, Postbox 7072 Majorstua

N-0306 Oslo, NORWAY

Telephone: + 47 22 59 01 00 Fax: + 47 22 59 01 29

Email: [email protected] Website: http://www.nts.no/norsok

Copyrights reserved

Structural steel fabrication M-101

Rev. 4, Dec. 2000

NORSOK standard Page 1 of 36

CONTENTS

FOREWORD 3

INTRODUCTION 3

1 SCOPE 4

2 NORMATIVE REFERENCES 4

3 DEFINITIONS AND ABBREVIATIONS 5

3.1 Definitions 5

3.2 Abbreviations 5

4 SELECTION OF STEELS 6

4.1 Design classes 6

4.2 Selection of steel quality level 6

5 QUALIFICATION OF WELDING PROCEDURES AND WELDERS 6

5.1 Welding procedure specification (WPS) 6

5.2 Qualification of welding procedures 6

5.3 Welding procedure approval record (WPAR) - Range of approval 7

5.4 Examination of the test weld 8

5.5 Welder and welding operators qualifications 11

6 FABRICATION AND WELDING REQUIREMENTS 11

6.1 General 11

6.2 Forming 11

6.3 Assembly 12

6.4 Preparation for coatings 13

6.5 Preparation and fit-up of weld bevels 13

6.6 Welding processes 13

6.7 Welding consumables 14

6.8 Preheat and interpass temperature 14

6.9 Production welding 15

6.10 Post weld heat treatment (PWHT) 16

6.11 Grinding 16

6.12 Peening 16

7 PRODUCTION TESTS 17

8 FABRICATION TOLERANCES 17

9 NON-DESTRUCTIVE TESTING (NDT) 17

9.1 General 17

9.2 Qualification of inspectors and NDT-operators 18

9.3 Extent of visual examination and NDT 19

9.4 Visual examination and finish of welds 21

9.5 Radiographic testing 21

9.6 Ultrasonic testing 21

9.7 Magnetic particle and Penetrant testing 22

9.8 Acceptance criteria 22

10 REPAIR 28


Rev. 4, Dec. 2000


10.1 Definitions 28

10.2 Correction of welds containing defects 28

10.3 Repair by welding 28

10.4 Repair welding procedure 29

10.5 Correction of distortion 29

ANNEX A 1 - TYPICAL GRINDING DETAILS FOR HIGH FATIGUE UTILISATION

(INFORMATIVE) 30

ANNEX A 2 - TYPICAL PEENING DETAILS FOR HIGH FATIGUE UTILISATION

(INFORMATIVE) 31

ANNEX B - CORRELATION BETWEEN STEEL QUALITY LEVEL, MDS NUMBER AND

STEEL GRADE/DESIGNATIONS (NORMATIVE) 33

ANNEX C - QUALIFICATION OF WELDING CONSUMABLES BY DATA SHEETS

(NORMATIVE) 34

ANNEX D - WELDING CONSUMABLE DOCUMENTED BY BATCH TESTING

(NORMATIVE) 36

ANNEX E FABRICATION TOLERANCES (NORMATIVE) 37


Rev. 4, Dec. 2000


FOREWORD

NORSOK (The competitive standing of the Norwegian offshore sector) is the industry initiative to

add value, reduce cost and lead time and eliminate unnecessary activities in offshore field

developments and operations.

The NORSOK standards are developed by the Norwegian petroleum industry as a part of the

NORSOK initiative and supported by OLF (The Norwegian Oil Industry Association) and TBL

(Federation of Norwegian Manufacturing Industries). NORSOK standards are administered and

issued by NTS (Norwegian Technology Center).

The purpose of NORSOK standards is to contribute to meet the NORSOK goals, e.g. to develop

standards that ensure adequate safety, value adding and cost effectiveness and thus are used in

existing and future petroleum industry developments.

The NORSOK standards make extensive references to international standards. Where relevant, the

contents of a NORSOK standard will be used to provide input to the international standardisation

process. Subject to implementation into international standards, the NORSOK standard will be

withdrawn.

Annex A is informative. Annexes B, C, D and E are normative.

INTRODUCTION

Revision 4 of this standard has been necessary due to regulations in new design standard N 004 and

new designation of steel grades. In addition a steel grade with SMYS 690 is introduced with

additional requirements to fabrication.


Rev. 4, Dec. 2000


1 SCOPE

This standard covers the requirements for fabrication and inspection of offshore steel structures with

SMYS < 500 MPa and with a minimum design temperature down to -14°C. For special application

steels with SMYS up to 690 MPa may be used.

Note: For highly fatigue utilized structures, more severe requirements may apply, and these will be

shown on the design drawings.

2 NORMATIVE REFERENCES

The following standards include provisions which, through reference in this text, constitute

provisions of this NORSOK standard. Latest issue of the references shall be used unless otherwise

agreed. Other recognized standards may be used provided it can be shown that they meet or exceed

the requirements of the standards referenced below.

API 2B Specification for fabricated structural steel pipe.

API RP 2X Ultrasonic examination of offshore structural fabrications.

ASME, Section V Non-destructive testing.

BS 7448, Part 1 Fracture mechanics toughness tests.

BS 7910 Guide on methods for assessing the acceptability of flaws in fusion

welded structures.

DNV RP D404 Unstable fracture.

EN 287-1 Approval testing of welders - Fusion welding.

EN 288-series Specification and qualification of welding procedures for metallic

materials.

EN 444 NDT - General principles for radiographic examination of metallic

materials by X-rays and gamma rays.

EN 462-series NDT - Image quality of radiographs.

EN 473 Qualification and certification of NDT personnel - General principles.

EN 719 Welding coordination - Tasks and responsibilities.

EN 729-series Quality requirements for welding - Fusion welding of metallic materials.

EN 875 Welding - Welded joints in metallic materials - Specimen location and

notch orientation for impact tests.

EN 970 Welding - Visual examination of fusion welded joints.

EN 1011-series Welding - Recommendation for welding of metallic materials, relevant

parts.

EN 1289 Non destructive examination of welds - Penetrant testing of welds -

Acceptance levels.

EN 1290 NDT of welds - Magnetic particle examination of welds - .


Rev. 4, Dec. 2000


EN 1291 NDT of welds - Magnetic particle examination of welds - Acceptance

levels.

EN 1418 Welding personnel - Approval testing for fully mechanised and automatic

welding.

EN 1435 Non destructive examination of welds - Radiographic examination of

welded joints.

EN 1597-1 Welding consumables - Test methods - Part 1: Test piece for all weld

metal test specimens in steel, nickel and nickel alloys.

EN 1714 Non destructive examination of welds - Ultrasonic examination of

welded joints.

EN 10204 Metallic products - Types of inspection documents.

prEN 10225 Weldable structural steels for fixed offshore structures.

EN 26847 Covered electrodes for manual metal arc welding.

Deposition of a weld pad for chemical analysis.

ISO 3690 Welding - Determination of hydrogen indeposited weld metal arising

from the use of covered electrodes for welding mild and low alloy steels.

ISO 5817 (=EN 25817) Arc welded joints in steel - Guidance on quality levels for imperfections.

NORSOK M-001 Material selection

NORSOK M-120 Material data sheets for structural steel

NORSOK N-001 Structural design

NORSOK N-004 Design of steel structures

NS 477 Welding. Rules for approval of welding inspectors.

3 DEFINITIONS AND ABBREVIATIONS

3.1 Definitions

Normative references Shall mean normative in the application of NORSOK standards.

Informative references Shall mean informative in the application of NORSOK standards.

Shall Shall is an absolute requirement which shall be followed strictly in order

to conform with the standard.

Should Should is a recommendation. Alternative solutions having the same

functionality and quality are acceptable.

May May indicates a course of action that is permissible within the limits of

the standard (a permission).

Can Can is conditional and indicates a possibility open to the user of the

standard.

3.2 Abbreviations

AWS American Welding Society

BS British Standard

CE Carbon Equivalent equation

CTOD Crack Tip Opening Displacement

DAC Distance Amplitude Curve

DC Design Class

DIN Deutsche Institut für Normung


Rev. 4, Dec. 2000


DNV Det Norske Veritas

EN (pr EN) European Standard (proposal for EN)

FCAW Flux Cored Arc Welding

FSH Full Screen Height

HAZ Heat Affected Zone

HDM Hydrogen content, deposit metal

IIW International Institute of Welding

ISO International Organization for Standardization

NDT Non Destructive Testing

MDS Material Data Sheet

MSF Module Support Frame

Pcm Carbon equivalent (Parameter for crack, modified)

PWHT Post Weld Heat Treatment

SAW Submerged Arc Welding

SMYS Specified Minimum Yield Strength

SQL Steel Quality Level

WPS Welding Procedure Specification

WPAR Welding Procedure Approval Record

4 SELECTION OF STEELS

4.1 Design classes

The design classes will be decided by the designer and shall form the basis for selection of steel

quality level (SQL). Reference is made to NORSOK standard N-004.

4.2 Selection of steel quality level

The steel quality level will be decided by the designer in compliance with N-004.

Annex B gives the correlation between the steel quality levels I, II, III and IV, and designations on

equivalent steels given in NORSOK standard M-120, Material data sheets.

Selection of a better steel quality level in fabrication than the minimum required by the designer

shall not lead to more stringent requirements in fabrication.

5 QUALIFICATION OF WELDING PROCEDURES AND WELDERS

5.1 Welding procedure specification (WPS)

WPS shall be established in accordance with EN 288 part 2.

5.2 Qualification of welding procedures

Welding procedures used for structures requiring steel quality level I and II for all strength levels

and steel quality level III for SMYS ≥ 355 MPa shall be qualified in accordance with EN 288 part 3

and the additional requirements in this standard.

The qualification is primarily valid for the workshop performing the welding tests, and other

workshops under the same technical and quality management. It may also be transferred to and used

by a subcontractor, provided the principles of EN 729 part 2 are implemented and documented.


Rev. 4, Dec. 2000


5.3 Welding procedure approval record (WPAR) - Range of approval

5.3.1 For welding of steels with SMYS ≤≤≤≤500 MPa

The WPAR is valid within the limitations specified in EN 288 part 3, with the following

clarifications and modifications:

a) Control of heat input according to EN 288 part 3, section 8.4.7, shall apply. If an approval

testing have been performed at both a high and a low heat input level (with all specified

mechanical testing), then all intermediate heat inputs are also qualified.

b) When the steel to be welded has a Pcm ≥ 0.21, or a carbon content C ≥ 0.13%, then an increase

of more than 0.02 Pcm units or 0.03 carbon equivalent units (IIW formula) over the value on the

approval test shall require a new qualification test.

c) A change from wrought (rolled, forged) steel to cast steel or converse.

d) A change in delivery condition (normalised, thermomechanically controlled processed or

quenched and tempered).

e) A change in microalloying element or manufacturing technique for steel with SMYS ≥ 400

MPa.

f) A change in groove angle more than +20 deg./-10 deg.

g) A qualification of fillet welds carried out on plate thickness equal to or greater than 30 mm,

applies for all plate and throat thicknesses. Single layer fillet welds qualifies multi-layer, but not

the converse.

h) CTOD testing shall be included in the qualification of welding procedures for weldments with a

plate thickness above 50 mm for all strength levels for steel quality level I and II and for SMYS

>400 MPa for steel quality level III. CTOD testing shall be included in the qualification of

welding procedures for weldments with a plate thickness below and equal 50 mm if requested

by the designer for the specified steel quality level.

Testing shall be executed from as welded and PWHT weld assemblies as applicable, covering the

following combined conditions:

• Full penetration buttweld with K-, or half V -groove as deemed most representative for the

actual fabrication. V and X groove are acceptable for weld metal test..

• A welding procedure representing the maximum heat input to be used in fabrication.

• Maximum joint thickness (within 10%).

Assemblies shall be made and tested for the actual combination of steel manufacturer, welding

process and welding consumable (brand) used, except welding consumables used for root passes

only, provided these are removed completely by gouging and grinding.

Note: The changes specified in d) and e) need not require re-qualification if HAZ properties for the

material to be welded have been documented from the steel manufacturer for relevant thicknesses

and heat input ranges. If sufficient documentation from the steel manufacturer is not available, a

change of material shall require re-qualification of a reduced number of procedures. The number of

procedures to be re-qualified shall be sufficient to verify that the HAZ properties of the new

material is comparable with that used for the previous qualifications.


Rev. 4, Dec. 2000


5.3.2 For welding of steels with SMYS >>>>500MPa

In addition to the requirements given in 5.3.1 the following additional requirements apply for

welding of steels with SMYS >500 MPa

a) A change in steel manufacturer.

b) CTOD testing as described in 5.3.1 h) shall be executed for thicknesses above 30 mm

c) Stress relieving if required/specified by designer

d) When the steel to be welded has a Pcm ≥ 0,21 or a carbon content ≥ 0,13, then an increase of

more than 0,03 Pcm or 0,04 carbon equivalent units (IIW formula) over the value of the

approval test shall require a new qualification test.

5.4 Examination of the test weld

5.4.1 General

The type and number of tests shall be in accordance with table 5.1. Testing shall be performed in

accordance with EN 288 and the additional requirements given below.

The test weld shall be 100% examined for both surface and volumetric defects with the relevant

NDT-methods. The soundness of the weld shall comply with clause 9.


Rev. 4, Dec. 2000


Table 5.1 Type and number of tests

Mechanical testing

Joint

configuration

Joint

thickness

(mm)

Tensile

test

Bend

tests 1)

Charpy

V-notch

tests

Hardness

and

macro 5)

CTOD

Buttwelds

(Tubulars and

plates)

t<50

t≥50

2

2

2

2

4 sets

6 sets

1

1

Ref. 5.3.1h

and 5.4.4

T-joints

(plates) 4)

t<50

t≥503)

3)

4 sets 2)

6 sets

2

2

Tubular joints4)

t<50

t≥503)

3)

4 sets 2)

6 sets

2

2

Fillet welds All 2

Notes:

1. Bend tests shall consist of 1 face and 1 root bend specimen for t < 20 mm and 2 side

bend specimens for t ≥ 20 mm

2. If the dimensions of the joint does not allow Charpy V-notch testing, the Charpy V-

notch properties shall be documented on a butt weld joint made with the same

consumable and same base material, and welding parameters and thickness within the

range qualified for the joint.

3. It shall be documented on a butt weld test that the welding consumable used will have

sufficient tensile strength.

4. T-joints on plates qualify for tubular joints, and vice versa.

5. For welds on submerged structures with cathodic protection, the hardness limits in

NORSOK M-001 (i.e. max 350 HV10) shall apply in addition to the requirements of

EN 288. For SMYS 690 MPa max 400 HV10 shall apply.

5.4.2 Charpy V-notch testing

Sampling of Charpy V-notch impact tests shall be carried out in accordance with EN 875, with the

notch in the positions listed below. (All specimens shall be machined with the notch through the

thickness, 2 mm below the surface of the material.) (Designation in parenthesis refers to EN 875).

• Notch in centre of weld (VWT 0/2)

• Notch in fusion line (VHT 0/2)

• Notch in HAZ, 2 mm from fusion line (VHT 2/2)

• Notch in HAZ, 5 mm from fusion line (VHT 5/2)

For welds with a joint thickness of 50 mm or more, two additional sets of Charpy V-notch tests

shall be taken from the root area, with the notch in the following positions:

• Notch in centre of weld (VWT 0/b)

• Notch in fusion line (VHT 0/b)

The test temperature and energy requirements shall comply with table 5.2.


Rev. 4, Dec. 2000


Table 5.2 Charpy impact test temperatures and energy requirements for welding

procedure qualifications.

Material Steel quality level

thickness I II III

mm SMYS

≤400

400<

SMYS≤

500

SMYS

>500

SMYS

≤400

400<

SMYS≤

500

SMYS

>500

355≤

SMYS

≤500

SMYS

>500

t ≤ 12 0°C -20°C -20°C 0°C -0°C -20°C -0°C 0°C

12 < t ≤ 25 -20°C -40°C -40°C 0°C -20°C -40°C 0°C -20°C

25 < t ≤ 50 -40°C -40°C -40°C -20°C -40°C -40°C -20°C -40°C

t > 50 -40°C -40°C -40°C -40°C -40°C -40°C -40°C -40°C

Energy

Requirement 1)

36J 42J 60J 27J 42J 60J 27J 42J

Note:

1. The minimum average value is given in the table. No individual value shall be less than 70% of

the minimum average value. Reduction factors of energy requirements for subsize specimens

shall be: 7,5 mm - 5/6 and 5 mm - 2/3.

5.4.3 Transverse tensile testing

Testing shall be carried out in accordance with EN 288. The fracture shall be located outside the

weld metal (i.e. max. 20% of the fracture surface shall consist of weld metal/HAZ).

5.4.4 CTOD testing

The CTOD- technique with the Bx2B through-thickness notched type specimen according to BS

7448 Part 1 should be used. Three valid test specimens shall be obtained for each test position.

CTOD-testing of welds shall be carried out with the fatigue notch tip positioned in the coarse

grained region of the heat affected zone and in the weld metal. For HAZ, determination of the actual

location of the fatigue crack tip shall be performed after testing. Ref. is made to prEN 10225.

Note: Test assemblies may be given hydrogen diffusion treatment prior to testing, and specimens

may be precompressed.

If not specified otherwise, the test temperature for design temperature down to -14 °C shall be:

-10 °C for splash zone or above.

0 °C for submerged parts.

Other test temperature may be prescribed by the designer.

Three (3) valid test specimens shall be obtained for each notch location.

The requirement for minimum CTOD value shall be prescribed by the designer. If not specified, the

requirement for minimum CTOD value shall be as for the steel purchase order.

CTOD-testing of HAZ can be omitted if relevant CTOD properties in HAZ have been documented

previously in accordance with requirements in this standard, provided the requirements for the

essential variables are met.


Rev. 4, Dec. 2000


CTOD-testing of weld metal can be omitted if relevant CTOD properties in WM have been

documented previously in accordance with requirements in this standard, provided the requirements

for the essential variables are met.

The required fracture toughness level shall be decided in design for joints when steel quality level I

and II are required. Testing is normally not requested for structures with plate thickness below 40

mm for SMYS≤500 MPa or for structures with plate thicknes below 25 mm for SMYS>500 MPa.

5.5 Welder and welding operators qualifications

The welders, welding operators and tack welders shall be qualified in accordance with EN 287, EN

1418 or equivalent. For tack welders, an internal test may be used.

For welding of single sided acute angled tubular joints with α < 70º, welders shall be qualified with

a realistic joint, representing the minimum angle α to be used in production.

For welding of joints where steel quality level IV is selected, a certificate for welding of plates in

position PE is sufficient for welding all product forms.

6 FABRICATION AND WELDING REQUIREMENTS

6.1 General

All welding work shall be according to recommendations given in relevant part of EN 1011. The

manufacturer shall have a quality system, which fulfil the relevant part of EN 729 and the applicable

level of EN 719.

The fabricator shall apply a weld numbering system for identification on all shop drawings and as

reference in all documentation.

6.2 Forming

Cold forming of steel (i.e. forming below 250°C) shall be carried out within the deformation range

recommended by the steel manufacturer. For steel quality level I and II, the deformation limit

without documentation of mechanical properties is 5%.

If the deformation is more than the above given limits, either heat treatment shall be performed, or

strain ageing tests shall be carried out according to the following procedure:

• The material shall be permanently strained locally to the actual deformation.

• The material shall be artificially aged at 250°C for 1 hour.

• One set of 3 impact test specimens shall be tested from the base material in the strained plus

artificially aged condition. The notch shall be located within the plastically strained portion of the

material, in the part of the cross section which have received the highest strain.

• The impact testing temperature shall be as specified for the actual steel grade in question.

• The Charpy-V impact value shall comply with the minimum requirements for the steel grade and

shall not be more than 25% lower than the impact value for the material before deformation and

strain ageing.


Rev. 4, Dec. 2000


If forming is performed at temperature above 250°C, it shall be documented that the base material

properties, weldability, weldmetal and HAZ properties satisfy the actual MDS and this standard.

The percentage strain due to forming is defined as follows:

100% x diameter thicknessmid Forming

thicknessWallstrainPercent =

6.3 Assembly

6.3.1 General

In tubular joints, circumferential and longitudinal weld joints should not be placed in the shaded

areas shown in fig. 6.1, unless otherwise shown on design drawings.

" #

" #

" #

" #

" 2

"%

&

" 2

" 2

" 2

Longitudinal welds Circumferential welds

W1 = 75 mm or min. 2 times chord thickness

W2 = 150 mm or min. D/4

W3 = 600 mm or min. D

Fig. 6.1 Prohibited location of welds in tubular joints. Longitudinal respectively circumferential

welds shall not be located in shaded area.

6.3.2 Splices

Splices shall not be located in areas, noted as restricted on design drawings.

6.3.3 Tapering

Tapering shall be in accordance with the requirements given in relevant standards or drawings. If no

other requirements are specified, a tapering of 1:4 should be used.


Rev. 4, Dec. 2000


6.3.4 Bolting connection

Bolting material shall comply with requirements in NORSOK standard M-001, Material selection.

Holes shall be made by machine drilling.

6.3.5 Seal/blind-compartments.

Crevices and areas which become inaccessible after fabrication or assembly shall be sealed off from

the outside atmosphere. Seal welds shall have a throat thickness of at least 3 mm. Where steel items

shall be hot dip galvanised, hollow sections shall be ventilated.

6.3.6 Temporary cut-outs

Temporary cut-outs shall not be located in restricted areas as shown on design drawings. Temporary

cut outs shall have a corner radius not less than 100 mm. Temporary cut-outs shall be closed by

refitting the same or an equivalent plate and employing the same welding, inspection and

documentation procedures and requirements that govern the structural part in question.

6.3.7 Straightening of structural members

Members distorted by welding shall be straightened according to a detailed work instruction. The

base material properties shall satisfy the specified requirements after straightening.

Maximum temperature for straightening shall not exceed the temperature limit recommended by the

steel manufacturer, but it shall in no case be higher than 600°C.

6.3.8 Doubler plates

All temporary attachments which shall be flame cut or welded under water shall be attached to the

structure by using doubler plates.

All attachments in the splash zone shall be attached to the structure by using doubler plates.

6.4 Preparation for coatings

Edges of plates and structural shapes which are intended to be coated shall be rounded to

approximately 2 mm radius, unless otherwise indicated on design drawings.

6.5 Preparation and fit-up of weld bevels

Permanent backing strips are not accepted, unless shown in design drawings.

Buttering shall be carried out in accordance with a relevant WPAR. Buttering in excess of 20 mm

shall be avoided.

6.6 Welding processes

The welding processes listed in EN 288-3 are acceptable.


Rev. 4, Dec. 2000


6.7 Welding consumables

The manufacturers shall ensure that welding consumables applied for joints where steel quality level

I, II and III are required, meet the requirements for mechanical properties as specified for the

welding procedure qualification, in both as welded and (where applicable) PWHT condition.

This may be achieved through (alternatively):

• Batch testing including chemical analysis and mechanical properties, see annex D.

• An established and reliable system of batch certification against accepted supplier data sheets,

see annex C.

• For steels with SMYS ≥ 500 MPa Annex D is mandatory

Except for solid wires such consumables shall be classified by the supplier as extra low hydrogen,

i.e. HDM ≤ 5ml/100g weld metal. For self shielded flux cored wire HDM ≤ 8ml/100g may be

accepted, provided preheating temperature and post weld holding temperature and time is assessed

to avoid hydrogen cracking. Hydrogen testing shall be according to ISO 3690 or equivalent.

For all steels with SMYS ≥ 500 MPa special precautions shall be taken to verify that selected

consumables comply with hydrogen requirements. Stricter requirements than given above may be

relevant. Prequalification with mock-up structures shall apply if there is a risk for high restraint in

welding or erection.

Consumables for joints in steel quality level III (with SMYS <355MPa) and IV and for joining

stainless to carbon steel shall be selected with due consideration of base material properties,

thickness and weldability, to ensure sufficient weld strength, toughness and homogenity.Such

consumables shall be delivered with EN 10204 type 2.2 certificate, as a minimum.

All welding consumables shall be individually marked.

When certification according to Annex C is used, welding consumables (except welding fluxes)

shall be supplied with an inspection certificate (type 3.1B) in accordance with EN 10204, including

a statement of compliance with the Welding Consumable Data Sheet and the chemical composition

of the weld deposit (elements of the data sheet). Welding fluxes shall be supplied with a test report

(EN 10204 type 2.2), declaring conformity with the approved product type.

6.8 Preheat and interpass temperature

Preheating above 50ºC should be achieved by electric heating elements. Cutting torches are not

allowed for preheating.

The minimum interpass temperature shall not drop below the minimum required preheat

temperature. If not otherwise stated in the WPS, and qualified by the WPAR, the maximum

interpass temperature shall not exceed 250°C measured at the edge of the groove. For C- and C/Mn-

steels, a maximum interpass temperature of 250ºC may be used, even if a lower temperature was

recorded on the WPAR.

The preheat temperatures used during repair welding should be minimum 50°C higher than the

preheat used for the original weld.


Rev. 4, Dec. 2000


Note: Production welding of high strength steels with SMYS>500 MPa is normally more sensitive

to hydrogen cracking than experienced during welding for qualification. Special precautions,

including preheating temperature, minimum holding temperature and extended post weld holding

temperature for 24 hours or more, shall be taken into consideration.

6.9 Production welding

6.9.1 General

Welding shall be carried out in accordance with the WPS and applicable drawings.

Butt welds in joints where steel quality level I and II for all strength levels, or steel quality level III

for SMYS > 400 MPa are required shall, whenever possible, be welded from both sides.

If any welding is conducted after PWHT, the PWHT shall be repeated.

For joints in inspection category A, the ”straight” edges of K- and 1/2V-butt weld grooves shall have

a groove angle of at least 10O, unless it is documented that possible defects can be detected by the

UT technique used . (For K-grooves, the 10

O should be machined from the root to each plate

surface.)

Any occurrence of cracking during production welding shall be investigated. Welding should be

suspended until the cause of cracks and defects has been identified and measures taken to prevent

their reoccurrence. Cracks or other persistent weld defects may lead to revision and requalification

of the WPS.

6.9.2 Attachments

Temporary attachments as lifting lugs, lugs for scaffolding and assembly, supports for cables,

equipment, ladders or other fabrication and erection aids should be removed. If indicated on design

drawings that removal (full or partial) is not required, the temporary attachments may be left as is,

or removed only partially.

All welding of attachments shall comply with the requirements for the structure to which they are

attached. Temporary attachments shall be cut minimum 3 mm from the base metal and ground. The

ground area shall be visually examined and magnetic particle/penetrant tested (as relevant) in

accordance with the inspection category in question.

6.9.3 Stainless steel components

Permanent or temporary structural elements, attachments or penetration sleeves in stainless steel

materials may be selected for various purposes.

Requirements for welding and testing of stainless outfitting structures shall follow similar

classification principles as for other structural steel elements. All welding and testing of welds to

carbon steel structures shall as a minimum comply with the requirements for the structure to which

they are attached.

Unless other requirements apply higher alloyed consumables than given for the relevant stainless

component shall be selected for tacking and final welding.


Rev. 4, Dec. 2000


6.10 Post weld heat treatment (PWHT)

PWHT shall be required for structural welds in steel quality level I or II, or quality level III with

Re>400MPa, when the nominal thickness (as defined in EN 288-3, section 8.3.2.1) exceeds 50 mm,

unless adequate fracture toughness can be documented in the as welded conditions. For restrained

joints of complicated design, PWHT may be required for smaller thicknesses, independent of steel

quality level.

PWHT shall be carried out in accordance with a procedure which shall include:

• Heating rate.

• Cooling rate.

• Soaking temperature and time.

• Heating facilities.

• Insulation.

• Control devices.

• Recording equipment.

• Configuration of structure to be PWHT or details if local PWHT shall be carried out.

• Number and location of thermocouples to be used during PWHT.

The holding time and temperature shall be as recommended by the steel manufacturer

The temperature difference between different parts of the structure during soaking time shall not

exceed 30°C within the heated area. Double sided heating shall be used as far as possible.

The temperatures shall be continuously and automatically recorded on a chart.

6.11 Grinding

When grinding is specified on design drawings or is instructed as a corrective action, the grinding

shall be performed according to a detailed procedure. Grinding tools, direction, surface roughness

and final profile shall be specified. Reference samples for typical joints and sections may be

prepared and used for acceptance of treated welds. Typical examples for requirements for grinding

of joints are given in Annex A.

6.12 Peening

Weld improvement by peening shall be performed in accordance with detailed procedures.

Normally pregrinding of a groove will be required to assure correct location of peening area. Tools

for grinding and peening, surface roughness and profile of grinding as well as peening shall be

specified. Tools for check and measurements shall be described and shall be available during

operations. Documentation of correct performance shall include macrophotography. Typical

examples of requirements for peening of joints are given in Annex A.


Rev. 4, Dec. 2000


7 PRODUCTION TESTS

Production tests shall be selected on weldments in critical regions to verify that the specified

requirements have been meet. Minimum one test coupon is required from each applied welding

process.

Test coupons shall be welded in a manner which realistically simulates the actual production

welding, normally as extension of the production weld, and meet the requirements for welding

procedure approval tests.

CTOD testing is not required for production testing.

If a production test fails, the reason for the failure shall be determined and remedial action

implemented.

8 FABRICATION TOLERANCES

Fabrication tolerances shall be in accordance with Annex E, unless otherwise specified on drawings.

9 NON-DESTRUCTIVE TESTING (NDT)

9.1 General

The inspection category shall be decided by the designer in accordance with NORSOK N-004, and

shall be specified on the design drawings.

Final inspection and NDT of structural steel welds shall not be carried out before 48 hours after

completion except where PWHT is required. The time delay may be reduced to 24 hours for steel

grades with SMYS of 355MPa or lower, and for steel grades with SMYS of 420MPa or lower for

plate thicknesses below 40 mm, provided delayed cracking have not been observed for the materials

and/or welding consumables in question.

When PWHT is performed, the final NDT shall be carried out when all heat treatment have been

completed.

Prior to fabrication start-up, contractor shall implement a system for recording of weld defect rates.

The defect rates shall be recorded on a weekly basis from each production area (geographically split

in production areas at the same yard) and shall be reported together with the accumulated defect

rate. The defect rate statistics shall be used as a tool in weld quality control. Causes for defects shall

immediately be investigated and corrective actions shall be taken to prevent further occurrence.

Cracks detected with any NDT method shall require documented investigation/action by the

responsible welding engineer.

At a weekly high defect rate or at repeated occurrence of planar defects, two trigger levels apply for

extended NDT for welds in inspection category B, C and D. Two steps of actions apply within

trigger level 2.


Rev. 4, Dec. 2000


Trigger level 1

If a defect rate for any method exceed 10 % for a single week the extent shall be increased to 100 %

for all welds in question irrelevant of the required inspection category for the welds.

Trigger level 2

If a defect rate for any method of 5 - 10 % for a single week is observed the following two steps of

extended NDT shall apply:

Step 1.

A defect rate for any NDT method exceeding 5 % (1% for MT) for a single week require doubling

of the extent of NDT according to the inspection category. Spot extent shall be increased to 20 %.

Step 2.

If the defect rate for the weld length where the extended NDT is taken in accordance with Step 1

above exceed 5 %, the extent shall be increased to 100 % for all welds in question irrelevant of the

required inspection category for the welds.

The increased NDT extent shall cover welds of the same inspection categories, welded in the same

period of time when the high defect rate was produced, to assure that the weld quality is maintained

also with the lower extent of NDT. Unless the causes for defects found leads to immediate and

documented preventive actions, the higher level of extent of NDT shall be maintained until the

weekly defect rate is well below 5 %.

Generally, if the defect rate approaches 10 % during any stage in production welding, further

welding should be held until investigations are completed and corrective actions implemented.

A low defect rate may be used as basis for a reduction in the extent of NDT for inspection

categories B, C and D, provided that a correct defect rate identification is prepared for each weld

method, each NDT method and each production area. See Note 2 in Table 9.1.

1) welds)of parts testedof(Length

100%)length x (Defect :as defined is ratedefect The

Note 1: “Tested part of welds” means the part that is tested with the same NDT method.

NDT after repair shall not be included when calculating the defect rate.

9.2 Qualification of inspectors and NDT-operators

Personnel responsible for welding inspection - welding inspectors - shall be qualified in accordance

with NS 477 or equivalent scheme.

Personnel performing visual inspections of welded joints shall be qualified in accordance with

relevant part of EN 473/NORDTEST.

Personnel responsible for all NDT activities shall be qualified according to EN 473/NORDTEST

Level 3 or equivalent.

The NDT operators shall be qualified according to EN 473/NORDTEST Level 2 or equivalent.


Rev. 4, Dec. 2000


Operators simply producing radiographs and not performing evaluation, do not require level 2, but

shall have sufficient training.

In undertaking testing of castings or forgings the NDT operator should also document experience

with forged and cast products.

9.3 Extent of visual examination and NDT

The required minimum extent of examination/testing is given in table 9.1. Design drawings may

show areas of welds where testing is mandatory.

Testing performed shall be representative for the weld quality. Partial NDT shall normally be planed

for on all shop drawings.

Ultrasonic testing to reveal the presence of possible weld metal transverse cracking shall be

included for butt welds with thickness more than 25 mm. The testing shall be performed on

minimum 5% of welds in inspection category A and B for SAW (12) and FCAW (131 and 136)


Rev. 4, Dec. 2000


Table 9.1 Minimum extent (in %) of non-destructive testing for structural welds.

Inspection

category

Type of

connection

Visual

examination

Extent of testing

RT UT MT

A Buttw.

T-conn.

Fillet/partial

100

100

100

10

-

-

100

100

-

100

100

100

B1)

Buttw.

T-conn.

Fillet/partial

100

100

100

Spot

-

-

50 2)

50 2)

-

100 2)

100 2)

100 2)

C1)

Buttw.

T-conn.

Fillet/partial

100

100

100

-

-

-

20 2)

20 2)

-

20 2)

20 2)

20 2)

D1)

All conn. 100 - - spot

E All conn. 100 - - -

Legend -

RT = Radiographic testing

UT = Ultrasonic testing

MT = Magnetic particle testing

Spot means 2 - 5%.

Note:

1. The extent of NDT shall be increased for Inspection categories B, C and D if repeated

occurrence of planar defects are revealed or if the weekly defect rate for any NDT

method, including all types of defects, are as given for the limits below.

Trigger level 1 - Defect rate exceeding 10 %:

The extent shall be increased to 100 % irrelevant of inspection category.

Trigger level 2 - Defect rate of 10 % and below calls for stepwise increase in extent:

Step 1 - Defect rate exceeding 5 % ( MT exceeding 1%): The original extent shall be

doubled. Spot extent shall be increased to 20 %.

Step 2 - Defect rate for the extended testing under Step 1 exceed 5 %: The extent shall

be increased to 100 % of the weld lengths in question for all inspection categories.

The required level of increased extent shall be maintained until a defect

rate below 5 % is re-established and documented.

2. The extent may be reduced to 50% of the specified extent, based on experience and documented

records with similar joints, provided the defect rate (see clause 10.1 and 11.1) for UT/RT is

<2.0% and for MT is <0.2% during the last 100m of weld. The last 100m shall be continuously

updated every week. If the defect rate exceeds the limits given above, the normal extent of NDT

shall apply again.

A possible reduction in the extent of NDT shall be considered separately for each welding

method and each production area.


Rev. 4, Dec. 2000


When partial testing is defined for welds in an area, the testing shall be spread such that the most

essential members and nodes are included in the inspection, and such that areas of welds most

susceptible to weld defects are covered.

The specified percentage to be tested in table 9.1 refers to the total length of welds in each

inspection category.

All WPS's used and welds representing all welding personnel involved in the fabrication shall be

subject to NDT.

During the initial fabrication the extent of UT and MT of inspection category B and C welds shall

be intensified, normally to twice the level given in table 9.1. This extent shall be maintained for a

weld and test length sufficient to conclude that the weld repair percentage is at a reasonable level.

The increased initial testing may be accounted for in the overall extent provided the initial testing

confirms consistent good workmanship.

In addition to what is listed in table 9.1, the following shall apply for inspection category A and B:

a) One film at each end for longitudinal welds of tubulars (including tubulars for nodes and stubs).

b) Where radiographic testing is required, intersection welds, and those locations where presence

of defects is deemed to be most harmful, shall be tested.

c) Ultrasonic and radiographic testing shall not overlap, except when 100% UT is specified.

However, ambiguous imperfections revealed by UT shall in addition be tested by RT.

d) Ultrasonic testing is normally not applicable for thicknesses less than 10 mm. For such

thicknesses, UT may be replaced with RT. In general, RT should be considered if UT is not

possible. Radiographic testing is normally not applicable for thicknesses above 40 mm.

e) MT shall be performed on both external and internal surface as accessible or as required by the

designer.

9.4 Visual examination and finish of welds

The visual examination shall be carried out in accordance with EN 970.

9.5 Radiographic testing

Radiographic testing shall be carried out in accordance with EN 1435, Class A.

Suspect planar indications discovered by RT shall be type determined, located and sized by UT.

Penetrameters of wire type (according to EN 462-1 or equivalent) shall be utilised. Sensitivity level

shall be in accordance with EN 462 part 3, Class A. However, if gamma ray sources are used, the

sensitivity shall be 2% or better.

9.6 Ultrasonic testing

Ultrasonic testing of welds in plate and tubular butt welds and double side welded tubular joints

shall be performed in accordance with EN 1714, examination level C.

Reference blocks shall be made with thickness and side-drilled holes in accordance with table 9.2.

DAC reference curves shall be established.


Rev. 4, Dec. 2000


The effective test range of a DAC curve shall be determined by the point at which the curve has

fallen to 25% FSH, when it will be necessary to raise the curve using reflectors at increased depth.

The reference block shall be from a steel type that is representative for the steel to be inspected.

Where ultrasonic testing is to be performed on steel produced by controlled rolling or

thermomechanical treatment, reference blocks shall be produced both perpendicular to, and parallel

to, the direction of rolling. The rolling direction shall be clearly identified.

The actual refracted angle for each probe measured from the reference block or as measured on the

actual object being examined, shall be used when plotting indications.

A transfer correction between the reference block and the test surface shall be performed.

Ultrasonic examination procedures shall be sufficiently detailed to ensure 100% of the weld body

and heat affected zones are examined for longitudinal defects.

All indications exceeding 20% DAC shall be investigated to the extent that they can be evaluated in

terms of the acceptance criteria.

All indications exceeding acceptance criteria shall be reported, unless more stringent requirements

are given in table 9.5.

The examination record shall include the position, the echo height, length, depth and type of

indication.

9.7 Magnetic particle and Penetrant testing

Magnetic particle testing shall be carried out in accordance with prEN 1290. Magnetic yokes using

alternating current shall be used. Prods are acceptable where the geometry of the welded joint

prevents the use of yokes. Permanent magnets are not acceptable.

For non-magnetic materials penetrant testing in accordance with EN 1289 should be used.

9.8 Acceptance criteria

9.8.1 General

All welds shall comply with the requirements given below, in 9.8.2 - 9.8.5.

9.8.2 Visual examination

All welds shall show evidence of good workmanship. The quality shall comply with the

requirements of table 9.3.

9.8.3 Radiographs

The soundness of the welded joint shall comply with the requirements of table 9.4.

9.8.4 Ultrasonic testing acceptance criteria

The acceptance criteria for welds shall comply with table 9.5 unless more stringent requirements are

specified by the designer.


Rev. 4, Dec. 2000


9.8.5 Magnetic particle testing

Linear indications (i.e. indications with a length/width ratio above 3 and length above 1.5 mm ) are

not acceptable. Any linear indications shall be ground and re-examined. Rounded indications shall

be evaluated in accordance with the requirements of table 9.3.

The same acceptance criteria applies for penetrant testing.

9.8.6 All methods

All defects shall be repaired according to clause 10.

Defects may be accepted by the relevant parties when repair work is considered detrimental to the

total integrity of the weld. Such acceptance shall be based on a fitness for purpose evaluation in

accordance with BS 7910 , DNV RP D404 or other recognised methods.

Table 9.2 Calibration reference block requirements

Thickness of

material to be

examined (mm)

Thickness of block Diameter of hole Distance of hole

from one surface

10 < t < 50 40 or t Ø 3 mm +/-0.2 mm

50 < t < 100 75 or t t/2 and t/4.

100 < t < 150 125 or t Ø 6 mm +/-0.2 mm Additional holes are

150 < t < 200 175 or t allowed and

200 < t < 250 225 or t recommended

t > 250 275 or t


Rev. 4, Dec. 2000


Table 9.3 Structural steel welds. Visual and MT-acceptance criteria for structural steel

welds

Welding Acceptance criteria

Type of defect Insp. cat. A, B Inspection category C, D, E

Cracks Not acceptable Not acceptable

Incomplete

penetration or lack

of fusion

Not acceptable Single - side weld:

Length < t/2, max 10 mm

Defects shall be regarded as a continuous

defect if the distance between them is < t.

Undercut Max depth 0.5 mm

Continuous

undercut is not

permitted

Maximum depth 0.75 mm

Continuous undercut is not permitted

Surface porosity

Exposed slag

Not acceptable Not acceptable. However, the following

defects may be acceptable if it does not

conflict with surface treatment requirements:

Accumulated pore diameters in any area of 10

x 150 mm is not to exceed 15 mm. Max. size

of a single pore is t/4 or 4 mm, whichever is

the smaller.

Concave root Max. concavity 0.5 mm if the transition is smoothly formed.

Excessive pen. 1)

Max. 3 mm

Roughness of weld

(fig. 1)

“U” shall be less than 2.5 mm. Weld surface shall be smooth,

without sharp transitions. The bottom of roughness in butt welds

shall not be below the base material surface.

Misalignment of

butt welds (fig. 2)

Max. misalignment (M), 0.15 x t or max. 4 mm,

whichever is the smaller.

Reinforcement of

butt welds (fig. 3) 1)

“t” less or equal to 10 Max reinforcement “C” 2 mm

“t” greater than 10, up to 25 Max reinforcement “C” 3 mm

“t” greater than 25, up to 50 Max reinforcement “C” 4 mm

“t” greater than 50 Max reinforcement “C” 5 mm

Reinforcement of

fillet/partial pen.

welds (fig.4) 1)

“a” less or equal to 10 Max reinforcement “C” 2 mm

“a” greater than 10, up to 15 Max reinforcement “C” 3 mm

“a” greater than 15, up to 25 Max reinforcement “C” 4 mm

“a” greater than 25 Max reinforcement “C” 5 mm

Symmetry of fillet

welds (fig. 5)

“a” less or equal to 6 Max difference, b - h: 3 mm

“a” greater than 6, up to 13 Max difference, b - h: 5 mm

“a” greater than 13 Max difference, b - h: 8 mm

Grinding arc strikes

etc. Removal of

temporary

attachments 2)

Grinding of base material shall not exceed 7% of the wall thickness

or max. 3 mm. Repair welding and inspection shall be performed if

removal of the base metal exceeds the specified requirements.

Sharp edges Minimum 2 mm radius (Ref. 6.4)


Rev. 4, Dec. 2000


Notes:

1) Localised reinforcements exceeding the above requirements are acceptable.

2) Temporary attachments shall be cut min. 3 mm from the base metal and ground smooth.

The ground area shall be visually inspected and MT shall be performed in accordance

with the inspection category in question.

3) When required (ref. 6.11), grinding of the surface shall be specified. Typical examples of

grinding requirements are given in annex A.

'

'

Fig. 1 Roughness of weld

(

)

*

)

Fig. 2 Misalignment of butt weld Fig.3 Reinforcement of butt weld

(

+

(

+ +

,

-

Fig. 4a Fig. 4b Fig. 5

Reinforcement of fillet weld Reinforcement of partial pen. weld Symmetry of fillet weld


Rev. 4, Dec. 2000


Table 9.4 Structural steel welds, RT acceptance criteria

Type of defect Inspection category

A, B C, D, E

Internal porosity (Note 1)

Isolated:

Pore diameter max t/4, but max.6

mm

max t/3, but max. 6 mm

Cluster:

Pore diameter max. 3 mm max. 4 mm

Scattered:

Accumulated pore diameters in any

10x150 mm area of weld

max. 20 mm max. 25 mm

Slag inclusions, or piping porosity (Note 2)

Width t/4, max .6 mm t/3, max. 6 mm

Length (Note 3) 2t, max 50 mm 4t, max. 100 mm

Incomplete penetration, lack of fusion

Length (Note 2) t, max. 25 mm 2t, max 50 mm

Cracks Not acceptable Not acceptable

Notes:

1) If more than one pore is located inside a circle of diameter 3 times the pore diameter, the

pores are to be considered as a cluster.

2) Defects in a line where the distance between the defect is shorter than the longest defect

shall be regarded as one continuous defect.

3) No length limitation for width ≤2 mm for t ≥20 mm and for width ≤1 mm for t <20 mm.


Rev. 4, Dec. 2000


Table 9.5 Structural steel welds. UT acceptance criteria.

Description Inspection category

A + B

Inspection category

C, D, E

Notes

General If the type of defect can not be ascertained with certainty the

defect shall be repaired when the length exceeds 10 mm and the

echo height exceeds the reference curve.

1

2

3

4

Cracks Unambiguous cracks are unacceptable regardless of size or

amplitude.

Lack of

fusion or

incomplete

penetration

Internal defects :

I: The echo height exceeds the reference curve:

Max length t, Max length 2t,

max 25 mm max 50 mm

II: The echo height is between 50 and 100% of the reference

curve:

Max length 2t, Max length 4t,

max 50 mm max 100 mm

Surface defects are not acceptable except:

For root defects in single sided welds , the max length for which

the echo height exceeds the reference curve shall be:

Max length t, Max length 2t,

max 25 mm max 50 mm

1

2

3

4

5

Slag

inclusions

When echo height exceeds the reference curve:

Max length 2t, Max length 4t,

max 50 mm max 100 mm

1

2

Porosity Repair is required if porosity may mask for other defects. 1

Notes:

1. Type of defect shall be decided by:

I: Supplementary non-destructive testing.

II: The ultrasonic operator's assessment of the defect, using his knowledge of the

welding process, signal geometry, defect position etc.

2. If elongated defects are situated on line and the distance between them is less than the

length of the longest indication, the defects shall be evaluated as one continuous defect.

3. Defect length shall be determined by the 6dB drop method from the end of the defect

(for defects larger than the beam) or by the maximum amplitude technique (for defects

smaller than the beam).

4. With UT performed from only one side of the weld with only one surface accessible, the

acceptable echo heights are reduced from 100% to 50% and from 50% to 20%,

respectively.

5. With “internal defects” it is meant defects which are located more than 6 mm from the

nearest surface. A defect is classified as a “surface defect” if any part of the defect is

located less than 6 mm or t/4, whichever is smaller, from the nearest surface.


Rev. 4, Dec. 2000


10 REPAIR

10.1 Definitions

Weld discontinuities: Irregularities in the body of the weld or on the weld surface classified as either

weld imperfection or as weld defect.

Weld imperfection: Discontinuities that are within the acceptance criteria defined in clause 9 and

are considered to have no practical limitations on the intended use of the product. Weld

imperfections may be left without remedial work. Cosmetic grinding may be performed at the

discretion of the fabricator.

Weld defect: Discontinuity with a size and/or density that exceeds the acceptance criteria defined in

clause 9.

10.2 Correction of welds containing defects

All repairs shall be carried out in accordance with established procedures.

Welds containing cracks shall not be repaired, until the reason for the cracking has been determined.

If necessary, the defective part of the weld shall be cut out for further examination. Crater cracks

may be repaired by grinding followed by NDT and subsequent repair welding according to an

accepted repair welding procedure.

Other defects shall be corrected by grinding, repair welding or re-welding.

When weld defects are removed by grinding only, the final weld surface and the transition to the

base material shall be smooth. Removal of defects shall be verified by local visual inspection, aided

by applicable NDT methods. If applicable, the remaining thickness in the ground area shall be

measured. Repair welding is required if the remaining thickness is less than that specified.

10.3 Repair by welding

10.3.1 Repair and re-repair welding

Before repair welding, the defect shall be completely removed.

The excavated area shall have smooth transitions to the metal surface and allow good access for

both NDT after excavation and subsequent repair welding. After excavation, complete removal of

the defect shall be confirmed by MT or PT. PWHT shall be performed after repair if specified for

the original weld.

The excavated groove shall be minimum 50 mm long, measured at defect depth even if the defect

itself is smaller. Defects spaced less than 100 mm shall be repaired as one continuous defect.

After repair welding the complete weld (i.e. the repaired area plus at least 100 mm on each side)

shall be subjected at least to the same NDT as specified for the original weld.

Repair welding may only be carried out twice in the same area.


Rev. 4, Dec. 2000


10.3.2 Re-welding

Re-welding shall be performed in accordance with the procedures and WPS utilised for the original

weld, and includes complete removal of the original weld and HAZ.

10.4 Repair welding procedure

Repair and re-re-repair welding may be performed using the same WPS as for the original weld, or a

separately qualified procedure.

For repairs using a different process, and/or consumable, a separate WPS shall be qualified if

required by 5.2. Mechanical testing may be limited to HAZ Charpy V-notch testing in the original

weld, provided the process/consumable is backed up by other WPAR’s.

10.5 Correction of distortion

Improperly fitted parts should be cut apart and re-welded in accordance with the applicable qualified

WPS.

Parts distorted by welding, beyond the tolerances, should be straightened in accordance with the

requirement in clause 6.


Rev. 4, Dec. 2000


ANNEX A 1 - TYPICAL GRINDING DETAILS FOR HIGH FATIGUE

UTILISATION (INFORMATIVE)

./01 .'2'345 6789. :589&89: &;.483

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#FGBB

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./01 2'.. ";3& 6789. :589&89: &;.483

Notes to figures:

1. For removal of undercuts the toe of the weld should be blended in a smooth transition and

extended below the plate surface in order to remove the toe defects.

2. Grinding should extend below plate surface to a minimum of 0.5 mm below the bottom of any

visible undercut and ensuring that no exposed defects remain, using a rotary burr grinder.

Grinding marks should run at right angels to weld axis and under no circumstances parallel to it.

3. Minimum radii of weld profiles after blending should not be less than 10 mm.

4. Upon completion of blending of toe the whole of the ground surface shall be inspected with

100% visual examination and 100% MT.

5. Ground surface shall be free of any cracks or cracklike indications, and there shall be no

evidence of undercut or overlap.


Rev. 4, Dec. 2000


ANNEX A 2 - TYPICAL PEENING DETAILS FOR HIGH FATIGUE

UTILISATION (INFORMATIVE)

A.2.1 General

Peening of local area as weld toe or weld trasition is an acceptable method to improve fatigue life of

structures. Peening is applied together with grinding where grinding serves the purposes to remove

stress risers such as surface defects and to define a steering grove for the tool in the area to be

peened. Both grinding and peening require skills and preparations not normally available in

fabrication yards. Due to the dependancy of correct performance specific precautions shall be taken

when peening is planned for.

A.2.2 Requirements for application

When peening is planned for the following preparations are required :

• Nomination of responsible engineer for preparations, performance and documentation

• A complete responsibility and personnel matrix

• Statement on expected or required improvements

• Detailed work instructions

• Documentation on operators experience, skill or training

• Selection of peening methods to be applied

• Detailed mark up drawings showing all areas of application

• Detailed stepwise procedure for the work, including:

grinding details as tools, radius, depth and direction

tools to be used for peening

method, intensity and extent of peening

quality control measures

documentation of performance and results

• Verification of performance such as experiments, tests or other relevant information

• As built record index for the final DFI resume

As preparation for peening the surface shall be dressed in a way that makes lack of coverage

detectable, preferably by stone grinding. Applicable tool for grinding is normally a rotary burr or

stone of 6 to 8 mm diameter when a single tool hammer is used and 10 to 12 mm when a needle

hammer is used. The depth of the groove is approximately 0.5 mm below the original surface.

All surface defects shall be removed by grinding prior to peening.

Applicable tool for peening is normally pneumatic hammers. A needle hammer is normally used

when a wider area shall be covered. For local toe peening a single tool hammer is recommended.

Correct tool is essential to maintain correct peening in compliance with requirements.

Special tools with adjusted curvature shall be prepared in accordance with weld geometry.

Needle peening shall be applied with a coverage of minimum 200 %. Single hammer peening shall

result in a fully covered hammered groove where the surface is smooth with uniform indentation.

All traces from previous grinding shall be completely removed.


Rev. 4, Dec. 2000


Devices for quality control and documentation shall be thoroughly selected. Groove depth

measuring tools and macro photo is normally applied. Reference specimens shall be prepared for

comparison between ground and final peened surfaces.


Rev. 4, Dec. 2000


ANNEX B - CORRELATION BETWEEN STEEL QUALITY LEVEL, MDS

NUMBER AND STEEL GRADE/DESIGNATIONS (NORMATIVE)

Steel

quality

level

NORSOK

MDS No.

Note 1

Rev.

No.

Reference

standard

Product type Steel grade Former Steel

grade

Y20 3 Plates S355G10+N/G10+M S355N4z/M4z

Y21 3 Rolled sections S355G12+N/G12+M S355N3z/M3z

Y22 3 Seamless tubulars S355G15+Q/G15+N S355Q3z/N3z

Y30 3 Plates S420G2+Q/G2+M S420Q3z/M3z

Y31 3 Rolled sections S420G4+M S420M3z

Y32 3 prEN 10225 Seamless tubulars S420G6+Q(mod) S420Q3 (z mod)

I Y40 3 Plates S460G2+Q/G2+M S460Q3zM3z


Y42 3 Seamless tubulars S460G6+Q(mod) S460Q3(z-mod)

Y50 3 Plates S500G2+Q/G2+M S500Q3z/M3z


Y52 3 Seamless tubulars S500G6+Q(mod) S500Q3(z-mod)

Y70 Plates S690+Q

Y25 3 Plates S355G9+N/G9+M S355N4/M4

Y26 3 Rolled sections S355G11+N/G11+M S355N3/M3

Y27 3 Seamless tubulars S355G14+Q/G14+N S355Q3/N3

Y28 Welded tubulars S355G13+N

Y35 3 Plates S420G1+Q/G1+M S420Q3/M3

Y36 3 Rolled sections S420G3+M S420M3

Y37 3 Seamless tubulars S420G6+Q S420Q3


II Y46 3 prEN 10225 Rolled sections S460G3+M S460M3



Y56 3 Rolled sections S500G3+M S500M3


Y70 Plates S690+Q

Y05 EN 10113 Plates and sections S355NL/ML

Y06 prEN 10225 Tubulars S355G1+N

III Y07 EN 10210 Hot finished tubulars S355NH

Y08 EN 10219 Cold formed tubulars S355MLH

Y15 En 10113 Plates and sections S420NL/ML

Y16 EN 10219 Cold formed tubulars S420MLH

S235JRG2

EN 10025 Plates and sections S275JR

S355J0

S235JRH

IV Y01 3 EN 10210 Hot finished tubulars S275J0H

S355J0H

S235JRH

EN 10219 Cold formed tubulars S275J0H

S355J2H

Note 1 NORSOK Material data sheets are published in NORSOK standard M-120.


Rev. 4, Dec. 2000


ANNEX C - QUALIFICATION OF WELDING CONSUMABLES BY DATA

SHEETS (NORMATIVE)

C.1 SCOPE

The purpose of certification is to verify that each batch of consumables has a chemical composition

within limits as specified by the supplier in conformance with a recognised classification standard.

By controlled and certified chemistry the supplier also confirms that mechanical properties of the

weld metal fulfil the minimum requirements specified for the product.

For this specification a batch (or lot) is defined as the volume of product identified by the supplier

under one unique batch/lot number, manufactured in one continuous run from batch controlled raw

materials.

Each individual consumable (brand name and dimension) shall be certified per batch, except for

solid wire (GTAW, GMAW, SAW), originating from the same heat, where one diameter may

represent all.

C.2 DATA SHEET

Each welding consumable or combination of consumables shall have a unique data sheet, issued as

a controlled document within the suppliers quality system. The purchaser shall base his selection,

ordering and receiving of consumables upon reviewed and accepted data sheets.

The data sheet shall give guaranteed limits and/or minimum values for composition and mechanical

properties, determined under defined reference conditions.

If the consumable shall be used for welds in PWHT condition, then the properties shall also be

documented in PWHT condition in addition to the as-welded condition.

Specifically this shall include, as applicable:

• Chemical analysis limits for solid wires and metal powders. For information also typical weld

metal analysis, using a relevant shielding gas or flux.

• Chemical analysis limits of weld metal from coated electrodes and cored wires, deposited

according to EN 26847. For information also specified limits for S, P and N in the core wire or

strip.

The analysis shall include limits for all elements specified in the relevant classification standard

and/or intentionally added and for residual elements known to influence weld metal quality.

Minimum:

C, Si, Mn, S, P, Cu, Ni, Cr, Mo, V, Nb.

For SAW fluxes the analysis shall be given as ranges for all main ingredient and flux basicity.


Rev. 4, Dec. 2000


• Mechanical properties (range or/and guaranteed minimum) of the weld, deposited and tested

according to prEN 1597 part 1 and including tensile strength, yield strength elongation, notch

toughness Charpy-V at -40ºC. For information also typical properties of a relevant butt weld

should be added.

• Diffusible hydrogen content HDM max., including any information on drying, restricted welding

parameters etc. required to ensure this value in practice.

• When relevant for the product, basic information about CTOD properties, to be supported by

separate test reports as required and agreed.

Data sheets shall also contain product classification according to recognised standards, relevant

approvals and information on packing, storage etc. as required for correct application and use of the

product.

C.3 CERTIFICATE

Every batch of consumables shall be supplied with an inspection certificate 3.1.B, containing as a

minimum the specific tested chemical composition of the wire or weld metal, as applicable. The

chemical elements shall conform to those of the data sheets, with a statement “below specified

maximum” acceptable for residual elements.

The supplier may optionally add information about mechanical properties, based on specific or non-

specific type of control. (Ref. EN 10204). Other tests may also be agreed between supplier and

purchaser.

Certificates shall be actively used by the purchaser to control received consumables against the

accepted data sheet. Full conformance of chemical composition shall be required to release each

batch for fabrication welding.


Rev. 4, Dec. 2000


ANNEX D - WELDING CONSUMABLE DOCUMENTED BY BATCH

TESTING (NORMATIVE)

D.1 SCOPE

The purpose of the batch testing is to verify that the consumables remains nominally equivalent to

that used for welding procedure qualification, with respect to chemistry and mechanical properties.

For this specification a batch (or lot) is defined as the volume of product identified by the supplier

under one unique batch/lot number, manufactured in one continuous run from batch controlled raw

materials.

Each individual product (brand name and dimensions) shall be tested once per batch, except for

solid wire originating from the same heat, where one diameter may represent all. SAW fluxes do not

require individual testing, while SAW wires shall be tested in combination with a selected, nominal

batch of flux.

Chemical Analysis

For solid wires and metal powders the analysis shall represent the product itself.

For coated electrodes and cored wires the analysis shall represent the weld metal, deposited

according to EN 26847.

The analysis shall include:

• All elements specified in the relevant classification standard and /or intentionally added.

• The main impurities S, P and N.

D.2 MECHANICAL PROPERTIES

Unless otherwise specified the properties shall represent all weld metal, deposited and tested

according to prEN 1597 part1.

Properties tested shall include:

• Tensile strength, yield strength and elongation.

• Impact strength Charpy-V, at temperatures -40ºC, or as specified by purchaser.

The need for other types of tests shall be evaluated for the application in question, such as:

• Mechanical properties based on a defined butt weld rather than all weld metal test.

• Mechanical properties in the PWHT condition.

• CTOD testing.

• Testing of hydrogen level.

D.3 DOCUMENTATION

Batch tests shall be documented by an inspection certificate 3.1B to EN 10204, with reference to a

recognised product classification standard and containing all specified test results.


Rev. 4, Nov. 2000


ANNEX E - FABRICATION TOLERANCES (NORMATIVE)

CONTENTS

E.1 SCOPE AND OBJECTIVES 38

E.2 CODES, STANDARDS AND SPECIFICATIONS 38

E.3 DEFINITIONS 38

E.4 GENERAL REQUIREMENTS 39

E.4.1 Implementation policy of requirements 39

E.4.2 Procedures and documents 40

E.4.3 Qualification of inspectors 40

E.4.4 Instrument reliability 40

E.4.5 Reference temperature 40

E.4.6 Control methods 41

E.4.7 Interface criteria’s 43

E.4.8 Alignment Requirement 43

E.5 FABRICATION TOLERANCES FOR STRUCTURAL COMPONENTS 44

E.5.1 I / H- Girders 44

E.5.2 Box Girders 45

E.5.3 Tubulars 46

E.5.4 Panels 49

E.5.5 Girder Nodes 50

E.5.6 Box Nodes 52

E.5.7 Tubular Nodes 53

E.5.8 Cast and Forged Elements 55

E.5.9 Curved and cylindrical shell 56

E.5.10 Conical transitions 56

E.6 ASSEMBLY TOLERANCES 57

E.6.1 Topsides and modules 57

E.6.2 Jacket and other tubular frame structures 58

E.6.3 Floating production units 63

E.6.4 Subsea structures 64

E.7 FABRICATION TOLERANCES FOR SPECIAL ITEMS 65

E.7.1 Crane Pedestal 65

E.7.2 Skid Beams 65

E.7.3 Outfitting Structure 65

E.7.4 Installation Aids 65

E.7.5 Grillages 65

E.7.6 Cranes 65


Rev. 4, Nov. 2000


E.1 SCOPE AND OBJECTIVES

This annex defines the maximum allowable dimensional tolerances for offshore steel items and

structures.

The Designer may, however, specify stricter tolerances and additional tolerances. These will, in case

take presedence over this annex.

Note: It should be observed that the requirement to fabrication tolerances in this annex may be more

strict than the manufacturing tolerances for steel products according to M-120.

The intention of this annex is to give dimensional tolerances which will ascertain that:

• The calculated strength and fatigue resistance is present in the structures

• Items and structures can be assembled without dimensional rework

• All parts of the structures are suitable for their intended use

• The structures are thrustworthy relative to measurements given on the structural drawings

• The relevant components tolerances are achieved and maintained after the components final

incorporation in the completed structure(s)

E.2 CODES, STANDARDS AND SPECIFICATIONS

Reference standards for this annex are:

ISO-8062 Castings - System of dimensional tolerances and machining

ENV 1090-1 1995 for Cranes. Execution of steel structures - Part 1: General

E.3 DEFINITIONS

Terminology used in conjunction with this annex:

AFC drawing:

Engineering drawings formally approved for construction.

Centreline:

A real or imaginary line that is equidistant from the surface or sides of the (measured) object.

Deflection:

Load imposed curves, bends, angles or irregularities from an unloaded structure. Note: Opposed to

straightness deviation.

Flatness:

Flatness is here defined as vertical offset at any point from a plane parallel with the surveyed object.


Rev. 4, Nov. 2000


Grid System:

The grid system is defined as the design reference system for all parts, components and elements of

a completed structure.

The grid system defines the 3D position of any item within a completed structure.

The grid system is normally denoted in one of the following manners:

• x, y and z coordinates,

• North, east and height coordinates

• Longitudinal, transversal and elevation coordinates.

The grid system defines the design origo (location and elevation datum) for a structure.

Position Deviation:

The specified point's actual position relative to it's nominal position.

(Measured value minus nominal value equals deviation).

Reference Lines:

Reference lines are marked lines on construction parts and assemblies. The reference lines shall be

parallel to, and in determined distances from grid lines.

Straightness Deviation:

Curves, bends, angles or irregularities from a straight generator.

Note: Straightness deviation is regarded to be fabrication imposed irregularities and not caused by

elastic deformation.

Survey Reference System

A reference system constituting of fixed and coordinate determined points, from where surveys can

be performed, and where the location and elevation of the fixed points are identifiable relative to the

grid system.

Work Point:

A marked or imaginary point on a member or structure from which dimensions shall be related.

E.4 GENERAL REQUIREMENTS

E.4.1 Implementation policy of requirements

The tolerances given in this annex shall be applied for completed structures.

For single elements to be parts of complex structures, specification of detailed and more stringent

tolerances for each fabrication and erection sequence may be necessary in order to meet the

requirements of this annex in the completed structure. Such tolerances shall be presented in the

plan/scope of work for fabrication.

Specification of detailed and more stringent tolerances for intermediate and final interfaces may also

be necessary in order to meet the requirements of this annex in the completed structure.

The allowable tolerances given for individual members shall not cumulate to give unacceptable

deviation for the finished section or complete structure.


Rev. 4, Nov. 2000


If tolerances given for individual sections and components are conflicting, those tolerances

representing the stricter values shall be governing.

If no appropriate tolerance is stated in this document, the tolerance requirements shall be agreed.

All tolerance requirements are based on nominal values on unloaded structure.

E.4.2 Procedures and documents

The following procedures and documents shall be prepared:

Plan for fabrication and erection including methods, techniques and dimensional control to assure

that all structures can be fabricated and assembled to dimensions within the specified tolerances.

The plan shall assure that all allowable tolerances for individual elements are not cumulative to the

extent of exceeding the allowable tolerance for the complete structure.

Dimensional inspection procedures relevant for the structures and any additional specifications

needed to those included in this document, subject drawings or other regulations/guidelines for the

structural fabrication.

The following documents shall be prepared prior to start of fabrication:

• Plan for dimensional assurance/inspection

• Dimensional inspection procedures

During fabrication and erection deviations outside the specified tolerances shall be identified and

informed of in advance of the formal handling of deviations.

The detailed deviation reports shall be available at all stages in fabrication, and shall be submitted

on request.

Final documentation shall be prepared in correspondence with the requirements for as built

documentation and fabrication record.

E.4.3 Qualification of inspectors

Personnel responsible for dimensional control activities shall have a minimum background of at

least 5 years relevant experience in industrial surveying.

Personnel monitoring dimensions and tolerances shall have relevant training in use and

understanding of instruments, and subsequent calculations, enabling them to perform all necessary

controls of own work performance.

E.4.4 Instrument reliability

All instruments used shall be in accurate permanent adjustment, have current valid control

certificates and be subject to a programme of periodic checking.

E.4.5 Reference temperature

Reference temperature for survey activities should be +20 deg. C.


Rev. 4, Nov. 2000


The field work temperature shall as a minimum be noted on all dimensional reports, when this is

necessary for future use of the report and the component surveyed. For components to be assembled,

built under significantly different temperature conditions, dimensions shall be computed to the

reference temperature and this shall be annotated on any subsequently produced document or report.

E.4.6 Control methods

E.4.6.1 Reference System

Prior to fabrication a survey reference system related to the grid system, shall be established. The

survey reference system shall use the same numerical values, and the same orientation directions of

the system axis as the grid system.

The system's north axis shall be positive toward platform north (or bow, if ship).

The system's east axis shall be positive toward east (or starboard, if ship).

The system's elevation shall be positive upward.

The numerical value should be the same for all disciplines and packages.

For special structures such as jackets being built laying down, the reference system must be adjusted

to this fabrication situation, but the final as built survey shall be related to the platform grid system.

The survey reference system should be established within the following tolerances:

Sections/complete structures: ±3 mm

Stricter survey reference system tolerances shall be used on components where the requirements of

the final product are more stringent than the above tolerance. For components where the tolerance of

the product are less than ±2 mm, the proposed survey methods shall be described.

At all stages during fabrication and erection, the Contractor shall ensure that the survey reference

system and the fabricated item shall be in correct position relative to each other.

Permanent survey stations shall be properly constructed and be protected from disturbance.

The permanent survey stations shall be rechecked periodically, or whenever additional permanent

survey stations are established. All additional or rechecked surveys shall be properly documented.


Rev. 4, Nov. 2000


Fig. E.4.6-1 Principal reference system

Figure E.4.6.1, indicates sample of applicable and practical reference systems.

The layout of the reference system may be specially designed to suit the task at hand and the

methods chosen for controls.

E.4.6.2 Marking criteria’s

During layout and assembly of each structural item all work points and centrelines, which are

relevant for the remaining steps of the construction, shall be marked and identified.

Location of hidden stiffeners, bulkheads etc. shall be marked on the outside of the structure to

ensure a correct assembly, if relevant for the remaining steps of the construction.

All primary datum work points on the structure shall be set out using accepted engineering

surveying techniques consistent with the tolerances required by this annex. All girders, boxes, nodes

and other structures shall be properly and clearly marked relative to the grid system at all interfaces,

if relevant for the remaining steps of the construction.

E.4.6.3 Accuracy

Surveys shall be performed using survey techniques and technology which enables the achievement

of a survey accuracy better than the specified tolerances.

The methods and equipment used must enable verification of the survey accuracy.


Rev. 4, Nov. 2000


All activities related to measurement and inspection of dimensions and tolerances shall take into

account the effects of self weight while the structure is under fabrication.

E.4.7 Interface criteria’s

All non-adjustable interfaces and interfaces deemed critical prior to erection shall be surveyed and

documented. A comparison of the interface results prior to erection shall be performed and

necessary actions in order to meet the global requirements shall be carried out.

E.4.8 Alignment Requirement

Requirements to alignments with regard to eccentricity of butt joints and cruciform joints are as

follows:

a) Butt-joints

Reference is made to table 9.3.

b) Cruciform Joints

Eccentricity of non-continuous plating in cruciform joints shall not exceed the following

requirements, (ref. figure 4.8-1)

e ≤ t1/2 (mm), maximum 5 mm, for t2 ≤ 20 mm

e ≤ t1/2 (mm), maximum 8 mm, for t2 > 20 mm

t1 = smaller thickness in mm of non-continuous plate

t2 = thickness in mm of continuous plate

t3 = larger thickness in mm of non-continuous plate

e = 2m + t3 - t1

2

m = misalignment

e = eccentricity

Fig. E.4.8-1 Cruciform joints


Rev. 4, Nov. 2000


E.5 FABRICATION TOLERANCES FOR STRUCTURAL COMPONENTS

E.5.1 I / H- Girders

Type of deviation Figure Nota-

tion

Ref.

Length

Allow % of

ref. length

Max.

Deviation mm

Lateral or vertical

deflection

5.1-1A f L ±0.15 ±10

Length 5.1-1A L L ±0.25 ±3

Height 5.1-1B H H ±0.3 ±3

Width 5.1-1B B B ±3

Inclination of web 5.1-1B V H ±0.8 ±10

Eccentricity of web

on flange

5.1-1B V1 H ±1.0 ±3

Buckling of web 5.1-1B V3 H ±0.75 ±10

Curvature/rotation

flange

5.1-1B V2 B/2 ±2.5 ±3

Twisting of section 5.1-1C d5 L ±0.10 ±10

Fig. E.5.1-1 I-/H-Girders tolerance references


Rev. 4, Nov. 2000


E.5.2 Box Girders

Type of deviation Figure Notation Ref. Length Allow % of

ref. Length

Max Dev.

mm

Position deviation at

end/interface section

5.2-1A d1 Ref. Centre

Lines

- ±3

Length 5.1-1A L L ±0.25 ±3

Height 5.1-1B H H ±0.3 ±3

Width 5.1-1B B B ±3

Out of straightness 5.2-1B d2 L ±0.15 ±10

Buckling of plates 5.2-1C d3 H, W ±0.5 ±10

Pos. deviation of load

bearing stiffeners

inclusive inclination

5.2-1D d4 Ref. Centre

Lines

- ±5

Twisting 5.2-1E d5 H ±0,5 ±6

Fig. E.5.2-1 Box Girders tolerance references


Rev. 4, Nov. 2000


E.5.3 Tubulars

The allowable tolerance given for individual tubular segments shall not be cumulative for the

finished tubular.

a) Circumference:

The external circumference shall not depart from the nominal external circumference by more than

the following (Ref. Figure 5.3-1):

• Measured at joints or within ±610 mm from the joint (Zone A in Figure 5.3-1):

of the nominal wall thickness or ±10 mm whichever is the smallest.

• The tolerances in (i) may be increased by 50% for the remaining length of the tubular (Zone B in

Figure 5.3-1).

b) Out-of Roundness (Ovality):

Ovality is defined as the difference between the measured maximum and minimum internal (or

external) diameters and shall not be more than 1% of the nominal OD (ODn) or 8 mm, whichever is

the least. (Ref. Figure 5.3-2)

c) Out of circularity:

Circularity is defined as the difference between the actual and the average radius, both beeing

determined from the optimum centre of the tubular. Maximum difference is not to be more than

0.25% of ODn.

d) Straightness:

The maximum allowable deviation from straightness in any 3 m increment of length shall be 3 mm.

The straightness deviation over tube length (L), shall not exceed 0.001 x L, with maximum 10 mm

deviation for lengths up to 12 m. Above 12 m length max. allowable deviation is 12 mm. Out of

straightness shall be checked on two longitudinal planes separated by 90°.

e) Length:

Unless otherwise noted, the tubular shall be delivered within following tolerances:

• Unbevelled ends: La ≥ Ln +25 mm

• Bevelled ends: La = Ln ± 5 mm

f) Tube ends:

The tube ends shall be perpendicular to the longitudinal axis within the following tolerances:

• Unbevelled ends: 5 mm

• Bevelled ends: 3 mm


Rev. 4, Nov. 2000


g) Local out-of roundness:

The local out-of roundness shall not deviate from the theoretical curvature by more than e=0.002 x

ODn (ref. fig. 5.3-3). The local out-of roundness shall be measured inside or outside over 20° of the

circumference.

h) Local Out-Of Straightness:

Local straightness is defined as the deviation of the shell plate from a straight generator of length

(L) parallel to the true centre line of the tubular. This tolerance shall not exceed 20% of the wall

thickness. Local straightness shall be checked on the inside or outside of tubulars with a nominal

external diameter greater than 2000 mm or with a nominal external diameter to nominal wall

thickness ratio greater than 65. These checks shall be carried out at 45° intervals of arc with L= 3 m.

Above tubular tolerances apply to welded and not seamless tubulars.

Fig. E.5.3-1 Tubulars - Circumfential tolerance

Fig. E.5.3-2 Tubulars - Ovality tolerance


Rev. 4, Nov. 2000


Fig. E.5.3-3 Tubulars - Local out-of roundness references


Rev. 4, Nov. 2000


E.5.4 Panels

Type of deviation Figure Notation Ref. Allow. % Max. dev. mm

PANEL SHEET:

Out of plane straightness,

sagging/hogging, between

girders

5.4-1 p1 W ±0.15 ±15

Local buckles between

stiffeners 5.4-1 p2 W1 ±0,5 ±5

GIRDERS/ STIFFENERS:

Out of straightness

in X and Y direction 5.4-1 g1 W 0.15% ±10

Position deviation 5.4-1 g2 Grid

system ±10

Inclination 5.4-1 g3 Hg ±0.8 ±10

Out of straightness of web

normal to web

(web buckles) 5.4-1 g4 Hg , W1 ±0.75 ±10

Fig. E.5.4-1 Deck panels tolerance references


Rev. 4, Nov. 2000


E.5.5 Girder Nodes

Type of deviation Figure Notation Ref. length Allow % of

ref. length

Max. deviation

mm

Position deviation of

interfaces

5.5-1B,

5.5-1C

d1 Ref. Centre

Line

- ±5

Lateral and vertical

straightness of node

5.5-1A f L ±0.15 ±5

Lateral and vertical

straightness of stiffeners

5.5-1A f1 L,H ±0.1 ±5

Height of node 5.5-1B s - - ±5

Pos. deviation stiffeners

inclusive inclination

5.5-1B,

5.5-1C

d2 Ref. Centre

Line

- ±5

Position deviation

column interfaces

5.5-1C d3 Ref.Centre

Line

- ±5

Baseplate flatness

/rotation rel.to Z axis

5.5-1A,

5.5-1B

b1 Ref. Centre

Line

- ±2

Pos.deviation baseplate

relative to Z axis

5.5-1B d4 Ref.Centre

Line

- ±3

Fig. E.5.5-1 Girder nodes tolerance references


Rev. 4, Nov. 2000


Fig. E.5.5-1 Girder nodes tolerances


Rev. 4, Nov. 2000


E.5.6 Box Nodes

Type of deviation Figure Notation Ref. Length Allow of

ref. length

Max. deviation

mm

Position deviation of main box

interface

5.6-1A d1 Ref. Centre

Line

- ±3

Out of straightness 5.6-1B d2 L ± 0,10% ±10

Buckling of plates 5.6-1C d3 H, W ±0,5% ±10

Radial and tangential stub end

deviation

5.6-1C,

5.6-1E

d4 Ref. Centre

Line

- ±5

Pos. deviation of load bearing

stiffeners incl. inclination

5.6-1D d5 Ref. Centre

line

- ±5

Offset of centrelines at centre

of node

5.6-1E,

5.6-1F

d6 Ref. Centre

Line

- ±5

Fig. E.5.6.1 Box nodes tolerance references


Rev. 4, Nov. 2000


E.5.7 Tubular Nodes

Type of deviation Figure Notation Ref. length Allow of

ref. length

Max.

deviation

mm

Overlength of stub 5.7-1A l2 L2 +25

-0

Overlength of node can barrel 5.7-1A l1 L1 +10

-0

Stub ends perpendicularity 5.7-1A p - ±3

Radial and tangential stub end/

node cans position

5.7-2 V ∆α Grid

system0.2° of arc ±6

Position of intersection point

node can / stub

5.7-2 E Grid

system±6

Internal stiffeners

-Position

-Inclination of web

-Flange width

-Bow of web

-Rotation of flange

-Eccentricity of flange

on web

-Height of stiffeners

5.7-1A

5.7-1B

5.7-1B

5.7-1C

5.7-1B

5.7-1B

5.7-1B

P

M

B

N

Lx

h

b

1,0%

1,5%

1,0%

±5

±5

±3

±6

±6

±6

+10/-3

Local straightness of

stubs/barrel

5.7-1A Wall

thickness

25% 8

Straightness of barrel 5.7-1A L 1/1200 10

The centre line of stub shall be within 0.2° from the stub angle specified on the design drawings.

Maximum position deviation measured at the intersection of stub end / node can shall be ±6 mm.

For stubs longer than 1 stub diameter, the position deviation between can and stub may be taken at

the 1 diameter location.

Tolerance for:

• Circumference

• Out-of Roundness (Ovality)

• Local out-of roundness

• Out-of circularity

are defined in Section E.5.3


Rev. 4, Nov. 2000


Fig. A

Fig. B (tolerance references)

Fig. C (tolerance references - internal stiffeners)

Fig. E.5.7-1 Tubular nodes


Rev. 4, Nov. 2000


Fig. E.5.7-2 Node stub location

E.5.8 Cast and Forged Elements

All relevant tolerances regarding these elements’ geometry i.e. hole positions, flatness, web and rib

positions shall be specified on the design drawings.

The nominal axes, work points, rib centrelines etc. shall be properly marked on each element

interface(s) to adjacent main steel.


Rev. 4, Nov. 2000


During installation of cast and forged items, special care shall be taken that the parent plate edges

are located within prepared face of casting / forging.

See also ISO-8062 standard for tolerances.

E.5.9 Curved and cylindrical shell

For elements including curved shells (such as semi submersible’s pontoons) special dimensional

procedures shall be implemented for measurement and computing.

Sylindrical shells.

The maximum deviation from the nominal radius, measured at ringstiffeners or at bulkheads shall

not exceed the value:

δ = | ra - r| <= 0,005 r

ra = actual distance from the cylinder axis to the shell wall

r = nominal radius of the shell

Components defined as Cylindrical Shell to be specified on design drawings.

E.5.10 Conical transitions

At both ends of a cone, the maximum deviation from the nominal radius shall not exceed the value:

δ=| ra - r| <= 0,005 r

where ra= Actual distance from the cylinder axis to the cone wall

r = Nominal radius at cone end

Requirements for internal stiffeners shall be in accordance with table 5.7.


Rev. 4, Nov. 2000


E.6 ASSEMBLY TOLERANCES

E.6.1 Topsides and modules

Type of deviation Figure Notation Ref. Allowable

% of ref.

length

Max.

deviation

mm

Position of any point of main

steel

6.1-1 X1,Y1 Grid system ±10

Position of support node 2) 6.1-1 X2, Y2,

Z2

Grid system ±6

Position of lifting node 6.1-1 X2, Y2,

Z2

Grid system ±10

Elevation of decks and mezz.

decks sag./hog.

6.1-1 H1, H2,

H3

Grid system ±10

Footings deviation from

elevation reference 1)

6.1-1 H Grid system ±5

For truss frames without any defined support points the elevation reference should be based on a

mean of all levelled points on main steel.

NOTES:

1) Maximum allowable deviation shall also apply to mating surface level at stab-in onto

jacket legs.

2) Includes Main Support Frame (MSF) stab-in nodes and module footing nodes.

Fig. E.6.1-1 Topside and module tolerance references


Rev. 4, Nov. 2000


E.6.2 Jacket and other tubular frame structures

E.6.2.1 Assembly tolerances

Type of deviation Figure Notation Ref. Max. dev. mm

Position deviation

of centre of nodes 6.2.1-A∆x, ∆y Grid system ±12

Rotation of node 6.2.1-A S ±6

Distance deviation

between two nodes

6.2.1-A ±20

Diagonal distance

between coloumn

in each hor. plane

12

Position of leg

ring stiffeners and

diaphragms ±6

Inclination of

ringstiffeners 6

Straightness of

legs / chords 6.2.1-B/C ∆f L X±10

Straightness of

braces 6.2.1-C ∆f L X±L/1000

Position of

intersecting braces Grid system ±15

NOTE: Local tolerances for sliding and pivoting ends shall be specified on the structural drawings.


Rev. 4, Nov. 2000


Fig. E.6.2-1 Jacket and tubular frame structures - assembly tolerances


Rev. 4, Nov. 2000


E.6.2.2 Final Tolerances for Jacket, Interface Jacket/MSF

Type of deviation Figure Notation Reference Max. dev.

mm

Horizontal position

deviation of centre of

stab-in cans

6.2.2 Vx, Vy

V =

√ (Vx²+Vy²)

Grid system

1)±6

±8

Jacket:

Distance between centre

of column to centre of

any column at stab-in

cans

6.2.2 F L ±12

Jacket:

Mating surface level at

stab-in

Grid system

2)

±3

MSF:

Distance between centre

of column to centre of

any column at stab-in

cans

6.2.2 F L ±6

Ovality of stab-in can As in section

E.5.3b

Horizontal position

deviation of caissons,

risers, J-tube

Grid system ±6

NOTES:

1) The position of the stab-in cans shall, if the situation allowes, be related to the top-

side stab-in cones with the tolerances stated above.

2) The jacket legs shall by preference be cut within above tolerances after grout is cured.

If survey of the deck footings show out-of acceptable elevation/flatness tolerances, ref. Section

E.6.1, the measured deviations shall be considered incorporated when cutting the legs in order to

minimise loads due to differential settlements in footings.


Rev. 4, Nov. 2000


Fig. E.6.2-2 Final tolerance jacket interface jacket/MSF

E.6.2.3 Guides, Sleeves, Piles and clamps

The position deviation of the centre of pile guides/sleeves shall be ±25 mm related to the

coordinate system.

Local alignment of sleeves 20 mm.

Radius of spacer plates ±5 mm.


Rev. 4, Nov. 2000


E.6.2.4 Piles

Type of deviation Figure Notation Ref. Max. dev.

mm.

Length ±100

Diameter between

spacerplates

6.2.4 d1 As specified on

drawing

Diameter in driving

head

6.2.4 d2 As specified on

drawing

End perpendicularity

in driving head

6.2.4 P As specified on

drawing

Pile markings ±50

For general tolerances, see E.5.3 Tubulars.

Fig. E.6.2-4 Piles tolerance references

E.6.2.5 Conductor Guides

The position deviation of the centre of the conductor guides shall be ±10 mm related to the

coordinate system for top el. and ±15 mm for the other elevations related to the same coordinate

system.

The maximum deviation of any conductor guide from the optimised centreline through all conductor

guides, shall not vary more than ±15 mm.


Rev. 4, Nov. 2000


E.6.2.6 Appurtenances

Caissons, J-tubes and risers.

Type of deviation Figure Notation Ref. Max.dev. mm

Length - - - ±25

E.6.3 Floating production units

E.6.3.1 Semi submersibles and tension leg platforms

Overall hull / substructure tolerances:

Type of deviation Figure Ref. Max. dev. mm

Global position of column top /

bottom

6.3.1-1

6.3.1-2

Global

grid system ±15

Distance between top / bottom

of two columns

6.3.1-1

6.3.1-2±30

Local position of column top /

bottom 6.3.1-3

Local

grid system ±5

Fig. E.6.3.1-1 Semi submerisibles / tension leg platforms. Global tolerance


Rev. 4, Nov. 2000


Fig. E.6.3.1-2 Semi submerisibles / tension leg platforms. Global tolerance

Fig. E.6.3.1-3 Semi submerisibles / tension leg platforms. Local tolerance

E.6.3.2 Ship

Ships should be fabricated using a grid system with origo in the aft perpendicular, and in accordance

with section E.3 of this annex. Based on the grid system a reference system according to section

E.4.6.1 should be permanently marked onboard the ship.

E.6.4 Subsea structures

Subsea structures should be fabricated according to tolerances given on drawings.


Rev. 4, Nov. 2000


E.7 FABRICATION TOLERANCES FOR SPECIAL ITEMS

E.7.1 Crane Pedestal

Crane pedestal tolerances shall be specified in a separate document to be prepared by the designer,

taking into account the structural aspects as well as the mechanical functional tolerances and

equipment interface tolerances.

E.7.2 Skid Beams

Skid beam tolerances shall be specified in a separate document to be prepared by the designer,

taking into account the structural aspects as well as the mechanical functional tolerances and

equipment interface tolerances.

E.7.3 Outfitting Structure

• This section covers all primary and secondary outfitting structures.

• The difference in elevation of deck plates and/or grating at joints shall not exceed 2 mm.

• Plates and gratings shall be without visible warping.

• Landing and stairway locations shall not deviate more than 25 mm from the dimensions shown

on the AFC drawings.

• Fabrication of handrails shall be performed to such a degree of accuracy that when erected, the

toprail shall be continuous, straight, have smooth transitions and be level to the eye.

• Members in the vertical plane shall not be out of plumb by more than 6 mm on each 3000 mm

section and not more than 26 mm over the total height of the structure.

• Wherever tolerances are not shown on the drawings, or specified elsewhere, fabrication work

shall be accurate to within 10 mm of all nominal dimensions.

• Matching holes for bolted connections shall not exceed 2 mm difference in location.

E.7.4 Installation Aids

Installation aid structures such as primary and secondary guides and bumpers shall be fabricated and

installed in accordance with acceptable tolerances for relevant elements/structures defined in this

document.

Specific tolerance requirements are shown on respective drawings, and shall be mandatory.

E.7.5 Grillages

Load out grillage, barge grillage and seafastening shall be fabricated and installed in accordance

with acceptable tolerances for relevant structures/elements defined in this document.

(Ref. section E.4.8)

Specific tolerance requirements shall be shown on respective drawings and shall be mandatory.

E.7.6 Cranes

Reference standard: ENV 1090-1 applies.

Norsok M101 Structural Steel Fabrication

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