DNV-OS-E303: Certification of Fibre Ropes for Offshore Mooring · PDF file'Certification of...

OFFSHORE STANDARD

DET NORSKE VERITAS

DNV-OS-E303

CERTIFICATION OF FIBRE ROPES FOR OFFSHORE MOORING

APRIL 2008

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

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

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

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

Amendments and Corrections This document is valid until superseded by a new revision. Minor amendments and corrections will be published in a separatedocument normally updated twice per year (April and October). For a complete listing of the changes, see the “Amendments and Corrections” document located at: http://webshop.dnv.com/global/, under category “Offshore Codes”.The electronic web-versions of the DNV Offshore Codes will be regularly updated to include these amendments and corrections.

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Offshore Standard DNV-OS-E303, April 2008Changes –

Main changesThis standard is an update of the DNV service documents for:'Certification of fibre ropes for offshore mooring' in order toaccommodate experience that has been gained since 1999. The following document is replaced by this standard:"Standard for Certification 2.13 (Jan.1999) - Certification ofOffshore Mooring Fibre Ropes".There are no changes to main certification requirements com-pared to the previous standard.

— On specific conditions the following may now be permitted:

— Sea-bed contact for fibre-rope assemblies that are notdynamically loaded.

— Service without inserts in permanent mooring sys-tems.

— The testing of product rope is now split between subropesand full ropes. Subropes should be used for change-in-length measurements due to the higher accuracy. In addi-

tion, a splice integrity test for subrope has been intro-duced. This aspect was previously only taken into accountby the fatigue test on fibre-rope assembly.

— The following documents will no longer be issued as partof fibre-rope assembly certification:

— Certificate of Compliance— DVR for mooring analysis— Inspection Release Note.

— The DVR for the mooring analysis will be issued sepa-rately to the user for verification based on DNV-OS-E301,Position Mooring.

— Description of fibre-rope change-in-length performancehas been harmonised with the ongoing work for the revi-sion of API-RP2SM "Recommended Practice for Design,Manufacture, Installation, and Maintenance of SyntheticFibre Ropes for Offshore Mooring".

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Offshore Standard DNV-OS-E303, April 2008 – Changes

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Offshore Standard DNV-OS-E303, April 2008 Contents –

CONTENTS

CH. 1 INTRODUCTION ................................................ 7

Sec. 1 General................................................................... 9

A. General....................................................................................9A 100 Introduction....................................................................... 9A 200 Important notice................................................................ 9A 300 Scope................................................................................. 9A 400 Objective........................................................................... 9A 500 Application........................................................................ 9

B. References ............................................................................10B 100 General............................................................................ 10B 200 Normative References..................................................... 10B 300 Informative references .................................................... 10

C. Definitions ............................................................................11C 100 Verbal forms ................................................................... 11C 200 Terms .............................................................................. 11C 300 Symbols .......................................................................... 11

CH. 2 TECHNICAL PROVISIONS ............................ 13

Sec. 1 General................................................................. 15

A. Introduction ..........................................................................15A 100 Objective......................................................................... 15

B. Marking ................................................................................15B 100 General............................................................................ 15B 200 Rotation Marker.............................................................. 15

C. In-service condition assessment ...........................................15C 100 ........................................................................................ 15

Sec. 2 Design Assessment ............................................. 16

A. Documentation......................................................................16A 100 General............................................................................ 16A 200 Documentation from the user ......................................... 16A 300 Documentation from the rope manufacturer................... 16A 400 Quality system ................................................................ 16A 500 Sub-contractors ............................................................... 16A 600 Manufacturing specification ........................................... 16

Sec. 3 Materials .............................................................. 18

A. Fibre ropes ............................................................................18A 100 Load-bearing yarn........................................................... 18A 200 Sheathing ........................................................................ 18

B. Terminations.........................................................................18B 100 Protection cloth for spliced eyes..................................... 18B 200 Termination hardware..................................................... 18

C. Mechanical properties...........................................................18C 100 Minimum Breaking Strength – (MBS) ........................... 18C 200 Change-in-length performance ....................................... 18C 300 Calculation of stiffness ................................................... 19C 400 Post-Installation Stiffness ............................................... 19C 500 Dynamic Stiffness .......................................................... 19C 600 Static Stiffness ................................................................ 20C 700 Splice integrity................................................................ 20C 800 Fatigue performance ....................................................... 20C 900 Torque and rotation characteristics................................. 20C 1000 Resistance to soil ingress ................................................ 21C 1100 Weight pr. Unit Length (W/L)........................................ 21C 1200 Maximum temperature due to Hysteresis Heating ......... 21

Sec. 4 Measuring and Expressing Rope Change-in-Length Properties ................... 22

A. General..................................................................................22A 100 Introduction..................................................................... 22A 200 Stretch and Strain............................................................ 22A 300 Spring Rate and Stiffness................................................ 22

Sec. 5 Specification of Testing ...................................... 23

A. General..................................................................................23A 100 General............................................................................ 23A 200 Data recording and measurement accuracy .................... 23

B. Testing of Yarn .....................................................................23B 100 General............................................................................ 23

C. Testing of subrope ................................................................23C 100 General............................................................................ 23C 200 Number and selection of subrope test specimens. .......... 23

D. Testing of Fibre Rope and Fibre-Rope Assembly ................23D 100 Number and selection of fibre-rope test specimens........ 23

E. Test methods.........................................................................24E 100 Introduction..................................................................... 24E 200 Testing of change-in-length performance on

subropes .......................................................................... 24E 300 Testing of breaking strength on fibre-rope assembly or

subrope............................................................................ 24E 400 Testing of splice integrity on subropes........................... 24E 500 Fatigue ............................................................................ 25E 600 Testing of Weight/Unit Length....................................... 25E 700 Soil ingress resistance..................................................... 25E 800 Testing of maximum temperature due to Hysteresis

Heating............................................................................ 25

F. Termination hardware...........................................................25F 100 Non-destructive testing................................................... 25F 200 Mechanical testing .......................................................... 25F 300 Fibre-rope assembly........................................................ 25

CH. 3 CLASSIFICATION AND CERTIFICATION 27

Sec. 1 Classification and Certification......................... 29

A. Classification ........................................................................29A 100 General............................................................................ 29

B. Certification of mooring analysis .........................................29B 100 General............................................................................ 29

C. Certification of Fibre-Rope Assemblies ...............................29C 100 Introduction .................................................................... 29C 200 Main elements in certification ........................................ 29C 300 Additional qualification activities................................... 29C 400 Deviations and test waivers ............................................ 29

Sec. 2 Work process ...................................................... 30

A. General..................................................................................30A 100 Introduction..................................................................... 30A 200 Request for certification ................................................. 30A 300 Pre-production Meeting .................................................. 30

B. QA/QC Review.....................................................................30B 100 General............................................................................ 30B 200 Quality Review Report ................................................... 30B 300 Design assessment .......................................................... 30

C. Testing ..................................................................................30C 100 General............................................................................ 30C 200 New techniques (under development) ............................ 31

D. Start up of production ...........................................................31D 100 General............................................................................ 31

E. Survey during production and testing...................................31E 100 The survey comprises the following main elements....... 31

F. Documents issued or attested by DNV.................................31F 100 General............................................................................ 31

G. Certificates............................................................................31G 100 Introduction..................................................................... 31

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Offshore Standard DNV-OS-E303, April 2008 – Contents

G 200 Certificates for Load-Bearing Yarns...............................32G 300 Fibre-Rope Assemblies ...................................................32

App. A Fibre-rope Stretch and Stiffness ....................... 33

A. Background........................................................................... 33A 100 Basic Rope Change-in-Length Properties.......................33A 200 Mooring Line Change-in-Length Properties...................33A 300 Original Spring Rate and Construction Stretch...............33

A 400 Static Spring Rate and Continued Original Spring Rate.33A 500 Polymer Stretch...............................................................34A 600 Sustained Elastic Stretch and Dynamic Spring Rate ......34

App. B Quality Review Report ...................................... 35

App. C Example of Certificate Format ......................... 37

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OFFSHORE STANDARDDNV-OS-E303

CERTIFICATION OF FIBRE ROPES FOROFFSHORE MOORING

CHAPTER 1

INTRODUCTION

CONTENTS PAGE

Sec. 1 General ....................................................................................................................................... 9

DET NORSKE VERITASVeritasveien 1, NO-1322 Høvik, Norway Tel.: +47 67 57 99 00 Fax: +47 67 57 99 11

Offshore Standard DNV-OS-E303, April 2008Ch.1 Sec.1 –

SECTION 1GENERAL

A. General

A 100 Introduction101 This Standard covers certification of fibre-rope productsfor offshore mooring.102 Chapter 1 (this chapter) provides a general introductionwith overview, definitions, general provisions and referencesrelevant for Chapter 2 and Chapter 3. Chapter 2 provides thetechnical provisions of this standard. Chapter 3 covers theprocess of certification.

A 200 Important notice201 Apparent compliance to the provisions of this standarddoes not imply that a product is certified; nor does apparentnon-compliance to certain provisions imply that a product can-not be certified. Certification is a matter of judgement based onthe complete set of provisions that are given in this standard.

A 300 Scope301 This standard specifies the requirements for the materi-als, design, manufacture and testing of offshore mooring fibreropes, which are subjected to classification or certification. Itmay also serve as a technical reference document in contrac-tual matters between user and manufacturer.302 This standard is applicable for fibre ropes used as tautmooring lines on column-stabilised units, ship-shaped units,loading buoys, deep draught floaters, and other floating bodies.

Guidance note:This standard may also be used for semi-taut and catenary moor-ing systems where only a portion contains fibre-rope segments.It does not apply to hawsers used to moor tankers to loading oroff loading buoys.

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

303 Typical applications are long-term mooring of floatingproduction systems and mooring of mobile offshore units. Italso applies to fibre-rope mooring lines for other offshoreinstallations, such as wave-, wind- or current energy plants.304 Provided appropriate qualification of the resistance tosoil ingress is carried out based on DNV-RP-A203, sea-bedcontact in the installation phase (or pre installation to the seabed) can be permissible under this standard.305 Provided appropriate qualification is carried out basedon DNV-RP-A203, a permanent mooring system can beinstalled without inserts for in-service examinations and test-ing.

A 400 Objective401 The objective of this standard is to ensure uniform qual-ity level of fibre ropes manufactured for offshore applications.

A 500 Application501 This standard is applicable to fibre ropes that are manu-factured using polyester-yarn materials.502 Fibre-rope segments of mooring lines can be of variousconstructions. Some examples of different types of rope con-

structions are shown in Figure 1.503 At the time of this standard, the most commonly usedtype of fibre rope for offshore moorings consists of parallelsubropes held together by a braided jacket. The subropes con-sist of strands in helical (laid) or braided arrangement. The hel-ical subropes typically use three or four strands, whereas thebraided subropes typically use eight or twelve strands. The sizeand number of subropes to make up the fibre rope variesbetween manufacturers. Rope constructions resembling steel-wire rope are also used, either as subropes or as the fibre rope.504 Fibre ropes shall be terminated with spliced eyes.505 The spliced eyes should be fitted on steel thimbles.Thimbles act as the interface between the rope eye and the con-necting (shackle or H-link) pin. The thimble should be a neatfit on the pin and the root diameter should be specified.506 If the fibre-rope segment is connected directly to an H-link, then the H-link (with pin) is considered ‘terminationhardware’ and subject to certification under this standard.

Guidance note:For other types of fibre-rope terminations than the spliced eye,none exist at the time of this standard with an appropriate levelof qualification as defined in DNV-RP-A203. The same appliesto other materials for termination hardware than steel.The fibre-rope assembly includes fibre rope with spliced eyesand termination hardware. If thimbles are used in the splicedeyes, then the connecting shackles (or H-links) are outside thescope of this standard and should be certified separately accord-ing to DNV-OS-E302. If the H-link is used without a thimble inthe eyes then the H-link terminates the fibre-rope segment andshall thus be certified as part of the fibre-rope assembly.


507 The entire length of rope shall be submerged at all timesduring service.508 Fibre-rope segments in mooring lines are normally pro-tected by an outer sheathing. A soil filter is usually incorpo-rated in this sheathing.509 The sheathing shall be sufficiently dense to avoid sun-light to penetrate when in service in order to prohibit marinegrowth inside the rope.510 Unless the protection against soil ingress has been dulyqualified, fibre-rope assemblies shall not contact the sea bedduring installation.511 Provided the protection against soil ingress has beenduly qualified, fibre-rope assemblies may be placed on the seabed pending retrieval and final hook up.512 The lower parts of the fibre rope shall not be in contactwith the sea bed during service, nor be handled or left in serv-ice in water with emulsified particles that may be transportedinto the load-bearing rope by the water that seeps in and outduring loading.

Guidance note:The filter serves as protection for unloaded rope. The protectionin the termination areas shall be qualified.


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Offshore Standard DNV-OS-E303, April 2008 – Ch.1 Sec.1

(A) Parallel-Subrope Rope.

(B) Six-Strand Rope.

(C) Thirty-Six-Strand Rope.Figure 1 Overview of types of rope

513 Fibre ropes are usually torque neutral, i.e. the rope doesnot exert torque when loaded. When it is desired that the fibrerope resists rotation of the connection to a steel-wire rope, a“torque-matched” rope is usually used.Torque matching implies that the torque/rotation exerted bythe fibre rope matches the steel-wire rope such that spinning isavoided.

Guidance note:It may be desirable that the fibre rope resist spinning in order tomaintain the fatigue life of the wire-rope.


514 The user may specify the type and dimensions of termi-nation hardware, and quality and strength of the materialsused. If not, the manufacturer should propose the type andquality, suitable for the intended service.515 The eye size is usually determined as the dimensionfrom the inside back of the eye to the crotch of the eye with twolegs of the eye close together. The tolerance should be - 0% /+ 20% of the dimension stated by the manufacturer if this is not

given. The profile of the spool should also be specified.

Figure 2 Illustration of spliced-eye termination with spool thimble.

The D/d ratio range and eye angle are given as illustration. Theactual design is part of the rope design as determined by themanufacturer.

B. ReferencesB 100 General101 In case of conflict between requirements of this standardand a reference document, the requirements of this standardshall prevail.102 The latest edition of the referenced document (includingamendments) should apply.

B 200 Normative References201 The referenced documents listed in Tables B1 throughB3 include provisions, which through reference in the text con-stitute provisions of this standard.

Guidance note:DNV-OS-E302 and DNV-OS-E304 are due to be issued. Untilissued, Certification Notes No. 2.6 and Certification Notes No.2.5 are applicable.


B 300 Informative references301 The referenced documents listed in Tables B4 throughB6 include information that may be useful to the users of thisstandard.

Table B1 DNV Offshore StandardsReference TitleDNV-OS-E301 Position Mooring.DNV-OS-E302 Certification of Offshore Mooring Chain.DNV-OS-E304 Certification of Offshore Mooring Steel Wire

Ropes.

Table B2 DNV Recommended PracticeReference TitleDNV-RP-A203 Qualification Procedures for New Technology.

Table B3 Other ReferenceReference TitleCI 1503 Test Method for Yarn-on-Yarn Abrasion.

Table B4 DNV Offshore StandardsReference TitleDNV-OS-C401 Fabrication and Testing of Offshore Structures.DNV-OS-C501 Composite Components.

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C. Definitions

C 100 Verbal forms101 Shall: Indicates a mandatory requirement to be followedfor fulfilment or compliance with the present standard. Devia-tions are not permitted unless formally and rigorously justified,and accepted by all parties.102 Should: Indicates a recommendation that a certaincourse of action is preferred or particularly suitable. Alterna-tive courses of action are allowable under the standard whenagreed between contracting parties, but shall be justified, doc-umented and approved by DNV.103 May: Indicates permission, or an opinion, which is per-mitted as a part of conformance with the standard.104 Can: Indicates a conditional possibility.

C 200 Terms201 MBS: Minimum breaking strength. The specified mini-mum force that shall be achieved in the break testing. TheMBS is a requirement, i.e. not a property of the fibre-ropeassembly.202 AVS: Average strength, as determined by the average offive break tests.203 Change-in-length performance: The stretch and cyclicstiffness of the fibre rope as function of loading sequence andtime.204 Stretch: The change in rope length under tension. It isdenoted ‘ΔL’ and has the dimension of length..205 Strain: The non-dimensional expression of stretch; theratio of stretch to the original length before applying tension. Itis denoted ‘ε’.206 Stiffness: The ratio of change in force to change in strain.When normalised with the average strength it is dimensionless.207 Static Stiffness: Ratio of change in force to change inlength when tension is either increased or reduced.208 Post-installation stiffness: Resulting static stiffness thatmay be used in analysis for the case where the maximumdesign storm occurs immediately after installation.

209 Dynamic stiffness: Maximum stiffness of the mooringlines, which applies when the mooring system is subject to thecyclic loading of a maximum design storm.210 Fibre rope: The full-size rope without splices, consti-tuted by all subropes and sheathing.211 Sheathing: Protective jacket and soil barrier.212 Fibre-rope segment: Finished fibre rope with splicedterminations, and splice-area protection.213 Fibre-rope assembly: Fibre-rope segment with desig-nated termination hardware.214 Termination hardware: The steel component inserted inthe rope eye to transfer the line loads from the fibre-rope seg-ment to the rest of the mooring line. The spool thimble is mostcommonly used.215 In-service condition assessment scheme: Inspectionplan and activities performed regularly during the service lifein order to control the condition of the mooring system.216 User: The company that buys the fibre-rope assembliesfrom the manufacturer.217 Mooring line: The entire line that transfers tensionbetween the floating unit and the anchor.218 MODU (mooring) system: Mooring system utilised bymobile units such as Mobile Offshore Drilling Units; charac-terised by intermittent use of the mooring lines that allowshands-on inspection at limited time intervals.219 Permanent (mooring) system: Mooring system that isinstalled for a design life of five years or more.220 I&T P: Inspection and test plan, which is a plan for thevarious steps in making the fibre-rope assemblies, describingthe involvement of QA department and external surveyor.221 I&T P sheet: A one-page sheet reflecting important sur-vey steps and which particular steps have been carried out fora particular fibre-rope assembly.

C 300 Symbols

SINST The post-installation stiffness is defined asthe resulting static stiffness from the com-pleted retraction at installed tension up to thepeak storm cycle after sustained elasticstretch.

SSTATIC The Static Stiffness is defined as the stiffnessof the mooring line in periods of moderatewave loading, after initial constructionstretch has been taken out.

SDYN The Dynamic Stiffness is defined as themaximum stiffness of the mooring linewhich is predicted when the mooring systemis subject to the cyclic loading of a maximumdesign storm.

TMIN Minimum tension in the fibre rope during astorm with 100-year return period.

TMEAN+LF Tension caused by static forces generated bywind, current and wave drift forces; and ten-sion caused by low frequency motions gen-erated by wind and waves in a storm with areturn period of 100 years.

TMEAN+LF+WF Tension caused by static forces generated bywind, current and wave drift forces, includ-ing tension caused by low frequencymotions generated by wind and waves; andtension generated by wave frequency motionin a storm with a return period of 100 years.

W/L Weight per unit length.

Table B5 DNV Offshore Service SpecificationsReference TitleDNV-OSS-101 Rules for Classification of Offshore Drilling and

Support Units.DNV-OSS-102 Rules for Classification of Floating Production

and Storage Units.DNV-OSS-401 Technology Qualification Management.

Table B6 Other ReferencesReference TitleAPI RP 2SK Design and Analysis of station-keeping systems

for Floating Structures.API-RP2SM Recommended Practice for Design, Manufacture,

Installation, and Maintenance of Synthetic Fibre Ropes for Offshore Mooring.

ASTM D 6611 – 00

Standard Test Method for Wet and Dry Yarn-on-Yarn Abrasion Resistance.

CI 1500-02 Test methods for fibre rope.ISO 18692 Fibre ropes for offshore station-keeping – Polyes-

ter.OCIMF Guidelines for Purchasing and Testing of SPM

Hawsers.

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CHAPTER 2

TECHNICAL PROVISIONS

CONTENTS PAGE

Sec. 1 General ..................................................................................................................................... 15Sec. 2 Design Assessment .................................................................................................................. 16Sec. 3 Materials................................................................................................................................... 18Sec. 4 Measuring and Expressing Rope Change-in-Length Properties .............................................. 22Sec. 5 Specification of Testing ........................................................................................................... 23



SECTION 1GENERAL

A. IntroductionA 100 Objective101 This section describes documentation requirements andtechnical requirements to polyester fibre ropes applied in posi-tion mooring.

B. MarkingB 100 General101 Each fibre-rope assembly should be marked at each endwith a unique identifier traceable to appropriate certification.

B 200 Rotation Marker201 All fibre-rope segments shall include a conspicuouslength-ways marker in order that any undue rotation in instal-

lation or in early operation can be observed by ROV inspec-tion. An alternative would be for at least two strands in thebraided jacket, one left hand, and one right hand to be madefrom durable, water-resistant-coloured yarns.

C. In-service condition assessment

C 100101 At present, the industry relies on scheduled retrieval ofinserts for inspection and testing for condition assessment. It isa requirement of this standard that the condition of the fibre-rope assemblies be controlled during service.102 The methods and techniques for controlling the condi-tion of the fibre-rope assemblies during service shall bedescribed in the in-service condition assessment scheme.

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SECTION 2DESIGN ASSESSMENT

A. Documentation

A 100 General101 This section covers documentation requirements.102 The design verification aims at confirming that the fibre-rope construction and termination design satisfies the specifieddesign conditions, codes and standards.103 The work consists of review of specifications, drawings,calculations, test reports and other data supplied by the userand the manufacturer documenting the strength and servicea-bility of the actual fibre rope segment with termination hard-ware. An overview of the required documentation is listed inTables A1 and A2.104 A design verification carried out on a fibre-rope assem-bly is only valid for that specific fibre-rope assembly.105 For permanent moorings, the design verification is onlyvalid for the designated location.

A 200 Documentation from the user201 This section provides the requirements to documenta-tion from the user. A summary of required documentation isfound in Table A1.

A 300 Documentation from the rope manufacturer301 This section provides the requirements to documenta-tion from the manufacturer for the purpose of certification ofthe fibre-rope assemblies.302 If any of the components in the mooring line are nottorque neutral, then an analysis showing that the componentsare torque matched shall be submitted.

Guidance note:Mixing torque-generating steel-wire rope with torque neutralfibre rope is mainly a concern for the fatigue life of the steel-wirerope.


A 400 Quality system401 Fibre-rope manufacturers should have a quality systemin operation.

A 500 Sub-contractors501 Main sub-contractors should operate a quality systemthat is formally accepted by the fibre-rope manufacturer.

A 600 Manufacturing specification601 The manufacturing specification shall give completemanufacturing instructions for each step in the productionprocess.

Guidance note:Information may be found in OCIMF Guidelines for Purchasingand Testing of SPM Hawsers, section D-2.3.


602 The rope manufacturer shall completely document allsplicing procedures. The same splicing procedures shall be fol-lowed when splicing the test specimens as for the delivery.

Guidance note:Information may be found in OCIMF Guidelines for the Purchas-ing and Testing of SPM Hawsers, Section D-8.


A summary of documentation requirements are given in Table A2:

Table A1 Documentation requirements - End UserUser specification:In-service inspection scheme.

Use of inserts.Mooring-system lay out and type of service.1) Type of installation, (Mobile offshore unit, e.g. drilling unit;

Floating production and/or storage unit, e.g. ship, semi-sub-mersible and spar).

2) Drawings of complete mooring systems, incl. number of anchors, number and length of fibre ropes, line configuration, etc.

3) Minimum line tension TMIN.4) Pretension for the installed mooring system.5) Line tension, which is the sum of mean and maximum

(extreme) low-frequency tension TMEAN+LF. Mean tension is the sum of pretension and tension caused by the static wind, current and wave drift loads.

6) Maximum line tension TMEAN+LF+WF.7) Design life.8) Minimum bending diameter during transport and installation.9) Installation test load for anchors if the fibre-rope assembly is

used for installation of the anchor.10) Torque and rotation characteristics of connecting wire rope.11) Highest and lowest occurring sea-water temperature.12) Evaluation of sea-bed particles (e.g. sand and mud) experienced

by the fibre-rope assembly during installation.13) Marine growth assessment report for the location of permanent

systems.

Table A2 Documentation requirement - Rope Manufacturer

Procedure for handling and installation.Manufacturing specification describing how the rope is manufac-tured including manufacturing specification for splices.Rope specification:1) Type of fibre rope construction2) Type of termination3) Weight pr. Unit Length of fibre rope4) Minimum Breaking Load5) Post-Installation Stiffness6) Static Stiffness7) Storm Stiffness8) Residual Performance - Intermediate9) Residual Strength - End of fatigue life10) Total Elongation of Fibre Rope Segments.

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Testing specification:

1) Weight pr. Unit Length of fibre rope2) Minimum Breaking Load3) Post-Installation Stiffness4) Static Stiffness5) Storm Stiffness6) Fatigue test7) Filter test8) Any requirements pertaining to qualification for special serv-

ice.Test reportsQuality plan for rope manufacturing.Specification of load bearing yarns.Load bearing yarn properties, manufacturer’s doc.Load bearing yarn properties, verification of yarn supply.Documentation of material for the fibre rope sheathing, consisting of filter and jacket.— Manufacturer and manufacturing plant— Designation— Sheathing weight/thickness— Permeability— UV resistance— Hydrolysis resistance— Resistance to chemicals.Materials for spliced-eye protection.Documentation of the termination hardware material, production and repair methods.Documentation of the termination hardware’s structural strength.Description of rope manufacturer’s quality system.Rope manufacturer’s approval of sub contractors’ quality system.

Table A2 Documentation requirement - Rope Manufacturer (Continued)

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SECTION 3MATERIALS

A. Fibre ropes

A 100 Load-bearing yarn101 The rope manufacturer should specify the following forthe yarn to be used in the construction of the load-bearing partof the rope:

— Manufacturer and manufacturing plant— Yarn designation— Yarn weight per unit length— Yarn breaking strength— Wet yarn-on-yarn abrasive performance— Marine finish designation.

102 The linear density of yarns should be stated in dtex,which is grams per 10 000 metres.

A 200 Sheathing201 The sheathing consists of the following:

— The rope jacket— The soil-ingress protection, if applicable.

202 The manufacturer, manufacturing plant, and designationof yarns and fabric shall be identified. The sheathing weight orthickness shall be stated.203 The permeability of the sheathing with respect to waterand solids shall be stated.204 The effect of UV light, of intensity corresponding to thatexperienced during operation, and after a time correspondingto the design life, shall be stated.205 The effect of the chemicals listed as effluents from theinstallation shall be stated.

B. Terminations

B 100 Protection cloth for spliced eyes101 For spliced-eye terminations, protective cloth will nor-mally be required between the eye and the termination hard-ware that fits through the eye. Such cloth should provide lowfriction and high wear resistance.102 If a thin cover of elastomeric material is used to protectagainst chafing, then it shall be elastic such that the rope is notconstrained from stretching or bending.103 If a thick cover of elastomeric material is used to encap-sulate the eye, it shall be applied over a tape or cloth that coversthe eye and prevents direct adherence to and penetration ontothe load-bearing rope.

Guidance note:If the fibre rope segment is intended to be opened for later inspec-tion, such as a service insert or test specimen, then the segmentshould be equipped with sufficient cloth beneath the PU coatingsuch that the splice area can be opened as a loose carcass.


104 The splices and eyes should have the same or better

resistance to soil ingress as the fibre rope.

B 200 Termination hardware201 Termination hardware is required to fit and support theeye and should be made of steel.202 Pins shall be made from forged steel in compliance withDNV-OS-E302.203 The material in thimbles should comply with DNV-OS-E304. 204 The material in H-links should comply with DNV-OS-E302.205 Manufacturing by welding should comply with therequirements of DNV-OS-C401.206 Other materials, such as polymers and fibre-reinforcedcomposites can be used if they have been qualified based onDNV-RP-A203.

Guidance note:If the spool thimble is turned from solid plate, then Z quality shallbe used.Guidance on composite components may be found in DNV-OS-C501.


C. Mechanical properties

C 100 Minimum Breaking Strength – (MBS)101 The Minimum Breaking Strength – (MBS) of the fibre-rope assembly shall be stated by calculation and verified bytesting. The MBS should be stated in kN. The strength, ductil-ity and toughness of the termination hardware should be suchthat it can withstand the actual breaking strength of the ropeassembly.102 If termination hardware produced as part of the supply isnot available at the time of testing, then the properties of thetermination hardware can be demonstrated through non-linearFEM analysis. It is the responsibility of the manufacturer todefine the load case that acts on the termination hardware.

C 200 Change-in-length performance201 For determination of the change-in-length performanceof the fibre-rope assemblies, it is crucial that the testing reflectthe actual use scenario of the mooring system. Thus, the testingshall be specified according to the measurement results that areneeded to verify the mooring analysis.202 This sub-section describes basic performance character-istics that should be addressed. It is recommended that moredetailed analyses be carried out using exhaustive change-in-length performance data for the actual rope. Further informa-tion about the change-in-length behaviour of fibre ropes can befound in Appendix A.203 The test load levels shall be based on key data from themooring design analysis. The forces referred to are illustratedin Figure 1.

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Figure 1 Illustration of key lead levels.

C 300 Calculation of stiffness301 Dynamic stiffness should be calculated through the peakand trough points of the cycle, using the average rope lengthduring the cycle as basis. This is illustrated in Figure 2.

Figure 2 Illustration of peak-to-trough dynamic stiffness

With input in kN force and % strain, the dynamic stiffness for-mula becomes:

where

PF = Peak forceTF = Trough forcePS = Peak strainTS = Trough strainAVS = Average Strength302 For so-called static loading, the stiffness is calculatedusing the beginning point and end point, where the rope length atthe beginning point is taken as basis. This is shown in Figure 3.

Figure 3 Illustration of resulting static stiffness

With input in kN force and % strain, the static stiffness formulabecomes:

where

EF = End force.BF = Beginning forceES = End strainBS = Beginning strainAVS = Average Strength

Guidance note:These input values are read out from the data logging file.Normalisation of stiffness (with the average strength) is optional.


C 400 Post-Installation Stiffness401 The Post-Installation Stiffness (SINST) shall be deter-mined by testing. The post-installation stiffness is calculated as a resulting staticstiffness using the following values:

Trough values: Force and stretch after retraction at installedtension.

Peak values: Peak force and peak stretch from dynamicstiffness measurements.

Guidance note:The peak values are obtained when the sustained elastic stretchcorresponding to maximum storm duration has been imposed,such that the maximum length can be determined for offset cal-culations.


C 500 Dynamic Stiffness 501 The Dynamic Stiffness (SDYN) is defined as the maxi-mum stiffness of the mooring line which is predicted when themooring system is subject to a maximum design storm. It ischaracterised by comparatively short periods and small ampli-tudes. It shall be determined by testing.

— LOWER LOAD LEVELThe lower load level shall be equal to the sum of mean andmaximum low frequency tension (TMEAN+LF) specifiedfor the mooring system. Mean tension is the sum of preten-sion and tension caused by the static storm wind, currentand wave drift loads.

Pretension Tension due static loads from wind, current and wave drift forces

Tension due to wind and wave generated low frequency motions

Tension due to wave frequency motions

Total line tension in a storm with 100-year return period

TMIN

TMEAN+LF

TMEAN+LF+WF

TMEAN

PF

PS

TF

TS

Dynamic stiffness

Force vs. strain plot

AVSTSPSTFPFTSPSS

⋅−⋅−⋅++

=)(2

)()200(

EF

ES

BF

BS

Resulting static stiffness

Force vs. strain plot

AVSBSESBFEFBSS

⋅−−⋅+

=)(

)()100(

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— HIGHER LOAD LEVELThe higher load level shall correspond to the maximumload (TMEAN+LF+WF) determined from the mooring anal-ysis for the design storm condition, with a 100-year returnperiod.

502 Normally the maximum line tension for an intact moor-ing system is applied as the upper load level in connection withdetermination of SSTORM. If the result of the mooring analysiswith the “single line failure” shows significantly higher lineload, then the storm stiffness at this higher load should bedetermined.

C 600 Static Stiffness601 The Static Stiffness (SSTATIC) is explained as the stiff-ness of the mooring line after a time in service, in periods ofmoderate wave loading, wind and current, and should be deter-mined by testing if needed in the analyses. It is characterisedby comparatively long periods and large amplitudes. The staticstiffness can be used to represent the mooring line stiffnessafter it has been possible to re tension the system such that the

post-installation stiffness becomes over conservative. It is rec-ommended that the static stiffness is measured both before andafter test for dynamic stiffness that uses the maximum designstorm conditions.

— LOWER LOAD LEVELThe lower test load level shall be equal to the specifiedminimum tension limit during storm condition TMIN,specified for the mooring system.

— HIGHER LOAD LEVELThe higher test load level shall correspond to the maxi-mum load (TMEAN+LF) determined for mean tension andlow-frequency motion.

Figure 4 Example illustration of loading cycles during change-in-length tests, with corresponding stiffnesses.

602 Mooring systems are designed to survive a single linefailure. If the time to replace the line is significant, it will haveto be considered if the maximum line tension representing theupper load level should be represented by the single line failurecase.

C 700 Splice integrity701 Subrope testing and the cyclic fatigue test of the fibrerope assembly shall be used to determine that the splice designis self locking. The number of cycles to lock the splices shallbe stated and verified by testing.

C 800 Fatigue performance801 The Fatigue performance shall be verified for permanentsystems by fatigue testing of a new test specimen with subse-quent examinations and tests.

802 The resistance of the splices against slipping out shall bedocumented as part of the post-testing examination of thefatigue test sample.803 The requirement to fatigue testing of a rope assemblydoes not apply to MODU moorings.

C 900 Torque and rotation characteristics901 The torque and rotation characteristics are defined as theresulting torque and/or rotation that the rope exerts whenloaded.902 The torque and rotation characteristics shall be docu-mented and verified by testing.903 Alternatively for ropes that are designed to be torqueneutral, documentation that the rope is inherently torque neu-tral shall be provided.

Maximum installation force TMEAN+LF

TMEAN+LF+WF

TMIN

Force

Stretch

TMEAN

Post-installation stiffness. Static stiffness .. Dynamic stiffness .

Pre tension

Original stiffness .

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C 1000 Resistance to soil ingress1001 The resistance to soil ingress, if applicable, shall bestated and verified by testing and/or qualification as outlined inDNV-RP-A203.

C 1100 Weight pr. Unit Length (W/L)1101 The Weight pr. Unit Length (W/L) of the fibre rope inair should be documented by calculation and verified by test-ing. The weight pr. unit length in sea water should be stated.The W/L should be stated in kg/m.

C 1200 Maximum temperature due to Hysteresis Heating1201 The maximum temperature due to hysteresis heating isdefined as the maximum temperature obtained in the fibre ropeassembly during cyclic loading. For ropes in standard use anyhysteresis heating is normally not expected.1202 It shall be verified that the maximum temperature dueto hysteresis heating is 10ºC below the safe long-term temper-ature.

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SECTION 4MEASURING AND EXPRESSING

ROPE CHANGE-IN-LENGTH PROPERTIES

A. GeneralA 100 Introduction101 This section covers the most up-to-date definitions ofthe properties that govern change-in-length performance offibre rope. These properties are defined as separate entities inorder to describe and measure individual contributions to over-all length changes."

Guidance note:The separate definition of (visco-elastic) properties is done inorder to aid the understanding of change-in-length behaviour. Itis not required in order to perform the basic analyses and testsdescribed in Section 3 and Section 5, but may be useful in moreadvanced analyses and tests.


102 The change in length properties of a fibre rope can gen-erally be determined by simple test procedures.103 As discussed in Appendix A, the important properties infibre-rope change-in-length performance are:

εp Polymer Creep Strain, a function of time under tensionεc Rope Construction Strain, a function of highest applied

tensionSo Original stiffness, during first loading or during load-

ing to a load which is higher than any previous loadSs Static stiffness, during subsequent loadings less than or

up to the highest previously applied loadSd Dynamic stiffness, after a number of relatively fast

load cyclesεse Sustained Elastic Strain, which occurs during cycling

and is recoverable after cycling.

A 200 Stretch and Strain201 Stretch ΔL is the change in rope length under tensionand has the dimension of length. The magnitude of stretchmeasured in testing is proportional to specimen length.202 During testing, the gauge length over which stretch ismeasured should only include that portion of the specimenwhich is unaffected by splices and eyes.203 The gauge length is the length between extensometerfixation points when a subrope is tested in the laboratory. Asthe rope is loaded during installation and use, this gauge lengthwill change accordingly due to rope stretch.204 When the rope is new and tensioned to reference tensionfor the first time, the gauge length defines the reference length,denoted L0.205 Strain ε is the non-dimensional expression of stretch, theratio of stretch length under tension to the original lengthbefore applying tension.

ε = ΔL / Lo where

ε = strainΔL = stretchLo = original length, for testing this is the reference length

206 Thus for example, when polymer stretch is measured ina test, it should be divided by reference length and expressedas polymer strain εp. This is sometimes called creep.

εp = ΔLp / Lo where

εp = polymer strain Δlp = stretch due to polymer strain

207 Construction stretch should be divided by referencelength and expressed as rope construction strain εc.

εc = ΔLc / Lowhere:

εc = construction strainΔLc = stretch due to construction stretch

Guidance note:The terms extension and elongation are sometimes used forstretch and strain. Because those terms are not intuitive and areused in various, sometimes opposing manners by different partsof the rope using community, their use here is discouraged.


A 300 Spring Rate and Stiffness301 Spring Rate K is the ratio of change in tension to changein stretch. The dimensions are force / length.

K = ΔF / ΔLwhere

K = spring rateΔF = change in applied tension

302 Stiffness S is the non-dimensional form of spring rate.The stiffness property can be applied to ropes of any length andany strength.

S =(ΔF/AVS) / (ΔL/Lo)where

S = stiffnessAVS = average strength

Guidance note:It is preferred that average strength (AVS) be used as the basisfor normalising stiffness. The minimum breaking strength is arequirement, not a property of the rope.


303 The spring rate of any particular mooring line can thenbe readily determined by

K = S × AVS / Lwhere

AVS = average strength of mooring lineL = length of mooring line304 The use of these change-in-length properties in mooringsystem design is discussed in DNV-OS-E301.

Guidance note:DNV-OS-E301 is due to be revised to contain this informationand other updates. Until issued, further information may befound in the 2008 revision of API-RP2SM.


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SECTION 5SPECIFICATION OF TESTING

A. General

A 100 General101 This section covers specification of testing to verify theproperties and performance of the fibre-rope assemblies to bemanufactured and delivered.102 The reference tension to be used for the testing is 1%MBS.103 When testing subropes, the force levels shall be based onthe MBS of the fibre-rope assembly divided by number of sub-ropes.

Guidance note:Since the MBS is a specified force level and not a physical prop-erty, the MBS divided by number of subropes will differ fromthat of the subrope.


A 200 Data recording and measurement accuracy201 Force, time, displacement and stretch should be loggedat a sufficient rate when measurements are taken. Considera-tion should be given to the required accuracy, whilst avoidingexcessive data files.

Guidance note:The following sampling rates may be taken as advice:


202 Change-in-length measurements should be performedon subropes, with the extensometer attached to the same strandat both ends.

Guidance note:For change-in-length measurements on fibre rope, the extensom-eter should be attached on the outer jacket with fixations that aregripping or squeezing the whole cross section. However, meas-urement on subrope is the preferred method, and the accuracywhen measuring on fibre rope shall therefore be justified. It mustbe ensured that the jacket follow the changes in length of theload-bearing subrope bundle.The gauge length for stretch measurements needs to be commensu-rate with the accuracy of the length-measurement device. Advice isprovided in CI 1500, Table 1M page 13 and Appendix A.


B. Testing of Yarn

B 100 General101 The material test shall be carried out for each lot or foreach 20 000 kg, whichever is less. It shall be stated whether or

not the results are in compliance with yarn manufacturer’s cer-tificate.102 The testing should be performed according to OCIMF,Guidelines for the Purchasing and Testing of SPM Hawsers,Appendix II.103 Four separate bobbins from different pallets should betested; one from the beginning, two from the middle and onefrom the end of each lot. Three tests should be performed oneach 10-kg bobbin.

C. Testing of subrope

C 100 General101 Provided production settings are not changed, the sam-ples for testing may be produced and tested before productionof the delivery.102 It is the rope manufacturer’s responsibility to take suffi-cient number of subrope samples in order to complete the nec-essary tests to document the fibre-rope properties. Thisincludes necessary spare length if other testing should berequired later.103 The following number and selection of subrope speci-mens should be followed for certification:

C 200 Number and selection of subrope test specimens.

201 The change-in-length and strength measurements shallbe performed identically on each subrope sample. For helicalsubrope constructions, three S and two Z specimens should beused.202 For helical subropes, the splice integrity test specimensshould be one S and two Z; and the weight test specimens shallbe one S and one Z.

D. Testing of Fibre Rope and Fibre-Rope Assembly

D 100 Number and selection of fibre-rope test speci-mens101 Provided production settings are not changed, the sam-ples for testing may be produced and tested before productionof the delivery.102 It is the rope manufacturer’s responsibility to take suffi-cient number of samples of the completed fibre rope in orderto complete the necessary tests to document the fibre-ropeproperties. This includes necessary spare length if additionaltesting should be carried out on behalf of the user.103 The following number and selection of fibre rope test

Break test at loads above 75% MBS: 0.5 seconds between points.

Dynamic stiffness: 20 - 30 points per cycle.Fast changes in load level: 2 seconds between

points.Initial parts of static measurements: 1 - 10 seconds between

points.Final parts of static measurements: 1 minute - 1 hour

between points.

Table C1 Requirements to subrope test specimens for certification

Type of test: Number of test specimens:Change-in-length performance. 5 subropes.Breaking strength. 5 subropes.Splice integrity. 3 subropes.Weight per unit length. 2 subropes.

DET NORSKE VERITAS


specimens should be followed for certification:

104 The lowest result defines the actual breaking strength ofthe delivery.105 The test requirements for torque and rotation character-istics shall be determined on a case-by-case basis.106 The test requirements for soil-ingress resistance testingshall be determined on a case-by-case basis.107 Production parameters should not be changed after themanufacture of the test specimens.108 The same set of termination hardware may be used forall tests that require a fibre-rope assembly to be tested.

E. Test methodsE 100 Introduction101 All tests shall be described in the testing specification.The key load levels and other information from the mooringanalysis needed to define the change-in-length performancetesting shall be submitted to the manufacturer by the user.102 Due to the dependence of the rope change-in-length per-formance on the actual loading, the testing specification shouldreflect the actual loading scenario as closely as possible. Thetest methods for change-in-length performance described inthis section are given for guidance, as a starting point for estab-lishing the testing specification for the specific delivery. Ageneric description of the individual characteristics that consti-tute the fibre-rope change-in-length behaviour is given inAppendix A.

E 200 Testing of change-in-length performance on subropes201 Since a MODU mooring system may be used in differentlocations and service scenarios, the change-in-length perform-ance testing for MODU systems may be carried out based on APIRP-2SM, ISO 18692, section B.3, or CI 1500-02, Appendix A.202 A basic test procedure for change-in-length perform-ance for permanent mooring systems is presented in the fol-lowing for guidance. The testing specification shall reflect theactual loading scenario for the mooring system, and thechange-in-length test programme will therefore need to beexpanded or adapted.203 The subrope specimen should be pre soaked by com-plete immersion in fresh water overnight prior to testing.204 The specimen should not have been previously loaded.205 For establishment of the post-installed condition, thespecimen should be loaded five times between reference ten-sion and installation test load for anchors, or pre-tensioningload for installed system, whichever is the higher. On reduc-tion of load during the last cycle, the force shall be maintainedat the installed tension and the rope should be allowed toretract for 20 minutes at constant force.206 For testing of dynamic stiffness the same specimen shallbe loaded between the lower and higher load level with aperiod between 10 and 20 seconds for 130 cycles.

207 The dynamic stiffness shall be measured on the final 5cycles.208 For testing of static stiffness the same specimen shouldbe loaded between the lower and higher load level for 130cycles.209 The static stiffness shall be measured on the final 5cycles, using a period between 60 to 180 seconds.

Guidance note:When measurements are not taken the cycling should be as fastas possible.It is recommended to measure the static stiffness both before andafter measurement of the dynamic stiffness.


210 After the stiffness measurements, the specimen shouldbe subject to a break test.211 The following measurements should be taken:

— Force vs. stretch curve for the installation test cycles andretraction at installed tension

— Force vs. stretch curve for cycles 1-10, cycle 100 and last10 cycles for dynamic and static stiffness.

212 The following should be reported:

— Post-installation stiffness between end of retraction andpeak of final dynamic cycles

— Dynamic stiffness on final cycles and cycle period duringmeasurement

— Static stiffness on final cycles and cycle period duringmeasurement

— Breaking strength report requirements.

E 300 Testing of breaking strength on fibre-rope assem-bly or subrope301 The specimen shall be pre soaked by complete immer-sion in fresh water overnight. It should not have been previ-ously loaded to more than 70% MBS.302 Fibre-rope assemblies shall be break tested using termi-nation hardware that is manufactured as part of the supply.303 Recommended test procedure:

— 10 cycles between reference tension and 50% MBS— Loading to failure. Above 75% MBS, the loading rate

should be kept constant at approximately 50% MBS/min.

The following should be reported:

— Force vs. stretch curve for cycles 1, 2 and 10 to 50% MBS— Breaking force and force vs. displacement curve for the

loading to break— The rate of loading reported in kN/min for the region

above 75% MBS— Location of failure.

304 The specimen should fail on the free length or at the toeof the splice region.

Guidance note:As applicable, the same specimen as used for change-in-lengthmeasurements may be used without re soaking.For fibre-rope assemblies, the diameter of thimble/H-link pinholes may be increased by machining to fit the loading pins of thetest machine.A force-control test machine is not required.


E 400 Testing of splice integrity on subropesThe subrope specimen shall be pre soaked overnight prior totesting.

Table D1 Requirements to fibre rope test specimens for certification

Type of test: Number of test specimens:Breaking strength. 5 fibre-rope assemblies.Fatigue test. 1 fibre-rope assembly.Torque and rotation, if applicable. 1 fibre-rope segment.Soil ingress resistance, if applica-ble.

1 fibre rope or -segment.

Weight per unit length. 1 fibre rope.

DET NORSKE VERITAS


It shall then be fitted on smooth steel pins in the test machineand cycled between 5% MBS and 50% MBS for a minimum of1000 cycles or until the force vs. stretch measurements demon-strate that the splices are self locking.The following should be reported:

— Force vs. pin-pin stretch curve for first 10 cycles, cycle 20,50, 100, 200, 500 and last 5 cycles up to 1000

— Photographic documentation as necessary.

E 500 Fatigue501 The specimen shall be pre soaked by complete immer-sion in fresh water overnight prior to testing. 502 The fatigue testing should be carried out on terminationhardware manufactured as part of the delivery.

Guidance note:The diameter of thimble/H-link pin holes may be increased bymachining to fit the loading pins of the test machine.


503 The sample should be equipped with an irrigation sys-tem to add sufficient fresh water to keep the sample moist andcooled during the fatigue test. Alternatively, testing may beperformed submersed.504 The following test procedure applies:

— Loading 6,000 cycles between 5% and 50% MBS— Loading 14,000 cycles between 5% and 44.1% MBS.

505 Examination of specimen:

— Dimensions and external condition of splice and eye— Condition of specimen interior— Perform break testing of 5 selected subropes.

506 The following shall be reported:

— Force vs. pin-pin stretch curve of first 10 cycles, cycle 20,50, 100, 200, 500, 1000, etc. and last 5 cycles of part 1

— Force vs. pin-pin stretch curve of first 10 cycles, cycle 20,50, 100, 200, 500, 1000, etc. and last 5 cycles of part 2

— Photographic documentation from examinations— Break test reporting requirements for the subropes— Documentation based on the force vs. stretch plots for pin-

pin that the splice is self locking.

E 600 Testing of Weight/Unit Length601 Suitable methods for this measurement may be found inCI 1500-2, section 8.3 page 6 or ISO 18692, section B.4page 20.

E 700 Soil ingress resistance.701 The test requirements for soil-ingress resistance shouldbe determined on a case-by-case basis.

E 800 Testing of maximum temperature due to Hystere-sis Heating801 If deemed necessary, the maximum temperature shall bemeasured during Fatigue testing.802 The measuring method shall ensure that it is the temper-ature of the fibre, and not that of the surrounding air or water,which is measured.803 If the measured temperature is considered to be higherthan can be expected under actual load conditions, e.g. due toapplication of a broader than actual load range, then the load-ing regime should be modified during the temperature meas-urements to avoid over conservatism.

F. Termination hardwareF 100 Non-destructive testing101 The requirements for non-destructive tests to be carriedout on termination hardware are given in DNV-OS-E304 forspool thimbles or DNV-OS-E302 for H-links. For weldedthimbles, the requirements to NDT are given in DNV-OS-C401, Chapter 2, Section 3, pages 35 through 37.

F 200 Mechanical testing201 The requirements to mechanical testing are given inDNV-OS-E302.202 It is the responsibility of the rope manufacturer to definethe critical sections of the termination hardware, and to ensurethat sufficient materials testing is carried out on material takenfrom sacrificial item which is produced as part of the actualdelivery.

F 300 Fibre-rope assembly301 One set of the termination hardware shall be tested aspart of fibre-rope assembly break testing and fatigue testing.

DET NORSKE VERITAS


DET NORSKE VERITAS



CHAPTER 3

CLASSIFICATION AND CERTIFICATION

CONTENTS PAGE

Sec. 1 Classification and Certification................................................................................................ 29Sec. 2 Work process............................................................................................................................ 30App. A Fibre-rope Stretch and Stiffness ............................................................................................... 33App. B Quality Review Report............................................................................................................. 35App. C Example of Certificate Format ................................................................................................. 37



SECTION 1CLASSIFICATION AND CERTIFICATION

A. Classification

A 100 General101 The principles, procedures, applicable class notationsand technical basis for offshore classification are given inDNV-OSS-101 for Offshore Drilling and Support Units andDNV-OSS-102 for Floating Production and Storage Units.

B. Certification of mooring analysis

B 100 General101 Certification of mooring system analysis is covered inDNV-OS-E301. The technical provisions are given in Chapter 2and the certification and classification requirements are given inChapter 3.

C. Certification of Fibre-Rope Assemblies

C 100 Introduction 101 This chapter describes the work process that shall takeplace when fibre-rope assemblies are certified according to therequirements of this standard. It is attempted to give this chap-ter a chronological order such that the prerequisites for certainsteps or milestones may be readily determined. The require-ments are found in Chapter 1 and Chapter 2.102 Apparent compliance to the provisions of this standarddoes not imply that a product is certified; nor does apparentnon-compliance to certain provisions imply that a product can-not be certified. Certification is a matter of judgement by DNVbased on the documentation provided and performed survey(and qualification), founded on the complete set of provisionsthat are given in this standard.103 In cases of new deliveries with similar materials, con-struction etc. the requirements to documentation and testingwill be considered in each case based on application for devi-ations or test waivers.

C 200 Main elements in certification201 The main elements in certification of fibre-rope assem-blies are design assessment and inspection survey.The design assessment covers:

— Review of specification and documentation from the user— Review of documentation covering rope design, produc-

tion and performance— Evaluation of test results— Issuance of Design Verification Report.

The fabrication survey covers.

— Survey of testing— Follow-up and witness of the production based on the fol-

lowing:

— Manufacturing specification— Inspection & Test Plan.

— Issuance of survey report— Issuance of the DNV certificate for each fibre-rope assem-

bly.

C 300 Additional qualification activities301 In case of special service requirements, additional qual-ification activities shall be carried out based on DNV-OSS-401, subject to approval by DNV.302 Provided the appropriate qualification is carried out,special service without insert retrievals and / or sea-bed contactduring installation is permissible under this standard.

C 400 Deviations and test waivers401 If a manufacturer or user wishes to deviate from therequirements of this Offshore Standard then thoroughly docu-mented request for waiver of test or deviation shall be submit-ted for approval by DNV. Any such request should be includedin the Request for Certification.402 Any deviations, exceptions and modifications to refer-enced codes and standards shall be documented and agreedbetween user, manufacturer and DNV, as applicable.403 Equivalent standards can be used subject to approval byDNV.

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SECTION 2WORK PROCESS

A. GeneralA 100 Introduction101 In the following, the work process is described. Theprocess consists of the following main steps in chronologicalorder:

— Request for certification— Pre-production meeting— Submittal of documentation for approval— Design review— QA/QC review— Production and survey— Issuance of certification documents.

A 200 Request for certification201 The request for certification should be sent to DNV bye-mail. The following information should be included:

— Manufacturer name, and plant location— Production and delivery schedules for fibre-rope segments

and termination hardware— Testing facilities, location and testing schedule— Type of unit; floating production unit, mobile offshore

unit or other type— Taut-leg mooring system or other type— Number of mooring lines in which fibre ropes will be used— Total number of fibre-rope assemblies, and number of

assemblies in each mooring line— Dimension, breaking strength of the fibre rope, including

type of fibre and rope construction— In-service condition assessment scheme (For permanent

mooring system.)— Key results from mooring analysis in order to decide the

load levels to be used in the certification test program (Forpermanent systems.)

— Any requests for deviations or test waivers, fully docu-mented.

A 300 Pre-production Meeting301 A pre-production meeting shall be held at the manufac-turer’s premises prior to start of the certification process.302 The meeting shall include representatives from the fol-lowing organisations:

— Manufacturer of the fibre ropes— DNV surveyor from local survey station appointed to fol-

low up production and testing— Responsible from DNV-Høvik if found necessary. In case

of use not directly covered by this standard, this is manda-tory

— Responsible from testing facility if the tests are not carriedout by the manufacturer or by DNV.

303 The presentation made by the manufacturer shallinclude:

— Scope of work— Outline and description of the components to be produced.— Content and requirements of purchase orders/specifica-

tions— Testing facilities— Any requests for deviations or test waivers— Any elements not directly covered by this standard— Manufacturer’s specification regarding production, termi-

nations and testing.

304 The presentation made by DNV will include:

— Introduction to the DNV-OS-E303 (This standard.)— Outline and explanation of specific requirements regard-

ing class and certification— Scope of verification and inspections to be carried out by

DNV:

— Status of documentation submitted to DNV— Quality systems (QA/QC review)— Inspection during fabrication of fibre-rope segments

and termination hardware— Witnessing during testing.

— Final documentation requirements:

— Content— Issue and distribution— Review of final documentation.

305 Minutes of Meeting from the pre-production meetingshould be distributed to the involved parties.

B. QA/QC ReviewB 100 General101 The main purpose of the review is to determine how ade-quate the implementation of the manufacturer’s quality systemis with respect to the specific activities required, and to accom-modate DNV’s involvement to assure the quality of the prod-uct.102 The departments, sections, production lines and testingfacilities directly engaged with the manufacture of fibre-ropesegments should be included in the review, to the extent appli-cable for the particular contract in question.

B 200 Quality Review Report201 The quality review report in Appendix B is recom-mended to be used as a general checklist when carrying out theQA/QC review.

B 300 Design assessment301 The design assessment is will be carried out based on thedocumentation received at this stage in the work process.302 The documentation requirements and the responsibili-ties of the user and the manufacturer are summarised in Chap-ter 2. Approved design documentation and procedures will belisted in the Design Verification Report (DVR).

C. TestingC 100 General101 The testing shall be carried out according to the provi-sions set forth in Chapter 2.102 The testing specification describing all tests is subject toapproval by DNV.103 Subject to documentation and approval by DNV, two ofthe fibre-rope assembly specimens may be used for change-in-length testing instead of the five subropes.104 If fatigue testing and subsequent examinations accord-ing to approved procedure of an equal-size or larger, but other-

DET NORSKE VERITAS


wise identical, fibre-rope assembly has been carried outbefore, then the fatigue test need not be carried out – subject toa documented waiver request and approval by DNV.

Guidance note:The same specimen can be used for measuring different proper-ties.The force vs. change-in-length performance of the mooring lineis paramount to the system design. Thus, design-specific specifi-cation should be made for each mooring system. Notwithstand-ing this, universal test results for stiffness and change in lengthcan be accepted.Examples on change-in-length tests can be found in API RP 2SMor in ISO 18692, section B.3 or in CI 1500-02, Appendix A.Examples of torque-measurement testing and soil-ingress resist-ance testing can be found in ISO 18692, sections B.6 and B.7.


C 200 New techniques (under development)201 The following methods are developed in Joint IndustryProjects:

— Method for providing documentation such that inserts-based inspection can be avoided.

— Universal test method for determination of change-in-length performance.

Guidance note:DNV can approve the use of JIP findings for certification offibre-rope assemblies. However, the use of said findings may besubject to confidentiality.


D. Start up of production

D 100 General101 It may be prudent to start the production prior to comple-tion of the full design review. Such advance production may bepermitted provided the following documentation / informationhas been reviewed by DNV:

— User specification— Manufacturing specification— Handling and installation procedure— In-service condition assessment scheme— Delivery date and date to be put in service— Key results from mooring design analysis for definition of

testing specification— Testing specification— Subrope test results for strength, change-in-length per-

formance and splice integrity.

102 This documentation shall be submitted in due time toallow proper design review and comments with subsequentimplementation.103 Manufacturing shall not take place until DNV has noti-fied that the above documentation has been reviewed.

E. Survey during production and testingE 100 The survey comprises the following main ele-ments101 Check that the fibre producer has prepared a sufficientyarn certificate.102 Check that the yarns and fabrics to be applied in thesheathing process are documented.103 Witness the manufacturer tests of load bearing yarns.One or two visits should normally be adequate. The manufac-turer issues the testing specification subject to approval byDNV.104 Prior to start of testing, the attending surveyor and theresponsible test engineer should review the approved testingspecification.105 Number of rope tests to be witnessed has to be decidedby the surveyor based on experience with the product and thetesting laboratory. Survey is not required for testing carried outby DNV.106 Witness that the production is carried out in accordancewith the manufacturing specification and associated QA plansregarding the production of subropes, fibre ropes, terminationsand sheathing.107 Periodic monitoring of a satisfactorily functioning qual-ity system may be used as verification of specific stages of thefabrication process.

F. Documents issued or attested by DNVF 100 General101 The surveyor will attest manufacturer’s test reports forreceived yarns.102 The surveyor will attest reports for the testing of thefibre-rope assemblies. The surveyor’s comments, if any, willbe included.103 DNV will issue a survey report (SR). Any findings andnon-compliance with the manufacturing specification and QAplans will be reported together with actions taken. The reportshould be attested by the manufacturer’s QA responsible.104 DNV will issue a Design Verification report (DVR) forthe fibre rope assemblies. The DVR will state:

— Documents which have been reviewed— Complying standards— Assumptions— Conditions and limitations— A list of all documents from the client/manufacturer will

be included together with reference correspondence; anycomments which are to be taken into account.

G. CertificatesG 100 Introduction101 Figure 1 shows the documentation that form basis forissuance of the DNV certificates for fibre-rope assemblies.

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Figure 1 Documentation for certification of fibre-rope assemblies in mooring systems.

102 The following will be furnished with a DNV certificate:

— Fibre-rope assembly— Termination hardware.

G 200 Certificates for Load-Bearing Yarns201 Load-bearing yarns shall be supplied with a works cer-tificate, issued by the producer.

G 300 Fibre-Rope Assemblies301 Each fibre-rope assembly will be furnished with its ownDNV certificate.302 The DNV certificate will be of one page and refer to thefollowing only:

— User / client— Purchase Order No— User specification— Installation / location of use— Design Verification Report from document review and

design assessment according to this standard

— Survey Report— DNV Certificates for the termination hardware, one for

each termination.

303 Example of certificate is shown in Appendix C.304 For each DNV certificate, there should be an accompa-nying inspection and test plan sheet identifying which surveyactivities have been carried out for each fibre-rope assembly.

Guidance note:The following documents will no longer be issued as part offibre-rope assembly certification:

— Certificate of Compliance— DVR for mooring analysis— Inspection Release Note.

The DVR for the mooring analysis will be issued by DNV sepa-rately on behalf of the user. That work will be based on the designstandard DNV-OS-E301 and not this standard.


DNV certificate for each fibre-rope assembly.

Design Verification Report.

Yarn certificates: - Producer. - Survey of

testing.

Inspection Report - Rope &

sheathing. - Splicing &

protection.

Test Reports - Strength. - Stiffness. - Fatigue, etc.

DNV certificate for termination hardware.

Survey Report.

Manufacturer’s documentation.

User documentation - Specification. - Inspection

scheme. QA/QC review.

I&T P sheet for each fibre-rope segment.

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Offshore Standard DNV-OS-E303, April 2008Ch.3 App.A –

APPENDIX A FIBRE-ROPE STRETCH AND STIFFNESS

A. BackgroundA 100 Basic Rope Change-in-Length Properties101 The change-in-length characteristics of fibre ropes aremore complex than those of steel wire rope. Stiffness can benon linear. Strain is greater for same load level. Permanentstrain can be significant. Both stiffness and strain depend onloading history.102 Stretch ΔL is defined as the change in length of the rope.103 Strain is defined as the change in length divided by itslength before change in tension, ε = ΔL / Lo . Stretch ΔL canbe determined by multiplying strain by the rope length.104 Stiffness is defined as the ratio of change in force ΔF toaverage strength divided by the ratio of stretch to originallength; S = (ΔF/AVS) / (ΔL/Lo). Spring rate K can be deter-mined by multiplying stiffness by rope strength and dividingby rope length.105 The change-in-length characteristics of polyester ropescan generally be described by six elements.

εp Polymer Creep Strain, a function of time under tensionεc Rope Construction Strain, a function of highest applied

tensionSo Original stiffness, during loading to a load which is

higher than any previous load Ss Static stiffness, during subsequent loadings less than or

up to the highest previous loadSd Dynamic stiffness, after a number of relatively fast

load cyclesese Sustained Elastic Strain, which occurs during cycling

and is relaxed after cycling

A 200 Mooring Line Change-in-Length Properties201 The terms ‘stretch’ and ‘spring rate’ are used when treat-ing the change-in length performance of a mooring rope ofknown strength and length. Alternatively, the basic rope prop-erties ‘strain’ and ‘stiffness’ could be used.

ΔLp Polymer Creep StretchΔLc Rope Construction StretchKo Original Spring RateKs Static Spring RateKd Dynamic Spring RateΔLse Sustained Elastic Stretch

202 Spring rate affects the maximum mooring line tensionand thus the required rope break strength.203 Permanent stretch affects change in line length. It is ofconcern when determining the mooring line length required forinstallation and the amount of line which must be taken up dur-ing installation. It can also be of concern when determining thelength of line which might need to be taken up during the serv-ice life of the mooring.204 Both spring rate and stretch affect maximum mooringline length during extreme events and thus affect the maximumplatform offset and the required riser or drill string length.

A 300 Original Spring Rate and Construction Stretch301 Figure 1 illustrates the first three elements of change-in-length performance. When load is first applied, the rope struc-ture is compacted and stretched. When load is relieved fromthe rope after the first loading, this stretch remains. We call thepermanent stretch which takes place during the first loadingconstruction stretch.302 Construction stretch is retained unless the rope is flexedin a completely relaxed condition.303 The rope spring rate is relatively soft on the first loadingbecause it includes construction stretch. The spring rate duringthe first loading to any particular tension is referred to as theoriginal spring rate.

Figure 1 Original Spring Rate, Construction Stretch, and Static SpringRate

A 400 Static Spring Rate and Continued Original Spring Rate401 After construction stretch takes place, the spring rateincreases, as shown in Figure 8. We call the spring rate whenthe rope is subsequently loaded below the previous high loadapplied to the rope static spring rate.402 Designate the highest load which has been applied to therope as Th1. Each subsequent time the rope is tensioned to aload T1 which is less than Th1, it will follow the static springrate curve.As tension is relieved, the rope will retract along the staticspring rate, but the construction stretch ΔLC1 remains.403 The first time the rope is tensioned to a load higher thanTh1, it will follow the static spring rate curve up to Th1, andbeyond that point it will follow the original spring rate curveup to that higher load. This is shown in Figure 2.

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Offshore Standard DNV-OS-E303, April 2008 – Ch.3 App.A

Figure 2 Spring Rates to Higher Load

404 As tension is relieved, the rope will retract along a staticspring rate curve which is offset from the earlier spring ratecurve. The distance between the two lines is the additional con-struction stretch imparted by the higher load, and the total con-struction stretch will then be ΔLC2 . A new upper bound Th2will be established for the static spring rate curve.

A 500 Polymer Stretch501 Figure 3 illustrates the polymer stretch characteristic.When load is maintained on the rope, the polymer fibres creep,and as a result the rope continues to stretch. The rate of poly-mer stretch may be rapid at first. For most synthetic fibres therate of stretch diminishes with time. (An exception is HMPEfibre).502 For polyester rope, polymer stretch can be plotted as astraight line against log time, as shown to the right in Figure 3.After a few days under tension, the rate of polymer stretch isvery small, and additional polymer stretch might be insignifi-cant.

Figure 3 Polymer Stretch

503 After polymer stretch occurs, the static spring rate curveshifts to the right, as shown on Figure 10.

Guidance note:During construction stretch, some polymer stretch also occurs.That stretch may be considered part of construction stretch.


A 600 Sustained Elastic Stretch and Dynamic Spring Rate601 Figure 4 illustrates both sustained elastic stretch anddynamic spring rate. After a number of load cycles are applied,additional stretch occurs. When cycling stops and load isdecreased this stretch is relaxed; thus it is elastic. It is referredto as sustained elastic stretch.602 When the rope is cycled a number of times, it becomesstiffer than the static spring rate. It is referred to as dynamicspring rate.

Figure 4 Sustained Elastic Stretch and Dynamic Spring Rate

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Offshore Standard DNV-OS-E303, April 2008Ch.3 App.B –

APPENDIX B QUALITY REVIEW REPORT

(For use as supplement to certification of offshore mooring fibre ropes)

Manufacturer: Project identity:

Components: Purchase Order No.:

1. General Yes No Comments

1.1: Does manufacturer have a QA certificate issued by DNV for production of fibre ropes?If yes, certificate no. _________________ 1.2: Has the manufacturer established a formal Quality System?- According to which standard:_______________- Is the system documented?1.3: Has the purchaser carried out a QA review of the manufacturer?If yes, report no,:____________________1.4: Is there a quality manager assigned?- Name: ___________________________1.5: Is there a person in the organisation who is responsible for quality inspec-tion?- Name: ___________________________2.0 Planning

2.1: Is inspection plans prepared, based on required service description and standards ?2.2: Are possible subcontractors evaluated?

2.3: Are job instructions and procedures describing how inspections shall be carried out prepared?2.4: Are above instructions and procedures implemented by the manufac-turer?- How many years: ___________________________2.5: Does QC/inspection department have a system to report non-conformities and repairs?2.6: Does the manufacturer has the latest edition of service description and standards that are required?3.0 Subcontractors

3.1: Will the manufacturer use subcontractors?- How many: ______________________________3.2: Are actions taken to assure that materials, products and services supplied by subcontractors meet the specified requirements?3.3: Are there procedures for incoming inspections of materials and products, and associated documents to assure they conform to specific requirements?- Procedure No.: _________________________4.0 Production

4.1: Are actions taken to ensure necessary identity/marking of materials and products?4.2: Are all measuring and testing equipment calibrated at established inter-vals?4.3: Do the calibration records appear adequate and in order?

4.4: Have adequate procedures/instructions been prepared for control of pro-duction methods, processes and inspection methods?- Procedure No.: ____________________________- Title: ___________________________________4.5: Are procedures for verifying and tractability of load-bearing yarn mate-rial established?- Procedure No.: ______________________________4.6: Are procedures for tractability of yarns applied in the jacketing process of the ropes established?- Procedure No.: ______________________________

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Offshore Standard DNV-OS-E303, April 2008 – Ch.3 App.B

The findings in this report have been agreed on with the manufacturer. The implementation of the various activities will be mon-itored during inspections carried out by DNV.The final acceptance of the product will be documented in a product certificate.

4.7: Are splicing procedures developed?- Procedure No.: ______________________________4.8: Are load levels to be applied in testing decided, and are the data verified?- Document No.: ____________________________- Title: ___________________________________- DVR No.: ________________________________4.9: Are the set up of the spinning machines correct?- By whom: ________________________________4.10: Are the persons that shall accept or reject the fibre ropes familiar with the acceptance criteria?4.11: Are actions taken to ensure that the length of test samples and test requirements are according to the capability of the test facility?4.12: Are all inspection results recorded and stored to show if specific require-ments are met?4.13: Are actions taken to ensure satisfactorily control of non-conforming products?4.14: Are actions taken to ensure that final inspection is performed?

4.15: Is final inspection sufficiently comprehensive to assure that specified requirements are met?4.16: Are there adequate procedures for re-inspection procedures of corrected repaired or modified products?- Procedure No.:_______________________________4.17: Are all final inspection results recorded?

Date: Date:

------------------------------------------------ ------------------------------------------------Manufacturer’s signature Signature for DNV

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Offshore Standard DNV-OS-E303, April 2008Ch.3 App.C –

APPENDIX C EXAMPLE OF CERTIFICATE FORMAT

This Certificate is issued for the information of interested parties to indicate compliance with the provisions of DNV Offshore Standard DNV-OS-E303, April 2008, (hereinafter referred to as “the Standard”)

Particulars of fibre-rope assembly:

Name of Owner:

Name of Installation:

Location (N/A for MODU):

Purchase Order No.:

Owner Specification:

Design Verification Report:

Survey Report:

Fibre-Rope Segment identification:

DNV Certificates for termination hardware (2 off):

In-service inspection program:

Procedure for handling and installation:

- PermanentType ofservice:

- MODU

THIS IS TO CERTIFY:

1. That the fibre-rope assembly has been subject to design review, manufacturing survey and testing according to the provisions of theStandard; and

2. That for its designated service the fibre-rope assembly has been found to be in compliance with the requirements of the Standard.

Remarks/Recommendations:

This Certificate is valid until ………………... subject to the provisions set forth in the in-service inspection program, and as otherwise stated onthe above referenced Design Verification Report.

Completion date of survey on which this Certificate is based:Issued at:

Place/Country

for Det Norske Veritas AS

(name)Surveyor

………………...

…………………/…………………. on (date) ………………...

DET NORSKE VERITAS AS, Veritasveien 1, NO-1322 Høvik, Norway, Tel.: +47 67 57 99 00, Fax: +47 67 57 99 11, Org.No. NO 945 748 931 MVA www.dnv.comForm No.: xxx Issue: April 2008 Page 1 of 1

DET NORSKE VERITASCertificate No.:

Date of issue:

CERTIFICATEFIBRE-ROPE ASSEMBLY

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Offshore Standard DNV-OS-E303, April 2008 – Ch.3 App.C

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