Certification of Fibre Ropes for Deepwater Offshore Services · • class the Unit and enter the...

Certification of Fibre Ropes for Deepwater Offshore Services

December 2018

Guidance Note NI 432 DT R02 E

Marine & Offshore

8 Cours du Triangle - CS 50101 92937 Paris La Defense Cedex - France

Tel: + 33 (0)1 55 24 70 00 https://marine-offshore.bureauveritas.com/bv-rules

© 2018 Bureau Veritas – All rights reserved

BUREAU VERITAS MARINE & OFFSHORE

GENERAL CONDITIONS

1. INDEPENDENCE OF THE SOCIETY AND APPLICABLE TERMS1.1 The Society shall remain at all times an independent contractor and neither the Society nor any of its officers,employees, servants, agents or subcontractors shall be or act as an employee, servant or agent of any other partyhereto in the performance of the Services.1.2 The operations of the Society in providing its Services are exclusively conducted by way of random inspectionsand do not, in any circumstances, involve monitoring or exhaustive verification.1.3 The Society acts as a services provider. This cannot be construed as an obligation bearing on the Society toobtain a result or as a warranty. The Society is not and may not be considered as an underwriter, broker in Unit’s saleor chartering, expert in Unit’s valuation, consulting engineer, controller, naval architect, designer, manufacturer,shipbuilder, repair or conversion yard, charterer or shipowner; none of them above listed being relieved of any of theirexpressed or implied obligations as a result of the interventions of the Society.1.4 The Society only is qualified to apply and interpret its Rules.1.5 The Client acknowledges the latest versions of the Conditions and of the applicable Rules applying to theServices’ performance.1.6 Unless an express written agreement is made between the Parties on the applicable Rules, the applicable Rulesshall be the Rules applicable at the time of entering into the relevant contract for the performance of the Services.1.7 The Services’ performance is solely based on the Conditions. No other terms shall apply whether express orimplied.

2. DEFINITIONS2.1 “Certificate(s)” means classification or statutory certificates, attestations and reports following the Society’sintervention.2.2 “Certification” means the activity of certification in application of national and international regulations orstandards, in particular by delegation from different governments that can result in the issuance of a Certificate.2.3 “Classification” means the classification of a Unit that can result or not in the issuance of a classificationCertificate with reference to the Rules. Classification is an appraisement given by the Society to the Client, at a certaindate, following surveys by its surveyors on the level of compliance of the Unit to the Society’s Rules or to thedocuments of reference for the Services provided. They cannot be construed as an implied or express warranty ofsafety, fitness for the purpose, seaworthiness of the Unit or of its value for sale, insurance or chartering.2.4 “Client” means the Party and/or its representative requesting the Services.2.5 “Conditions” means the terms and conditions set out in the present document.2.6 “Industry Practice” means international maritime and/or offshore industry practices.2.7 “Intellectual Property” means all patents, rights to inventions, utility models, copyright and related rights,trade marks, logos, service marks, trade dress, business and domain names, rights in trade dress or get-up, rights ingoodwill or to sue for passing off, unfair competition rights, rights in designs, rights in computer software, databaserights, topography rights, moral rights, rights in confidential information (including know-how and trade secrets),methods and protocols for Services, and any other intellectual property rights, in each case whether capable ofregistration, registered or unregistered and including all applications for and renewals, reversions or extensions ofsuch rights, and all similar or equivalent rights or forms of protection in any part of the world.2.8 “Parties” means the Society and Client together.2.9 “Party” means the Society or the Client.2.10 “Register” means the public electronic register of ships updated regularly by the Society.2.11 “Rules” means the Society’s classification rules and other documents. The Society’s Rules take into accountat the date of their preparation the state of currently available and proven technical minimum requirements but arenot a standard or a code of construction neither a guide for maintenance, a safety handbook or a guide of professionalpractices, all of which are assumed to be known in detail and carefully followed at all times by the Client.2.12 “Services” means the services set out in clauses 2.2 and 2.3 but also other services related to Classificationand Certification such as, but not limited to: ship and company safety management certification, ship and port securitycertification, maritime labour certification, training activities, all activities and duties incidental thereto such asdocumentation on any supporting means, software, instrumentation, measurements, tests and trials on board. TheServices are carried out by the Society according to the applicable referential and to the Bureau Veritas’ Code ofEthics. The Society shall perform the Services according to the applicable national and international standards andIndustry Practice and always on the assumption that the Client is aware of such standards and Industry Practice.2.13 “Society” means the classification society ‘Bureau Veritas Marine & Offshore SAS’, a company organizedand existing under the laws of France, registered in Nanterre under number 821 131 844, or any other legal entity ofBureau Veritas Group as may be specified in the relevant contract, and whose main activities are Classification andCertification of ships or offshore units.2.14 “Unit” means any ship or vessel or offshore unit or structure of any type or part of it or system whether linkedto shore, river bed or sea bed or not, whether operated or located at sea or in inland waters or partly on land, includingsubmarines, hovercrafts, drilling rigs, offshore installations of any type and of any purpose, their related and ancillaryequipment, subsea or not, such as well head and pipelines, mooring legs and mooring points or otherwise as decidedby the Society.

3. SCOPE AND PERFORMANCE3.1 Subject to the Services requested and always by reference to the Rules, the Society shall:• review the construction arrangements of the Unit as shown on the documents provided by the Client;• conduct the Unit surveys at the place of the Unit construction;• class the Unit and enter the Unit’s class in the Society’s Register;• survey the Unit periodically in service to note whether the requirements for the maintenance of class are met.The Client shall inform the Society without delay of any circumstances which may cause any changes on theconducted surveys or Services.3.2 The Society will not:• declare the acceptance or commissioning of a Unit, nor its construction in conformity with its design, suchactivities remaining under the exclusive responsibility of the Unit’s owner or builder;• engage in any work relating to the design, construction, production or repair checks, neither in the operation ofthe Unit or the Unit’s trade, neither in any advisory services, and cannot be held liable on those accounts.

4. RESERVATION CLAUSE4.1 The Client shall always: (i) maintain the Unit in good condition after surveys; (ii) present the Unit for surveys;and (iii) inform the Society in due time of any circumstances that may affect the given appraisement of the Unit orcause to modify the scope of the Services.4.2 Certificates are only valid if issued by the Society.4.3 The Society has entire control over the Certificates issued and may at any time withdraw a Certificate at itsentire discretion including, but not limited to, in the following situations: where the Client fails to comply in due timewith instructions of the Society or where the Client fails to pay in accordance with clause 6.2 hereunder.4.4 The Society may at times and at its sole discretion give an opinion on a design or any technical element thatwould ‘in principle’ be acceptable to the Society. This opinion shall not presume on the final issuance of any Certificateor on its content in the event of the actual issuance of a Certificate. This opinion shall only be an appraisal made bythe Society which shall not be held liable for it.

5. ACCESS AND SAFETY5.1 The Client shall give to the Society all access and information necessary for the efficient performance of therequested Services. The Client shall be the sole responsible for the conditions of presentation of the Unit for tests,trials and surveys and the conditions under which tests and trials are carried out. Any information, drawing, etc.required for the performance of the Services must be made available in due time.5.2 The Client shall notify the Society of any relevant safety issue and shall take all necessary safety-relatedmeasures to ensure a safe work environment for the Society or any of its officers, employees, servants, agents orsubcontractors and shall comply with all applicable safety regulations.

6. PAYMENT OF INVOICES6.1 The provision of the Services by the Society, whether complete or not, involve, for the part carried out, thepayment of fees thirty (30) days upon issuance of the invoice.

Bureau Veritas Marine & Offshore Genera

6.2 Without prejudice to any other rights hereunder, in case of Client’s payment default, the Society shall be entitledto charge, in addition to the amount not properly paid, interests equal to twelve (12) months LIBOR plus two (2) percent as of due date calculated on the number of days such payment is delinquent. The Society shall also have theright to withhold Certificates and other documents and/or to suspend or revoke the validity of Certificates.6.3 In case of dispute on the invoice amount, the undisputed portion of the invoice shall be paid and an explanationon the dispute shall accompany payment so that action can be taken to solve the dispute.

7. LIABILITY7.1 The Society bears no liability for consequential loss. For the purpose of this clause consequential loss shallinclude, without limitation:• Indirect or consequential loss;• Any loss and/or deferral of production, loss of product, loss of use, loss of bargain, loss of revenue, loss of profitor anticipated profit, loss of business and business interruption, in each case whether direct or indirect.The Client shall defend, release, save, indemnify, defend and hold harmless the Society from the Client’s ownconsequential loss regardless of cause.7.2 Except in case of wilful misconduct of the Society, death or bodily injury caused by the Society’s negligenceand any other liability that could not be, by law, limited, the Society’s maximum liability towards the Client is limitedto one hundred and fifty per-cents (150%) of the price paid by the Client to the Society for the Services having causedthe damage. This limit applies to any liability of whatsoever nature and howsoever arising, including fault by theSociety, breach of contract, breach of warranty, tort, strict liability, breach of statute.7.3 All claims shall be presented to the Society in writing within three (3) months of the completion of Services’performance or (if later) the date when the events which are relied on were first discovered by the Client. Any claimnot so presented as defined above shall be deemed waived and absolutely time barred.

8. INDEMNITY CLAUSE8.1 The Client shall defend, release, save, indemnify and hold harmless the Society from and against any and allclaims, demands, lawsuits or actions for damages, including legal fees, for harm or loss to persons and/or propertytangible, intangible or otherwise which may be brought against the Society, incidental to, arising out of or inconnection with the performance of the Services (including for damages arising out of or in connection with opinionsdelivered according to clause 4.4 above) except for those claims caused solely and completely by the grossnegligence of the Society, its officers, employees, servants, agents or subcontractors.

9. TERMINATION9.1 The Parties shall have the right to terminate the Services (and the relevant contract) for convenience aftergiving the other Party thirty (30) days’ written notice, and without prejudice to clause 6 above.9.2 In such a case, the Classification granted to the concerned Unit and the previously issued Certificates shall remainvalid until the date of effect of the termination notice issued, subject to compliance with clause 4.1 and 6 above.9.3 In the event where, in the reasonable opinion of the Society, the Client is in breach, or is suspected to be inbreach of clause 16 of the Conditions, the Society shall have the right to terminate the Services (and the relevantcontracts associated) with immediate effect.

10. FORCE MAJEURE10.1 Neither Party shall be responsible or liable for any failure to fulfil any term or provision of the Conditions if andto the extent that fulfilment has been delayed or temporarily prevented by a force majeure occurrence without the faultor negligence of the Party affected and which, by the exercise of reasonable diligence, the said Party is unable toprovide against.10.2 For the purpose of this clause, force majeure shall mean any circumstance not being within a Party’sreasonable control including, but not limited to: acts of God, natural disasters, epidemics or pandemics, wars, terroristattacks, riots, sabotages, impositions of sanctions, embargoes, nuclear, chemical or biological contaminations, lawsor action taken by a government or public authority, quotas or prohibition, expropriations, destructions of the worksite,explosions, fires, accidents, any labour or trade disputes, strikes or lockouts.

11. CONFIDENTIALITY11.1 The documents and data provided to or prepared by the Society in performing the Services, and the informationmade available to the Society, are treated as confidential except where the information:• is properly and lawfully in the possession of the Society;• is already in possession of the public or has entered the public domain, otherwise than through a breach of thisobligation;• is acquired or received independently from a third party that has the right to disseminate such information;• is required to be disclosed under applicable law or by a governmental order, decree, regulation or rule or by astock exchange authority (provided that the receiving Party shall make all reasonable efforts to give prompt writtennotice to the disclosing Party prior to such disclosure.11.2 The Parties shall use the confidential information exclusively within the framework of their activity underlyingthese Conditions.11.3 Confidential information shall only be provided to third parties with the prior written consent of the other Party.However, such prior consent shall not be required when the Society provides the confidential information to asubsidiary.11.4 Without prejudice to sub-clause 11.1, the Society shall have the right to disclose the confidential information ifrequired to do so under regulations of the International Association of Classifications Societies (IACS) or any statutoryobligations.

12. INTELLECTUAL PROPERTY12.1 Each Party exclusively owns all rights to its Intellectual Property created before or after the commencementdate of the Conditions and whether or not associated with any contract between the Parties.12.2 The Intellectual Property developed by the Society for the performance of the Services including, but not limitedto drawings, calculations, and reports shall remain the exclusive property of the Society.

13. ASSIGNMENT13.1 The contract resulting from to these Conditions cannot be assigned or transferred by any means by a Party toany third party without the prior written consent of the other Party.13.2 The Society shall however have the right to assign or transfer by any means the said contract to a subsidiaryof the Bureau Veritas Group.

14. SEVERABILITY14.1 Invalidity of one or more provisions does not affect the remaining provisions.14.2 Definitions herein take precedence over other definitions which may appear in other documents issued by theSociety.14.3 In case of doubt as to the interpretation of the Conditions, the English text shall prevail.

15. GOVERNING LAW AND DISPUTE RESOLUTION15.1 These Conditions shall be construed and governed by the laws of England and Wales.15.2 The Parties shall make every effort to settle any dispute amicably and in good faith by way of negotiation withinthirty (30) days from the date of receipt by either one of the Parties of a written notice of such a dispute.15.3 Failing that, the dispute shall finally be settled under the Rules of Arbitration of the Maritime Arbitration Chamberof Paris (“CAMP”), which rules are deemed to be incorporated by reference into this clause. The number of arbitratorsshall be three (3). The place of arbitration shall be Paris (France). The Parties agree to keep the arbitrationproceedings confidential.

16. PROFESSIONAL ETHICS16.1 Each Party shall conduct all activities in compliance with all laws, statutes, rules, economic and trade sanctions(including but not limited to US sanctions and EU sanctions) and regulations applicable to such Party including butnot limited to: child labour, forced labour, collective bargaining, discrimination, abuse, working hours and minimumwages, anti-bribery, anti-corruption, copyright and trademark protection, personal data protection (https://personaldataprotection.bureauveritas.com/privacypolicy).Each of the Parties warrants that neither it, nor its affiliates, has made or will make, with respect to the mattersprovided for hereunder, any offer, payment, gift or authorization of the payment of any money directly or indirectly, toor for the use or benefit of any official or employee of the government, political party, official, or candidate.16.2 In addition, the Client shall act consistently with the Bureau Veritas’ Code of Ethics.https://group.bureauveritas.com/group/corporate-social-responsibility

l Conditions – Edition September 2018

GUIDANCE NOTE NI 432

NI 432Certification of Fibre Ropes for

Deepwater Offshore Services

SECTION 1 GENERAL

SECTION 2 CERTIFICATION SCHEME

SECTION 3 QUALIFICATION OF FIBRE MATERIAL

SECTION 4 ROPE DESIGN AND MANUFACTURING

SECTION 5 QUALITY CONTROL ACTIVITIES

SECTION 6 ROPE PROTOTYPE TESTING

APPENDIX 1 ROPES FOR STATION-KEEPING: DESIGN AND OPERATING CRITERIA

APPENDIX 2 TEMPLATES FOR DATA SHEET

APPENDIX 3 ROPE TESTING

December 2018

Section 1 General

1 General 5

1.1 Scope1.2 Field of application1.3 Certification conditions1.4 Definitions1.5 Reference documents

Section 2 Certification Scheme

1 Process of Certification 7

1.1 General1.2 Certification activities1.3 Documentation to be submitted

Section 3 Qualification of Fibre Material

1 Fibre for rope core 9

1.1 General

2 Fibre for braided rope cover 9

2.1 General

Section 4 Rope Design and Manufacturing

1 Rope design 10

1.1 General1.2 Rope construction1.3 Materials1.4 Rope core1.5 Protective cover1.6 Particle ingress protection

2 Rope manufacturing 11

2.1 General

3 Terminations 11

3.1 General

4 Length of finished rope 11

4.1 General

5 Marking 12

5.1 General

2 Bureau Veritas December 2018

Section 5 Quality Control Activities

1 General 13

1.1 Inspection, testing and quality plan1.2 Rope samples1.3 Rope testing

Section 6 Rope Prototype Testing

1 General 14

1.1 Scope

2 Breaking test 14

2.1 General2.2 Strength2.3 Tenacity2.4 End-of bedding-in axial stiffness

3 Load-elongation measurements and response in torsion 15

3.1 Rope length3.2 Quasi-static and dynamic axial stiffness3.3 Response in torsion

4 Creep 15

4.1 HMPE ropes

5 Endurance and durability 15

5.1 Cyclic Tension-Tension loading endurance5.2 Axial compression fatigue5.3 Particle ingress protection

6 Sub-sea lowering lines and other applications 16

6.1 General6.2 CBOS performance6.3 Other applications

Appendix 1 Ropes for Station-Keeping: Design and Operating Criteria

1 General 17

1.1 Subject

2 Arrangement of Mooring System 17

2.1 Lay-out2.2 Torsional behaviour2.3 Line top section2.4 Line bottom section2.5 Rope protection

3 Design criteria (in-place system) 18

3.1 Strength (maximum tension)3.2 Minimum tension in leeward line3.3 Endurance under cyclic Tension-Tension loading3.4 Creep

December 2018 Bureau Veritas 3

4 Installation, Operation and Inspection 18

4.1 Installation4.2 Re-tensioning4.3 Inspection of rope4.4 Creep monitoring

5 Load-elongation of fibre ropes 19

5.1 General5.2 Model5.3 Elongation under permanent load5.4 Stiffness5.5 “Quasi-static” stiffness5.6 Dynamic stiffness5.7 Data for polyester ropes

6 Reference documents 22

6.1 Proceedings of the Offshore Technology Conference (OTC)6.2 Proceedings of the Rio Oil & Gas conference (IBP)6.3 Proceedings of the International Conference on Ocean, Offshore and Artic

Engineering (OMAE)

Appendix 2 Templates for Data Sheet

Appendix 3 Rope Testing

1 General 26

1.1 Subject

2 Testing conditions 26

2.1 Testing equipment2.2 Condition of rope samples2.3 Recording

3 Testing sequences 27

3.1 General3.2 Breaking test3.3 Linear density test3.4 Creep test

4 Stiffness tests and measurement 28

4.1 Testing conditions4.2 Testing sequence – Case 14.3 Testing sequence - Case 24.4 Testing sequence - Case 34.5 Recording

5 Endurance tests 29

5.1 Tension-Tension cyclic loading endurance test5.2 Axial compression fatigue

6 Other tests 29

6.1 Response in torsion6.2 Particle ingress protection


NI 432, Sec 1

SECTION 1 GENERAL

1 General

1.1 Scope

1.1.1 This Guidance Note defines the procedures andrequirements for the certification of fibre ropes intended foruse as load-bearing components in the station-keeping sys-tem of a floating offshore unit, or for other offshore deepwa-ter applications, as defined in [1.2].

Note 1: The term “deepwater” is used here as illustrative of the cur-rent field of application of ropes in the offshore industry, in systemswhere the rope is a “critical component” for safety or asset integ-rity. However, it is not meant as a limitation, neither on the serviceconditions of ropes nor on the scope of this Guidance Note.

Note 2: For the related design and operating criteria of mooringsystems and information on the background of certification require-ment, reference is made to App 1.

1.2 Field of application

1.2.1 Fibre ropes for station-keeping systems

This Guidance Note is applicable to fibre ropes used as ele-ments of anchoring lines for the station-keeping of perma-nent floating offshore platforms or mobile floating offshoreunits, at their operating site, or similar applications andmade of fibres as per Sec 3, [1.1.1].

The conditions and criteria for use of fibre ropes in a sta-tion-keeping system are defined in App 1.

Note 1: The certification of ropes is to be generally performed as apart of activities for the classification of an offshore unit, and thegranting of a POSA notation covering the station-keeping system ofthat unit (as per NR493, see [1.5.1]).

Note 2: This Guidance Note covers the compliance of ropes to ISO18692 (see [1.5.2]), and related rope certification.

1.2.2 Tethers

This Guidance Note is also applicable to fibre ropes used insimilar conditions as anchoring lines (i.e. free spanningbetween terminations) such as tension members (tethers) insubsurface systems.

The provisions indicated for station-keeping lines are gener-ally applicable to such ropes.

1.2.3 Sub-sea lowering and other applications

Subject to adjustments of the technical requirements onrope design and to adequate testing, this Guidance Note isalso applicable to fibre ropes used for:

• sub-sea lowering lines for a (deepwater) fibre rope han-dling system, and

• other offshore “deepwater” applications.

Some guidance is given for such ropes.

1.2.4 Limits of scope

This Guidance Note may be referred to when agreed byinvolved parties.

However, this Guidance Note is in principle not intended tocover the certification of synthetic fibre ropes for othermarine applications, such as:

• single point mooring (SPM) hawsers

• FSRU mooring lines

• towing lines, mooring lines (ship to terminal, ship to ship).

Note 1: The type approval and inspections of SPM hawsers is nor-mally performed with reference to the OCIMF guidelines (see [1.5.3]).

Note 2: The type approval (if requested) and the inspections ofropes for other services is performed based on applicable Rules,with reference to recognised product standards (such as ISO stand-ards or Cordage Institute documents).

Note 3: NI 658 is however applicable to fibre qualification for suchapplications.

1.2.5 Termination fittings

Termination fittings, such as thimbles or similar devices arecovered in this Guidance Note only for their interface prop-erties with rope and for testing (see Sec 4, [3] and App 3).

Shackles or other connecting devices are not covered bythis Guidance Note.

Note 1: When requested and/or for classification purpose, referenceis to be made to the relevant provisions of NR493 (see [1.5.1]).

1.3 Certification conditions

1.3.1 The certification activities defined in Sec 2 are carriedout within the framework of Bureau Veritas Marine & Off-shore - General Conditions.

1.3.2 The certification scheme defined in Sec 2 and relatedrequirements within this Guidance Note are based on thepresent State of the Art in using fibre ropes for the applica-tions defined in [1.2].

The Society reserves the right to modify the content of thisscheme or associated requirements, or to call for specificrequirements for a particular product or usage or servicecondition.

1.3.3 In addition to the requirements of this Guidance Notes,the certification activities are performed with reference to:

• other publications of Bureau Veritas, as applicable (see[1.5.1])


NI 432, Sec 1

• ISO 18692-1, and other ISO documents defined in[1.5.2], as relevant:

- ISO 18692-2, (Polyester)

- ISO 18692-3, (HMPE)

- ISO TS 17920, (Aramid)

- ISO TS 19936, (Polyarylate).

Reference can also be made to specific requirements of Pur-chaser's specification, where applicable.

1.4 Definitions

1.4.1 In addition to the definition of MBS, rope model andrope size listed in [1.4.2] to [1.4.4], further relevant defini-tion can be found in ISO 18692 and, for general vocabu-lary, in ISO 1968 (see [1.5.2]).

1.4.2 Minimum Breaking Strength (MBS)

The MBS of the rope is defined as the specified minimumfor the tension at break of a rope, when tested following theprocedure defined in this Guidance Note.

Note 1: The MBS is thus defined as that of the spliced (terminated)rope).

1.4.3 Rope model

Rope model means a set of ropes having, over a range ofsizes, common characteristics including fibre and othermaterials, construction and method of manufacture for therope core, the cover, and the terminations, and dimensionalcharacteristics such that a rope in one size can be consid-ered as homothetic to a rope of another size.

Note 1: A rope model generally corresponds to a product in a Man-ufacturer's catalogue, provided same fibre(s) and other materialsare used.

Note 2: Two ropes of the same model have, in principle, the samenumber of elements (strands, sub-ropes …) and all dimensions(diameters, lay length …) in same proportion or, for a parallel con-struction, can be made of a different number of identical sub-ropes.

Note 3: The acceptance, for the purpose of rope approval, of sev-eral ropes being of “the same model” is subject to the prior agree-ment of the Society (see Sec 2, [1.1.2] and Sec 6, [1.1.3]).

1.4.4 Rope sizeRope size means nominal dimension (e.g. diameter, or cir-cumference) of the cross section of a rope, or a reference num-ber (in ISO rope standards), or the resulting MBS of that rope.Note 1: For the purpose of this Guidance Note, the MBS is gener-ally used to indicate rope size.

1.5 Reference documents

1.5.1 Bureau Veritas documentsNR320 − Certification scheme of materials and equipmentfor the classification of marine units

NR266 − Requirements for survey of materials and equip-ment for the classification of ships and offshore units

NR216 − Rules for materials and welding for the classifica-tion of marine units

NR493 − Classification of mooring systems for permanentoffshore units

NI 658 − Type approval of fibres and yarns for the manufac-turing of fibre ropes.

1.5.2 ISO documentsISO 1968 − 2004 − Fibre ropes and cordage - Vocabulary

ISO 18692-1 − 2018 − Fibre ropes for offshore station-keep-ing - Part 1: General specification

ISO 18692-2 − 2018 − Fibre ropes for offshore station-keep-ing - Part 2: Polyester

ISO 18692-3 − Fibre ropes for offshore station-keeping -Part 3: High Modulus Polyethylene (HMPE) - (currently ISOTS 14909 − 2011)

ISO/TS 17920 − 2015 − Fibre ropes for offshore station-keeping - Aramid

ISO/TS 19336 − 2015 − Fibre ropes for offshore station-keeping - Polyarylate

1.5.3 Other documentsOCIMF − 2000 − Guidelines for the purchasing and testingof single point mooring hawsers

Cordage Institute − CI 1503-09 − Test Method for Yarn-on-Yarn Abrasion


NI 432, Sec 2

SECTION 2 CERTIFICATION SCHEME

1 Process of Certification

1.1 General

1.1.1 The certification of ropes intended for a given projectinvolves the following steps to be carried out:

a) Qualification of the fibre material, resulting in a TypeApproval of the fibre, usually with the fibre Manufac-turer (see Sec 3).

b) Qualification of the rope based on the design, manufac-turing, and testing of a full size prototype of the speci-fied rope, and resulting in a Type Approval of the rope(See Sec 4, Sec 5 and Sec 6).

This Type Approval will be valid for the manufacturingof ropes that are identical, in rope model (i.e. includingfibre(s)) and in rope size, to the rope that has been pro-totype tested.

c) Manufacturing in conformity to prototype and testing ofropes for supply.

Note 1: For further manufacturing, the qualification does not needto be repeated when the ropes are identical to a rope already hold-ing a Type Approval, i.e. no change is made to materials, design,nor manufacturing process.

1.1.2 During qualification, account is taken, subject toagreement by the Society at time of the review of ropedesign and manufacturing specifications, of test results frompreviously qualified ropes of the same model, holding aType Approval by the Society (see Sec 6, [1.1.3]).

Note 1: In practice, the rope for a given project is most often not aunique product, but one size in a rope model proposed by theManufacturer, with other size(s) of the same rope model havingbeen already qualified.

1.2 Certification activities

1.2.1 Certification activities generally include the following:

a) For rope qualification:

• review of design and manufacturing documents

• review of fibre certification status (see Sec 4)

• visits during the manufacturing of a prototype ropeand the preparation of rope samples for testing

• witnessing of prototype testing

• review of manufacturing and testing reports

• issuance of a Type Approval Certificate upon satis-factory completion of the procedure

• assessment of manufacturing facilities and issuanceof a recognition certificate upon satisfactory com-pletion of the procedure (BV mode II survey asdefined in NR 320).

b) For the production of ropes in accordance with the ropeapproval:• attendance to tests and examinations as agreed for

individual supplies• visits during manufacturing of ropes• visits during rope testing (where applicable)• issuance of a certificate of inspection for the individual

supply upon satisfactory completion of the procedure.

c) During both steps:• inspection at suppliers works, as needed.

1.3 Documentation to be submitted

1.3.1 The Manufacturer is to submit the following docu-mentation, in due time:

a) At time of application for rope qualification:• summary of rope design, (see [1.3.2])• related production plans (when applicable)• Manufacturer’s brochures and catalogues of prod-

ucts (for information).

b) For rope qualification:

1) At start of qualification:• quality management system certificates• data of intended material (type, Supplier, and grade)• plans for prototype testing with, for any request

of test dispensation, reference to previouslyobtained Type Approval(s) for the same model ofrope (see Sec 6, [1])

• detailed planning for design activities, prototypemanufacturing, prototype testing, and subse-quent rope manufacturing.

2) Before manufacturing and testing:• Manufacturer's design and manufacturing speci-

fications• quality plan covering all steps of manufactur-

ing, inspection and testing• detailed testing procedures• plans and specifications for the purchase of

thimbles and fittings (if any) and relevant TACdocumentation

• list of Quality control procedures• testing reports (when available).

3) After prototype testing• prototype testing reports.

c) For the production of ropes in accordance with the TypeApproval:• rope supply data sheet (see [1.3.4])• inspection and Test Plans• testing reports (where applicable and when available).


NI 432, Sec 2

1.3.2 Summary of rope designA Summary of rope design is to provide a general descrip-tion of the rope to be qualified, including:• identification of product (rope model)• type of service• material (with fibre designation)• type of construction, including type of torque behaviour• type of protective cover and particle ingress protection• type of terminations• specified MBS and rope diameter• reference assembly and interface drawings.

An example of template for the Summary of rope design isgiven in App 2, Tab 1.

1.3.3 Design and Manufacturing SpecificationsThe detailed design and manufacturing specifications are toinclude:• specifications of materials• details of rope construction (see Sec 4, [1.2])• details of rope protection• details of terminations• specification of thimbles• manufacturing specifications, of rope and terminations

including production sheets, and relevant procedures• marking information• quality control procedures, Inspection plans, and report

forms.

An example of data sheet for details of rope construction isgiven in App 2, Tab 2.Note 1: These detailed design and manufacturing documents arekept as confidential, unless otherwise agreed between involvedparties.

1.3.4 Rope supply data sheet

A Rope supply data sheet is to provide a general descriptionof the intended supply, including:

• identification of product (rope model)

• type of service and other information on rope serviceconditions, as provided by Purchaser

• specified MBS and diameter

• reference Type Approval, with a Statement of Compli-ance by the Manufacturer

• material (with fibre designation)

• type of construction, including type of torque behaviour

• protective cover and particle ingress protection information

• type of terminations

• assembly and interface drawings

• scope of supply (for information and interface with clas-sification activities)

• number and length of finished ropes in the supply.

An example of template for Rope supply data sheet is givenin App 2, Tab 3.

1.3.5 Manufacturing records

Full fabrication files are to be made available to Surveyor, atfactory, including, as a minimum:

• material certificates

• production sheets

• records of controls and inspections

• testing records.


NI 432, Sec 3


SECTION 3 QUALIFICATION OF FIBRE MATERIAL

1 Fibre for rope core

1.1 General

1.1.1 The following fibre materials are currently used (orconsidered) for the rope core (i.e. the load-bearing part ofthe rope - see Sec 4, [1.4]), and form the basis of this Guid-ance Note:

• Polyester (high tenacity, marine grade)

• High Modulus Polyethylene (HMPE)

• Aramid and Polyarylate.

Other fibre materials and yarns made of several materials(dual fibre yarns) will be given special consideration by theSociety, based on their particular properties and intendedapplication.

1.1.2 The fibre is to be qualified and Type Approved by theSociety with respect to the provisions of this GuidanceNote, following the requirements and procedures of NI 658(see Sec 1, [1.5.1]).

Compliance with Ni 658 is to include the specific provi-sions applicable to deepwater mooring lines or other spe-cific offshore applications.

Fabricated yarns are to be Type Approved on the same basis.

Note 1: The Type Approval is to be obtained by the fibre Manufac-turer. In case of fabricated or re-processed fibre, the Type Approvalis to be obtained by the rope Manufacturer.

1.1.3 The fibre for the rope core is to be high tenacity fibre,with a tenacity not lower than:• 0,78N/Tex for Polyester fibres• 2,5N/Tex for High Modulus Polyethylene (HMPE) fibres• 1,8N/Tex for Aramid and Polyarylate fibres.

1.1.4 The fibre is to be marine grade fibre, i.e. fibre pro-vided with a marine finish having documented efficiencyand persistence, as per NI 658.Note 1: The provisions on marine finish are however not applica-ble to HMPE.

1.1.5 Fibres and fabricated yarns are to be delivered with awork’s certificate stating compliance with the TypeApproval (such as type 3.1 as per EN10204 − 2004), asdetailed in the document referred to in [1.1.2]. When theproduct is for internal use, same information is to be givenin a test report.

2 Fibre for braided rope cover

2.1 General

2.1.1 The fibre for a braided rope cover (see Sec 4, [1.5]) isto have documented properties, in accordance NI 658 andthe general provisions for “marine application” therein. A Type Approval should be obtained by the manufacturer.

The fibre is to be delivered with a work’s certificate statingcompliance with the Type Approval.

2.1.2 A polyester fibre used for a braided cover is to have aminimum tenacity of 0,73 N/tex.

NI 432, Sec 4

SECTION 4 ROPE DESIGN AND MANUFACTURING

1 Rope design

1.1 General

1.1.1 The rope design is to be identified in all details,including materials, arrangement, method of manufacture,as well as numerical data (e.g. sizes, numbers, dimensionssuch as twist or lay-length) for the proposed rope size.

1.2 Rope construction

1.2.1 Ropes for station-keeping, and other ropes unlessotherwise specified, are to comprise a rope core, as theload-bearing part of the rope, and a protective cover.

For sub-sea lowering lines or other specific applications, anopen construction, without cover, is to be used.

The constructions of rope core and of rope cover are to beidentified in all details. The mass and dimensional charac-teristics of the rope are to be also defined.Note 1: An example of data sheet for details of rope construction isgiven in App 2, Tab 2.

Note 2: For ropes for station-keeping, the diameter or the particu-lars of a specific (non-circular) cross section are given for informa-tion. The diameter is however an important parameter for someapplications (e.g. sub-sea lowering lines).

1.3 Materials

1.3.1 All materials entering in rope manufacturing are to beidentified and shall not be changed subsequently.

Fibres for rope core and for rope cover are to be in accord-ance with the relevant provisions of Sec 3.

Additional materials entering in the manufacturing of rope(e.g. filter, coating or lubricant) and terminations (e.g. lin-ing, coating) are to have identified nature and properties,including, as applicable:

• base material

• type of construction/preparation

• brand name / reference to a specification

• dimensional properties (e.g. thickness, linear density)

• strength and performance (e.g. filtering capability), withreference to standards appropriate for the product.

Note 1: The final acceptance of fibres and other materials for a givenrope is, in any case, pending the full size testing of prototype ropes.

1.4 Rope core

1.4.1 The rope core is to be of suitable construction to pro-vide intended strength and stiffness, meeting the perfor-mances specified in Sec 6, and other relevant properties ofthe rope.

The construction of rope core is to be such that the rope hasa defined torque behaviour, as suitable for the intendedapplication, being in principle one of the following:

• Torque-neutral construction:

a construction such that rope ends do not exert a torque,or tend to rotate, when the rope is tensioned.

Note 1: Some constructions are inherently torque-neutral.

• Torque-matched construction:

a construction such that, over a certain range of tension,the rope develops a similar torque to, and thus can bal-ance that of a given steel wire rope.

Note 2: The type and size of matched steel rope are to be specified.

Note 3: See App 1, [2.2] for application to station-keeping lines.For lowering/lifting lines working in single fall, an inherentlytorque-neutral construction must be used.

1.5 Protective cover

1.5.1 A protective cover, when applicable as per [1.2], is toprotect rope core from mechanical damages during han-dling and in service.

The cover is to be permeable, to permit flooding of voidspaces within the rope when immersed.

Note 1: In case of a parallel construction, the cover also has thefunction of holding rope core elements (sub-ropes) together.

1.5.2 A braided cover is typically used. The braided coveris to have a thickness not less than 7 mm when made of pol-yester yarns (see Sec 3, [2.1.2]) or, if another material isused, a thickness providing at least an equivalent level ofprotection.

Note 1: For ropes with diameter less than 100mm, the minimumcover thickness t, in mm, is taken as:

t = 0,07 ⋅ D

with t not to be less than 4 mm and D the nominal diameter in mm.

1.5.3 Coloured strands in a suitable pattern are to be pro-vided within the braiding, as a mean to verify that the ropehas not been twisted, during handling or in service.

Note 1: although this pattern is not intended as a colour coding, adistinctive pattern is current practice.

1.6 Particle ingress protection

1.6.1 For covered ropes, a particle ingress protection is toprovide a secondary barrier to avoid penetration of dust orsoil or other particles into the rope core (see App 1, [2.5]).

Note 1: This secondary barrier may be provided as an under-layerto the braided cover or other suitable arrangement.

A properly selected non-woven filtering material may be used. Thefiltering capability of material may be assessed by standard filteringtests, prior to the qualification test below.


NI 432, Sec 4

1.6.2 The particle ingress protection is to be able to preventthe ingress of particles with a size above a limit not exceed-ing 20 microns.

Note 1: a lower limit is easily achievable and may be specified. Seealso App 1, [2.5].

1.6.3 The arrangement and method of placement of theprotective cover are to be specified (see [3.1.3]). The effi-ciency of the particle ingress protection is to be verified bytesting in accordance with Sec 6, [5.3].

2 Rope manufacturing

2.1 General

2.1.1 Manufacturing specifications shall define each step of themanufacturing process, and associated setting of parameters.

Any particular aspect of manufacturing process is to be dulyidentified and covered by specifications and procedures.

The Society reserves the right to require specific documen-tation on any aspect of proposed practice.

2.1.2 Strands (i.e. rope core or sub-rope strands), sub-ropesand rope core are to be manufactured in a single lengthover each supplied rope, with no interruption, nor inter-change, nor splice.

Note 1: a longer length is normally made of several segments. Thecase of very long single length in large size, if needed (i.e. a ropewith a length above say 1000 m and a weight exceeding say 20 t),would be specially considered, subject to adequate validation tests.

2.1.3 The method for joining yarns and the staggering ofjoins are to be defined.

2.1.4 If a coating, a lubricant or other additive is addedduring some stage of manufacturing, the methods of prepa-ration and application are to be specified, and to be tracea-ble to a specification of the product.

2.1.5 A cover braiding may include properly staggeredstrand interchanges.

3 Terminations

3.1 General

3.1.1 Ropes are normally provided with spliced termina-tions, to suit a thimble or similar device.

Manufacturing specifications and procedures are to definedimensions of eye, splicing method, splice arrangement,and each step of the manufacturing process.

3.1.2 The type of material (type of steel or other material),diameter, and groove geometry of thimble are to be defined,and the manufacturing of termination is to suit that geometry.

For parallel construction ropes, the arrangement and match-ing of sub-rope splices are to be defined.

Note 1: to avoid that a damage (e.g. by cutting) of one sub-ropejeopardise the residual strength of the rope, one to one splicingshould be used.

For short rope length, the relative orientation between thesplices at each end is to be also defined, and kept identicalbetween samples for prototype testing, for production test-ing, and for supplied items with a length less than 70 m (e.g.inserts).

3.1.3 The cover and particle ingress protection are to berestored over the splice area, to ensure continuity of protection.

An additional lining is to be provided in the bearing area ofeye onto thimble.

Eye and splice are to be further protected by a polyurethanecoating.

Note 1: coating may be omitted for test samples.

3.1.4 Other termination systems would be given specialconsideration, when supported by extensive investigationsof strength and durability.

4 Length of finished rope

4.1 General

4.1.1 The length of finished ropes is defined as a bedded-inlength at a specified tension.

The bedded-in length LT0, in m of supplied ropes at a ten-sion T0 is obtained as:

LT0 = M / LDT0

where

M : The net mass of rope, in kg, obtained by weigh-ing, and corrected for ancillary weights and theadditional mass of material in terminations,

LDT0 : The linear density (mass per unit length, MTex)of the rope in a bedded-in condition at a ten-sion T0 (in% of MBS), obtained from the “linear-density test” specified in Sec 6, [3.1], followingthe procedure as per App 3, [3.3].

Note 1: Unless otherwise specified, T0 is taken as 20% of MBS andthe load sequence in App 3, [3.3] is used. If a different tension or adifferent bedding-in/pre-stretching sequence is used, these condi-tions are to be indicated in the rope supply data sheet (see also Sec6, [3.1] and App 1, [5.3]).

Note 2: Taking LD0 (see App 3, [3.3]) in the above formula, the “lengthat reference tension” L0 can be obtained (see also App 1, [5.3]).

Note 3: If another method than weighting is used to determine ropelength, the Manufacturer will have to document the relationbetween the length of finished rope in the specified conditions andthe length measurements performed during production.

4.1.2 The length of short ropes (such as rope samples orinserts) may be taken as the length measured at a referencetension of 2% of the rope MBS.

4.1.3 The length of finished ropes is to be within 1% of thespecified length.


NI 432, Sec 4

5 Marking

5.1 General

5.1.1 A name plate is to be affixed at a convenient locationat one end of each rope (be it a test sample of a part of thesupply) with, as a minimum, the following indications dura-bly marked:

• manufacturer identification• order and part number• rope core material• rope MBS• date (month, year) of production.

The name plate is stamped with the relevant Society mark-ing, at time of final inspection.


NI 432, Sec 5


SECTION 5 QUALITY CONTROL ACTIVITIES

1 General

1.1 Inspection, testing and quality plan

1.1.1 Inspection and testing activities are to be conductedby the Manufacturer, with the objectives of ensuring that:

• the prototype rope is conform to specifications, with anychange made during the course of approval, (in parame-ters that could affect quality of finished product), beingduly reflected by modification of the specifications andprocedures.

• produced ropes are in conformity with approved prototype.

1.1.2 A Quality plan, covering all steps of manufacturingand inspection, is to be prepared by the Manufacturer andsubmitted to the Society for review, together with corre-sponding procedures.

Note 1: The qualification of operators, particularly those employedin rope splicing, is to be addressed within quality procedures.

Note 2: A Quality plan usually covers a rope model and isreviewed accordingly.

1.1.3 Quality control checklists and report forms are to beprepared by the Manufacturer, following those in OCIMFGuidelines, Sec 1, [1.5.3] (duly modified to account forrope construction), or an equivalent practice.

1.2 Rope samples

1.2.1 Rope samples are to be taken from the production, atfollowing rates:

• during manufacturing of prototype rope, once in everylength of continuous production

• during manufacturing of ropes for delivery, once in thefirst length of continuous production, then at an agreedrate, not less than once every 70 t.

1.2.2 For each sample, a piece of rope is to be taken out,then set under a reference tension of 2% of MBS, so that asample with a length of about 2m (at the reference tension)can be marked, then cut.

Note 1: If, for large size ropes, the above tension cannot beachieved, a lower target may be set, not less than 100 kN, that is tobe duly specified in inspection and test records (see also App 3).

1.2.3 Measurements are to be taken, at the reference ten-sion, of:

• rope outside diameter

• length and weight of rope sample

• weight of rope core of the sample

• cover thickness.

The linear density of rope and of rope core are to be calcu-lated from the weight of sample and its length at the refer-ence tension.

Note 1: The rope diameter is generally given for information, andmay be measured by an appropriate measuring device (e.g. a PItape). Where diameter is deemed an important parameter, the effec-tive maximum outside diameter should be measured with a calliper.

1.2.4 Samples are to be opened and inspected for conform-ity to design (number of components at each level, pitch orlay length of cover, sub-ropes and strands).

1.2.5 Yarn re-testing and recalculation of rope strength arenot required at this stage, and if performed as part of theManufacturer's Quality Control procedures, are not to beused to advocate another breaking strength than the Mini-mum Break Strength given in rope specifications.

Note 1: Such testing however provides useful information for laterreference (see App 1, [4.3]).

1.3 Rope testing

1.3.1 For rope approval, testing of prototype ropes is to beperformed in accordance with the provisions of Sec 6.

1.3.2 When a rope has been previously qualified, a break-ing test is to be performed on one rope sample taken fromthe on-going manufacturing, for Qr verification.

The breaking test is to be performed following the same pro-cedure as for prototype rope (see Sec 6, [2] and App 3) andthe result (the tension Tb at rope breaking) is to be abovethe specified MBS.

Besides, the rope core tenacity is to be not less than speci-fied for prototype in Sec 6, [2.3].

Note 1: A measurement of the end of bedding-in stiffness is nor-mally not required in the present test, not dispensing however fromthe bedding-in sequence, before testing to break.

Note 2: Test is not required for the production immediately follow-ing rope qualification tests.

NI 432, Sec 6

SECTION 6 ROPE PROTOTYPE TESTING

1 General

1.1 Scope

1.1.1 Testing of a prototype rope is to be performed, withthe objectives of verifying the breaking strength and otherproperties of the proposed rope.

1.1.2 The tests for the breaking strength and those for otherproperties, unless otherwise specified below, are to be per-formed on full size samples of the prototype rope. The testsqualify proposed rope and other ropes that are identical, i.e.of the same model (see Sec 1, [1.4.2]) and size as tested.

1.1.3 When data is available from the previous qualifica-tion tests of another rope (or other ropes) of the same modelbut a different size, to which a Type Approval has beengranted by the Society, some of the tests need not be per-formed. This is however subject to prior agreement by theSociety, based on a review of all characteristics, includingconstruction parameters of both ropes, and to the condi-tions specified below for each test.Note 1: The Society may also give consideration, if relevant, tosome tests performed for a different but similar model, provided itcan be established as an evidence that results are not affected bythe differences.

1.1.4 A plan for prototype testing is to be prepared andsubmitted to the Society, for review and agreement, at thetime of the request for rope approval.For ropes for station-keeping, and other ropes unless other-wise specified, the testing is to include, as a minimum, thetests defined in [2] to [5], as applicable, taking into accountthe accepted results of earlier tests (see [1.1.3]).

For sub-sea lowering lines and other applications, see [6].

1.1.5 A provision is to be made of spare rope for possibleretesting, in addition to the number of samples for therequired tests.

1.1.6 Rope samples for break test and cyclic loading endur-ance test are to be provided with the specified thimbles, ormounted on equivalent fittings (see App 3, [2.2]).Note 1: For a roller thimble, such testing with rope qualifies thethimble, provided the diameter of the pin hole is not exceeding 1,3that of the final thimble. For thimble qualification in other cases,reference is made to NR493, Sec 4.

1.1.7 Tests are to be performed on a testing machine withadequate capacity, stroke, control and recording systems,for the test sequences defined in App 3, and having docu-mented calibration.

1.1.8 When tests have been performed, a complete anddetailed report of testing issued by the testing laboratory isto be provided for review. This report is to include identifi-

cation of rope samples, all details of sample characteristicsand mounting, with sketches and pictures, and the recordsof load-elongation measurements (see App 3, [2.3]).

2 Breaking test

2.1 General

2.1.1 For prototype testing, a breaking test (i.e. loading upto the actual breaking of rope) is to be performed, on threesamples, following the procedure as per App 3.

2.2 Strength

2.2.1 When, for all three breaking tests defined in [2.1]:• the measured tensions at rope breaking Tb, in kN, are

above the specified MBS, the rope is deemed to havethat MBS.

• one of the measured Tb is below the specified MBS, theresult can be discarded only if the cause is identified, sothat remedial action can be taken.Then, two additional tests have to be performed and, forthe rope being deemed to have the specified MBS, bothmeasured Tb are to be above that MBS.

Note 1: A test failure may be due to a malfunction of the testmachine, or may be due to the rope. In the later case, changes torope design may need to be made that, if substantial, could lead toa complete re-run of all tests being required.

Note 2: Adjusting the breaking strength, upward or downward,form test results is not permitted (see App 1, [3.1]).

2.3 Tenacity

2.3.1 For each breaking test defined in [2.1]the rope coretenacity T, in N/Tex, is obtained from:T = Tb / LDC0

where:Tb : Tension at rope breaking, in kNLDC0 : Linear density of rope core at the reference ten-

sion of 2% of MBS, in kTex. (see [3.1] and App3, [3.3], or Sec 5, [1.2.3] when applicable).

2.3.2 For ropes intended for station-keeping purpose, therope core tenacity is to be not less than, for all breaking tests:• 0,47 N/Tex for Polyester fibres• 1,30 N/Tex for HMPE fibres• 0,90 N/Tex for aramid and polyarylate fibres.

2.4 End-of bedding-in axial stiffness

2.4.1 The dynamic stiffness at end of bedding-in “Krebi”(see App 3, [3.1]) is obtained during each test.


NI 432, Sec 6

For polyester ropes for station-keeping, Krebi is to bebetween 18 and 28.Note 1: Measurement of Krebi is for comparison (see App 1, [5.6]).Krebi is not meant to be a stiffness for utilisation in design.

Another range may be specified. (See App 3, [3.3]).

Note 2: For other materials and applications, and if a specific rangeis not defined, Krebi is to be measured for information.

3 Load-elongation measurements and response in torsion

3.1 Rope length

3.1.1 A “linear-density test” is to be performed at time ofprototype testing, on one sample, following the procedurein App 3.This test provides load-elongation data, then the linear den-sity LDT0 of the rope in a bedded-in condition under tensionT0, from which the bedded-in length LT0 of supplied ropes attension T0 is obtained (see Sec 4, [4.1.1] and App 1, [5.3]).Note 1: When another loading sequence than used at time of qual-ification test is anticipated, the corresponding load-elongationmeasurements may be performed on a sub-rope. See App 3, [3.3].

Note 2: For ropes other than polyester ropes for station-keeping, inapplications where knowledge of the as-installed length is deemedless essential, and subject to Society agreement, either the load-elongation results of a previous qualification test performed on arope of the same model, or measurements on a sub-rope (see App3, [3.3]) may be used.

3.2 Quasi-static and dynamic axial stiffness

3.2.1 The load-elongation properties of rope under variableloading, i.e. the rope quasi-static and dynamic axial stiff-ness (see App 1, [5]) are to be verified at time of prototypetesting, following the procedure in App 3.These tests need not be performed when data is available fromthe previous qualification test of another rope with the samemodel of rope core, and a diameter not less than 150 mm.

3.2.2 Tests may be performed on a separate rope sample, oras an intermediate sequence within the breaking test, eitherall on the same sample or by distributing the measurementsover the three test samples, as detailed in App 3.Note 1: These tests are minimum tests, when the stiffness for ropes witha given fibre has been adequately characterised (see App 1, [5.4]).

3.2.3 If required, or if data for some particular service condi-tions are needed, further tests should be conducted, that canbe performed on a sub-rope, in case of a parallel construction.

3.3 Response in torsion

3.3.1 For ropes that are not inherently torque neutral, theresponse in torsion is to be verified at time of prototype test-ing, by testing on one sample, following the applicable pro-cedure and the criteria in ISO 18692-1, as quoted in App 3.

3.3.2 Such a test needs not be performed when data isavailable from the previous qualification test of anotherrope with the same model of rope core and termination,and a diameter not less than 150 mm.

4 Creep

4.1 HMPE ropes

4.1.1 For HMPE ropes intended for use as station-keepinglines, a test is to be performed following the procedure inApp 3, at time of prototype testing, to calibrate long-termrope creep rates with data and model of fibre creep.

For parallel construction ropes, this test may be performedon a sub-rope.

This test needs not be performed when data is availablefrom the previous qualification test of another rope (or asub-rope of it) with the same model of rope core, and adiameter not less than 70 mm.

Note 1: This is not applicable to materials such as polyester or ara-mids. See App 1, [3.4] for background information.

5 Endurance and durability

5.1 Cyclic Tension-Tension loading endur-ance

5.1.1 The endurance under cyclic Tension-Tension loadingis to be verified by testing on one sample

This test needs not be performed when data is availablefrom the previous qualification test of another rope, withthe same model of rope in all respect (i.e. including termi-nations and cover), if the size (MBS) of the rope to be quali-fied is between 50% and 200% of that of the tested rope.

5.1.2 The endurance test is to be performed following theprocedure in App 3, for a load range LR between 40% and50% of rope MBS, with a mean load such that the maximumload during cycling is between 52% and 55% of rope MBS.

The rope sample is to withstand cyclic loading for a numberof cycles N to be taken, in function of the load range LR(in% of the specified MBS), such that:

N ⋅ LR5,05 = 166

Note 1: With above limits on load range, N will be between 5 500and 17 000.

At the end of cycling, the rope is to be loaded to break, todetermine the residual strength, that shall be at least 80% ofthe MBS

5.2 Axial compression fatigue

5.2.1 For ropes that are sensitive to compression (e.g. ara-mid or polyarylate fibres), axial compression fatigue is to beverified at time of prototype testing, by testing on one sam-ple according to App 3.

After low tension cycling, the rope is to be loaded to break,to determine its residual strength that shall be at least 95%of the MBS

This test needs not be performed when data is available fromthe previous qualification test of another rope with the samemodel of rope core, and a diameter not less than 90 mm.

Note 1: This is not applicable to materials such as polyester or HMPE.


NI 432, Sec 6


5.3.1 A test is to be performed following the procedure andcriteria in ISO 18692-1, as quoted in App 3, to verify theeffectiveness of the particle ingress protection.Such test need not be performed when data is availablefrom the previous qualification test of another rope with thesame model of rope, as to overall construction, particleingress protection, and rope cover, and a diameter in princi-ple not less than 100 mm.

6 Sub-sea lowering lines and other applications

6.1 General

6.1.1 The testing requirements in [2] to [5] generally applyto ropes intended for sub-sea lowering lines and otherapplications, taking into account that:• load levels in the linear density and in static and

dynamic stiffness tests may be adjusted to suit the needof intended application

• the lower bound MBS, specified in [3]and in [5] for theacceptance of previous tests for another rope size, will

be considered on a case-by-case basis, depending onrope construction.

Note 1: A lower bound in the range of 1000 kN is generally applicable.

6.2 CBOS performance

6.2.1 For sub-sea lowering lines or other applicationswhere a rope is repeatedly passed over a sheave or equiva-lent device, the Cyclic Bending Over Sheave (CBOS) perfor-mance of the rope is to be documented.

Note 1: CBOS tests are typically performed on small or intermedi-ate sizes, as needed to qualify the fibre and the rope, and to evalu-ate the sensitivity to geometrical (or other) parameters.

Full size testing in representative conditions is to be consid-ered for validation before an approval can be granted.

6.3 Other applications

6.3.1 Additional tests are to be considered for particularapplication, and/or a particular product or usage or serviceconditions. Testing methodology and acceptance criteriawill be considered on a case-by-case basis.


NI 432, App 1

APPENDIX 1 ROPES FOR STATION-KEEPING: DESIGN AND OPERATING CRITERIA

1 General

1.1 Subject

1.1.1 This Appendix outlines the design and operating cri-teria specific to fibre rope mooring systems, complementingand updating the requirements of NR493 (see Sec 1,[1.5.1]) - In case of discrepancy, the latest edition shall pre-vail), and provides information on the background of certifi-cation requirement.

2 Arrangement of Mooring System

2.1 Lay-out

2.1.1 The requirements for fibre ropes used as station-keep-ing lines or similar applications, in this Guidance Note andin the present Appendix, are generally intended for arrange-ments where the rope is fully immersed and free-standingbetween termination points.

2.1.2 A deepwater fibre rope mooring system generallyincludes, for each line:

• a bottom steel section, most often chain, attached to theanchor point

• the fibre rope section

• a top steel section.

Note 1: Other arrangement would require specific considerations:see [2.5]

Note 2: The system may be a taut leg system, with only a short bot-tom steel section, or a semi-taut / catenary system, where a longerbottom chain section is provided. The top section is usually madeof chain in permanent mooring, or may be a wire rope (e.g. inmobile offshore drilling units).

The fibre rope section may be made of several segments, ifneeded for practical reasons of fabrication or handling (seealso [4.3]).

2.2 Torsional behaviour

2.2.1 A torque neutral construction is generally used inpermanent systems, where other line sections are made ofchain or torque neutral spiral-strand wire ropes.

Note 1: A parallel construction is most often used, that is inherentlytorque neutral

2.2.2 A torque-matched construction should be used inlines including non-torque-neutral wire ropes, such as six-

strand wire ropes, unless other arrangement is provided toavoid cyclic torsion at the interface.

Note 1: The cyclic variations of line tension would induce, in anon-balanced line, a cyclic torsion leading to degradation byfatigue of the wire rope near terminations.

2.3 Line top section

2.3.1 The line top section shall have a suitable length sothat, with due allowance for the initial elongation of fibrerope under system pretension, further elongation over plat-form life, and creep where applicable (see [4.2] and [5.3]):

• an adequate pre-tension can be maintained.

• the top of fibre rope is kept clear of platform fairleads

• the upper part of fibre rope is kept well below surface,in order to avoid degradation due to UV and at a suffi-cient depth (in principle at least 100m) to avoid thedevelopment of hard marine growth (micro-organismswith a mineral shell) inside the rope.

Note 1: Some extra length is generally provided for line hook-upand initial tensioning.(see also [5.3]).

2.4 Line bottom section

2.4.1 The line bottom section shall have a suitable length tokeep the fibre rope clear of sea bottom in leeward lines, andthus avoid detrimental chaffing or ingress of soil particles.

2.4.2 Ropes being fitted with a particle ingress protection,this condition need not be applied to the “redundancycheck” (damaged) design conditions of the system, pro-vided it can be ensured that sea-bottom do not include hardsoil areas and is free from other obstructions.

2.5 Rope protection

2.5.1 The rope cover and filter (particle ingress protection)provide a protection of the load-bearing rope core duringinstallation and in service.

2.5.2 The rope cover is protecting the rope against chaffing.Suitable procedures should be however considered to avoidcontacts that may generate cutting (such as sharp edges orsteel ropes).

2.5.3 The filter is avoiding the ingress of solid (soil) parti-cles in case of accidental drop-off on, or contact with thesea floor. It is thus considered as an elementary precaution.It is also expected to have some beneficial effect withrespect to hard marine growth (this is however currently notquantified).


NI 432, App 1

2.5.4 Both cover and filter as specified in this document areintended for the arrangement as defined above, and the cri-teria in [3] and [4]. Other arrangement of the system or ser-vice conditions would require specific considerations of therelated hazards, with an enhanced rope protection or othermitigating provisions (see also [3.2]).

3 Design criteria (in-place system)

3.1 Strength (maximum tension)

3.1.1 The design criteria for the strength of line compo-nents, i.e. the Safety Factors for each of the design conditionexamined, are to be in accordance with the relevantrequirements of NR493 (see Sec 1, [1.5.1]).Note 1: The reference strength is the specified MBS, as verified bythe testing procedure in App 3. Adjusting the breaking strength,upward or downward, from test results is not permitted: doing sowould require that a larger number of test results (5 minimum) isavailable, from which a “characteristic breaking strength” could beobtained by suitable statistical derivation. Such procedure might beconsidered by Rope Manufacturer at time of rope design, usingsmall size ropes or sub-ropes, but is not required for Rope Approval.

3.2 Minimum tension in leeward line

3.2.1 The minimum tension in leeward lines is to be evaluated.

3.2.2 For ropes made of materials that are sensitive to com-pression failure (such as aramid and polyarylate), and whenthe ropes have demonstrated axial compression fatigue per-formance, as per Sec 6, [5.2], a minimum dynamic tensionof 2% of the MBS is to be maintained in the rope, for alldesign conditions of the system. This is however not requiredfor the “redundancy check” (damaged) design conditions.

3.2.3 For ropes made of materials that are not sensitive toaxial compression failure (such as polyester and HMPE) andfor permanent systems, a positive tension is to be main-tained, in principle, in the fibre rope under operating anddesign conditions, not including however the “redundancy”check (damaged) design conditions.

This is intended to avoid complete slackening of the line,then contact of the rope with sea bottom (see [2.4] above)and risks of snap loads in the bottom line section, particu-larly when occurring under dynamic conditions.

If this is not achievable given system geometry, considera-tions should be made for adequate protection or other miti-gating provisions.Note 1: As a guideline, a minimum quasi-dynamic tension of 2% ofMBS in the “intact” design conditions may be considered.

3.3 Endurance under cyclic Tension-Tension loading

3.3.1 The fatigue life of the lines under cyclic Tension-Ten-sion loading should be evaluated, in accordance with therelevant requirements in Rules NR493 (see Sec 1, [1.5.1]).Note 1: Attention is drawn to the fact that, in a fibre rope mooring,the adjacent steel components will generally have a fatiguestrength significantly lower than the one of the rope itself.

• For polyester ropes, the T-N curve therein is applicableto carefully designed and manufactured long lay polyes-

ter ropes, meeting all the requirements of this GuidanceNote. Same T-N curve apply –conservatively- to long-lay HMPE ropes, meeting all relevant requirements ofthis Guidance Note.

Note 2: With respect to the data from the Rope Durability project(OTC 17510 − 2005 − Banfield S.J., Casey N.F., Nataraja R. −Durability of Polyester Deepwater Mooring Ropes), this T-Ncurve account - conservatively - for scale effects that have beenobserved at medium load ranges. A cut off could be applied (at aload range of 5% of MBS), but will only make clearer that fatigueis more critical in adjacent (steel) components of the line.

Note 3: For these materials, the endurance test in Sec 6, [5.1.1],Sec 6, [5.1] is intended as a verification test.

• For other materials, having a rope endurance validated bythe “cyclic loading endurance test” in Sec 6, [5.1], the T-N curve for spiral strand wire ropes may be considered.

3.4 Creep

3.4.1 Where relevant, e.g. for HMPE, a prediction is to bemade of the long-term creep of the rope. This prediction isto be based on:

• fibre data of creep rates (See OCEANS − 2006 − Vlasb-lom M.P. and Bosman R.L.M. − Predicting the CreepLifetime of HMPE Mooring Rope Applications.)

• correlation between fibre and rope obtained from proto-type testing (see Sec 6, [4]).

3.4.2 This prediction will provide an evaluation of theexpected creep per year, thus of the expected life time ofrope (for this criterion) with respect to intended service life,taking into account the allowable creep elongation for asection of the rope, that is defined as the smaller of:

• the extension at which the strength of the rope is still atleast 95% of the original specified MBS; or

• 10% of the installed length.

Note 1: The term “creep” is referring here to the progressive, aboutproportional to elapsed time, non-recoverable increase of length ofthe fibre or rope under a constant load, that is exhibited by somematerials, such as HMPE.

Note 2: An evaluation method is outlined in A.14.4 of ISO standardon station-keeping systems (ISO 19901-7 − 2005 − Petroleum andnatural gas industries − Specific requirements for offshore structures− Part 7: Station-keeping systems for floating offshore structures andmobile offshore units).

Note 3: Creep is both load and temperature dependent. Then, onlythe most critical section (usually the top part) needs to be evaluatedwith respect to the allowable creep. An evaluation for the wholelength could also be made to indicate the expected total creepelongation, where needed.

4 Installation, Operation and Inspection

4.1 Installation

4.1.1 The installation of the mooring system is to be per-formed following detailed and carefully engineered proce-dures, in order to avoid torsion and damage by over-bending on obstacles, chaffing or cutting, as well as con-tamination by solid or liquid projections.


NI 432, App 1

Guidance on rope handling care, identification of damagesand repair may be found in Annex D of ISO 18692-1.

Lines are to be generally deployed under a low tension,with a suitable minimum tension being ensured to avoidrisk of damage by local over-bending in a free-span, and areto be generally kept clear of sea-bottom.

Seizing of line, or seizing of ancillary installation devices online, is to be performed by soft rope seizing only. The accu-mulation of twist in line is to be avoided.

4.1.2 Ropes being fitted with a particle ingress protectionmay be pre-laid on bottom, provided it is ensured that sea-bottom do not include hard soil areas and is free from otherobstructions.

Note 1: A rope without particle ingress protection that has beendropped or laid on the sea-floor is not to be used as a long-termcomponent of a permanent mooring system.

4.1.3 For materials that are sensitive to compression failure,pre-deployed lines, if not laid on bottom, are to be main-tained under tension, in a way that is preventing high cyclicstraining (by bending or torsion) at rope ends. A minimummean tension of 2% of MBS may be considered, providedthat the rope has not been pre-stretched before.

4.1.4 As possible, a pre-stretching of rope (see [5.3])through appropriate hold load or cycling is to be performedwithin the hook-up sequence. However, the tension in ropeduring pre-stretching (and for anchor testing, if applicable)should not exceed 50% of fibre rope MBS.

4.2 Re-tensioning

4.2.1 During operation, and primarily in the first monthsafter installation, lines tend to slacken due to bedding-in ofthe fibre ropes (see [5.3]). Adequate means are to be availa-ble to control line tensions (see NR 493, Sec 4), and to re-tension the lines, whenever needed, to design pretensions(see also [5.3]).

4.3 Inspection of rope

4.3.1 For permanent offshore units, the monitoring of ropecondition is normally achieved through “visual” inspection(by ROV). However, recovery, then inspection and testing ofa rope section, may be necessary in some circumstances(e.g. after a significant accidental event).

For this purpose, it is recommended that short rope seg-ments (inserts) are provided (one at the top of each line).

Note 1: Alternatively, the Operator should be prepared to plan theremoval of a full line, or at least the top length, whenever needed,and a section be cut for inspection.

Note 2: The length of inserts is usually taken same as for test ropes,so that a break test can be performed (see Note 3). Removed insertsgenerally need not be replaced, their length being compensated byan adjustment of top-chain segment.

Note 3: On a recovered insert, after inspection, a break test is usu-ally performed to assess its residual strength. This however providesonly an overall indication when the rope has seen substantial degra-dation. For parallel construction ropes, the break test should be pref-

erably performed on some of the sub-ropes, and other sub-ropesshould be dissected, to perform a more accurate assessment fordeteriorations, by visual and scanning electron microscope (SEM)examinations, and through yarn re-testing (see Sec 5, [1.2.5]).

4.3.2 For mobile offshore units, the lines are to be subjectto comprehensive inspection when recovered between plat-form moves, with attention to damage by cutting, chaffing,or contact with sea-bottom. Whenever needed a section isto be cut for inspection and testing, at one or the other end,unless inserts have been provided to that effect.

4.4 Creep monitoring

4.4.1 Where relevant, e.g. for HMPE, creep in a top sectionof the rope should be monitored, through adequate marking.

The maximum allowable creep elongation defined in [3.4]should not be exceeded.

Other criteria (e.g. a maximum service time) recommendedby fibre or rope manufacturer(s) are also to be met.

5 Load-elongation of fibre ropes

5.1 General

5.1.1 A proper knowledge of the load-elongation proper-ties of fibre ropes is needed for designing a system. How-ever, these properties are rather complex to evaluate andspecify, in comparison with the linear elastic behaviour ofequivalent steel components. The model below definesrope properties for engineering and analysis of a fibre ropemooring system, in a consistent manner with the testingprocedures specified in this Guidance Note.

Note 1: Due to the nature of constituent material (a complexassembly of long chains of organic molecules), fibres and fibreropes exhibit a visco-elasto-plastic behaviour (i.e. non-linear andtime dependent) that cannot be reduced to a load-elongation“characteristic”, be-it non linear.

5.1.2 A particularly important aspect, quite specific to fibreropes, is the modification of the properties of a rope duringthe first loading(s) and during the early stages of rope ser-vice. This process, called “bedding-in”, involves changes atboth a macroscopic level (e.g. compaction of the structure)and, primarily, at a molecular level within fibres. Bedding-in results in an essentially permanent - not recoverable -elongation with respect to the rope initial length at time ofmanufacturing (unless the rope is returned to a loose condi-tion for a substantial time - what does not happen in anoperating mooring system), and in some changes in the rhe-ological properties.

Most of the bedding-in happens during the initial loading,at time of installation, or quickly after. Rope pre-stretchingduring installation improves bedding-in. Further - delayed -bedding-in occurs with the variations of mean loads and thecyclic loading imposed by metocean or other (e.g. re-ten-sioning) actions.


NI 432, App 1

5.1.3 The (mean) elongation of a rope may thus be definedas the combination of two terms:

• A load dependent incremental permanent (non-recover-able) elongation, happening principally when the ten-sion in rope exceeds the maximum tension achieved ina previous storm or other event (see [5.3]).

• A time dependent visco-elastic term tending, under sta-tionary conditions, toward a stabilisation of the ropeelongation (depending on end conditions and previoushistory this term can be creep, recovery, relaxation orinverse relaxation).

5.2 Model

5.2.1 Based on earlier work (see [6.1]), a practical Engi-neering model has been developed (see [6.2]) and [6.3]),for modelling in analyses the load-elongation characteris-tics of polyester ropes.

Tests performed on other materials have generally con-firmed the applicability of this model for a number of mate-rials, but less calibration data are available.Note 1: See OTC 20846 - 2010 - François M., Davies P., GrosjeanF. and Legerstee F. - Modelling Fiber Rope load-elongation proper-ties: Polyester and other fibers).

5.2.2 The elongation of a rope working as a line in a sta-tion-keeping system can be written as the sum of threeterms, related to the time scale of actions:

• elongation under permanent load (line pretension)

• variations of elongation induced by variations (increaseor decrease) of the mean tension in each line, under theeffect of changing weather conditions, i.e. a time scaleof several hours, or days, that is the field of applicationof the “quasi-static” stiffness

• rapidly varying (cyclic) loading (or imposed cyclic dis-placements), i.e. a time scale ranging from seconds (e.g.wave induced motions) to minutes (e.g. slow driftmotions or VIM, around the natural period of the sys-tem): this is modelled by a “dynamic” stiffness.

This separation is also matching the typical steps of a moor-ing analysis, whatever frequency or time domain is used:

• set-up of the model

• static response to mean loads

• low and wave frequency response.

5.3 Elongation under permanent load

5.3.1 The elongation of the rope under permanent load(system pretension) is accounted for by considering thelength under pre-tension of the rope (see below).

In analysis, it is normally assumed that, at a given time, thepre-tensions have been reset to their design values.Note 1: When relevant, analysis with lower-bound pretensions tak-ing into account accumulated permanent elongation, should beconsidered.

The length of finished ropes LT0 is defined, in Sec 4 as a bedded-inlength at a specified tension. This may be deemed a lower-boundevaluation of the as-installed length under pre-tension. The lengthunder pre-tension however increases with time, and re-tensioning

may be needed from time to time, e.g. after an important storm. ForHMPE, creep further increases rope length with time.

Note 2: A loading sequence that is deemed representative of a typi-cal installation condition of a station-keeping system is specified inthe testing procedure (the “linear density test”, see App 3, [3.3]), sothat the bedded-in length is representative of the as-installed lengthof the ropes at a reference pre-tension T0 of 20% of MBS. Othertension or bedding-in conditions may be specified if deemed moreappropriate (see Sec 4, [4.1.1]), e.g. in relation with pre-stretchingof lines and in-situ load test, if any (see [4.1]).

Note 3: An evaluation of the length in the design conditions couldbe derived from the mean elongation during the test for quasi-staticstiffness (see also Note 4). Some margin for later elongation shouldbe considered.

Note 4: For the purpose of analysis, the length under tension canbe backed-up to a theoretical “length-at-zero-tension”, using thestiffness specified in the particular step of analysis. As the rope,once installed, is kept under a sustained tension, a true length atzero tension is not very relevant, and its evaluation by tests wouldraise experimental difficulties.

Note 5: For the purpose of installation planning, the “length at refer-ence tension” L0 (see Sec 4, [3.1.1]) can be deemed representative ofthe length on storage reel (new rope, spooled at a very low tension).

5.4 Stiffness

5.4.1 Under the assumption of a linear elastic behaviouraround a given mean condition, the load-elongation rela-tion of a line subject to a varying load is written as:

ΔF = Ku ⋅ ε

with:

ε = ΔL / L

ΔF (and ΔL): The variation of tension in a rope segment oflength L, under a variation of length ΔL,

Ku : The spring Δconstant (sometimes noted EA) of aunit length of line.

Note 1: For consistency of results, L can be taken as the bedded-inlength of rope segment under tension T0 (see [5.3]).

Normalisation of Ku, either by the rope MBS, or by the rope(core) linear density m, leads to the following expressions:

• ΔF / MBS = Kr ⋅ ε• ΔF / m = (E / ρ) ⋅ ε

where

Kr : A reduced stiffness, which is dimensionless

E / ρ : A modulus, in tenacity unit (N / tex).Note 2: In fibre ropes, normalisation by m have been found appro-priate for comparisons over a rather large range of sizes (from yarnto ropes), but normalisation by MBS, more practical for users, isused in this Guidance Note.

5.4.2 Once the stiffness of ropes with a given fibre hasbeen adequately characterised, only a limited amount offull size testing is needed, on one rope size, to verify andcalibrate, if necessary, the properties of a particular ropemodel. Then, the measurement of “Krebi”, the dynamicstiffness at end of bedding-in, within the breaking test per-formed for each rope size, will confirm these data for anyother size.Note 1: The quasi-static and the dynamic stiffness of fibre ropes aredepending on rope construction, but, primarily, on fibre material. A


NI 432, App 1

proper characterisation should thus start by testing at the fibre level,then on representative sub-ropes or ropes.

Note 2: As noted in [5.1], the rope properties are depending onload history. In this respect, a Phase 1 (initial loading and bedding-in) is included in the test sequences defined in App 3, so that themeasured stiffness may be deemed representative of the conditionsat the time when the design conditions happen.

5.5 “Quasi-static” stiffness

5.5.1 The variations of line elongation under a tension var-ying at a very slow rate can be generally modelled by a lin-ear “quasi-static” stiffness Krs.

Note 1: The “quasi-static” stiffness is addressing the effect of meantension variations, under changing weather conditions such as thebuild-up and decay of a storm or the occurrence of a loop current.Among other effects, these changing conditions are causing anincrease or a decrease of the mean tension in the lines (in “wind-ward” or “leeward” lines, respectively) from the initial pre-tension,at a very slow rate. This does not include the “slow-drift” motions,for which the dynamic stiffness is applicable (see [5.6]).

Note 2: The wording “quasi-static” stiffness is used to differentiatefrom other approaches or measurement sequence, particularly thestiffness over a monotonic ascending loading at standard cross-head rate, often but unduly termed “static stiffness”.

The “quasi-static” stiffness is obtained by the “quasi-static”stiffness test described in App 3. In this test, after a properbedding-in, the rope is cycled between two tension levels,over several cycles, each having a duration of 1 h (twice 30minutes).

Note 3: Cycling is performed to get rid of the initial condition ofrope on the test bench, not representative of actual condition.Result can be averaged over several cycles, to verify stabilisationand eliminate eventual measurement errors, in all cases ignoringthe first half cycle.

5.5.2 From test results (load and elongation versus time),cycles of longer duration can be simulated as follows, to geta stiffness that is more representative of the loading durationin the events intended to be modelled.

a) The elongation Lτ at the end of each 1/2 cycle of dura-tion τ, is derived from a fitting of the creep (or recovery)plateau as:

L(t) = Lp + ac ⋅ log [1 + (t - tp) / ta]

where:

tp : Time at a point along the load plateau (anypoint)

ac : Creep «per decade» over the plateau

ta : Time scale constant

Lp : Elongation of the rope sample at time tp,

ac, ta, and Lp being obtained by a three parameter fit of theelongation versus time over the loading plateau (see [6.2]).

b) From L(t), the elongation Lτ can be obtained as:

Lτ ~ Lp + ac ⋅ log [τ / ta]

c) The (linearised) “quasi-static” stiffness is then taken as asecant stiffness, i.e.:

Krsτ = (T2 − T1) / (L2τ − L1τ)

where:

T1, T2 : The tensions during the plateau of two succes-sive 1/2 cycles (in % of MBS),

L1τ , L2τ : The calculated elongation at the end of these1/2 cycle (in %).

The tensions T1 and T2 are normally taken as 10% and 30%of MBS, and the duration τ is normally taken as 12 h.

Note 1: Longer duration τ could be more appropriate for some meta-ocean events (e.g. 7 days for the rising time of a loop current event).

Note 2: For variations of mean tension beyond those in the “quasi-static” stiffness, test, a (non-linear) “quasi-static characteristic” canbe obtained from the results of the test (see [6.3]), that will provide amore accurate estimate of e.g. minimum tensions in leeward lines.

5.6 Dynamic stiffness

5.6.1 A linear stiffness Krd, dependent on the mean tension inthe line (see [6.1] and [6.2]), can be used to model theresponse to dynamic loadings (both the “wave frequency” andthe “low frequency” loadings (see NR 493, Sec 1, [1.5.1])

During cycling on a test bench at a constant mean tension,the stiffness rapidly increases at the beginning of the run,then tends to stabilise. The measurements of the dynamicstiffness with a limited number of cycles (100 to 300) after astandard bedding-in condition, as specified in App 3 willprovide adequate reference data.

Note 1: Other parameters influencing the dynamic stiffness (loadrange, frequency) are deemed negligible (at least less significant),and would be also difficult to account for in the analysis process.

Note 2: For characterisation, the dynamic stiffness is typicallyobtained from tests under cyclic loading around a number of meantension, including primarily tests under a constant amplitude (har-monic) loading and some tests under representative stochasticloadings.

For rope qualification, measurement at three levels of mean tensionand one tension range are deemed sufficient.

Note 3: Long duration tests indicate that the stiffness would con-tinue to increase, even over a very large number of cycles, but suchobservation were made in conditions (constant amplitude, no priorbedding-in) that may not be representative of the actual conditionsin the field, where mean tension variation and cycling happensimultaneously.

5.7 Data for polyester ropes

5.7.1 The following data may be considered for polyesterropes.

These data are applicable to “normally stiff ropes”, i.e.ropes with a “Krebi” between 18 and 23, i.e. in the lowerhalf of the range specified in Sec 6, [2.4].

Quasi-static stiffness:

• Krs = 15

Dynamic stiffness:

• Krd = 18,5 + 0,33 ML (upper bound)

• Krdm = 15 + 0,25 ML (lower bound)

where:


NI 432, App 1

ML : Mean tension, in% of MBSNote 1: See [6.2.1] and [6.3.1] for data references

Note 2: For the evaluation of behaviour at time of pre-tensionadjustment, at the end of installation, a stiffness at tensioning maybe taken as: KrT = 10.

Note 3: The increase of length between the supplied length underpretension LT0 and stabilised conditions may be evaluated as beingin the order of 2 to 3%.

6 Reference documents

6.1 Proceedings of the Offshore Technology Conference (OTC)

6.1.1 • OTC 6965 − 1992 − Chaplin C.R. and Del Vecchio

C.J.M. − Appraisal of Lightweight Moorings for DeepWaters.

• OTC 10779 − 1999 − Bosman R.L.M. and Hooker J. −The Elastic Modulus Characteristics of Polyester Ropes.

6.2 Proceedings of the Rio Oil & Gas confer-ence (IBP)

6.2.1 • IBP 247 00 − 2000 − François M. and Davies P. − Fibre

Rope Deepwater Mooring: a Practical Model for theAnalysis of Polyester Mooring Systems.

6.3 Proceedings of the International Confer-ence on Ocean, Offshore and Artic Engi-neering (OMAE)

6.3.1 • OMAE 57136 − 2008 − François M. and Davies P. −

Characterisation of Polyester Mooring Lines.


NI 432, App 2

APPENDIX 2 TEMPLATES FOR DATA SHEET

Table 1 : Summary of rope design

General information

Manufacturer

Product name / Rope model

Type of service

Outside diameter (in mm):

Minimum Breaking Strength MBS (in kN):

Fibre Material

Supplier

Designation

Rope core Construction

Torque behaviour

Cover Material

Construction

Particle ingress protection

Termination Type

Termination fittings

Typical Assembly DWG

Other information


NI 432, App 2

Table 2 : Rope design - Construction details

General information Manufacturer


Size

Type of service

Fibre Rope core fibre Material

Fibre supplier & Designation

Size (dTex)

Cover fibre Material

Fibre supplier & Designation

Size (dTex)

Rope construction

Item (1) Number of components Construction (2)Size

(dtex or mm or kg/m)Pitch (mm) ortorsion (t/m)

Core Yarn

Intermediate yarn

Strand

Sub rope

Rope core

Linear density (kg/m)

Cover Yarn

Intermediate yarn

Strand

Particle ingress protection weight (kg/m)

Linear density (in kg/m)

Thickness (mm)

Rope Linear density (in kg/m)

Diameter (mm)

Terminations Type

Cover material

Coating

Assembly DRWG

Dimensions Inside radius (mm)

Eye length (mm)

Length of splice (mm)

Thimble Material

Supplier

Test load

DWG

Other informations

(1) List to be adjusted to proposed construction(2) Parallel, laid or braided


NI 432, App 2

Table 3 : Rope supply data sheet

PROJECT

Manufacturer


Type of service

Dimensions Outside diameter (in mm):

Minimum Breaking Strength MBS (in kN):

Reference rope approval

Manufacturer’s signature

Rope particulars Rope core material

Torque behaviour

Particle ingress protection

Termination type

Termination fittings

Typical assembly drawing

Remarks

Item designation Number in supply Length at.............load Assembly drawing


NI 432, App 3

APPENDIX 3 ROPE TESTING

1 General

1.1 Subject

1.1.1 This Appendix defines the procedures for the testingof fibre ropes following the provisions of Sec 6.Note 1: The procedures herein are in line with those of ISO 18692and related documents (see Sec 1, [1.5.2]).

Other testing procedures could be considered if, in theopinion of the Society, they can be deemed equivalent tothose herein, or more appropriate for a particular product orusage or service conditions.

Any additional tests, when required, are to be performedfollowing previously agreed procedure.

2 Testing conditions

2.1 Testing equipment

2.1.1 The testing machine is to have adequate capacity andstroke for the intended tests, and is to be fitted with a con-trol system such that applied load (or crosshead movement)is continuously monitored, at any time during the testingsequence (i.e. during both loading and unloading).

For cyclic loadings, the period of cycling is to be takenbetween 10 s and 30 s, unless otherwise specified.Note 1: In the testing steps described in the following sections,loads are defined as a percentage of the (specified) rope MBS.

For testing on sub-ropes of a parallel construction rope, the same per-centage of a reference strength RBS, in kN, is to be taken, given by:

RBS = MBS / n

where

n : Number of sub-ropes in rope core.

Note 2: During ramp loadings (both increase -including for break-ing or decrease) the rate of loading, specified in% of MBS per min-ute, may be obtained either as a tension rate or as the equivalentcross head velocity.

Note 3: The triggering signal is to be - or as close as possible to - aharmonic (sinusoidal) signal. The amplitude and/or period of thefirst 10 cycles in a sequence may slightly deviate from specified,but the period is not to exceed 60 s in principle.

Note 4: For stiffness measurements, cyclic loading, defined in thefollowing sections as load ranges, may be also applied as the equiv-alent imposed displacement, provided mean load can be kept con-stant over the duration of cycling.

2.2 Condition of rope samples

2.2.1 SamplesRope samples are to be fully representative samples of therope model, in all respect, and of the size to be qualified,unless otherwise accepted in Sec 6.

Samples for load-elongation measurement and linear den-sity tests may have different terminations. In such case, dueattention is to be given that rope samples are selected andmounted in accordance with the test to be performed.

Note 1: Rope samples for break tests, cyclic loading endurance,creep and axial compression tests are to be mounted on the speci-fied thimbles, or on fittings with same radius and groove shape, andsame type of material as the specified fittings.

Note 2: For parallel construction ropes some of the tests can beperformed on sub-ropes when – and only when - specified in thefollowing.

2.2.2 Sample condition

The tests are to be generally performed with samples in awet condition, obtained by soaking the sample in freshwater, for a minimum of 4 hours.

The linear density test, however, is to be performed on a drysample.

For the cyclic loading endurance test the sample is to bekept wet by water spraying, or by performing the test withthe sample immersed, using fresh water.

Same conditions shall apply for the axial compressionfatigue test of Aramid and Polyarylate ropes.

The creep test of HMPE ropes is to be performed in temper-ature controlled conditions.

Note 1: Provided the material is not sensitive to the effect of water,tests for load-elongation or torque measurements can be performedon dry samples.

2.2.3 Cover condition

For the breaking test of prototype rope and other gaugelength elongation measurements, the cover is to be cut forthe marking of rope core (measurement by video imageprocessing) or for fixing the extensometer.

For the linear density test, at the contrary, the marking is to bemade on the cover, and the cover is to be fastened to the ropecore, so as to avoid any slippage between core and cover.

Note 1: The rope cover is not meant to contribute to the ropestrength. However, the cutting of cover may be omitted for thebreaking strength test of a production sample.

Note 2: For the cyclic loading endurance test, no extensometer is tobe fixed to the sample, to avoid any damage to the rope that couldbias the test result.

2.3 Recording

2.3.1 The ambient conditions (such as humidity, water orair temperature) during each test are to be recorded.

The crosshead elongation and rope tension are to be continu-ously recorded over each test. The recording of rope tensionis to be performed by a properly calibrated strain gage system.


NI 432, App 3

For stiffness measurements, the elongation over a gaugelength of 1 m minimum set at middle of the test rope, clearfrom terminations, is to be recorded by a system of ade-quate sensitivity, taking into account rope material andintended sequences.

As possible, the gauge elongation and load are to be contin-uously recorded.

Note 1: The cross-head elongation provides an overview of therope behaviour along each test, but can only give qualitative indi-cations on stiffness. Gauge elongation measurements, by eliminat-ing the effect of splice and eye, provide quantitative data that arerepresentative of the response of a long line.

2.3.2 As a minimum, the gauge length and elongation areto be continuously recorded as follows, during the breakingtest and stiffness measurement test defined in [3.2] and [4]:

• over, initial loading and unloading of rope sample

• over the last bedding-in cycles (at least three full cycles)for the measurement of the dynamic stiffness at end ofbedding-in

• over the full three cycles of the “quasi-static” stiffnesstest (load and elongation versus time)

• over the last cycles (at least three full cycles) of eachmean load step of the dynamic stiffness test, for themeasurement of the dynamic stiffness.

For the calculation of elongation of the rope in% (i.e.strain), the variation of gauge length is normalised by thegauge length at the time of the lower load, in the last cycleof each step.

A suitable reference gauge length, taken as a constant overthe whole test may be more convenient and can also be used.

Other pertinent test conditions and results are to be dulyrecorded

Note 1: The sampling rate may be adjusted according eachsequence e.g., as a minimum, one per 30 s during load ramps, oneper minute during a load holding plateau, one per second duringcycling for dynamic stiffness.

Note 2: In theory, the variation of gauge length should be normal-ised by either the gauge length at the start of a sequence or an aver-age gauge length, depending on the test.

3 Testing sequences

3.1 General

3.1.1 Each test generally includes the following threephases, unless otherwise specified for a particular test:

• Phase 1: initial loading and bedding-in

• Phase 2: cycling

• Phase 3: loading to break

For each test, the steps of the different phases are detailed inthe sub-sections below.

Note 1: During phase 1, if the sequence needs to be interrupted,e.g. to reset fixed end or gauge length measurement system, duringinitial loading or bedding-in, the corresponding step shall berepeated (i.e. for the full number of bedding-in cycles).

3.2 Breaking test

3.2.1 A breaking test includes the following steps:

a) Phase 1:

• mount the sample and load to 2% of rope MBS, formarking and for setting of extensometer

• increase tension to 50% of MBS, in approximately 5min and hold load for 30 min

• unload to 10% of MBS, at about same rate (approxi-mately 10% / minute)

• bedding-in: perform cyclic loading (see [2.1]),between 10% and 30% of MBS, for 100 cycles.

Krebi, the dynamic stiffness at end of bedding-in, is tobe obtained in the same way as the dynamic stiffness inother conditions (see [4]).

b) Phase 2:

as detailed in [4]) below, when the stiffness measure-ments are performed as part of breaking strength test(see [4.3] and [4.4]), otherwise this phase is skipped.

c) Phase 3:

• unload the sample to 2% of MBS

• load to break, at a rate of about 20% of MBS / min

• record the residual breaking strength of the rope.

3.3 Linear density test

3.3.1 A linear density test includes the following steps,without interruption:

a) Phase 1:

• mount the sample, load to 2% of rope MBS, andmark a length LR0 of about 2m

• increase tension to 20% of MBS in approximately 5min

• perform cyclic loading between 15% and 25% ofMBS, for 100 cycles.

b) Phase 2:

• at end of cycling, hold load at 20% of MBS andmeasure the length LR20 (m) between marks

• unload to 2% of MBS, and measure the length LR2

between marks.

c) No phase 3, but:

• Cut the sample at the marks, and weigh it:

The linear density LD20, in MTex, is then obtained as

LD20 = MR / LR20

where

MR : Mass of the cut sample, in kg

• Separate cover and weigh the rope core:

The linear density LDC0, in MTex, of rope core atreference load is then obtained as

LDC0 = MC / LR0

where

MC : Mass of rope core of the cut sample, in kg


NI 432, App 3

Note 1: Linear densities LD0 and LD2 are obtained in the same wayas LD20, from LR0 and LR2. These data are for information.

Note 2: When another hold load T0 (instead of 20% of MBS) or otherinitial loading and bedding-in sequence is specified, the lineardensities LDT0 is obtained in the same way as LD20, from LRT0.

Note 3: In the conditions specified in Sec 6, [3.1], this test may beperformed on a sub-rope (or on the rope sample itself), usingan extensometer, and omitting the phase 3 (cutting of rope).

The linear density LDT0 (or LD20) is then obtained as:

LDT0 = LD0 ⋅ LT0 / L0

where

LD0 : Linear density at reference load, obtained fromthe QA/QC rope sample (see Sec 5, [1.2]),and theratio LT0 / L0 is obtained from extensometer dataduring the test.

If reference is made to a previous qualification test performedon a rope of the same model, the ratio LT0 / L0 is to be takenfrom that test.

Note 4: If a lower reference load than 2% of MBS is used inQA/QC samples (see note in Sec 5, [1.2.1]), the length L0Q atthat tension is to be measured first.

3.4 Creep test

3.4.1 The following test may be performed, on one sub-rope sample, to calibrate creep rate of an HMPE rope withfibre data:

a) Phase 1:

• mount the sample and load to 2% of RBS (see[1.2.1]), for marking and for setting of extensometer

• increase tension to 50% of RBS, in approximately 5min and hold load for 30 min

• unload to 20% of RBS, at about same rate (approxi-mately 10% of RBS / minute)

• cycle between 10% and 30% of RBS and for a mini-mum of 300 cycles.

b) Phase 2:

• select a tension T (typically in the range of 33 to50% of RBS)

• load the sample to the preselected tension T andhold load for a minimum of 7 days

• unload the sample.

c) No phase 3:

The creep rate is obtained by fitting of the elongationversus time (in natural scale) over the end of the test(e.g. last one or two days).

Note 1: The testing temperature is not to exceed 25°C and shouldbe kept as constant as possible over the test duration (no morethan 5°C range)

4 Stiffness tests and measurement

4.1 Testing conditions

4.1.1 The measurements of the quasi-static and dynamicstiffness on prototype rope(s) can be achieved in differentways, as follows:

• quasi-static and dynamic stiffness measurements areperformed on a separate sample than those for breakingtest (case 1)

• quasi-static and dynamic stiffness measurements are per-formed during the phase 2 of one breaking test (case 2)

• quasi-static and dynamic stiffness measurements are dis-tributed over the three breaking tests and performedduring phase 2 of each breaking test (case 3).

The testing sequences for each of those 3 cases are detailedin [4.2] to [4.4] below.

4.2 Testing sequence – Case 1

4.2.1 The measurements are to include, as a minimum, thefollowing steps when performed on a separate sample thanthose for breaking tests:

• phase 1: same as for phase 1 for breaking test: see [3.2]

• phase 2-QS: quasi-static stiffness test

For the measurement of the quasi-static stiffness, phase2-QS includes three cycles, without interruption,between two levels (10% and 30% of rope MBS), withthe following steps for each cycle:

- load slowly the rope from 10% to 30%, at a ratebetween 3% and 10% of MBS / min

- hold load at 30% until 30 min after the start of a)

- unload slowly the rope from 30% to 10%, at a rateas in a)

- hold load at 10% until 30 min after the start of c).

• phase 2-D: dynamic stiffness test, for a minimum ofthree mean loads.

For the measurements of dynamic stiffness, phase 2-Dincludes, as a minimum, cycling (see [2.1]) with a loadrange of 10% (i.e. ± 5%) around each of the following meanloads, in ascending order, for a minimum of 100 cycles:

- 25% of MBS

- 35% of MBS

- 45% of MBS.

• no phase 3.

For parallel construction ropes, the stiffness testing andmeasurements can be performed on a sub-rope. In thiscase, the reference breaking strength (RBS) as defined in[2.1] is to be considered in the above definition of testingsequences instead of the MBS.


NI 432, App 3

4.3 Testing sequence - Case 2

4.3.1 The measurements are to include, as a minimum, thefollowing steps when performed as the phase 2 of onebreaking test:

• phase 2-QS: quasi-static stiffness test, as per [4.2]

• phase 2-D: dynamic stiffness test, for a minimum ofthree mean loads, as per [4.2].

4.4 Testing sequence - Case 3

4.4.1 The measurements are to include, as a minimum, thefollowing steps when distributed over the three breakingtests and performed as the phase 2 of those breaking tests:

a) Sample n°1:

• phase 2-QS: quasi-static stiffness test, as per [4.2]

• phase 2-D: dynamic stiffness test following [4.2], forthe 25% mean load and for a minimum of 100 cycles.

b) Sample n°2:


c) Sample n°3:


4.5 Recording

4.5.1 Quasi-static stiffness testContinuous records of load and elongation versus time areto be taken. The quasi-static stiffness is to be obtained, fol-lowing the procedure in App 1, [5.5].

4.5.2 Dynamic stiffness testContinuous records of load versus elongation are to betaken, at least over the last cycles (minimum three fullcycles) of each step. The dynamic stiffness for the condi-tions of that step (mean-load, load range, period) can beobtained by linear regression.

Note 1: Subject to suitable sampling intervals and accuracy ofelongation measurements, the dynamic stiffness may be alsoobtained from maximum and minimum loads and elongations overthe last cycle.

5 Endurance tests

5.1 Tension-Tension cyclic loading endur-ance test

5.1.1 A cyclic loading test endurance for Tension-Tensionendurance includes the following:

a) Phase 1:



• unload to 30% of MBS, at about same rate (approxi-mately 10% / minute).

b) Phase 2:

Cycle for the specified mean load and load range, as perSec 6, [4], until sample breaks, or the specified numberof cycle is achieved, whichever happens first.

c) Phase 3:




5.2 Axial compression fatigue

5.2.1 An axial compression fatigue test includes the follow-ing steps:

a) Phase 1:



• unload to 20% of MBS, at about same rate (approxi-mately 10% / minute).

b) Phase 2:

• cycle between 10% and 30% of MBS for a minimumof 300 cycles

• cycle between 1% and 20% of MBS for a minimumof 2000 cycles.

c) Phase 3:




6 Other tests

6.1 Response in torsion

6.1.1 The assessment of the response in torsion of a rope,when needed, is to be performed following the method andthe criteria in ISO 18692-1 (see Sec 1, [1.5.2]).

Note 1: Specific testing procedures apply to “torque-neutral” andto “torque-balanced” ropes.


6.2.1 The assessment of the efficiency of the particleingress protection system is to be performed following themethod in ISO 18692-1 (see Sec 1, [1.5.2]). The specifiedcriteria (see Sec 4, [1.6]) are to be met.


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