CERTIFICATION OF FIBRE ROPES FOR OFFSHORE MOORING

Transcription

1 OFFSHORE STANDARD DNV-OS-E303 CERTIFICATION OF FIBRE ROPES FOR OFFSHORE MOORING APRIL 2008

2 FOREWORD (DNV) is an autonomous and independent foundation with the objectives of safeguarding life, property and the environment, at sea and onshore. DNV undertakes classification, certification, and other verification and consultancy services relating to quality of ships, offshore units and installations, and onshore industries worldwide, and carries out research in relation to these functions. DNV Offshore Codes consist of a three level hierarchy of documents: Offshore Service Specifications. Provide principles and procedures of DNV classification, certification, verification and consultancy services. Offshore Standards. Provide technical provisions and acceptance criteria for general use by the offshore industry as well as the technical basis for DNV offshore services. Recommended Practices. Provide proven technology and sound engineering practice as well as guidance for the higher level Offshore Service Specifications and Offshore Standards. DNV Offshore Codes are offered within the following areas: A) Qualification, Quality and Safety Methodology B) Materials Technology C) Structures D) Systems E) Special Facilities F) Pipelines and Risers G) Asset Operation H) Marine Operations J) Wind Turbines O) Subsea Systems Amendments and Corrections This document is valid until superseded by a new revision. Minor amendments and corrections will be published in a separate document normally updated twice per year (April and October). For a complete listing of the changes, see the Amendments and Corrections document located at: under category Offshore Codes. The electronic web-versions of the DNV Offshore Codes will be regularly updated to include these amendments and corrections. Comments may be sent by to rules@dnv.com For subscription orders or information about subscription terms, please use distribution@dnv.com Comprehensive information about DNV services, research and publications can be found at or can be obtained from DNV, Veritasveien 1, NO-1322 Høvik, Norway; Tel , Fax Det Norske Veritas. All rights reserved. No part of this publication may be reproduced or transmitted in any form or by any means, including photocopying and recording, without the prior written consent of Det Norske Veritas. Computer Typesetting (FM+SGML) by Det Norske Veritas. Printed in Norway. If any person suffers loss or damage which is proved to have been caused by any negligent act or omission of Det Norske Veritas, then Det Norske Veritas shall pay compensation to such person for his proved direct loss or damage. However, the compensation shall not exceed an amount equal to ten times the fee charged for the service in question, provided that the maximum compensation shall never exceed USD 2 million. In this provision "Det Norske Veritas" shall mean the Foundation Det Norske Veritas as well as all its subsidiaries, directors, officers, employees, agents and any other acting on behalf of Det Norske Veritas.

3 Changes Page 3 Main changes This standard is an update of the DNV service documents for: 'Certification of fibre ropes for offshore mooring' in order to accommodate experience that has been gained since The following document is replaced by this standard: "Standard for Certification 2.13 (Jan.1999) - Certification of Offshore Mooring Fibre Ropes". There are no changes to main certification requirements compared to the previous standard. On specific conditions the following may now be permitted: Sea-bed contact for fibre-rope assemblies that are not dynamically loaded. Service without inserts in permanent mooring systems. The testing of product rope is now split between subropes and full ropes. Subropes should be used for change-inlength measurements due to the higher accuracy. In addition, a splice integrity test for subrope has been introduced. This aspect was previously only taken into account by the fatigue test on fibre-rope assembly. The following documents will no longer be issued as part of fibre-rope assembly certification: Certificate of Compliance DVR for mooring analysis Inspection Release Note. The DVR for the mooring analysis will be issued separately to the user for verification based on DNV-OS-E301, Position Mooring. Description of fibre-rope change-in-length performance has been harmonised with the ongoing work for the revision of API-RP2SM "Recommended Practice for Design, Manufacture, Installation, and Maintenance of Synthetic Fibre Ropes for Offshore Mooring".

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5 Contents Page 5 CONTENTS CH. 1 INTRODUCTION... 7 Sec. 1 General... 9 A. General...9 A 100 Introduction...9 A 200 Important notice...9 A 300 Scope...9 A 400 Objective...9 A 500 Application...9 B. References...10 B 100 General...10 B 200 Normative References...10 B 300 Informative references...10 C. Definitions...11 C 100 Verbal forms...11 C 200 Terms...11 C 300 Symbols...11 CH. 2 TECHNICAL PROVISIONS Sec. 1 General A. Introduction...15 A 100 Objective...15 B. Marking...15 B 100 General...15 B 200 Rotation Marker...15 C. In-service condition assessment...15 C Sec. 2 Design Assessment A. Documentation...16 A 100 General...16 A 200 Documentation from the user...16 A 300 Documentation from the rope manufacturer...16 A 400 Quality system...16 A 500 Sub-contractors...16 A 600 Manufacturing specification...16 Sec. 3 Materials A. Fibre ropes...18 A 100 Load-bearing yarn...18 A 200 Sheathing...18 B. Terminations...18 B 100 Protection cloth for spliced eyes...18 B 200 Termination hardware...18 C. Mechanical properties...18 C 100 Minimum Breaking Strength (MBS)...18 C 200 Change-in-length performance...18 C 300 Calculation of stiffness...19 C 400 Post-Installation Stiffness...19 C 500 Dynamic Stiffness...19 C 600 Static Stiffness...20 C 700 Splice integrity...20 C 800 Fatigue performance...20 C 900 Torque and rotation characteristics...20 C 1000 Resistance to soil ingress...21 C 1100 Weight pr. Unit Length (W/L)...21 C 1200 Maximum temperature due to Hysteresis Heating...21 Sec. 4 Measuring and Expressing Rope Change-in-Length Properties A. General...22 A 100 Introduction...22 A 200 Stretch and Strain...22 A 300 Spring Rate and Stiffness...22 Sec. 5 Specification of Testing A. General...23 A 100 General A 200 Data recording and measurement accuracy B. Testing of Yarn...23 B 100 General C. Testing of subrope...23 C 100 General C 200 Number and selection of subrope test specimens D. Testing of Fibre Rope and Fibre-Rope Assembly...23 D 100 Number and selection of fibre-rope test specimens E. Test methods...24 E 100 Introduction E 200 Testing of change-in-length performance on subropes E 300 Testing of breaking strength on fibre-rope assembly or subrope E 400 Testing of splice integrity on subropes E 500 Fatigue E 600 Testing of Weight/Unit Length E 700 Soil ingress resistance E 800 Testing of maximum temperature due to Hysteresis Heating F. Termination hardware...25 F 100 Non-destructive testing F 200 Mechanical testing F 300 Fibre-rope assembly CH. 3 CLASSIFICATION AND CERTIFICATION 27 Sec. 1 Classification and Certification A. Classification...29 A 100 General B. Certification of mooring analysis...29 B 100 General C. Certification of Fibre-Rope Assemblies...29 C 100 Introduction C 200 Main elements in certification C 300 Additional qualification activities C 400 Deviations and test waivers Sec. 2 Work process A. General...30 A 100 Introduction A 200 Request for certification A 300 Pre-production Meeting B. QA/QC Review...30 B 100 General B 200 Quality Review Report B 300 Design assessment C. Testing...30 C 100 General C 200 New techniques (under development) D. Start up of production...31 D 100 General E. Survey during production and testing...31 E 100 The survey comprises the following main elements F. Documents issued or attested by DNV...31 F 100 General G. Certificates...31 G 100 Introduction... 31

6 Page 6 Contents G 200 Certificates for Load-Bearing Yarns...32 G 300 Fibre-Rope Assemblies...32 App. A Fibre-rope Stretch and Stiffness A. Background...33 A 100 Basic Rope Change-in-Length Properties...33 A 200 Mooring Line Change-in-Length Properties...33 A 300 Original Spring Rate and Construction Stretch...33 A 400 Static Spring Rate and Continued Original Spring Rate.33 A 500 Polymer Stretch...34 A 600 Sustained Elastic Stretch and Dynamic Spring Rate...34 App. B Quality Review Report App. C Example of Certificate Format... 37

7 OFFSHORE STANDARD DNV-OS-E303 CERTIFICATION OF FIBRE ROPES FOR OFFSHORE MOORING CHAPTER 1 INTRODUCTION CONTENTS PAGE Sec. 1 General... 9 Veritasveien 1, NO-1322 Høvik, Norway Tel.: Fax:

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9 Ch.1 Sec.1 Page 9 SECTION 1 GENERAL A. General A 100 Introduction 101 This Standard covers certification of fibre-rope products for offshore mooring. 102 Chapter 1 (this chapter) provides a general introduction with overview, definitions, general provisions and references relevant for Chapter 2 and Chapter 3. Chapter 2 provides the technical provisions of this standard. Chapter 3 covers the process of certification. A 200 Important notice 201 Apparent compliance to the provisions of this standard does not imply that a product is certified; nor does apparent non-compliance to certain provisions imply that a product cannot be certified. Certification is a matter of judgement based on the complete set of provisions that are given in this standard. A 300 Scope 301 This standard specifies the requirements for the materials, design, manufacture and testing of offshore mooring fibre ropes, which are subjected to classification or certification. It may also serve as a technical reference document in contractual matters between user and manufacturer. 302 This standard is applicable for fibre ropes used as taut mooring lines on column-stabilised units, ship-shaped units, loading buoys, deep draught floaters, and other floating bodies. This standard may also be used for semi-taut and catenary mooring systems where only a portion contains fibre-rope segments. It does not apply to hawsers used to moor tankers to loading or off loading buoys. 303 Typical applications are long-term mooring of floating production systems and mooring of mobile offshore units. It also applies to fibre-rope mooring lines for other offshore installations, such as wave-, wind- or current energy plants. 304 Provided appropriate qualification of the resistance to soil ingress is carried out based on DNV-RP-A203, sea-bed contact in the installation phase (or pre installation to the sea bed) can be permissible under this standard. 305 Provided appropriate qualification is carried out based on DNV-RP-A203, a permanent mooring system can be installed without inserts for in-service examinations and testing. A 400 Objective 401 The objective of this standard is to ensure uniform quality level of fibre ropes manufactured for offshore applications. A 500 Application 501 This standard is applicable to fibre ropes that are manufactured using polyester-yarn materials. 502 Fibre-rope segments of mooring lines can be of various constructions. Some examples of different types of rope constructions are shown in Figure At the time of this standard, the most commonly used type of fibre rope for offshore moorings consists of parallel subropes held together by a braided jacket. The subropes consist of strands in helical (laid) or braided arrangement. The helical subropes typically use three or four strands, whereas the braided subropes typically use eight or twelve strands. The size and number of subropes to make up the fibre rope varies between manufacturers. Rope constructions resembling steelwire rope are also used, either as subropes or as the fibre rope. 504 Fibre ropes shall be terminated with spliced eyes. 505 The spliced eyes should be fitted on steel thimbles. Thimbles act as the interface between the rope eye and the connecting (shackle or H-link) pin. The thimble should be a neat fit on the pin and the root diameter should be specified. 506 If the fibre-rope segment is connected directly to an H- link, then the H-link (with pin) is considered termination hardware and subject to certification under this standard. For other types of fibre-rope terminations than the spliced eye, none exist at the time of this standard with an appropriate level of qualification as defined in DNV-RP-A203. The same applies to other materials for termination hardware than steel. The fibre-rope assembly includes fibre rope with spliced eyes and termination hardware. If thimbles are used in the spliced eyes, then the connecting shackles (or H-links) are outside the scope of this standard and should be certified separately according to DNV-OS-E302. If the H-link is used without a thimble in the eyes then the H-link terminates the fibre-rope segment and shall thus be certified as part of the fibre-rope assembly. 507 The entire length of rope shall be submerged at all times during service. 508 Fibre-rope segments in mooring lines are normally protected by an outer sheathing. A soil filter is usually incorporated in this sheathing. 509 The sheathing shall be sufficiently dense to avoid sunlight to penetrate when in service in order to prohibit marine growth inside the rope. 510 Unless the protection against soil ingress has been duly qualified, fibre-rope assemblies shall not contact the sea bed during installation. 511 Provided the protection against soil ingress has been duly qualified, fibre-rope assemblies may be placed on the sea bed pending retrieval and final hook up. 512 The lower parts of the fibre rope shall not be in contact with the sea bed during service, nor be handled or left in service in water with emulsified particles that may be transported into the load-bearing rope by the water that seeps in and out during loading. The filter serves as protection for unloaded rope. The protection in the termination areas shall be qualified.

10 Page 10 Ch.1 Sec.1 given. The profile of the spool should also be specified. (A) Parallel-Subrope Rope. Figure 2 Illustration of spliced-eye termination with spool thimble. The D/d ratio range and eye angle are given as illustration. The actual design is part of the rope design as determined by the manufacturer. (B) Six-Strand Rope. (C) Thirty-Six-Strand Rope. Figure 1 Overview of types of rope 513 Fibre ropes are usually torque neutral, i.e. the rope does not exert torque when loaded. When it is desired that the fibre rope resists rotation of the connection to a steel-wire rope, a torque-matched rope is usually used. Torque matching implies that the torque/rotation exerted by the fibre rope matches the steel-wire rope such that spinning is avoided. It may be desirable that the fibre rope resist spinning in order to maintain the fatigue life of the wire-rope. 514 The user may specify the type and dimensions of termination hardware, and quality and strength of the materials used. If not, the manufacturer should propose the type and quality, suitable for the intended service. 515 The eye size is usually determined as the dimension from the inside back of the eye to the crotch of the eye with two legs of the eye close together. The tolerance should be - 0% / + 20% of the dimension stated by the manufacturer if this is not B. References B 100 General 101 In case of conflict between requirements of this standard and a reference document, the requirements of this standard shall prevail. 102 The latest edition of the referenced document (including amendments) should apply. B 200 Normative References 201 The referenced documents listed in Tables B1 through B3 include provisions, which through reference in the text constitute provisions of this standard. Table B1 DNV Offshore Standards Reference Title DNV-OS-E301 Position Mooring. DNV-OS-E302 Certification of Offshore Mooring Chain. DNV-OS-E304 Certification of Offshore Mooring Steel Wire Ropes. DNV-OS-E302 and DNV-OS-E304 are due to be issued. Until issued, Certification Notes No. 2.6 and Certification Notes No. 2.5 are applicable. Table B2 DNV Recommended Practice Reference Title DNV-RP-A203 Qualification Procedures for New Technology. Table B3 Other Reference Reference Title CI 1503 Test Method for Yarn-on-Yarn Abrasion. B 300 Informative references 301 The referenced documents listed in Tables B4 through B6 include information that may be useful to the users of this standard. Table B4 DNV Offshore Standards Reference Title DNV-OS-C401 Fabrication and Testing of Offshore Structures. DNV-OS-C501 Composite Components.

11 Ch.1 Sec.1 Page 11 Table B5 DNV Offshore Service Specifications Reference Title DNV-OSS-101 Rules for Classification of Offshore Drilling and Support Units. DNV-OSS-102 Rules for Classification of Floating Production and Storage Units. DNV-OSS-401 Technology Qualification Management. Table B6 Other References Reference Title API RP 2SK Design and Analysis of station-keeping systems for Floating Structures. API-RP2SM Recommended Practice for Design, Manufacture, Installation, and Maintenance of Synthetic Fibre Ropes for Offshore Mooring. ASTM D Standard Test Method for Wet and Dry Yarn-on Yarn Abrasion Resistance. CI Test methods for fibre rope. ISO Fibre ropes for offshore station-keeping Polyester. OCIMF Guidelines for Purchasing and Testing of SPM Hawsers. C. Definitions C 100 Verbal forms 101 Shall: Indicates a mandatory requirement to be followed for fulfilment or compliance with the present standard. Deviations are not permitted unless formally and rigorously justified, and accepted by all parties. 102 Should: Indicates a recommendation that a certain course of action is preferred or particularly suitable. Alternative courses of action are allowable under the standard when agreed between contracting parties, but shall be justified, documented and approved by DNV. 103 May: Indicates permission, or an opinion, which is permitted as a part of conformance with the standard. 104 Can: Indicates a conditional possibility. C 200 Terms 201 MBS: Minimum breaking strength. The specified minimum force that shall be achieved in the break testing. The MBS is a requirement, i.e. not a property of the fibre-rope assembly. 202 AVS: Average strength, as determined by the average of five break tests. 203 Change-in-length performance: The stretch and cyclic stiffness of the fibre rope as function of loading sequence and time. 204 Stretch: The change in rope length under tension. It is denoted ΔL and has the dimension of length Strain: The non-dimensional expression of stretch; the ratio of stretch to the original length before applying tension. It is denoted ε. 206 Stiffness: The ratio of change in force to change in strain. When normalised with the average strength it is dimensionless. 207 Static Stiffness: Ratio of change in force to change in length when tension is either increased or reduced. 208 Post-installation stiffness: Resulting static stiffness that may be used in analysis for the case where the maximum design storm occurs immediately after installation. 209 Dynamic stiffness: Maximum stiffness of the mooring lines, which applies when the mooring system is subject to the cyclic loading of a maximum design storm. 210 Fibre rope: The full-size rope without splices, constituted by all subropes and sheathing. 211 Sheathing: Protective jacket and soil barrier. 212 Fibre-rope segment: Finished fibre rope with spliced terminations, and splice-area protection. 213 Fibre-rope assembly: Fibre-rope segment with designated termination hardware. 214 Termination hardware: The steel component inserted in the rope eye to transfer the line loads from the fibre-rope segment to the rest of the mooring line. The spool thimble is most commonly used. 215 In-service condition assessment scheme: Inspection plan and activities performed regularly during the service life in order to control the condition of the mooring system. 216 User: The company that buys the fibre-rope assemblies from the manufacturer. 217 Mooring line: The entire line that transfers tension between the floating unit and the anchor. 218 MODU (mooring) system: Mooring system utilised by mobile units such as Mobile Offshore Drilling Units; characterised by intermittent use of the mooring lines that allows hands-on inspection at limited time intervals. 219 Permanent (mooring) system: Mooring system that is installed for a design life of five years or more. 220 I&T P: Inspection and test plan, which is a plan for the various steps in making the fibre-rope assemblies, describing the involvement of QA department and external surveyor. 221 I&T P sheet: A one-page sheet reflecting important survey steps and which particular steps have been carried out for a particular fibre-rope assembly. C 300 S INST S STATIC S DYN T MIN T MEAN+LF Symbols T MEAN+LF+WF W/L The post-installation stiffness is defined as the resulting static stiffness from the completed retraction at installed tension up to the peak storm cycle after sustained elastic stretch. The Static Stiffness is defined as the stiffness of the mooring line in periods of moderate wave loading, after initial construction stretch has been taken out. The Dynamic Stiffness is defined as the maximum stiffness of the mooring line which is predicted when the mooring system is subject to the cyclic loading of a maximum design storm. Minimum tension in the fibre rope during a storm with 100-year return period. Tension caused by static forces generated by wind, current and wave drift forces; and tension caused by low frequency motions generated by wind and waves in a storm with a return period of 100 years. Tension caused by static forces generated by wind, current and wave drift forces, including tension caused by low frequency motions generated by wind and waves; and tension generated by wave frequency motion in a storm with a return period of 100 years. Weight per unit length.

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13 OFFSHORE STANDARD DNV-OS-E303 CERTIFICATION OF FIBRE ROPES FOR OFFSHORE MOORING CHAPTER 2 TECHNICAL PROVISIONS CONTENTS PAGE Sec. 1 General Sec. 2 Design Assessment Sec. 3 Materials Sec. 4 Measuring and Expressing Rope Change-in-Length Properties Sec. 5 Specification of Testing Veritasveien 1, NO-1322 Høvik, Norway Tel.: Fax:

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15 Ch.2 Sec.1 Page 15 SECTION 1 GENERAL A. Introduction A 100 Objective 101 This section describes documentation requirements and technical requirements to polyester fibre ropes applied in position mooring. B 100 General 101 Each fibre-rope assembly should be marked at each end with a unique identifier traceable to appropriate certification. B 200 Rotation Marker 201 All fibre-rope segments shall include a conspicuous length-ways marker in order that any undue rotation in installation or in early operation can be observed by ROV inspection. An alternative would be for at least two strands in the braided jacket, one left hand, and one right hand to be made from durable, water-resistant-coloured yarns. C. In-service condition assessment B. Marking C At present, the industry relies on scheduled retrieval of inserts for inspection and testing for condition assessment. It is a requirement of this standard that the condition of the fibrerope assemblies be controlled during service. 102 The methods and techniques for controlling the condition of the fibre-rope assemblies during service shall be described in the in-service condition assessment scheme.

16 Page 16 Ch.2 Sec.2 SECTION 2 DESIGN ASSESSMENT A. Documentation A 100 General 101 This section covers documentation requirements. 102 The design verification aims at confirming that the fibrerope construction and termination design satisfies the specified design conditions, codes and standards. 103 The work consists of review of specifications, drawings, calculations, test reports and other data supplied by the user and the manufacturer documenting the strength and serviceability of the actual fibre rope segment with termination hardware. An overview of the required documentation is listed in Tables A1 and A A design verification carried out on a fibre-rope assembly is only valid for that specific fibre-rope assembly. 105 For permanent moorings, the design verification is only valid for the designated location. A 200 Documentation from the user 201 This section provides the requirements to documentation from the user. A summary of required documentation is found in Table A1. Table A1 Documentation requirements - End User User specification: In-service inspection scheme. Use of inserts. Mooring-system lay out and type of service. 1) Type of installation, (Mobile offshore unit, e.g. drilling unit; Floating production and/or storage unit, e.g. ship, semi-submersible and spar). 2) Drawings of complete mooring systems, incl. number of anchors, number and length of fibre ropes, line configuration, etc. 3) Minimum line tension T MIN. 4) Pretension for the installed mooring system. 5) Line tension, which is the sum of mean and maximum (extreme) low-frequency tension T MEAN+LF. Mean tension is the sum of pretension and tension caused by the static wind, current and wave drift loads. 6) Maximum line tension T MEAN+LF+WF. 7) Design life. 8) Minimum bending diameter during transport and installation. 9) Installation test load for anchors if the fibre-rope assembly is used for installation of the anchor. 10) Torque and rotation characteristics of connecting wire rope. 11) Highest and lowest occurring sea-water temperature. 12) Evaluation of sea-bed particles (e.g. sand and mud) experienced by the fibre-rope assembly during installation. 13) Marine growth assessment report for the location of permanent systems. Mixing torque-generating steel-wire rope with torque neutral fibre rope is mainly a concern for the fatigue life of the steel-wire rope. A 400 Quality system 401 Fibre-rope manufacturers should have a quality system in operation. A 500 Sub-contractors 501 Main sub-contractors should operate a quality system that is formally accepted by the fibre-rope manufacturer. A 600 Manufacturing specification 601 The manufacturing specification shall give complete manufacturing instructions for each step in the production process. Information may be found in OCIMF Guidelines for Purchasing and Testing of SPM Hawsers, section D The rope manufacturer shall completely document all splicing procedures. The same splicing procedures shall be followed when splicing the test specimens as for the delivery. Information may be found in OCIMF Guidelines for the Purchasing and Testing of SPM Hawsers, Section D-8. A summary of documentation requirements are given in Table A2: Table A2 Documentation requirement - Rope Manufacturer Procedure for handling and installation. Manufacturing specification describing how the rope is manufactured including manufacturing specification for splices. Rope specification: 1) Type of fibre rope construction 2) Type of termination 3) Weight pr. Unit Length of fibre rope 4) Minimum Breaking Load 5) Post-Installation Stiffness 6) Static Stiffness 7) Storm Stiffness 8) Residual Performance - Intermediate 9) Residual Strength - End of fatigue life 10) Total Elongation of Fibre Rope Segments. A 300 Documentation from the rope manufacturer 301 This section provides the requirements to documentation from the manufacturer for the purpose of certification of the fibre-rope assemblies. 302 If any of the components in the mooring line are not torque neutral, then an analysis showing that the components are torque matched shall be submitted.

17 Ch.2 Sec.2 Page 17 Table A2 Documentation requirement - Rope Manufacturer (Continued) Testing specification: 1) Weight pr. Unit Length of fibre rope 2) Minimum Breaking Load 3) Post-Installation Stiffness 4) Static Stiffness 5) Storm Stiffness 6) Fatigue test 7) Filter test 8) Any requirements pertaining to qualification for special service. Test reports Quality plan for rope manufacturing. Specification of load bearing yarns. Load bearing yarn properties, manufacturer s doc. Load bearing yarn properties, verification of yarn supply. Documentation of material for the fibre rope sheathing, consisting of filter and jacket. Manufacturer and manufacturing plant Designation Sheathing weight/thickness Permeability UV resistance Hydrolysis resistance Resistance to chemicals. Materials for spliced-eye protection. Documentation of the termination hardware material, production and repair methods. Documentation of the termination hardware s structural strength. Description of rope manufacturer s quality system. Rope manufacturer s approval of sub contractors quality system.

18 Page 18 Ch.2 Sec.3 SECTION 3 MATERIALS A. Fibre ropes A 100 Load-bearing yarn 101 The rope manufacturer should specify the following for the yarn to be used in the construction of the load-bearing part of the rope: Manufacturer and manufacturing plant Yarn designation Yarn weight per unit length Yarn breaking strength Wet yarn-on-yarn abrasive performance Marine finish designation. 102 The linear density of yarns should be stated in dtex, which is grams per metres. A 200 Sheathing 201 The sheathing consists of the following: The rope jacket The soil-ingress protection, if applicable. 202 The manufacturer, manufacturing plant, and designation of yarns and fabric shall be identified. The sheathing weight or thickness shall be stated. 203 The permeability of the sheathing with respect to water and solids shall be stated. 204 The effect of UV light, of intensity corresponding to that experienced during operation, and after a time corresponding to the design life, shall be stated. 205 The effect of the chemicals listed as effluents from the installation shall be stated. B. Terminations B 100 Protection cloth for spliced eyes 101 For spliced-eye terminations, protective cloth will normally be required between the eye and the termination hardware that fits through the eye. Such cloth should provide low friction and high wear resistance. 102 If a thin cover of elastomeric material is used to protect against chafing, then it shall be elastic such that the rope is not constrained from stretching or bending. 103 If a thick cover of elastomeric material is used to encapsulate the eye, it shall be applied over a tape or cloth that covers the eye and prevents direct adherence to and penetration onto the load-bearing rope. If the fibre rope segment is intended to be opened for later inspection, such as a service insert or test specimen, then the segment should be equipped with sufficient cloth beneath the PU coating such that the splice area can be opened as a loose carcass. 104 The splices and eyes should have the same or better resistance to soil ingress as the fibre rope. B 200 Termination hardware 201 Termination hardware is required to fit and support the eye and should be made of steel. 202 Pins shall be made from forged steel in compliance with DNV-OS-E The material in thimbles should comply with DNV-OS- E The material in H-links should comply with DNV-OS- E Manufacturing by welding should comply with the requirements of DNV-OS-C Other materials, such as polymers and fibre-reinforced composites can be used if they have been qualified based on DNV-RP-A203. If the spool thimble is turned from solid plate, then Z quality shall be used. Guidance on composite components may be found in DNV-OS- C501. C. Mechanical properties C 100 Minimum Breaking Strength (MBS) 101 The Minimum Breaking Strength (MBS) of the fibrerope assembly shall be stated by calculation and verified by testing. The MBS should be stated in kn. The strength, ductility and toughness of the termination hardware should be such that it can withstand the actual breaking strength of the rope assembly. 102 If termination hardware produced as part of the supply is not available at the time of testing, then the properties of the termination hardware can be demonstrated through non-linear FEM analysis. It is the responsibility of the manufacturer to define the load case that acts on the termination hardware. C 200 Change-in-length performance 201 For determination of the change-in-length performance of the fibre-rope assemblies, it is crucial that the testing reflect the actual use scenario of the mooring system. Thus, the testing shall be specified according to the measurement results that are needed to verify the mooring analysis. 202 This sub-section describes basic performance characteristics that should be addressed. It is recommended that more detailed analyses be carried out using exhaustive change-inlength performance data for the actual rope. Further information about the change-in-length behaviour of fibre ropes can be found in Appendix A. 203 The test load levels shall be based on key data from the mooring design analysis. The forces referred to are illustrated in Figure 1.

19 Ch.2 Sec.3 Page 19 Total line tension in a storm with 100-year return period ES Pretension Tension due static loads from wind, current and wave drift forces Tension due to wind and wave generated low frequency motions Tension due to wave frequency motions Force vs. strain plot EF T MIN Resulting static stiffness T MEAN T MEAN+LF T MEAN+LF+WF Figure 1 Illustration of key lead levels. C 300 Calculation of stiffness 301 Dynamic stiffness should be calculated through the peak and trough points of the cycle, using the average rope length during the cycle as basis. This is illustrated in Figure 2. TF TS PS Figure 2 Illustration of peak-to-trough dynamic stiffness With input in kn force and % strain, the dynamic stiffness formula becomes: (200 + PS + TS) ( PF TF) S = 2 ( PS TS) AVS where PF = Peak force TF = Trough force PS = Peak strain TS = Trough strain AVS = Average Strength 302 For so-called static loading, the stiffness is calculated using the beginning point and end point, where the rope length at the beginning point is taken as basis. This is shown in Figure 3. PF Dynamic stiffness Force vs. strain plot BF Figure 3 Illustration of resulting static stiffness With input in kn force and % strain, the static stiffness formula becomes: (100 + BS) ( EF BF) S = ( ES BS) AVS where BS EF = End force. BF = Beginning force ES = End strain BS = Beginning strain AVS = Average Strength These input values are read out from the data logging file. Normalisation of stiffness (with the average strength) is optional. C 400 Post-Installation Stiffness 401 The Post-Installation Stiffness (S INST ) shall be determined by testing. The post-installation stiffness is calculated as a resulting static stiffness using the following values: Trough values: Force and stretch after retraction at installed tension. Peak values: Peak force and peak stretch from dynamic stiffness measurements. The peak values are obtained when the sustained elastic stretch corresponding to maximum storm duration has been imposed, such that the maximum length can be determined for offset calculations. C 500 Dynamic Stiffness 501 The Dynamic Stiffness (S DYN ) is defined as the maximum stiffness of the mooring line which is predicted when the mooring system is subject to a maximum design storm. It is characterised by comparatively short periods and small amplitudes. It shall be determined by testing. LOWER LOAD LEVEL The lower load level shall be equal to the sum of mean and maximum low frequency tension (T MEAN+LF ) specified for the mooring system. Mean tension is the sum of pretension and tension caused by the static storm wind, current and wave drift loads.

20 Page 20 Ch.2 Sec.3 HIGHER LOAD LEVEL The higher load level shall correspond to the maximum load (T MEAN+LF+WF ) determined from the mooring analysis for the design storm condition, with a 100-year return period. 502 Normally the maximum line tension for an intact mooring system is applied as the upper load level in connection with determination of S STORM. If the result of the mooring analysis with the single line failure shows significantly higher line load, then the storm stiffness at this higher load should be determined. C 600 Static Stiffness 601 The Static Stiffness (S STATIC ) is explained as the stiffness of the mooring line after a time in service, in periods of moderate wave loading, wind and current, and should be determined by testing if needed in the analyses. It is characterised by comparatively long periods and large amplitudes. The static stiffness can be used to represent the mooring line stiffness after it has been possible to re tension the system such that the post-installation stiffness becomes over conservative. It is recommended that the static stiffness is measured both before and after test for dynamic stiffness that uses the maximum design storm conditions. LOWER LOAD LEVEL The lower test load level shall be equal to the specified minimum tension limit during storm condition T MIN, specified for the mooring system. HIGHER LOAD LEVEL The higher test load level shall correspond to the maximum load (T MEAN+LF ) determined for mean tension and low-frequency motion. Force Original stiffness. Post-installation stiffness. Static stiffness.. Dynamic stiffness. T MEAN+LF+WF T MEAN+LF Maximum installation force T MEAN Pre tension T MIN Stretch Figure 4 Example illustration of loading cycles during change-in-length tests, with corresponding stiffnesses. 602 Mooring systems are designed to survive a single line failure. If the time to replace the line is significant, it will have to be considered if the maximum line tension representing the upper load level should be represented by the single line failure case. C 700 Splice integrity 701 Subrope testing and the cyclic fatigue test of the fibre rope assembly shall be used to determine that the splice design is self locking. The number of cycles to lock the splices shall be stated and verified by testing. C 800 Fatigue performance 801 The Fatigue performance shall be verified for permanent systems by fatigue testing of a new test specimen with subsequent examinations and tests. 802 The resistance of the splices against slipping out shall be documented as part of the post-testing examination of the fatigue test sample. 803 The requirement to fatigue testing of a rope assembly does not apply to MODU moorings. C 900 Torque and rotation characteristics 901 The torque and rotation characteristics are defined as the resulting torque and/or rotation that the rope exerts when loaded. 902 The torque and rotation characteristics shall be documented and verified by testing. 903 Alternatively for ropes that are designed to be torque neutral, documentation that the rope is inherently torque neutral shall be provided.

21 Ch.2 Sec.3 Page 21 C 1000 Resistance to soil ingress 1001 The resistance to soil ingress, if applicable, shall be stated and verified by testing and/or qualification as outlined in DNV-RP-A203. C 1100 Weight pr. Unit Length (W/L) 1101 The Weight pr. Unit Length (W/L) of the fibre rope in air should be documented by calculation and verified by testing. The weight pr. unit length in sea water should be stated. The W/L should be stated in kg/m. C 1200 Maximum temperature due to Hysteresis Heating 1201 The maximum temperature due to hysteresis heating is defined as the maximum temperature obtained in the fibre rope assembly during cyclic loading. For ropes in standard use any hysteresis heating is normally not expected It shall be verified that the maximum temperature due to hysteresis heating is 10ºC below the safe long-term temperature.

22 Page 22 Ch.2 Sec.4 SECTION 4 MEASURING AND EXPRESSING ROPE CHANGE-IN-LENGTH PROPERTIES A. General A 100 Introduction 101 This section covers the most up-to-date definitions of the properties that govern change-in-length performance of fibre rope. These properties are defined as separate entities in order to describe and measure individual contributions to overall length changes." The separate definition of (visco-elastic) properties is done in order to aid the understanding of change-in-length behaviour. It is not required in order to perform the basic analyses and tests described in Section 3 and Section 5, but may be useful in more advanced analyses and tests. 102 The change in length properties of a fibre rope can generally be determined by simple test procedures. 103 As discussed in Appendix A, the important properties in fibre-rope change-in-length performance are: εp εc So Ss Sd εse Polymer Creep Strain, a function of time under tension Rope Construction Strain, a function of highest applied tension Original stiffness, during first loading or during loading to a load which is higher than any previous load Static stiffness, during subsequent loadings less than or up to the highest previously applied load Dynamic stiffness, after a number of relatively fast load cycles Sustained Elastic Strain, which occurs during cycling and is recoverable after cycling. A 200 Stretch and Strain 201 Stretch ΔL is the change in rope length under tension and has the dimension of length. The magnitude of stretch measured in testing is proportional to specimen length. 202 During testing, the gauge length over which stretch is measured should only include that portion of the specimen which is unaffected by splices and eyes. 203 The gauge length is the length between extensometer fixation points when a subrope is tested in the laboratory. As the rope is loaded during installation and use, this gauge length will change accordingly due to rope stretch. 204 When the rope is new and tensioned to reference tension for the first time, the gauge length defines the reference length, denoted L Strain ε is the non-dimensional expression of stretch, the ratio of stretch length under tension to the original length before applying tension. ε = ΔL / Lo where ε = strain ΔL = stretch Lo = original length, for testing this is the reference length 206 Thus for example, when polymer stretch is measured in a test, it should be divided by reference length and expressed as polymer strain εp. This is sometimes called creep. where εp = ΔLp / Lo εp = polymer strain Δlp = stretch due to polymer strain 207 Construction stretch should be divided by reference length and expressed as rope construction strain εc. εc = ΔLc / Lo where: εc = construction strain ΔLc = stretch due to construction stretch The terms extension and elongation are sometimes used for stretch and strain. Because those terms are not intuitive and are used in various, sometimes opposing manners by different parts of the rope using community, their use here is discouraged. A 300 Spring Rate and Stiffness 301 Spring Rate K is the ratio of change in tension to change in stretch. The dimensions are force / length. K = ΔF / ΔL where K = spring rate ΔF = change in applied tension 302 Stiffness S is the non-dimensional form of spring rate. The stiffness property can be applied to ropes of any length and any strength. S =(ΔF/AVS) / (ΔL/Lo) where S = stiffness AVS = average strength It is preferred that average strength (AVS) be used as the basis for normalising stiffness. The minimum breaking strength is a requirement, not a property of the rope. 303 The spring rate of any particular mooring line can then be readily determined by K = S AVS / L where AVS = average strength of mooring line L = length of mooring line 304 The use of these change-in-length properties in mooring system design is discussed in DNV-OS-E301. DNV-OS-E301 is due to be revised to contain this information and other updates. Until issued, further information may be found in the 2008 revision of API-RP2SM.

23 Ch.2 Sec.5 Page 23 SECTION 5 SPECIFICATION OF TESTING A. General A 100 General 101 This section covers specification of testing to verify the properties and performance of the fibre-rope assemblies to be manufactured and delivered. 102 The reference tension to be used for the testing is 1% MBS. 103 When testing subropes, the force levels shall be based on the MBS of the fibre-rope assembly divided by number of subropes. Since the MBS is a specified force level and not a physical property, the MBS divided by number of subropes will differ from that of the subrope. A 200 Data recording and measurement accuracy 201 Force, time, displacement and stretch should be logged at a sufficient rate when measurements are taken. Consideration should be given to the required accuracy, whilst avoiding excessive data files. The following sampling rates may be taken as advice: not the results are in compliance with yarn manufacturer s certificate. 102 The testing should be performed according to OCIMF, Guidelines for the Purchasing and Testing of SPM Hawsers, Appendix II. 103 Four separate bobbins from different pallets should be tested; one from the beginning, two from the middle and one from the end of each lot. Three tests should be performed on each 10-kg bobbin. C. Testing of subrope C 100 General 101 Provided production settings are not changed, the samples for testing may be produced and tested before production of the delivery. 102 It is the rope manufacturer s responsibility to take sufficient number of subrope samples in order to complete the necessary tests to document the fibre-rope properties. This includes necessary spare length if other testing should be required later. 103 The following number and selection of subrope specimens should be followed for certification: Break test at loads above 75% MBS: Dynamic stiffness: Fast changes in load level: Initial parts of static measurements: Final parts of static measurements: 0.5 seconds between points points per cycle. 2 seconds between points seconds between points. 1 minute - 1 hour between points. C 200 Number and selection of subrope test specimens. Table C1 Requirements to subrope test specimens for certification Type of test: Number of test specimens: Change-in-length performance. 5 subropes. Breaking strength. 5 subropes. Splice integrity. 3 subropes. Weight per unit length. 2 subropes. 202 Change-in-length measurements should be performed on subropes, with the extensometer attached to the same strand at both ends. For change-in-length measurements on fibre rope, the extensometer should be attached on the outer jacket with fixations that are gripping or squeezing the whole cross section. However, measurement on subrope is the preferred method, and the accuracy when measuring on fibre rope shall therefore be justified. It must be ensured that the jacket follow the changes in length of the load-bearing subrope bundle. The gauge length for stretch measurements needs to be commensurate with the accuracy of the length-measurement device. Advice is provided in CI 1500, Table 1M page 13 and Appendix A. B. Testing of Yarn B 100 General 101 The material test shall be carried out for each lot or for each kg, whichever is less. It shall be stated whether or 201 The change-in-length and strength measurements shall be performed identically on each subrope sample. For helical subrope constructions, three S and two Z specimens should be used. 202 For helical subropes, the splice integrity test specimens should be one S and two Z; and the weight test specimens shall be one S and one Z. D. Testing of Fibre Rope and Fibre-Rope Assembly D 100 Number and selection of fibre-rope test specimens 101 Provided production settings are not changed, the samples for testing may be produced and tested before production of the delivery. 102 It is the rope manufacturer s responsibility to take sufficient number of samples of the completed fibre rope in order to complete the necessary tests to document the fibre-rope properties. This includes necessary spare length if additional testing should be carried out on behalf of the user. 103 The following number and selection of fibre rope test

24 Page 24 Ch.2 Sec.5 specimens should be followed for certification: Table D1 Requirements to fibre rope test specimens for certification Type of test: Number of test specimens: Breaking strength. 5 fibre-rope assemblies. Fatigue test. 1 fibre-rope assembly. Torque and rotation, if applicable. 1 fibre-rope segment. Soil ingress resistance, if applicable. 1 fibre rope or -segment. Weight per unit length. 1 fibre rope. 104 The lowest result defines the actual breaking strength of the delivery. 105 The test requirements for torque and rotation characteristics shall be determined on a case-by-case basis. 106 The test requirements for soil-ingress resistance testing shall be determined on a case-by-case basis. 107 Production parameters should not be changed after the manufacture of the test specimens. 108 The same set of termination hardware may be used for all tests that require a fibre-rope assembly to be tested. E. Test methods E 100 Introduction 101 All tests shall be described in the testing specification. The key load levels and other information from the mooring analysis needed to define the change-in-length performance testing shall be submitted to the manufacturer by the user. 102 Due to the dependence of the rope change-in-length performance on the actual loading, the testing specification should reflect the actual loading scenario as closely as possible. The test methods for change-in-length performance described in this section are given for guidance, as a starting point for establishing the testing specification for the specific delivery. A generic description of the individual characteristics that constitute the fibre-rope change-in-length behaviour is given in Appendix A. E 200 Testing of change-in-length performance on subropes 201 Since a MODU mooring system may be used in different locations and service scenarios, the change-in-length performance testing for MODU systems may be carried out based on API RP-2SM, ISO 18692, section B.3, or CI , Appendix A. 202 A basic test procedure for change-in-length performance for permanent mooring systems is presented in the following for guidance. The testing specification shall reflect the actual loading scenario for the mooring system, and the change-in-length test programme will therefore need to be expanded or adapted. 203 The subrope specimen should be pre soaked by complete immersion in fresh water overnight prior to testing. 204 The specimen should not have been previously loaded. 205 For establishment of the post-installed condition, the specimen should be loaded five times between reference tension and installation test load for anchors, or pre-tensioning load for installed system, whichever is the higher. On reduction of load during the last cycle, the force shall be maintained at the installed tension and the rope should be allowed to retract for 20 minutes at constant force. 206 For testing of dynamic stiffness the same specimen shall be loaded between the lower and higher load level with a period between 10 and 20 seconds for 130 cycles. 207 The dynamic stiffness shall be measured on the final 5 cycles. 208 For testing of static stiffness the same specimen should be loaded between the lower and higher load level for 130 cycles. 209 The static stiffness shall be measured on the final 5 cycles, using a period between 60 to 180 seconds. When measurements are not taken the cycling should be as fast as possible. It is recommended to measure the static stiffness both before and after measurement of the dynamic stiffness. 210 After the stiffness measurements, the specimen should be subject to a break test. 211 The following measurements should be taken: Force vs. stretch curve for the installation test cycles and retraction at installed tension Force vs. stretch curve for cycles 1-10, cycle 100 and last 10 cycles for dynamic and static stiffness. 212 The following should be reported: Post-installation stiffness between end of retraction and peak of final dynamic cycles Dynamic stiffness on final cycles and cycle period during measurement Static stiffness on final cycles and cycle period during measurement Breaking strength report requirements. E 300 Testing of breaking strength on fibre-rope assembly or subrope 301 The specimen shall be pre soaked by complete immersion in fresh water overnight. It should not have been previously loaded to more than 70% MBS. 302 Fibre-rope assemblies shall be break tested using termination hardware that is manufactured as part of the supply. 303 Recommended test procedure: 10 cycles between reference tension and 50% MBS Loading to failure. Above 75% MBS, the loading rate should be kept constant at approximately 50% MBS/min. The following should be reported: Force vs. stretch curve for cycles 1, 2 and 10 to 50% MBS Breaking force and force vs. displacement curve for the loading to break The rate of loading reported in kn/min for the region above 75% MBS Location of failure. 304 The specimen should fail on the free length or at the toe of the splice region. As applicable, the same specimen as used for change-in-length measurements may be used without re soaking. For fibre-rope assemblies, the diameter of thimble/h-link pin holes may be increased by machining to fit the loading pins of the test machine. A force-control test machine is not required. E 400 Testing of splice integrity on subropes The subrope specimen shall be pre soaked overnight prior to testing.