API RP 2SM-2001 pdf download.Recommended Practice for Design, Manufacture, Installation, and Maintenance of Synthetic Fiber Ropes for Offshore Mooring.
3.3.4 Durability and Fatigue Factors which may limit the life of synthetic fiber ropes for deepwater mooring and which should be checked include hydrolysis, heating and internal abrasion, tension-tension fatigue and axial compressive fatigue. The possibility of creep rupture was commented on in the previous section. 3.3.5 External Abrasion and Cut Resistance Jacketing should be used on fiber ropes where external abrasion is expected to occur while in service and during installation and recovery (if applicable for movable tempo- rary moorings). Certain rope constructions may need a pro- tective jacket to keep the strength core strands together, such as parallel strands. In case a protective jacket is used, the interaction between the jacket and the rope core should be considered when evaluating rope properties, service life and installation/recovery procedures. Braided HMPEs, which have demonstrated to possess high wear resistance may be used without jacketing if it can be shown that the wear resis- tance will be adequate for the intended application. To date there have been no recorded incidents of detrimen- tal fishbite damage to large diameter fiber ropes, and there- fore this is not expected to be a concern for large deepwater fiber rope moorings. If damage due to fishbite becomes a concern for a specific application and/or location, means for minimizing such damage should be considered in the selec- tion and design of the fiber rope, and the frequency of subsea inspection may have to be increased.
4.2.2 Yarn Quality Quality control procedures stated in Section 7 of this docu- ment should be used to ensure that yarn quality is maintained. 4.2.3 Marine Finish Typically, synthetic fiber manufacturers apply a non-water soluble marine finish coating to polyester, nylon, and aramid marine ropes to enhance performance. Purposes of the marine finish include: • Increasing the initial strength (translational efficiency) of the rope. • Providing lubrication to assist bedding-in of the rope during initial tensioning. • Increasing the rope’s service life by reducing yarn-to- yarn abrasion. Minimum requirements on the quality of marine finish and its long-term durability are described below. A more detailed discussion on these requirements can be found in Appendix E. 18.104.22.168 Quality of Marine Finish Due to the potential importance of marine finishes on deepwater moorings, the following should be followed: a. Fiber, yarn and rope data used for design of deepwater moorings should explicitly denote whether the data was gen- erated from samples which included a marine finish, and give the descriptive designation of the marine finish with the man- ufacturer’s fiber certification. b. As part of the prototype rope fatigue qualification testing (6.3.6), post-test analysis of the fibers (see 22.214.171.124) should demonstrate that the finish remains effective during wet cyclic fatigue for at least the duration of the testing. In addi- tion, as part of the rope specification (6.2) the fiber or rope supplier should demonstrate that the marine finish remains effective in seawater for at least one year.
126.96.36.199 Long-Term Durability of Marine Finish Until such time as standard accelerated processes for finish analysis have evolved, marine finish effectiveness and dura- bility should be demonstrated by subjecting yarn or ropes to continuous seawater exposure (ASTM seawater or ocean field trials) for a fixed time period of at least 1 year, followed by: a. Measuring the post-exposure yarn-on-yarn abrasion cycles-to-failure and comparing with control yarns not exposed to the seawater environment. b. Measuring the post-exposure level of the marine finish and comparing with control yarns not exposed to the seawater environment. Note: Marine finish level should be determined by the fiber supplier, rope manufacturer or qualified third-party with adequate under- standing of analytical chemical techniques as well as the chemistry of the particular fiber and finish being evaluated. For permanent mooring applications the above testing should be repeated on yarns taken from fiber rope inserts whenever these inserts are removed as discussed in 9.3.3. In this way marine finish level in the ropes can be monitored throughout the life of the installation.