API RP 2SM:2001 pdf download
API RP 2SM:2001 pdf download.Recommended Practice for Design,Manufacture, Installation, and
Maintenance of Synthetic FiberRopes for Offshore Mooring.
4.6.10.2 UV Resistance
Polyester ropes have excellent resistance to UV light, and jacket design need not take account of this aspect. Uncovered aramid ropes may suffer degradation of surface yarns if exposed to [JV radiation awaiting installation or if permanently deployed, uncovered, in the upper few metres of water. In such cases an opaque cover is recommended.
4.6.10.3 MarIne Growth
Minor strength loss in synthetic fiber ropes caused by marine growth or its by-products has been reporled. Marine organisms with hard shells can grow between the rope jacket and the load bearing core and cause abrasion tlaiiiage to core yams. Soft marine growth may limit visibility and hence afTcct the ability of an ROV to inspect the rope. Marine growth may also influence the drag loading on the line and hence loadings on the whole mooring system. For operations where marine growth is a concern, the fiber ropes should be placed below the marine growth zone. If marine growth is to be removed mechanically this should be done in such a way that damage to the rope itself is avoided.
4.6.11 Snap Back at Failure
Considerable energy will he stored elastically in the tensioncd lines of a taut leg mooring and the safety implications for the crews and equipment. especially during handling and installation if one of thc lines was to brcak should be considered.
4.6.12 Effect of Water Depth
At 2,000 m (6.560 ft) depth, the hydrostatic pressure is 20 MPa (2.900 psi), which is about 2% of the strength of polyester or nylon yarns and a smaller fraction of the strength of the other yams. This would have a ncgligiblc ef fret on yarn mechanical properties, and would only be responsible for a small transverse strain and the accompanying axial strain on a rope.
5 Mooring Design and Analysis
5.1 GENERAL
This section is based on the recommendations given in API RP 2SK Ill. Sections 4 through S. Modifications needed to cover the case of synthetic fiber rope mooring lines arc provided below.
5.2 MOORING CONFIGURATiON
A mooring system with synthetic fiber ropes can be config. ured as either a taut.leg or a catenary system. The choice depends on many considerations which are beyond the scope of this document. A taut-leg mooring (TLM) has a smaller mooring footprint than the conventional catenary mooring system. This can be particularly important for the held layout of production installations in congested dcvclopmcnl areas. The taut leg mooring systems also difTer from conventional catcnary moored systems in that the anchor must resist substantial vertical load.
5.3 DESIGN CRITERIA
5.3.1 Maximum Tension Limits
Maximum tension limits and factors of safety for fiber rope should be the same magnitude as for steel and thus in accordance with 6.3.2 of API RP 2SK l1. hut with the breaking strength of the new rope defined as MRS as in 4.6.2 of this document.
5.3.2 Minimum Tension and Maximum Allowable Low Tension Cycles
The previous wjuIrmcnt for minimum teiisil iixi— mum number of low-tension cycles is no longer applicable to polyester fiber ropes as they are not susceptible to axial compression fatigue.
As a general guideline for aramid ropes during installation and throughout the service life of the mooring line, tension should not drop below 10% MRS more than 501) times. Fiber ropes may be designed to sustain more cycles or lower tensions than indicated above before severe strength loss occurs. However, test data should be provided for justification of relaxing this general guideline.
