API RP 2I:2008(2015) pdf download
API RP 2I:2008(2015) pdf download.In-service Inspection of Mooring Hardware for Floating Structures.
2.5.3 Limit in Number of Connecting Links
The number of connecting links in a moonng line should not exceed an average of one per 400 ft of outboard line length. Furthermore, the total number of connecting links in a mooring line should be no more than ten, excluding the connecting links at the anchor end.
2.5.4 Removal of Whole Chain
If a large number of links meets the discard criteria and these links are distnbuted in the whole length, the chain should be replaced with a new chain.
2.5.5 Re-welding of Loose Stud
Rewelding of loose studs in the field Is undesirable for the following reasons:
— welding in the field may produce hard heat-affected zones that are susceptible to cold cracking:
— hydrogen ernbnttlement may occur from sorption of moisture from the atmosphere or welding electrodes.
Weld repairs on loose studs should be delayed as long as possible. Where a few links are found with loose studs In a short section of a chain, it is recommended that this portion of the chain be cut out arid a connecting link put in.
If the major portion of the chain has loose studs, the chain should be scrapped. In the case where the chain is not too old, but contains many loose studs, the chain may be reconditioned onshore at a qualified chain manufacturer where the loose studs are rewelded at one end and the chain is heat-treated again. However, this practice cannot be apØied to Grade 4 chains, for which stud welding is normally prohibited.
Studs in chain links serve two purposes:
a) to avoid knots or twist problems during handling operations: and
b) to support the links and prevent the sides of the links from deflecting inward during tensile loading, thus preventing
high bending stresses in the chain.
It is important to keep the stud in place to accomplish the purposes just scussed. Although weld repair of loose studs should be cksoouraged, excessive stud movement can be prevented by carelul welding using the proper electrode, preheat, inlerpass temperature, and rate of cooling after weling. Some regulatory bodies permit field rewelding of studs in oil rig quality chains. However, they normally require the welding contractor to submit welding specifications for their approval prior to such weld repair.
2.5.6 GrInding
Any grinding to eliminate shallow surface defects should be done parallel to the longitudinal direction of the chain, and the groove should be well rounded and form a smooth transition to the surface. The ground surface should be examined by MPI.
2.5.7 Replacement of Mooring Jewelry
Replacements for mooring jewelry such as connecting links, anchor shackles, swivels, wire rope sockets, and pelican hooks should meet or exceed the original design and manufacture requirements.
2.6 Recommended Inspection Schedule
A chain inspection schedule should be based on the age, condition and operational history of the chain (ground chain versus rig chain over fairleader under high load) and type of operation.
In addition to the major inspections, chain and oonnecting hardware should be checked for visible defects frequently dunng anchor retrieval.
Special attention should be given to the long term operations where the inspection schedule is current at the start of the operation, but the inspection wil expire during the operation. For example. a development drilling will take 18 months to complete. but the inspection will expire ii 6 months after start of the operation. In this case, an inspection of the mooring system should be con&cted before the MOOU is moored on location or Mile the MODU is in operation.
2.7 SpecIal Event Inspection
Rigorous mooring Wispection is critical for operations in the areas of tropical cyclone where the probability of mooring failure can be much ligher. Also guidance is needed to address the reuse of the components from a mooring damaged by a tropical cyclone. Additional guidance for MODU mooring inspection in these areas can be found in Annex B.
3 Guidelines for In-service Inspection of MODU Mooring-wire Rope and Anchor Handling Equipment
3.1 Common Problems wIth MODU Mooring-wire Rope
Mooring-wire ropes receive rough treatment in service, which may result in vanous types of damage. Inspectors should be particularly attentive to the common wire rope problems described in the following paragraphs.
3.1.1 Broken Wires
3.1.1.1 Broken Wires at the Termination
Broken wires at the termination, even if few in nurrter, indicate high stresses at the termination and may be caused by incorrect fitting of the termination, fatigue, overloading, or mishandling during deployment or retrieval.
3.1.1.2 Distributed Broken Wires
The nature of the wire breaks is an important key to diagnosing wire rope problems. For example, a crown break on the top of the strand may indicate excessive tension. fatigue. wear, or oorrosáon Necking down at the broken end of the wire indicates failure in tension. Broken faces perpendicular to lhe axis of the wire indicate fatigue. Reduced cross sections of the wire breaks may irflcate corrosion and wear. An example of distributed crown breaks is given in Figure 9, and typical wire fractures are shown in Figure 10.
