海洋工程锚链营运检验指南(4)

??Locally grouped broken wires in a single strand or adjacent strand may be due to local damage. Once begun, this type of damage will usually worsen.

9.3.2 Changes in rope diameter can be caused by external wear, interwire and interstrand wear, stretching or corrosion.

A localized reduction in rope diameter may indicate a break in the core. Conversely, an increase in rope diameter may indicate a swollen core due to corrosion.

9.3.3 Wear on the crown of outer strands in the rope may be caused by rubbing against fairleads, unit structure, or the sea bed depending on the location of the wear.

Internal wear between individual strands and wires in the rope is caused by friction and is accelerated by bending of the rope and corrosion.

9.3.4 Corrosion decreases rope strength by reducing the cross-sectional area and

accelerated fatigue by creating an irregular surface which invites stress cracking. Corrosion is indicated by: ??The diameter of the rope at fairleads will grow smaller; ??The diameter of stationary ropes may actually grow larger, due to rust under the outer layer of strands. Diameter growth is rare for mooring lines.

9.3.5 Deformation, i.e. distortion of the rope from its normal construction, may result in an uneven stress distribution in the rope. Kinking, bending, scrubbing, crushing and flattening are common wire rope deformations. Ropes with slight deformations will not lose significant strength. Severe distortions can accelerate rope deterioration and lead to premature failure. 9.3.6 Thermal damage, although rare for mooring ropes in normal service, may be indicated by discoloration. Prompt attention should be given to damage caused by excessively high or low temperatures. The effect of very low temperatures on wire rope is unclear except for the known detrimental effect on lubricants. 10. References 10.1 Wire Rope

API RP 2I and ISO-Standard 4309.

(Please see 9.1 regarding the ISO-Standard) 10.2 Chain

API RP 2I: \Floating Drilling Units\End of Document No.39

Page 1 of 3 IACS Rec. 1995/Rev.3 2009

No. 39

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Safe Use Of Rafts Or Boats For Survey

1. Access to Structures

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