海洋工程锚链营运检验指南(2)

验船师在阐明钢丝绳状况中应极其小心。 状况明显时接受或拒绝是比较容易 的。但两种状况之内的“灰色”区域是难于评估的。验船师必须根据所有获得的 证据作出正确的评估和技术判断。

通常，钢丝绳的服役年限或时间，除了作为验船师在确定检验范围时应考虑 的一个因素外，对接受或拒绝钢丝绳并没有直接的关系。 9.2 检验和检查 应进行 100%的外观检验和直径测量。 9.2.1 外观检验应对每根钢丝绳锚腿验证和记录下述项目 :

—断裂钢丝的性质和数量； — 接头处钢丝断裂情况； — 外部磨耗和腐蚀； — 钢丝断裂的集中程度； — 变形； — 股断裂； — 接头面积；

— 钢丝绳直径的减少，包括绳芯破断或挤出。 9.2.2 直径测量应以约 100m 的间距进行，并应由现场验船师来决定。如果

发现特别值得注意的部位，检验可集中在这些部位上，并应以更小的间距进行直

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径测量。 9.2.3 如果在下层部位中表明存在严重的内部腐蚀或绳芯的可能断裂或钢 丝破断，应视实际可能性进行内部检查。作为钢丝绳内部检查的指南，见 API RP 2I， 3.3.6.3。 9.3 钢丝绳损伤指南

钢丝绳失效原因可从所见到的钢缆损坏中推出。 钢丝绳失效的大部分类型简 述如下。

包括图像实例在内的， 较详细的资料可从 ISO—标准 4309 和 API RP 2I 获得。 9.3.1 接头处破断的钢丝表示其接头处存在高应力， 这可能由接头安装错误、 疲劳、过载、或敷设、回收过程中的操作错误等所造成

（ 1）分散型破断钢丝，由 API RP2I 图 9～12 可表明其破坏的原因。 绳股顶处冠部断裂或单根钢丝的破断可由过大的张力、疲劳、磨耗或腐蚀所 造成。

过大的张力可由钢丝断口的颈缩所表明。 疲劳由断裂面垂直于钢丝轴线所表明。 腐蚀和磨耗可由钢丝横剖面的减少所表明。

两股界面处谷部断裂表示绳股绷紧， 通常由破断的绳芯或使绳芯直径减少的 内部腐蚀所造成。

谷部断裂可能由高的载荷、紧的滑轮和相对于钢丝绳直径显得太小的滑轮所 造成。

（ 2）局部集中在单根股或相邻股中的断裂钢丝可因局部损坏所造成。

一旦形成，此种损伤通常将持续恶化。 9.3.2 钢丝绳直径的变化可由外部磨耗、钢丝间或股间磨损、拉伸或腐蚀所

造成。钢丝绳直径的局部减少可表明绳芯断裂。相反，钢丝绳直径的增加可表明

腐蚀导致绳芯胀大。 9.3.3 钢丝绳外层股冠部处磨耗可根据腐损部位由与导缆器、 平台结构或海

床间摩擦所造成。

钢丝绳内各股间或各根钢丝间的内部磨损是由互相摩擦造成的， 并因钢丝绳

弯曲和腐蚀加速磨损。 9.3.4 腐蚀减少横剖面面积从而降低钢丝绳强度， 腐蚀会招致应力裂纹的不

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规则表面从而加快疲劳。腐蚀可由下述情况表征: ? 导缆器处钢丝绳直径将变小；

? 静止不动钢丝绳直径实际上将增大， 是因外层股下锈蚀所致。 对系泊缆，

直径增大是很罕见的。 9.3.5 变形，即钢丝绳已出现与其正常结构不同的变化，可引起绳中不均匀

的应力发布。纽结、弯曲、摩擦、断裂和变平是钢丝绳通常的变形。稍有变形钢 丝绳的强度损失不大。严重的变形可加快钢丝绳的退化，并导致过早的破坏。 9.3.6 热损坏， 虽然它在锚泊钢缆正常营运中很少发生， 仍可用变色来表明。

对由过高或过低温度造成的损坏应给予及时的注意。 除了已知非常低的温度对润 滑剂会产生有害的影响外，其对钢丝绳的其他影响尚不清楚。

10 参考文献 10.1 钢丝绳 API RP2I 和 ISO—标准 4309。（关于 ISO 标准，见 9.1）

10.2 锚链 API RP2I“浮式钻井平台锚泊部件营运检查的推荐标准”。 No.38

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Guidelines for the Survey of Offshore Mooring Chain Cable in Use

1. Application and Purpose

The information herein is intended to provide guidance to Surveyors for inspection of position mooring systems which have been classed by the Society for Mobile Offshore Drilling Units. Temporary mooring equipment is to be surveyed under the Rules for Building and Classing Steel Vessels of the Classification Society. 2. Survey Interval, Purpose and Extent

2.1 Annual Surveys are to be conducted at approximately twelve (12) month intervals, with the vessel at operational draft, with the position mooring system in use.

2.1.1 The purpose of the Annual Survey is to confirm that the mooring system will continue to carry out its intended purpose until the next annual survey. No disruption of the unit's operation is intended. Ideally, the Annual Survey would be done during a relocation move. 2.1.2 The scope of the Annual Survey is limited to the mooring components adjacent to the winch or windlass. Depending on the mooring component visible from the unit, particular attention should be given to: Chain

- Wear on the chain shoulders in way of the chain stopper and windlass pockets; - Support of chain links in the windlass pockets.

Wire Rope

- Flattened ropes; - Broken wires;

- Worn out or corroded ropes.

The surveyor should determine if any problems have been experienced in the previous twelve (12) months period with the mooring system, e.g. breaks, mechanical damage, loose joining shackles, chain or wire jumping.

If the Annual Survey reveal severe damage or neglect to the visible part of chain or cable, a more extensive survey should be performed.

Typical damage warranting a more comprehensive survey could be: Chain

- Reduction in diameter exceeding 4%; - Missing studs;

- Loose studs in Grade 4 chain;

- Worn out cable lifters (i.e. gypsies) causing damage to the chain. Wire Rope

- Obvious flattening or reduction in area;

- Worn cable lifters causing damage to the wire rope; - Severe wear or corrosion; - Broken wires.

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2.2 Special Periodical Surveys are carried out at intervals of approximately five (5) years and will require extensive inspection, usually associated with a sheltered water visit. When considered necessary by the Society, the interval between Special Periodical Surveys may be reduced.

2.2.1 The purpose of the Special Periodical Survey is to ensure that each chain is capable of performing its intended purpose until the next Special Periodical Survey, assuming that

appropriate care and maintenance is performed on the mooring system during the intervening period.

2.2.2 The Special Periodical Survey should include:

??Close visual examination of all links of mooring chains, with cleaning as required ??Enhanced representative NDT sampling - 5% on general chains

- 20% on chain which has been in way of fairleads over last five (5) years - All connecting links ??Dimension checks, including length over five (5) links 2.2.3 Particular attention should be given to: ??Those lengths of chain (or wire rope) which have frequently been in contact with the windlass and fairleads during the unit's operation since the last survey. The Surveyor should ensure that these lengths are rated for use in the way of the windlass and fairlead. ??The looseness and pin securing arrangements of the joining-shackles. ??All windlass and fairlead chain pockets for: - Unusual wear or damage to pockets;

- Rate of wear on pockets, including relative rate of wear between links and pockets;

- Mis-match between links and pockets, and improper support of the links in the pockets. ??A functional test of the mooring system during anchor-handling operation for: - Smooth passage of chain links and/or wire rope and joining-shackles over the windlass and fairleads pockets;

- The absence of chain jumping or other irregularities.

2.2.4 The thickness (diameter) of approximately 1% of all chain links should be measured. The selected links should be approximately uniformly distributed through the working length of the chain. The above percentage may be increased/decreased if the visual examination indicates excessive/minimal deterioration.

2.2.5 All joining-shackles of the Kenter type and bolted type which have been in service for more than four (4) years should be dismantled and an MPI performed on all machined surfaces as per 8.2. No.38

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2.3 Special Continuous Surveys

In lieu of a special periodic survey, the Owner may opt for a Continuous Survey, by providing an extra mooring line which may be regularly inspected on shore and exchanged with lines installed on the unit on an annual or other appropriate schedule. 3. Anchor Inspection

The anchor head, flukes and shank should be examined for damage, including cracks or bending. The anchor shackle pin and crown pin should be examined and renewed if excessively worn or bent. Moveable flukes should be free to rotate between stops on the anchor head.

Bent flukes or shanks should be heated and jacked back in place according to an approved procedure, followed by Magnetic Particle Inspection. 4. Anchor Swivels

Although swivels are no longer in common use, anchors have been lost due to corrosion of the threads engaging the swivel nut. These threads should be carefully examined and, if significant corrosion is found, the swivel should be removed or replaced. 5. Chain Inspection Criteria 5.1 Chain Types Considered

This section applies only to \the following means: ??Mechanically locked adjacent to the link's (IACS R3 chain for example) flash-butt-weld and fillet welded on the other end ??Studs mechanically locked in place on both ends (IACS R4 chain for example) Other types of chain will require special consideration.

The service environment of offshore mooring chain is more severe than the service

environment for conventional ship anchoring chain. Offshore chain is exposed to service loads for a much longer period of time. The long term exposure to cyclical loadings in sea water magnifies the detrimental effect of geometric and metallurgical imperfections on fatigue life. Moreover the increased number of links in offshore chains renders the chain more susceptible to failure from a statistical standpoint.

Due to the effect of \for IACS R4 chain, have a lower ratio of fatigue strength to static tensile strength than typical lower strength steel such as used for IACS R3 chain.

5.2 Chain Link Diameter Loss due to Abrasion and Corrosion

Diameter measurements should be taken in the curved or bend region of the link and at any area with excessive wear or gouging. Particular attention should be given to the 'shoulder' areas which normally contact the windlass or fairlead pockets. No.38

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Links with minimum cross-sectional area less than 90% of the original nominal area should be rejected. If repair is permitted, it should be done by qualified personnel using an approved procedure.

Note: WELD REPAIR IS NOT PERMITTED ON IACS R4, R4S and R5 CHAIN (See paragraph 5.3.1)

A 5% reduction in diameter is equivalent to 10% of the reduction in cross-sectional area to original.

Two diameter measurements should be taken 90 degrees apart and the average compared with original diameter considering with allowable diminution. 5.3 Chain Stud Defects and Repair or Replacement

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