Читать книгу Underwater Inspection and Repair for Offshore Structures - Gerhard Ersdal - Страница 37

A set of guidance for surveys of the moorings of floating units has been produced by IACS (2010). It states the minimal requirements for an annual survey, the scope of which are mooring components adjacent to the winch or windlass. It should be conducted with the vessel at operational draft with the position mooring system in use. This is to be supplemented by a more extensive survey if typical damage is present such as:

 chain: reduction in diameter exceeding 4%, missing studs, loose studs in grade 4 chain;

 wire rope: obvious flattening or reduction in area, worn cable lifters causing damage to the rope, severe wear or corrosion, broken wires.

Special periodical surveys are also required at approximately 5‐year intervals. These special surveys are quite demanding and should include the following:

 close visual examination of all chain links, with cleaning if required;

 enhanced NDE sampling of:5% of the chain20% of chain which has been in the proximity of fairleads in the last 5 yearsall connecting links

 dimensional checks, including lengths over five links;

 checking looseness and pin‐securing arrangements of joining shackles;

 measurement of thickness (diameter) of approximately 1% of all chain links distributed through the working length of the chain; and

 dismantling and MPI of all Kenter‐type shackles which have been in service for more than 4 years.