Seabed survey

Tide and current movement around the base of a structure or pipeline may produce shifting of the seabed levels. Scour may leave portions of a structure (particularly leg bases) or a pipeline unsupported, resulting in movement, rocking, displacement, or even rupture of the structure or pipeline. Scour prevention devices, such as artificial seaweed mats, can effectively prevent or control scouring problems, but regular seabed inspections are still required to check their continued effectiveness.

Debris survey

Debris means any material that should not be there, such as lost fishing nets, anchor cables, wire ropes, girders and scrap material dropped over the side from offshore platforms and vessels.

Debris is a serious problem, not only because it may create a hazard to divers, submersibles and ROVs, but also because it can interfere with corrosion protection systems and may cause fretting, wear and resultant accelerated corrosion.
For these reasons, debris surveys, to locate and record the positions of all debris so that it may later be removed efficiently and safely, are essential.
Every offshore structure has a limit to the amount of weight and wave loading that it can safely endure.

Marine growth survey

Marine-growth can jeopardise the safety of a structure by increasing not only the weight of the structure itself, but also its surface area, which means that the impact of waves and currents is increased. If marine-growth becomes excessive, important equipment may have to be removed from the deck, or the structure may become unsafe. Regular surveys are needed to help determine when the removal of marine-growth will be necessary.
Such surveys need to measure the thickness of the growth, the amount of the structure that is affected, and whether the growth is 'soft' or 'hard', as each type has different significance due to different weights per volume.

On another hand, more and more countries' requirements are a "clean hull" (e.g. New Zealand) and if a vessel has too much biofouling they may restrict entry, reduce its itinerary, ask you to clean your vessel offshore using an approved treatment or within 24 hours by an approved provider. Such measures being at the expenses of the vessel owner or operator.

You may be interested to know about: our video and still-photography equipment

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