Typical Anchor Handling Operation - Step 8
In the following a typical anchor handling operation will be described step by sted. The procedure
described is just one out of many more or less different ways of retreiving an oil rig mooring
anchor from the seabed. The oil rig's equipment and / or construction may dictate a different
procedure, as may the anchor handling vessel, but the procedure described here is the one I have
participated in the most.
The supply vessel keeps heaving in the work wire whilst a little throttle ahead is maintained. This is to avoid the weight of the anchor chain pulling the vessel backwards. When the anchor reaches the same depth as the vessel's propellers the forward thrust is stopped so that the jet of water won't make the anchor spin and get entangled with the anchor chain. By now the oil rig will also start heaving in the anchor chain so the vessel will start moving slowly astern. This is a particularly dangerous part of the operation, since the low working deck is highly likely to get flooded when the vessel is moving astern! Depending on the water depth, the anchor chain might be dragging along the seabed while being winched in by the rig, or it might be hanging in a curve from the chain fairlead to the stern of the AHTS vessel.