Consequences of not following ASOG

An SOV was approaching a Platform for personnel transfer via use of onboard Personnel Access Platform (PAP) and the platform’s gangway. When the distance was approximately one metre between the gangway and the PAP, there was a sudden rejection of the vessel’s starboard azimuth thruster by the vessel’s DP system without any warning. The ‘ready’ signal was lost to DP Control for the starboard Azimuth thruster. The vessel started to drift astern.

After a few seconds, the starboard azimuth thruster readiness indicator on the Vessel’s DP Console showed ‘ready’. The DPO on duty immediately re-selected the thruster back into operation. After the re-selection of the previously failed thruster, the vessel continued to drift astern with the stern starting to rotate slowly to starboard. As the PAP was very near to the gangway, it made contact with the gangway and incurred damage. During the drift, the gangway also snagged against the ship’s structure at the ship’s stern.

The DPO immediately tried to move the vessel away using the DP joystick but found response was slow. The Master, who was at the manual thruster console at that time, immediately instructed the OOW to switch the vessel to manual control.  He then took over command using manual control and manoeuvred the vessel away to avoid further collision with the platform. During the manoeuvre, the gangway which was snagged with vessel’s stern structure was dragged. It subsequently came dethatched from its securing point on the platform and finally remained suspended off the platform by its rigging.

There was no injury to personnel reported.

While the vessel was manoeuvring into position to prepare for passenger transfer, the DP system reported an intermittent failure of one of two aft azimuth thrusters causing the starboard thruster to be incapacitated and de-select from DP Control, however the DP system still showed the thruster as ready, the operator re-selected the thruster back into DP Control.

The vessels DP system calculation was distorted by the inclusion of an unresponsive thruster and therefore could not stabilise.

The vessel could not hold position with the remaining Bow and Port azimuth thrusters.