...resulting vessel drifting

Incident Date:

17/06/2002

Summary:

Financial impact

Incident consequences (potential or actual):

No details available.

Cause of accident or incident:

No details available.

Activity Location:

Support vessel eg Supply, Standby

Activity Type:

Modification of plant/structures

Description:

At the time of the incident, the vessel was working on DP alongside the East face of the platform with the port side presented to the jacket and with 25 to 30 ks. of wind on the stern. The diving bell was positioned at -129m. A three men bell run was in progress and working divers had entered the jacket for the purpose of installing a bell mouth assembly on a modified conductor. The divers were working in the zone between -120 m and -140m (bottom). Both azimuth thrusters stopped at 10.07 Hrs eliminating the vessel's station keeping capability and causing the vessel to drift to the NW (ahead). Heading control continued to be available by virtue of the bowthrusters. Azimuth thruster No. 1 re-started within one minutes but stopped once again apparently as a direct result of the re-starting of No. 2 which also shut down immediately. This cycle of re-starting and subsequent failure of Nos. 1 & 2 azimuth thrusters re-occurred a second time before No. 1 was finally restarted with No. 2 initiated. The vessel position then stabilised to 40m from the original working location. An emergency diver recovery was initiated immediately following the first failure, and both divers had returned to the clump weight by the time seven minutes had elapsed. The bell was recovered to deck with all divers well. Finally, the vessel recovered both bell clump weight and departed from the platform 500m zone.

Specific Equipment:

Azimuth thrusters

Lessons Learnt:

No details available.

Task Description:

No details available.

Recommendations:

Reconfigure the IMAC 33 cards to bring about a suitable segregation of critical consumers (thrusters and transformers) to remove the single card failure mode affecting systems on both sides of the switchboard. Carry out suitable briefings of all personnel on the vessel to ensure that an understanding of the incident and the corrective actions are fully disseminated.Carry out a review of other vessels, vessel management systems (power management/Integrated Control Systems) to ensure that similar failure mechanisms are not present.

Contact Details:

No details available.

Figures:

No figures available.

Usage details:

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