Comments from the report:
Both DPOs had several years’ experience but with a different DP control system where it is common to stop the vessel during a move by reducing speed to 0.0kts. However, on the system fitted to this vessel a retardation factor is used so speed is reduced automatically when the stop request is made.
Setting a speed at 0.0kt led to an unstable situation. The master instructed DPOs to keep a minimum speed on DP of 0.1kts and not set speed to 0.0kts
Considerations of the IMCA Marine DP Committee from the above event:
- Vessel specific familiarisation programmes and operation manuals should capture and make allowance for crew members not being familiar with systems. Each system/vessel has peculiarities which must be taught and learned by the crew onboard.
- The DP system manufacturer should be involved as it should not be possible for the operator to apply a valid setting which then causes an unstable DP system.
- It is recognised practice to slow down during a move, but it is not considered good practice to use zero speed.
- The use of the present position would maintain the vessel in the wanted position.