It was discovered that the 230v supply breaker was open and the uninterruptible power supply (UPS) 2 batteries completely discharged. Warning alarms generated by the DP system regarding the condition of UPS 2 were overlooked. An additional checklist item was added to the field arrival trials to check UPS 1, 2 and 3 are clear of alarms and operating as normal. Vessel maintained position throughout.
Considerations from the above event:
- The lessons to be learnt from the above are obvious and barriers preventing such errors are essential;
- Alarms presented to operators must be acknowledged and acted on.