Human Factor Caused a DP Undesired Event

Comments from the report:

The report detailed that there was a “bug” in DP-A station. To resolve the issue DP-A and B as well as MTC stations were stopped at the same time, so to avoid the restarting station copying corrupted information from an online controller affected by the bug. The report highlighted that there had been no regular software updates executed and the equipment was getting older with more frequent reboots while in operation.

Considerations of the IMCA Marine DP Committee from the above event:

This event highlights the need to ensure a robust management of change process around software and software updates. The event report did not highlight the use of activity specific operating guidelines nor any change to DP status during the incident. Although not detailed in the report, the DP committee questioned the use of manual thruster control instead of Independent Joystick mode which may have aided station keeping during investigation works. Although not related to the event the number of references seems inadequate. IMO MSC Circ 645 and IMO MSC.1 Circ 1580 guidance documents state that for DP 2  or 3 operations:

• There is a requirement for 3 sensors serving the same principles when the vessel is fully dependant on these signals (eg, 3 gyros)
• There is a requirement for 3 independent position references simultaneously available during operation based on two different principles.

Again, although not related to the event, the report notes that the vessel operates “closed bus”. Reference can be made to IMCA M 166  Guidance on Failure Modes & Effects Analyses (FMEAs) for failure considerations related to closed bus operations.