Unintentional deactivation of the DP system – DP incident

Comments from the report:

The initiating event was the unintentional activation of the DP standby button whilst in Automatic DP control. The radio used to call the installation control was situated over the DP control panel. In order to put the DP system in ‘Standby Mode’ it required the operator to Press the ‘Standby’ button twice. There were no alarms generated during the incident. After leaving the 500m zone attempts were made to re-enact the situation of the VHF radio handset pressing the button but this failed to put the system in standby. Follow Up – Information was sent to the DP system supplier including export files from the operator station. It was proven that the ‘Standby’ button was activated. The time difference between double taps was so small it was almost 1 single tap, this could explain activation by the VHF handset. To stop this from happening again, a clear flip top button cover will be fitted to both DP operator stations and a procedure initiated that the handset must be placed back in its cradle after each use.

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

• It is poor design that makes it necessary to lean over the DP control panel to use the VHF
• Vessel operators are reminded of the critical nature of DP mode selection buttons and should assess if the DP system is susceptible to unintentional deactivation of any critical mode
• If so, appropriate action should be taken without delay
• Recent action that the Committee is aware of is:
  • The fitting of a plastic flip cover to protect mode selection buttons
  • Installation of an additional function that requires the operator to confirm the mode change via a pop up window on the operator station
• A very short time period was allowed for DP stabilisation following the incident, the system had been switched to standby therefore time was required to build up the mathematical model.