Change of heading leads to DP incident
- DP Event
- Published on 25 February 2020
- Generated on 9 May 2025
- DPE 01/20
- 2 minute read
Incident
Further investigation revealed the overspeed settings were too tight and had to be increased in accordance with manufacturer’s recommendation.
Comments
The vessel had been on DP for the whole day and in order to lift the ROV on deck with the crane, vessel heading had to be changed 15 degrees away from the wind.
This caused a high load on two running bow thrusters and the third bow thruster was started, selected to DP and successfully shared the load. Increased windward force on the vessel due to high wind velocity acting on it as it changed heading, caused all the three bow thrusters to trip on overspeed with no DP or thrusters’ control system alarms.
Further investigation revealed the overspeed settings were too tight and had to be increased in accordance with manufacturer’s recommendation.
Considerations
- It is not clear why the additional bow thruster was not put online before the heading change.
- A simulated alteration of heading and or referring to the vessel’s capability plots should have been considered to ensure that the heading change could have been performed within vessel’s DP capability.
- The overspeed trip of all thrusters during DP operations shows inadequate initial commissioning and full power testing during the FMEA proving trials and annual DP trials and following any modification.
- This incident further highlights the importance of equipment protection settings with respect to DP redundancy concept, in addition to equipment safety. DP FMEAs require to consider the effects of equipment protection system on the wider DP redundancy concept.
- Reference: Guidance on Failure Modes & Effects Analysis (FMEA) (IMCA M166).
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The case studies and observations above have been compiled from information received by IMCA. All vessel, client, and operational data has been removed from the narrative to ensure anonymity. Case studies are not intended as guidance on the safe conduct of operations, but rather to assist vessel managers, DP operators, and technical crew.
IMCA makes every effort to ensure both the accuracy and reliability of the information, but it is not liable for any guidance and/or recommendation and/or statement herein contained.
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