Unreliable position reference systems leads to incident
- DP Event
- Published on 29 November 2019
- Generated on 9 May 2025
- DPE 04/19
- 1 minute read
Incident
The end-effect was that the deviation from the set point in surge and sway increased with each oscillation.
Comments
Only two DGNSS were online, with poor signal quality due to the location and environmental conditions. The end-effect was that the deviation from the set point in surge and sway were increasing for each oscillation.
Considerations
- For DP2 operations, the use of only two DGNSS systems is insufficient; a minimum of three systems are to be used based on two principles.
- The importance of monitoring the position reference systems (PRS) screen cannot be overstated; this then ensures that all the PRS agree on the position of the vessel.
- It is evident that the selected PRS were not providing reliable position information and highlights the problems that can be experienced when at least one reliable PRS is not available.
- It was noted that the move was paused at 2005; this should have provided the opportunity to investigate and correct the situation rather than continue with the move.
- It is also worth considering that the erratic movement of the vessel could indicate that the DP system needs retuning.
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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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