Comments from the report:
It was concluded that the loss of both DGNSS were due to huge superstructure of the installation interfering with satellite signals. This phenomenon is called reflection meaning DGNSS picks up reflected signals from the surroundings.
Considerations of the IMCA Marine DP Committee from the above event:
- The vessel was not being operated as a DP Equipment Class 2, as the requirement is at least three independent position reference systems should be installed and simultaneously available to the DP control system. Reference IMCA M 252 Guidance on Position Reference Systems and Sensors for DP Vessels.
- Loss of more than one DGNSS position reference system is a well-known issue due to external common cause failures, for example shielding of reference satellites and/or differential corrections.
- Operational planning and decision support tools, such as Activity Specific Operating Guidelines (ASOG), were clearly not in use or were inadequate. Reference IMCA M 220 Rev 1 provides Guidance on Operational Activity Planning.
- It appears that the DP Alert system was not used.
- It is mentioned in the report that at 08:09, master takes control of the vessel by the IJS. It is unclear from the report why the vessel then made contact with the installation. Reference IMCA M 117 The Training and experience of Key DP personnel.
- This event clearly demonstrates the benefit that can be gained from regular DP exercises and drills.
The following case studies and observations 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 DP technical crew in appropriately determining how to safely conduct their own operations. Any queries should be directed to IMCA at email@example.com. Members and non-members alike are welcome to contact IMCA if they have experienced DP events which can be shared anonymously with the DP industry.
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