A termination failed during launch of an ROV for a test dive, and the ROV/TMS assembly fell to the seabed. No-one was harmed. The umbilical termination slipped through the wirelock socketing.
It was noted that the umbilical termination had been done only a few days beforehand and been load tested to 1.5 x the weight of the ROV/TMS assembly.
What was the cause?
Third-party investigation concluded that the four main causes of the failure were:
- The volume of the bullet/cone was too small giving too narrow a passage for the wirelock to flow and fill the bullet;
- Uneven distribution of strains, with the majority close to the outside perimeter of the cone;
- Too high force applied during docking;
- Excessive resin in the broad end of the cone changed the intended shape of it, thereby decreasing the cone’s function.
Corrective action/lessons learned:
- The root cause was suboptimal cleaning and strand distribution within too small a cone, which was difficult to work with. The cone was changed to a bigger one;
- Adjustment of docking head dampers.
Members may wish to refer to:
- Main ROV lift wire umbilical and bullet parted
- Umbilical termination failure and loss of ROV
- Loss of ROV after umbilical termination failure and damage to ROV during recovery
- Guidance for the safe and efficient operation of remotely operated vehicles (IMCA R 004)
- The initial and periodic examination, testing and certification of ROV launch and recovery systems (IMCA LR 011, IMCA R 011)
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