As part of its latest Safety Flashes, IMCA released an incident where a termination failed during launch of an ROV for a test dive.
The case
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.
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.