ROV main lift failure

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)