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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:

Safety Event

Published: 9 December 2021
Download: IMCA SF 34/21

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