SAFETY FLASH: UMBILICAL FAILURE DURING ROV RECOVERY

Incident Overview

During recovery of a remotely operated vehicle (ROV) following an inspection dive, the unit was nested in the Launch and Recovery System (LARS) cursor, lifted clear of the surface, and moved along the vessel’s cursor rails towards the transition point. At this stage, the operator stopped the umbilical winch and cursor-assist tuggers in order to switch the winch into low-tension mode.

As the ROV reached the cursor rail transition point, the umbilical parted and the ROV dropped to the seabed. The vehicle was subsequently located by means of its transponder and recovered. No personnel were injured, and no damage occurred to seabed assets.

Positive Outcomes

• The vessel’s crew responded quickly, locating and recovering the ROV without incident.
• No injuries occurred, and no seabed infrastructure was damaged.
• The recovery operation was completed safely and without escalation.

Issues Identified

• Latent defects were present within the umbilical termination, which had not been detected during earlier inspection or testing.
• The cursor rail transition point proved to be a location of elevated load during the recovery operation.
• Pausing the winch and tugger operations resulted in a brief period when the termination remained under load.

Root Cause

The investigation determined that the failure originated from an improperly constructed umbilical termination. The resin case was defective, and the armoured strands were not correctly centred or evenly distributed within the termination during manufacture. Although the termination had previously passed a pull test, these internal defects ultimately caused it to fail at the transition point.

Key Takeaways and Actions

• Establish a formal inspection and verification process for umbilical terminations, including checks on resin integrity and armoured strand separation.
• Provide dedicated training for personnel responsible for inspecting and re-terminating umbilicals.
• Incorporate umbilical termination checks into pre-job and planned maintenance routines to confirm connection integrity prior to deployment.
• Reinforce careful monitoring during ROV recovery—particularly at transition points where loading conditions can vary.

Note: The original version of this Safety Flash is available from the IMCA website.