A member has reported an incident in which an ROV main lift umbilical parted causing the ROV to drop to the seabed (1360m water depth). The incident occurred while recovering a ROV to deck. With the use of the vessel crane and the assistance of a second ROV, the fallen ROV was recovered to deck and inspected; there was no damage. There were no injuries.
Our member’s investigation noted the following:
- The main lift umbilical had recently undergone third-party destructive testing and load testing and had been certified as fit for purpose;
- The scheduled maintenance and inspection was found to be in accordance with the manufacturer’s original requirements;
- An umbilical lubrication system was in place and operational;
- The current lubrication system had been installed a year earlier as a systems upgrade to the originally fitted system;
- At the time of the incident, the vessel was located in a safe recovery zone away from subsea assets;
- During inspection, internal strands of the main lift umbilical were found to have damage consistent with previous water ingress (rust), and there was no evidence of lubricant present in the inner core.
Our member determined that the cause of the failure was internal (hidden) damage of the main umbilical, following from lack of lubricant penetration.
The following lessons were learnt:
- All rope parts should be thoroughly examined and tested to determine if wire damage has occurred in locations that are not visually accessible;
- Conducting ROV launch and recovery operations clear of subsea assets was a mitigation; this prevented further equipment damage that could potentially have occurred.
Recommendations and corrective action:
- Ensure that close visual inspections are carried out on each strand of all layers of the umbilical during the annual cut back and re-termination;
- Ensure the condition of the strands was reported on the umbilical destruction test report (Umbilical destruction test procedures now reflect this);
- Recommend further research into the use of UT scanning and cleaning equipment on ROV umbilicals after 10 years of service.
Members may wish to refer to the following similar incidents (key words: umbilical failure):
IMCA Safety Flashes summarise key safety matters and incidents, allowing lessons to be more easily learnt for the benefit of all. The effectiveness of the IMCA Safety Flash system depends on Members sharing information and so avoiding repeat incidents. Please consider adding [email protected] to your internal distribution list for safety alerts or manually submitting information on incidents you consider may be relevant. All information is anonymised or sanitised, as appropriate.
IMCA’s store terms and conditions (https://www.imca-int.com/legal-notices/terms/) apply to all downloads from IMCA’s website, including this document.
IMCA makes every effort to ensure the accuracy and reliability of the data contained in the documents it publishes, but IMCA shall not be liable for any guidance and/or recommendation and/or statement herein contained. The information contained in this document does not fulfil or replace any individual’s or Member's legal, regulatory or other duties or obligations in respect of their operations. Individuals and Members remain solely responsible for the safe, lawful and proper conduct of their operations.