Accident: HMPE Rope Properties Not Assessed
The U.K. Marine Accident Investigation Branch has released its report on the investigation of the failure of a mooring line on board the LNG carrier Zarga which resulted in serious injury to a deck officer.
A deck officer suffered severe head injuries when he was struck by a parted high modulus polyethylene fiber (HMPE) mooring rope during a berthing operation at South Hook LNG terminal, Milford Haven on May 2, 2015.
The area where the officer was standing was clearly within the snap back zone of the rope but had previously been designated as a safe area.
The perception on board was that HMPE ropes did not recoil on failure, and the elasticity introduced by the rope’s tail had not been properly assessed.
The investigators concluded that the vessel’s mooring lines were not fit for purpose: they did not have the minimum breaking strength specified at build, they were not compatible with the vessels mooring deck fittings, and the required working load limit was too high.
The predominant failure mode, axial compression fatigue, had not previously been associated with HMPE rope failures.
The rope’s tightly bound jacketed construction increased the likelihood of axial compression fatigue and prevented the crew from inspecting its load bearing core and identifying key discard criteria.
Guidance provided by the rope manufacturers and shipping industry bodies for the selection and use of high modulus synthetic fiber mooring lines was limited and often contradictory.
Command weaknesses were identified prior to and during the mooring operation. Had tugs been recalled to assist in the re-positioning of the vessel the accident might have been avoided. The officer in charge of the forward mooring party got directly involved in a specific task and lost his overall view of the mooring operation.
Recommendations have been made to Shell International Trading and Shipping Company, the Oil Companies International Marine Forum, Bridon International (the rope manufacturer) and Eurocord aimed at improving the levels of knowledge among shipowners, managers, builders and crew regarding the complex properties of high modulus synthetic fiber ropes.
The report is available here.