The UK’s Marine Accident Investigation Branch (MAIB) has published the findings of its investigation into a mooring line failure on board the Q-max LNG carrier Zarga that left a deck officer with serious head injuries.
The incident took place at Milford Haven in March 2015 as crew attempted to berth the 266,000m³, 2009-built Zarga. The desk officer was hurt when an ultra-high modulus polyethylene (UHMPE) mooring line parted.
MAIB concludes that the rope failed “due to the effects of axial compression fatigue that… significantly reduced the yarn strength and therefore rope residual strength”. Human error contributed too, however.
“Factors that often contribute to mooring-deck accidents are lack of communication and control, insufficient training and experience and the person in charge becoming directly involved with a particular aspect of the operation,” the report found. “All of these factors were evident in this case.”
The report notes 45 mooring-line failures in 2009-2015 involving STASCo-managed Q-max and Q-flex LNG carriers, “the vast majority” involving Bridon’s Steelite Superline Extra rope.
Bridon has stopped manufacturing and selling the three-strand ropes.
MAIB’s report sets out a series of recommendations, to mooring line manufacturer Bridon International, to shipmanager Shell International Trading & Shipping Co (STASCo) and to members of the Oil Companies International Marine Forum:
Bridon International should review and enhance guidance and instructions for monitoring, maintenance and discard of high-modulus synthetic fibre (HMSF) mooring ropes and bring this to customers’ attention. It should also conduct whole rope break tests, to establish accurate realisation factors for its HMSF ropes.
STASCo should review the mooring arrangements on board its vessels, ensuring that the mooring lines and deck fittings are compatible. It should develop robust mooring-line procurement criteria, provide its ships’ crews with comprehensive guidance on inspecting these types of mooring ropes. It should also investigate methods for monitoring HMSF rope mooring lines’ through-life condition.
OCIMF members should consider the report’s findings as they revise their mooring-equipment guidelines. Priorities include preventing injuries to crew from mooring rope snapback, the factors that lead HMSF ropes to lose strength, adopting safe ratios for all deck fittings that use these types of rope and through-life monitoring of these mooring ropes’ operating conditions and maintenance.
LNG World Shipping reported last year on the results of research that MAIB published in Safety Bulletin 1/2015: Urgent safety lessons on the elongation and snapback characteristics of mooring lines.
Read the full MAIB Accident Report