An overstressed fall wire caused the fall of the fast rescue boat on board the UK registered car carrier, Tombarra, which then plummeted some 29m from its davit into the water below, killing one of the rescue boat’s four crew says the UK’s Maritime Accident Investigation Branch, MAIB. Among the causes was a non-working proximity switch and concern is raised about an overweight fast rescue boat.
The MAIB investigation has identified a number of factors that contributed to the accident, including:
• The proximity switch that failed to operate was not fitted in accordance with its manufacturer’s instructions, and was not suitable to be used as a ‘final stop’ device in man-lifting equipment.
• The functionality of the proximity switch was not tested immediately before the rescue boat’s recovery.
• Although the davit system manufacturer intended that the winch motor be stopped by its operator before the proximity switch was activated, the manufacturer’s guidance was misleading.
• The winch motor was able to easily and rapidly overstress the fall wire.
Although the International Maritime Organization recommends that all davit system designs are checked to ensure the compatibility of component parts, the Life Saving Appliance (LSA) Code accepts that overstressing of components could occur, but requires that this is prevented by the use of safety devices. However, the Code does not specify any standard to which such safety devices must conform or the number of safety devices that must be fitted to davit systems.
Part B of the MAIB report raises concerns regarding the overweight condition of the FRB, although it did not substantially contribute to the tragedy.
During the investigation, it was found that the rescue boat, a WHFRB 6.50, was significantly overweight. This did not contribute substantially to the failure of the fall wire on this occasion, but the boat’s in-service weight growth is a cause for concern and warranted detailed examination of the circumstances.
The weight growth found on Tombarra’s rescue boat had been caused by the ingress and retention of water in the hull’s internal stiffeners, which were hollow, and in segregated spaces containing buoyancy foam within the boat’s hull.
The water could not be drained from these spaces and the crew had no way of knowing the water was there. The foam used in the buoyancy chambers was of varying quality and contained voids in which water was able to collect. Inspection and testing of other WHFRB 6.50 rescue boats, along with reports of inspections of other rescue boat models, indicates that there is considerable scope for many rescue boats and lifeboats to be overweight due to water retention.
During this investigation, it was apparent that the problem of water ingress and retention in rescue boats and lifeboats using buoyancy foam is known by many of the interested parties within the shipping industry.
There is general recognition that boats will not remain watertight and their weight will increase over time as the accumulated water cannot be drained. An increase in weight can not only adversely affect a rescue boat’s ability to meet international requirements, but it can also compromise the safety of its launching and recovery equipment.
Recommendations have been made in part A of the two-part report to the Maritime and Coastguard Agency and the International Life-saving Appliance Manufacturers Association aimed at improving the safe operation of davit systems through improved design and construction. Recommendations have also been made to the davit system manufacturer to take action to ensure that both its currently supplied SA1.5/1.75 davits with W50RS winch/15/20kW electric motor combinations, and its future davit systems are safe to operate.
Part B of the report includes recommendations to the Maritime and Coastguard Agency aimed at ensuring rescue boats and lifeboats are designed so that water can be drained from all hull spaces and that the weights of rescue boats and lifeboats are periodically checked. A recommendation has also been made to the International Life-saving Appliance Manufacturers’ Association aimed at ensuring the safety of boats already in service and improving future designs.