200801 Lifeboat winch incident

Source MAIB – completed preliminary examination, 2007

The crew of a ship in port were conducting a lifeboat familiarisation drill. Having been lowered to just above the water, both lifeboats were in the process of being recovered when the electric motor of one lifeboat winch burnt out and stopped, leaving the lifeboat suspended a few metres below the davit heads.

The recovery of the lifeboat continued by hand, but the load during the luffing-in of the davits with the boat proved too strenuous. A decision was taken to temporarily exchange the motor with the other davit to complete the recovery. However, as soon as the defective motor was removed, the lifeboat unexpectedly released and lowered to the water at a controlled speed. No damage was sustained and the operational motor was then successfully transferred and used to recover the lifeboat.

Subsequent investigation revealed that when the damaged motor was removed, the pinion gearwheel shaft also withdrew from the housing. The crew had no appreciation that this shaft formed part of the geared connection between the roller ratchet freewheel assembly (which holds the load) and the winch drum. The removal of this shaft therefore disconnected the gearing and released the load to lower on the integral centrifugal brake. Although the risks associated with the removal of the pinion gearwheel shaft were not clearly described in the lifeboat davit system manual, there were references to precautions to be taken before working on the davit mechanism. No attempt was made to consult the manual before the damaged motor was removed.

Corrective actions
The davit manufacturer was made aware of the incident;
An alternative method for the emergency retrieval of lifeboats was provided;
Formal instruction issued regarding the securing of lifeboats before working on the winches and brakes
Notices posted at each lifeboat, on the planned maintenance system and in the maintenance manual, warning of the dangers of removing a winch motor when the lifeboat is not fully secured;
The sister vessel within the fleet made aware of the incident.

The MAIB also advised the vessel's operator to:
Review their company processes and procedures regarding the conduct of unplanned rectification work undertaken by ship's staff on lifesaving apparatus;
Ensure that an adequate risk assessment is in place covering the maintenance and repair of lifesaving systems by ship's staff;
Review the conduct and planning of lifeboat drills to ensure compliance with both statutory requirements and company procedures;
Review the condition and specification of other lifeboat winch motors to ensure that they would not contribute to further incidents.