Summary
On 12 September 2017, while approaching Yarmouth, Isle of Wight, the ro-ro passenger ferry Wight Sky suffered a catastrophic failure of one of its main propulsion engines, followed by a fire. The fire was brought under control in less than 2 minutes, but the vessel’s engineer, who had been standing near the engine, suffered serious burn injuries to his hands and face. Although he was discharged from hospital 7 days later, he was subsequently diagnosed with posttraumatic stress disorder.
An examination conducted by the vessel’s engine maker, Volvo Penta UK, concluded that the most probable trigger for the failure was debris in the engine’s oil channels following rebuild.
Findings
- The engine had been completely rebuilt and failed after 5½ hours of operation.
- The vessel’s soft patches had not been removed, necessitating the engine to be lowered piecemeal into the engine room.
- Debris could have entered the engine’s oil channels during the 3 days that the partially assembled engine had been exposed to the elements.
- Analysis of oil samples from the engine indicated that accelerated wear had commenced before the engine failure.
- The power supply to the essential services switchboard, which distributed power to critical equipment including the fixed fire-extinguishing system, was lost 27 minutes after the accident.
Conclusions
- The consequences of this accident could have been far worse; the engineer was fortunate that his injuries were not life threatening, and the quick actions of the bridge team ensured the safety of the vessel, passengers and crew.
- Volvo Penta’s investigation into the engine failure concluded that:
- Debris in the engine’s oil channels was most probably responsible for initiating the failure.
- When the shells of main bearing 5 turned, the lubrication supply to big end bearing 4 was blocked, resulting in destructive failure.
- Rebuilding the engine in a clean and controlled environment and transferring it complete into the engine room would have reduced the likelihood of debris ingress
- The engine was not fitted with a wear detector, so there was no means of receiving a warning before the engine failed.
- The essential services switchboard aft circuit breaker had been left in manual mode, resulting in the loss of power to critical equipment, including the fixed fire-fighting system.
Action Taken
Wightlink Limited has:
- Agreed with RKM that all engines will be fully assembled and load-tested prior to delivery on board.
- Put in place signage to ensure that the circuit breakers for the essential services switchboard are correctly set at all times.
Volvo Penta UK has:
Written to all Volvo Penta dealerships in the UK and Ireland to provide guidance on good practice for repair and rebuild and to ensure that:
- Volvo Penta UK is informed of any major engine failure resulting in injury, fire or flood.
- Where appropriate, soft patches are removed to allow removal and reinstallation of complete engines.
- Engine assembly is completed in a clean environment to prevent debris being built into an engine.
- Following rebuilds, engines are load-tested on a dynamometer and certificates issued confirming the required performance.
- Records of component measurements are kept to confirm that they are within tolerance and fit for reuse.
Recommendations
- Consider offering wear particle detection technology for Volvo Penta marine engines that cannot be easily serviced on board.
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Source: MAIB
