In its latest Safety Digest, UK MAIB analyzed a fire onboard a crew transfer vessel, which was not extinguished because the fixed fire extinguishing system was activated before the engine space had been fully closed down and the fire-fighting medium quickly escaped through the natural air vent, losing effect. Although there were no injuries, UK MAIB highlighted that the correct safety actions were taken, but in the wrong order.
The incident
A crew transfer vessel was on passage from a windfarm to its base port. The vessel’s speed was 21kts and onboard were the skipper, a crewman and eight wind turbine technicians.
When the port engine oil temperature alarm sounded, the skipper brought the port engine to ‘idle’ and sent the crewman to investigate. The crewman found nothing untoward with the port engine and returned to the main cabin. By now, the oil temperature alarm had reset and so the skipper decided to resume passage on both engines.
Several minutes later, there was a loud bang from the port engine and the port engine space fire alarm activated. On the CCTV monitor by the control console, the skipper saw flames and smoke coming from the engine. He immediately stopped the starboard engine, alerted the passengers to the fire and told them to prepare for evacuation. He also stopped the port engine space’s ventilation fan.
Within 2 minutes of the port engine failure, the crewman had closed the flap on the engine space’s supply vent on the aft deck, and activated the fire extinguishing system. The extinguishing medium filled the port engine space, obscuring the flames from view on the CCTV, and a white gaseous cloud billowed from the port engine space’s natural air vent.
Meanwhile, the technicians mustered on the foredeck and the skipper broadcast a ‘Mayday’ via VHF radio. In response, other crew transfer vessels in the immediate vicinity closed to assist.
The technicians were soon transferred onto another vessel, but by then plumes of black smoke were coming from the port engine space’s natural air vent. As a result, the deckhand had to lean through the smoke to operate the port engine’s remote fuel shut-off. The skipper then sealed the port engine space’s natural and exhaust vents.
A hose was also rigged on the aft deck to provide boundary cooling if required. Minutes later, the CCTV showed that the smoke in the port engine space had cleared and flames were burning across the engine’s top. The fire was short-lived and within minutes had extinguished, partly due to the smothering effect of shutting the engine space vents but also because there was no more combustible material to burn.
Lessons learned
- The fixed fire extinguishing system did not extinguish the fire because the system was activated before the engine space had been fully closed down and the engine fuel supply isolated. Consequently, although the fire-fighting medium initially dampened the flames, it quickly escaped through the natural air vent and its effect was lost. The correct actions were taken, they were just taken in the wrong order – a crucial mistake that regular and comprehensive drills, the adherence to emergency check off cards, and clear signage could have helped avoid.
- Although engine alarms can be spurious, it is risky to assume that all is well if the reason for the alarm is not apparent. It is better to err on the side of safety and use the machinery affected only after the all clear has been given following a thorough technical investigation.
- The early broadcast of a ‘Mayday’ enabled the technicians to be evacuated quickly off the vessel, taking them away from danger and enabling the crew to focus on the fire and vessel safety.
