The UK MAIB Safety Digest in one of its cases includes lessons learned regarding a fire incident in the engine room of a cargo ship.
The incident:
A cargo ship was proceeding on passage in a controlled traffic lane when the duty engineer noted that one of the main engine clutches was overheating and generating copious amounts of smoke. He contacted the bridge and requested an immediate shutdown of the affected engine. The engine was shut down, the fire alarm sounded and the ship’s crew mustered at their emergency stations. As there was a significant amount of smoke coming from the engine room, a fire-fighting team wearing BA was organised to investigate.
While the BA team was investigating, the master prepared to deploy the anchor. The BA team reported back that the clutch area was extremely hot, with electrical control wires melting, producing sparks and thick smoke. Local cooling was attempted. However, this proved ineffective, and a decision was taken to close down the engine room and to use the CO2 fixed fire-extinguishing system.
The ship was immediately anchored and the starboard engine, which had not been affected, was stopped. Following operation of the CO2 system, the boundary temperatures were monitored. After a number of hours, the engine room was vented of smoke and residual CO2. The atmosphere within the space was then tested. Following confirmation that it was safe to enter, an inspection of the engine room and area around the clutch revealed that the cables were no longer sparking and that the heat had dissipated. The engine room fans were started, the generators run up and electrical power restored. The starboard engine was then started, and the vessel commenced weighing anchor. However, before the anchor had been fully recovered, the chief engineer reported electrical short-circuiting from the clutch controls, and smoke emanating from the cables. The engine room was again shut down and monitored until it had sufficiently cooled and was clear of smoke. A request for assistance was made and the ship was later towed to a safe haven for repairs to be carried out.
Findings:
A technical inspection of the port engine clutch found that an oil seal on the hydraulic clutch control unit had failed. This had allowed hydraulic oil to pass into the clutch housing, resulting in excessive pressure developing within the housing. The clutch housing relief valve had then operated, which reduced the over-pressure but allowed oil to spray onto the hot clutch casing. The atomised oil ignited on contact with the clutch casing. A fire then developed around the area of the clutch. This melted the insulating material on the electrical control cabling, resulting in thick smoke and electrical short-circuits within the clutch control system. It was noted that the clutch high temperature alarm had not activated before or during the fire.
Lessons Learned
1. Planned maintenance systems need to be reviewed to ensure that they continue to provide appropriate maintenance solutions. Maintenance activities should include an assessment of component condition, and maintenance intervals should be adjusted accordingly.
2. In this case, the correct operation of one safety device and the malfunction of another combined to turn a component failure into a hazardous situation:
• The pressure relief valve worked correctly by preventing a dangerous over-pressurisation of the clutch housing. However, the resultant oil spray led to a fire. Designers, installers and operators have a responsibility to ensure that safety devices are fit for purpose and that their emergency operation does not lead to a hazardous situation.
• The high temperature alarm, which should have given warning of a fault when the clutch mechanism temperature increased due to the pressure rise, failed to function. Critical alarms should be tested on a regular basis, alarm test results recorded and any defects rectified.
3. Following the initial fire, electrical power was restored before sufficient remedial work had been completed on the damaged cabling. A thorough post-fire risk assessment should have been carried out to identify potential hazards (collateral damage to equipment and systems) and deficiencies in emergency systems. The fire detection system might have been damaged and the fixed fire-extinguishing system was no longer available as it had been operated during the initial fire incident. If a sufficient risk assessment had been carried out, it is likely that the identified hazards would have highlighted the need for external assistance at an earlier stage.
Source: UK MAIB
