Bolt Failure Leads to Fire in Engine Room On Board Merchant Vessel in Transit

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What Happened

During routine rounds, a fuel oil leak was observed in one of the main engine unit fuel distributors. A failed attempt was made to arrest the leak by tightening the bolt, following which a pipe was used to provide more torque to tighten a bolt on the distributor. The leak was arrested and the engine room unmanned.

However, after about half an hour, there was fire alarm in the engine room and low pressure on Main Engine cylinder unit no.2. On attending the alarm, the engineers observed fire and smoke coming out of unit no.2. Before anyone could stop the main engine the vessel had a blackout.

A fire alarm was raised on the vessel following which all crew proceeded to muster station and designated fire parties proceeded to fight the fire in engine room. The intensity of the fire was too big to be fought manually and the CO2 system had to be deployed. Meanwhile the company and coastal authorities were informed about the fire in engine room.

After deploying the CO2, there was a significant reduction in smoke. Checks were performed by the fire party for any hot spots and signs of fire or potential sources of combustion or reignition.

Analysis and Investigation

Upon investigation, a broken bolt from the fuel distributor housing of Maine Engine cylinder unit no.2, was discovered. This was believed to be the probable cause of the fire. Spraying of hot high pressure oil, on heated surfaces of the main engine unit, caused ignition and hence the fire.

There was significant heat and smoke damage to the main engine due to which the exact location of the leak could not be determined. The spray of fuel oil from the fuel distributor housing, in turn suggested a leak in the choking tube(s) of the fuel distributor for cylinder unit no. 2 and/or the feed pump’s connection to the fuel distributor housing. The bolt could have broken due to over tightening causing the oil spray or the failure of choking tubes could also have played a significant role in the fire.

Lessons Learnt

  • Any high pressure bolts/ nuts have a maker recommended tightening torque. Over tightening or under tightening of high pressure connections, bolts or nuts is a hazard to the safety and safe operations of the ship, posing risks to the crew as well as the ship.
  • In addition to the correct tightening torque, the correct bolts or nuts must be used for the high pressure parts and parts exposed to high temperatures.
  • In this case a spanner and pipe were used to tighten the bolt without any visual indication of the torque. Use of improper tools can be detrimental hence the crew must be sufficiently trained and informed to use the correct tools specified for a particular job.
  • In case of any leaks, an immediate corrective action must be taken and the leak must be
    monitored at regular intervals.
  • Age of equipment and parts under various thermal and mechanical stresses can play a major role in failure of equipment and hence condition monitoring of equipment is crucial for safety onboard vessels.
  • In case of any leaks on the main engine high pressure fuel lines, the engine must be stopped if necessary, to carry out repairs. Careful assessment and forward thinking is essential for the crew and officers onboard to avoid any accidents.

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Source: MSIU

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