Pressurised Fuel Oil Leak Causes Fire in Ship Engine

Summary:

On 27 April 2016, at about 13:30, the staff chief engineer heard one of the crew members shouting in the engine-room. He made his way to the workshop in order to investigate what had happened. At the other entrance to the workshop, the staff chief engineer was informed that there was a fire on one of the diesel generators.

The staff chef engineer hurried towards the diesel generator room and from the inside, he observed a dark orange fire under the turbocharger of diesel generator no. 2, on the B-bank side. The fire was brought under control within a few minutes, limiting the damage to the immediate surroundings of the turbocharger.

Cause of the Fire

The immediate cause of the fire was found to be a pressurised fuel oil leak on the fuel oil supply line to the high pressure fuel oil pumps. The fuel oil leak was in way of a connecting flange on the A-bank side of the A-B set pipe. The top left Allen bolt was found completely loose and had actually fallen out of place. The remaining three Allen bolts were also loose.

Missing Allen screw

The MSIU did not have access to the Allen bolts and therefore, a metallurgical analysis was not carried to determine whether there was any damage to the threads. It has to be pointed out, however, that the safety investigation ruled out any potential problems (say, damaged thread) with the missing Allen bolt, given that the three other bolts were also found loose. Engine-room records collected during the course of the safety investigation indicated that the last maintenance on the pipe was carried out on 21 April 2016.

AMOS history report (screen dump)

The task was actually ‘breakdown’ maintenance after the engineers noticed a broken pipe bracket and a loose bolt on the bracket. The absence of damages to the thread of the Allen bolt may be suggestive that there were no anomalous operations of the pump, which could have caused the loosening of the bolts. While the safety investigation noted that the maintenance history in above Figure showed that the bolts had been tightened to the torque recommended by the manufacturer (23 Nm)3 , it was not excluded that actually a lower torque may have been applied, thus allowing for vibration to loosen the bolts.

Protection covers in way of the fuel oil lines

Taking into consideration that the prime mover had only been working for a total of 39 hours from the time it was maintained until the fire, it was considered possible that actually vibration was a major contributing factor to the loosening of the four Allen bolts, fitted in somewhat awkward positions.

Conclusions

Blue buttons below the ultra fog system

1. It was not excluded that actually a lower tightening torque had been applied when the system was last maintained, thus allowing for vibration to loosen the bolts after a relatively short period of running time;
2. Vibration was a major contributing factor to the loosening of the four Allen bolts;
3. Despite the protection covers, a closer inspection revealed that fuel oil had sprayed at a pressure of 8 bar underneath the protective cover, penetrated through the gaps in the exhaust lagging screen, reached the exhaust pipe and auto ignited;
4. The gaps in the protective screen had never been detected during the regular maintenance on the DG because of the narrow and small spaces involved;
5. The ultra fog system had been operated successfully;
6. The staff chief engineer took the necessary and timely actions by activating the ultra fog system and shutting down the fuel oil supply to the affected prime mover.

Action Taken

Splash tape fitted after the fire

Although the covers had been installed as per maker’s design, the Company fitted SOLAS splash tape on the affected flange and pipe as an added protection barrier system.

Moreover, the Company replaced the (blue) release buttons on the water mist system with red call buttons to avoid any confusion. The Company has also addressed this issue through its crew familiarisation procedure.

New call points in red casings

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Source: Transport Malta

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