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Auxiliary Boiler Back Fire on Ships – Case Study

Boiler Back Fire Incident on Ships

Vessel was at anchorage awaiting berthing instructions.

18:00hrs – Fire in engine room reported to the bridge.
18:01hrs – Alarm sounded and announcement made on vessel PA system.
18:03hrs – All mustered at fire station and all are accounted for, several explosion’s were being heard coming from the engine room.
18:04hrs – Emergency stop for engine room operated, Quick closing valves operated & commenced boundary cooling.
18:05hrs ~ 1820hrs – Fire fighting team unable to enter engine room due to heavy smoke and continuous sound explosion.
18:30hrs – Explosion sound stopped, fire fighting team enter the engine room and fire extinguished using portable dry chemical extinguisher.
18:45hrs – Fire extinguished and confirmed no chance of re-ignition.
18:50hrs – Started cleaning the effected area and surrounding and assessing damage.

There have flashback incidents on board ships fitted with composite boiler in the past.
The manufacturers have issued a safety bulletin for this type of boiler which was not known to the office or Ship Staff.
As per the manufacturer’s recommendation, the burner can be changed to avoid a boiler back fire but this was not know to either the office/ship staff.

The un-burnt fuel accumulated in the hot furnace lead to generation of a rich combustible mixture of air and fuel which was not completely purged during the pre-purge cycle prior to next start sequence. This caused boiler back fire in the furnace during re-igniting of the burner.
Although the exact cause of accumulation of un-burnt fuel in furnace has not been determined it is suspected that leaky fuel oil solenoid valve which lead to dripping of fuel oil in furnace after auto cut-off of boiler.
The boiler fuel oil solenoid valve had been opened up a number of times in the past as it was found leaking and was being overhauled by lapping the v/v disc and seat as no spare was available. The vessel did not inform the office on the condition of the valve.

Safety bulletin issued for that type burner is included in the report.
For vessels fitted with the this type burner the Safety bulletin should be posted in the ECR and should be part of the engine room familiarization.
The makers have recommended modification to the burner which will be done on this burner.
Ch-Engineers of these vessels should include in their hand over notes the problem associated with this type of burner and refer to the safety bulletin.
Check through “peep hole” if ignition electrodes are giving spark for pilot burner and pilot burner is igniting and giving stable flame.
Check the funnel smoke which must be “dull black”. Black or white smoke indicates improper combustion of fuel with un-burnt fuel accumulating in the furnace.
Prior inspection of boiler burner or attempting to re-ignite the boiler burner after a flame failure alarm:
Change boiler control to manual, run the purge cycle for at least 5 minutes ensuring the blower damper is fully “open” position to ensure combustible gases purged out of furnace.
Check through peep hole for any hot spots near the burner area or furnace floor during purging.
Check funnel, must be clear of any smoke.
After above operation satisfactorily done, the maintenance on boiler can be carried out. Maker’s maintenance procedures during overhauling / repairing are to be adhered to at all times.

Duty engineer to check the burner flame (through peep hole) and the funnel smoke regularly during watch keeping and ensure proper combustion of fuel in furnace.
Regular maintenance of boiler fuel oil system components to be carried out as per maker’s instructions and at a specified interval or earlier if required.
Fuel oil system solenoid valves to be checked at regular intervals for positive shut off and must to be replaced if found leaking.
Do not attempt try to re-ignite the boiler burner without eliminating the cause of ignition failure.