uptake fires in a boiler on board or ships

Soot and unburnt carbon can deposit on the walls of the boiler uptake

(chimney). They form, in effect, another fuel and can catch fire in

the uptake. Although uptake fires do not often occur, they can be

very difficult to extinguish and the hazard builds up quietly and

usually undetected. The fire is caused by smouldering of the deposits

accumulated in the uptake. It usually occurs during boiler shutdown

or under light load condition. There is evidence that under normal

loads the flue gas "cools" the soot and the carbon deposits so that a

smouldering fire does not occur. In the absence of flue gas or if the

flue gas flow is insufficient to cool the deposits, they can catch fire.

When an uptake fire occurs, it results in very high exhaust

temperatures and excessive thick black smoke, mixed with sparks,

coming out of the uptake. The boiler must be shutdown immediately

and the blower switched off or the damper closed to stop any air

supply to the uptake. The fire service must be called. If the uptake is

common for several boilers, all the boilers must be shut down. The

key point is to stop the boiler air supply. No attempt should be made

to extinguish the fire by water unless the water supply is plentiful. A

steam fire may result if the water supply is not plentiful. The fire

should be allowed to die out. The fire must be contained by

restricting and removing any combustibles in the near vicinity.

To prevent an uptake fire, the operator must clean the uptake

periodically to eliminate accumulation of soot and unburnt carbon.

He should also exercise care in the daily operation of the boiler and

maintain the correct air/fuel ratio to ensure complete combustion of

fuel and minimize production of soot or unburnt carbon.

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M❤K