Causes,Symptoms,Action & Precaution of Scavenge Fire

Causes of scavenge fire
  •  Cylinder oil can collect in the scavenge space of an engine. 
  • Unburned fuel and carbon may also be blown into the scavenge space as a result of defective piston rings, faulty timing, a defective injector, etc
  • A build-up of this flammable mixture presents a danger as a blow past of hot gases from the cylinder may ignite the mixture, and cause a scavenge fire.

Symptoms for scavenge fire
  • A loss of engine power will result, 
  • high exhaust temperatures at the affected cylinders.
  • The affected turbo-chargers may surge and 
  • sparks will be seen at the scavenge drains.

Actions to be taken when scavenge fire occurs
  • Once a fire is detected the engine should be slowed down,
  •  shut off fuel for the affected cylinders and cylinder lubrication increased.
  • All the scavenge drains should be closed.
  • A small fire will quickly burn out, but where the fire persists the engine must be stopped.
  • A fire extinguishing medium should then be injected through the fittings provided in the scavenge trunking.
  •  On no account should the trunking be opened up.

Precautions to be taken to avoid scavenge fire
  • To avoid scavenge fires occurring the engine timing and equipment maintenance should be correctly carried out.
  • The scavenge trunking should be regularly inspected and cleaned if necessary.
  • Where carbon or oil build up is found in the scavenge, its source should be detected and the fault remedied.
  • Scavenge drains should be regularly blown and any oil discharges investigated at the first opportunity.

ref: introduction to marine engineering by D A Talyor

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