The cause of scavenge fire is blow-by of combustion product between liner and piston into the scavenge air spaces. This fouling will be greater if soot is produced because of incomplete combustion of the fuel injected.
There are some causes of blow-by of combustion product, they are
Worn, sticking or broken piston rings,
Lubricating quills on liner are not working,
Damage to the running surface of liner,
The symptoms includes surging of turbocharger, rises of scavenge air temperature and exhaust temperature.
This problem could be prevented by careful maintenance, which includes draining the scavenge cock, regular inspections and cleaning of scavenge spaces
Detail refer to Marine Engineering Series – Diesel Engines A.J. Wharton
