With respect to scavenge fires in large two-stroke marine engines:

1. Accumulation of oil and carbon deposits in the scavenge space (from over-lubrication, poor combustion, or oil draining down the liner).
2. Blow-by of hot combustion gases past the piston rings (due to worn/stuck rings or a worn liner), igniting the deposits in the scavenge space.
3. A leaking fuel injector or fuel in the scavenge space.
4. A hot spot in the scavenge space (e.g. from a damaged liner or a hot piston) igniting the deposits.
5. Running at low load for a long time, causing deposits to build up.

1. A rise in the scavenge air temperature (and the scavenge space temperature).
2. A rise in the exhaust temperature of the affected cylinder.
3. A change in the engine noise (a dull thud or knocking).
4. Smoke or flames from the scavenge space drain/relief valves.
5. A rise in the scavenge air pressure (or a change).
6. A rise in the liner/jacket water temperature of the affected cylinder.
7. The engine may run roughly or lose power.

1. Reduce the engine load (to a minimum) to reduce the heat input and the blow-by.
2. Stop the engine if the fire is severe (or if the load reduction does not control it).
3. Cut off the fuel to the affected cylinder (if possible) to stop the combustion.
4. Increase the cylinder lubrication (to help cool and seal) - but only if safe.
5. Do NOT open the scavenge space doors (admitting air would feed the fire); use the scavenge space fire-extinguishing system (steam or CO2) if fitted.
6. Keep the engine turning (on turning gear) to prevent the piston/liner from seizing, if safe.
7. Monitor the temperatures and the engine.

1. Allow the engine to cool, then inspect the scavenge space and the affected cylinder.
2. Clean the scavenge space and remove all the carbon and oil deposits.
3. Inspect the piston, rings, and liner for damage (scuffing, cracks, distortion).
4. Inspect the scavenge space relief valves and the drains for damage.
5. Check the fuel injectors and the cylinder lubrication.
6. Check the scavenge air system and the turbocharger for damage.
7. Rectify the cause of the fire (e.g. worn rings, over-lubrication, leaking injector) before restarting.
8. Restart the engine at low load and monitor the temperatures, then increase the load gradually.