1. INCREASE IN ENGINE LOAD:

• The fouling and the deformation of the ship's hull increases resistance to a fairly great extent ,liable to increase the engine load.
• Bending of propeller blades due to drifting woods and going aground subjects the engine to an increased load.

2. DEFECTIVE FUEL INJECTOR VALVE:

Exhaust gas temperature rises due to the enlarged nozzle hole of the fuel valve which was used for a long period of time.

3. FOULING OF EXHAUST GASES PASSAGE :

• Combustion products stick to the turbocharger nozzle and the surface of turbine blades,thus clogging the exhaust gas passage and exhaust gas passage and reducing the turbocharger efficiency.
• Failure of nozzle and blades of turbo charger caused by foregoing materials result the reduction in the turbine efficiency.

4. FOULING OF THE SCAVENGE AIR PASSAGE:

• Fouling of the air-side due to oil mist on suction casing and the diffuser of the turbocharger.
• clogging of cylinder liner scavenge port by combustion products.

5.Leakage of the scavenge air.

6. A FIRES OCCURS and air is insufficient .

7.Unsatisfactory purification of fuel oil.

8.Insufficient suction of air .

9.The scavenging valve in the scavenge air trunk is damaged or opening and closing function of scavenging valve is not good.

10.BLOW BY of exhaust valve.

11.Abnormal exhaust gas temperature or pressure in the cylinder.

12.Exhaust valve closing timing is deviated due to clogging of orifice of exhaust valve driving gear.

13.Usually before staring of the engine blow through procedure is carried out by opening the INDICATOR COCK, so as to take the excess fuel dripped from the injector and also to take out the water present inside the combustion chamber.when engine is started with out doing this a high exhaust temperature is formed.

Blow By of Exhaust Valve

If the following phenomena are observed during operation of the engine, damage of exhaust valve shall be doubted. In such a case quickly stop the engine, dismantle the susceptible exhaust valve, make inspection and repair it or replace parts with spare ones if necessary.

1. Rise in exhaust gas temperature.
2. Abnormality of compression pressure.
3. noise
4. abnormal pressure of cooling water pump.

The picture shows an exhaust valve of a main marine engine which has been removed and kept seperately for overhauling purposes.