Let us discuss some of the operational faults which occur in the marine diesel engine during the starting and running of the main engine
1.The engine oscillates when being started or does not gain speed:
During the starting of the engine the engine is turned on air and during this operation the engine oscillates and it does not gain the speed to be started in the fuel.
So as the result the engine fails to start.
Possible causes for this are:
1.Individual cylinder receives only an insufficient amount of starting air, or none at all.
2.The starting air pressure is too low in general and cannot over come the compression counter-pressure .this happens more frequently with engines having only a few cylinders.
3.One or more starting air control slide valve is struck.
5.One or more starting valves are struck or defective.
4.Obstructed staring air pipes (flame baffles).If the is any obstruction it has to be removed first.
2.Scavenge air pressure charging receiver drops with the load indicator remaining in the same position:
At the time of running the scavenge air pressure drops and this causes the improper combustion. This is indicated in the scavenge air pressure indicator and immediate action has to be taken to bring back the scavenge pressure to normal condition
Possible causes for less scavenge air pressure are:
1.Turbocharger is either fouled or defective.
2.Loss of exhaust gases before turbine due to leakage in the exhaust pipe line from the Main Engine.
3.Intake filters of turbocharger are fouled. Protective grating before turbocharger is fouled.
4.Air loss on account of leakage (leaking stuffing box).
5.Increase in exhaust gas back-pressure after turbine.
3.Engine speed falls with load indicator remaining in the same position:
Possible causes are :
1.A component of the running gear is hot. Stop the engine immediately.
2.The hydrodynamic resistance of the ship’s hull is increasing.
3.The propeller is absorbing greater power.
4.The propeller shaft friction in the stern tube is excessive.
5.A fuel pump or fuel pipe is defective.
6.The priming plug on a fuel injector valve is either loose or leaking.
7.The holes of fuel valve nozzle are obstructed.
8.Defective scavenge air valves.
9.Defective or fouled turbocharger or air cooler (inadequate air supply).Protective grating before turbocharger may be fouled.
10.Fouled scavenge or exhaust ports.
11.Poor combustion.
This post is part of the series: Operating Faults In Main Engine
In this series we will get a clear idea on the operating troubles in main engine.
