Answer EKM Question 55

Q55. A. Difficulty has been experienced in maintaining engine speed at the set value; State THREE possible causes. State how each of these causes may be detected.

B. Describe the action to be taken in order to ensure safe operation of the main engine plant in the event of complete failure of the remote control and sensing equipment.

Answer: A. The three causes of difficulties in maintaining constant speed are:
(1) Bad weather:
A bad weather causes a rough sea and the immersed volume of the ship changes continuously with out any pattern. The ship experiences various motions in this case, pitching is one of them. If ship is experiencing heavy pitching its propeller will sinks and rise of water and cause a load fluctuation on the engine. This causes speed fluctuation in the engine. A governor is capable of keeping the engine in the set speed range. If the engine is fitted with a sensitive PID governor the fluctuation will only be mild but it will still be felt . If the engine is fitted with a proportional governor with servomotor the fluctuation will be intense.

(2) Air supply:
Combustion of fuel in the engine require an adequate amount of air to be supplied. Failure of this air supply causes engine to produce a reduced power and thus the desired set speed is difficult to achieve. This can be observed by the groaning sound of the surge condition of the turbocharger, further can be confirmed with a fluctuating RPM of turbocharger. The causes may be dirty felt filter of turbocharger or air cooler fauling.
This problem can be avoided by the periodic maintenance of air supply system of the engine. Clean/renew the felt filters as per manufacturers recommendation or when seems necessary. Keep the Air cooler clean and record the temperature difference of air and cooling water across the cooler to know the cleaning periods.

(3) Fuel supply:
To run an engine trouble free it is the most important factor to supply the compatible fuel to the engine. The fuel with different qualities not only cause the engine to run abnormally but also causes its parts to get damage before the service life. This recommended fuel must be well treated before being supplied to the engine.
Water may enter in the fuel system through various ways like heater leakages, atmospheric condensation, Purifiers etc,. Although the water is heavier than oil and does not mix easily with oil water particles or drops do find their way in the fuel and cause cooling effect during atomisation of the fuel and this reduces the combustion quality resuting in lower power and RPM. But this reduction is not a constant reduction as the water drop spread in the fuel is not homogeneous and hence conditions vary as per the quality of fuel in each stroke of the fuel pump leading to speed or input load fluctuation.
A regular draining of the service and settling tank is a good practice to avoid such problem.
Failing to maintain the viscosity of the fuel can also be the reason of restricted fuel supply to the engine. A proper watch on the temperature of fuel supplied is necessary. Additionally pumps and injectors of the engine are to keep properly maintained.

B. To ensure the safe operation during the failure of remote control and sensing devices the engine room should be put back to normal watch keeping instead of the day work. The engineers and watchkeepers are to be assigned duties with compliance of MLC-2006, so that the proper rest hours can be maintained.
As the sensing devices are no more functional the watch keepers must be extra careful and vigilant, regular fire and flooding rounds should be included. Watchkeepers are required to note the running machineries parametres from the local gauges and keep record for comparisons.