Answer MEP Question 10

Q. With reference to main engine automatic slowdown and shutdown systems; 

A. List TWO parameters for shutdown and slowdown, state reasons for having these parameters for shutdown and slowdown of engines. 

B. How are the above-chosen parameters tested while the engine is in operation?

A. 1. The following two items will initiate an engine shutdown: 

- Low lubricating oil pressure - this is fitted to prevent bearing failure and bearing overheating that could lead to a crankcase explosion, Seizure of running gear. 

- High jacket water temperature - this is fitted to prevent a piston seizure within the liner and possible liner failure.

2. The following two items will initiate an engine slowdown:

High cylinder exhaust temperature - this will reduce the engine load and hence prevent possible engine overload. 

High scavenge temperature - this will reduce the engine load and hence reduce the piston ring blow past reducing the scavenge trunk temperature.

B. How are the above chosen parameters tested while engine is in operation? 

- For the shutdown parameters, the shutdown override would be engaged to prevent any shutdown activating the engine shutdown device. 

- Engine monitoring and logging down parameters are carefully done during the test period to compensate for the override condition. 

- For the LO pressure trip, the line to the pressure sensor would be isolated and disconnected. A pressure line would be fitted to the sensor and the pressure raised above the trip point and slowly reduced. At the point where the trip activates, the pressure would be recorded. If this pressure is incorrect, the sensor would be adjusted. 

- For the high jacket water trip, the probe would be removed from its pocket and inserted into the temperature probe test unit. The temperature of the test unit would be increased up to the trip temperature and the trip circuit monitored for activation. The shutdown panel would be reset, and the override disengaged. 

- For the slowdown parameters, the slowdown override would be engaged to prevent any slowdown activating the engine load reduction. 

- Engine monitoring and logging down parameters are carefully done during the test period to compensate for the override condition. 

- For both the high exhaust temperature and scavenge air temperature slowdown, the probes would be removed from their pockets and inserted into the temperature probe test unit, the temperature of the test unit would be increased up to the activation temperature and the alarm circuit monitored. If the activation temperature was found to be incorrect, the trip setting would be adjusted accordingly. The slowdown panel would be reset, and the override disengaged.