31. The purpose of an air cooler in a supercharging system is to:
A. Reduce temperature of supercharged air in order to condense and remove maximum possible moisture from the air prior entry to the engine
B. Reduce the temperature of the supercharged air in order to increase the density & also to cool down below dew point to remove moisture from air prior entry to the engine
C. Cool supercharged air to increase its density such that the dew point is not reached to avoid entry of moisture into the engine
D. Cool supercharged air to increase its density and also to keep the peak temperature and exhaust gas temperature within limits
32. Which of the following is a disadvantage of water as cooling medium for pistons, when compared to oil?
A. Chemical treatment is required
B. Higher thermal stresses in piston
C. Piston of more complicated design
D. All of the above
33. Where boiler point temp high?
C) Primary steam drum
D) Secondary steam drum
34. Which of the following statements correctly describes the phenomenon of surging in a 2-stroke crosshead type engine?
A. Due to sudden increase in engine load the exhaust gases may flow back through scavenge ports causing surge
B. Due to sudden decrease in engine load the turbocharger pressure ratio drops. This causes high pressure downstream of T/C in scavenge trunk causing flow reversal of scavenge air
C. Due to sudden increase in engine load, the T/C turbine rpm may increase suddenly increasing the compressor pressure ratio to surge
D. Due to sudden decrease in engine load, the turbocharger may stall as the higher pressure downstream in exhaust system may cause reversal of flow of exhaust gases
35. Steam temperature control for the ESD-II boiler is achieved by:
A. Fitting a de-superheater between 1st & 2nd passes of superheater
B. Fitting an attemperator between 1st & 2nd passes of superheater
C. Gas dampers in boiler uptake
D. Bypassing the superheater
36. The coating which is provided on the valve stem of exhaust valves of modern marine diesel engines is of:
37. ESD stands for which type of boiler
A. External superheater D-type
B. Emergency shutdown Boiler
C. Extreme Superheat type
D. External Superheat De-superheater type
38. In comparison to exhaust valves, intake valves of diesel engines may be fabricated from low-alloy steels because
A. the beveled edges of the intake valves provide forself-centering during seating
B. intake valves utilize stellite-coated valve seat insertswhich reduce wear
C. the volume of air passing through intake valves is less than the volume of air passing through exhaust valves
D. intake valves are less affected to the corrosive action of exhaust gases
39. Why is it essential to renew turbocharger bearings after a preset number of hours of running even if the bearings are in seemingly perfect condition?
A. Because they are prone to failure due to prolonged exposure to high temperature conditions.
B. Because they are subject to cyclic loading and are prone to failure due to metal fatigue.
C. It is not essential to renew if condition monitoring suggests perfect condition.
D. Lube oil contamination is bound to occur and affect the condition of the bearings.
40. To check the setting of the over speed trip on a diesel powered generator, you would use a
B. torsion meter
D. pony brake