Motor Engineering – MEO CLASS 4 MMD PAPER

31. What do you mean by surge limit of a turbocharger?

1. Characteristic curve of a turbocharger
2. Portion of compressor characteristic curve which lies on the left side of the point of maximum pressure
3. A line joining all the points of maximum pressure on compressor characteristic curves , drawn at various speeds of operation
4. Maximum rpm limit of T/C above which surging will start

ANS.: C

32. A large, low-speed, main propulsion diesel engine uses sea water to directly cool the

1. A. cylinder heads
2. B. exhaust valves
3. C. scavenging air
4. D. injectors

ANS.: C

33. Exhaust Grouping is required in case of ______________ turbocharging in order to

1. Constant pressure, prevents shockwave generation
2. Pulse pressure, prevent interference with scavenging of other cylinders
3. Constant pressure, prevent interference with scavenging of other cylinders
4.  Pulse pressure, prevents shockwave generation

ANS.: B

34. Function of a de-superheater is to.

1. A. Protect superheater from overheat
2. B. Control superheater steam outlet temperature
3. C. Increase the efficiency of the boiler
4. D. Reduce steam temperature for auxiliary uses after steam superheater

ANS.: D

35. Which of the following statements is false?

1. Oxidation of lubricant leads to decrease in its viscosity
2. Formation of oxidation acids, sulphuric acid leads to depletion of TBN of lubricant
3. Contamination with water will lead to decrease in the load carrying capacity of a lubricant.
4. Build up of insolubles will lead to increase in viscosity of a lubricant

ANS.: A

37. After prolonged operation, jerk type fuel pumps wear on the top edge of plunger and edges of spill ports and helix due to erosion by high pressure fuel as it spills. This wear would result in

1. Late start of injection and early end of injection
2. Early start of injection and late end of injection
3. Early start of injection and early end of injection
4. Late start of injection and late end of injection

ANS.: A

38. Labyrinth seal fitted on the back surface of a compressor wheel of a turbocharger fitted on turbine side use     

1. Prevents bearing lube oil contamination
2. Prevents bearing lube oil being sucked into the air stream
3. Helps to keep the shaft cool by controlled leakage of air
4. None of the above

ANS.: B

39. It is a known fact that centrifugal pumps require priming for pumping liquids , as they cannot handle air and will lose suction due to air entry . But on the other hand T/Cs use centrifugal compressors for supercharging. Which of the following do you think makes a centrifugal compressor to pump air and behave differently than the centrifugal pumps?    

1. Presence of air cooler
2. Presence of Labyrinth seal
3. High speed of rotation, very fine internal clearances and large impeller diameters
4. Difference in principle of operation

ANS.: C

40. If an operating auxiliary boiler has a water pH reading of 7, you should

1. bottom blow the boiler
2. treat the water with caustic soda
3. treat the water with chemical scavengers
4. reduce the water alkalinity to recommended readings

ANS.: B

41. In case of 2-stroke marine diesel engines, the top part of the liner forming the combustion chamber experiences very high pressure induced mechanical stresses as well as high thermal stresses. Which of the following is a correctly designed liner for catering both the above stresses?
    1. Thick top portion with jacket cooling to take care of both the high mechanical and thermal stresses
    2. Thick top portion to take care of high mechanical stresses while bore cooling to reduce thermal gradients
    3. Thin top portion to reduce thermal gradients and hence thermal stresses while supporting ribs to take care of mechanical stresses
    4. Thick top portion to take care of high mechanical stresses with jacket cooling combined with allowance for thermal expansion to minimize the thermal stresses

ANS.: B

42. Which of these fuel oil impurities can cause maximum abrasive damage?
    1. Water
    2. Ash
    3. Catalytic fines
    4. Sodium

ANS.: C

43. In modern marine 2-stroke diesel engines, __________ is sometimes used as a coating on the underside of the exhaust valve disc, to reduce the rate of hot corrosion.
    1. Monel
    2. Chromium
    3. Inconel
    4. Cermet

ANS.: C

44. Irregular circumferential wear of liner due to diminishing neutralizing capacity of cylinder oil away from lubricating holes is known as:
    1. Micro seizure
    2. Scuffing
    3. Scoring
    4. Clover leafing

ANS.:  D

45. Which of the following is a reasonable statement about water washing of turbine side of a T/C ?
    1. It leads to thermal shock and reduces the life of the T/C
    2. It leads to thermal shock and not so effective as solid washing
    3. If properly carried out keeping rpm, load, temperature limits & other factors into account; it is quite safe and more effective than solid washing
    4. It should never be carried out as most of the engine manufacturers recommend against the same

ANS.: C

46. Which of the following statements correctly describes the phenomenon of surging in a 2-stroke crosshead type engine?
    1. Due to sudden increase in engine load the exhaust gases may flow back through scavenge ports causing surge
    2. 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
    3. Due to sudden increase in engine load , the T/C turbine rpm may increase suddenly increasing the compressor pressure ratio to surge
    4. 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

ANS.: B

47. If the boiler tubes are scaled on the water side then
    1. Heat conduction through the tubes will be very high leading to rapid evaporation
    2. The boiler furnace can get damaged due to excessive temperatures
    3. The surface of the tube will be overheated as heat transfer is impaired
    4. The natural circulation of water within the boiler will be more efficient

ANS.: C

48. Fins are installed on the generating tube surfaces in waste heat boilers to
    1. Prevent soot fires in the exhaust system                    
    2. Prevent exhaust gas erosion of the tubes                   
    3. Increase the velocity of exhaust gas flow                  
    4. Increase the rate of heat transfer

ANS.: D            

49. Any steering gear system alarm can only be successfully acknowledged from
    1. The bridge
    2. The engine control room
    3. The steering compartment
    4. The ship’s office

ANS.: B

50. To check the setting of the over speed trip on a diesel powered generator, you would use a
    1. tachometer
    2. torsion meter
    3. dynamometer
    4. pony brake

ANS.: A

51. Which of the following specifications/qualities of cylinder oils counter corrosive wear?
    1. Viscosity
    2. TBN
    3. Detergency
    4. Specific gravity

ANS.: B

52. What is meant by elastohydrodynamic lubrication?
    1. Formation of hydrodynamic film under high pressure with minor elastic deformation of mating surfaces, distributing load over a greater area
    2. Addition of extreme pressure additive (EP) to the lubricant
    3. Addition of Viscosity index improvement additive
    4. Addition of elastomer based additives

ANS.: A

53. In a bypass type filtering system for a medium or high speed diesel engine, the lube oil bypassing the filter
    1. returns directly to the suction side of the pump
    2. returns directly to the sump
    3. flows to the engine bearings
    4. flows through a second-stage strainer, reheater, and returns to the sump

ANS.: C

54. Which type of boiler burner has max turn down ratio?
    1. Pressure set
    2. spinning cup
    3. Spill type
    4. Y-jet type

ANS.: D

55. Most steam traps respond well to cleaning. But when a thermodynamic trap fails to operate after cleaning, the next course of action should be
    1. throttle the steam outlet valve
    2. renew the trap
    3. lap the disc and seat the trap
    4. throttle the steam inlet valve

ANS.: C

56. Types of corrosion in fresh water of D/E
    1. Stress
    2. hot corrosion
    3. bimetallic
    4. selective phase corrosion

ANS.: D

57. Which of the following types of damages are metal seatings of a valve subject to? Choose the correct alternative.

1. Corrosion, Erosion, Abrasion, Deformation
2. Corrosion, Fatigue failure, brittle fracture, caustic cracking
3. Erosion, caustic cracking, brittle fracture, Clover leafing
4. None of the above

ANS.: A

58. When A/E stand by F.O. heater to be used for main engine
    1. Sudden opening F.O. inlet valve pressurized and damage the heater
    2. F.O. in vapor lock inside heater allow steam
    3. F.O. inlet valve causes pressure drop M/E F.O. pressure standby water is not pressurized may cause sudden change in engine /per load/rpm
    4. heater leaking

ANS.: C

59. Viscosity of fuel oil used for ME was 145cst, new fuel comes whose viscosity was more than earlier, what u should do
    1. Increase temp setting
    2. Change setting of viscotherm
    3. Do nothing
    4. Open steam valve manually more

ANS.: C                                                                       

60. Which of the following can be done to reduce the cold corrosion of Main Engine cylinder liners using high sulphur fuel oil
    1. Increasing cylinder oil feed rate
    2. using high TBN cylinder oil
    3. Increasing scavenge air temperature
    4. Decreasing cylinder oil feed rate

ANS.: B