Steam Boilers Engines Nozzles and Turbines

41. Fire tube boilers are those in which

  1. flue gases pass through tubes and water around it
  2. water passes through the tubes and flue gases around it
  3. forced circulation takes place
  4. tubes are laid vertically
  5. none of the above.

Correct answer: (A)
flue gases pass through tubes and water around it

42. For burning 1 kg of carbon to CO as per chemically correct combusiton, amount of air required is

  1. 1 kg
  2. 4/3kg
  3. 8/3kg
  4. 2 kg
  5. 16/3 kg.

Correct answer: (B)
4/3kg

43. For combutsion of a fuel, following is essential

  1. correct fuel air ratio
  2. proper ignition temperature
  3. 02 to support combustion
  4. all the three above
  5. none of the above.

Correct answer: (D)
all the three above

44. For the same diameter and thickness of tube, a water tube boiler compared to a fire tube boiler has

  1. more heating surface
  2. less heating surface
  3. equal heating surface
  4. heating surface depends on other parameters
  5. none of the above.

Correct answer: (A)
more heating surface

45. For water, at pressures below atmospheric,

  1. melting point rises slightly and boiling point drops markedly
  2. melting point rises markedly and boiling point drops markedly
  3. melting point drops slightly and boiling point drops markedly
  4. melting point drops slightly and boiling point drops slightly
  5. none of the above.

Correct answer: (A)
melting point rises slightly and boiling point drops markedly

46. Fusible plug for boilers is made of fusible metal containing tin, lead, and

  1. bismuth
  2. copper
  3. aluminium
  4. nickel
  5. iron.

Correct answer: (A)
bismuth

47. Gardually increasing temperature of flue gases at inlet to chimney for given steam outputs is an indication of

  1. higher effectiveness of boiler
  2. high calorific value coal being burnt
  3. fouling of heat transfer surfaces
  4. raising of steam temperature
  5. leakage of air.

Correct answer: (C)
fouling of heat transfer surfaces

48. Green coal, in order to be burnt, must be

  1. heated sufficiently
  2. burnt in excess air
  3. heated to its ignition point
  4. burnt as powder
  5. burnt as lumps.

Correct answer: (C)
heated to its ignition point

49. Gusset stays in a boiler are provided to

  1. prevent the bulging of flat surfaces
  2. avoid explosion in furnace
  3. prevent leakage of hot flue gases
  4. support furnace freely from top
  5. prevent atmospheric air leaking into furnace.

Correct answer: (A)
prevent the bulging of flat surfaces

50. Hard coke is produced by carborisation of coal at

  1. atmospheric temperature
  2. 500-600°C
  3. 70O-850°C
  4. 95O-1100°C
  5. 120O-1500°C.

Correct answer: (D)
95O-1100°C

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