Chapter 4

  1. What is the main purpose of baffles in the setting of a boiler? 

    E.   To allow hot gases to make more than one pass through a boiler
  2. Which of the following are disadvantages of using baffles in a boiler setting?
    1.  Eddy currents can be produced
    2.  Increased friction can result
    3.  Coal fired boilers can result in pockets of ash accumulation
    4.  Heat transfer is increased 

    B. 1, 2, 3
  3. In order to direct the flow of combustion gas over the tubes in a watertube boiler, it is necessary to use _______.

    A. baffles
  4. Baffles can be placed so as to cause the gases to flow at right angles to the tube length, in which case they are called ________ baffles.
    a. longitudinal
    b. cross
    c. back
    d. straight
    b. cross
  5. Baffles may be placed so as to cause the gases to flow parallel to the tubes, in which case they are called _________ baffles.

    D. longitudinal
  6. Baffles are usually constructed of ___________ material and may be made up of individual bricks or tiles.

    B. refractory
  7. Curved or streamlined baffles have the ________ of having no sharp turns to cause eddy currents, increase friction, or form pockets for ash accumulation.

    A. advantage
  8. Metal fin bars are welded to adjacent tubes, forming a continuous surface and a pressure-tight wall, this is referred to as a welded fin tube wall or a ________ wall.

    A. membrane
  9. A wall suitable for severe service, here the tubes are side by side and touching each other, this is called a ________ wall.

    C. tangent tube
  10. Flat plates or studs are welded to each side of the tubes, this is called a _______ wall.

    C. flat stud tube
  11. In the watertube boiler, water cooling of the furnace is achieved by arranging tubes to form all or part of the furnace walls. Which of the following refers to this type of construction?
    1. Tangent tube wall
    2. Fin-welded tubes
    3. Tube and brick wall
    4. Flat-stud tube wall

    A. 1, 2, 3, 4
  12. The increased temperature of the steam means increased ____ per kg of steam and therefore the ability to do more work per kg.

    (B) Energy
  13. Initially the superheater will add ____ and once the steam becomes dry the superheater will begin to add ____ to the steam.

    (A) Latent heat, Sensible heat
  14. The purpose of the superheater is to raise the temperature of steam generated in the boiler above the ____ temperature.

    (A) Saturation
  15. Radiant superheaters have a ____ steam temperature characteristic.

    (B) Falling
  16. Steam produced from water in a boiler is at saturation temperature and usually contains a certain amount of moisture. The purpose of the superheater is:
    1. To save on chemical make-up to the boiler
    2. That any moisture present in the steam will be evaporated
    3. Is to help protect the turbine blades from erosion
    4. Is to allow more work per kg of steam

    D. 2, 3, 4
  17. Superheated steam:

    A. Has a temperature that is higher than the saturation temperature for that pressure
  18. Which of the following are types of superheaters:
    1. Primary 5. Convection
    2. Secondary 6. Pendant
    3. Conduction 7. Attemperator
    4. Radiant

    D. 1, 2, 4, 5, 6
  19. A primary superheater:

    A. Receives the saturated steam from the steam drum
  20. Which of the following correctly describes the manner in which pendent superheaters are suspended?

    D. Vertical
  21. Which of the following are integral superheaters?
    1. High pressure types
    2. Convection types
    3. Radiant types
    4. High temperature types

    D. 2, 3
  22. Superheaters shielded from the radiant heat of the furnace and located within the path of the hot combustion gases from the furnace are classed as ____ superheaters.

    (C) Convection
  23. The convection superheater has a ____ steam temperature characteristic.

    (C) Rising
  24. What does a "rising steam temperature characteristic" mean?
    1. At low loads, the steam temperature will be low
    2. The superheated steam temperature will rise as the firing rate or boiler output increases
    3. At high loads, the steam temperature will be high
    4. The temperature of the boiler feed water rises

    B. 1, 2, 3
  25. Which of the following has a rising steam temperature characteristic?

    E. Convection superheater
  26. Which of the following has a falling steam temperature characteristic?

    A. Radiant superheater
  27. A convection superheater:

    C. Has the hot combustion gases passing over it
  28. Combination superheaters combine the characteristics of the convection superheater and the radiant superheater resulting in a ____ steam temperature.

    (D) Steady
  29. Which of the following apply to the combination of a radiant superheater and a convection heater?

    1. Frequently steam-generating units have a convection superheater in series with a radiant superheater
    2. The steam enters the radiant superheater first and then the convection superheater
    3. A fairly steady steam temperature characteristic is produced
    4. Superheated steam temperatures remain fairly constant at all boiler loads

    D. 1, 2, 3, 4
  30. Which of the following are disadvantages in separately fired superheaters?
    1. Provides a wider range of temperature control
    2. Higher initial cost
    3. Lower operating efficiency
    4. Larger space requirement

    B. 2, 3, 4
  31. The separately fired superheater is located in a _______ apart from the main steam generator and is independent of the steam generator operating conditions.

    C. furnace
  32. The reheater receives steam, which has already expanded through a portion of the turbine, and as a result of this expansion has dropped in pressure and in _________.

    C. temperature
  33. A reheater is similar in construction and purpose to a ____.

    (B) Superheater
  34. The reheater receives steam, which has already expanded through a portion of the turbine, and as a result of this expansion has dropped in pressure and in _________.

    B. temperature
  35. In the reheater, the steam has its temperature raised to about the same temperature as was initially provided by the _________.

    A. superheater
  36. Reheaters are located in the furnace in areas of relatively _____ gas temperatures.

    B. high
  37. The temperature control methods used for reheater temperature control are the same as those used for __________ temperature control.

    D. superheater
  38. Which of the following are disadvantages of economizers?
    1. There is more thermal shock
    2. There is increased fan power
    3. Surfaces must be kept clean to provide increased efficiency
    4. More fuel is needed if the boiler has an economizer

    D. 2, 3
  39. Which of the following types of boilers use economizers?
    1. Water tube boiler
    2. Fire tube boiler
    3. Electric boiler
    4. Waste heat boiler

    B. 1, 2, 4
  40. Which of the following are advantages of an economizer?
    1. Not as much boiler feedwater is required
    2. There is less thermal shock to the boiler drum
    3. There is not as great a pressure drop through the unit
    4. There is an increase in boiler efficiency

    E. 2, 4
  41. What is the purpose of the handholes on certain economizers?
    1. Used for extra strength
    2. Used for installation
    3. Used for repair
    4. Used for inspection

    E. 2, 3, 4
  42. What is the main purpose of the cast iron fins on the economizer tubes?

    D. None of the above
  43. A component of a steam generator that absorbs heat from the furnace gases after the gas has passed through the furnace, superheater, and reheat sections is called an economizer.
    (a) True
    (b) False
    (a) True
  44. The two basic types of economizers are:

    D. Integral and separate
  45. An economizer is:
    1. An energy saving device
    2. A boiler feedwater preheater
    3. A device that has water inside tubes and hot gases on the outside
    4. A device normally located behind the air preheater

    C. 1, 3, 4
  46. Which of the following are classifications of economizers?
    1. Gas type
    2. Integral type
    3. Vertical type
    4. Separate type

    D. 2, 4

    • Fins ____ the effective heating surface of the tube.
    • (a) Decrease
    • (b) Increase

    (b) Increase
  47. Which of the following type of economizer is the most commonly used?

    A. Separate type
  48. Which of the following tube types are used on economizers?
    1. Extended surface tubes
    2. U bend tubes
    3. Continuous tube
    4. Fin tube

    C. 1, 2, 3, 4
  49. Which of the following statements apply to air heaters?
    1. This is another method of recovering heat from the flue gases
    2. They are often called air preheaters
    3. They consist of a heat exchanger surface located in the path of the combustion gases
    4. Combustion efficiency is improved

    E. 1, 2, 3, 4
  50. Which of the following are classes of air heaters?
    1. Pendent type
    2. Recuperative type
    3. Horizontal type
    4. Regenerative type

    E. 2, 4
  51. What is meant by "counter flow" when referring to air heaters?

    D. The flue gas and the air pass through alternate passages in opposite directions
  52. The main purpose of the baffles in the tubular air heaters are:

    E. To direct the air across the tubes in a number of passes
  53. Which of the following are advantages of air heaters?
    1. They have a low initial cost
    2. They increase the efficiency of the boiler
    3. They are easily maintained
    4. There is increased combustion efficiency

    E. 2, 4
  54. Which of the following could contribute to air heater corrosion?
    1. If the fuel contains sulphur compounds
    2. If the output of the air heater is too hot
    3. If the output of the air heater approaches the dew point
    4. None of the above

    C. 1, 3
  55. The two basic types of air preheaters are:

    E. Recuperative and regenerative
  56. Which of the following refers to recuperative air heaters?
    1. They are rotary heaters
    2. The heat from the flue gases passes through a plate or a tube wall to the air on the other side
    3. They are plate type air heaters
    4. They are tubular air heaters

    A. 2, 3, 4
  57. Which of the following statements refers to regenerative air heaters?
    1. They are stationary type heaters
    2. They are rotary type heaters
    3. Leakage of gas and air is largely prevented by means of radial and circumferential seals
    4. They may be arranged in either a vertical or a horizontal manner

    B. 2, 3, 4
  58. Hot spots not caused by slag indicate poor heat transfer through the tube walls.
    (a) True
    (b) False
    (a) True
  59. The water and water/steam mixture in the steam generation tubes is at _________ temperature.

    D. saturation
  60. The water ________ of the economizer exit is always below that of the steam drum to prevent steaming in the economizer.

    B. temperature
  61. Hot spots on tubes not caused by slag are a more serious problem. They indicate poor heat _______ through the tube walls.

    B. transfer
  62. Wet tubes on startup of the boiler are a _______ occurrence, caused by condensation on the tube walls.

    A. normal
  63. When starting up a boiler, a steam flow is needed through the __________ tubes for cooling.

    C. superheater
  64. There is no steam flow through the ______ tubes before the steam turbine has a steam flow through it. Be careful not to increase boiler firing too rapidly and overheat the reheat tubes, during startup.

    C. reheater
  65. The _________ increases the temperature of the steam from the H.P. turbine back up to superheat temperature.

    C. reheater
  66. When starting the boiler, it may be necessary to keep a flow of BFW through the _________ tubes to prevent overheating and fouling.

    B. economizer
  67. The temperatures of the flue gas leaving the preheater must be kept above the _______ to avoid condensation.

    D. dewpoint
  68. When the boiler is shut down, the air preheater should be inspected for signs of _______.

    C. corrosion
Card Set
Chapter 4
Chapter 4