Thermal Engineering Interview Questions and Answers for freshers on “Boiler Accessories – 2”.
1. Convective superheater is placed in the furnace and it receives heat from the burning fuel through radiation.
a) True
b) False
Answer: b
Clarification: Convective superheaters receive heat from flue gases. Radiant superheaters are placed in the furnace. The wall tubes of radiant superheater receive heat from the burning fuel through radiant process. Radiant superheaters are usually used where the steam is to be raised to a high superheat temperature.
2. Steam separator reduces the wetness of the steam before it enters the engine or turbine.
a) True
b) False
Answer: a
Clarification: The function of a steam separator is to reduce the wetness of the steam by removing the water particles from the steam before it enters the steam turbine or engine. It is installed on the main pipe delivering the steam as close as possible to the engine.
3. Which of the following is NOT a valid type of steam separator?
a) Baffle (Impact) type
b) Tubular type
c) Reverse current type
d) Centrifugal type
Answer: b
Clarification: On the basis of principle of operation steam separators are classified into baffle or impact type, reverse current type and centrifugal type. There is a loss of heat in the steam pipe after the steam leaves the boiler which produces wetness. This wetness could damage the turbine or engine. Steam separator is installed close to the engine to remove the water particles and reduce the wetness of the steam.
4. What is the function of a steam trap?
a) It is used to store stem once the generation is complete
b) It prevents the leakage of steam from the boiler
c) It is used to increase the temperature of the steam
d) It captures the condensed steam from steam pipes and steam separators
Answer: d
Clarification: Steam trap captures the condensed steam from the steam pipes, steam jackets and steam separators. It doesn’t allow steam to escape. Removal of condensed steam is important because wetness could damage the engine or turbine.
5. Which of the following statement about convective superheater is TRUE?
a) It is located in the furnace
b) It absorbs heat from the burning fuel through radiant process
c) It absorbs heat from the flue gases
d) It is used where very high superheat temperature is required
Answer: c
Clarification: Convective superheaters utilize the heat from flue gases. It is radiant superheater that is located in the furnace and it absorbs heat from the burning fuel through radiant process. Radiant superheaters are generally used when a high superheat temperature is required.
6. Which of the following is NOT a valid type of air preheater?
a) Tubular type
b) Plate type
c) Temperature type
d) Storage type
Answer: c
Clarification: There are three types of air preheater – tubular type, storage type and plate type. There is no such category as temperature type. In tubular type air preheaters, the hot gases after leaving the boiler travel through inside of the tubes in a direction opposite to that of air and transfer some part of their heat to the air. In case of plate type air preheaters, the air absorbs the heat from the flue gases rushing through the heater at high velocity on the opposite side of the plate.
7. The degree of preheating does not depend on _____
a) type of fuel
b) initial temperature of air
c) type of fuel burning equipment
d) boiler and furnace ratings
Answer: b
Clarification: The degree of preheating doesn’t depend on initial temperature of air. It depends on type of fuel, type of fuel burning equipment and ratings at which boiler and furnace are operated. An air preheater increases the temperature of the air being supplied to the furnace for better combustion.
8. Which of the following statements about air preheaters is FALSE?
a) It increases the temperature of air being supplied to the furnace
b) Storage type air preheaters cannot be used in larger plants
c) The temperature of the hot gases released through the chimney is kept minimum
d) It facilitates the burning of fuel
Answer: b
Clarification: The temperature of the hot gases released into the atmosphere through the chimney is kept minimum for loss of heat. Storage type air preheaters are widely used in larger plants. An air preheater increases the temperature of the air being supplied to the furnace. It smoothens the burning of fuel and helps in combustion process.
9. What is the function of a superheater?
a) It increases the temperature of the air being supplied to furnace
b) It increases the temperature of steam above saturation temperature
c) It increases the temperature of feed water
d) It increases the temperature of the flue gases leaving the furnace
Answer: b
Clarification: The function of a superheater is to increase the temperature of steam leaving the boiler above saturation temperature. Economiser increases the temperature of the feed water being supplied to the boiler. Air preheater increases the temperature of the air being supplied to the furnace.
10. Which of the following statements about superheaters is TRUE?
a) Condensation losses in the cylinders and steam pipes are reduced
b) Turbine erosion is avoided
c) Increases efficiency of the steam plant
d) Steam consumption of the engine is increased
Answer: d
Clarification: Superheater reduces the steam consumption of the engine or turbine. It eliminates turbine erosion. It also reduces the losses due to condensation in the steam pipes and cylinders. Superheater being a boiler accessory increases the efficiency of the steam plant.
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