Thermal Engineering Questions and Answers – Boiler Accessories – 1

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This set of Thermal Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Boiler Accessories – 1”.

1. Boiler Accessories increase efficiency of the steam boilers.
a) True
b) False
View Answer

Answer: a
Explanation: Boiler accessories are auxiliary plants that help in proper operation of the boiler and also increase its efficiency. Feed pumps, injector, superheater, air preheater, economizer, superheater are some commonly used boiler accessories.
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2. Which of the following is NOT a boiler accessory?
a) Feed pump
b) Steam trap
c) Steam separator
d) Mud hole (sight hole)
View Answer

Answer: d
Explanation: The correct answer is mud hole (or sight hole). Feed pump, steam trap, steam separator are all boiler accessories whereas a mud hole is a boiler mounting. Boiler mounting increases the efficiency of the boiler.

3. Which of the following statements about feed pump is TRUE?
a) It is used to deliver feed water to the boiler
b) It is used to take out steam from the boiler
c) It is a boiler mounting
d) It delivers air to the combustion chamber
View Answer

Answer: a
Explanation: Feed pump is used to deliver feed water to the boiler. Reciprocating pump and rotary pump are the commonly used feed pumps. Reciprocating pump is classified into single acting and double acting pump.
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4. Which of the following statements about reciprocating feed pumps is FALSE?
a) Water is discharged in alternate strokes in single acting pump
b) Water is discharged in each stroke in double acting pump
c) They are supplied steam from the boiler itself
d) In double acting pump water us displaced by only one side of the piston
View Answer

Answer: d
Explanation: In a double acting reciprocating pump, water is displaced by both side of the piston. This is the reason why water is discharged in each stroke. In case of single acting pump water is displaced be only one side of the piston and hence water is discharged in alternate strokes.

5. The rotating element of the rotary feed pump is called _____
a) impeller
b) propeller
c) armature
d) propulsor
View Answer

Answer: a
Explanation: Impeller is the correct answer. Rotary pumps are usually run by an electric motor or small steam turbine. It makes use of the centrifugal force of the rotating impeller for pumping the water.
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6. Which of the following is TRUE about an injector?
a) It feeds water into the boiler
b) Kinetic Energy of steam is utilized to increase velocity of feed water
c) It is used where there isn’t enough space to install feed pump
d) It is ideal for high capacity high pressure boilers
View Answer

Answer: d
Explanation: Injector is used to feed water into a boiler. It is used in place of feed pump when there isn’t enough space to install a feed pump. It is usually used in vertical and locomotive boilers. It is not at all used in case of high capacity and high pressure boilers.

7. Pumping efficiency of an injector is high.
a) True
b) False
View Answer

Answer: b
Explanation: The pumping efficiency of an injector is low. But its thermal efficiency is high. It is compact and has low initial cost. It cannot be used to force very hot water.
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8. What is the function of economizer?
a) It is used to heat the feed water
b) It is used to improve the quality of steam
c) It is used to heat air being supplied for combustion
d) It separates suspended water particles from steam
View Answer

Answer: a
Explanation: Economizer makes use of waste heat from the hot gases to heat the feed water before suppling it to the boiler. There are two types of economizers – independent type and integral type. Independent type economizer is installed in the pathway of the hot gases. Integral type economizer is situated in the boiler setting itself.

9. Which of the following statements about vertical tube economiser (Green’s economiser) is FALSE?
a) It is used with boilers operating below 25 bars
b) It is an integral type economiser
c) The direction of flow of flue gases is opposite to that of water
d) It consists of a blow-off cock for removal of sediments
View Answer

Answer: b
Explanation: Green’s economiser is an independent type economiser. It is put into service for boilers of medium pressure range upto about 25 bar. The direction of flow of flue gases around the tubes is opposite to the flow of the water. A blow-off cock is allocated at the end of vertical pipes for removal of sediment deposits.
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10. What is the function of an air preheater?
a) It increases the temperature of air before it enters the furnace
b) It increases the temperature of hot gases before they are released into the atmosphere
c) It reduces the temperature of hot gases before they are released into the atmosphere
d) It improves the quality of steam by mixing it with hot air
View Answer

Answer: a
Explanation: The function of an air preheater is to heat the air that is supplied to the furnace. It helps in the combustion and eases the burning of coal. It consists of plates or tubes with hot gases on one side and air on the other.

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