250+ TOP MCQs on Constituents of Steam Power Plant and Answers

Power Systems Multiple Choice Questions on “Constituents of Steam Power Plant”.

1. What is the principle of operation of steam power plant?
A. Carnot cycle
B. Brayton cycle
C. Stirling cycle
D. Rankine cycle
Answer: D
Clarification: The Rankine cycle is an idealized thermodynamic cycle of heat engine. Under this cycle heat energy is converted into mechanical energy while undergoing phase change. The heat is supplied externally to the closed loop which usually uses water as working fluid.

2. Read the following statement about boilers.
I. Water tube boiler is capable of generating steam of pressure more than 50 kg/cm2 .
II. Fire tube boiler is suitable for generating steam of pressure less than 17.5 kg/cm2 .
III. Water tube boiler occupy comparatively less space.
A. Only statement I is true
B. Statement I, II and III are true
C. I and II are true but III is false
D. I and III are true but II is false
Answer: B
Clarification: In fire tube boiler water and steam are in same shell so higher pressure is not possible. In water tube boiler comparison to fire tube boiler, the drum do not contain any tabular heating surface so they can be built in smaller diameter and consequently they will withstand higher pressure.

3. Fire tube boilers are safer than water tube boilers.
A. True
B. False
Answer: B
Clarification: In event of sudden and major tube failure steam explosion may occur in furnace of fire tube boiler due to rush of high pressure water into hot combustion chamber. Water tube boiler does not contain such tubular heating surfaces so no such problem arises there.

4. Which of the following material is not used in the boiler furnace walls?
A. Fire clay
B. Concrete
C. Silica
D. Kaolin
Answer: B
Clarification: Fire clay, Silica and Kaolin have property of resisting change in shape, weight or physical property at higher temperature. Concrete have no such properties at higher temperature so it is not suitable for that. The construction of boiler furnace varies from plain refractory walls to completely water cooled walls depending upon the characteristics of fuel used and firing methods.

5. Which of the following statement about economiser of steam power plant is wrong?
A. Economiser increases the Boiler Efficiency about 5 to 15%
B. It uses the heat of flue gases used by boiler going to the chimney.
C. Economiser increases the temperature of intake air
D. It require regular maintenance and cleaning
Answer: C
Clarification: Economiser is used to rise the temperature of feed water. Air preheater is used to raise the temperature of intake air. Flue gases after heating boiler water Still possesses sufficient heat energy which if not used will waste. Economiser and air preheater uses that heat energy to work and hence increase the thermal efficiency of power plant about 15%.

6. Which of the following are the most widely used condensers in modern thermal power plants?
A. Surface condensers
B. Low level counter flow type jet condenser
C. High level counter flow type jet condenser
D. Parallel flow type jet condenser
Answer: A
Clarification: Power plants mostly use surface condensers because from these condensers condensate can be used as feed water requiring less pumping power. In case of jet condensers exhaust steam mixes with the cooling water hence condenses and cooling water are mixed so condensing cannot be recovered for the use of feed water.

7. Read the following statements about feed water heaters
I. Open or contact heaters are also called Deaerator.
II. Open or contact heaters constructed to remove non-condensable gases from feed water.
A. Only statement I. is correct
B. Only statement II. is correct
C. I. and II. are correct
D. I. and II. are wrong
Answer: C
Clarification: Dissolved gases can cause corrosion inside the boiler so they must be removed from feed water. Feed water heaters are used to heat the feed water by means of bled steam before it is supplied to the boiler. The amount of non-condensable gases decreases with increase in temperature of water in open heaters hence called Deaerator.

8. Which of the following is a part of air and fuel gas circuit?
A. Condenser
B. Economiser
C. Air preheater
C. Cooling tower
Answer: C
Clarification: In air and fuel gas circuit air is drawn from the atmosphere by a forced draught fan or induced draught fan through the air preheater. In air preheater that air is heated by the heat of flue gases passing to the chimney and then admitted to the furnaces. Cooling tower and Condenser are parts of Cooling water circuit and Economiser is part of Feed water and steam circuit.

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