This set of Thermal Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Steam Generators – Fire Tube Boilers – 1”.
1. In Simple Vertical boiler, the ash that falls off from the grate falls in the _____
b) ash pit
c) ash disposer
Explanation: The correct answer is ash pit. Grate is a mesh on which fuel is burnt, and after combustion the ashes fall down in the ash pit. While cleaning, this ash is removed from the ash pit.
2. What is the highest steam production rate that can be achieved by Simple Vertical boiler?
a) 1000 kg/hr
b) 2500 kg/hr
c) 3000 kg/hr
d) 5000 kg/hr
Explanation: Steam production rate in case of Simple Vertical boiler does not exceed 2500 kg/hr. The pressure of the steam produces is also limited to 7.5 to 10 bar.
3. In a Simple Vertical boiler, two cross tubes are provided with the fire box. Which of the following statement about the orientation of these tubes is correct?
a) Both of them are vertical
b) Both of them are horizontal
c) Both of them are inclined
d) One is horizontal and the other one is vertical
Explanation: Cross tubes are fitted inclined. The presence of cross tubes increases the heating surface. The inclined orientation of the cross tubes ensures effective circulation of the water. For cleaning purpose, hand holes are provided at the end of each of these tubes.
4. What is the purpose of fire door in boilers?
a) It is opened to increase air supply for combustion
b) It is opened to put out the fire, in case of emergency
c) It allows the hot gases to pass safely through chimney
d) It is used to feed fuel for combustion
Explanation: Fire door is provided to feed fuel to the fire. It is provided near the grate. Fire doors must have high resistance to heat.
5. Cochran boiler is a multi-tube boiler.
Explanation: Cochran boiler is a multi-tube boiler. It is vertical and has a number of fire tubes arranged horizontally. The height of the boiler is 5.79 m and working pressure is around 6.5 bar usually.
6. What is the shell diameter of a Cochran boiler?
a) 2.00 m
b) 1.50 m
c) 1.00 m
d) 2.75 m
Explanation: The shell diameter of the Cochran boiler is 2.75 m. Its height is 5.79 m. It has a maximum working pressure of 15 bar but is usually operated at around a pressure of 6.5 bar.
7. What is the height of a Cochran boiler?
a) 5.79 m
b) 4.10 m
c) 4.26 m
d) 3.50 m
Explanation: The height if Cochran boiler is 5.79 m. It has a maximum working pressure of 15 bar but is usually operated at around a pressure of 6.5 bar. Steam capacity is around 3500 kg/hr with maximum steam capacity of 4000 kg/hr.
8. What is the maximum working pressure of Cochran boiler?
a) 8 bar
b) 10 bar
c) 15 bar
d) 20 bar
Explanation: The maximum working pressure of Cochran boiler is 15 bar. It has a maximum steam capacity of 4000 kg/hr. It is usually operated around 6.5 bar. It has an efficiency of 70 to 75 % which depends on the fuel used.
9. What is the area of the heating surface of a Cochran boiler?
a) 100 m2
b) 120 m2
c) 150 m2
d) 200 m2
Explanation: The heating surface of a Cochran boiler has an area of 120 m2. Cochran boiler is a vertical multi-tube boiler. It is a fire tube boiler with working pressure around 6.5 bar and Steam capacity of 3500 kg/hr.
10. What is range of efficiency of a Cochran boiler?
a) 50 – 55%
b) 60 – 65%
c) 70 – 75%
d) 80 – 85%
Explanation: The efficiency of a Cochran boiler varies in the range of 70 to 75%, it depends on the fuel used. The steam capacity of a Cochran boiler is 3500 kg/hr and working pressure around 6.5 bar. The maximum steam capacity and working pressure are 4000 kg/hr and 15 bar respectively.
11. Which of the following statements is correct about the smoke box in boilers?
a) It collects smoke and is emptied later after being done operating the boiler
b) It regulates hot gases from tubes to chimney
c) It treats the smoke before it is released to the atmosphere
d) It is used to store ashes
Explanation: The hot gases produced by the combustion of fuel in the furnace pass through the tubes (in case of fire tube boilers) or go about the tubes containing water (in case of water tube boilers) and then they are released to atmosphere through smoke box and chimney.
12. Which of the following boiler mounting is NOT present in a Cochran boiler?
a) Stem stop valve
b) Blow off cock
c) Safety valve
d) Fusible plug
Explanation: Cochran boiler has water level gauge, safety valve, steam stop valve, blow off cock, man hole and a pressure gauge as its mountings. Mountings are provided for the safe operation of the boiler. Cochran boiler doesn’t have a fusible plug.
13. How many flue-tubes does a Cornish boiler has?
Explanation: Cornish boiler has only one flue tube, it is a single tube boiler. It has a shell of diameter 1.25 to 1.75 m and length ranging from 4 m to 7 m. The steam capacity of a Cornish boiler is 6500 kg/hr.
14. What is the steam capacity of a Cornish boiler?
a) 5500 kg/hr
b) 6500 kg/hr
c) 7500 kg/hr
d) 8500 kg/hr
Explanation: The correct answer is 6500 kg/hr. The pressure of the steam produces is around 10.5 bar. Cornish boiler is a single tube boiler, it has only one tube through which the flue gases pass.
15. Lancashire boiler is easy to operate and has less maintenance and operating costs.
Explanation: Lancashire boiler has a simple design, easy to operate and reliable. The maintenance cost and operating cost are also less as compared to other boilers. It is generally used in textile industries and sugar mills.
Sanfoundry Global Education & Learning Series – Thermal Engineering
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