This set of Thermal Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Steam Generators – Boilers Selection and Terminology”.
1. Which of the following factors is NOT considered while selecting a boiler?
a) Available floor area
b) Number of tubes in the boiler
c) Available fuel and water
d) The portable load factor
View Answer
Explanation: While selecting a boiler its working pressure and quality of steam produced, steam generation rate, floor area available, accessibility for repairing parts, erection facilities, portable load factor, fuel and water available, operating and maintenance cost are the factors that are considered.
2. What is the usual geometry of a boiler shell?
a) Torus
b) Cuboidal
c) Cubical
d) Cylindrical
View Answer
Explanation: Boiler shell consists of one or more steel plates bent into cylindrical form that are riveted or welded together. Cylindrical geometry distributes stresses equally and has more strength and is easy to manufacture.
3. The function of “Setting” (Boiler term) is to confine heat to the boiler and form a passage for gases.
a) True
b) False
View Answer
Explanation: It is the primary function of “Setting” to confine heat to the boiler and form passage for gases. It is made of brickwork and also provides support to some type of boilers like in Lancashire boiler.
4. _____ is the platform in the furnace upon which fuel is burnt.
a) Shell
b) Grate
c) Setting
d) Heat exchanger
View Answer
Explanation: Grate is made of cast iron and it is the platform on which the fuel is burnt. The bars in the grate are arranged so that air may reach the fuel for proper combustion. The area on which the fire rests in a wood or coal fired boiler is called the grate surface.
5. What is the chamber formed by the space above the grate and below boiler shell called, where combustion takes place?
a) Grate surface
b) Mounting
c) Furnace
d) Setting
View Answer
Explanation: Furnace is where the combustion takes place and hot gases are released. Grate surface is the area over the grate available for burning fuel. Mountings like fusible plug, pressure gauges are attached for safe operation. Function of setting is to confine heat to the boiler shell.
6. In boiler terminology, the volume of the shell occupied by water is termed as _____
a) water space
b) steam space
c) wet volume
d) wet space
View Answer
Explanation: According to boiler terminology the volume of shell occupied by water is called water space. The rest of the volume of the shell is taken up by the steam and is called as steam space.
7. The items that are added to a boiler for safe operation are called _____
a) safety components
b) setting
c) accessories
d) mountings
View Answer
Explanation: Items such as stop valve, pressure gauges, safety valves, Water level gauges etc. are called mountings. A boiler cannot safely work without mountings. Items that are added to increase the efficiency of the boiler are called as accessories.
8. The items that are added to increase the efficiency of boiler are called _____
a) mountings
b) accessories
c) setting
d) boiler essentials
View Answer
Explanation: Items such as superheaters, economisers, feed pumps etc. are called accessories and they increase the efficiency of the boiler. Mountings are attached so that the boiler could be operated safely.
9. According to boiler terminology, Formation of steam bubbles on the surface of water is called _____
a) foaming
b) scale
c) lagging
d) bubbling
View Answer
Explanation: Foaming is the formation of steam bubbles on the surface of water. It happens due to high surface tension of water. Scale is the deposit of medium to extreme hardness occurring on water heating surfaces. Lagging are blocks of asbestos or magnesia insulation wrapped on the outside of a boiler shell.
10. Which of the following according to boiler terminology, is the term used for the deposition of medium to extreme hardness occurring on water heating surfaces because of undesirable condition in the boiler water?
a) Refractory
b) Foaming
c) Scale
d) Lagging
View Answer
Explanation: The correct answer is scale. Refractory is a heat insulation material. Lagging are blocks of asbestos or magnesia insulation wrapped on the outside of a boiler shell. Foaming is the formation of steam bubbles on the surface of water.
11. According to boiler terminology, the removal of the mud and other impurities of water from the lowest part of the boiler is termed as _____
a) lagging
b) blowing off
c) waste removal
d) foaming
View Answer
Explanation: The correct answer is blowing off. The removal of mud by blowing off is accomplished by use of a blow off cock or valve. Foaming is the formation of steam bubbles on the surface of water. Lagging are blocks of asbestos or magnesia insulation wrapped on the outside of a boiler shell.
12. What is lagging?
a) The formation of steam bubbles on the surface of water
b) Blocks of asbestos or magnesia insulation wrapped on the outside of a boiler shell
c) The deposit of medium to extreme hardness occurring on water heating surfaces
d) Heat insulation material
View Answer
Explanation: Lagging are blocks of asbestos or magnesia insulation wrapped on the outside of a boiler shell or steam piping. Refractory is a heat insulation material. Scale is the deposition of medium to extreme hardness occurring on water heating surfaces. Foaming is the formation of steam bubbles on the surface of water.
13. Which of the following is a refractory material?
a) Fire brick
b) Plastic
c) Wood
d) Paper
View Answer
Explanation: Refractory materials are heat insulation materials and they are supposed to withstand high temperatures. Refractory materials such as fire brick and plastic fire clay are used to make lining combustion chambers in boilers.
14. Furnace is also called fire-box.
a) True
b) False
View Answer
Explanation: Furnace is chamber where combustion of fuel takes place. It is also called as fire-box. Hot gases originate from furnace. It is the chamber formed by the space above the grate and below the boiler shell.
15. Which of the following is NOT a feature of a good boiler?
a) Light in weight
b) Steam production rate should be as per requirement
c) Capable of quick starting
d) Water and gas circuits should be such as to allow maximum fluid velocity
View Answer
Explanation: The water and gas circuits should be such as to allow minimum fluid velocity to minimize friction losses. Essentials of a good boiler includes – reliability, less space requirement, light in weight, accessibility to various parts, simple installation, steam production rate as per requirement, capable of quick starting.
Sanfoundry Global Education & Learning Series – Thermal Engineering
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