This set of Energy Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Boiler Mounting Accessories – 1”.
1. How many level indicators are there in the water level indicator of a boiler?
Explanation: The function of the water level indicator is to indicate the level of water inside the boiler drum at any given instant. Two water level indicators (one as a standby) are fitted at the front of the boiler drum. The boiler operator keeps track of water level in the drum and operates the feed pump as per the requirement to maintain a constant level of water inside the drum.
2. What is the function of pressure gauge in the boiler?
a) To indicate steam pressure
b) To indicate water pressure
c) To indicate Air pressure
d) To indicate Flue gas pressure
Explanation: The function of the pressure gauge is to indicate the steam pressure inside the boiler drum in bar or in Kgf in cm2 or in KN/m2 in gauge pressure. If the boiler is fitted with a superheater, one more pressure gauge fitted to the superheater header indicates the superheated steam pressure at any given instant.
3. other than Steam stop valve in the boiler which is the other similar type of valve used?
a) Non-reversible valve
b) Transient valve
c) Reversible valve
d) Junction valve
Explanation: Stop valve and junction valve are essentially same. Conventionally stop valves are smaller in size whereas, junction valves are larger. When the valve is mounted on the top most portion of the steam drum, normally the valve is called junction valve. If it is connected in the steam pipe to regulate the flow of steam, the valve is known as stop valve.
4. What type valve is a feed check valve of a boiler?
a) One way valve
b) Globe valve
c) Reversible valve
d) Disc check valve
Explanation: Feed check valve regulates the flow of feed water under pressure to the boiler drum. It is essentially a one way valve and allows water to flow only in one direction i.e., towards the boiler drum. No water flows back to the boiler drum.
5. What is the function of Blow down valve of a boiler?
a) To remove sludge
b) To build sediments
c) To remove Flue gas
d) To remove ash
Explanation: Blow down valve is also called as Blow-off-cock. The function of this valve is to remove the sludge or sediments collected at the bottom of the boiler drum from time to time. Whenever boiler cleaning and inspection is due, water inside the tubes and in the boiler drum can be completely drained by operating the blow down valve.
6. What is the function of fusible plug in the boiler?
a) Protect the fire tube
b) To trip on overload
c) To act as a junction switch
d) To maintain pressure
Explanation: The function of the fusible plug is to protect the fire tube from burning due to excessive heating. This usually happens when the water level inside the drum becomes too low and the shell and crown plate are directly exposed to steam space.
7. What is the function of safety valves in the boiler?
a) To prevent excessive steam pressure
b) To prevent excessive air pressure
c) To prevent water pressure
d) To prevent from rising temperatures
Explanation: The function of safety valve is to prevent the excessive steam pressure inside the boiler drum exceeding the design pressure. When the pressure inside the boiler drum exceeds the rated pressure, safety valve automatically opens and discharges the steam to the atmosphere till normal working pressure is retained.
8. How many types of safety valves are used in boiler in practice?
Explanation: Two types of safety valves are used in practice
i) Spring loaded safety valve
ii) Dead weight safety valve
9. What happens due to high temperature of feeds water in the economizer?
a) Fuel consumption increases
b) Fuel mechanical efficiency increases
c) Fuel consumption decreases
d) Fuel mechanical efficiency decreases
Explanation: Function of the economizer is to recover a portion of heat of the exhaust gases before the flue gases enter the chimney and discharged to the atmosphere. Due to the high temperature of feed water, fuel consumption reduces. This increases the overall efficiency of the boiler.
10. What is the function of superheater in the boiler?
a) Increase the temperature of steam
b) Reheat the steam
c) Superheat the feed water
d) To heat the fuel gas
Explanation: Function of the superheater is to increase the temperature of steam above its saturation temperature. As heat contained in unit mass of superheated steam is more than dry saturated or wet steam, it is extensively used in steam power plants.
11. What is the function Air heater in the boiler?
a) Preheat the air before entering the boiler
b) Recover the heat from flue gas
c) Heating of economizer tubes
d) Reheat the gas coming out of economizer
Explanation: Function of air preheater is to recover the heat of a portion of exhaust flue gases before the flue gases enter the chimney. It is places along the passage of the exhaust flue gases in between the economizer and the chimney.
12. Tubular air preheater of a boiler is also called as _________
a) recuperative air preheater
b) elliptical air preheater
c) ovoid air preheater
d) squarish air preheater
Explanation: Tubular air preheater is also called as recuperative air preheater. This type of air preheater is composed of steel tubes through which hot flue gases flow. Air is made to circulate over these steel tubes and thus gains heat.
13. What does regenerative air preheater consists of?
Explanation: This type of air preheater consists of a rotor which turns about 2 to 3rpm. The rotor is filled with thin corrugated metal elements. Hot gases pass through one half of the heater and air through the other half. As the rotor turns, the heat storage elements transfer the heat absorbed from the hot gases to the incoming air.
14. What is the function of the feed water pump of a boiler?
a) Pump water at high pressure
b) To pump water at lower pressure
c) To pull back the water from boiler
d) To convert steam into water after the boiler process
Explanation: Function of feed water pump is to pump water at high pressure to the water space of the boiler drum. There are many types of feed pumps, in which they are mainly classified into rotary and reciprocating pumps.
15. Rotary pumps are driven by _________
a) electric motors
c) diesel engines
d) biogas fuel
Explanation: Rotary pumps are driven by electric motors. Water is pumped due to rotary action of the impeller. Rotary pumps are invented by Charles C Barnes. It is a positive displacement pump. The efficiency of these pumps depends on the percentage of slip to the total quantity displaced.
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