This set of Thermal Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Boiler Mountings – 1”.
1. Which of the following statements regarding boiler mountings is TRUE?
a) They ensure safe operation of the boiler
b) They are installed to increase efficiency of the boiler
c) Economizer, superheater and feed pumps are boiler mountings
d) Water level indicator is not a boiler mounting
Explanation: Boiler mountings are installed for safety of a boiler. Economizer, superheater and feed pumps are not boiler mountings, they are boiler accessories. Examples of boiler mountings are water level indicator, steam stop valve, man hole, pressure gauge, safety valve etc.
2. Water level indicator _____
a) indicates the amount of steam in the boiler
b) indicates the amount of water in the boiler
c) indicates the amount of water converted to steam
d) indicates the amount of steam left in the boiler
Explanation: Water level indicator constantly indicates the level of water inside the boiler. The water level in a boiler must not fall below a certain safe-level. If the level of water inside the boiler happens to fall below safe-level, crack and leak can occur.
3. What is the purpose of guard glass in a glass-tube water level indicator?
a) It protects the attendant, if water starts leaking
b) It protects the water gauge, if steam pressure increases the design pressure
c) It protects the attendant, if boiler cracks
d) It protects the attendant, if the gauge glass breaks
Explanation: The guard glass is tough. It doesn’t give shards on breaking. Guard glass covers the gauge glass. If due to sudden rush of water and steam the gauge glass breaks, the guard glass protects the attendant from getting hurt.
4. What is the purpose of pressure gauge?
a) It measures the pressure exerted on the boiler shell from outside
b) It measure the current atmospheric pressure
c) It measures pressure exerted inside the boiler shell
d) It measures hydrostatic pressure of water at the bottom of the boiler shell
Explanation: Pressure gauge measures the pressure exerted inside the boiler shell. Normally, it is manufactured to indicate pressure upto double the maximum working pressure. It measures gauge pressure i.e. pressure above atmospheric pressure.
5. Which of the following statements about compound pressure gauge is TRUE?
a) It measure the hydrostatic pressure exerted by water at the bottom surface
b) It can measure pressures above and below atmospheric pressure on the same dial
c) It is installed at the bottom of the boiler shell
d) It measures absolute pressure
Explanation: A compound pressure gauge is designed such that it can measure pressures above and below atmospheric pressure. It is a pressure gauge, hence mounted on the front top of the shell.
6. The syphon tube in the Bourdon pressure gauge (single tube) is filled with _____
b) turpentine oil
c) mineral water
d) condensed water
Explanation: Syphon tube is an integral part of the Bourdon pressure gauge. The syphon tube is completely filled with condensed water. Steam pressurizes the water in the syphon from one side and the water is forced into the elliptical tube.
7. Which of the following statements about Bourdon pressure gauge is FALSE?
a) Double-tube Bourdon gauge is more rigid than the single tube
b) Double-tube Bourdon gauge is more suitable for portable boilers
c) It measures the gauge pressure
d) The movement of the free end of the elliptical tube is proportional to the internal pressure of the boiler
Explanation: The movement of the free end of the elliptical tube is proportional to the difference between internal and external pressure in the tube. Since the external pressure is atmospheric the free end measures gauge pressure.
8. The function of a safety valve is _____
a) to release the excess steam when the steam pressure exceeds the rated pressure
b) to extinguish fire when the temperature reaches impermissible value
c) to release the excess water
d) it cuts off the water supply when water level reaches its maximum limit
Explanation: A safety valve releases excess steam if the steam pressure exceeds the rated pressure. The safety valve automatically opens when the pressure exceeds the limit and closes automatically when the pressure reduces to acceptable value.
9. Which of the following is NOT a type of safety valve?
a) Dead weight safety valve
b) Lever safety valve
c) Spring loaded safety valve
d) High water and low steam safety valve
Explanation: The types of safety valve are – high steam and low water safety valve, dead weight safety valve, spring loaded safety valve and lever safety valve. The purpose of safety valve is to release excess steam when the steam pressure exceeds the design pressure.
10. Which of the following statements about safety valves is FALSE?
a) It is usually mounted on the top of the shell
b) It releases the steam if the steam pressure exceeds the rated pressure
c) Dead weight safety valve is a type of safety valve
d) An attendant is required to operate the valve
Explanation: The safety valve automatically opens once the steam pressure exceeds the rated pressure and it automatically closes when the pressure drops down to permissible value. Safety valves are usually mounted on top of the shell.
11. Which of the following statements about dead weight safety valve is FALSE?
a) It is unsuitable for Locomotive boilers
b) It is suitable for low pressure and low capacity boilers
c) To lift the valve the inside pressure must overcome the valve weight and the dead weights
d) It is suitable for high pressure boilers
Explanation: Large amount of weights will be required to balance high pressure; therefore, it is not suitable for high pressure boilers. It is used in low pressure and low capacity boilers. It cannot bear vibrations and movements, hence not suitable for locomotive boilers.
12. Spring loaded safety valve is suitable for locomotive and marine engines.
Explanation: Spring loaded safety valve unlike dead weight safety valve and lever safety valve is unaffected by vibrations and movements in vertical directions. It is therefore suitable for locomotive and marine engines.
13. Which of the following statements about high steam and low water safety valve is FALSE?
a) It can be used on portable boilers
b) Steam escapes out when water level falls below a certain level
c) Steam is released when its pressure exceeds a certain pressure
d) It is generally used in Lancashire and Cornish boiler
Explanation: High steam and low water safety valve is not suitable for locomotive and marine engines. It is designed such that when the steam pressure exceeds a certain pressure limit or when the water level falls below a certain limit the valve opens and the steam is released to atmosphere.
14. In water level indicator, the glass tube that indicated the water level is called _____
a) measurement tube
b) guard glass tube
c) gauge glass tube
d) level tube
Explanation: In a water level Indicator the glass tube that indicates the water level is called gauge glass tube. It is very hard. It produces shards when it breaks which could hurt the attendant. Therefore, the gauge glass is completely covered by guard glass which does not produce shards after breaking.
15. A Steam separator is a boiler mounting.
Explanation: A steam separator comes under boiler accessories and not under boiler mountings. Boiler mountings include – safety valves, water level indicators, pressure gauges, steam stop valve, feed check valve etc.
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