MCQs on Hydraulic Actuating Systems – Air Compressors

1 - Question

What is the function of the air compressor?
a) Decreases the pressure of air
b) Increases the pressure of air
c) Removes dust particles
d) Adds lubricating oil
View Answer Answer: b
Explanation: Air compressor is a machine which draws the air from the atmosphere, compresses it to increase the pressure and delivers the high pressure compressed air to the air receiver tank. The other options mentioned are the functions of the air filter and air lubricator respectively.



2 - Question

Which among the following are the applications of air compressors?
a) Supercharging of IC engines
b) Agriculture
c) Railways
d) Aerospace
View Answer Answer: a
Explanation: Some of the applications of air compressors are supercharging IC engines, Gas turbines and jet engines, Packing machines, Hand tools, CNC machines etc. and in spray paintings. The other options mentioned are the applications of Hydraulic systems.



3 - Question

The capacity of the compressor is specified by free air delivery.
a) True
b) False
View Answer Answer: a
Explanation: Capacity of the compressor is specified by free air delivery. Free air delivery is defined as the volume of the air drawn by the compressor per unit time. After compression, the volume reduces as per pressure. It is a factor that should be considered during the selection of air compressor. advertisement



4 - Question

Which among the following are not the accurate selection criteria for air compressors?
a) Free air delivery
b) Air receiver capacity
c) Power supply
d) Speed
View Answer Answer: d
Explanation: Speed is not the accurate selection criteria for the selection of air compressors. The selection criteria of the air compressors include factors such as average air consumption of the system, free air delivery, Air receiver capacity, Power supply and components and accessories.



5 - Question

What is the normal pressure at which the compressed air is stored?
a) 30 bar
b) 40 bar
c) 10 bar
d) 100 bar
View Answer Answer: c
Explanation: Several types of air compressors are used for generating the compressed air for pneumatic systems. The air compressor draws the air from the atmosphere, compresses it and delivers it to the air receiver tank, where it is stored under pressure. Normally compressed air is stored at a maximum of 10 bar pressure in the air receiver tank.



6 - Question

The compressed air is very costly.
a) True
b) False
View Answer Answer: a
Explanation: Air is freely available. Compressed air is very costly due to various power losses during compression. The main loss is due to the heat of compression. During compression, the pressure increases, the volume reduces and the temperature increases.



7 - Question

Which among the following leads to conserving of energy?
a) Conserving compressed air
b) Wasting the compressed air
c) Using compressed air for Cleaning and Washing
d) Allowing leakages of compressed air
View Answer Answer: a
Explanation: Conserving the compressed air leads to conserving energy. Employees should be trained well to conserve compressed air in the industry. If leakages of air are found anywhere, immediately it should be stopped. Use of compressed air for cleaning anything should be avoided.



8 - Question

What is the use of Intake air filters?
a) To reduce the temperature of the air
b) Used as storage and smoothened
c) To prevent dust from entering the compressor
d) To remove the traces of moisture
View Answer Answer: c
Explanation: Intake air filters are used to prevent dust from entering the compressor. Dust causes sticking valves, scoured cylinders, excessive wear etc. The other functions mentioned in the options are done using Interstage coolers, air dryers and air receivers respectively.



9 - Question

What is the function of Interstage coolers?
a) To reduce the temperature of the air
b) Used as storage and smoothened
c) To prevent dust from entering the compressor
d) To remove the traces of moisture
View Answer Answer: a
Explanation: The main function of Interstage coolers are to reduce the temperature of the air before it enters the next stage to reduce the work of compression and increase efficiency. They are normally water cooled. The other functions mentioned in the options are done using intake air filters, air dryers and air receivers respectively.



10 - Question

The removal of moisture from the compressed air is done using ____
a) receivers
b) moisture drain traps
c) air dryers
d) interstage coolers
View Answer Answer: b
Explanation: The removal of moisture from the compressed air is done using Moisture drain traps. These traps resemble steam traps. Interstage coolers are used to reduce the temperature of the air before it enters the next stage. The remaining traces of moisture after cooler are removed using air dryers. Air receivers are provided as storage and smoothening the pulsating air output.

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