POWER ENGINEERING 3B2 - CHAPTER
9 EXAM QUESTIONS AND ANSWERS.
VERIFIED 2026.
A compressor driven by a constant speed driver has its output varied by
_____________________________.
a. a stop and start switch
b. a solenoid valve
c. a mercury switch
d. some type of unloading device
e. a safety relief valve - ANS D
A variable speed control regulates the speed of the _________ from air receiver pressure
monitoring.
a. driver
b. compressor crankshaft
c. compressor impellers
d. compressor blades
e. coupling - ANS A
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
,The stop and start system is best employed where ____________________________.
a. the air demand is constant
b. the air demand is low and infrequently demanded
c. a large AC motor is used as the driver
d. a diesel engine is used as the driver
e. variable speed and start, stop - ANS B
In the variable speed control method the compressor output is regulated by
_______________________.
a. adjustment of clearance pockets
b. a rheostat
c. a safety relief valve
d. a driver that can be throttled
e. only small receivers are available - ANS D
The item used to activate the inlet air unloader is ________________.
a. a spring loaded pilot valve
b. a torsion bar
c. a bleed-off valve
d. a compressor flywheel
e. None of the above - ANS A
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
,The flow of air from a compressor must be _______ to suit load requirements and to maintain
constant pressure in the system.
a. increased
b. decreased
c. dampened
d. interrupted
e. regulated - ANS E
The ________ control method can be used when the compressor is driven by a steam engine, a
turbine, or an internal combustion engine.
a. constant speed
b. start and stop
c. dual
d. start and stop in conjunction with constant speed
e. variable speed - ANS E
Output from a compressor using the constant speed control method must use some type of
______________ device.
a. unloading
b. uploading
c. down loading
d. start stop device
e. variable speed - ANS A
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, One method to prevent surging in dynamic compressors is to ___________________.
a. sue variable frequency drive
b. use vanes
c. install a recirculation line
d. open a discharge line blow-off valve to atmosphere
e. use a safety valve - ANS D
The reasons for cooling the air in an air compression system is to:
1) Remove water vapor and oil vapor from the air.
2) Make cylinder lubrication more effective.
3) Decrease the amount of power required to compress the air.
4) Remove fixed carbon from the valves.
a. 2, 4
b. 1, 4
c. 1, 2, 3
d. 1, 2, 3, 4
e. None of the above - ANS C
A good method of drying air before it goes into the receiver is to ____________.
a. heat it
b. pressurize it
c. cool it
4 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
9 EXAM QUESTIONS AND ANSWERS.
VERIFIED 2026.
A compressor driven by a constant speed driver has its output varied by
_____________________________.
a. a stop and start switch
b. a solenoid valve
c. a mercury switch
d. some type of unloading device
e. a safety relief valve - ANS D
A variable speed control regulates the speed of the _________ from air receiver pressure
monitoring.
a. driver
b. compressor crankshaft
c. compressor impellers
d. compressor blades
e. coupling - ANS A
1 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
,The stop and start system is best employed where ____________________________.
a. the air demand is constant
b. the air demand is low and infrequently demanded
c. a large AC motor is used as the driver
d. a diesel engine is used as the driver
e. variable speed and start, stop - ANS B
In the variable speed control method the compressor output is regulated by
_______________________.
a. adjustment of clearance pockets
b. a rheostat
c. a safety relief valve
d. a driver that can be throttled
e. only small receivers are available - ANS D
The item used to activate the inlet air unloader is ________________.
a. a spring loaded pilot valve
b. a torsion bar
c. a bleed-off valve
d. a compressor flywheel
e. None of the above - ANS A
2 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
,The flow of air from a compressor must be _______ to suit load requirements and to maintain
constant pressure in the system.
a. increased
b. decreased
c. dampened
d. interrupted
e. regulated - ANS E
The ________ control method can be used when the compressor is driven by a steam engine, a
turbine, or an internal combustion engine.
a. constant speed
b. start and stop
c. dual
d. start and stop in conjunction with constant speed
e. variable speed - ANS E
Output from a compressor using the constant speed control method must use some type of
______________ device.
a. unloading
b. uploading
c. down loading
d. start stop device
e. variable speed - ANS A
3 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
, One method to prevent surging in dynamic compressors is to ___________________.
a. sue variable frequency drive
b. use vanes
c. install a recirculation line
d. open a discharge line blow-off valve to atmosphere
e. use a safety valve - ANS D
The reasons for cooling the air in an air compression system is to:
1) Remove water vapor and oil vapor from the air.
2) Make cylinder lubrication more effective.
3) Decrease the amount of power required to compress the air.
4) Remove fixed carbon from the valves.
a. 2, 4
b. 1, 4
c. 1, 2, 3
d. 1, 2, 3, 4
e. None of the above - ANS C
A good method of drying air before it goes into the receiver is to ____________.
a. heat it
b. pressurize it
c. cool it
4 @COPYRIGHT 2025/2026 ALLRIGHTS RESERVED.
