- 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
d. some type of unloading device
- 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
a. driver
- 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
b. the air demand is low and infrequently demanded
- 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
d. a driver that can be throttled
- A method of unloading a reciprocating compressor is to ________________________.
a. hold the discharge valve closed
b. hold the discharge valve open
c. place a check valve in the discharge line
d. hold the inlet valves in the open position
e. unloading a cylinder
d. hold the inlet valves in the open position
- 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
a. a spring loaded pilot valve
- 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
e. regulated
- 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
e. variable speed
- 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
a. unloading
- To prevent surging, the capacity of the compressor must not be allowed to fall below the ___________.
a. surge limit
b. maximum volume
c. rated point
d. rated pressure
e. set point
a. surge limit
- 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
d. open a discharge line blow-off valve to atmosphere
- 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 value s.
a. 2, 4
b. 1, 4
c. 1, 2, 3
d. 1, 2, 3, 4
e. None of the above
c. 1, 2, 3
- A good method of drying air before it goes into the receiver is to ____________.
a. heat it
b. pressurize it
c. cool it
d. increase the velocity
e. decrease the velocity
c. cool it
- Air compressor inter and after coolers may be______________.
a. water or air cooled
b. oil or hydrogen cooled
c. teflon lubricated
d. electrically heated
e. freon refrigerant cooled
a. water or air cooled
- The aftercooler is used in an air compression system to _____________________.
a. cool the air after the first stage of compression
b. cool the lubricating oil of large axial compressors
c. cool the air after it leaves the receiver
d. cool the air after the last stage of compression
e. cool the air before being compressed
d. cool the air after the last stage of compression
- It is advisable that ________ is fitted between the aftercooler and air receiver.
a. a gauge glass
b. pressure gauge
c. a moisture separator
d. an air filter
e. temperature gauge
c. a moisture separator
- In a compressed air system, if water vapour is not removed from the air then it may collect in pipelines and cause:
1) Increase in pressure 2) Water hammer 3) Gurgling noise 4) Damage from freezing
a. 1, 3
b. 3
c. 1, 4
d. 2, 4
e. 1, 2, 3
d. 2, 4
- If there is a shut-off valve between the aftercooler and the receiver, the aftercooler must also be fitted with a ________.
a. safety valve
b. pressure gauge
c. thermometer
d. fusible plug
e. vacuum breaker
a. safety valve
- An air compressor will require more power to compress the air if an intercooler is implemented.
a. True
b. False
b. False
- Effective intercooling will reduce weakening of parts due to high temperatures, and reduce possibility of ___________.
a. compressor explosions
b. water hammer
c. compressor implosions
d. compressor leaks
e. corrosion
b. water hammer
- Aftercoolers should be fitted with _______________.
a. pressure gauges
b. thermometers
c. possibly a safety valve
d. water separator
e. All of the above
e. All of the above
- The presence of ________ in the air may later result in the compressed air piping being subjected to water hammer.
a. oil
b. corrosion
c. dirt particles
d. nitrogen
e. moisture
e. moisture
- Detrimental effects of moisture in an air compression system are:
1) It may cause corrosion 2) It may cause water hammer 3) It will reduce compressor capacity 4) It will cool the air below the dew point 5) It may wash carbon off the valves 6) It may freeze in the air lines
a. 1, 2, 3, 6
b. 3, 4, 5, 6
c. 1, 2, 3, 4, 5, 6
d. 2, 4, 5, 6
e. 1, 2, 3, 4, 5
a. 1, 2, 3, 6
- The inlet pipe to the compressor must be _________________.
a. larger that the compressor intake
b. twice as large as the compressor intake
c. smaller than the compressor intake
d. at least as large as the compressor intake
e. at least as large as the compressor discharge
d. at least as large as the compressor intake
