“Surging” would be best described as which of the following?
A reversal of flow within the compressor
A sudden increase in air temperature
A sudden decrease in air temperature
A malfunction caused by the micro- processing unit
None of the above
Which of the following methods are used to control the load for rotary compressors?
Modulating inlet method
Start- stop Method
Load- unload method
Microprocessor- based control system
All of the above
Different methods used to control the load for a compressor include which of the following?
Inlet air unloader
Suction line unloading valve
Inlet air modulating valve
The free air capacities of axial flow compressors range form___m3 to___m3/min ?
1.5- 200
2.7-1500
2.8- 3700
1.9- 8000
What is the main advantage of an axial flow compressor?
Low maintenance
Higher efficiency
Trouble free service
Which of the following are advantages of the centrifugal compressor?
Low maintenance costs
Simple, rugged construction
Large volumes of oil free air
In a centrifugal compressor, energy is transferred from the impeller to the gas in the from of which of the following?
Velocity
Pressure
Velocity and pressure
In a rotary type screw compressor, the spiral valve is used to do which of the following?
Prevent dust and dirt from entering the compressor
Regulate the amount of air to the compressor
Open and close bypass ports in the stator
Which of the following devices removes any entrained moisture from the air leaving the compressor?
Fluid cooler
Air after cooler
After filter
Moisture separator
What is the main difference between the rotary compressor and the reciprocating compressor?
Difference in pressures
The difference in size
Use of inlet and discharge valves
The most common designs of a rotary compressor are which of the following? Sliding vane Rotary lobe Rotary screw Sliding lobe Rotary vane
Sliding Vane, Rotary Lobe, Rotary vane
Sliding Vane, Rotary Lobe, Rotary Screw
Sliding Vane, Sliding Lobe, Rotary vane
External lubrication involves the lubrication of all moving parts external to the cylinder or casing, such as? Piston Crosshead Crankshaft bearings Connecting rod bearings All of the above
Crosshead, crankshaft bearings, connecting rod bearings
crankshaft bearings, crosshead, piston
Lubricating oil is necessary in a compressor to serve which of the following purposes?
Reduce friction
Remove the heat produced by friction
Coat the surfaces and reduce corrosion
Provide a seal around the rings, vanes, and valves
If the cylinder of a reciprocating compressor is of oil free operation, the piston rings will be made of which of the following?
Stainless steel
Cast iron
Aluminum
Teflon or carbon
In a reciprocating compressor, air cooling has which of the following advantages over water cooling?
Simple construction
Less piping hazards
No freezing
In the _______________ compressor one of the cylinders acts as a cushion, while the other acts to compress the air?
Tandem
Free piston
Single stage
Double stage
Reciprocating compressors may be divided into which of the following?
Two stage
Single acting
Double acting
Which of the following statements is true?
Compression ratio is the ratio of discharge gauge pressure to the intake absolute pressure
A high compression ratio in a single cylinder results in a high volumetric efficiency and a high discharge temperature
Intercoolers are used to cool the discharged air before it is delivered to it’s point of use or the receiver
None of the above x
Intercoolers serve as a means to do which of the following?
Cool down the temperature of the air
Remove any entrained moisture in the air
Decrease the power required to compress the air in the following stage
