Book 2: 6-27 - "Air Compression"

Question 1

A rotary lobe compressor has _____ within a casing.
Select one:

A. Two figure-eight shaped impellers revolving in the same direction

B. Two figure-eight shaped impellers revolving in opposite directions

C. Two figure-six shaped impellers revolving in opposite directions

D. One figure-eight shaped impeller

E. Two figure-six shaped impellers revolving in the same direction

Answer 1

B. Two figure-eight shaped impellers revolving in opposite directions

Question 2

The temperature very exceptional circumstances may be about _____ near the end of the compression stroke.
Select one:

A. 150°C (302°F)

B. 175°C (347°F)

C. 90°C (194°F)

D. 225°C (437°F)

E. 75°C (167°F)

Answer 2

D. 225°C (437°F)

Question 3

One of the categories of air compressors is the _____ type.
Select one:

A. Reciprocating

B. Positive displacement

C. Rotary screw

D. Centrifugal

E. Rotary lobe

Answer 3

B. Positive displacement

Question 4

A disadvantage of the rotary screw compressor is:
Select one:

A. They can be classed as “oil-free” if so designed

B. Vibration free operation

C. Smooth air flow

D. No suction or discharge valves are required

E. It is less efficient than a reciprocating type

Answer 4

E. It is less efficient than a reciprocating type

Question 5

The crosshead in a double-acting compressor serves as a bearing and is the point where:
Select one:

A. Linear motion stops

B. All motion stops

C. Circular motion stops

D. Circular motion becomes linear motion

E. Circular motion becomes angular motion

Answer 5

D. Circular motion becomes linear motion

Question 6

Some uses of compressed air in buildings include all of the following except:
Select one:

A. Extinguishing fires in buildings.

B. Mixing or agitating in water treatment processes

C. Atomizing fuel oil

D. Operating building environmental control systems

E. Starting engines

Answer 6

A. Extinguishing fires in buildings.

Question 7

Generally, positive displacement compressors favor:
Select one:

A. Pressure

B. Speed

C. Time

D. Volume

E. Temperature

Answer 7

A. Pressure

Question 8

Lubricating oil is necessary in an air compressor to perform the following functions except:
Select one:

A. To reduce friction

B. To provide seating

C. To prevent wear

D. To reduce corrosion

E. To remove heat

Answer 8

B. To provide seating

Question 9

A piston rod in a double-acting compressor has:
Select one:

A. Linear travel at one end and angular at the other

B. Linear travel at both ends

C. Angular travel at one end only

D. Linear travel at one end only

E. Angular travel at both ends

Answer 9

B. Linear travel at both ends

Question 10

One of the categories of air compressors is the _____ type.
Select one:

A. Rotary lobe

B. Dynamic

C. Centrifugal

D. Reciprocating

E. Rotary screw

Answer 10

B. Dynamic

Question 11

One of the disadvantages of using compressed air to drive tools and other machinery over the use of electricity or steam is:
Select one:

A. Compressed air machines cannot be damaged by overloading

B. Air driven hand tools do not become hot after extensive use

C. Air driven hand tools do not create a shock hazard

D. Compressed air tools are that they are usually more expensive

E. Air driven hand tools are lighter in weight

Answer 11

D. Compressed air tools are that they are usually more expensive

Question 12

External lubrication of the compressor refers to lubrication of all of the following except the:
Select one:

A. Crankshaft bearings

B. Rotor shaft bearings on rotary and dynamic compressors

C. Cylinder walls

D. Connecting rod bearings

E. Crossheads on reciprocating compressors

Answer 12

C. Cylinder walls

Question 13

Generally, dynamic compressors favor:
Select one:

A. Time

B. Speed

C. Temperature

D. Volume

E. Pressure

Answer 13

D. Volume

Question 14

Which of the following statements about centrifugal compressor advantages is incorrect?
Select one:

A. They are commonly used for large volume applications

B. They are commonly used for low-pressure applications

C. They are of simple and rugged construction

D. They have low maintenance requirements

E. Their efficiency is higher than the positive displacement type

Answer 14

E. Their efficiency is higher than the positive displacement type

Question 15

Internal lubrication of the compressor refers to lubrication of all of the following except the:
Select one:

A. Crankshaft bearings

B. Casings of the applicable compressor

C. Pistons

D. Cylinder walls

E. Vanes

Answer 15

A. Crankshaft bearings

Question 16

The single-stage rotary screw compressor will develop discharge pressures to about:
Select one:

A. 400 kPa (58 psi)

B. 100 kPa (14.5 psi)

C. 500 kPa (72.5 psi)

D. 600 kPa (87 psi)

E. 200 kPa (29 psi)

Answer 16

A. 400 kPa (58 psi)

Question 17

An example of a dynamic compressor is the _____ compressor.
Select one:

A. Rotary screw

B. Reciprocating

C. Centrifugal

D. Rotary lobe

E. Sliding vane

Answer 17

A. Rotary screw

Question 18

The sliding vane compressor operates at speeds of up to:
Select one:

A. 3000 r/min

B. 4000 r/min

C. 1000 r/min

D. 2000 r/min

E. 5000 r/min

Answer 18

A. 3000 r/min

Question 19

A pilot type of air compressor unloader may operate in all except one of the following ways:
Select one:

A. It may open a bleed valve to atmosphere and simply dump to atmosphere if the compressor is a large dynamic type

B. It may close the compressor intake line if compressor is a dynamic type

C. It may open a by-pass valve in the discharge back to the compressor intake

D. It may open a by-pass valve in the intake back to the compressor discharge

E. It may hold the cylinder inlet valves open if the compressor is a reciprocating type

Answer 19

D. It may open a by-pass valve in the intake back to the compressor discharge

Question 20

Since the compressors two rotating lobes do not make contact with each other:
Select one:

A. Compression is very high

B. Efficiency is quite low due to blow-by

C. Very high rotational speeds are required

D. Oil is required to complete the seal for compression

E. Lubrication is not required and the unit is termed “oil free”

Answer 20

E. Lubrication is not required and the unit is termed “oil free”