Ch. 8

Question 1

527. __________ of a compressor is known as free air delivered or free air capacity.

a. Capacity
b. Displacement
c. Absolute pressure
d. Efficiency
e. Pressure ratio

Answer 1

a. Capacity

Question 2

528. Reciprocating compressors are suitable for_________________.

a. low pressure service
b. only high pressure service
c. all ranges of pressure
d. single stage only
e. None of the above

Answer 2

c. all ranges of pressure

Question 3

529. Four ways of dividing reciprocating compressors into types are:

1)     Single or double acting
2)     Method of compression
3)     Number of impellers
4)     Speed of prime mover
5)     Method of drive
6)     Cylinder arrangement 

a. 3, 4, 5, 6
b. 1, 2, 5, 6
c. 1, 3, 5, 6
d. 2, 3, 4, 6
e. 1, 3, 4, 5

Answer 3

b. 1, 2, 5, 6

Question 4

530. ________ positive displacement compressors require intake and discharge valves.

a. Rotary
b. Centrifugal
c. Sliding vanes
d. Rotary lob
e. Reciprocating

Answer 4

e. Reciprocating

Question 5

531. A reciprocating compressor is suited for all ranges of ______ .

a. discharge air temperatures
b. speed
c. oil lubrication
d. cooling water temperatures
e. pressures

Answer 5

e. pressures

Question 6

532. Reciprocating air compressors are best suited to _____________________.

a. high speed, low volume applications
b. low pressure, high volume applications
c. low pressure, low volume applications
d. high pressure, moderate volume applications
e. high speed, high volume applications

Answer 6

d. high pressure, moderate volume applications

Question 7

533. Cylinder arrangements of reciprocating air compressors may be:

1)     Vertical or horizontal
2)     Rotary or simplex
3)     The V or Y type
4)     An angle type
5)     Twin impeller type 

a. 1, 3, 4
b. 1, 3, 5
c. 2, 4, 5
d. 1, 2, 3
e. 2, 3, 5

Answer 7

a. 1, 3, 4

Question 8

534. In a multistage reciprocating compressor the highest pressure stages may be_______________________.

a. remote controlled
b. poppet valve regulated
c. double lobe
d. single acting
e. free piston

Answer 8

d. single acting

Question 9

535. A free piston air compressor _____________________________.

a. has a spare or free piston for air compression
b. uses one steam cylinder to drive two compression pistons
c. has a common intake and discharge valve system
d. has a cushion cylinder that acts as a flywheel
e. has two crankshaft

Answer 9

d. has a cushion cylinder that acts as a flywheel

Question 10

536. A double acting reciprocating air compressor __________________.

a. must have at least two pistons
b. receives and discharges air at both ends of the cylinder
c. increases the pressure twice from inlet pressure value
d. has one compression stroke for every crankshaft revolution
e. None of the above

Answer 10

b. receives and discharges air at both ends of the cylinder

Question 11

537. In multistage compression, the high-pressure cylinders are __________ because the volume is __________ and the pressure is __________than the lower pressure stages.

1)     smaller
2)     larger
3)     higher
4)     lower
5)     more
6)     less 

a. 2, 5, 4
b. 1, 5, 4
c. 2, 4, 6
d. 2, 5, 6
e. 1, 6, 3

Answer 11

e. 1, 6, 3

Question 12

538. _______ and carbon rings can be used in reciprocating air compressors to deliver oil free air.

a. Brass
b. Aluminum
c. Titanium
d. Ceramic
e. Teflon

Answer 12

e. Teflon

Question 13

539. Oil free air may be provided by reciprocating air compressors by _______________________________.

a. use of a porous filter
b. use of an oil filter
c. nylon and brass piston rings
d. carbon or Teflon piston rings
e. use of an intercooler

Answer 13

d. carbon or Teflon piston rings

Question 14

540. The prime purpose of water cooling or air cooling of air compressors is to ______________________________.

a. cool the air
b. help increase moisture and volume of the air
c. keep the cylinder at a reasonable temperature
d. prevent fire from occurring in the receiver
e. prevent operator injury

Answer 14

c. keep the cylinder at a reasonable temperature

Question 15

541. Air compressor pistons are constructed of:

1)     Steel
2)     Cast iron
3)     Brass
4)     Aluminum
5)     Copper alloy 

a. 1
b. 1, 2
c. 3, 4, 5
d. 1, 2, 4
e. 2, 3, 4, 5

Answer 15

d. 1, 2, 4

Question 16

542. Water cooling by water jacketing of air compressor cylinders is preferred over air cooling because _________________________.

a. the construction of the compressor is cheaper than the finned type
b. there is less piping involved
c. the construction is fairly simple
d. more efficient cooling is obtained
e. the air temperature can not be controlled

Answer 16

d. more efficient cooling is obtained

Question 17

543. Reciprocating compressor valves are usually found in two common forms ____________________________.

a. plate disc and channel type
b. composition and rubber
c. copper and aluminum
d. angle and inverted
e. ribbed and push rods

Answer 17

a. plate disc and channel type

Question 18

544. Compressor valves are usually automatic and open and close by _________________________________.

a. action of a poppet valve
b. movement of the piston covering or uncovering ports
c. operation of an air solenoid valve
d. a pressure difference
e. a camshaft

Answer 18

d. a pressure difference

Question 19

545. If _____________ is used then the cylinder is constructed with integral cast fins, which provide increased radiating area.

a. water cooling
b. water jacket
c. glycol cooling
d. sliding vane compressor
e. air cooling

Answer 19

e. air cooling

Question 20

546. Compressor connecting rods are constructed of _____________.

a. cast iron
b. stainless steel
c. forged steel
d. black iron
e. brass

Answer 20

c. forged steel

Question 21

547. A reciprocating compressor can deliver oil-free air if it ________________________________ .

a. uses an oil separator at the compressor discharge
b. uses an oil filter before the compressor inlet
c. implements a charcoal filter at the compressor discharge
d. implements carbon or Teflon piston rings
e. uses an intercooler to increase the oil viscosity

Answer 21

d. implements carbon or Teflon piston rings

Question 22

548. Lubricating oil is necessary in an air compressor in order to perform the following functions:

1)     Provide sealing
2)     Remove heat
3)     Reduce friction
4)     Eliminate water cooling
5)     Reduce corrosion
6)     Remove carbon
7)     Prevent wear 

a. 1, 2, 3, 4, 5
b. 1, 2, 3, 4, 5, 6, 7
c. 1, 3, 4, 6
d. 1, 2, 3, 5, 7
e. 1, 2, 4, 5

Answer 22

d. 1, 2, 3, 5, 7

Question 23

549. Internal lubrication of air compressors refers to:

1)     The crankcase and crankshaft
2)     Cylinder walls and pistons
3)     Vanes and casing walls of some compressors
4)     Impellers of a centrifugal compressor 

a. 2, 3
b. 1, 3, 4
c. 3, 4
d. 1, 4
e. 1, 2, 3

Answer 23

a. 2, 3

Question 24

550. Single-acting compressors having the bottom of the cylinder open to the crankcase will have lubrication provided by _________________________.

a. a pressure lubricator
b. a force fed oil pump
c. a splash system
d. an oil ring
e. None of the above

Answer 24

c. a splash system

Question 25

551. Compressor lubrication may be divided into two main sections __________ lubrication and __________ lubrication. 1) peripheral 2) internal 3) splash 4) external 5) pressure a. 1, 2 b. 3, 5 c. 3, 4, 5 d. 2, 3, 4 e. 2, 4

Answer 25

e. 2, 4

Question 26

552. A kind of rotary compressor is _________________. a. a two lobe b. a cross - compound double cylinder c. sliding piston d. axial e. All of the above

Answer 26

a. a two lobe

Question 27

553. The operating speed of a typical two-stage sliding vane compressor ranges up to _____________. a. 250 rpm b. 5000 rpm c. 1800 rpm d. 3000 rpm e. 2000 rpm

Answer 27

d. 3000 rpm

Question 28

554. An important advantage of a sliding vane compressor is that it ___________________________________. a. does not require internal lubrication b. has a high starting torque c. does not require inlet or discharge valves d. requires light nylon timing gears e. does not require a prime mover

Answer 28

c. does not require inlet or discharge valves

Question 29

555. In a rotary lobe compressor one lobe is directly driven by the driving mechanism while the other lobe is driven by __________________________. a. intermeshing with the driven lobe b. a reduction gear c. means of timing gears d. speed increasing gears e. a belt

Answer 29

c. means of timing gears

Question 30

556. The impellers of a _________ compressor maintain their relative positions with each other by the use of timing gears. a. siding vane b. free piston c. axial flow d. angle types e. lobe type rotary

Answer 30

e. lobe type rotary

Question 31

557. In the ________ compressor, the male rotor has convex lobes and the female rotor has concave flutes. a. lobe type rotary b. axial flow c. sliding vanes d. rotary screw e. free piston

Answer 31

d. rotary screw

Question 32

558. The lobe type compressor runs at speeds up to about _________ Rev/min. a. 1550 b. 1600 c. 1650 d. 1700 e. 1750

Answer 32

e. 1750

Question 33

559. The rotary screw compressor usually has the _____________________. a. male lobe driven b. male flute driven c. female flute driven d. female lobe driven e. female and male driven

Answer 33

a. male lobe driven

Question 34

560. Rotary lobe compressors have their elements ________________________ . a. lubricated by graphite b. enclosed by an aluminum casing c. as spring loaded vanes d. revolving in opposite directions e. lubricated by oil

Answer 34

d. revolving in opposite directions

Question 35

561. Three different designs of rotary compressors are: 1) Sliding vane 2) Rotary screw 3) Axial flow 4) Volute centrifugal 5) Rotary lobe 6) Diffuser vane centrifugal a. 2, 4, 6 b. 1, 2, 3 c. 3, 4, 6 d. 1, 3, 5 e. 1, 2, 5

Answer 35

e. 1, 2, 5

Question 36

562. Centrifugal compressors are commonly used for ___________________. a. low volume, high pressure applications b. low speed, high pressure applications c. high humidity, low volume applications d. large volume, low pressure applications e. large volume, low speed

Answer 36

d. large volume, low pressure applications

Question 37

563. Adjustable diffuser vanes on centrifugal air compressors are implemented to ______________________________. a. change the operating characteristics of the compressor b. prevent back or reverse flow of air c. remove foreign particles from the air d. reduce the amount of air entering the compressor e. change the direction of the air flow to remove moisture

Answer 37

a. change the operating characteristics of the compressor

Question 38

564. Centrifugal air compressors are used for __________________ pressure applications. a. changing b. low volume, high pressure c. low volume, low pressure d. high volume, high pressure e. high volume, low pressue

Answer 38

e. high volume, low pressure

Question 39

565. For changing the air ____________ in centrifugal air compressors to ______________, volute casings and diffuser vanes are implemented. 1) pressure 2) volume 3) velocity 4) temperature a. 1,2 b. 2,4 c. 4,1 d. 3,1 e. 4, 2

Answer 39

d. 3,1

Question 40

566. A centrifugal air compressor may have ________ for multi-staging. a. two or more pistons b. two or more impellers on separate shaft c. two or more compressors d. two or more diffuser vanes e. two or more impellers on same shaft

Answer 40

e. two or more impellers on same shaft

Question 41

567. Each pair of moving and fixed blades in an axial air compressor constitutes a/an _______________. a. pressure drop b. temperature decrease c. program of air d. stage e. obstacle

Answer 41

d. stage

Question 42

568. Axial flow compressor advantages are similar to those of centrifugal air compressors, they have an added advantage of ______________________. a. being lower in cost b. being a shorter machine c. being corrosion and erosion free d. being approximately 10% more efficient e. solid forged rotor

Answer 42

d. being approximately 10% more efficient

Question 43

569. In axial air compressors, the pressure rise per stage is ____________ therefore, for high pressures ____________ stages are required. 1) low 2) high 3) single 4) multi a. 1, 3 b. 1, 4 c. 2, 3 d. 2, 4 e. 2, 1

Answer 43

b. 1, 4

Question 44

570. Axial flow compressor blades are subject to greater ________ and ________ than there is in a centrifugal compressor. 1) fouling 2) erosion 3) corrosion 4) cleaning a. 1, 3 b. 1, 4 c. 2, 1 d. 3, 4 e. 2, 3

Answer 44

e. 2, 3

Question 45

571. Axial flow compressors are _______________________. a. a dynamic type of compressor b. a single acting compressor c. a rotary type of compressor d. centrifugal compressor e. All of the above

Answer 45

a. a dynamic type of compressor

Question 46

572. ___________ on centrifugal air compressors are provided in order to control the amount of air flowing to the impeller and thus control the capacity of the unit. a. Adjustable inlet vanes b. Adjustable diffuser vanes c. Variable frequency drive d. Moving and fixed blades e. Dummy piston

Answer 46

a. Adjustable inlet vanes