Unit Review Pumps & Air Compressors Comprehensive Self-Assessment

Question 1

1.	What size packing should be used if the stuffing box bore on a pump is 63.5 mm (2.5 in.) and the shaft diameter is 50.8 mm (2 in.)?
A.	12.7 mm (1/2 in)
B.	19.05 mm (3/4 in)
C.	9.525 mm (3/8 in)
D.	6.35 mm (1/4 in)
E.	4.76 mm (3/16 in)

Answer 1

D. 6.35 mm (1/4 in)

Question 2

2.	Lubricating oil is necessary in an air compressor to perform the following functions except:
A.	To prevent wear
B.	To reduce friction
C.	To remove heat
D.	To reduce corrosion
E.	To provide seating

Answer 2

E. To provide seating

Question 3

3. The centrifugal compressor consists of all of the following except:
   A. An impeller which rotates at high speed inside a volute-shaped casing
   B. Air is drawn in at the centre or eye of the impeller axially
   C. Air is discharged at the impeller periphery with low velocity due to centrifugal force
   D. The air then passes through the volute-shaped casing where a conversion of velocity into pressure takes place
   E. It is then discharged in a radial direction from the volute

Answer 3

C. Air is discharged at the impeller periphery with low velocity due to centrifugal force

Question 4

4.	The carbon residue test is used to determine the amount of carbon which oil will form when subjected to:
A.	Low temperatures
B.	High temperatures
C.	Low pressures
D.	High pressures
E.	High viscosity

Answer 4

B. High temperatures

Question 5

5.	A typical two-stage compressor might have an automatic shutdown device, which would operate in the event that any except one of the following conditions occurred:
A.	Low lubricating oil pressure
B.	Low discharge air temperature
C.	Low lubricating oil level
D.	Excessive vibration
E.	Cylinder lubricator stopped

Answer 5

B. Low discharge air temperature

Question 6

6.	If the moving surfaces of materials can be separated from each other by a/an \_\_\_\_\_ so that their high spots do not come in contact with each other wear will be reduced or eliminated.
A.	Oil
B.	Grease
C.	Lubricant
D.	Space
E.	Solid

Answer 6

C. Lubricant

Question 7

7.	An example of a dynamic compressor is the \_\_\_\_\_ compressor.
A.	Sliding vane
B.	Rotary lobe
C.	Rotary screw
D.	Reciprocating
E.	Axial flow

Answer 7

E. Axial flow

Question 8

8.	The sum of static suction lift plus static discharge head is the:
A.	Static suction lift
B.	Static discharge head
C.	Static suction head
D.	Total static head
E.	Total head

Answer 8

D. Total static head

Question 9

9.	The area of the centrifugal pump where the velocity of the liquid discharged from the impeller is lowered and converted to pressure is an area of increasing cross-sectional area called the:
A.	Impeller
B.	Diffuser
C.	Wear ring
D.	Volute
E.	Eye

Answer 9

D. Volute

Question 10

10.	Solid lubricants are suitable for use under conditions of:
A.	Low load
B.	Dampness
C.	Extreme (high or low) temperatures
D.	Dust
E.	Corrosive atmospheres

Answer 10

C. Extreme (high or low) temperatures

Question 11

11.	Reciprocating pumps are used for \_\_\_\_\_ applications.
A.	High volume, high-pressure
B.	Low volume, high-pressure
C.	Low volume, high-temperature
D.	High volume, Low-temperature
E.	Low volume, Low-pressure

Answer 11

B. Low volume, high-pressure

Question 12

12. Mechanical seals have all the following advantages over packing except that they:
    A. Are less expensive than packing
    B. Requires less maintenance
    C. Do not produce wear on shafts
    D. Reduce leakage to a minimum
    E. Can work under very high temperatures and pressures

Answer 12

A. Are less expensive than packing

Question 13

13. When the pump is located above the source of supply and a separate hand-operated priming pump is used the pump is primed in the following manner except:
    A. Close the discharge valve
    B. Close the priming valve
    C. The pump is operated exhausting air from the main pump casing and suction line
    D. Water issues from the priming pump discharge
    E. The priming pump valve is shut and the main pump is primed

Answer 13

B. Close the priming valve

Question 14

14.	A single-stage centrifugal compressor is one with a single impeller and may be able to compress atmospheric air to a pressure of about:
A.	500 kPa (72.5 psi)
B.	200 kPa (29 psi)
C.	100 kPa (14.5 psi)
D.	300 kPa (43.5 psi)
E.	600 kPa (87 psi)

Answer 14

D. 300 kPa (43.5 psi)

Question 15

15.	The single-stage rotary screw compressor will develop discharge pressures to about:
A.	400 kPa (58 psi)
B.	200 kPa (29 psi)
C.	100 kPa (14.5 psi)
D.	500 kPa (72.5 psi)
E.	600 kPa (87 psi)

Answer 15

A. 400 kPa (58 psi)

Question 16

16. Priming of a centrifugal pump means:
    A. Filling the casing with the fluid being pumped
    B. Evacuating the casing of air
    C. Filling the casing and suction line with the fluid being pumped
    D. Installing a foot valve on the pump discharge line
    E. Starting the pump first

Answer 16

C. Filling the casing and suction line with the fluid being pumped

Question 17

17.	Usually the cause of the bearing trouble is one of the following:
A.	Proper viscosity of oil
B.	Proper bearing design
C.	True alignment of shaft and bearing
D.	Temperature of oil too low
E.	Loss of oil supply

Answer 17

D. Temperature of oil too low

Question 18

18.	The temperature of under normal conditions will be about \_\_\_\_\_ near the end of the compression stroke.
A.	225°C (437°F)
B.	175°C (347°F)
C.	90°C (194°F)
D.	150°C (302°F)
E.	75°C (167°F)

Answer 18

C. 90°C (194°F)

Question 19

19. Which of the following statements about rotating mechanical seals is false?
    A. The sealing ring is fastened to the pump shaft
    B. The mating ring will turn with the shaft
    C. The spring is fastened to the pump shaft
    D. The mating ring is held stationary within the pump casing
    E. The sealing ring will turn with the shaft

Answer 19

B. The mating ring will turn with the shaft

Question 20

20. When the pump is located above the source of supply and the priming water comes from an external source the pump is primed in the following manner except:
    A. Close the discharge valve
    B. Open the external supply valve
    C. Open the air vent valve
    D. Water flows into the pump and suction line where it is prevented from escaping by the foot valve
    E. When air flows from the vent valves the pump is primed

Answer 20

E. When air flows from the vent valves the pump is primed