Chapter 74

Question 0

The purpose of "wear rings" in centrifugal pumps is to:
A) lower the pump pressure
B) increase the efficiency
C) eliminate the need for a relief valve
D) prevent wear on the pump inlet
E) prevent wear on the pump discharge

Answer 0

B) increase the efficiency

Question 1

A slight leakage is desired between the pump shaft and packing of the majority of pumps in order to:
A) prevent the ingress of atmospheric air
B) increase the pump capacity and efficiency
C) prevent wearing of the wear rings
D) lubricate the surfaces
E) prevent the pump from vapour locking

Answer 1

D) lubricate the surfaces

Question 2

Flexible couplings will compensate for:
A) overheating of packing
B) axial misalignment
C) bearing failure
D) shaft eccentricity due to a badge bent shaft
E) impeller imbalance

Answer 2

B) axial misalignment

Question 3

Proper priming and venting of a pump is important, especially if:
A) the medium being pumped is high temperature
B) the medium being pumped contains suspended solids
C) the pump has a stuffing box and lantern ring
D) a mechanical seal is used
E) oil or other low flash point lubricant is being pumped

Answer 3

D) a mechanical seal is used

Question 4

Most pump failures and damage occur:
A) after about six months of continuous service
B) due to vapour binding
C) during initial startup
D) due to wrong rotation
E) because of inadequate operator training

Answer 4

C) during initial startup

Question 5

A plugged impeller symptom or result will be:
A) air leaks in suction line and stuffing boxes
B) wrong direction of rotation
C) loss of prime
D) an overheated stuffing box
E) no liquid being delivered

Answer 5

E) no liquid being delivered

Question 6

List four advantages of mechanical seals when compared with packing glands:

Answer 6

Less maintenance is required
There is no wear on the shaft or shaft sleeve
Leakage is reduced to a minimum
Allows design of very high temperature and pressure applications

Question 7

Two ways in which a pump and motor shaft can be out of alignment are _______ misalignment and _______ misalignment.

Answer 7

Angular, offset