CPM Bearings, Seals, and Shaft Couplings 2

Question 1

A mechanical seal in a centrifugal pump creates its primary seal between which two components?

Accepted Answer

A rotating seal face and a stationary seat

Answer

The shaft sleeve and the stuffing box bore

Answer

The impeller back shroud and the back plate

Answer

The pump casing halves at the split line

Question 2

Compared to compression packing, the primary operational advantage of a mechanical seal is:

Accepted Answer

Near-zero leakage during normal operation

Answer

Lower initial purchase and installation cost

Answer

Simpler installation requiring no special tools or training

Answer

Tolerance of much greater shaft runout and deflection

Question 3

A radial lip seal (rotary shaft seal) should be installed with the sealing lip oriented:

Accepted Answer

Toward the fluid being retained

Answer

Away from the fluid being retained

Answer

Perpendicular to the direction of shaft rotation

Answer

In the direction opposite to shaft rotation

Question 4

When replacing compression packing in a pump stuffing box, adjacent packing rings should be staggered by:

Accepted Answer

90° so no two ring joints are aligned

Answer

45° so joints alternate every other ring

Answer

120° distributing three joints evenly

Answer

180° placing joints directly opposite each other

Question 5

What is the purpose of a lantern ring installed within a packed stuffing box?

Accepted Answer

To distribute flush fluid or lubricant evenly around the shaft circumference

Answer

To add structural rigidity to the packing stack under high pressure

Answer

To act as the primary sealing element if the packing fails

Answer

To center the shaft and dampen vibration within the stuffing box

Question 6

An O-ring installed in a groove that is too narrow (undersized width) may result in:

Accepted Answer

Extrusion of the O-ring material into the clearance gap under pressure

Answer

Rolling and twisting of the O-ring during dynamic motion

Answer

Insufficient compression leading to immediate leakage

Answer

Accelerated chemical degradation from increased contact stress

Question 7

Which type of seal is most commonly used to prevent leakage past a reciprocating piston inside a hydraulic cylinder?

Accepted Answer

U-cup piston seal

Answer

Mechanical face seal

Answer

Labyrinth seal

Answer

Rotary lip seal