Free Millwright Pumps, Seals, and Packing Questions and Answers

Question 1

What is the primary cause of cavitation in a centrifugal pump?

Accepted Answer

Suction pressure dropping below the liquid's vapor pressure

Answer

Excessive discharge pressure (dead-heading)

Answer

Incorrect direction of motor rotation

Answer

Misalignment between the pump and motor

Question 2

In a typical mechanical seal, what are the two primary, lapped sealing surfaces called?

Accepted Answer

The stationary and rotating faces

Answer

The gland and the shaft sleeve

Answer

The O-ring and the gasket

Answer

The impeller and the casing wear ring

Question 3

When installing new packing rings into a stuffing box, how should the joints of consecutive rings be oriented?

Accepted Answer

Staggered by 90 or 180 degrees

Answer

All joints should be aligned at the top (12 o'clock)

Answer

Randomly placed with no specific orientation

Answer

Aligned with the lantern ring port

Question 4

What is the term for the condition where the pump and motor shafts are parallel but their centerlines are offset from each other?

Accepted Answer

Parallel misalignment

Answer

Angular misalignment

Answer

Soft foot

Answer

Axial float

Question 5

What is the function of a lantern ring (or seal cage) in a pump's stuffing box?

Accepted Answer

To distribute sealing or flushing liquid to the packing

Answer

To prevent the packing from extruding

Answer

To act as a primary bearing surface for the shaft

Answer

To scrape contaminants off the shaft before they reach the packing

Question 6

A pump that uses intermeshing gears, lobes, or screws to move a constant volume of fluid with each rotation is best classified as what type of pump?

Accepted Answer

Positive displacement pump

Answer

Centrifugal pump

Answer

Eductor-jet pump

Answer

Dynamic pump