Axial Thrust in Centrifugal Pumps

Question 1

What is the driving force of axial thrust?

Answer 1

Different pressures axially across the suction and discharge of each stage.

Question 2

What measurement is crucial for axial thrust calculation?

Answer 2

The difference of the suction and discharge areas of each stage, usually the impeller eye diameter.

Question 3

Axial thrust is caused by internal pressures acting on what components?

Answer 3

Impellers, sleeves, mechanical seals, shaft.

Question 4

If thrust load is too small, what can happen to the bearings?

Answer 4

Skidding damage

Question 5

If thrust load is too large, what can happen to the bearings?

Answer 5

Failure before L10 life

Question 6

Axial load should put the shaft in tension or compression? Why?

Answer 6

Tension. Compression can cause bending, and yields weaker material properties.

Question 7

What axial force adjustment can be made, but may cause compression?

Answer 7

Balance holes

Question 8

Concerning axial load, what should the area ratio be? Why so high?

Answer 8

8 X. Because as the wear rings clearances degrade, recirculation flow increases. Also this accounts for API seal plan flows.