Fundamental Pump Laws

It doesn’t matter what size, shape or design of the pump its purpose is to move fluids. Head loss that must be overcome makes the task a bit more complicated and the type of pump makes a difference.

Two of the basic pump laws are volumetric flow rate and pump power:

Volumetric Flow Rate:

The capacity of a centrifugal pump is directly proportional to its speed.

Expressed mathematically:

V @ N whereas; V = Volumetric flow rate and N = Speed

If  pump speed is doubled, pump capacity will double. If cut 50%, capacity will be halved. Discharge head is directly proportional to the square of pump speed.

Expressed mathematically:

Hp @ N2

If a pump’s speed is doubled, its discharge head will go up by a factor of four.

Pump Power:

Power required  by the pump’s driver is directly proportional to the cube of the pump speed.

Expressed mathematically:

P @ N3  whereas: P = Power required and N = Speed

If the pump’s speed is doubled, the power required by its driver will go up by a power of 8!

Why is this important?

I will discuss this in a future blog about troubleshooting centrifugal pumps.

by Mac Maccormack | September 23, 2020
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