WHAT IS THE DIFFERENCE BETWEEN NPSHA AND NPSHR?

24th Jul 2020
NPSH

npsha & npshr

What is the difference between NPSHa and NPSHr ?

Let’s start with what NPSHa and NPSHr mean. NPSHa stands for Nett Positive Suction AVAILABLE and NPSHr stands for Nett Positive Suction Head REQUIRED.

Now, what is the difference between NPSHa and NPSHr? Well, firstly NPSH is a measure of the pressure experienced by the fluid at the suction of the pump. This is always quoted in metres (or feet) rather than as a pressure because head is a fluid independent property. Keep in mind that a pump will always lift liquid to the same height regardless of the fluid's respective densities. 

NPSHa (available) is a property of the system and is calculated by the system designer giving a value of the pressure on the suction side of the pump. 

NPSHr (required) is a property of the pump. This is calculated by the manufacturer as the point where cavitation occurs. 

It is good practice to have a safety margin between 0.5m and 1m. 

Find us on Socials

We regularly update our LinkedIn page with articles and news, so go give us a follow to stay up to date. You can also find more articles by us on our blog and news page.

 

If you have any enquiries then please don’t hesitate in getting in touch on [email protected] or calling us on 01425 627700.

You might also like...

transfer pump what is it

TRANSFER PUMP...WHAT IS IT?

A transfer pump is a general term for a pump that’s sole purpose is to move liquid from one place to another. Such as from a bulk storage tank to a day storage tank. They can take many forms depending upon the liquid to be transferred and the discharge pressure...

Read More
Centrifugal pumps

IS THERE A DIFFERENCE BETWEEN CENTRIFUGAL AND ROTODYNAMIC PUMPS?

Pumps often have the label as either centrifugal or positive displacement. But, you have probably heard of rotodynamic pumps which is often incorrectly interchanged with the word centrifugal pumps. So is there a difference between rotodynamic pumps and centrifugal...

Read More
common terms

COMMON TERMS USED IN THE PUMP INDUSTRY

Common terms used in the pump industry.  Absolute pressure: The absolute pressure is the sum of the gauge or dial pressure and the atmospheric pressure (14.7psi). If your pump gauge reads 150 psi, then the absolute pressure will be 164.7 psi. Absorbed Power: This is...

Read More