Computing GPM with Differential pressure (DP)

[bluenote49]

Can someone provide me with the formula for this and regarding the DP values is it possible just to deduct the readings on both suction and discharges gauges to get the DP?

For example in suction side of the pump the reading is 3 BAR and in the discharge line the Pressure is 4.5 BAR so the DP is 1.5 BAR. Is this correct?

 

[LittleInch]

There is no "formula".

Yes you are correct, that is the meaning of "differential".

You might be able to estimate flow by using the pump curve, but this is only an estimate with about 25% accuracy.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[Artisi]

Agreed, you may be able to predict the approximate flow rate if you have an accurate pump performance curve - but very hit and miss - I wouldn't / couldn't predict any accuracy.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[LittleInch]

Artisi, True- If you get in the flat part of the pump curve it could be impossible to put a figure from zero flow to almost full flow. Blue note - it all depends on your pump curve and accuracy of instruments and knowledge of density of your fluid.

Basically forget about trying to guess flow this way and find another. Differential pressure across a control valve can be reasonably good, but a proper meter is much better

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way