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How do I calculate impeller size?

How do I calculate impeller size?

How do I calculate impeller size?

Currently I have a pump with an 11" impeller at a discharge pres of 22psi and 112GPM.

I'd like to know how much will the flow and/or pressure will change if I trim or increase my impeller size.

is there a formula for this ?

thank u

RE: How do I calculate impeller size?

Flow may not change. Pressure will be proportional to diameter squared.

RE: How do I calculate impeller size?


For general terms the pump affinity laws apply to impeller size or rotating speed.  

22 PSI at 112 GPM sounds low for an 11 inch impeller.  Hope this is a slow running pump.

RE: How do I calculate impeller size?


As suggested by D23 use the affinity laws to provide a rough appoximation of the effect of changing impeller size.


You can expect this formula to give you accuracy within 10 to 30%.

RE: How do I calculate impeller size?

Affinity laws are the best equations to calculate and estimte the changes, however these are constant efficiency equations. But when there is a change in impellar size, efficiency does change and hence these equations may not predict the changes very accurately, however they definitely give a close estimate.

hope this helps.

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