Affinity law question 1

[oodly]

Back to basics here, I've got a pump on a VFD running at 60 Hz. It's moving 550 gpm with 90 ft. of head. If I slow this pump down until it moves only half the water, or 275 gpm, what will its head be? Thanks.

 

[SandCounter]

P₁/P₂ = (Q₁/Q₂)²

Q₁ = 550 gpm
Q₂ = 275 gpm
P₁ = 90 ft

Solve for P₂.

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I used to count sand. Now I don't count at all.

 

[LittleInch]

Or
Pump affinity for centrifugal pumps with no change in pump diameter

Flow prop to speed
head prop speed^2
power prop ^3

So half the speed, a quarter of the head so 90/4 = 22.5 ft

whether this works or not will depend clearly on your static head and system curve.
If it's not moving any (or less) water at half the speed the head will be higher up the curve....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[TenPenny]

That totally depends on what the system curve looks like. How much of your head is static vs dynamic (friction)?

The only real answer is, the head will be whatever is needed to supply 275 gpm.

 

[77JQX]

What TenPenny said

 

[LittleInch]

TBF All the OP is asking for was what does the pump produce.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.