I'm trying to build a hydraulic power unit with a 5 horsepower electric motor, gear pump and tank. The flow requirement for the system is 1.7 gallons per minute. The pressure requirement is 3000 psi. I'm having some trouble finding gear pumps that are rated for high pressure and low speed. Typically they're at about 20 gallons per minute and some are around 2gpm.

I'm wondering if I get a gear pump that's capable of 2 gallons per minute and run it at a lower speed, will it still be capable of the same pressure that it's rated at at 2 gallons per minute?

Does this have diminishing returns with even lower speeds? For example if I get a pump rated at 4 gallons per minute and run it at less than half the rated speed, will it deliver the same pressure that it's rated for?

  • $\begingroup$ Gear pumps come with data sheets showing the performance cf speed. If the pump you are looking at does not have a data sheet then don't buy it. $\endgroup$
    – Solar Mike
    Commented Aug 2, 2022 at 7:49

1 Answer 1


I think 2 GPM with lowering speed to 1.7 GPM will be OK. In fact, engineer always select next larger capacity when (in most of the case) the equipment is not readily available.

For pressure, actually the pressure will depends on back pressure. But as long as the pump at least can push 3000 psi, gear pump should be better choice in term of losing pressure at lower speed (compare to progressive cavity pump, vane pump, and other non rigid sealing mechanism) - maybe second best maintaining pressure at lower speed to Reciprocating Pump only.

So, go for it!


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