Hydraulic Pump Output Flow
The gpm a hydraulic pump delivers from its displacement and drive speed.
Example
You enter
- Pump displacement (in³/rev) 2
- Drive speed (rpm) 1800
- Volumetric efficiency (0-1) 0.95
You get
- Q theo (GPM) 15.584
- Delivered flow 14.81 gpm
- Q slip (GPM) 0.779
Details, formula, and sources
Theoretical flow = disp x rpm / 231, delivered = theoretical x volumetric efficiency. A 2.0 in^3/rev pump at 1800 rpm and 0.95 vol eff makes 15.58 theoretical but delivers 14.81 gpm - the 0.78 gpm difference is internal slip that grows with pressure and wear. A sizing aid; the pump manufacturer's data govern.
q_theo = disp x rpm / 231; q_actual = q_theo x vol_eff; q_slip = q_theo - q_actual.
The fluid-power pump displacement-flow relation (theoretical flow = disp x rpm / 231), by name.
The displacement-based flow relation and the 231 in^3/gal constant are standard published fluid-power results.
Estimate. AHJ and licensed professional govern.
Field names used by the API: disp_in3, rpm, vol_eff, q_theo_gpm, q_actual_gpm, q_slip_gpm
- Theoretical flow disp x rpm / 231 (231 in^3 per gallon)fluid-power engineering
- Delivered flow theoretical x volumetric efficiency; the slip grows with pressure and wearfluid-power engineering
- Sizing only the delivered gpm feeds the pump-horsepower tile; the manufacturer data governscope of this tile