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Hydraulic Oil Pump - Horsepower vs. Pressure and Volume Flow

The power required for hydraulic pumping.

Hydraulic pump - horsepower

Horsepower required by a hydraulic pump can be calculated as

P HP = q p / 1714                                                     (1)


P HP = horsepower (HP)

q = flow (gpm)

p = required pressure (psi)

  • 1 gpm (US) =6.30888x10 -5 m3 /s = 0.227 m3 /h = 0.06309 dm3 (litre)/s = 2.228x10-3 ft3 /s = 0.1337 ft3 /min = 0.8327 gpm (UK)
  • 1 psi (lb/in2) = 144 psf (lbf /ft2) = 6,894.8 Pa (N/m2) = 6.895x10-3 N/mm2= 6.895x10-2 bar
  • 1 hp = 745.7 W

Hydraulic pumps - flow vs. horsepower graph

Example - Hydraulic Pump

The horsepower required by a a pump with flow 20 gpm and 1500 psi increase in pressure can be calculated as

P HP = (20 gpm) (1500 psi) / 1714

= 17.5 HP


Note that the equation above is for a pump with 100% efficiency - which in the practial life is never true. An overall efficiency of 80 - 95% is common.

The equation above (1) can be modified to

P HP = q p / ((μ / 100) 1714)                                        (2)


μ = overall efficiency (%)

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