Fluid Power General Design Rules and Application

Hydraulic and Pneumatic Knowledge

Horsepower for driving a pump:

  • For every 1 HP of drive, the equivalent of 1GPM @ 1500 PSI can be produced.

Horsepower for idling a pump:

  • To idle a pump when it is unloaded will require about 5% of its full rated horsepower.

Compressibility of water:

  • Volume reduction is about 1/3% for every 1000 PSI pressure.

Compressibility of hydrualic oil:

  • Volume reduction is approximately 1/2% for every 1000 PSI of fluid pressure.

Flow velocity in hydraulic lines:

  • Pump suction lines 2 to 4 feet per second
  • Pressure lines up to 500 PSI, 10 to 15 feet/sec
  • Pressure lines 500 to 3000 PSI, 15 to 20 ft/sec
  • Pressure line over 3000 PSI, 25 ft.sec
  • All oil lines in air-over-oil system, 4 ft.sec