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From Wikipedia, the free encyclopedia

Fluid power is the technology of exploiting the properties of fluids to generate, control, and transmit power as a result of the pressurization of fluids.

As the term fluid refers either to gases or to liquids, fluid power is also subdivided into the categories of hydraulics and pneumatics. The differences being that with hydraulics the medium used is a liquid (ie mineral oil or water) and for pneumatics it is a gas (ie air or another inert gas).


Practical use

Transport energy

A fluid power system with a pump driven by a prime mover such as an electric motor or IC engine that converts mechanical energy in to fluid energy. This fluid flow is used to actuate a device specifically designed to operate with fluid energy such as:

  • Cylinder (hydraulic or pneumatic): Provides force in a linear fashion
  • Motor (hydraulic or pneumatic): Provides continuous rotational motion
  • Rotary actuator: Provides rotational motion of less than 360 degrees.


Hydraulics and pneumatics are similar in many ways, but there are clear reasons for using one over the other.

  • Cost: Pneumatics are considerably cheaper to build and operate. For one, air is used as the compressed medium, so no reservoir is needed to store fluid, nor is there any need to provide means to drain or recover fluid. With increasing working pressures, pneumatics require larger parts than hydraulics.
  • Precision: Unlike liquids, gases change volume significantly when pressurized making it difficult to achieve precision.
  • Safety: Gases tend to want to expand at high velocities when compressed, thus pneumatics are typically limited in utilities with a working pressure up to around 100 psi (7 bar).

See also


  • Esposito, Anthony, Fluid Power with Applications, ISBN 0-13-010225-3
  • Hydraulic Power System Analysis, A. Akers, M. Gassman, & R. Smith, Taylor & Francis, New York, 2006, ISBN 0-8247-9956-9

External links



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