In brief
Fluid power is the umbrella term for hydraulics and pneumatics, i.e. the transmission of energy and signals by means of pressurised liquids or gases.
Contents
What is Fluid power?
Fluid power covers all methods in which a pressurised medium transmits forces and movements. In hydraulics the medium is usually a mineral oil or another hydraulic fluid, in pneumatics compressed air. Hydraulics is suited to large forces in a compact design, pneumatics to fast, comparatively light movements and simple automation tasks.
A fluid power system consists of energy generation (pump or compressor), conditioning (filters, coolers, air service unit), control (directional, pressure and flow control valves) and actuation (cylinders, motors). Pipes, fittings and hoses connect the components, and accumulators and reservoirs complete the system. The graphical symbols for circuit diagrams are standardised in ISO 1219-1, so that diagrams can be read internationally.
For maintenance, cleanliness of the medium, leak-tightness and the condition of seals and hoses are decisive. Many failures are due to contamination, leakage or ageing. Replacement requires precise information on pressure rating, connection type and medium, because seemingly identical components can differ in these respects.
In practice: maintenance and procurement
For spare parts enquiries in fluid power, the operating pressure, nominal size, connection thread, seal material and medium should be stated in addition to the part number. An up-to-date circuit diagram helps to determine the function of a component unambiguously.
Synonyms and abbreviations: hydraulics and pneumatics · fluid technology · fluidics · fluid power systems
Frequently asked questions
What is the difference between hydraulics and pneumatics?
Hydraulics works with virtually incompressible liquids and high pressures; it generates large forces and allows precise, smooth movements. Pneumatics uses compressible compressed air at much lower pressures; it is fast, clean and simple, but less rigid and less suitable for large forces. Both belong to fluid power.
What does ISO 1219 cover?
ISO 1219-1 specifies graphical symbols for fluid power components and systems, for example for pumps, valves, cylinders and filters. Further parts of the standard deal with the layout of circuit diagrams. As a result, hydraulic and pneumatic diagrams can be read regardless of language and manufacturer, which makes troubleshooting and spare part identification easier.
Which components make up a hydraulic system?
A hydraulic system comprises a reservoir, a pump with drive, filters, valves for controlling direction, pressure and flow, and cylinders or hydraulic motors as actuators. These are supplemented by pipes, hoses, accumulators, coolers and measuring instruments. Reliability depends heavily on the cleanliness of the hydraulic fluid.