Fluid deforms continuously on the application of shear stress, no matter how much small is it. Fluid comprises both gases and liquid. The technique of using liquid for power transmission is called as hydraulics while which uses gases for power transmission is called Pneumatics. In most hydraulic systems, mineral oils will be used while in most pneumatic systems, atmospheric air will be used. Principle behind fluid power The basic principle which governs any fluid system is the pascal law. The law applies to fluid power transmission. The other laws which will be used in the analysis, design and manufacturing of any fluid system are Boyle's law, Charles's law and Bernoulli theorem. Property of fluid For reliable and proper working of hydraulic system the fluid used should have the following certain qualities. Some of them are Viscosity The fluid used should have its viscosity in the specified range. Higher viscosity will lead to higher friction and wear while lower viscosity will lead to leakage problems Viscosity Index This determines the change of viscosity with respect to temperature. Oil with High VI is preferable Oxidation resistance The continuous use of oil will promote oxidation. So the oil should be able to resist oxidation Pour and Cloud point These determines the lowest range of temperature below which the fluid will not transmit power Flash and fire point These determines the highest range of temperature above which fluid will catch fire and will cease to transmit power. Lubrication The fluid should be able to lubricate the moving parts in the system. Heat generation and transmission The amount of heat generated should be less. The fluid should have capacity to transmit the heat generated Corrosion resistance The fluid should not corrode the parts of the system. Some of the most commonly used fluid for power transmission are water, emulsions, Water glycol, Synthetics, air and compressed gases Parts of fluid system The most of fluid system will employ some or all of the following parts Pump or Compressor: This gives the motion to the fluid which is used to perform useful work Control Valves: These are used to regulate and control the flow of the fluid Tubes, pipes and Hoses: These carry the fluid from the pump/compressor to the actuator Actuator: The actual work is performed by the actuators. Discharge Tank: The liquid after performing work will be discharged into a tank in case of liquids