Hydraulics is a mechanical function that operates through the force of liquid pressure. In hydraulics-based systems, mechanical movement is produced by contained, pumped liquid, typically through cylinders moving pistons. It combines mechanical, electronics, and software engineering in the designing and manufacturing of products and processes.
Simple hydraulic supplies systems include aqueducts and irrigation systems that deliver water, using gravity to create water pressure. These systems essentially use water’s own properties to make it deliver itself. More complex hydraulics use a pump to pressurize liquids, moving a piston through a cylinder as well as valves to control the flow of oil.
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Hydraulics are similar to pneumatic systems in function. Both systems use fluids but, unlike pneumatics, hydraulics use liquids rather than gasses. Hydraulics systems are capable of greater pressures: up to 10000 pounds per square inch (psi) vs about 100 psi in pneumatics systems. This pressure is due to the incompressibility of liquids which enables greater power transfer with increased efficiency as energy is not lost to compression, except in the case where the air gets into hydraulic lines.
Fluids used in hydraulics may lubricate, cool, and transmit power as well. Pneumatics, being less multifaceted, require oil lubrication separately, which can be messy with air pressure. Pneumatics are simpler in design and to control, safer (with less risk of fire) and more reliable, partially as the compressibility of the gas-absorbing shock can protect the mechanism.