Hydraulics generally covers the theory of the flow behaviour of liquids. In engineering, it refers to the use of Hydraulic fluids to transfer signals, force and energy.
A hydraulic system is a type of transmission system, such as the other familiar types of mechanical, electric and pneumatic transmission systems. In many applications, these can be used as completely alternative or hybrid solutions, depending on the requirements.
In general, the hydraulic fluid transfers power, energy or force/torque from the prime mover (pump) to the working unit (cylinder or hydraulic motor). Introducing pressurised fluid into cylinders causes the pistons and piston rods inside them to move in a linear direction. This movement is used for work processes and to drive machines. Hydraulic motors are used for rotating drives. The power parameters of the prime mover are adapted to the requirements of the working unit. The transferred power results from the factors of pressure and fluid flow.
The following are generally used as hydraulic fluids:
- Hydraulic fluids based on mineral oil
- Flame-resistant hydraulic fluids
- Readily biodegradable hydraulic fluids
Hydraulics also encompasses the subdivisions of hydrostatics and hydrodynamics.