Hydraulic pumps can be placed into two distinct classifications: fixed displacement types, which include gear pumps, screw pumps and generator pumps, and variable displacement types, which include rotary vane pumps, radial piston pumps, axial piston pumps and bent axis hydraulic pumps. Screw pumps are further categorized into single end, double end, single rotor, multi-rotor timed and multi-rotor untimed pumps.
Hydraulic pumps are widely used in various engineering fields and come in a variety of designs. Each pump has a different internal mechanism based on the same fundamental principle. Hydraulic pumps create an efficient and flexible form of energy transfer by converting a liner or rotary motion to hydraulic energy. The fluid exits the pump at a higher pressure and velocity than when it initially entered the pump. It is important to note that the pump doesn't produce pressure, it simply produces flow.
The overall efficiency of hydraulic pumps is the product of the mechanical and volumetric efficiencies. The need to power modern machinery is driving major innovations in hydraulic energy. Hydraulic pumps are favored because of their simple designs and high efficiency. Other types of pumps include reciprocal pumps, centrifugal pumps, sumps pumps, screw pumps, vacuum pumps and hand pumps.