There are usually three types of hydraulic pump constructions found in mobile hydraulic applications. These include equipment, piston and vane; however, there are also clutch pumps, dump pumps and pumps for refuse automobiles such as dry valve pumps
The hydraulic pump is the component of the hydraulic system that takes mechanical energy and converts it into fluid energy in the form of oil flow. This mechanical energy 
is taken from what is called the primary mover (a turning drive) such as the power take-off or straight from the vehicle engine.
With each hydraulic pump, the pump will be of the Hydraulic Pump china uni-rotational or bi-rotational design. As its name implies, a uni-rotational pump is designed to operate in one direction of shaft rotation. On the other hand, a bi-rotational pump has the ability to operate in either path.