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