There are many types of machinery that are driven by or actuated by a hydraulic pump. There are a variety of different systems that are used to generate the flow and pressure required and they all have a hydraulic fluid and a system that controls the fluid and pressure with hydraulic valves. The pump needs to driven and this can be done by any force generating device such as an electric motor, an internal combustion engine, wind power or even a person operating a lever or crank.

How It Works
A hydraulic fluid is put under pressure by the hydraulic pump and the pressure can then be used to drive a piston or drive unit via hydraulic lines. A hydraulic valve is used to switch the force on and off to give control of the device. The control can be mechanical or electrical and may be actuated manually through a lever or a button or automatically through control system.

Volume and Pressure
There are many different hydraulic systems and they all used a combination of volume displacement and pressure to work. The higher the pressure the more robust a system needs to be because of the tremendous forces involved. In general higher pressure systems are more efficient and the higher the pressure the less flow is required for the same application of force. There are two general types of pumps fixed displacement types that displace the same amount of fluid every cycle and adjustable displacement types that can vary the displacement for increased or decreased pressure.

Pump Types
There are many different types of hydraulic pumps that have different applications. Screw type pumps are good for high volumes at relatively low pressure. They are simple and effective but not particularly efficient. A gear pump has a more balanced pressure and flow and is very simple but is not very efficient particularly as pressure increases.

The vane pump is widely used in system of medium pressure up to 150 bar and beyond. While the axial piston pump is used in applications that require the highest efficiency. Where high pressure above 300 bars is needed the radial piston pump combine high pressure and low flow rates needed in these applications.