In order to drive or operate certain machinery, the hydrostatic drive system is used. This system makes use of a hydraulic fluid under pressure, making it easier to operate such mechanisms. Also known as the hydraulic power transmission, this system generally includes of valves, piping, and filters to help in guiding and controlling the system. It also includes the motor part of the transmission, in which a hydraulic motor or hydraulic cylinder is seen to be able o drive the machinery. And lastly, it also includes a hydraulic pump, driven either by an electric motor, a windmill, or a combustion engine, of which would be under the generator part of the transmission.

Pumps help with the right pressure for good machinery operations. A closer look on hydraulic pumps would show us that this particular part of the whole system is indeed a critical ingredient for good use of machinery.

A hydraulic pump is the pump usually seen and used in hydraulic drive systems. This specific pump can either be hydrostatic or hydrodynamic. Hydrostatic pertains to the pressure exerted by a stationary fluid, while hydrodynamic relates to the operation by the force of liquid in motion. Hydraulic pumps are related to a positive displacement pump, which simply means that the flow is directly parallel to the displacement of the pump per revolution, plus its speed. Simple and low budget pumps or high quality pumps are used depending on the required flow and pressure, but is also related to the required life time expectancy and efficiency.

There are several types of hydraulic pumps. While most of them fall into the fixed displacement category, some can be categorized under adjustable displacement as well. Screw pump is a type of hydraulic pump that looks sort of a double Archimedes spiral, only closed. Having two screws in one body, the screw pumps are used for high flows and relatively low pressure. Usually seen on board ships, this pump has a constant pressure hydraulic system for the control of ball valves, and also for the steering gear and help drive systems. Although the efficiency is not that high, this type of hydraulic pump has the advantage of low sound levels. Another type would be Gerotor pumps. This very special pump has more efficiency as well as the sound level, knowing that this is only a medium pressure pump. Gear pumps are on the simple side, an economic pump that is used in simple hydraulic systems. However, the efficiency of such is not very good, especially at higher pressures. Vane pumps would be another type of hydraulic pumps where it has a higher efficiency rate as compared to gear pumps. In general, vane pumps can be used for mid pressures for up to 180 bars. There is also the axial piston pump, which has the best efficiency level among all the other pumps. These pumps can work with a pressure of up to 350 bars. Radial piston pumps, on the other hand, are used specifically for high pressure and relatively small flows.