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How do Hydraulic Pumps Work?

How do hydraulic pumps work?

Fundamentally, a hydraulic pump is a mechanical device that converts mechanical power into hydraulic energy. It generates flow with enough power to overcome pressure induced by the load.


When a hydraulic pump operates, it performs two functions. First, its mechanical action creates a vacuum at the pump inlet, which allows atmospheric pressure to force liquid from the reservoir into the inlet line to the pump. Second, its mechanical action delivers this liquid to the pump outlet and forces it into the hydraulic system.


A pump produces liquid movement or flow, it does not generate pressure. It produces the flow necessary for the development of pressure, which is a function of resistance to fluid flow in the system. For example, the pressure of the fluid at the pump outlet is zero for a pump not connected to a system (load). Further, for a pump delivering into a system, the pressure will rise only to the level necessary to overcome the resistance of the load.


Types of Hydraulic Pumps

In mobile hydraulic applications there are typically three types of hydraulic pumps used. These include gear, piston and vane pumps.


Hydraulic Gear Pumps



Hydraulic gear pumps convert mechanical power into the hydraulic energy of the fluid. The rotation of the gear causes the suction at the inlet and fluid is transferred by the pump. The fluid flows over the gears. The mechanical energy by the rotation of gears is transferred into the fluid pressure at the discharge.


At Neilson Hydraulics we stock a large quantity of Bosch Rexroth products but also with our sister company VHS Hydraulic Components we have access to stock of numerous brands of gear pumps including Casappa, Dana Brevini and the OT gear pumps.


Hydraulic Piston Pumps

The piston pump is a hydraulic pump that delivers optimum efficiency and reliability while maintaining a compact size with a high power density. Hydraulic piston pumps can handle large flows at high hydraulic system pressures.


In these pumps, the pistons accurately slide back and forth inside the cylinders that are part of the hydraulic pump. The sealing properties of the pistons are excellent, which makes it possible to operate at high pressures with low fluid leakage. Piston pumps are the hydraulic pumps with the highest-pressure rating and best overall efficiency.


At Neilson Hydraulics we stock and supply the Bosch Rexroth flagship A10VO variable displacement piston pump and also as part of a large group with our sister company Parmafluid the A17FO axial piston fixed displacement pump plus many more Bosch Rexroth products.





Type of Piston Pumps

  • Axial piston pump, fixed displacement
  • Axial piston pump, variable displacement
  • Radial piston pump, fixed displacement
  • Radial piston pump, variable displacement


Hydraulic Vane Pumps

Vane pumps are hydraulic pumps that operate at very low noise levels. Vane pumps tend to be a compromise between gear and piston pumps. They are limited by their maximum pressure rating and this is a sign of their relative fragility to gear and piston pumps. Hydraulic vane pumps operate with much lower flow pulsation, i.e. constant flow. As such, vane pumps produce less noise while maintaining a relatively high speed of up to 3,000 rpm.


As a group with our sister companies VHS Hydraulic Components and Parmafluid, we supply the entire range of hydraulic Bosch Rexroth vane pumps including the PV7 Vane pumps for use on a wide range of industrial manufacturing applications.




To enquire or speak to our technical team about all your hydraulic pump or hydraulic problems please contact Neilson Hydraulics on: 01709 821002/ E: sales@neilson hydraulics.co.uk or visit our website at: www.neilson-hydraulics.co.uk.