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Hydraulic Pump Classification

When a hydraulic pump goes into operation, it performs to key functions. Firstly, its mechanical action creates a vacuum at the pump inlet which allows the atmospheric pressure to force liquid from the main reservoir into the inlet line to the pump. Secondly, its mechanical action delivers this liquid to the pump outlet and forces it into the hydraulic system.

A pump produces flow and liquid movement, which does not actually generate any form of pressure. It produces the flow necessary for the development of pressure, which is a function of resistance to fluid flow in the system. The pressure of the fluid at the pump outlet is zero, for a pump which is not connected to a system. If the pump is delivering into a system, then the pressure will only rise to the level necessary to overcome the resistance of the load itself.

Hydraulic Pump Classification

All pumps are classified as either positive-displacement or non-positive-displacement. Most pumps which are used in hydraulic systems are positive-displacements.

Non-positive-displacement pumps produce a continuous flow. However, as they do not provide an internal, positive seal against slippage, its output varies considerable as pressure varies. Both propeller pumps and centrifugal pumps are typical examples of a non-positive design.

If the output port of these models were to be blocked off, either as a result of mistaken installation of fluid contamination, the pressure itself would rise whilst the output would decrease to zero. Although the pumping element itself would continue to move, the flow would be stopped as a result of the slippage.

In a positive-displacement pump, slippage is negligible when compared to the pump’s overall output flow. If the out-flowing port on these models were to be plugged, then pressure would instantly increase to the point that the pump’s moving element or its case, would probably explode or stall.

The Types Of Hydraulic Pumps

There are a wide range of hydraulic pumps available to meet the requirements of your system, and they each operate in different ways. Some of the most common forms of pump include:

  • Reciprocating Pumps
  • External/Internal Gear Pumps
  • Lobe Pumps
  • Screw Pumps
  • Internal-Gear Pumps
  • Balanced/Unbalanced Vane Pumps

Intelligently-Designed Hydraulic Components, From Flowfit Online

Here at Flowfit Online, we are extremely proud to offer a diverse range of hydraulic pumps and other components, to help you enjoy a reliable service from your system. As the UK’s leading provider of hydraulic components, we only offer the very best in hydraulic components.

If you’re looking for reliable hydraulic pumps, then you need to look no further than the diverse and extensively tested range available here at Flowfit Online. For more information on our wide range of hydraulic components, accessories and systems, please don’t hesitate to get in touch with our dedicated specialists today on 01584 876 033.

Alternatively, you can email your questions directly to our team at, and we will get back to you as soon as we can!

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