Types of Hydraulic Pumps Explained: How They Work and Exactly What You’ll Need

hydraulic pump

Hydraulic Pumps can be described as the classes of machines that use positive displacement for hydraulic power applications that provide the flow of hydraulic fluid to machines like cylinders, rams motors, etc. The power-steering pumps in cars are an example of where engine-driven rotary-vane pumps are standard. The gear-type oil pump of the engine is another typical illustration. Hydraulic pumps can also be motor-driven or operated manually operated. Pumps with variable displacement are particularly useful since they can provide infinite adjustments across their speed range and maintain a constant rpm for their input.

Hydraulic pumps

A hydraulic pump is an external tool that can be used to pump water, oil, or other fluid substances. They are often used in agriculture and manufacturing to move fluids or air. Hydraulic pumps are also becoming more common in the leisure industry as they can be used for various tasks, such as pumping gasoline and diesel fuel, removing water from ponds, and flushing toilets.

Hydraulic pumps
Image Source: Mobile Hydraulic Tips

Types of Hydraulic Pumps

Beginning using variable displacement pumps, the main kinds of hydraulic pumps currently that are in use comprise:

  • Axial piston pumps
  • Radial piston pumps
  • Pumps for Rotary Vanes
  • External gear pumps
  • Internal gear pumps

Pumps create flow. Pressure is the resistance to flow. Whereas centrifugal pumps can run against blocked discharges without building up excess pressure, positive-displacement pumps cannot. Hydraulic pumps, like any positive-displacement pump, thus require overpressure protection, generally in the form of a pressure-relief valve. Over-pressure relief is usually integrated into the pump itself.

Hydraulic systems are employed when the need for compact power is present, and mechanical, electrical, or pneumatic systems could become too huge, risky, or simply inadequate for the task. For example, hydraulic power can move heavy buckets and booms in the construction industry. In the manufacturing industry, hydraulic power is employed to power presses and other high-force equipment. The heart of the hydraulic process is the motor, and the selection of the appropriate hydraulic pump depends on how the system is required to perform.

Axial Piston Pump

Axial piston pumps are hydraulic pumps that use a rotary motion to move fluid through an open channel. These pumps are commonly used in water systems, agricultural pumping, and other industrial applications. Axial piston pumps utilize pistons mounted in an axial direction that move inside internal cylinders, creating an alternating flow of suction and discharge. They can be constructed as adjustable rate devices, making them suitable for controlling the speed of hydraulic motors and cylinders. In this model, the swashplate is utilized to alter the depth so that each piston can extend into its cylinder while the pump turns, affecting the discharge volume. In addition, the pressure compensator piston can be utilized in certain designs to ensure an equal discharge pressure under various demands.

Axial Piston Pump
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Radial Piston Pumps

Radial piston pumps (RPPs) are hydraulic pumps that allow for greater displacement and flow rates with less noise. They are used extensively in oil and gas production, mining, and construction industries. Radial piston pumps have been increasingly adopted in the past decade because of their advantages over other pump types.

Radial Piston Pumps
Image Source: Power Transmission World

The pistons of radial pumps place several pistons that are radially arranged around a hub for a rotor. The rotor is mounted eccentrically inside the pump housing and can force the pistons into and out of the cylinders as it rotates. That causes hydraulic fluid to flow into the cavity of the cylinder and then be discharged from it. Outlets and inlets to the pumps are within a valve inside the central hub. A different design is to place outlets and inlets along the outside of the housing for the pump. Radial piston pumps can be purchased as fixed- or variable-displacement models. In the variable-displacement version, the eccentricity of the rotor in the pump housing is altered to decrease or increase the stroke of the pistons.

Rotary Vane Pumps

Rotor vane pumps employ several rigid vanes arranged in an eccentric rotor that moves along the inside walls of the housing cavity, creating smaller volumes that force the fluid to exit through the port for discharge. In certain models, the volume of fluid that exits the pump may be controlled by changing the rotational axis on the rotor relative to the housing. Zero flow is achieved when the housing and rotor axles are in alignment.

Rotary Vane Pumps
Image Source: GrabCAD

Rotary vane pumps are an essential part of hydraulic systems. They use rotating disks to create a vacuum and pump water or oil. These pumps can be used in various applications, such as pumping water from a well or are, extracting oil from wells, and providing power to machines.

External Gear Pumps

External gear pumps (EGPs) can be used with an onboard engine to provide pressurized water or other fluid to various parts of the engine. They are typically used in high-volume manufacturing, oil and gas exploration, and mining.

External Gear pump
Image Source: ResearchGate

External gear pumps depend on the counter-rotating movement of spur gears meshed externally to give motion to the fluid. They are typically fixed-displacement models extremely simple and durable. They are usually closed-coupled designs in which the pump and motor have a common shaft and mounting. On top of that, oil moves around the housing perimeter for the pump in between gear teeth. On the side, that is the outlet, the meshing effect of the teeth diminishes the capacity to release the oil. The little amount of oil stuck between the re-meshing gears flows through the bearings before returning to the suction side of the pump. External gear pumps can be popular in fixed displacement hydraulic applications because they can produce extremely high pressures.

Internal Gear Pumps

This inner gear pump uses the meshing action of an external and an internal gear, which is paired with an element shaped like a crescent to produce fluid flow. The external gear’s axis is offset from the internal gear. And as the two gears spin, the two gears’ movement out of and through meshes creates suction and discharge areas. The sector is an obstacle between discharge and suction. Another type of internal gear pump, known as the generator, utilizes meshing trochoidal gears to achieve similar suction zones and discharge areas without using a sector.

Internal Gear Pumps
Image Source: Pye-Barker Engineered Solutions


This article briefly overviews some of the most commonly used kinds available in hydraulic pumps. For more details on other areas, check out the additional guides or go to our Thomas Supplier Discovery Platform to find possible sources of supplies or read more about particular products.

Mia A Chloe
Author: Mia A Chloe

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