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What Is The Difference Between Hydraulic Pumps and Hydraulic Motors?

Hydraulic systems are responsible for the overall function of many machines in the agricultural and industrial sectors. These systems facilitate lifting, pushing and rotation motion under heavy loads by transforming mechanical energy into fluid power and then transferring it to their components. Among the most vital components within a system are hydraulic pumps, and hydraulic motors.

Hydraulic pumps and motors are to hydraulic systems what heart and muscles are to human beings, meaning that they shouldn’t be spoken of interchangeably, as they serve two unique, yet similar, functions. For more information, read on to find a simple breakdown of what hydraulic pumps and motors are, including their different types, and their overall importance to hydraulic systems.

What Are Hydraulic Pumps?

A hydraulic pump’s purpose is to pump hydraulic fluid power throughout a hydraulic system, delivering energy to where it’s needed.

Mechanical energy is delivered via liquid from an engine or motor output shaft in rotary motion into the pump inlet. This liquid, when delivered, is low pressure into the interior of the pump, which has different layouts depending on whether you’re using gear pumps, piston pumps, or vane pumps. Nonetheless, the fluid power is increased soon after, as the interior functions of whichever pump it is will compress and thereby pressurise the fluid. The pump then pushes it out to different areas of the hydraulic system, which is how they get the energy to function.

Types Of Hydraulic Pumps

The different types of hydraulic pumps each account for unique mechanisms required to facilitate the conversion of mechanical energy into hydraulic energy.

  • Hydraulic Gear Pumps – Hydraulic gear pumps are made up of two gears that interlock and grind against one another, powered by a motor output shaft. The rotary motion of the gears creates a vacuum whose purpose is to pull hydraulic fluid within. When inside, the gear turns and mesh tightly on the outlet side, creating high pressure within.
    • Use – Gear pumps are often used in light industry machinery, fluid power applications and small-scale hydraulic systems. This is due to their steady, consistent flow of hydraulic fluid power at moderate pressure.
  • Hydraulic Piston Pumps – An axial piston pump moves alternatively within a cylindrical chamber. Both extension and retraction of the pistons within serve two different functions. When it extends, the inlet valve is opened to draw hydraulic fluid into the chamber. Then, it extends, closing the inlet valve for the outlet. As it’s expelled, it’s also compressed, and the piston pump expels the fluid power.
    • Use – A piston pump is best used in hydraulic systems that require high pressure. They are often found in industrial manufacturing plants and mobile hydraulic systems with sophisticated control systems, such as aeroplanes.
  • Hydraulic Vane Pumps – Vane pumps have a rotor that is mounted within the cylinder, and the rotor is slotted with several vanes. Vane pumps work by taking advantage of the centrifugal force and hydraulic pressure to push the vanes out against the cylinder it’s housed in. The vanes section up the cylinder into chambers of various volumes. When they expand, hydraulic fluid is allowed into the chamber, and when they contract, the pressurised fluid is expelled through the inlet.
    • Use – Vane pumps are used in mid-pressure systems that require moderate operating speed with little pulsation. They are popularly used in air conditioning units, low-pressure hydraulic systems and automotive power steering systems.
  • Hydraulic Screw Pumps – Screw pumps are made up of two or more screws intermeshed tightly within a casing. They transport fluid from the inlet to the outlet by trapping the fluid between the threads of the screws, and the casing.
    • Use – Screw pumps are perfect for applications requiring a smooth, constant pressure flow. They are used in industrial applications that involve high fluid viscosity, such as oil flow transfer, fuel systems or a system where the efficient handling of thick liquids is critical.

Each type of hydraulic pump above is categorised as a positive displacement pump, which ensures a fixed volume of fluid is moved per cycle. This consistent flow rate enables hydraulic system conversions to be precise. The mechanical power that they convert is taken from an electric motor or an internal combustion engine.

What Are Hydraulic Motors?

Hydraulic motors are required to reconvert hydraulic power into mechanical power.

The reason for this is simple – hydraulic fluid is only used in hydraulic systems to transport energy. The fluid pressure is energy in and of itself, but it can’t be used in this form. This is why it’s converted back into mechanical power when it reaches its destination through the hydraulic motor.

Types of Hydraulic Motors

Each type of motor accommodates specific operational requirements and system designs.

  • Gear Motors – Gear motors are part of the gear pump category, and they utilise interlocking gears to convert hydraulic fluid pressure into rotational force. It is a simple and durable setup that sees common usage.
    • Use – Gear motors are best used in small machinery like winches and conveyor belts, as well as automotive such as power steering systems.
  • Axial Piston Motor – Piston motors operate through oscillating pistons moving in line with the shaft. It transforms high-pressure oil delivered by hydraulic pumps into mechanical power. This makes it suitable for complex systems requiring precision.
    • Use – Axial piston motors are preferred for high-pressure and performance applications, such as construction equipment (excavators, road rollers), marine applications (propellers) and aerospace actuation systems.
  • Radial Piston Motors – Radial piston motors feature pistons arranged circularly around a central shaft. It boasts a high torque and low speed and excels in heavy-duty applications.
    • Use – Radial piston motors’ high torque and low speed suit the demanding requirements of heavy construction machines, where high power is needed to lift, dig and otherwise handle objects.
  • Vane Motor – A vane motor sports extending vanes that spin within the casing it is housed in. The vanes’ movement of hydraulic pressure into mechanical energy.
    • Use – Light to medium-duty industrial tools use vane motors, such as automation equipment, where quiet operation of repeated tasks is beneficial, or power-assisted brakes for automobiles.

There are two types of displacement motors available. Fixed displacement motors deliver a constant torque and speed output, for example, and are far simpler in design. Variable displacement motors, however, allow for adjustment of the displacement volume.

Interplay Within Hydraulic Systems: The Difference Between Hydraulic Pumps And Motors

In the context of hydraulic pumps, a motor pump or combustion engine will generate mechanical energy. This mechanical energy is important, as it’s the exact type of energy the hydraulic engine needs to perform some of its functions. However, it cannot be generated in the exact position it’s needed within a hydraulic system. As a result, mechanical energy is constantly converted back and forth from fluid energy. This solves the issue, as fluid energy is easier to move through its pressurised fluid form.

Hydraulic pumps and hydraulic motors are both required to facilitate this conversion. The hydraulic pump compresses the mechanical energy into fluid and pushes it where it needs to go. The hydraulic motor then converts pressure energy from within the fluid back into mechanical energy and uses it to serve its function.

Conclusion

Overall, hydraulic pumps and hydraulic motors are both existentially required for many hydraulic machines. They are the main drivers for hydraulic systems, with their energy conversion capabilities being key for proper, specific functions.

If you’re looking to get your hydraulic pumps or hydraulic motors repaired, why not contact the experts in hydraulic repairs at CJ Plant at 01527870793.

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