What Is The Difference Between The Hydraulic Pump And The Hydraulic Motor?

diesel engine with hydraulic pump

Hydraulic motors and pumps are reciprocal in concept, which means they can be swapped out. However, there are certain structural variances between them due to their distinct objectives of use. The structure of a diesel engine with hydraulic pump is very similar to that of a pump of the same type. The valve distributor hydraulic pump, on the other hand, cannot flow backward, so it cannot be utilized as a hydraulic motor, and there is no valve distributor high-speed motor.

How do you define a hydraulic pump?

A hydraulic pump is a mechanical energy converter that transfers mechanical energy into hydraulic energy. Hydraulic pumps are the most common type of hydraulic pump utilized in hydraulic drive systems. It operates by providing enough flow with sufficient power to overcome the pressure caused by the pump outlet’s load. When a hydraulic pump is in action, diesel engines with hydraulic pumps can be achieved by reducing the pressure, which forces the liquid to flow into the pump from the reservoir via an intake line.

Hydraulic Pumps Types

Hydraulic gear pumps with outside teeth are often the most cost-effective pumps. They have the lowest volumetric efficiency of all pump types, while having a sweeping displacement or volume range of 1 to 200 mm.

When compared to gear pumps, rotary vane pumps, both simple adjustable and fixed displacement, have a higher efficiency; nonetheless, they are only useful for mid-range pressures (180bar). Today’s units can tolerate pressures of up to 300 bar in continuous operation.

Screw pumps are made out of two Archimedes’ screws that come together to form a single chamber. Screw pumps are designed to handle strong flows at low pressures of roughly 100 bar. Screw pumps are popular because they produce little to no noise, however, they are not particularly efficient.

The swashplate technique is used in piston pumps to create both adjustable and fixed displacement devices. They have the design advantage of being compact as a result of this. These pumps are far more cost-effective and easier to construct; nevertheless, one disadvantage is that they are susceptible to oil contamination. Axial piston pumps are the most common variable displacement kind, and they can be used in a wide range of applications, from mobile to heavy industrial.

What is the definition of a hydraulic motor?

A hydraulic motor is a mechanical actuator that converts hydraulic flow and pressure into torque and angular displacement. The moveable part of a hydraulic cylinder is the hydraulic motor. Hydraulic motors can sometimes include devices that can run on hydropower, but the word has been narrowed to exclusively include motors that use hydraulic fluid as part of their closed hydraulic circuits.

Hydraulic motors can be divided into two groups:

Vane and gear motors are simple rotating systems with advantages like high rpm and low beginning cost. A vane motor consists of a housing with an irregular bite that tunes a rotor composed of bands that slide out and in. The way the vane tips have been made to meet the motor housing and the vane tip is an important part of the design. Because they were designed for high-quality rotational drive systems, piston and plunger motors are substantially more complicated. Axial piston and Plunger motors with adjustable transfer ratios are available.

How do hydraulic pumps and motors differ from one another?

You can know these two types of hydraulic components are different just by looking at their definitions. Hydraulic pumps, on the other hand, absorb mechanical kinetic energy to generate hydraulic energy, whereas hydraulic motors do the exact reverse.

While a hydraulic pump is connected to a prime mover by pulleys, sprockets, and gears, the hydraulic motor is connected to the load by pulleys, sprockets, and gears, allowing its main shaft to sustain a greater radial load.

In the low pressure chamber of a hydraulic pump, there is usually a vacuum. Suction nozzles are normally larger than high-pressure nozzles to provide more efficient oil absorption and anti-cavitation capability; however, a hydraulic engine does not require any of these.

Hydraulic motors often require negative and positive rotation, resulting in a symmetrical internal structure. Hydraulic pumps, on the other hand, normally rotate in a single direction, negating the necessity for such a requirement. The blades of a vane motor, for example, must be oriented radially, as opposed to the inclination of a vane pump, or the blades may break when reversed. An asymmetrical distribution plate is required for a diesel engine with hydraulic pump. The same is true for a gear motor, which requires a specific leakage tube that cannot be directly linked to the low-pressure chamber like a gear pump.

A hydraulic motor has a much larger speed range, allowing it to convert from lubricating to hearing mode. A hydraulic motor requires a low minimum steady speed, as well as variable brake and speed in some cases.

To overcome the static friction experienced during start-up, hydraulic motors require a considerable amount of start-up torque. When there is a case of pressure fluctuation, they also require significant start-up torque. This can be achieved with the help of a diesel engine with a hydraulic pump. To reduce internal friction in a hydraulic motor, for example, the number of teeth on a gear motor is increased, and an axial clearance compensating device with a lower compression coefficient than a pump is added.

Hydraulic pumps must be self-priming from the start. One of the reasons point contact plunger motors can’t be utilized as pumps is that they don’t have the ability to self-prime.

The blade of a vane pump is pushed out by centrifugal force, creating a working chamber. If this pump is utilized as a motor, it will not work since the blade is unable to generate the external force needed to start a functional chamber.


Version plunger motors eliminate the slipper to become point contact motors in order to reduce friction, however, plunger pumps cannot function without slippers. A hydraulic motor for diesel engines with a hydraulic pump features a small internal leakage.  The reason for this is that the leaking direction of a hydraulic motor is the same as its motion, causing motion speed to be involved.

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About the Author: Vijay Aegis

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