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Choosing your hydraulic motor

How do you choose the right hydraulic motor?

When you consider the hydraulic components, there are different types of hydraulic motor. Obviously, each piece of hydraulic equipment has its own particularities in terms of the arrangement of its internal moving parts. However, whatever the model chosen, the role of a hydraulic motor is always to convert hydraulic energy into mechanical energy. To help you make the right choice for your application, let's take a look at hydraulic motors.

What is a hydraulic motor?

A hydraulic motor is a device that converts hydraulic power into mechanical energy by means of hydraulic pumps. Hydraulic power is supplied by a fluid under high pressure. In other words, this energy is generated by the rotary movement of the output shaft.

In order to stimulate the hydraulic system, the motor has two characteristics, namely the motor torque and the speed of rotation. If the resistive torque is too high, the hydraulic pressure will rise. Once it reaches the pressure relief valve setting, the flow is transmitted to the tank. The advantage of the torque motor is that it develops high power in a smaller footprint.

Hydraulic motors are needed to guarantee rotary movements in environments where there is a risk of explosion and where temperatures are too high for traditional solutions.

What are the different types of hydraulic motor?

There are 4 different types of hydraulic motor:

  • Vane motors,
  • Radial piston motors
  • And gear motors.

Each motor has its own characteristics and performance.

The vane motor

All hydraulic motors have their own operating principle, based on their direction of rotation. What makes the vane-type hydraulic motor special is its components, which enable it to deliver high-performance starting torque. In fact, the vane motor has built-in springs that give it the power it needs to start rotating.

Gear motor

This type of motor is more affordable than the vane motor. In fact, the geared hydraulic motor is very popular. Its main advantage lies in its speed and simplicity. To keep the pump running, the gear motor has a drive wheel that turns under the effect of pressure exerted on the hydraulic fluid by the gear pump. However, the disadvantage of this type of hydraulic motor is its somewhat high efficiency.

Radial piston motor

There are 2 types of radial piston hydraulic motor: the radial piston motor and the axial piston motor. The first operates in odd numbers and turns on a cam. The second, on the other hand, turns through the pressure of a ball joint. Be aware that these engines are slow, but with satisfactory efficiency.

What faults can these motors encounter?

Hydraulic motors are identical to all hydraulic valves. In fact, these hydraulic devices can also break down. These malfunctions can be :

  • Aeration, which is characterised by the presence of air bubbles in the hydraulic fluid.
  • Contamination, which occurs when a foreign body is introduced into the fluid.
  • Cavitation, which occurs when the fluid no longer occupies all the space inside the pump.
  • Internal leaks in the hydraulic circuit due to difficulties in regulating the pump.

How does a hydraulic motor work?

Hydraulic motors work in the same way. The difference lies mainly in the pressure between the inlet and the bearing, and in the dimensions. There are also differences in the internal moving parts that are mechanically connected to the coupling shaft. Under the effect of the pressure difference, these internal moving parts move and cause the motor shaft to move. Regardless of the difference, the hydraulic motor emits a rotational movement to a load. In other words, the hydraulic energy obtained from the pressurised fluid is converted into mechanical energy.

How do I choose the right hydraulic motor?

Like spare parts, you also need to choose the right hydraulic motor. Obviously, you need to choose the right motor for your hydraulic pump. In any case, here are a few points to bear in mind:

  • Type of application ;
  • Maximum and average power to be allocated;
  • Output shaft speed and torque spectra;
  • External loads;
  • Installation options, weight and expected service life;
  • Efficiency ;
  • Weight/power ratio;
  • Hydraulic maintenance.

Whether slow or fast, motors have a volumetric efficiency. For production systems that require fairly high performance, you can opt for different engines such as axial piston or inclined shaft engines. The latter have a power rating of up to 500 kW, a torque of 160 daN.m and a speed range from 50 to 300 rpm. These motors offer good performance and greater efficiency.

On the other hand, for production lines that do not require high speeds but rather good robustness, motors with axial pistons and double plates are recommended. These hydraulic systems have a power rating of up to 250 kW, a torque of 1,000 daN.m and a pressure of 250 bar. They offer a wide range of speeds and greater efficiency.

For very low speeds, radial piston engines are recommended, particularly in rotating barrel technology. This type of motor has a speed range from 5 to 500 rpm. They can also deliver power of up to 350 kW, with torque of 650 daN.m and pressure of 450 bar.

Finally, for applications on agricultural machinery, public works or sweepers, we recommend choosing the orbital hydraulic motor. This requires a lower speed and comes in several types depending on the speed of rotation and maximum torque capacity.

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