Hydraulic orbital motors are precision mechanisms with tight internal tolerances. Maximizing life, (and avoiding in-service problems), requires installing them correctly, taking care of the fluid, and not expecting them to work outside their design limits. This blog covers seven important tips for their care and maintenance. First though, an exploration of their main features.

Sealing for Pressure

A hydraulic orbital motor works like a pump in reverse. Rather than an input shaft driving a mechanism that produces fluid flow and pressure, flow and pressure generate rotation and torque.

Hydraulic motors take many forms, but the orbital type has a georotor at its heart. A gerotor is a form gear pump where the gears are arranged in a planetary configuration. More specifically, there’s a static outer ring, the stator, with teeth around the inner surface. Inside this ring there’s a second gear with teeth on the outside. This is the rotor and its function is to roll around, or orbit, inside the stator.

The secret to the gerotor is that the rotor has one tooth less than the stator. This results in two parts of the rotor, slightly less than 180° apart, always being in contact with the stator as the rotor orbits.

Dividing the space between rotor and stator into two chambers forms a high pressure side, where hydraulic fluid is delivered, and a low pressure side. The pressure differential creates a moment that turns the rotor. This is linked to an output shaft that turns slowly, thanks to the gearing effect of the teeth, while delivering high torque.

Critical Aspects of Hydraulic Orbital Motors

These motors are so rugged, reliable, and compact that they’re preferred for mobile equipment applications like wheel motors in skid-steers, for scissor lifts, and for a host of agricultural and construction machinery. However, two aspects need close attention:

• Maintaining the rotor-stator seal
• Minimizing side loads, especially impact loads

Careful selection and integration, along with periodic inspection and maintenance, take care of these aspects.

Seven Tips for Extending Hydraulic Orbital Motor Life

1. Size the motor for the application: Hydraulic orbital motors are known for delivering high torque from a small package, but sustained overloading will curtail their life. Determine peak loads during specification and design, and select the motor to suit.
2. Get alignment correct at installation: Misalignment puts side loads on the rotor and bearings, which should always be avoided. Review and follow the OEM installation specifications.
3. Keep fluid flow and pressure with the motor’s operating limits: Flow parameters outside the specified range will lead to speed fluctuations that could be dangerous. Fit pressure relief valves in the hydraulic system to reduce the risk of motor damage.
4. Use the correct viscosity fluid: A motor like those in Impro’s CE medium duty line runs best with fluid that’s in the range of 20 – 43 cSt. Oil that’s too thin will accelerate gerotor wear, while if it’s too thick it will reduce efficiency and speed.
5. Keep the fluid clean: Any contamination will accelerate wear on the gerotor teeth, ultimately leading to lack of pressure and reduced speed and torque. Impro recommends using filters capable of ISO 17-14 cleanliness or better.
6. Don’t let the fluid get too hot: Viscosity drops with rising temperature, and higher temperatures cause expansion of components like the rotor and stator. Impro advises fluid temperature be kept below 85°C (180°F).
7. Inspect periodically: Schedule inspections to look for leaks and abnormal sounds or vibration. If any unusual indications are seen, consider taking the motor out of service so it can be repaired before the damage becomes too severe.

Impro: Your Source for Low Speed, High Torque Motion

Hydraulic orbital motors are tough enough to survive in arduous applications like forestry, construction and agriculture. They won’t last forever though, but with attention to selection, installation and operation, thousands of hours of trouble-free running can be expected.

If you need a source of low speed, high torque rotary motion a hydraulic orbital motor may fit the bill. Contact us to discuss your application and have your questions answered.