In the process of using orbital hydraulic motor, what are the reasons for wrong operation?

In my work, customers often complain that the performance of the motor is not good. However, for those questions, after analysis, it is found that it is very common that orbital hydraulic motors are used improperly in practice, resulting in poor performance or damage of the motor.

I.installation

(1).The mounting and fixing support of orbital hydraulic motor should have enough rigidity.When the system has pressure impact, the motor is not allowed to vibrate, since it is easy to damage the motor.

(2).The output shaft of the motor shall be coaxial with the center line of the coupling connected.

(3).When the oil inlet and return of the motor are steel pipes, the stress of the pipeline should be completely removed, and the pipeline force is not allowed to act on the motor. When connecting the oil drain pipe, the oil return resistance should be less than 0.3MPa, and it should be connected into the oil tank separately, and it should not be connected in series with other oil return pipes. If the oil return resistance (back pressure) is too high, the technical performance of the motor will be deteriorated.

(4).After the motor is installed, fill the motor housing with clean hydraulic oil from the two oil ports before starting.

(5).The radial load on the motor output shaft should not exceed the specified value, otherwise it will affect the reliability of the motor and shorten its service life.

(6).When the motor is put into operation for about 200 hours, the oil should be changed and the oil filter should be cleaned.

II.system design

(1).The intermittent working pressure of the motor refers to the maximum allowable working pressure at the oil inlet of the motor, and the continuous working pressure refers to the pressure difference between the oil inlet and the oil return.

(2).It is not allowed to use the motor at the maximum speed and pressure at the same time.

(3).Under the condition of intermittent operation, the running time of motor shall not exceed 10% per minute.

(4).The maximum oil temperature is 80 ℃.

(5).Generally speaking, the shaft seal assembly used in orbital motor can withstand high working pressure. However, in order to obtain good service life and comprehensive mechanical performance, it is recommended to use back pressure no more than 5MPa. If it exceeds 5MPa, it is recommended to connect the external drain pipe. And when connecting the external drain pipe, it should ensure that the motor can always be filled with oil. In addition to maintaining a low back pressure, connecting the drain pipe can also take away the wear pollutants generated in the motor and produce a certain cooling effect.

(6).There should be a running in period before the motor works at full load. It is recommended to run in for 1 hour below 30% of the maximum working pressure.

 The ideal performance and service life of the orbital hydraulic motor largely depend on the hydraulic oil used.Viscosity is one of the most important performance indexes that should be considered when selecting hydraulic oil. The choice of viscosity should always take into account: the oil must be thin enough to facilitate flow. But at the same time, it must be thick enough to facilitate the sealing and keep a layer of oil film between the bearing and the sealing surface.

(1).Viscosity and temperature

 Oil temperature affects its viscosity.Generally speaking, when the oil temperature is high, it becomes thinner and its viscosity decreases; conversely, when the oil temperature is low, its viscosity increases.When selecting the oil, the start-up and normal operation temperature of the hydraulic system should be considered, this point is extremely important. When the hydraulic system starts to work, the oil is generally thick. With the operation of the system, the oil temperature rises until the cooling system starts to work.From this time on, the oil should be kept at the design temperature of the hydraulic system. In practical application, this situation changes, because the working environment of the hydraulic system varies from high temperature to low temperature.The cooling system varies from complex to simple, and the external temperature will also affect the operating temperature of the system. The recommended oil is 46# anti-wear hydraulic oil, and the viscosity under working conditions is not less than 37-73 CST.

(2).Cleanliness

 The cleanliness of oil in hydraulic system is very important. The oil used in orbital hydraulic motor shall be kept in accordance with ISO cleanliness standard 19 / 16 of SAE J1165, which allows that the number of particles with diameter greater than 5 μ m in each milliliter of oil shall be less than 2500 pcs, and the number of particles with diameter greater than 15 μ m shall be less than 80 pcs.

(3).Maintenance of hydraulic oil

  For all hydraulic systems, it is essential to maintain acceptable viscosity and cleanliness.Since orbital hydraulic motor is widely used, we can't consider every application scenario very carefully. Field testing and monitoring is the only way to obtain the accuracy of cleanliness.

IV.points for attention

(1).If the oil is too thick, the pump will be damaged by cavitation when starting in cold weather, but there is no cavitation problem for the motor.

(2).When selecting hydraulic oil, all components in the system should be taken into account and adjusted properly to obtain the best viscosity range.For example, when a medium plunger type oil pump is connected with a cycloid stator rotor motor, the optimal viscosity range becomes 100-150sus [20-32 CST], and the viscosity must not be less than 70 sus [13 CST].

(3).If the oil turns black, there may be overheating.

(4).If the oil becomes emulsified, there may be water pollution.

(5).When the system is very cold, pay attention to the liquid level indication.