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Faults Causes and Removal Methods of Gear Hydraulic Motor
Views: 118 Update Date: Dec 21 , 2018

Hydraulic gear motor is a kind of hydraulic motor. It has simple structure, high output speed and good anti-pollution performance. What will happen when it breaks down?

The following faults will occur when the hydraulic gear motor is in use:

1. Oil Seal Leakage: The reasons for oil seal leakage are: first, the back pressure of the oil drain pipe is too high and the oil drain pipe is not smooth; second, the quality of motor shaft seal (oil seal) is not good, or the choice is wrong, or the oil seal is damaged and oil leakage.

The exclusion methods are as follows:

(1) The drain pipe should be brought back to the oil pool separately, instead of sharing with the hydraulic motor return pipe or other return pipe;

(2) When the pipeline path is blocked by dirt or too small in design and bends too much, it should be disposed of to make the pipeline unobstructed.

2. Excessive noise, accompanied by vibration and heat

The reasons are as follows:

(1) Air is introduced into the system and into the gear hydraulic motor.

(2) The reasons of the gear motor itself are as follows: poor gear profile accuracy or poor contact; too small axial clearance, etc.

The exclusion methods are as follows:

(1) Clean the oil filter to reduce oil pollution;

(2) Make every effort to eliminate the vibration and noise caused by the radial unbalanced force and the axial unbalanced force of the gear hydraulic motor.

3. Reasons for the decrease of rotational speed and torsion torque are as follows:

(1) The insufficient oil supply of the hydraulic oil pump, the increase of wear and radial clearance, axial clearance, or the mismatch between the motor and power of the hydraulic oil pump, causes the insufficient oil output and the decrease of the flow into the gear hydraulic motor.

(2) The pressure regulating failure pressure of hydraulic system pressure regulating valves (such as relief valves) is not high, and the leakage of control valves is large, which results in insufficient flow and pressure entering the hydraulic motor.

(3) When the oil temperature rises, the oil viscosity is too small, resulting in large leakage in each part of the hydraulic system.

Exclusion methods:

(1) Eliminate the fault of insufficient oil supply of hydraulic oil pump, such as cleaning oil filter, repairing hydraulic pump, ensuring reasonable axial clearance, replacing motor which can meet the requirements of speed and power, etc.

(2) Faults of control valves in clearance, especially relief valves, should be checked for the reasons of pressure regulation failure, and targeted elimination;

(3) Choose oil with appropriate viscosity to reduce oil temperature;

4. The lowest speed of gear motor is unstable and has creeping phenomenon.


(1) When air is mixed into the system, the bulk modulus of elasticity of the oil, i.e. the rigidity of the system, will be greatly reduced.

(2) The back pressure of the hydraulic motor is too small to install the back pressure valve, and the air is injected back into the gear hydraulic motor from the oil return pipe.

(3) The poor connection between the gear motor and the load leads to large coaxiality error, which makes the gear hydraulic motor subject to the action of radial force, resulting in the increase of the sealing clearance between the high and low pressure chambers of the internal oil distribution part of the motor, the increase of internal leakage, and the increase of flow pulsation. At the same time, coaxiality error will also cause uneven friction between the relative moving surfaces and cause creeping phenomenon.

Exclusion methods:

(1) Preventing air from entering hydraulic motors;

(2) Installing a back pressure valve at the oil return part of the hydraulic motor and adjusting the back pressure properly can prevent the acceleration forward of the gear motor when it starts and compensate for the change of the motion resistance, so that the total load is uniform and the motor runs smoothly, which is equivalent to improving the rigidity of the hydraulic system.

(3) Attention should be paid to the coaxiality between the hydraulic motor and the load to minimize the creeping phenomenon caused by the eccentric wear of the hydraulic motor spindle caused by the radial force and the uneven friction between the relative moving surfaces.

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