A hydraulic motor is an actuator that converts the hydraulic energy output by a hydraulic pump into mechanical energy. In theory, hydraulic motors and hydraulic pumps are reversible, and their structures are basically the same. Their fault diagnosis and elimination can refer to the methods of hydraulic pumps. However, in practice, hydraulic motors and pumps of the same type have structural differences due to their different purposes of use. In order to identify the cause of the malfunction, it is necessary to understand the differences between the two.
The low-pressure chamber of a hydraulic pump is generally vacuum. In order to improve oil absorption performance and anti cavitation ability, the inlet is usually made larger than the outlet. The pressure in the low-pressure chamber of the hydraulic motor is slightly higher than atmospheric pressure, so there is no such requirement.

Firstly, let's take a look at the issue of insufficient output speed or decreased power of blade type hydraulic motors. This may be caused by various reasons, including insufficient oil supply from the hydraulic pump, insufficient outlet pressure of the hydraulic pump, loose or poorly sealed joint surfaces of the hydraulic motor, blade jamming due to contaminants or burrs, excessive sliding clearance between the rotor and the oil distribution plate, fatigue failure of the oil distribution plate support spring, wear and tear on the inner curved surface of the stator, and wear or blockage of the one-way valve seat and steel ball in the blade type hydraulic motor. To address these issues, we can take corresponding troubleshooting measures, such as adjusting the oil supply, increasing the outlet pressure of the hydraulic pump, tightening the joint surface and checking the sealing condition, removing burrs and contaminants on the blade edges and rotor slots, grinding and polishing the rotor and stator end faces, checking and replacing the support spring, and polishing the inner surface curve of the stator.

The physical properties of hydraulic fluid include multiple basic properties, and we will now introduce three of them that are closely related to hydraulic transmission performance.
（1） The mass of a liquid per unit volume of density is called the density of the liquid, which is the density of the p-liquid in the equation P=m \ v; V - the volume of a liquid; M - the quality of the liquid. The density values of commonly used hydraulic transmission fluids are shown in Table 2-2. Table 2 Density of commonly used hydraulic transmission fluids (20 ℃) Hydraulic fluid density/(kg. m-3) Hydraulic fluid density/(kg. m-3) Anti wear hydraulic fluid L-HM32 Anti wear hydraulic fluid L-HM46 Water in oil emulsion L-HFB Water in oil emulsion L-HFAE 0 87 x l03 0.  875 x l03 0.  932 x l030.  9977 x l03 water ethylene glycol hydraulic fluid L-HFC universal phosphate hydraulic fluid L-HFDR aircraft phosphate hydraulic fluid L-HFDR No. 10 aviation hydraulic oil 1 06 x l031.  15 x l031.  05 x l030.  The density of 85 x l03 liquid changes with pressure or temperature, but the amount of change is generally small and can be ignored in engineering calculations.

Disassembly steps and installation instructions for hydraulic motors:
The clearance between each motion pair of the motor has been properly matched, and users are not allowed to replace parts arbitrarily. In general, do not disassemble the motor at will. Only in the event of a serious malfunction can it be disassembled and inspected with the consent of our company.
（1） Preparation before disassembly
Remove the drain plug and drain the oil from the motor housing.
Loosen the 5 screws on the oil pan and remove the oil pan.
3. Remove the oil distribution plate, positioning ring, cushion block, cylindrical pin, and double headed key.
Attention: To prevent changes in rotation direction after reassembly, it is necessary to mark the output shaft end face and oil distribution plate face in the same direction.
（2） Disassembly and assembly sequence
Remove the cover, screw clean screws into the center screw hole of the crankshaft, and lift out the crankshaft.
Remove the snap ring from the connecting rod.
3. Remove the assembly of the plunger body connecting rod and make corresponding marks one by one, so that the original clearance can still be ensured during reassembly. Generally, users can inspect and repair the plunger body and connecting rod by disassembling them here. If necessary, the assembly of the plunger body and connecting rod can be disassembled: loosen the hole with a spring retaining ring, remove the retaining ring, and the plunger body and connecting rod can be separated.
Assemble according to the reverse procedure above, paying attention to ensuring the axial clearance of the bearings.
Before assembly, all parts must be cleaned to prevent scratches or bumps on any working surface.
If only the sand hole of the plunger sleeve leaks oil or the joint surface between the plunger sleeve and the housing leaks oil, the screws on the plunger sleeve can be loosened, the plunger sleeve can be removed, and the plunger sleeve or "O" ring can be replaced.
Common problems with hydraulic motors, root cause analysis, and troubleshooting methods