The leakage of hydraulic pumps refers to the leakage of hydraulic oil. In work engineering, almost all hydraulic pumps will have similar problems. The appearance of hydraulic pumps will not stop machinery and equipment immediately, but it will reduce the volume of hydraulic pumps. Reduce the operating efficiency, and limit the increase of the rated pressure of the hydraulic pump.

The main reason for the leak: Because most of the relative moving parts in the hydraulic pump are sealed with a gap seal, when the hydraulic pump is operating, the high-pressure oil in the pressure chamber must flow through this gap to the suction chamber and other low pressure places, resulting in leakage. Therefore, controlling leakage and reducing leakage are one of the basic conditions to ensure the normal operation of the hydraulic pump. The condition of hydraulic pump leakage is the existence of clearance and pressure difference, and the amount of leakage is proportional to the third power of the clearance value and proportional to the first power of the pressure difference. The analysis of pump leakage mainly starts from the three aspects of seal gap size, gap pressure difference and whether the movement increases the leakage.

Because the machining accuracy of the annular gap between the plunger and the cylinder bore is easy to control, and other gaps are easily compensated, the volumetric efficiency and rated pressure of the plunger pump are high. The main leakage gap in a vane pump is the end face gap between the rotor and the flow plate, followed by the gap between the vane and the rotor blade slot, and between the vane top and the stator inner ring. In order to reduce leakage, some medium and high pressure double-acting vane pumps design the flow plate as a floating type to realize automatic compensation of the end face gap.

The main leakage gap of the plunger pump is the annular gap between the plunger and the cylinder bore, followed by the end face clearance between the axial plunger pump cylinder and the distribution plate, and the planar clearance between the shoe and the swash plate. For radial piston pumps, in addition to the annular gap between the plunger and the cylinder bore, there is also the radial gap between the cylinder and the distribution shaft, and the gap between the shoe and the stator inner ring. Clearance, meshing gap between two meshing gear teeth. The end gap of the medium and high pressure gear pump is compensated by an automatic floating compensation mechanism.

For external gear pumps, the main clearance is the end surface clearance between the gear end face and the front and rear pump covers or left and right side plates, followed by the radial direction between the tooth top and the inner circle of the pump body.