In the hydraulic system, if the pressure somewhere is lower than the air separation pressure at the working temperature of the oil, the air in the oil will be separated to form a large number of bubbles; when the pressure is further reduced to the saturated vapor pressure at the working temperature of the oil , the oil will rapidly vaporize and produce a large number of air bubbles. These bubbles are mixed in the oil to generate cavities, which make the oil filled in the pipeline or hydraulic components into a discontinuous state. This phenomenon is generally called cavitation.

Cavitation generally occurs at the valve port and the oil inlet of the hydraulic pump. When the oil flows through the narrow passage of the valve port, the flow velocity increases and the pressure drops greatly, which may cause cavitation. The installation height of the hydraulic pump is too high, the inner diameter of the oil suction pipe is too small, the oil suction resistance is too large, or the speed of the hydraulic pump is too high, and the oil suction is insufficient, etc., cavitation may occur.

After the cavitation phenomenon occurs in the hydraulic system, when the bubbles flow to the high pressure area with the oil, the bubbles will rapidly burst under the action of high pressure, and the surrounding liquid particles fill the cavity at high speed, and the liquid particles collide at high speed to form local hydraulic shocks. The local pressure and temperature are sharply increased, resulting in strong vibration and noise.

Due to the long-term exposure to hydraulic shock and high temperature, as well as the strong corrosion effect of the gas escaping from the oil, the metal particles on the pipe wall and the surface of the element are peeled off at the pipe wall and the surface of the element near the place where the bubbles condense. The surface corrosion caused by the phenomenon is called cavitation.

In order to prevent cavitation and cavitation, the following measures can generally be taken:

1. Reduce the pressure drop at the small holes and gaps in the flow path. Generally, it is hoped that the pressure ratio before and after the small holes and gaps is p1/p2<3.5.

2. Correctly determine the inner diameter of the oil suction pipe of the hydraulic pump, limit the flow rate of the liquid in the pipe, reduce the oil suction height of the hydraulic pump, minimize the pressure loss in the oil suction pipe, and the pipe joints are well sealed. For high pressure pumps, auxiliary pumps can be used to supply oil .

3. The entire system pipeline should be as straight as possible to avoid sharp bends and local narrow gaps.

4. Improve the cavitation resistance of components.