Avoid air entering the hydraulic cylinder system. The oil used in the system has little compressibility, and it can be considered as incompressible under normal circumstances. However, the compressibility of air is great, so even if the system contains a small amount of air, its impact is also great.

The air dissolved in the oil will escape from the oil at low pressure, producing bubbles and forming cavities. In the high-pressure area, under the action of pressure oil, these bubbles are quickly broken and compressed sharply, causing noise in the hydraulic cylinder system. At the same time, when the gas is suddenly compressed, it will release a lot of heat, causing local overheating, accelerating the rise of oil temperature, and damaging components and oil. The high compressibility of air will also lead to crawling and other faults of working devices, which destroys the stability of work and sometimes produces vibration.

To avoid air entering the system:

1. The oil suction pipe and oil return pipe should enter below the oil level and maintain a certain length;

2. All parts of the system should be kept full of oil by installing a one-way valve at the outlet of the hydraulic pump and setting a back pressure valve on the oil return path;

3. The oil level of the oil tank should be as large as possible, and the suction side and the oil return side should be separated by diaphragms to remove bubbles;

4. Vent holes shall be set at higher places of pipelines and equipment, and the air shall be discharged during startup;

5. Keep the pipe joint well sealed. If the seal is not good, air will be sucked into the hydraulic cylinder system.