Sany Heavy Industry: Thousands of Questions on Maintenance and Repair: Air Mixed into the Hydraulic System Must Not Be Ignored!

During the process of energy and signal transmission in a hydraulic system, the hydraulic oil is required to have good rigidity and continuity. If air is mixed into the hydraulic system, it will lose its inherent rigidity and continuity, and the stability and reliability of the hydraulic system's operation cannot be guaranteed.

When air is mixed into the hydraulic system, it will cause the following five hazards: 1. The rigidity of the hydraulic oil drops sharply, resulting in a slower response of the hydraulic system, reduced efficiency, and causing the actuator to crawl and vibrate. 2. Bubbles can prevent the formation of an oil film between moving parts, leading to poor lubrication and accelerating the wear of hydraulic components. 3. A certain amount of oxygen in the air will accelerate the oxidation of hydraulic oil and system components. 4. When bubbles are pressurized, they can generate high temperatures, which will cause the hydraulic oil to heat up. 5. The pressure shock generated by the burst of bubbles under high pressure can cause cavitation in hydraulic components. The above five hazards can cause hydraulic system failures and shorten the service life of hydraulic components.

To prevent air from entering the hydraulic system, the following preventive measures need to be taken: 1. If air bubbles are generated during refueling due to inattention and are carried into the oil tank and mixed into the system. Special components should be installed in the fuel tank to reduce the formation of air bubbles in the system. A partition should be set between the return oil pipe and the suction port of the hydraulic pump. A bubble separation net should be installed above the suction oil pipe, which can separate approximately 90% of the bubbles. 2. Air is drawn in due to loose joints or damaged oil seals and sealing rings. The hydraulic system should have good sealing performance. All joints should be firmly fixed and it should be ensured that the oil tank is well sealed. This can prevent outside air from entering and contaminating the system. 3. Air enters the oil suction pipeline and the pipelines of the connecting system due to wear, abrasion or corrosion. The structure of the hydraulic system should be reasonably designed to rationalize the layout of pipeline routing. To keep the pipeline clean and reduce external corrosion. 4. Ensure that the hydraulic oil level in the hydraulic oil tank is higher than the return oil level. If the return oil level is higher than the hydraulic oil level in the oil tank, a large amount of air will mix in. Therefore, the hydraulic oil in the oil tank should not be lower than the lower mark; it is best to be at the middle position. 5. After replacing the hydraulic components, open the exhaust ports of the components. For example, for the main hydraulic pump, you can select an oil port at the highest point to open and add hydraulic oil for exhaust. 6. The breather valve installed on the hydraulic oil tank cover should be inspected and cleaned regularly. Prevent the breather valve from being clogged with dust in the oil passage, which may affect the air discharge from the hydraulic oil tank.