1. Solid particle pollution: often causes valve clamping, increased leakage, filter blockage, oil oxidation, etc. Practice has shown that solid particles between 5-15 μ m are most likely to cause valve clamping; 10-30 μ m particles can cause wear on power components; The oil distribution plate of the axial piston pump is sensitive to solid particles of 10-15 μ m; Radial pumps and motors are sensitive to particles ranging from 15 to 25 μ m; The vane pump is sensitive to particles of 20-30 μ m;

2. Water pollution: Oil contaminated with water often corrodes metals and reduces lubrication;

3. Air pollution: Air pollution often causes hydraulic system delay, cavitation, oil oxidation, etc. When the air content exceeds 2% (up to 8% to 10%), the oil begins to become turbid. The amount of air dissolved in hydraulic oil depends on the type of hydraulic oil, working pressure, and temperature.

1. On site assessment of hydraulic oil quality based on appearance;

2. On site oil droplet clamp judgment on fine filter paper (spot method);

3. On site identification of hydraulic oil test items;

4. The laboratory conducts regular sampling and testing.

1. Fixed cycle oil change method: refers to the method of replacing hydraulic oil after six months, one year, or 1000-2000 hours of operation. This method is widely used, but not very scientific;

2. On site identification and oil change method: determined based on the usage of the oil on site. Generally, online particle counters and portable particle counters are used for sampling and detection;

3. Comprehensive analysis of oil change method: taking oil samples for experimental analysis to determine, this method conforms to the principle of oil change and is relatively the most scientific.

1. Keep the surrounding environment clean and install dust-proof devices at the interface of hydraulic components;

2. Air filters should be installed on the ventilation holes of the fuel tank, and the fuel level should be controlled at 2/3 of the tank height. The bottom of the fuel tank should be cleaned regularly;

3. Strengthen the management of hydraulic oil, select suitable hydraulic oil, and filter it when refueling;

4. Regularly clean the fuel tank and use an external filtration device to purify the oil regularly;

5. Regularly check the integrity of the heat exchanger;

6. Choose a suitable oil filter and regularly clean or replace the filter element;

7. Regularly sample and inspect the quality of hydraulic oil (using an oil particle counter for testing), and handle or replace the oil as appropriate.

8. Prevent the mixing of new and old oil or the blending of different grades of oil.