According to statistics, 70% of hydraulic component failures are related to hydraulic oil, and about 90% of these 0% are caused by impurities. The main points to check for hydraulic oil are: cleanliness, color, viscosity and consistency; in addition, there is odor. When hydraulic oil from the high-pressure side to the low-pressure side without performing mechanical work, heat is generated within the hydraulic system. High temperatures in hydraulic oil can cause expensive seals to deterior and oil to oxidize to failure, can cause corrosion and the formation of deposits, which can block damping holes and accelerate valve wear. Excessive temperature can also cause valves and to seize up, and high temperatures in hydraulic components can also lead to safety issues. By checking the oil temperature in the tank, system failures can sometimes be eliminated before serious harm occursIn most systems, the pressure relief valve is the main source of heat generation, and excessive flow through the pressure reducing valve of hydraulic components is also another major cause of heat. Since low efficiency is related to energy loss, checking the operating temperature can reveal whether there is a problem with low efficiency. For hydraulic systems, the control of pollutants in oil is a major task. The sources of pollutants in hydraulic components mainly include the following:1. Entering with new oil.2. Internal to the during assembly.3. Entering with the surrounding air.4. Generated by internal wear of hydraulic components.5. Entering through leakage or damaged seals.6. Introduced during maintenance.