Requirements for hydraulic oil performance of grader

In hydraulic transmission, hydraulic oil is both a medium for transmitting power and a lubricant. It also acts as a seal in some components. The heat in the system is also diffused through the oil, so it also plays a heat dissipation role. Therefore, in order to ensure that the hydraulic system works reliably, effectively and economically, the hydraulic oil must meet the following requirements:
1) Appropriate viscosity. Viscosity refers to the magnitude of the friction resistance between molecules when the oil flows. When the viscosity is too large, the resistance to oil flow is large, the energy loss is large, and the system efficiency is reduced. In addition, the no-load loss of the main engine increases, the temperature rises quickly and the operating temperature is high, and the "cavitation" phenomenon is easy to occur at the suction end of the main pump. If the viscosity is too small, the good lubrication conditions of the hydraulic components cannot be guaranteed, the wear of the components is aggravated, the leakage increases, and the efficiency of the hydraulic system is also reduced.
2) Good viscosity-temperature characteristics. The viscosity-temperature characteristics refer to the degree to which the viscosity of the oil changes with temperature, usually expressed by the viscosity index. The larger the viscosity index, the smaller the decrease in the viscosity of the oil with the increase in temperature during the operation of the hydraulic system, so that the internal leakage of the hydraulic system will not be too large. The viscosity index should generally not be lower than 90.
3) Good anti-wear and lubricity. The purpose is to reduce mechanical friction and ensure sufficient oil film strength under different pressure, speed and temperature conditions.
4) High chemical reaction stability, not easy to oxidize and deteriorate. Practice has shown that for every 10°C increase in oil temperature, its chemical reaction rate increases by about one time. Hydraulic oil with good anti-oxidation stability is not easy to oxidize and deteriorate after long-term use, which can ensure the normal circulation of hydraulic oil.
5) The quality should be pure, and the content of mechanical impurities, moisture and dust should be minimized.
6) The impact on seals should be small.
7) Good anti-emulsification and not easy to cause foam. Anti-emulsification refers to the ability of oil to not become an emulsion after mixing with water and stirring, and the ability of water to separate from it. Anti-foaming refers to the ability of oil to not generate an emulsion after mixing with air and stirring, and the ability of bubbles to separate from the oil. After mixing with water or air, the volume modulus of hydraulic oil is reduced, the compressibility is increased, the hydraulic components are slow to move, and it is easy to produce shock and vibration.
8) Good anti-rust performance. Hydraulic oil covers the surface of parts to prevent them from being oxidized and rusted.
9) Good shear stability. In order to improve the viscosity index of the oil, high molecular polymers such as polymethyl methacrylate and polyisobutylene are often added to the oil. These substances have long molecular chains. When the oil flows through the slits of hydraulic components, it is subjected to a large shearing effect, which often causes the molecular chains to break and the viscosity-temperature characteristics of the oil to decrease.
10) The ignition point and flash point should meet the ambient temperature, and the volatility should be small to ensure the safety of hydraulic oil.