Technical Article

Performance requirements and improvement measures of hydraulic oil

(1) Proper viscosity and good viscosity-temperature characteristics of hydraulic oil

Excessive viscosity will increase the loss of viscous resistance; The suction performance of the pump deteriorates, it is difficult to start, and even cavitation occurs; Control sensitivity drops.

Too low viscosity will increase leakage and decrease volumetric efficiency; Decrease in control accuracy; The liquid lubricating film becomes thin, and even unable to form liquid lubrication, which increases the wear.

Hydraulic oil can increase viscosity index and improve viscosity-temperature characteristics through additives. Such as polyisobutylene, polymethacrylate, etc.

(2) Good anti-wear properties (lubricity)

Wear resistance is a kind of performance that has nothing to do with viscosity, but is achieved by adding additives to the oil to form an oil film to reduce wear.

By adding oily additives and extreme pressure anti-wear additives to the hydraulic oil, the hydraulic oil forms a physical or chemical adsorption film on the metal surface. This film is also called a boundary film. The boundary film forms boundary lubrication and prevents direct contact with the substrate, which is beneficial Reduce friction and wear.

(3) Good oxidation stability and thermal stability

Oxidation stability refers to the ability of oil to resist oxidation. When the oil is affected by heat, oxygen, water, and metal substances, it will oxidize to produce organic acids and polymers. The color of hydraulic oil becomes darker, acid value increases, viscosity changes, and precipitation substances are formed. Therefore, the corrosiveness of the hydraulic oil increases, thereby blocking the small holes of the hydraulic components and increasing wear. Thermal stability refers to the ability of oil to resist chemical reactions and decomposition at high temperatures. The high temperature of the oil will accelerate the cracking and polymerization, and the metal surface will also act as a catalyst. Therefore, hydraulic oil must withstand a certain high temperature and avoid working at extremely high temperatures.

Generally, the oxidation stability and thermal stability of hydraulic oil are improved by adding antioxidants.

(4) Good demulsibility and hydrolytic stability

The ability of oil to resist mixing with water to form an emulsion is called demulsibility. The ability of oil to resist decomposition by chemical reaction with water is called hydrolytic stability.

Water can cause corrosion, accelerate oil deterioration, destroy oil film and reduce the lubricity of hydraulic oil. Adding a demulsifier can improve the demulsibility of hydraulic oil.