Vacuum pump oil is a special lubricating oil for vacuum obtaining equipment. It is one of the important materials of vacuum pump. The oil quality directly affects the ultimate pressure, pumping rate, back pressure and oil return rate reached by the equipment. In the vacuum pump, the vacuum pump oil not only acts as a medium for obtaining vacuum, but also lubricates, cools and seals the mechanical friction points. According to the working conditions of the oil in use, vacuum pump oil can be divided into mechanical vacuum pump oil, steam jet pump oil, vacuum sealing oil, etc.

Performance requirements of vacuum pump oil:

(1) Very low vapor pressure

This is the most important performance of vacuum pump oil. Since the vacuum pump requires the vacuum degree to be below 0.000133Pa, the evaporation of the vacuum pump oil is required to be extremely low. For general vacuum pump oil, paraffin-based narrow-cut lubricating oil is used. For diffusion vacuum pump, silicone oil or other synthetic oil with very low vapor pressure can also be used. The saturated vapor pressure should be lower than the ultimate pressure indicated on the pump nameplate.

(2) Viscosity and viscosity-temperature characteristics

The volume of the vacuum pump cavity is constantly changing to form the exhaust effect, which requires that the lubricating oil should have appropriate viscosity and viscosity-temperature characteristics.

(3) Thermal oxidation stability

The vacuum pump is constantly developing at high speed. Due to the high-speed friction between the sliding vane and the pump body, the oil temperature rises, and the oil is easily oxidized and decomposed. In particular, the diffusion pump often works in a high temperature environment, which increases the vapor pressure in the system. Reduced vacuum. Therefore, the vacuum pump oil is required to have good thermal oxidation stability.

(4) Corrosion resistance

If the vacuum pump sucks in corrosive gas, it will chemically react with the oil to corrode the parts inside the pump. On the other hand, the inhaled air often contains water vapor condensate, which can cause the emulsification of the vacuum pump oil and cause the metal to corrode. Therefore, the oil is required to have good corrosion resistance and demulsibility.

(5) Anti-emulsification

During the operation of the vacuum pump, the water and cold gas in the system will be discharged into the pump oil, and the oil and water will form an emulsion, which not only affects the service life of the pump oil, but also deteriorates the ultimate pressure. Especially in the process of vacuum drying for industrial applications such as medicine, food, and ceramics, the emulsification resistance of vacuum pump oil is more important. Good emulsification resistance, strong oil-water separation ability of pump, water vapor and condensed gas are discharged through needle valve.

(6) Flash point

It should not only be considered from the aspect of flammability and safety, but mainly requires that the vacuum pump does not carry light components, so as not to affect the saturated vapor pressure of the oil.

(7) Water separability

It can quickly separate the water entrained in the oil to achieve the required vacuum degree.