In the vacuum pump, as the medium to obtain vacuum, the vacuum pump oil also plays the role of lubrication, cooling and sealing for mechanical friction. Therefore, the vacuum pump has certain requirements for the performance of vacuum pump oil. What are the specific requirements?

1. Very low vapor pressure

This is the most important performance of vacuum pump oil. Since vacuum pump requires high vacuum degree, paraffin based narrow distillate lubricating oil is generally used. For diffusion vacuum pump, silicone oil with low vapor pressure or other synthetic oil can also be used.

2. Suitable viscosity and good viscosity temperature characteristics

The volume of vacuum pump cavity changes constantly and forms exhaust effect, which requires that the lubricating oil should have appropriate viscosity and viscosity temperature characteristics.

3. Good thermal oxidation stability

Vacuum pump is developing to high speed. The high-speed friction between sliding vane and pump body makes oil temperature rise and oil is easy to oxidize and decompose. Especially, diffusion pump is often in a high temperature environment, which increases vapor pressure in the system and reduces vacuum degree. Therefore, good thermal oxidation stability is required for vacuum pump oil.

4. Good corrosion resistance and oxidation resistance

If the gas inhaled by the vacuum pump is corrosive, it will react with the oil and corrode the internal parts of the pump; the water vapor condensate often exists in the air, which will cause the emulsion of the vacuum pump oil and corrode the metal, so it is required to have good anti-corrosion and anti emulsifying properties.

5. High flash point requirements

The vacuum pump does not carry light components to avoid affecting the saturated vapor pressure of oil.

6. Lower limit pressure

Limit pressure is an important performance index of vacuum pump oil to understand the limit pressure of vacuum pump under the lowest vacuum limit pressure.