Vacuum Pump Oil Principle

If user don’t understand the principle of vacuum pump oil, user might use oil indiscriminately, hence it will reduce the performance of the pump, and cause malfunctions. Understanding the working principle of the oil, using the oil correctly and knowing how to select the oil correctly is very important.


We know that the vacuum pump oil plays a role of lubrication and sealing for the vacuum pump. If the vacuum pump oil is used incorrectly, it will cause smoking from the exhaust port. The oil plays a vital role for the pump.


In order to save costs, many users use different brand mixed oil or cheap oil. If different oils are used in combination, conflicts will occur due to the different indicators such as the ignition point and vapor pressure of the oil. Cheap oil is used instead, and the performance parameters are not up to standard. Vacuum pump oil is also a factor that directly affects the life of the pump. How to buy vacuum pump oil must first clarify several performance indicators of the pump oil, that is, the principle parameters of the pump oil.

  • The vapor pressure of a qualified pump oil should not be too high.

Vapor pressure is an important parameter for pump oil. It ensures that the vacuum pump can continuously and quickly obtain vacuum and maintain the stability of the ultimate pressure. Pumps with different vacuum degrees have different requirements for the saturated vapor pressure of the pump oil. For ultra-high vacuum or high vacuum pump, the saturated vapor pressure should be lower. Therefore, according to the needs of the pump, user should select the appropriate vacuum pump oil.

  • Instead of buying the most expensive pump oil, buy the most suitable one.

Another performance index is the viscosity of the oil. If the viscosity is too high, the resistance of the moving parts will increase, which will increase the energy loss. If the viscosity is too low, the sealing effect of the oil will be weakened, which will easily lead to leakage and easily deteriorate.

  • Strong anti-oxidation stability.

During the vacuum pumping process, the rotor rotates at a high speed and the temperature rises. The oil is heated and oxidized, decomposed and volatilized, and discharged from the exhaust port, which leads to waste of oil. Therefore, oil with stronger oxidation stability should be selected.

  • Strong anti-corrosion and anti-emulsification performance.

Due to the wide range of pump applications and complex working conditions, some of the pumping gas containing corrosive gas or water vapor, which will chemically react with the vacuum pump oil, contaminate the pump oil, and accelerate the emulsification of the oil. Therefore, the pump oil should have good aviation corrosion performance and anti-emulsifying properties.

  • Oil that has a high flash point.

The flash point refers to the temperature at which the vapor and air mixture on the surface of the flammable liquid comes into contact with an open flame for the first time when a flash occurs. If this temperature is too low, it will affect the saturated vapor pressure.

  • The vacuum pump oil needs to have a lower ultimate pressure.


The above 6 indicators are the interpretation of the principle of vacuum pump oil. After understanding these 6 indicators, you will have a better understanding of pump oil, and have ideas on how to choose suitable pump oil.

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