Several Key Factors of Air Compressor Oil

Lubricating oil is crucial to a compressor’s normal operation. It has five functions of cooling the compressing chamber, Sealing to Increase Compressing Efficiency, Lubricating and Reducing Frictions, Reducing Noises and Avoiding Corrosion.

 

1. Pour Point

 

Pour point is the lowest temperature that the lubricating oil could flow. Under any temperature below the pour point, the lubricating oil will freeze.

The pour point of Comair lubricating oil is -40℃, far lower than the industrial standard of -9℃.

 

2. Kinematic Viscosity

 

Kinematic viscosity is about the friction force between lubricating oil molecules. Or simply we can understand it as the lubricating oil stickiness.

The industrial standards of kinematic viscosity 41.4-50.6 mm2/s at 40℃.

 

3. Viscosity Index

 

The higher the viscosity index, the more stable the lubricating oil is at different temperatures.

 

At high temperature, the oil viscosity will decrease and the oil will become thinner. With higher viscosity index, the oil is more difficult to become thinner and thus more difficult to become oil vapor, which is good to lower oil content in compressed air.

 

The required viscosity index of lubricating oil in compressor industry is >90. For Comair lubricating oil, it tested viscosity index is 124.

 

4. Flash Point

 

Flash point is the lowest temperature at which the lubricating oil will generate sufficient oil vapor to flash when exposed to a source of ignition or fire.

 

The higher the flash point is, the better the lubricating oil. Normally the discharged air temperature at the air end is over 110℃ and there might be static spark inside the compressor, so the required flash point for lubricating oil is usually above 200℃.

 

Above all, the other factors may also have large influence on lubricating oil performance including carbon deposition tendency, oxidation resistance, emulsification resistance, and foam resistance.

 

For oil injected screw air compressor and diesel portable air compressor, the lubricating oil directly mix with compressed air. The followings shall be further considered when choosing the lubricating oil:

 

The lubricating oil does not chemically react with the compressed air.

 

The dissolution of compressed air in lubricating oil and the dilution functions.

 

Because the lubricating oil constantly undergo heating and cooling process, it is required to keep suitable viscosity degree for a long time and to maintain superior performance of oxidation resistance, anti-corrosion and rust protection etc.