In the field of equipment lubrication, it is necessary to keep lubricating oil clean and control pollution well. The air also causes the "pollution" of lubricating oil. The lubricating oil can not only contain water, impurities or other oil liquids, but also avoid containing air, whether it is the foam on the oil surface or the bubbles contained in the oil. The reasons for air mixing in lubricating oil are complex. Sometimes it is not necessarily the problem of oil itself. Therefore, adding anti-foaming agent or changing oil can not solve the fundamental problem.

Bubbles and foam are harmful to lubricating oil and machinery, and bubbles will accelerate the oxidation deterioration rate of lubricating oil, accelerate consumption of additives, affect heat dissipation, and not form a complete lubricant film, causing wear and tear to equipment. Bubbles also cause local high temperatures in high-pressure systems, causing rapid deterioration of oil. In addition, air is easy to compress, there is gas in lubricating oil, oil film thickness will become thinner or even oil film rupture, direct friction between mechanical components, resulting in wear and tear. When bubbles burst under pressure, the metal surface will also be damaged by cavitation. In addition, bubbles can also cause instability of equipment operation.