Basic knowledge of air compressor oil: indicators, functions, service life

1. Important indicators of oil products

A. Flash point: The temperature at which the flame flickers within three seconds when the oil is in contact with the flame. The higher the better

B. Ignition point: the temperature at which the oil is ignited. The higher the better

C. Viscosity: At 40 degrees Celsius, the oil flow rate is generally No. 46 for screw air compressors, and only a few air compressor brands use No. 32, such as Kobelco, Hitachi and Sullair in the United States. To test whether the oil is oxidized or whether it has reached the end of its service life, it depends on the change of viscosity. Generally, mineral oil should not exceed 15%. If it exceeds too much and is used for a long time, it will gel or carbonize.

D. Viscosity index: The index of the viscosity of the oil product due to temperature changes. The higher the better, as the index of mineral oil is generally within 120.

E. Pour point: The lowest temperature of the oil when it keeps flowing. The lower the pour point, the better. For example, the pour point of mineral oil is around minus 19 degrees — 21 degrees. For example, in the cold northern regions of our country, the temperature is low in winter, and the pour point of mineral oil is high. The air compressor cannot be started, and the air compressor must be heated before it can be started. If synthetic oil is used, such problems will not occur.

F. Density: It is the specific gravity, the general oil is about 0.85, except Sullair’s SULLBUE32# and Ingersoll Rand’s super coolant is about 0.99

G. Acid value: The new oil will not exceed 0.09. If the old oil is used in the air compressor, impurities, iron filings, and acidic substances will increase the acid value of the oil, which will also accelerate the oxidation of the oil, such as the acidity of the oil If the value exceeds 1, it means that the oil is highly polluted and it is recommended to replace it.

O. Oil classification: Mineral oil (first-stage hydrogenation, dewaxing, distillation and other processes are called Class I base oil; secondary processes are called Class II; the best three-stage process is called Class III, which is called semi-synthetic in China Oil is still classified as mineral oil in foreign countries. The real semi-synthetic oil should be a type III base oil with more than 20% synthetic ester added to be called semi-synthetic oil. Synthetic oil (polyalphaolefins referred to as PAO, ester Synthetic oil is referred to as POE, ether synthetic oil is referred to as PAG, etc.)

P. Composition of lubricating oil products: base oil and additives (antioxidants, anti-emulsifiers, anti-rust agents, defoamers, viscosity modifiers, dispersants, high-temperature resistant esters, etc.) are blended into products.

2. The role of air compressor oil in the air compressor

A. Cooling: The air compressor will generate a lot of heat when it is working, and the oil will play the role of heat.

B. Lubrication: The oil forms a protective film on the metal surface to reduce wear and tear. The oil film of No. 46 is thicker than that of No. 32 oil, especially when it is cold start, it can better protect the metal surface.

C. Sealing: The lubricating oil in the compression chamber of the screw host can reduce leakage.

D. Sound reduction: reduce the noise when the host is running

3. Air compressor oil service life

A. The service life of air compressor oil is mostly determined by the type of base oil. Imported mineral oil generally needs to be replaced within 3,000 hours of use. The service life of semi-synthetic oil is within 6,000 hours, and synthetic oil can be used for 8,000 hours. hours to 16000 hours.

B. The service cycle set by the air compressor oil manufacturer is generally the standard working condition of the air compressor (clean air, operating temperature within 95 degrees, normal operation of the air compressor, etc.), and harsh working conditions will shorten the service life of the oil. life.

C. In the aftermarket, it is necessary to understand the oil history of the air compressor. If there is any problem with the previous oil product or the oil product used is not a regular brand, please inform our engineers to handle it properly. Because the inferior oil oxides will remain in the machine, seriously affecting the service life of new oil.

4. Common problems of air compressor oil

A. Gel: The base oil of air compressor oil is not good, and there are many ash impurities in it. These substances are easily oxidized. Through the oxidation reaction of high temperature and air, they will form sludge like asphalt. In severe cases The head of the air compressor is locked, and the general precursor of gelation is that the compressed air becomes smelly and the operating current of the air compressor is high.

B. Carbonation: Under the high temperature operation of the air compressor, especially after exceeding 95 degrees, the light and heavy components of the oil will be separated, and after oxidation, they will be adsorbed on the surface of the parts like varnish, which will block the oil fine separator, and the oil seal of the machine head will wear and leak oil, the bearing life is shortened.

C. Oil emulsification: The air compressor runs at low temperature for a long time, the water in the machine cannot be evaporated in time, and the oil and water are mixed and emulsified into a milk-like liquid.

D. The oil content of the air outlet is high: the oil-gas separation of the oil is poor, and there are more hydrogenated compounds in the base oil, which makes it difficult to separate from the compressed air.

E. Abnormal color of old oil: Normally, the color of the oil will turn dark red or black, but if it turns purple or other colors, it means that the oil additives are used improperly, and it is recommended to replace the oil in time.

F. Too much foam in the oil product: usually the proportion of oil defoamer added is not appropriate, sometimes it will lead to insufficient oil return and affect the service life of the machine bearing.

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