Info Centre >> Fuel and Lube Oil Technical Manual >> 7. Lube Oil - Test Results >> 7.5 Compressor Oil >> 7.5.1 Air Compressor Oils
Air Compressor Oils
Oil mist fires in compressors are caused by the buildup of carbon from spent lubricant in the air discharge side of the equipment, but may largely be avoided by the use of high quality oils.
Modern synthetic compressor oils are made from chemically-synthesised hydrocarbons (polyalphaolefins), various different types of esters and sometimes severely hydrotreated mineral oils. For some applications, they are also manufactured from polyglycols (materials similar to antifreeze).
Polyglycol fluids are miscible with water and small quantities of water will not affect the operation of the equipment provided it is not salt water. Synthetic lubricants can withstand higher operating temperatures than normal mineral oils and tend to stay within specification for much longer periods. Recommendation of synthetics is largely dependent on the burden placed on the oil by the equipment in use. Both the equipment tolerances and the speed of operation compared to the oil throughput tend to determine the quality of the oil specified.
Compressor oils tend to contain antioxidants in larger proportions than any other oils due to the stress that is put on them by the hot, high pressure oxygen-rich environment they endure. The job of the oil under these conditions is to reduce friction, prevent wear and improve the sealing of the pressure chambers. It must also have a low carbon-forming tendency, as it will be in intimate contact with high-pressure air at high temperatures.