Compressor oil is used to lubricate, prevent wear and corrosion, and improve compression efficiency. It varies in viscosity and additives, and can be natural or synthetic. Anti-wear additives reduce metallic contact, and correct viscosity reduces gas escape. Synthetic oils have better stability and can be used in oxygen compressors. Oil-free systems are required for safety and sensitive equipment. Synthetic oils are becoming more popular due to specific characteristics and longer life.
Compressor oil is a lubricant used to prevent wear, minimize metal corrosion and improve compression efficiency. Oils vary in thickness or viscosity, the types of additives used, and whether they are natural or synthetic oils. They can circulate with the gases in compression, as in air conditioning systems, or be separated, as in oxygen compressors.
Wear resistance is important because many compressors run continuously and can wear out quickly without proper lubrication. Chemicals called anti-wear additives reduce metallic contact of moving parts. The correct viscosity, or thickness, of compressor oil is important because the oil acts as a sealant and reduces the amount of gas that escapes around the compressor pistons, called blow-by.
Synthetic compressor oil is made from artificial lubricants rather than natural petroleum oils. Different molecules are blended to provide wear protection, adequate viscosity and high temperature stability. Compressors for oxygen and other gases that can cause combustion can use synthetic oil because blends that do not burn in the presence of oxygen can be used.
Many systems, such as those used for air conditioning and refrigeration, circulate oil and refrigerant through the system as a mixture. Compressor oil provides lubrication while it’s inside the compressor, but it’s not stored there. Moving lubricant through a system can provide cooling to the compressor, as hot oil will be cooled in heat exchangers before returning. These systems may also be less expensive to manufacture, because no additional equipment is required to keep the oil separate.
Oil-free systems are required for locations where the presence of compressor oil can cause a fire or contaminate the gas supply. These systems are used to compress pure oxygen, and are also used to breathe air for both safety equipment and scuba diving. Sensitive laboratory instruments may also require oil-free air supplies to prevent equipment damage.
Maintaining oil levels in some systems is essential to long life. Most refrigeration systems are sealed and only require oil maintenance if a leak occurs. Larger refrigeration systems and commercial gas compressors may use an oil supply tank, where compressor oil is stored until it is needed by the system. This allows you to add replacement oil without having to shut down the compressor.
Since the late 20th century, synthetic oils have become more popular for some compressor systems. This was largely due to the ability to create or formulate specific oil characteristics for industrial, medical and consumer uses. Synthetic oils were sometimes more expensive, but better oil stability allowed them to stay in compressors for longer periods before needing to be changed. This could result in lower costs for the oil itself and lower labor costs for maintenance.
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