Environments such as medical offices, food processing plants, tattoo shops, clean room environments, research laboratories, public buildings and critical manufacturing lines require air that is 100% clean of microscopic oil particles that can contaminate both the equipment and the product. If the air output of oilless air compressors contains any oil in the air, no matter how small the amount, it is unacceptable for these environments.
Generally more reliable, oilless air compressors can be used in industries requiring continuous pressurized gas such as metal processing, electronics, semi-conductor, food processing, chemical, industrial, medical, automotive and aerospace. Other types of air compressors include rotary, screw and mini air compressors, all of which may be made oil free. Oilless air compressor manufacturers offer products that may cost more at purchase, but become more economical over time due to higher-energy efficiency as well as increased profit potential.
There are two types of air compressors that are oil free: centrifugal compressors and rotary screw air compressors. While centrifugal compressors are always oil free, rotary screw compressor manufacturers are manufacturing more oil free rotary screw compressors for precision applications in recent years than lubricated rotary screw compressors.
Centrifugal compressors are turbo machines that act as fans, blowers, pumps and compressors to provide high pressure airflow for a number of large industrial applications. A rotary impeller draws air in through the compressor’s inlet, imparting high velocity to the air with rapid rotary motion; the kinetic energy of the air is converted to pressure as the air or gas is channeled into a diffusing chamber and out through a discharge nozzle. Due to the centrifugal compressor’s use of a rotary impeller, they contain no lubricants, which might come in contact with the air stream.
Oil-free rotary screw compressors use two helical screws fitted into one another, rotating quickly in opposite directions. The meshing and rotation of the two helical rotors produces a series of volume-reducing cavities; gas is drawn in through an inlet port in the casing, captured in these cavities, compressed and then discharged through another port in the casing. The design is oil-free because the air is compressed entirely through the action of the screws, without the assistance of an oil seal.