Screw Compressors
A screw compressor, also referred to as a rotary screw compressor, is an air compressor in which the air is compressed between two intermeshing, counter-rotating
screws contained within a specially shaped chamber. As the mechanism rotates, the movement of the two rotors produces an area of air that steadily condenses in volume. As the compression of air continues, the reduced pockets of air are discharged through another area of the chamber. Screw compressors are ideal for large industrial applications because of their ability to provide continuous output over a long period of time. Screw compressors are commonly used for a variety of applications among construction, manufacturing, agriculture, food and beverage, mining and automotive industries. They are also utilized in air tools, woodworking, pharmaceuticals, natural gas and
plastics production.
The effectiveness of screw compressors requires minimal space between the rotors and the air chamber so that the compression areas are properly sealed. Often, oil is used to facilitate this process and aid in sealing. The oil is then separated from the discharge stream, cooled, filtered and recycled. It is usual for some entrained compressor oil to carry over into the compressed gas stream and gradually seep into the surrounding air. Oil-free screw compressors complete the air compression process without the aid of oil for cooling and sealing. The downside of oil-free screw compressors is that they have lower discharge pressure capability, but they are useful in situations in which oil carry-over cannot occur, like in a hospital. Although they may be more costly initially, screw compressors have also been said to require less maintenance and have longer operating lives than other air compressors of comparable size.