The rotary screw compressor uses rotors (helical screws) to compress air. When the rotors start turning, air is drawn in on one side and becomes trapped between the rotors and the casting. Since the rotors are continuously turning, the air gets compressed to the opposite end and fresh air is drawn in.
These compressors are made to run 24 hours a day, 365 days a year. The duty cycle of screw compressors is generally much longer than that of piston-type compressors.
This type of compressor is usually the best choice when you need continuous air in a workshop or factory. The rotary screw compressor is available in oil-injected and oil-free versions.