A Rotary Screw Air Compressor is a compressor that uses a rotary-type positive displacement mechanism, called a rotary screw, air-end. Rotary Screw Compressors are commonly used to replace piston compressors, in commercial and industrial applications, where large volumes of high pressure air are needed. Another name used (though not frequently) is “twin screw compressor”.
The compression process of a Rotary Screw is a quite different than that of a reciprocating piston compressor, as the Rotary Screw air-end generates compression in a continuous sweeping motion. There is very little pulsation or surging of flow, which occurs with piston compressors. Rotary Screw Compressors also use two inter-twined helical shaped screws, known as rotors, to compress the air. These rotors are precision machined to extremely tight tolerances, whereby the vanes on the rotors are almost touching, and typically just a few thousandths of an inch apart.
In an oil-flooded Rotary Screw Compressor, lubricating oil bridges the space between the rotor vanes, both providing a hydraulic seal and transferring mechanical energy between the driving and driven rotor. Air enters the system at the “suction side” of the air-end and moves through the rotor vanes as the screw rotors rotate. The inter-twined rotors force the air and oil through the air-end, which eventually exits at the end of the screws. The air and oil then go through a separation process. The air is cooled and routed to air lines and a receiver. The oil is also cooled, filtered and re-routed back into the air-end in a closed loop system.