The Rotary Screw Air Compressor: Basic Types

A rotary screw compressor, also known as a “twin-screw compressor,” is classified as a positive displacement machine. Because it is a low-pressure mechanism – operating only as high as 400 psig discharge pressure, it does not compete against reciprocating compressors for many kinds of industrial applications. Instead, it finds itself meeting the needs of devices where space is premium, and the demand is for a continuous air supply.

Basic Types


Rotary screw air compressors fall into two basic types each with its own advantages and issues.

  1. Oil-free or dry Oil-less compressors: In many processors, the presence of oil contamination is highly detrimental. Increasingly tight regulations are resulting in a greater demand for oil-free or oil-less compressors. As a result, this type of rotary screw compressor is a standard for a variety of industrial/commercial operations including:

a. Medical

b. Lab/research facilities

c. Biotechnology

d. Pharmaceutical companies

e. Food and beverage processors, developers and manufacturers

2. Oil flooded compressors: For more than half a century, air and refrigeration applications have relies on this version of rotary screw air compressor to ensure clean and efficient operations. In the past few decades, this type of compressor has infiltrated the natural gas industry. More recently, oil companies are installing this type of compressor. In fact, some oil and gas companies prefer oil-flooded rotary screw air compressors to the traditionally-used reciprocating types.

Both types are favored for their high airflow delivery as well as their longevity and low maintenance – the result of fewer parts that can wear out or complicate matters.

The Rotary Screw Compressor

When it comes to installing an air compressor, the choices are rotary or reciprocating. When longevity, easy maintenance, and continuous airflow are expected – the only choice is a rotary screw compressor. The only other decision is whether an oil-free or oil flooded types are best in serving the specific industrial application.