The rotary screw air compressor is one of two main categories in the air compressor industry, with the other being reciprocating piston compressors. The rotary screw, also known as helical rotary compressor, does not use values, instead it using positive displacement pumps to generate flow by applying an expanding cavity on the suction side of the compressor and a decreasing cavity on the discharge side.

The rotary screw compressor is usually deemed the quieter compressor, it is lighter than the reciprocating compressors, is pulsation-free, maintains efficiencies over the operational time of the compressor, as there is no direct contact of the rotors. It is primarily used in commercial or industrial applications and was originally placed into service back in the 1950’s.

Within the rotary screw housing will be the two rotors, with a clearance between them and the housing is typically .003 inches to .005 inches. There are two types of rotary screws compressors as well…those which are oil-free and dry rotors. In the case of the oil-free version, the male rotary, or drive rotor, is connected through a shaft and driven by an electrical engine. The female rotor is driven by the male rotor through a thin film of oil. In the dry version, there is a set of timing gears to help achieve proper rotation.

Here is a little more about how this type of compressor operates…a void is created as power is applied due to the male and female rotors separating from one another. This void is filled by gas through a tiny inlet port. As the male rotor returns, it starts compressing the gas filled space, pushing it to and through the discharge port. This process then turns the screws of the compressor as the compression is isolated and focused onto the housing walls. The rotary screws are cooled and lubricated via lubricant which is automatically injected in to the housing through another small port.

Here is where you can also track quality and difference models during your price comparison. Some of the rotary-type compressors have a variable discharge value, which continuously seeks maximum efficiency by only opening and closing the respective ports based on pressure, rather than a static, full opening and closing regardless of pressure. The basic operation is simple; when there is less air demand, the discharge value allows the air to cycle back through the inlet without begin compressed. The efficiency here is that the rotors are not subjected to a full-length operation, decreasing the power used in one respective cycle and reducing wear on the system at the same time.

Tagged with: rotary screw air compressor

Filed under: Quiet Air Compressors