What is a Screw Compressor?

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  • Written By: Alexis W.
  • Edited By: Heather Bailey
  • Last Modified Date: 05 November 2019
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A screw compressor, also often referred to as a rotary screw compressor, is a gas compression unit that utilizes two opposing-threaded screws as a way to force air into a sealed chamber. These two screws, often referred to as rotors, have spaces between the threads and the threaded taps where the gas is pushed into the threads. This causes the air to travel with the thread as it spins inside its chamber. As the gas is pushed through the thread, it becomes compressed in the chamber.

There are generally two types of screw compressors. The first type of rotary screw compressor is most often called the dry screw compressor. It gets this name because it doesn’t utilize any lubricated seal in its function or within any of its chambers.

With both male and female rotors in the dry compressor unit, the compression is determined and maintained accurately through the use of a series of timing gears. These timing gears are imperative to the function of the dry-running screw compressor because any variance in the screws’ operation can result in the failure of the compression system. The allowances within the threads that create the compression rely heavily on the stability and maintenance of the timing of the screws’ operation.


The second type of rotary screw compressor is referred to as an oil-flooded unit. It has this name because the chamber that houses the two rotors is completely filled with lubricating oil. This lubricating oil is the dividing force between the two opposing rotors, or screws, and serves two functions within the unit.

The first purpose of the lubricating oil is to create a hydraulic seal in between the two rotors as they perform their functions. This is imperative because the rotors must be precise in their movements, meaning there cannot be any allowances for air or other gases to escape from the rotor’s threads. The second function the lubricating oil serves is with the compression it provides with its weight; it acts as a mechanical force in the opposition of the rotors as they spin.

The most typical applications for both types of rotary screw compressors occur in industrial and construction fields. The dry compressor is most often used in larger applications such as industrial facilities which utilize compressed air systems. The oil-flooded compressor units are often used in smaller applications on construction sites to power air-powered construction tools.


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