What Is a Rotary Screw Compressor?

Manufacturers typically classify compressors into two types: rotary screw and reciprocating/piston. Both serve the same purpose in pressurizing air for industrial use but differ in the mechanics of how they do it and, to a lesser extent, the specific applications they’re best suited for.

While many reciprocating compressors are still in use today, they employ an older technology that requires additional maintenance and doesn’t perform as well at higher pressures. As a result, rotary screw models have largely replaced them as the compressor of choice for most heavy-duty applications.

Screw Compressor Working Principles

Rotary screw compressors feature a pair of interlocking rotors in a sealed chamber. These rotors turn continuously during operation. Air enters the chamber through an inlet valve and, as it does, suction forces it into the space between the rotors. There, the rotating screw mechanism reduces the volume of the air and ejects it when it reaches a specified pressure.

To deliver the appropriate pressure and volume of air, compressor rotors must be manufactured to tight tolerances, and machines must be capable of maintaining carefully controlled operating speeds. However, when a well-designed rotary screw compressor is sized appropriately for the task, it’s one of the most efficient options on the market today.

Advantages and Applications

One of the main benefits to using a rotary screw compressor is that they have a 100-percent duty cycle — in other words, unlike reciprocating models, which will overheat when run for too long, screw compressors can operate continuously. Because a screw compressor incurs less wear and tear, it will deliver a longer service life with fewer maintenance requirements.

As a result, rotary screw compressors offer excellent value for heavy-duty industrial applications. Typical users include manufacturing facilities, autobody and auto repair shops — where production may require the continual use of multiple air tools at once — and oil and gas plants, which often need highly pressurized air for various processes.

How to Choose the Right Screw Compressor

Rotary screw air compressors range in size and capability. The simplest models feature a single screw, though most commercial-grade units feature two or more. The main factors to consider when assessing a rotary screw compressor include:

  • Pressure: Manufacturers rate the pressure of the air output from a compressor in pounds per square inch gauge (psig). Most air tools run at 90 psig, while cleaning, manufacturing and packaging tasks often require higher pressures.
  • CapacityCapacity, measured in CFM (cubic feet per minute) refers to the volume of compressed air that a machine can output at a given pressure. A higher CFM rating means that a compressor can run more tools or processes at once.
  • Horsepower: Horsepower refers to the size of the motor driving a rotary screw compressor — it’s not necessarily reflective of its psig or CFM rating, though more powerful machines do require a more powerful motor. As a general rule of thumb, an efficient compressor should be able to produce at least five CFM of 100 psig compressed air per unit of horsepower.

Kaishan Compressor manufactures a wide range of rotary screw compressors for virtually any application. Explore our inventory by browsing our website, or contact a representative directly for assistance.

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