Different Rotary Compressor Options
While the rotary screw air compressor is the most common rotary style compressor found today, there are other types of rotary compressors that are available. While reciprocating compressors utilize pistons to create the compressed air, rotary compressors uses a variety of different components to produce the compressed air based on the compressor technology.
The first and most common style is the rotary screw air compressor. With oil lubricated rotary screw compressors, oil is positioned in the space between the rotors, which provides the necessary seal for compression. Many times, there are single and two stage models to choose from. Single stage compressors the air is compressed once, where in two stage compressors the air is compressed twice for double the pressure.
When speaking about fixed or variable speed models, variable means it was designed to handle inconsistent demand for air and can fluctuate up or down with reduced energy consumption. Fixed speed compressors are at a constant flow and are typically more efficient with a consistent demand.
Rotary vane compressors operate with vanes that product centrifugal force as the rotor spins. As air enters in it is trapped between the vanes as they move, reducing the volume and raising the air pressure. With oil lubricated rotary vane compressors, the oil is between the vane and housing which assists with premature wear on the vanes. The simple and proven design of rotary vane compressors make them popular in terms of reliability and easy maintenance.
With scroll compressors, there are two spiral shaped scrolls, one stationary and one mobile, which produces the compressed air by pressing against the stationary scroll to trap and compress the air. Scroll compressors are most commonly found in medical, pharmaceutical, food, beverage and lab applications. Their low maintenance needs and energy efficiency, along with their quiet operation make them a common consideration when evaluating a rotary compressor.
Fixed versus Variable Speed
Fixed rotary compressors run at one, fixed speed regardless of the compressed air demand. The compressor will never ramp up or down as far as producing more or less air, it will always operate at a constant capacity.
Variable speed compressors will increase or decrease the output of compressed air based upon the demand. The benefit of variable speed compressors is they are energy efficient which translates into cost savings.