The three basic types of industrial air compressors
Reciprocating air compressors
This type of air compressor is classified as a positive displacement machine meaning it increases the pressure of air when reducing its volume. This is accomplished by the reciprocating air compressor through a piston within a cylinder as the compressing and displacing element. Single-stage and two-stage reciprocating compressors are available in the market to suit your specific requirements. Single-stage compressors are used generally for pressures in the range of 70 psig to 100 psig while two-stage compressors are used for higher pressure in the range of 100 psig to 250 psig. Psig is a measure of pressure meaning pound/square inch (gauge). It is important to note that industrial air compressors with 100 horsepower and above are typically rotary screw or centrifugal compressors.
Rotary screw air compressors
The most common rotary screw air compressor is the single stage helical or spiral lobe oil flooded screw air compressor that consists of two rotors within a casing where the rotors compress air internally. There are no valves and the units are basically oil cooled with air cooled or water cooled oil coolers where the oil seals the internal clearances. The rotary screw compressor has several advantages over other industrial air compressors like ease of maintenance and operation. Since cooling takes place inside the compressor, the working parts do not experience extreme operating temperatures. It also includes smooth, pulse-free air output in compact size with high output volume for a longer service life.
Centrifugal air compressors
This type of industrial air compressor is best suited for applications where demand is relatively constant. The three-stage centrifugal air compressor is generally more efficient than rotary screw types and can approach the efficiency of double-acting reciprocating air compressors. Being a dynamic machine, air is compressed through mechanical action of high speed rotating impellers that impart pressure and velocity into the air. By design the centrifugal air compressor is oil-free and the oil lubricating running gear is separated from the air by shaft seals and atmospheric vents.
Although choosing among the different types of industrial air compressors can be quite intimidating, a bit of knowledge on how they work can make the choice a lot easier. It is no different when you are buying a new car where you exert all efforts at doing research to come up with an investment that is worth your money.