Compressed air is the fourth utility. Along with gas, electricity, and water, it is essential to most modern industrial and commercial operations. It runs tools and machinery, provides power for material handling systems, and ensures clean, breathable air in contaminated environments. It is used by virtually every industrial segment from aircraft and automobiles to dairies, fish farming, and textiles.
A plant's expense for its compressed air is often viewed only in terms of the equipment. Every cost, however, represents as much as 70% of the total expense in producing compressed air. As electricity rates escalate across the nation and the cost of maintenance and repair increases, selecting the most efficient and reliable compressor becomes critical.
Basic operation of a rotary screw compressor
Rotary screw compressors operate on the principle of positive displacement. Filtered air enters the inlet of the airend where male and female rotors un-mesh. The air is trapped between the rotors and the airend housing. This space is reduced as the rotors re-mesh on the opposite side of the airend. Thus, the air is compressed and moved to the discharge port. Cooling fluid injected into the housing mixes with the air to seal, lubricate, and remove the heat generated by compression. This fluid forms a thin film between the rotors that virtually eliminates metal-to-metal contact and wear. The fluid is separated from the compressed air, cooled, filtered, and returned to the injection point. The compressed air passes through an aftercooler to reduce its temperature and is ready for the air treatment equipment.