Many industrial air compressors come in self-contained packages, which include the drive motor, inlet filters, and other optional accessories. The package may be mounted on an air receiver depending on the size and type of the air compressor. Best Garage Air Compressor are classified either as positive-displacement or dynamic. Air is drawn into a chamber, where it is compressed by mechanical means. This causes the pressure inside to rise, forcing the air into the system. A simple example of a positive-displacement compressor is the hand pump for inflating tires. The operating principle for positive-displacement compressors is either reciprocating or rotary. A reciprocating compressor is a piston that moves in an enclosed cylinder. Single-acting compressors produce air by compressing only one side of the piston. Double-acting compressors create compression on both the piston and crankshaft revolutions. This doubles the power of a single-acting compressor with identical stroke and bore. The compressor can be either air-cooled or water-cooled, lubricated, or unlubricated in any case.
One or more cylinders are connected in parallel in single-stage reciprocating compressors. They compress air from the atmospheric pressure to the final discharge in one step. Single-stage compressors can discharge up to 100 psig. Multi-stage reciprocating compressors on the other side have multiple cylinders connected in series. Each stage adds a degree of compression. In a 2-stage unit, for example, air is compressed at atmospheric pressure to an intermediate pressure in the first stage. Then, it is cooled by an intercooler, and then raised to discharge pressure in the second.
Multi-stage reciprocating compressors run more efficiently, are cooler, and last longer than single-stage compressors. This is because intercoolers remove heat from compression. Although not usually used for plant air, some two-stage compressors are capable of producing 250 psig and more. Air-cooled single-acting reciprocating compressors have either one or two stages, and can produce up to 150 horsepower. In most industrial applications, however, the maximum size of a reciprocating compressor is usually 30 horsepower. Specific power is a measure of operating efficiency. It is either the kW required to produce 100 cfm or the kW/100 cm. The specific power of a single-stage single-acting compressor is approximately 24kW/100 cfm at 100psig. The typical specific power of a single-stage, two-acting compressor at 100psig is between 19 kW/100 cfm and 21 kW/100 cfm. Water-cooled double-acting compressors can range from 25 HP (single stage) to 500 HP. The most common sizes for industrial applications are between 75 hp to 250 hp. The most efficient air compressor is a two-stage reciprocating compressor. At 100 psig, the typical specific power is between 15 kW/100 cmfm and 16 kW/100 cfm. Double-acting compressors are more expensive to install, have higher maintenance costs and cost higher than other types.