Compare RECIPROCATING COMPRESSORS or PISTON COMPRESSORS. A reciprocating compressor can be oil free or oil inject. The reciprocating piston compressor is the original method for compressing gases.

The volume of the piston limits the volume of compressed air produced. But, the air pressure from the reciprocating piston compressor can be very high. When air pressure in the 8 to 35 atm (120 to 540 psi) or higher, is required, the piston, or reciprocating, compressor is the answer, The plastic bottle industry has set the standards for the reciprocating compressor industry.

Oil free and oil injected designs are available. The oil free compressor uses water for cooling. This will require a stronger air drying system at the output end of the compressor. The oil inject compressor will have less friction and, at such, require less maintenance. Also, the oil gives a tighter seal giving these models higher pressure capacity.

The air coming from single piston or dual piston compressors, single stage, has pulsation from when the piston releases the compressed air. For these compressors an air storage tank is recommended. Not only does the tank dampen the pressure pulses, it also provides cooling of the air plus the opportunity for oil and water droplets to settle.

To obtain very high air pressure, some dual compressors have the output of one piston feed the input of the second piston.

Capacity FAD is the measure of free air delivery as measured at the input of the compressor