Here is a list of common terms that relate to air compressors and how an air compressor functions



Vacuum pumps are machines for compressing air or gas from an initial pressure which is below atmospheric  to a final pressure which is near atmospheric.

Reciprocating air compressors are those in which each compressing element consists of a piston moving back and forth in a cylinder.

Rotary air compressors
are those which utilize two intermeshing helical rotors to trap a volume of air, then compress it to a higher pressure.

Single Stage Air Compressors are those in which compression from initial to final pressure is complete in a single step or stage.

Two Stage Air Compressors are those in which compression from initial to final pressure is completed in two distinct steps or stages.

Intercoolers are devices for removing the heat of compression of the air or between consecutive stages of multistage air compressors.

Aftercoolers are devices for removing the heat of compression of the air or gas after compression is completed. They are one of the most effective  means of removing moisture from compressed air.

Moisture separators are devices for collecting and removing moisture precipitated from the air or gas  during the process of cooling.

Air Receivers are tanks into which the compressed air or gas is discharged from the air compressor. Receivers help to eliminate pulsations in the discharge line and also act as storage capacity during intervals when the dean

PSIG is pounds per square inch gauge

Absolute Pressure (PSIA) is the existing gauge pressure plus atmospheric pressure. At sea level the gauge pressure in pounds per square inch (PSI) plus 14.7 gives the absolute pressure in pounds per square inch (PSIA).


Dew point is the temperature at which air is fully saturated with water vapor.

Delivery (ACFM) is determined by precisely measuring a voume of air which has been raised to a specific pressure and is expressed in conditions existing at the air compressor discharge. This flow rate is generally stated in terms of actual cubic feet per minute (ACFM).

SCFM represents standard cubic feet per minute. Defined as the characteristics of air at 14.696 PSIA, 60 F and 0% relative humidity, this relates to dry mass flow. SCFM is used to define a bench mark condition upon which the required amount of air to do a given function can be determined to the specific site conditions at which the operation will be undertaken.