Air Compressor Glossary & Terms

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Here are a few terms related to air compressors and a definition for each, a mini dictionary, air compressor vocabulary.

Glossary

ACFM (Actual Cubic Feet per Minute): The actual volume of air delivered to the system, accounting for pressure, temperature, and humidity.
Aftercoolers: A heat exchanger that cools compressed air after it leaves the compressor to remove moisture.
Air Dryer: A device that removes moisture from compressed air to prevent corrosion and contamination.
Brake Horsepower: The total power required to compress and deliver a quantity of air, including voltage and mechanical losses.
Centrifugal Compressor: A type of air compressor that uses an impeller to energy to the air, thus increasing the pressure. Also known as a dynamic compressor. Typically used in large facilities using 500hp+ of compressed air with a continuous demand.
Check Valve: A device that allows fluid or air to flow in only one direction.
Coalescing filter: A specific type of filter that not only works to remove dust and particles from the air, but also oil vapors and other liquid contaminants. They are typically found downstream from the compressor and the air treatment components.
Compression Ratio:: The ratio of the pressure at the discharge to the pressure at the inlet.
Cubic Feet Per Minute (CFM): A measure of airflow - The volume of air that is able to pass through an opening in one minute.
Desiccant: A material used with air compressors and air dryers that helps to remove water vapor from the air. Desiccants are typically used to reach low dew points that are not achievable with refrigerated dryers.
Dew Point: The temperature at which air becomes saturated, when vapors start to condense into liquid
Drain Cock: Used to release accumulated moisture from the compressor tank (Also see drain valve).
Drain Valve: A drain valve works to remove surplus liquid from the compressor. There are manual, float and electronic drain valves available. They are typically installed at the compressor tank, aftercooler, receiver tank, dryer and filters.
Dryer: Compressor tanks are made of steel, when water gets into the tank, the tank can rust thus reducing the life of the tank. Dryers help reduce the moisture the gets into the tank.
Dual Stage: Compressors where air is compressed from initial pressure to an intermediate pressure in one or more cylinders and then compressed to a higher final pressure in another cylinder or cylinders.
Duty Cycle: The percentage of time a compressor runs versus rests during a complete cycle.
Filter Efficiency: The rate of which a filter can remove particles from an air flow.
Filter housing: Cover which protects the filter assembly.
Free Air Delivery (FAD):: The amount of air a compressor delivers at atmospheric conditions (similar to CFM and ACFM).
Horsepower (HP):: The measure of power the compressor motor uses to operate.
Intercooler: A heat exchanger between compression stages to reduce temperature before the air is compressed again
Kick-in Pressure: Factory set low pressure point of the pressure switch that starts the compressor to re-pressurize the receiver.
Kick-out Pressure: Factory set high pressure point of the pressure switch that stops the compressor from increasing the air pressure in the receiver.
Load Time: The time it takes for a compressor to go from load to unload.
Load/Unload Control: A control system that allows the compressor to run without compressing air when demand is low. This is more efficient than starting and stopping the motor.
Low oil shutoff: A feature which shuts off the compressor motor if the pump runs low on oil, preventing damage or failure.
Oil free compressor: Air compressor that has no oil inserted into the compression chamber for lubrication, cooling or sealing.
Pneumatic: Related to the movement of air.
Pneumatic power: Compressed air power.
Point of use: An outlet in a building used to connect tools or equipment to the air compressor system.
Pounds Per Square Inch (PSI): A unit of measurement referring to the pressure applied on one square inch of an object's surface.
Pressure Switch: An instrument which senses a change in pressure and automatically adds or decreases air in the tank.
Preventative Maintenance (PM): A maintenance program performed on a fixed schedule that includes compressor service as well as routine inspection of other system components.
Purging: The elimination of undesired gas or liquid from a system. Often times associated with a desiccant air dryer to refresh the desiccant material.
Receiver: A storage tank that holds compressed air and reduces pulsations in the system.
Reciprocating Compressor: A reciprocating compressor uses pistons driven by a crankshaft to deliver air at high pressure. Ideal for intermittent use applications.
Refrigerated Air Dryer: An air dryer that removes moisture from the compressed air by cooling it and draining the condensate that is formed.
Rotary Screw Compressor: A compressor which utilizes two intermeshing helical rotors to trap a volume of air, then compress it from one end of the rotors to the other.
Safety valve: A valve which limits fluid pressure by releasing some of the pressurized liquid or gas. a.k.a. Pressure Relief Valve.
SCFM (Standard Cubic Feet per Minute): Airflow measured under standard conditions (14.7 psi, 68°F, 36% RH).
Single Stage: A compressor in which the air is compressed from initial pressure to final pressure in one step.
Start/Stop Control: The motor turns on/off based on system pressure. Most commonly associated with piston and reciprocating compressors.
Unloader: A valve that is between the compressor pump and tank. It opens when the compressor stops, that "psss" you hear when a compressor stops.
Vacuum Pumps: A vacuum pump is a compressor that operates with an intake pressure below atmospheric and discharge pressure at or slightly above atmospheric.