The term ‘pressure’ in relation to air compressors may have an obvious meaning to experts in compressed air, but others who are new to the industry may not fully understand exactly what it means. Keep on reading for a simple explanation which will hopefully bring your confusion to an end, once and for all.

Air compressors work by converting air into a type of force or power. This is achieved when the compressed air is released from a small environment, back into the atmosphere. The build up of air inside the compressor creates a high level of pressure, which, when released, has varying amounts of force to be used for different applications. The level of pressure is measured using pounds per square inch (psi) or bar.

It is important to create the right amount of pressure to comply with the application. If the pressure is too weak when it is released, then the application will not work efficiently. However, if the pressure is too powerful, it could damage or wear out the equipment; or could even prove to be highly dangerous.

Are you new to the world of compressed air? If you have been hearing terms about the volume of air in an air compressor and getting a bit confusing then these explanations should clarify the differences. The key difference is that displacement is a theory and free air delivered is the actual volume of air.

1. Displacement (volume)
This is the theoretical volume of an air compressor. This is the swept volume of a cylinder multiplied by the number of compressions per minute. This is released in cubic feet per minute (CFM). Do not get the displacement calculation confused with working out the size of air compressor needed.

2. Free Air Delivered
This is a more accurate way of estimating the volume of air that is available. The free air delivered is the volume of air which can be entered into the air compressor. This is released at a specific pressure as CFM/FAD.