How to correctly size an air compressor

Compressors come in all types and sizes. From massive machines that keep huge production plants running to the small versions that avid do-it-yourselfers are using, there is a compressor for everyone. With so many models to choose from, it is vital you choose the correct one.

Specifying your compressed air system by flow and pressure – not kW or horsepower

The key to sizing your compressor properly is knowing the flow (CFM) and pressure (PSI) requirements for your application. Pressure can be measured in pounds per square inch (PSI), or bar (a metric measure of pressure). Simply, pressure refers to the amount of force needed to perform a certain amount of work at any given point in time.

An air compressor needs to provide enough pressure to perform a given task, anything less than that will not accomplish the task. That is why it is important to understand what pressure is needed for your application in order to size the compressor properly. Otherwise, you either waste energy or run into performance problems.

That brings us to flow. Flow is measured in cubic feet per minute (CFM), litres per second (l/s) or cubic meters per hour (m3/h) depending on where you are located. Flow is the ability of the compressor to continue performing a task within an acceptable time frame or the amount of flow that is required to complete a given task in a certain length of time.

To sum up, pressure is determined by the job being performed. Flow requires the understanding of how frequently the job must be done, or how many jobs are being performed at once. If the compressor is undersized it will result in pressure drops and the inability to complete a task. Oversizing not only wastes energy and increases costs but can lead to future mechanical problems and potential compressor failure.

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