What is Compressor CFM and how do I use it?
CFM is the most common unit of measurement for the discharge air volume from a compressor over a period of time. It’s based on volume/time, as you might have guessed.
What is CFM?
CFM stands for Cubic Feet Per Minute. A compressor can produce a certain amount of compressed air per minute (CFM), from its discharge port.
You will need to know the maximum cubic feet per minute that your compressor can deliver when you use compressed air in your home or plant. This will tell you if your compressor can supply enough compressed airflow to power any air-consuming equipment or tools.
You need to understand the CFM required for a device or tool to work within its design parameters. To function properly, the device or tool must have a set number of CFM and a particular air pressure.
The rule of thumb is that each 1HP motor produces approximately 3-4 CFM compressed air flow at 90 PSI.
CFM to HP – Rule of thumb
Or, the equivalent of 1 CFM to 0.25 HP at 90 PSI.
Air Compressor kW – CFM Calculation (rule by thumb)
The rule of thumb is that every 1 kW compressor power produces approximately 4-5.5 CFM compressed air flow at 90 PSI.
Or, the equivalent of 1 CFM to 0.18-22.5 kW at 90 PSI
One exception to the rule
The industry standard for air production per motor HP is 10 HP, but it is not applicable to compressors smaller than 10 HP. To determine the flow and pressure rates of compressors less than 10 HP, it is necessary to consult the specifications or to use the “guest” of 2-3 CFM discharge flow at 90 PSI per HP of electric motor.
After you have sized your applications and accumulated all the air you will need for now and future plant growths, you can start looking for the right compressor. Divide the CFM requirement by 4 to get an idea of the horsepower rating.
What about S-CFM
SCFM is another unit you will be familiar with when it comes to compressed air, and especially compressed air tools. To help you understand the differences between CFM and SCFM, I recommend my article. It’s beyond the scope of this article.
CFM differs among manufacturers
Different compressor manufacturers have different ways of evaluating their compressor output. A compressor might show a discharge rate that is acceptable, but closer inspection will reveal that it was based on a lower pressure than what you might require.
CFM discharge rates at higher pressures are generally lower than those at lower pressures for the same compressor.
You should ensure that the unit you choose has the CFM and pressure you require to function properly.