As a result, if you can reduce the pressure in the tank, the CFM of your compressor will increase. It indicates that if the pressure hits 90 PSI, the compressor will produce 5 CFM of air. When the pressure is reduced from 90 PSI, the air production is greater than 5 CFM. This shows that there is more airflow with less pressure.
CFM is used to indicate the volume of air that a compressor will move per minute. It is calculated by multiplying the speed of the motor (revolutions per minute or RPM) by the cubic feet per minute (CFM). For example, if a compressor runs at 1000 RPM and produces 20 CFM, its CFM rating is 20 CFM. The higher the CFM number, the faster the compressor will move air.
There are two types of compressors: centrifugal and axial-flow. Centrifugal compressors use a spinning metal disk called a impeller to create airflow. Axial-flow compressors use a series of blades attached to a rotating cylinder called a fan. Both types of compressors work on the same basic idea—the movement of air causes it to become compressed, thus reducing its temperature and increasing its density. This is why compressors are needed in any aircraft engine installation to supply breathable air to the passengers and crew.
The amount of power that a compressor uses is measured in horsepower (hp).
A higher PSI means the compressor can store more air in the tank, allowing you to operate air tools longer. Cubic feet per minute (CFM) and standard cubic feet per minute (SCFM) describe the volume of air a compressor delivers at specific PSI levels. As you lower the PSI output, CFM increases. Higher CFM is better for heavy duty use like welding.
The amount of air a compressor can store is limited by how large it's tanks are. The bigger the tank, the more air it can hold. Also, there's a limit to how low you can go with any given size tank. At very low pressures, the gas becomes less dense and will not flow into the tank as easily. This makes a smaller tank capable of holding more pressure than a larger one.
Compressors are rated by their storage capacity. The rating may be indicated in either CFM or SCFM. For example, a compressor that delivers 15 CFM at 150 PSI has 30 cubic feet of storage space compared to 10 cubic feet per second of delivery rate.
The PSI level at which a compressor operates is called its "compression ratio". For example, if a compressor pumps out 1000 CFM at 20 PSI, then its compression ratio is 50%.
Higher compression ratios mean fewer moving parts and therefore less chance of failure. This is why high-capacity compressors usually run at high pressures.
CFM and PSI have a simple linear connection. At 60 PSI, you will receive 4 CFM if you get 8 CFM at 120 PSI. The pressure simply "pushes" the air out, and half the "push" results in half the air flow.
You can also convert CFM to KGM by multiplying by 1.751. You can also convert KGM to PSI by dividing by 1.755.
So at 60 PSI, you would be getting 37.1 CFM. At this rate, it would take almost 9 minutes to fill a 10-foot cube with smoke.
At 100 PSI, the smoke fills up the room in just over 3 minutes! That's more than enough time to set some fireworks or do another activity with the kids.
As you increase the pressure even more, so does the flow of air. At 120 PSI, you are getting 83.3 CFM -- which is enough to fill a large room in under a minute.
And at 180 PSI, the flow of air is still strong but now it's moving at a steady stream rather than bursts of speed. This is perfect for blowing dust off a table or floor or anything else that needs to be cleaned slowly but thoroughly.
Converting between CFM and other units may come in handy at some point.