PSI Versus CFM
What is PSI?
PSI (Pounds per Square Inch) is a unit of pressure. It measures how much force is exerted on a square inch of surface area. In a compressed air system, PSI tells you how strongly the air is being compressed inside the tank. For example, if a tank is pressurized to 150 PSI, it means that each square inch inside the tank is experiencing a force of 150 pounds.
Why PSI Matters:
Pressure Strength
Higher PSI means more compressed air force. This is crucial for tools and equipment that require high pressure to operate efficiently.
System Performance
The PSI rating helps determine the capacity and efficiency of the air compressor in delivering the needed pressure for various applications.
What is CFM?
CFM (Cubic Feet per Minute) is a unit of airflow. It measures the volume of air that the compressor can deliver in one minute. In simpler terms, CFM tells you how much air is being moved by the compressor. For example, a compressor with a rating of 60 CFM can supply 60 cubic feet of air every minute.
Why CFM Matters:
Airflow Volume
The higher the CFM, the more air the compressor can deliver, which is essential for tools and machines that require a constant and high volume of air.
Efficiency and Capability
Knowing the CFM rating helps you choose the right compressor for your needs, ensuring it can handle the demand of your air-powered tools and equipment.
How PSI and CFM Work Together
Imagine you have a balloon filled with air. The more you squeeze it, the higher the pressure inside the balloon gets. Now, if you let the air out through a small hole, the air will flow out at a certain rate. This rate of airflow is like CFM.
How it Works:
Filling the Tank:
Think of your air compressor tank like a balloon that’s pumped up to a high pressure, say 150 PSI.
Using the Air:
When you start using the air (like letting air out of the balloon), you use it at a certain rate. This rate is measured in cubic feet per minute (CFM).
Maintaining Pressure:
The compressor keeps pumping to try and maintain that high pressure (150 PSI). But if you start using air faster than the compressor can pump it in, the pressure will drop.
Finding Maximum Capacity:
If you use air faster and faster, you’ll reach a point where the pressure starts to drop. The rate at which this happens tells you your compressor’s maximum capacity at that pressure. For example, if it drops when you use 60 CFM, your compressor can handle 60 CFM at 150 PSI.
Different Pressures, Different Rates:
If you do the same test at a lower pressure, like 75 PSI, you’ll find a different maximum CFM because the compressor works differently at different pressures.
How Much Air Do I Need For My Tools?
To give you an idea of how much air you might require, below is a chart of commonly used pneumatic equipment, along with an approximation of the air required to power them.
Equipment | PSI | CFM |
|---|---|---|
Impact Wrench 3/8th-1/2" | 70-90 | 5 |
Impact Wrench 1/2-3/4" | 70-60 | 10 |
Impact Wrench 3/4-1 3/4" | 70-90 | 20 |
Air Ratchet | 70-90 | 3-5 |
Orbital Body Sander | 70-90 | 12 |
Tire Changer | 125-150 | 2 |
Bead Breaker | 125-150 | 12 |
Blow Gun | 70-90 | 3 |
Die Grinder | 70-90 | 7 |
Screwdriver #2-6 Screw | 70-90 | 5 |
Screwdriver #6-5/16 Screw | 70-90 | 10 |
Paint Spray Gun (HVLP) | 40-60 | 15 |
Note: Be sure to check with you tool and equipment's' documentation before purchasing an air compressor. This list is only intended to help you approximate your air consumption.
Are You Looking for an Air Compressor?
For almost two decades, we have been manufacturing our industry-leading line of air compressors: the Twister series. We offer models ranging from 60 to 250 CFM at up to 225PSI, and can be powered by everything from diesel, to propane, to electricity.