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Standard CFM
When talking about the airflow capacity of an air compressor, this amount is measured in terms of cubic feet per minute (CFM). CFM is the rate and volume of free airflow an air compressor unit can produce, with a higher CFM meaning an air compressor system can power more pneumatic tools and machinery at once.
But what is standard CFM airflow?
Standard CFM (SCFM) is the amount of air a compressor can deliver under a standard set of reference pressure and temperature conditions. These accepted standard values are:
- 14.5 psia (pounds per square inch absolute)
- 68 degrees Fahrenheit with no humidity
While CFM reflects the size and speed of the air compressor’s internal capacities, SCFM is a better indicator of whether the compressor can effectively power your tools or processes.
FAQs
The critical difference between standard CFM and actual CFM (ACFM) is that SCFM is a theoretical, standardized value, while ACFM is a real-world measurement.
A compressor’s SCFM rating standardizes the factors of heat, humidity and pressurization. ACFM measures the volume of air flowing through a system in its given working environment. This metric accounts for the real-world temperature, pressure and humidity of where the compressor is being used. It can only be determined once the machine is operational within a facility.
SCFM is essential for standardized comparisons. In situations when air compressors may be used in varying environmental conditions, a normalized metric allows you to evaluate equipment performance and make accurate comparisons. This ensures that measured performance is comparable across different settings regardless of external factors.
Understanding the conditions where an air compressor operates allows you to convert SCFM to CFM and vice versa.
Here is the formula to calculate CFM, which provides a metric of the compressor’s output in its current environment:
- CFM = Volume (in cubic feet) / Time (in minutes)
But what is the standard CFM formula? This requires converting CFM to SCFM, accounting for standard conditions to standardize the measurement.
Here is the CFM to SCFM conversion formula:
- SCFM = CFM × (Pactual/Pstd) × (Tstd/Tactual)
Here’s what each part means:
- Pstd: Standard pressure
- Pactual: Actual pressure
- Tactual: Actual temperature
- Tstd: Standard temperature
One of the most important variables to consider when choosing what size air compressor you need is the compressed air volume expressed as standard CFM. Your air compressor must be able to power multiple pneumatic tools simultaneously.
To ensure a compressor has the needed output, you must calculate your total SCFM requirements. Here’s how to do that:
- Make a list of all the tools you plan to use concurrently.
- Find the SCFM rating for each tool in its manual or on the manufacturer’s website.
- Convert the tool’s rating from CFM to SCFM if needed.
- Add up the total SCFM requirements of the tools you’ll use simultaneously.
- Add 25% to the sum to account for potential fluctuations and future growth.
This number allows you to select a compressor with an SCFM output that meets or exceeds the calculated total. For example, if the sum equals a combined SCFM of 500, you would need an air compressor with a total capacity of 625 CFM.
If you need help determining the best air compressor size and type for your industry or application, contact Quincy Compressor.