SCFM Vs. CFM Air Compressor: What Are The Differences?

SCFM vs CFM air compressors appear similarly, and thus, many people feel lost when it comes to differentiating these terms. Indeed, telling these 2 terms apart isn’t common knowledge, and the fact that there is no clear explanation regarding SCFM and CFM makes it even trickier to understand. 

But don’t worry – we’re here to help. Today’s article will clear the path for you. Stay tuned!

What Does SCFM Stand For?

SCFM is an abbreviation of Standard Cubic Feet per Minute. It represents the cubic flow speed of air under standardized circumstances of constant pressure and heat. 

SCFM has a tight bond with the mass flow rate of the gas (mass of a gas delivered through a specific area in a specific time) via a multiplicative constant that relies solely on the molecular gas volume.

There are various standardized settings for pressure, heat, and even standard humidity levels. Therefore, you need to pay extra attention while selecting a standard environment. People would usually calculate the SCFM readings following the air expansion to a standard pressure of about 14.7 PSIA.

Nevertheless, it’s important to note that standards might differ from one to another. Until now, there hasn’t been any global consensus on what the ‘universal standard’ actually is in this regard.

Temperatures can range from 68°F to 0°C to 15°C to 20°C, for example. As a result, many adopt 14.73 PSIA as the pressure standard, while others prefer 14.696 PSIA. These differences will even be more apparent when you come to other regions. 

For instance, as an American coming to Europe, you will notice that the typical American temperature standard ranges from 60 to 70 ℉, whereas the standard European temperature ranges from 0°C.

Be aware, however, that this is not always the situation. Those are only a few examples of commonly used settings. Thus, the outcome is a wide range of volumetric flow speeds. For example, if one calculates the SCMF at 0°C while the other does so at 60°F, the results will drastically vary.

What Does CFM Stand For? 

CFM is an abbreviation representing Cubic Feet per Minute. The concept is difficult to understand since there isn’t a precise meaning applicable in all circumstances. In addition, there is no method of comparing the weight of a gas using a number since gases are compressible.

Yet, CFM is a measurement of air volume under real-time pressure or temperature in the simplest meaning. Also, if you want to identify the CFM measurement in an air compressor, it’s a must to lower the pressure to under 90 PSI.

However, this calculation is pretty similar to the old-fashioned horsepower rates of the 1960s, which did not consider various real-world conditions, which is ineffective. 

In reality, the compressor ends up losing airflow owing to temperature and resistance factors. Additionally, obstacles in the coupling between the piston and the container (including your air device) also affect the CFM value. 

Thus, many manufacturers are now utilizing DCFM, also known as displaced CFM, which applies arithmetic to determine how much gas the machine’s tank will flow out at a particular RPM. 

We also have another measurement called ACFM, or actual CFM, which people measure by operating the compressor and counting its actual released air volume.

The Differences Between SCFM Vs CFM Air Compressor

Here’s an easy way to visualize the distinction between SCFM vs CFM indexes:

For example, in a steamy, high-pressure environment containing an air balloon volume of 1ft3, the flow pace would be around one cubic foot per minute (CFM). Therefore, its mass flow rate is 3 – 4 SCFM in this scenario.

But that’s not true. What truly happens, though, is that the balloon tends to inflate as it adjusts to the external setting, which is more or less the usual rate. 

Although these 2 terms are interchangeable, for most applications, SCFM is preferable since it can also inform you of the heat and pressure index. 

A few more differences between CFM and SCFM are: 

  • CFM is usually a lower figure than SCFM since it gets measured at a higher pressure than SCFM, leading to a lower gas volume.
  • There are no specified metrics for calculating CFM figures, but SCFM calculations utilize a system of standardized factors such as pressure, heat, and volume.
  • People carry CFM measurements at a pressure of 90 PSI, whereas they calculate SCFM after the air expands to an average level of about 14.7 PSIA.

Does PSI Affect CFM?

Not really! A compressor’s CFM rating at 100 PSI does not guarantee that it will generate a considerably higher CFM at 90 PSI. 

There is no variation in the piston displacement or the compressor drive RPM because they are all constant. The temperature loss and parasitic variables, including resistance, get reduced when the PSI drops, but the amount of air pumped remains the same.

When purchasing a compressor, a principle is to seek something designated at 1.5 times the CFM requirement of the devices you usually utilize. After all, there’s room for fluctuations due to the air compressor’s sensitivity to things like heat and dampness.

How Can I Calculate The CFM? 

It’s easy to determine the CFM of an air compressor by performing the below steps:

  • Firstly, spot the tank capacity in gallons. It’s relatively evident as the suppliers usually state this specification on the device.
  • Afterward, calculate your tank volume by dividing the capacity value by 7.48.
  • Release air, then refill the compressor. Make sure to note the time it costs to fill the tank while observing the tank gauge. 
  • Now, keep track of the PSI (pounds per square inch) when the machine starts and stops for PSI 1 and PSI 2 (these 2 numbers are 2 different PSI measurements).
  • After that, take PSI 1 minus PSI 2 and divide the result by 14.7. This number represents the tank pressure while refueling.
  • Next, divide the tank capacity you calculated previously by the newly computed pressure.
  • Translate this index to minutes by dividing it by the amount of time (in seconds) it costs the machine to pump that air amount.
  • Multiply the newly calculated number by 60, and you’re done.

Conclusion

That’s everything we have for you today regarding the topic of SCFM vs CFM air compressors. Hopefully, we have cleared the way for you and made it a bit easier for you to distinguish these two complicated terms.