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A Closer Look
SCFM, ACFM, ICFM...What Does it Mean?
One of the terms that is often confused in compressed air and gas systems is the term CFM or Cubic Feet Per Minute. This term is also expressed as SCFM, ACFM, and
ICFM. So what are the differences SCFM vs ACFM?
Definition SCFM -- The term SCFM stands for Standard Cubic Feet Per Minute, referenced to a pre-specified pressure, temperature, and relative humidity. In most cases,
SCFM is referenced to 14.7 PSIA, 68°F, and 0% relative humidity. By specifying these parameters, the mass flow of compressed air and gas systems is clearly defined.
ACFM Definition -- The term ACFM stands for Actual Cubic Feet Per Minute and is often improperly used by some air compressor vendors. For example, an air compressor
vendor may state that a 200 HP air compressor is rated for 1000 ACFM at 100 PSIG. Taking this phrase literally, the natural assumption is that 1000 Actual Cubic Feet
Per Minute of compressed air is leaving the discharge of the compressor at 100 PSIG. This is incorrect. The compressor vendor should have stated that this 200 HP air
compressor is rated for 1000 Inlet Cubic Feet Per Minute (through the inlet air filter) when operating at a discharge pressure of 100 PSIG. The actual volume flow of
compressed air leaving this air compressor is about 125 ACFM, depending on ambient conditions.
If in the above example, the atmospheric air pressure was 14.7 PSIA, the ambient air temperature was 68°F, and there was no water vapor in the ambient air (0%
relative humidity), then this air compressor would produce 1000 SCFM when operating at 100 PSIG discharge pressure.
This entire subject can be very confusing and, if you are like most people, this paper will require more than one reading. In fact, we have spent many hours explaining
this subject to consulting engineering companies.
At Fluid Energy, we believe that understanding basic fundamentals is important when analyzing and troubleshooting compressed air and gas systems. Please contact your
Fluid Energy representative if you would like further definition on this subject.
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