Sutherland Shire Air Compressors Community Guide and Business Directory - Cronulla, Caringbah, Miranda, Gymea, Sutherland, Kirrawee, Woronora, Jannali, Kareela, Como, Bonnet Bay, Engadine, Sylvania.

Air Compressors

When manufacturers list performance for blowers and compressors it is stated as "Capacity" in CFM (Cubic Feet per Minute). This refers to the volume of air at the inlet to the unit, therefore this is often referred to as Inlet CFM (ICFM) or Actual CFM (ACFM). These terms are used interchangeably and mean basically the same thing (CFM, ICFM, ACFM).

SCFM

Standard Cubic Feet per Minute (SCFM) is a volumetric flow-rate corrected to standard-density conditions. SCFM is volumetric flow-rate at a “standardized” pressure, temperature, and relative humidity. The “standard” ambient conditions are defined by 14.7 psi a atmospheric pressure, some temperature (e.g., 68°F) depending on the "standard" used, and some relative humidity (e.g., 36%, 0%) depending on the "standard" used.

ACFM

Actual Cubic Feet per Minute (ACFM) is the volume of gas flowing anywhere in a system independent of its density. If the system were moving air at exactly the "standard" condition, then ACFM would equal SCFM. Unfortunately, this usually is not the case as the most important change between these two definitions is the pressure. To move air a positive pressure or a vacuum must be created. When positive pressure is applied to a standard cubic foot of air, it gets smaller. When a vacuum is applied to a standard cubic foot of air, it expands. The volume of air after it is pressurized or rarefied is referred to as its “actual” volume.

CFM is often a confusing term because it has no single definition that applies to all instances. In the most basic sense, CFM means cubic feet per minute. Sounds simple enough right? Unfortunately, air is a compressible gas. To further confuse the issue, a centrifugal fan is a constant CFM device or a constant volume device. This means that, provided the fan speed remains constant, a centrifugal fan will pump a constant volume of air. This is not the same as pumping a constant mass of air. Again, the fan will pump the same volume, though not mass, at any other air density. This means that the air velocity in a system is the same even though mass flow rate through the fan is not.