Industrial Components and Equipment Division - Hitachi America, Ltd.
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Air Flow Definition - Air Technology Group Technical Support Library - ICED : Hitachi America, Ltd.

Hitachi America, Ltd., Industrial Components and Equipment Division
Oil Free Compressed Air and Vacuum

Air Flow Definition - Hitachi Air Technology Group

Hitachi Air Technology Group provides air flow definition related to the flow of air in various Hitachi Air Technology Group products. The air flow definition helps end users to accurately configure Hitachi Air Technology Group products for optimum performance.

Go through the following sections for Hitachi Air Technology Group air flow definition:

SCFM - Standard Cubic Feet per Minute*

Compressed air consumption is commonly rated in Standard Cubic Feet per Minute - SCFM. SCFM determines the weight of air to fixed or "Standard" conditions. There are several definitions of SCFM. However, in the United States, the most common air flow definition is used with "sea-level" properties:

  • 14.696 Pounds per Square Inch (psia)
  • 60 Degrees Fahrenheit ( oF ) ( 520oR )
  • 0% Relative Humidity (RH).

Europeans normally use one ATA and 0oC as SCFM.

ACFM - Actual Cubic Feet per Minute*

Real life "actual conditions" are seldom "standard conditions". Actual air volume flow is often termed as
ACFM - Actual Cubic Feet per Minute.

Actual Cubic Feet per Minute - ACFM, depends on the

  • Pressure,
  • Temperature, and
  • Humidity of the actual air.

The conversion from SCFM to ACFM can be expressed as:

ACFM = SCFM [Pstd / (Pact - Psat Φ)](Tact / Tstd) (1)

where

  • ACFM = Actual Cubic Feet per Minute
  • SCFM = Standard Cubic Feet per Minute
  • Pstd = Standard absolute air pressure (psia)
  • Pact = Actual absolute barometric pressure (psia)
  • Psat = Saturation pressure (psi)
  • Φ = Actual relative humidity
  • Tact = Actual ambient air temperature ( oR )
  • Tstd = Standard temperature ( oR )

ICFM - Inlet Cubic Feet per Minute*

Inlet Cubic Feet per Minute - ICFM, is used by compressor vendors to establish conditions in front of additional equipment like inlet filter, blower or booster.

When air passes through the filter, there will be a pressure drop. The conversion from ICFM to
ACFM can be expressed as:

ACFM = ICFM (Pact / Pf) (Tf / Tact) (1)

where

  • ICFM = Inlet Cubic Feet per Minute
  • Pf = Pressure after filter or inlet equipment (psia)
  • Tf = Temperature after filter or inlet equipment ( oR )

* - Information supplied by The Engineering Tool Box