Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

This is an AMP page - Open full page! for all features.

Air - SCFM versus ACFM and ICFM

Actual air compressor capacity (ACFM) vs. standard air capacity (SCFM) and inlet air capacity (ICFM).

Sponsored Links

SCFM - Standard Cubic Feet per Minute

It is common to rate compressed air consumption in Standard Cubic Feet per Minute - SCFM.

The SCFM - Standard Cubic Feet per Minute - determines the weight of air to fixed or "Standard" conditions. There are several definitions of SCFM. The most common used in the United States is with the "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 0 oC as SCFM.

Note that the The Compressed Air & Gas Institute and PNEUROP have adopted the definition used in ISO standards with dry (0% relative humidity) air at 14.5 psia (1 bar) and 68 oF (20 oC).

ACFM - Actual Cubic Feet per Minute

Real life "actual conditions" are seldom "standard conditions". When

  • pressure is applied a volume of air - it gets smaller
  • vacuum is applied to a volume of air - it expands

The actual air volume flow is often termed ACFM - Actual Cubic Feet per Minute.

The Actual Cubic Feet per Minute - ACFM - depends on the

  • pressure
  • temperature
  • humidity

of the actual air.

The conversion from SCFM to ACFM can be expressed

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 = absolute pressure at the actual level (psia)

Psat = saturation pressure at the actual temperature (psi)

Φ = Actual relative humidity

Tact = Actual ambient air temperature (oR)

Tstd = Standard temperature (oR)

Note!

Psat Φ < Pact

Related Mobile Apps from The Engineering ToolBox

- free apps for offline use on mobile devices.

Online SCFM - ACFM Calculator

The calculator below can used to calculate ACFM:

SCFM

Standard absolute air pressure - Pstd - (psia)

Actual absolute air pressure - Pact - (psia)

Saturation pressure at the actual temperature - Psat - (psia)

Actual relative humidity - Φ

Actual ambient air temperature - Tact - (oR)

Standard air temperature  - Tstd - (oR)


Load Calculator!

Example - SCFM to ACFM

The actual CFM of a compressor operating at "non-standard" conditions like

  • elevation 5000 feet (1500 m) - atmospheric pressure Pact = 12.23 psia
  • temperature 80oF - absolute temperature Tact = 540oR
  • saturation pressure Psat = 0.5069 psia
  • relative humidity Φ = 80%
  • demand: 100 SCFM

can be calculated as

ACFM = (100 SCFM) [(14.7 psia) / ((12.23 psia) - (0.5069 psia) (80 / 100))]((540 oR) / (520 oR))

    = 129.1  

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 ACFM to ICFM can be expressed as

ICFM = ACFM (Pact / Pf) (Tf / Tact)                                               (2)

where

ICFM = Inlet Cubic Feet per Minute

Pf = Pressure after filter or inlet equipment (psia)

Tf = Temperature after filter or inlet equipment (oR)

Note!

The Ideal Gas Law is accurate only at relatively low pressures and high temperatures. To account for the deviation from the ideal situation, another factor is included. It is called the Gas Compressibility Factor, or Z-factor. This correction factor depends on the pressure and temperature for each gas considered.

The True Gas Law, or the Non-Ideal Gas Law, becomes:

P V = Z n R T  (3)

where

Z = Gas Compressibility Factor

n = number of moles of gas present

Air Volume Conversion Factors

Air volume conversion factors related to air with temperature 70°F (21.1°C):

Air TemperatureFactor
°F°C
0 -17.2 1.152
10 -12.2 1.128
20 -6.7 1.104
30 -1.1 1.082
40 4.4 1.060
50 10.0 1.039
60 15.6 1.019
70 21.1 1.000
80 26.7 0.981
90 32.2 0.964
100 37.8 0.946
110 43.3 0.930
120 48.9 0.914
130 54.4 0.898
140 60.0 0.883
150 65.6 0.869
160 71.1 0.855
170 76.7 0.841
Sponsored Links

Related Topics

Related Documents

Sponsored Links

Share

Search Engineering ToolBox

  • the most efficient way to navigate the Engineering ToolBox!

SketchUp Extension - Online 3D modeling!

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your Sketchup model with the Engineering ToolBox - SketchUp Extension - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!

Privacy

We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.

Topics

Unit Converters

Temperature

oC
oF


Load Calculator!

Length

m
km
in
ft
yards
miles
naut miles


Load Calculator!

Area

m2
km2
in2
ft2
miles2
acres


Load Calculator!

Volume

m3
liters
in3
ft3
us gal


Load Calculator!

Weight

kgf
N
lbf


Load Calculator!

Velocity

m/s
km/h
ft/min
ft/s
mph
knots


Load Calculator!

Pressure

Pa (N/m2)
bar
mm H2O
kg/cm2
psi
inches H2O


Load Calculator!

Flow

m3/s
m3/h
US gpm
cfm


Load Calculator!

3 10

This website use cookies. By continuing to browse you are agreeing to our use of cookies! Learn more