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# SCFM vs ACFM

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## SCFM vs ACFM

(OP)
Can someone please give me some information on how to calculate the SCFM for a compressor?

Flow - 1100 acfm
Pressure - 100 psig
Air Temp - 110 F
Altitude - 1600 ft

A formula and sample calculation would be great.

### RE: SCFM vs ACFM

scfm=acfm*(p+14.7)/14.7*530/(t+460)
t temp fahrenheit
p psig

### RE: SCFM vs ACFM

(OP)
Thanks for the formula Zekman.

Would you substitute the atmospheric pressure associated with 1600 ft elevation instead of 14.7?

### RE: SCFM vs ACFM

Visiting the above given threads would have cleared your confusion.

Actually, the equation for conversion of ACFM to SCFM is

ACFM = (SCFM x Pstd x T)/[(P-Psat*RH)x Tstd]

Where, P and T are actual pressure and temperature in psia and Rankine respectively, Psat is the saturation pressure of water vapor at the actual temperature and pressure conditions. Pstd is standard pressure, 14.696psia and Tstd is (460+60)R.

A general standard condition is at 60F temperature, 14.696psia pressure and 0%RH but there are some different values across globe.

When you calculate SCFM these are the things you should consider. However, if you are trying to calculate FAD(free air delivery) then atmospheric pressure comes into picture.

Regards,

### RE: SCFM vs ACFM

(OP)
I did read the threads and called the compressor supplier yesterday. The compressors in question were purchased from Sullair and what they call standard conditions are 14.5 psia, 68 F, and dry conditions which i assume to be 0 % RH. There is no mention of the altitude being at sea level.

It seems to me they are mixing numbers, They use atmospheric pressure but dry to me signifys a condition after the air dryer.

The actual line conditions after the air dryer are known. I'm trying to determine the difference between the nameplate capacity and the actual. Once I determine the reserve capacity, then I have to size a larger receiver to keep the second compressor from loading and unloading continiously.

### RE: SCFM vs ACFM

Compressor manufacturers are very prone to "fudge" thier numbers. Make sure you take thier numbers with a very large block of salt.

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