Is there any way.... (hey roger)

Thanks Chris

Here's another way to estimate capacity that's pretty easy. Just rearrange the equation to solve for cfm instead of time. Make sure you use absolute values for pressures (psig+14.7). Also from Ingersoll-Rand.

Rod

20psi = 1.96 CFM, 25 psi = 2.25 CFM, 30 PSI = 2.53 cfm, 35 psi = 2.81 cfm, 40 psi = 3.10 cfm, 45 psi = 3.38 cfm, 50 psi = 3.66 cfm, 60 psi = 4.23 cfm, 70 psi = 4.79 cfm, 80 psi = 5.36 cfm.

For a 1/8" orifice:

20 psi = 7.86 cfm, 25 psi = 8.98 cfm, 30 psi = 10.1 cfm, 35 psi = 11.3 cfm, 40 psi = 12.4 cfm

A real 5hp compressor should be able to hold between 60 - 80 psi with a 1/8" orifice.

A good 10 hp compressor should be able to hold between 25 - 35 psi with a 1/4" orifice.

A good 20 hp compressor should be able to hold between 65 - 90 psi with a 1/4" orifice.

Pressure maintained with a 1/8" Orifice: 20 psi = 7.86 cfm, 25 psi = 8.98 cfm, 30 psi = 10.1 cfm, 35 psi = 11.3 cfm, 40 psi = 12.4 cfm.

Remember, these values are calculated at "standard" conditions, 70 F @ sea level. The shape of the orifice can also slightly affect the values. You should use a glycerine filled pressure gauge as well, to help dampen vibrations. Don't be too disappointed if your machine puts out somewhat less than it's specifications, especially if you live at a bit of an elevation. In Edmonton, at around 2200ft, compressors were only able to deliver 97% of their claimed output.