# Recommended CFM @ 90 PSI?

1. Sep 5, 2006

### mapair

Hello folks, I am trying to find some general numbers on what the recommended max. CFM for compressed air @ 90 PSI is through the following pipe sizes: 1/2", 1", 1.25", 1.5" & 3". I'm not looking for anything specific, just some general numbers. I'd greatly appreciate any input on this! Thanks!

2. Sep 5, 2006

### Q_Goest

Hi mapair,
I wouldn't recommend a maximum flow through a pipe because it varies so much depending on the actual system and what the system is needed for. The longer the pipe, and the more elbows, valves and other restrictions it has, the more pressure drop you will get. What might be an acceptable flow rate for one system may produce way too much pressure drop for another system.

Just to give you a few numbers for flow (note: all flow is in SCFM, assuming 70 F) I'll jot down some flows that give you a 2 psi drop per 10 feet of pipe. I'm also assuming clean, schedule 40, steel pipe for each of these:
1/2" - 74 SCFM
1" - 295 SCFM
1.25" - 608 SCFM
1.5" - 912 SCFM
3" - 4946 SCFM

If you want more specific calculations, you might try doing a search for free online calculators.