Re: Air Compressor Redux

[Don Malling <dmallin@attglobal.net>]

It would seem that CFM is a meaningless term out of context of a 
specified or assumed PSI. Certainly a tool's CFM requirements would be 
different at 15 PSI vs 90 PSI.

According to this site 
http://www.cleandryair.com/scfm_vs__icfm_vs__acfm.htm

SCFM (Standard CFM) is CFM at standard conditions: 14.7 (15) PSI (sea 
level) 60 degrees and 0% humidity.

It would seem that the big variable in CFM is CFM at what PSI. The air 
compressor is rated to deliver 18 CFM at 175 PSI.
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=5730

Some air tools specify a CFM rating at a specified PSI

5 CFM @ 90 PSI
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=53176

8-10 CFM @ 90 PSI
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=46874

Some don't mention a PSI
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=113

15 CFM @ 90 PSI
http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=46015

It appears that 90 PSI is a standard when specifying a tool's CFM 
requirements.

I'm not sure how to translate CFM at one PSI to CFM at another PSI 
(maybe it's exponential by PSI or something), but it would seem that if 
the tool's requirement is 5 CFM @ 90 PSI and my compressor is rated at 
an air delivery rate of 19.5 CFM at 100 PSI, I should have enough 
compressor capacity to run about 4 of those tools. The PSI is about the 
same, but the compressor delivers almost 4 times the tool's required CFM 
at the required PSI.

Yes/No?

Don Malling