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Compressors, CFM VS SCFM

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Forum topic by Raymond posted 09-15-2010 08:27 PM 5220 views 0 times favorited 5 replies Add to Favorites Watch
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Raymond

676 posts in 2413 days


09-15-2010 08:27 PM

Some new terms are appearing on compressors. I have narrowed my search for a new compressor to the 30 gallon Sanborn at Menards. 6.1 CFM at 40 and 5.3 CFM at 90. And now along comes Craftsman with a 33 gallon 6.1 SCFM at 40 and 5.3 SCFM at 90. I did some googling and that did not help in finding a converter from CFM to SCFM. Anyone have any thoughts on that is better to look for in compressors. High CFM or SCFM numbers. Is there any real difference when talking CFM verses SCFM?

-- Ray


5 replies so far

View syenefarmer's profile

syenefarmer

390 posts in 1767 days


#1 posted 09-15-2010 08:32 PM

This may help to clarify the difference for you, SCFM vs CFM. I recently purchased a new compressor and the rating I looked for while researching was SCFM and not CFM. I eliminated any compressor from consideration if the SCFM rating wasn’t easily available from the Owners Manual or the store selling it.

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Raymond

676 posts in 2413 days


#2 posted 09-15-2010 10:24 PM

Who would have thought that purchasing a compressor would be so much work. Now I find out that. Sanborn, which was part of Coleman Powermate. Come to find out that Coleman Powermate is now out of business http://www.mastertoolrepair.com/-c-6_35.html and has been taken over by http://www.midwest-air.com/products/power%20equipment/airstream.html. I might do better with the Craftsman. Ugg the search continues.

-- Ray

View lew's profile

lew

10088 posts in 2441 days


#3 posted 09-15-2010 11:24 PM

Just a thought here. If you follow the links posted by syenefarmer there is a formula to calculate Actual CFM (ACFM) from Standard CFM (SCFM) [ http://www.sponsler.com/whatacfm.htm ]. In the example given, a compressor with a SCFM rating of 1000 has a ACFM rating of 128.

This seems to me to be sort of like the way speakers and amplifier manufactures “misrepresent” their power ratings- to Average Joe Public. Electrical energy can be measured 3 ways- RMS, Peak and Peak to Peak. An amplifier may have a power rating of about 35 watts (RMS). It could also be rated at 50 watts (peak) or even 100 watts (Peak to Peak). 35 watts RMS is most closely related to the “actual” or “real” rating. However, 50watts or 100 watts looks more impressive and appears to be more powerful.

Could SCFM simply be a way of “overstating” the compressors specifications? I wonder.

Lew

-- Lew- Time traveler. Purveyor of the Universe's finest custom rolling pins.

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Radu

299 posts in 1729 days


#4 posted 09-15-2010 11:26 PM

Ray,
The flow rate for compressible fluids (air in this case) should always be referred as StandardCFM (Standard conditions 15 °C and 100.325 kPa / 60 °F and 14.696 psi). The humidity has some effect too, but let’s not complicate things.

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Raymond

676 posts in 2413 days


#5 posted 09-16-2010 03:12 PM

Thanks for all the suggestion. The search continues.

-- Ray

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