Why The Difference In Cfm
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Post Fiend
Joined: Mar 2004
Posts: 24,418
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From: San Francisco, Ca.
Why The Difference In Cfm
Hi! Can someone explain to me why a puematic tool is rated, for an example, 4 CFM no load speed and then 16 CFM at load? I'm thinking of getting an Ingersoll Rand 8" geared orbital sander # IR328B. Why the big difference in CFM from the non-load and load specs? Does putting the pad on a surface really use that much more CFM? If I do get it, it's going to be used for paint removal and body prep work. They do work great.
Tuned
Joined: Sep 2003
Posts: 483
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It isnt no load, its a number for industrial averaging not an actual which would vary some with pressure. If we had a hundred workers only a third of them would be using air at any given time so thats how you would need to size the compressor, I agree its kind of,, well,, misleading for lack of better words. If you had a hundred workers with air tools you would need to size a comp for 35 of them.
Thread Starter
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Post Fiend
Joined: Mar 2004
Posts: 24,418
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From: San Francisco, Ca.
Thanks Sberry27. Now I'm just a little confused. Below are the specs. What size compressor do you think I need. I appreciate the input.
Free Speed (rpm) 825
Pad Diameter (in./mm) 8/200
Net Wt (lbs./kg) 4.7/2.13
Overall Length (in./mm) 11.8/300
Av. Air Consump. (cfm/l/min.) 4/113
@ Load (cfm/l/min.) 16/453
Sound dB(A) (pressure/power) 90.45/93.7
Air Inlet (in.) 1/4
Min. Hose Size (in./mm) 3/8"/10
Free Speed (rpm) 825
Pad Diameter (in./mm) 8/200
Net Wt (lbs./kg) 4.7/2.13
Overall Length (in./mm) 11.8/300
Av. Air Consump. (cfm/l/min.) 4/113
@ Load (cfm/l/min.) 16/453
Sound dB(A) (pressure/power) 90.45/93.7
Air Inlet (in.) 1/4
Min. Hose Size (in./mm) 3/8"/10
Tuned
Joined: Sep 2003
Posts: 483
Likes: 1
According to that it needs 16 to run continious. I ran the same sander from a comp making 12 and it wasnt a real problem but its been a while and do not recall how long it ran before we needed to wait on air. Normally the figure is 3 times the avg but see they rated that one at 4. For body work a comp making the full 16 wouldnt be any too much, the 12 was a little on the small side. Sanding really eats the air, even a 6 inch DA would outrun the 12 cfm unit. I would be looking for something in the 17+ cfm rating. I am making 28 now and it allows 2 men to work with air hungry tools, and really 3 because they are not all sanding full time at once. I didnt quote any horsepower ratings as they are so misleading its irrelevent, go by cfm.
