SCFM to CFM conversion

[Munch]

I have a compressor rated at

SCFM @ 40 PSIG = 3.7
SCFM @ 90 PSIG = 2.6

Will it handle something requiring 13 CFM @23 PSI?

For the life of me I can't find consistent conversion numbers...

[ducpainter]

I have a compressor rated at

SCFM @ 40 PSIG = 3.7
SCFM @ 90 PSIG = 2.6

Will it handle something requiring 13 CFM @23 PSI?

For the life of me I can't find consistent conversion numbers...

I have no proof...

experience tells me no way.

[red baron]

Oooo, a thread that's my speciality.


13 cfm at 23 psi is gonna require a large hose to flow that much volume at the low a pressure.


Figure on about 4 cfm per compressor horsepower.

[Speeddog]

Well, if Munch's 'something' can have the regulator attached to it, then you could use a small hose.

That 4 cfm per HP, what duty cycle are we talking about?
Is that wide-open 24/7 or something else?

[Capo]

That compressor will not provide 13 cfm.

[Langanobob]

Can't help but  be curious what are you doing with it? 

I agree with the above comments that it just won't work but sometimes air-powered stuff will sort of work without rated flow so depending on what it is and how much you need to use it, it may be worth a try if you already have this compressor.  If you're thinking of buying this compressor I think I would pass on it and get a bigger/better one. 

I *think* the relationship between compressor  CFM  and pressure is relatively linear, so if your compressor CFM only increases by 1.1 in dropping  50 psi from 90 to 40 psi, I don't think it's reasonable to expect it to increase by 10 psi or so in dropping only another 17 psi to 23 psi.  I think 4 or 5 CFM at 23 psi is more realistic.

You probably know this already but SCFM is Standard CFM which means the CFM at about 70F or so and atmospheric pressure.  ACFM is Actual CFM and is the CFM at whatever pressure you are working with.  Because it's compressed, ACFM is lower than SCFM so you have to make sure which CFM your device is rated at. 

[ducatiz]

My understanding is that when a device says xCFM@ypsi it is referring to SCFM (at least that's what my painter friend says).

You won't find ACFM on most commonly available air powered equipment, certainly not retail/consumer stuff.

but that's a lot of volume.  most good consumer compressors are going to make around 3-5 CFM at 90 psi nad have 2-4 hp gas motors (or equivalent electric motors).  Figure 5-6 hp minimum and a good sized tank probably at least 40-60 gallons.

Probably not going to use 3/8" hose either!

[ducpainter]

3/8" hose is fine...

the connector/qd is important.

[Langanobob]

ducatizz brought up a good point about storage tank size.  If you only need this 13 CFM at 23 psi for relatively short bursts you *could* use a small compressor with a larger tank to store enough air in to supply the 13 CFM.  For a short time, then you'd have a long wait 'til it charged up again.

But your best bet by far is a correctly sized compressor.

[mitt]

That compressor will not provide 13 cfm.

* continuously

Like said above, if it is for a quick burst, and you have a holding tank, it could supply 13cfm for a few seconds.

mitt

[NAKID]

OK, I agree with everyone so far. But what are you using that requires that much air?

[ducpainter]

OK, I agree with everyone so far. But what are you using that requires that much air?

Most hvlp spray guns need that kind of volume.

But I'm guessing.

[NAKID]

What size compressor do you have Nate?

[ducpainter]

What size compressor do you have Nate?

It's a 5 hp Quincy two stage...old model...

80 gallon tank...17cfm at more pressure than any spraygun ever used.

[Speedbag]

One could connect another relatively large tank in series. Used to do this years ago back when I actually sprayed paint a bit (in ancient times, before HVLP guns) and didn't have the real equipment but got by.