CFMs relation to PSI help

[unspankable]

Hello all,

I have a 240v single stage compressor rated 11cfm@125psi.
How do I determine how many cfm it'll flow at a lower pressure?

For instance I have a Sata NR2000 HVLP spray gun rated 15cfm@29psi and since cfm's available increase as pressure drops, I'm wondering if my compressor will be ok.

Any input would be much appreciated.
Thanks!

 

[dsmnickk90]

Hello all,

I have a 240v single stage compressor rated 11cfm@125psi.
How do I determine how many cfm it'll flow at a lower pressure?

For instance I have a Sata NR2000 HVLP spray gun rated 15cfm@29psi and since cfm's available increase as pressure drops, I'm wondering if my compressor will be ok.

Any input would be much appreciated.
Thanks!

Yes it will be okay. At 30psi it probably has close to 25 - 30cfm. How big is the tank?

 

[MattT]

I don't think there is a fixed formula for how much extra cfm you'll get with reduced pressure. Not that it'd help you any if there was. Your compressors output rating is continuous and the guns consumption rating will be average. So it'll use 15cfm over time but way more than that while you're actually painting.

All you can really do is try it. If it doesn't keep up you'll either have to take breaks to let the pressure build back up or get a bigger compressor and/or add on tank capacity.

 

[Bob C]

All you can really do is try it. If it doesn't keep up you'll either have to take breaks to let the pressure build back up or get a bigger compressor and/or add on tank capacity.

^Simplest way.

 

[KinzeMech]

I have a 240v single stage compressor rated 11cfm@125psi.
How do I determine how many cfm it'll flow at a lower pressure?

If you post a make and model of the compressor, someone might know. It is odd to find a single stage compressor with an output rating at 125psi. Most of them are given two flow ratings, one at 90psi and one at 40 psi. Typically, a pump rated 11scfm at 90 psi would normally also be rated around 12.5-13 scfm @ 40 psi.

 

[bsaint]

the "graph" would be semi linear because thermal dynamics would tell you heat is involved and fluid mechanics would tell you the efficiency is reduced when you add heat. Ill dig out some books and tell you.

 

[pipsters]

Post how long it takes to go from 25 to 35 PSI in seconds, and how big your tank is (gals). I can give you an estimate.

 

[KinzeMech]

thermal dynamics

Is this a real thing? Or a misspelling of thermodynamics?

 

[DekeT]

My rule of thumb is an increase of about 1.5-2 cfm for every halving of the pressure. So at 30psi I would estimate 14-15 cfm for your setup. Pipsters suggestion is the measurable way to do this with good results.

 

[unspankable]

If you post a make and model of the compressor, someone might know. It is odd to find a single stage compressor with an output rating at 125psi. Most of them are given two flow ratings, one at 90psi and one at 40 psi. Typically, a pump rated 11scfm at 90 psi would normally also be rated around 12.5-13 scfm @ 40 psi.

Compressed air systems 3hp contractor series 20gal
It says 12cfm@40 psi and free air is 14 so looks like I'm screwed.
http://www.compressed-air-systems.com/images/downloads/product_sheets/port_3hp_elec.pdf

Is there any decent paint gun that i can get by with or should i get a real compressor?

Thanks for the help.

 

[KinzeMech]

That's a pretty decent single stage compressor. You could probably use a little more storage space. If you can scavenge a junk compressor from somewhere, that's a tank you can tee in. Another option is harbor freight has an 11 gallon portable tank for $40. That's another 50% tank capacity right there, and when you're done, who doesn't have use for an air bubble?

If the specs on the gun are correct, and the specs on the compressor are correct, they should work together just fine. Your pump puts out 80% of your gun's capacity. If you get enough tank space to give the compressor a head start, it should work fine.

 

[unspankable]

That's a pretty decent single stage compressor. You could probably use a little more storage space. If you can scavenge a junk compressor from somewhere, that's a tank you can tee in. Another option is harbor freight has an 11 gallon portable tank for $40. That's another 50% tank capacity right there, and when you're done, who doesn't have use for an air bubble?

If the specs on the gun are correct, and the specs on the compressor are correct, they should work together just fine. Your pump puts out 80% of your gun's capacity. If you get enough tank space to give the compressor a head start, it should work fine.

Is there anything special to this or do i just run air line to the spare tank then on to the rest of my equipment and gun?

 

[Outlawmws]

Is there anything special to this or do i just run air line to the spare tank then on to the rest of my equipment and gun?

That will do it.