Paint Gun CFM, how to check.

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PostPosted: Tue Jan 17, 2023 2:35 pm
Hello all. I just re-ran my air piping in my shop from the redneck way I had it to using 3/4 copper pipe. I was just using 3/8 hose to my regulator before and it worked good for years but I want to make sure I have enough cfm to my gun. My guns call for 10-12 cfm and around 28 psi at the gun. I can for sure get the psi at the gun but how do you know what cfm you are getting without using a gun/cap checker? Which I don't have. My question is : Is there a way to check for the correct cfm right at the gun? I don't use a small regulator or valve on the gun, I use a "checker" gauge on the gun and adjust on the wall then remove the checker gauge. I'm sure this will be fine but I would like to know what cfm I am getting at the gun. Any info appreciated, thanks.

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PostPosted: Tue Jan 17, 2023 3:31 pm
Your compressor should have a sticker on it or you can look it up online.

Compressor Specs.JPG


Notice that pump puts out 18.9 CFM however when under pressure the output drops down.
15.6 SCFM (Standard Cubic Feet per Minute) at 100 psi
15.2 SCFM at 175 psi

Personally, I feel my compressor is the minimum for a 1 man shop. It will run all the air tools, sandblast cabinet, pressure pot blaster and spray guns I have.
1968 Coronet R/T


ACTS 16:31

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PostPosted: Tue Jan 17, 2023 6:57 pm
I don't trust compressor "ratings". They're usually what the market wants or what the manufacturer wants to tell you.

Simple way is to connect your gun to the compressor with any hose(s) that you'd normally use. Fittings and gun settings as normal.

Half fill the gun cup with water and then just pull the trigger. Watch the pressure. If it goes down and continues falling then your compressor doesn't have the capacity the gun needs. If the compressor switches on, then off for a bit, then on again and cycles like this then you're good to go. If it struggles a bit, try duplicating what would happen when you're painting. So pull the trigger all the way for about 3 second, release for a second and repeat. Again, listen to the compressor - if it just runs constantly and can't keep up the pressure then you're in the market for a new/bigger one.

Do the same with an air hog, like a 6" DA, set to about 40-50psi. If your compressor can maintain pressure then you have capacity for tools like this as well.
Chris



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PostPosted: Wed Jan 18, 2023 9:46 am
'68 Coronet R/T wrote:Your compressor should have a sticker on it or you can look it up online.

Compressor Specs.JPG


Notice that pump puts out 18.9 CFM however when under pressure the output drops down.
15.6 SCFM (Standard Cubic Feet per Minute) at 100 psi
15.2 SCFM at 175 psi

Personally, I feel my compressor is the minimum for a 1 man shop. It will run all the air tools, sandblast cabinet, pressure pot blaster and spray guns I have.



That about the same as my compressor, I've used it for years no prob. I just want to know the exact cfm I'm getting right at the gun. I'm not having any issues and am prob over thinking this as I usually do, but I just want to know if I'm getting the 10 to 12 cfm at the gun.

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PostPosted: Wed Jan 18, 2023 11:23 am
If your compressor is adequate, then the line and fitting sizes would be the only possible restrictions.

3/8" minimum on your air hoses, high flow fittings and be sure to check the fitting sizes on your water separator/regulator set up. Some of them have 1/4" diameter fittings which will reduce air flow.

Chris's idea of using water would be a quick test.
1968 Coronet R/T


ACTS 16:31



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PostPosted: Wed Jan 18, 2023 12:47 pm
'68 Coronet R/T wrote:If your compressor is adequate, then the line and fitting sizes would be the only possible restrictions.

3/8" minimum on your air hoses, high flow fittings and be sure to check the fitting sizes on your water separator/regulator set up. Some of them have 1/4" diameter fittings which will reduce air flow.

Chris's idea of using water would be a quick test.



Sounds good, I will try that, thank you all.

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