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Air Pressure

Chris_Hamilton

Trying to be the best me, I can be
#22
Found the article I was looking for from the Sata Newsletter from 2015. My scanner is broken on my crappy printer so I took 2 pictures of the article. You'll have to go back and forth between the two pics. Sorry about that but the article is worth reading. They even used my straw analogy :) Anyways this is exactly what the German SATA rep told me in 1999.
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Barry

Paint Fanatic
Staff member
#24
Like I say 5 to 10 times a week, its the net result that counts and nothing else.

By the way, there have been three different engineering studies on this since about 1990.
I have proven a lot of their findings myself, like flash times, amount of paint usage and gloss readings as well as metallic, orange peel and run control.

So do whats works best for you, and while we're at it, let's make it clear none of these effects a paint under 39% solids, lacquer, enamels, or noncompliant guns.

I hope you all have a happy thanksgiving.
 

Chris_Hamilton

Trying to be the best me, I can be
#25
@Barry, not trying to be argumentative....just trying to understand. How does it make a difference whether at the wall, or the gun? Only thing I can see that is different is the length of the hose. But that should be a non-issue with 3/8'' hose, 35ft and high flow fittings. And the part I really don't understand if you are putting full pressure to the regulator at the gun, the gun doesn't see that, it only sees what's coming out of the regulator. What is the difference that would affect the items you listed above? Also any proper diaphragm type regulator is going to have more flow capability than a gun mounted diaphragm type regulator. Doesn't make sense to me.
Everything else being equal...meaning two identical correctly setup air lines and compressor, you feel there is more of a benefit to running full pressure to the gun regulator versus to the wall regulator and adjusting there? What am I missing? I'd appreciate your thoughts. I'd like to read those studies too if they are online anywhere.
 
#26
the idea is that the air hose is a restriction so what you set on the wall isnt what you have on the other end. higher psi will make sure you have enough air directly at the inlet of the gun. for 20 years i have always run 100 psi or so at the wall.
 

Barry

Paint Fanatic
Staff member
#28
Cris, no problem at all this, has nothing to do with spi, so I offer them help, and it works, or it doesn't..
Im not writing a 20-page explanation, so read the part where I proved some of their points and think about it.

When a professional painter calls me with one of the following problems, what is the first question I ask?
Orange peel
Runs
Flash is too long
Metallic with quality base, problems.
Clear is cloudy the next day
Solvent pop in the first coat of epoxy
Solvent pop in 2nd coat of clear

What is air pressure at the wall set at?
Why is the answer 9 times out of 10, 70 to 80 lbs?
If 125 at the wall or higher, then we go to the next question.

Like I said, net results all we care about, so if your way works, don't change it.
 
#29
when i learned to paint we had a ball valve on the wall to shut the air off /on . some places even had a water shut off valve .
the old saying applies here , if it works dont fix it !

if you think painting is hard today try painting a car in lacquer with no time for cut and buff .
 
#30
What I have observed is that it takes 60 psi at the regulator to get 20 psi to my Iwata LPH 1.4 tip.

I have at least 3 gun pressure regulators that I attached to the gun the first time I tried this. All of them read the same.
That's through a 35' 3/8" Flexzilla hose with high flow fittings.

When I set up my other spray guns that require 30-35 psi at the gun, my wall regulator is now in the 80+ psi range.

The point I am trying to make is setting the wall regulator at 100 psi and using a regulator at the gun is not changing the overall pressure setting that much. So is it really "choking" the volume of air enough to make any difference?
 
#31
68: 60 psi at the wall regulator through 35' of 3/8" hose ends up 20 psi at the gun? That seems like an excessive amount of pressure drop.
I use one set up similar to what you do that is about 35 psi at the wall regulator and I get 30psi at the gun. 3/8" hose with hi-flo fittings. I rigged up a small tee with a gage at the gun to make sure. So that 's only about 5psi drop with 38' of hose.
All the other guns have a diaphragm regulator and I feed them at the wall at about 85 psi. I tried to feed that set up higher but noticed fluctuations at the gun I think because I was above the pressure where compressor turns back on. The compressor cycles from 100 psi to 150 psi.
I agree it's all about results. Another good discussion!
 
#32
68: 60 psi at the wall regulator through 35' of 3/8" hose ends up 20 psi at the gun? That seems like an excessive amount of pressure drop.
I use one set up similar to what you do that is about 35 psi at the wall regulator and I get 30psi at the gun. 3/8" hose with hi-flo fittings. I rigged up a small tee with a gage at the gun to make sure. So that 's only about 5psi drop with 38' of hose.
All the other guns have a diaphragm regulator and I feed them at the wall at about 85 psi. I tried to feed that set up higher but noticed fluctuations at the gun I think because I was above the pressure where compressor turns back on. The compressor cycles from 100 psi to 150 psi.
I agree it's all about results. Another good discussion!
Interesting. I will need to take a look at the particulate filter set up just before my air hose. If there is a restriction it might be there.

Again, 85 psi is not far from 100 so it does make the case for there not being much difference.
 
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