By the books?...

[Stretch]

I've got the DeVilbiss GTI gun and haven't done much with it yet. I did do a half helmet with some PPG black base, blue pearl flames and clear and it turned out really well for my first effort. I had the regulator from my compressor set at about 35psi (assuming I'd lose a bit of pressure between the 50ft hose and the gun). With a bit of adjustment (based on what I've read on this site) everything seemed to work fine.

Anyway I was cleaning out the garage today and ran across the paper for the gun. Included in it was a small tag that recommended about 30psi at the gun with the trigger pulled. So I popped the gun on just to test that out and even with the compressor (Craftsman 6hp 33gal) turned up to 120 psi, the gun wouldn't read over 20 psi with the trigger pulled.

No big deal, the gun worked for what I needed but I wanted to get feedback. Do you think I lucked out with the helmet or is the recommended psi just that, a recommendation. I'm sure my next job will answer my question, but any feedback you all have would be much appreciated.

Thanks-Stretch

 

[rex]

The pressure is a recommendation but you're low no doubt.I'm kind of surprised you didn't get drips off the rivets shotgunning it on with low pressure.Round surfaces are kind of forgiving so that could be why it didn't let loose,it all flowed to the bottom,but you must have done a nice job laying it out evenly.Try running pressure at the gun 30-40lbs,you'll get better atomization.

 

[Stretch]

Thanks for the reply rex. I've got a few problems though. As I mentioned, I had the regulator set to 35psi and got some good results.

You recommend running the gun at 30-40 psi, the trouble is that even if I set the compressor regulator up to 120psi the gun won't get above a 20psi reading with the trigger pulled.

When I tested the gun last I put the pressure up to 120 psi and even though the gun didn't read above 20psi with the trigger pulled, the gun itself was blasting out air. I can't imagine spraying paint at that pressure without getting tons of overspray. Maybe the reading at the gun is incorrect.

I'll keep testing different settings but any recommendations would be appreciated.

Thanks-Stretch

 

[rex]

Whoa,something's odd.Does the GTI have a built in regulator?I use the Sharpe regulator between the fitting and the handle but they don't seem to handle being soaked in thinner like DeVilbiss' can handle.I think the Sharpe goes about $15.If you already have one in that place I'd say it's bad,get a new one.I think pressure drop through 50' of hose is around 30lb or so,so you should have at least 60lbs going in the gun if there's 120 at the other end of the hose.

 

[Stretch]

Thanks Rex. I could be losing too much pressure. I've got the compressor out in my shed and there's a 25' hose coming into my garage. I keep the pressure gauge at the compressor set to 135psi. I then have another regulator and water trap inside the garage. I use that regulator to adjust the pressure I need. It can easily get to 120 psi so I may be losing 10 psi in that hose.

The regulator on the gun came with it and fits between the handle and fitting. It could be bad but I doubt it. It's new and has only been used a few times.

Now since the regulator in the garage can easily get to 120psi that indicates that pressure drop isn't the problem correct? According to the manual, the gun needs a max of 30psi at the handle to deliver the 10 psi at the nozzle. I know I can't be losing 90 psi from the garage regulator to the gun. Maybe the regulator on the gun is bad after all.

I know we haven't talked much of CFM but I figure that a 6hp/33 gal should handle helmets and tanks. I think it's rated at 9cfm @ 40psi. Not ideal but enough for an occasional small job right?

The manual also says to ONLY use the HVLP quick disconnects sold by DeVilbiss. I'm using the basics that can be found at the local hardware store. I wouldn't think that's a problem.

Thanks so much for all your help. It is truely appreciated.

-Stretch

 

[Stretch]

Checked some stuff again this afternoon. The gauge at the gun reads 100psi with the trigger off but drops to 20psi with the trigger pulled. Tried to get another gauge today but the store I stopped at was out of them. Does this sound like a CFM problem or could it still just be the gauge?

Thanks-Stretch

 

[rex]

I'm thinking it's a cfm prob.I'm not experienced with HVLPs but they do like to eat air.Since you're losing 80lbs just pulling the trigger I'd say the compressor can't supply enough air.Since the helmet came out good I'd say you can skate by on the smaller stuff but I wouldn't tackle anything big without a bigger compressor,you'll get to a point the compressor can't maintain the 20lbs and you'll lose pressure fast.

 

[DDG]

I'd say it's the regulator. I've got a 5.5hp 25gal
and with it set at 70lbs I can easily set my gun reg. at 25-30lbs with no problems of the comp. keeping up. It goes through about 40ft of hose.
I know on my gun there's also a screw on the bottom of the handle, and if it's screwed out I can't get any pressure over 10lbs.
I use a Warwick hvlp so it might differ from yours.
Good luck,
Dirt