Air pressure varies

[Bob Kontak]

When I use my DeVilbiss HVLP gun with a regulator at the input to the gun, the pressure is at 50psi but when I pull the trigger it drops down to the high 20's which is where I want it to paint.

I don't notice this with my small gravity gun but I shoot at plus or minus 55psi with only the compressor regulator aside from the gun regulator. Right now I have 80 feet of the regular old reddish hose. Could the gun regulator be the problem?

I remember Porsche962 talking of a special hose you use for HVLP guns but I am not sure if this is for keeping pressure constant.

[962porsche]

with HVLP you have to have the hole system HVLP hose ,fitting every thing right from the air tank to the gun .
at the gun regulator you would want it set around 30 to 40 LBS as you pull the trigger on the gun letting air out with out product coming out of the gun .
when you release the trigger on the gun the air pressure will go up on the regulator .
you set the pressure with the trigger on the gun pulled back .
of course when you let off the trigger the pressure will go to what the tanks pressure is .

[Bob Kontak]

Originally Posted by 962porsche

of course when you let off the trigger the pressure will go to what the tanks pressure is .

Thank you. Jeebus - that is is.

I bought a newer compressor that goes up to 140 PSI. My old Craftsman DeVilbiss compressor topped out at 90 making the change of pressure not as noticeable especially shooting with a gravity feed gun.

[962porsche]

adjusting the guns pressure is ez .
just pull the trigger back so your only getting air coming out of the gun then set your pressure with the regulator on the gun at 30 to 40 lbs . the pressure at the gun will depend on how wide your spray pattern is .
when you let off the trigger the pressure at the gun will go to what ever your tank has in it .

[Bob Kontak]

Originally Posted by 962porsche

when you let off the trigger the pressure at the gun will go to what ever your tank has in it .

I have a feeling this is going to be embarrassing................

When I make a pass on a panel, I just let off the trigger completely.

I have no issues with dialing it in at the "just air" point but I think you are going to say don't let off the trigger the whole way at the end of a pass. Just let off enough to stop the paint flow.

[962porsche]

that is a yes and no answer !
it depends on what I'm spraying .
if I have a panel / part on a stand I let off all the way as the air pressure may hit the wall or floor and kick up dust or if there is more then one part in the booth the air could hit some thing I don't want it to .
if I'm say spraying down the side of a car when I get to the end I will just let off enough to stop the product from coming out and move to go back down the side of the car .

I also will not just pull the trigger with the gun pointing at the floor and then start across a panel . this will also kick up unwanted dust .
when you 1st pull the trigger you will get a quick blast of air then it will settle down to spraying pressure .
this is one of many reasons to start off a panel and end off a panel .