HVLP questions

[luc gendron]

Hello,

Thanks to those of you who helped me choose my compressor. I opted for the Husky (Campbell) model from home depot. Now I've purchased my HVLP spray gun and used it for the first time today. Here are my questions:

1. Should there always be air coming out of the gun? As soon as I connect the air hose to the gun, air blows out of the gun on a continual basis...is this normal? This in turn forces to air compressor to run full cycle.

2. Why is there a pressure gauge at the end of my gun. Can I not use the pressure control gauge at the compressor's end? Also, I could not get a good spray pattern unless I regulated the the compressor at 90 psi and the gauge at the gun at 40 psi. Why is that?

3. Where is the best place to install a water and oil filter, at the gun end or coming out of the compressor? I opted for the filter at the gun intake (thinking this would eliminate any condensation forming in the air travel from the compressor to the end of the 25 ft hose) but some water leaked out of the filter as I tilted the gun on its side to get at a thight spot.)

4. Why are people still using standard spray guns!! For 10 years I hesitated at HVLP but from my first experience...what a great tool. Almost no spray mist, hence the perfect solution for those of us with small to medium workshops and without a spray booth.

Thanks in advance for your responses!

[keith ouellette]

The type of spray pattern you get is sometimes related to the type of liquid you are spraying. Latex paint doesn't flow as well as oil. The thinner the better. No air comes out of the end of my gun until I pull the trigger. I have my filter at the end of my main line but before my air hose and this seems to work well but make sure you have a water and oil filter and not a filter and oiler.

[Charlie Plesums]

My "conversion" hvlp gun - that runs on a regular compressor - is a non-bleeder gun. The trigger first starts the air, then the fluid. This is important with a small compressor.

My "turbine" hvlp gun is a bleeder gun, where the air runs continuously. I believe it is because the turbine expects a continuous air flow.

I run 100 psi at the compressor, but only about 20 psi at the gun, which (I am told) drops to about 5 psi at the tip. If you double the pressure, you cut the volume of air in half. Therefore with normal air hoses, you need a fairly high pressure to get enough air through the hose, but you let it expand in the gun to high volume and low pressure.

If you need 40 psi at the inlet to most HVLP guns, your material is probably too thick. Try thinner (what are you spraying? How thin is it?)

I used a water and oil filter for several years, but collected almost nothing in the filter. Guess I was just lucky, but didn't have a problem.

Although it isn't a page specifically on spraying, I do have a web page on finishing furniture that you may find helpful www.plesums.com/wood/tips/finishing.html (http://www.plesums.com/wood/tips/finishing.html)

[luc gendron]

Thanks Charlie,

I'm spraying latex paint at the moment. It is thick, so I guess that is why I need 40 psi at the gun end. I guess I purchased a ''bleeder type'' gun. I tried to ask questions at the store (Princess auto in Canada) where I bought the gun put you now how it is, kids working in supposedly professional hardware stores. I'll bring it back and shop for a non bleeder type gun as my compressor (26 gallon) is working hard pushing for wasted air....Why would they make a bleeder gun that will be attached to a compressor? Seems it is just wasting? Is there a purpose for this air to be running all the time?

[Jim Becker]

1. Should there always be air coming out of the gun? As soon as I connect the air hose to the gun, air blows out of the gun on a continual basis...is this normal? No paint or finish however until I release the trigger. This in turn forces to air compressor to run full cycle.

It sounds like it may be a bleeder gun...and if so, the air will escape constantly. A pressurized gun will not do that.


2. Why is there a pressure gauge at the end of my gun. Can I not use the pressure control gauge at the compressor's end? Also, I could not get a good spray pattern unless I regulated the the compressor at 90 psi and the gauge at the gun at 40 psi. Why is that?

HVLP conversion guns generally specify that the compressor pressure be between 40 and 90 PSI and the pressure at the gun be reduced to some number. My Wagner performs best with 40 PSI from the compressor and 15 PSI, more or less, at the gun regulator. Every gun is different relative to the combination. (I have a special line just for spraying finishes that has a mini-regulator set to 40 PIS all the time while the rest of my system is regulated to 90 PSI just past my filters near the compressor)


3. Where is the best place to install a water and oil filter, at the gun end or coming out of the compressor? I opted for the filter at the gun intake (thinking this would eliminate any condensation forming in the air travel from the compressor to the end of the 25 ft hose) but some water leaked out of the filter as I tilted the gun on its side to get at a thight spot.)

Filtration is usually installed just off the compressor, although some folks will also run a disposable moisture filter closer to the gun, too.


4. Why are people still using standard spray guns!! For 10 years I hesitated at HVLP but from my first experience...what a great tool. Almost no spray mist, hence the perfect solution for those of us with small to medium workshops and without a spray booth.

HVLP certainly can reduce things like over spray a good part of the time, but again, every gun is different. Many people use "standard" spray guns because that's what they have, or that's what came with their compressor. Some pros even prefer them for certain tasks.

[Charlie Plesums]

Thanks Charlie,

I'm spraying latex paint at the moment. It is thick, so I guess that is why I need 40 psi at the gun end. ......
If you will be spraying a lot of latex, I suggest that you spring for an airless sprayer... even the widely available $300 Graco is better than forcing an HVLP system into that thick paint. On the other hand, in my experience the HVLP systems are far superior when fine atomization is required, such as furniture finishes.

Of course, this comment will probably start a war, since I have read posts by some people who have great success spraying lacquer with an airless sprayer, and some who have had success using an HVLP system for latex, but I spent my $300 and am glad I did, and it won't replace either of my HVLP systems. ;)