Troubleshooting Painting Problems with an Air-Assisted Airless Gun

      What's causing the spray fan to "wink out" occasionally? Pros help pin down the cause of poor performance. January 9, 2007

Question
I have been in paint for over 17 years - eleven years as a house painter doing custom homes and five years in a paint store selling Benjamin Moore. For the last 2 years, I have worked in a cabinet shop running the paint line. I have, for about the last 18 months, been using the Kremlin systems. We spray Akzo-Nobel Rel-Plaz.

I have read that several of you are quite impressed with these systems. I have not been very impressed, but I am now wondering if our setup is wrong. We follow the rep's advice to catalyze, but have trouble with dry spraying and runs. The spray fan consistently winks out while spraying. Most everyone that I put back there has problems. I have some, but not nearly as much. When the pump is set up in the morning, we generally set it at 300# fluid and about 17# of air. We use a #9 tip. I have sprayed a lot of clear finish, but have never had this much trouble getting it to lay nice and smooth. Also, has anyone had experience with the Rel-plaz failing? It tends to peel easily.

Forum Responses
(Finishing Forum)
From contributor T:
Have you replaced any of the tips? We have three 10:14's. After a couple of years and several hundred gallons, we replaced them - erosion from all the material and cleanings. Couple of .001 made a difference in the spray pattern.



From contributor R:
It seems to me 17# of air is way too high in relation to 300 on the fluid.


From contributor J:
I have been using an AAA gun for many years. If your finishers are used to HVLP or conventional, they will have to change some spraying habits. AAA lays out 45% more material at one time than other guns, so they do have to spray faster. The "winking" youíre experiencing is from air in the fluid line or a dirty gun filter (the filter in the handle). Try this. Put on a coat with just enough overlap to not leave dry lines. Let it flash off for 3 minutes, then go back and give it a 50/50 overlap pattern. I have found you will get less runs and a more uniform coat. Also keep in mind that when youíre spraying, the pattern will take a few seconds to flow out, so donít try to get an instant wet pattern right behind the gun with one pass, or it will be run city.


From contributor D:
If your coating is peeling, you have an adhesion problem. Problems with a coating's adhesion or with intercoat adhesion are caused by poor and/or inappropriate surface prep. You should be working with your Akzo-Nobel finish rep to see what it is you are doing to cause your finish to peel. If your rep is no help, then you should be on the phone with Akzo-Nobel's tech support to nail down what you are doing to cause the defect. Are you following the tech sheet to the T?

Generally, substrates are sanded to 150 grit, 180 grit if you have to. Between coat scuffings are done with 320 grit. If you are laying down your coating over a wiping stain, whose stain? Are you allowing enough dry time for the stain? If it's not an Akzo stain, are you positive that the stain is one which has an alkyd binder and not linseed oil?

If you are doing a glaze coat, are you leaving an accumulation of glaze (too thick a glaze)? Are you doing a vinyl sandwich? Are you using the recommended Akzo-Nobel glaze for your coating? These are the details you need to work out with your finish rep. You must be a pretty big shop if you are using Akzo-Nobel. Either that or you are using their only over-the-counter sales in Phoenix to get your goods.



From contributor O:
In relation to your problem with the fan "winking," replace the fittings on the suction rod where the rubber meets the stainless steel rod and also the nut that hooks to the fluid section with regular hardware store hose clamps. The older style clamps were leaky and could cause you to suck just enough air. That would be a simple fix.

Also, if that doesn't fix your problem, look into the inlet and outlet valves as well as the GT cartridge at the throat of the pump. If the GT cartridge is clogged with dried finish residue, it can cause the piston rod to not move freely and potentially cause you problems.



From contributor Y:
The other comments are on the right track. Winking is a pump problem, not a gun problem. I would first perform a stall test. A stall test is this: pressurize the pump and gun. Trigger the gun with the tip in place. Watch the piston in both the up and down stroke. When you are not triggering, the piston should instantly stall and no longer move or creep. If it stops for a minute and does not move, you do not have a problem with the upper or lower ball. If it does move, you have some debris stuck in one of the balls.

Next I would inspect all filters, including the one in the gun. Make sure there are no obstructions. Next check the suction assemblies to insure that there are no air leaks, thus preventing suction out of the container.

I would think you should be running 300psi to 500psi on the fluid side and 8 to 12psi on the atomizing air side. You may want to try a larger tip, which allows more material to come. Most larger shops with overhead lines use a 12-154 tip. You may also want to try the new double atomizing tip - the 12-152 Ultra.

Also, I believe that Rez Plaz is acid catalyzed and you will want to be sure all hoses, fittings, couplings, etc. are stainless steel. If they are not, you could get something called copper ionization. This is where the copper ion migrates out of the fitting because of the acid (happens with some WB coatings too) and creates a hardened obstruction in the fitting or hose.

If you are using a large amount, you should consider a portioning system to mix your 2K products.



From the original questioner:
The reason that we turn the air pressure up so high has to do with the tip fingering. I agree with the lower pressures - it makes sense, but has not worked.

The AKZO rep has been little help and will not come to see me. I pissed him off when I questioned his product. From the info that I have received, he has changed the catalyst amounts 3 to 4 times and I know this is not good. The drum says 3.2% catalyst. I have not done the math myself, but the standard they came up with was 3.8 oz per gallon. Then they went to 4 oz. per gallon.

This summer when the temp spiked over 100 in the shop, we had a viscosity problem. He then told us no more than 3 oz. I cut back to 2.5 and added acetone to aid in drying and the problems stopped. Now that the temp is going down, I have increased to 3 and now they are recommending 12 to 12 1/2 ounces of butyl acetate per gallon. This supposedly is to help with the adhesion problem.

The stain that we use is an Akzo product that is tinted by our employees. We offer custom colors. We use a lot of the Akzo product - they purchase it by the drum.

Tip wear is a big issue with me. I am at odds with my maintenance department over that and over the pump maintenance.

My feeling about the winking goes back to my experience with the airless setups I am used too. (I also received factory repair training with several companies.) I feel that the setups do not have a big enough or long enough set of lines. They use cheap clear tubing for the air hose to the line. They also use short 8 to12' fluid hose that I used to sell as whips for the airless. I believe they are in the 3/16" range. I have asked to speak with the Kremlin reps also, but have not had any success there either.



From contributor H:
Hopefully you have solved your winking problems by now. If not, I would suggest you put in a 25 foot hose on your fluid line. The Kremlin pump is designed to use at least 25 feet of hose. This length will absorb any fluid fluctuations that occur during pump cycling. Shorter lengths will wink, especially if they are only 10-15 feet.


The comments below were added after this Forum discussion was archived as a Knowledge Base article (add your comment).

Comment from contributor C:
The winking that you are referring to is very common to airless or air-assisted spraying. It is caused by pump surge. When the pump rod switches direction it causes a slight loss in pressure then surges back to normal. To correct this problem you need to install a fluid pressure regulator ahead of the gun hose. Set this regulator lower then the pump outlet pressure, and the "wink" should be fixed. Just make sure you get a high pressure regulator. Your Kremlin rep should have the info.



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