Sunday, June 24, 2012

Priming – A Comedy Of Errors

Today was a mixture of the Good, Bad and downright Ugly as the DOG Aviation paint department utilized the new Eastman spray gun, digital regulator and the DeKups disposable painting cup system by DeVilbiss. The primer of choice is a two part epoxy primer made to Boeing specifications by Akzo Nobel.

First the good … The parts primed today turned out marvelous and the spray painting box worked great… but getting there was nothing less than a miracle.  The entire morning was a perfect day for spray painting … not breathtakingly hot and humid, no wind ... almost a dead calm with an occasional swirl of air. Mixed up a batch of the Akzo and let it sit the 30 minutes required mixing occasionally. OK good to go!

The Bad - While the primer was sitting the required 30 minutes the shiny new spray gun was removed from the box, digital regulator attached, followed by a water separator and connected to a 50’ 1/2” hose. ( Eastman recommended only using a max of 25’ hose which just was not long enough so I figured if one were to use a 1/2” hose there would be less restriction to the air flow). So far so good ... maybe. Next tried to adjust the pressure regulator at the gun to the required 29 PSI … think the best I could get was 19 PSI so I turned up the regulator at the compressor to 120 and that got it up to 22 PSI. Decided to remove the water separator and that got the pressure up to 26 PSI. Close enough, so decided to put paint in the gun.

The Ugly – The primer was mixed in the disposable DeKups liner, liner placed in the cup, on goes the locking ring … good to go. Turned the gun upside-down, attached the assembly to the gun, pulled the trigger and nothing … no paint, no collapsing paint bag. ( Pulling the trigger with the HVLP gun upside down is supposed to bleed the air out of the paint cup by collapsing the bag until there is no air in the bag making upside down painting possible). Now at this point I know there is something wrong, but I haven’t connected the dots just yet. So I decided to move on … figuring I’m not planning to paint upside down, so I’ll just use the cup as a gravity feed .. right? WRONG! When I turned the spray gun upright I pulled the trigger and was looking at the pressure gauge so did not notice the paint pouring out of the fitting where the DeKups locking ring attaches to the gun. The gun is just covered with dripping epoxy primer!!!

More Ugliness - Then to add insult to injury, when I disconnected the gun from the air hose the quick release valve broke … air was just hissing full blast out of the hose so I had to run back, disconnect at the compressor and find a replacement quick connector.

After changing over to the paint cup that came with the spray gun, the job got finished and the results were encouraging. I was able to lay down a nice thin coating of primer on the parts with no runs. I was never able to get the regulator pressure up to 29 PSI but the gun seemed to work well at 26 PSI. At this point not sure if the digital gauge is reading low or if I just can’t achieve 29 PSI at the gun even though a hose with a larger diameter was used.
While cleaning up the winds kicked up so began transferring parts inside. The small parts hanging were OK but one rib hit the ground. Fortunately it was dry enough not to have any grass stick onto it.

                                       Cleaning up the aftermath of the mess still wondering what went wrong.

A Senile Delinquent moment … After literally spending hours trying to scrub off dried Akzo from the gun and all the accessories (no easy task with Akzo primer) and wondering why all the paint had leaked out in the first place, the dots finally got connected. Could the metal adapter have been machined wrong or perhaps the plastic locking ring was molded incorrectly (it did not look like a tight fit) or could there have been a rip in the liner. Nope … just didn’t know what the issue was. Anyway, while cleaning things up, I discovered there was an unopened box on the table … an unopened box of lids. Yes, you read that right LIDS!!!!  In my over exuberance to get painting I forgot one very important step … putting a disposable lid on the disposable liner BEFORE placing the liner in the cup holder and putting the locking ring on it!  DUH!!! Won't be making that mistake again!!!