Refrigerated Air Dryer

[Ronf]

Yesterday I replaced my refrigerated air dryer that supplied the paint booth only with a larger unit to handle both booth and shop. Old unit was rated for spray equipment up to 15 cfm. The new unit, which is an SPX-Deltech 50 CFM Refrigerated Air Dryer is now installed to handle both the paint booth and the shop area (trying to keep moisture out of shop air tools). As to ensure the paint booth had no problems for future projects I set up three practice panels in the booth, 24" x 48" 18g panels and sprayed them out with 2 stage paint. Prior to panels being sprayed they were sanded with 80g followed by 180g and finished off with 320g. These were then covered in a non-sanding 2 part epoxy primer (PPG DP50LF) with no issues. Today, 24 hours after epoxy was spray, I shot the BC and clear coat to TDS specs with high quality products (PPG DBC2000 base and DC3000 cc). Base coat was reduced to spec with a medium reducer (75-90 degrees) and a catalyst added at 5% rts (catalyst is an option per tds but my normal way to shoot base). Base went down great with no problems. However, clear coat had a load of solvent pop, about 1 pop every 2 sq. inches, which surprised me as all these products are familiar too me as well as my booth being maintained at 72 degrees year round. I'm trying to figure out why these solvent pops are now occurring in JUST the clear after doubling the flash off time from the base. I understand my booth temp is maintained below the 75 degrees minimum called for in the base reducer but it was never a problem in the past at 72 degrees. My guess is the size of AC dryer I replaced my old unit with along with the catalyst I use caused this problem but not completely sure. Any thoughts? I need to get this resolved before I can use the booth again.

[Bob K]

I’ve generated that kind of solvent pop by testing to see how low pressure at the gun would affect the paint. I lowered from the normal 28psi to about 10psi with the trigger pulled. The solvent pop took several hours to develop. Maybe your gun filter got clogged with something that was introduced into the air line while you were doing the plumbing.

Bob K

[Ronf]

I’ve generated that kind of solvent pop by testing to see how low pressure at the gun would affect the paint. I lowered from the normal 28psi to about 10psi with the trigger pulled. The solvent pop took several hours to develop. Maybe your gun filter got clogged with something that was introduced into the air line while you were doing the plumbing.

Bob K

Bob,

I actually thought the same thing in that I was introducing air into the cup. However, as I use the 3M PPS cup system in which the entire lid of the cup is a filter and seal I don't see how I could ever clog the filter or introduce air. I think you may have hit upon something I have not thought about with your previous experimenting in which the CC was laid too heavy (I'm guessing your experiment with an incoming pressure of 10 psi, giving you somewhere around 3-4 psi tip pressure, was laid too heavy) and introduced air. I am experiencing the exact same problem in that the solvent pop, on clear coat only, doesn't occur until an hour plus after hitting the panel. I'm thinking the dynamics of the shot has change since replacing the refrigerated dryer with a bigger unit and maybe I need to cut my product flow or up the pressure and move faster or extend off gassing time between coats, your thoughts?

[Bob K]

For me it was that the clear was going out with very little air pressure and it wasn’t atomizing very well hence the solvent wasn’t evaporating in the air stream like it would under higher pressure.

Bob K

[bmarler]

i think bobk could be onto something with the filter thing. (assuming you run an orange bulb on the gun) there could have been some residue in the dryer's plumbing that fouled that filter.
i had something like that happen to me once. i always use a new bulb for an important spray session, but i remember a time when i set up a new hose/regulator something came loose and partially blocked the bulb. these new guns take so much air to atomize properly so the reduced flow made a huge difference. it took a while to figure it out cause my gun gauge still read fine but the paint just didn't come out right.

[Ronf]

i think bobk could be onto something with the filter thing. (assuming you run an orange bulb on the gun) there could have been some residue in the dryer's plumbing that fouled that filter.
i had something like that happen to me once. i always use a new bulb for an important spray session, but i remember a time when i set up a new hose/regulator something came loose and partially blocked the bulb. these new guns take so much air to atomize properly so the reduced flow made a huge difference. it took a while to figure it out cause my gun gauge still read fine but the paint just didn't come out right.

First, let me thank each of you for your input. If both of you had not been persistent when referring to a filtering problem I would never have discovered the discrepancy and yes I think I found and nailed the problem. The one problem I shrugged off quickly was the inlet paint filter as I use the 3M PPS cup system that has a 4" lid filter which is virtually impossible to clog (I say virtually as I did manage to clog it on one occasion with some bad sealer). Also, before product goes into cup I also use a doubled up cone filter too ensure the product is properly strained (see pics). Since the problem was discovered in the new air system I'll follow this reply with a separate ongoing post to ensure new and old members can learn from my mistakes, see follow up post that will include pics of problem.

[Ronf]

15 plus years ago when I went to an refrigerated air line cooler I quit using paint gun water traps, big orange bulb hanging off the end of my guns, as they were no longer required with the AC line cooler and I absolutely hated them hanging off the end of my gun as they only caused obstructions when painting. A few days ago when I installed the new replacement SPX-Deltech 50 CFM Refrigerated Air Dryer it required the 1/2" hard line copper tubing to be reconfigured which meant sweating in new K copper lines. Normally when I sweat copper lines of this type I always introduce Argon into the tubing to ensure I don't introduce flash back products and corrosion into the system, however since the new sweat on tubing and fittings to be installed was post refrigerated plumbing that would be exiting the air outlet on AC unit I saw no reason to infuse the Argon, big mistake on my part. Because both of you kept referring to and were insistent on this being a filtering problem I decided to tear down my post AC filtering units and look for problems. This is where I discovered the problem! I use a Deltech 810 series filter and water trap designed for paint booths along with a Deltech regulator. Look at what I found after tearing down the filtering unit.E.jpgB.jpg

[Ronf]

Hopefully after cleaning and filter replacement (Luckily I had an extra filter on hand) this will end the problem.

[Bob K]

Wow, did any of the powder get past the white filter and get into your gun? What is it? Desiccant? There looks like too much of it to be copper oxide but I don’t know how fast copper deteriorates in a hot air environment.

Bob K

[Ronf]

Wow, did any of the powder get past the white filter and get into your gun? What is it? Desiccant? There looks like too much of it to be copper oxide but I don’t know how fast copper deteriorates in a hot air environment.

Bob K

Bob,

No it is not Desiccant nor was any of this debris present when I first set this system up years ago. If fact I replaced the 810 Deltech canister cartridge filter with an 812E a few years back (812E is designed for paint booth application) and found nothing present. All of this corrosion material has to be from the newly relocated lines, wow what a shock! The newer Deltech replacement filters, which I just happen to have on hand, omit the spring and foam pre filter, making it a much easier and better filtering system too maintain. Just glad I finally found the problem in a timely manner thanks to you and bmarler!

[Bob K]

Thanks for the kind words but I did not think the problem was that far back in the air line. I thought it was between your gun pressure gauge and the gun tip. I’m glad you have it worked out.

Bob K

[bmarler]

that's a surprising amount of debris in that filter. glad you got it sorted out. like bobk i thought the problem was further downstream.
i totally hear you about the bulk of the gun with the bulb on it but i've made my peace with it. mine is probably more bulky than most as i run an actual regulator instead of a needle valve at the gun inlet as well as the orange bulb. but with the dekups system allowing any gun orientation without sputtering i make it work just fine. i just remind myself it's better than the old drippy cup/bandana hanging off the gun.
if i really need the gun to have the mobility i'll put a new section of polyethylene hose between the regulator/bulb. then i can hold the regulator or drape it across my back and run the poly hose down my arm. i never skip the gauge at the gun inlet though, gotta have that.
your pictures make me want to disassemble my paint airline filter though to clean it and service the desiccant.

[S-C]

Hi Ronf,

Very happy to hear you resolved the problem, OR DID YOU?

This seems to still be up in the air.

Yes, your filter assembly was contaminated with loads of particulates that you cleaned out and replaced the cartridge filter, but you make no mention of this debris ever making its way into your paint. You referred to the problem as solvent pop, so I’m thinking a dirty filter may not be the cause unless the filter was so dirty that it restricted flow to the air cap resulting in poor atomization with paint being laid down to heavy.

Thing is, you would have noticed the low psi at the guns regulator, yes?

Possible moisture in the line? I think that would have shown up immediately in the form of fisheyes?

If it’s truly solvent pop, my understanding is the solvents are being trapped within for whatever reason and showing up later as they escape.

????

[Ronf]

that's a surprising amount of debris in that filter. glad you got it sorted out. like bobk i thought the problem was further downstream.
i totally hear you about the bulk of the gun with the bulb on it but i've made my peace with it. mine is probably more bulky than most as i run an actual regulator instead of a needle valve at the gun inlet as well as the orange bulb. but with the dekups system allowing any gun orientation without sputtering i make it work just fine. i just remind myself it's better than the old drippy cup/bandana hanging off the gun.
if i really need the gun to have the mobility i'll put a new section of polyethylene hose between the regulator/bulb. then i can hold the regulator or drape it across my back and run the poly hose down my arm. i never skip the gauge at the gun inlet though, gotta have that.
your pictures make me want to disassemble my paint airline filter though to clean it and service the desiccant.

Marler,

On your Dekups can you invert your gun 180 degrees and never miss a lick regardless of spray out length/time? On my 3M PPS system you have about 1-3 seconds of spray time when inverted before you hit dead air, almost like rattle can spray for clearing nozzle. Your Dekups may have the advantage if this is the case and something I need too look into. unfortunately all my gun adapters and back stock of liners/lids are 3M.

[Len]

Marler,

On your Dekups can you invert your gun 180 degrees and never miss a lick regardless of spray out length/time? On my 3M PPS system you have about 1-3 seconds of spray time when inverted before you hit dead air, almost like rattle can spray for clearing nozzle. Your Dekups may have the advantage if this is the case and something I need too look into. unfortunately all my gun adapters and back stock of liners/lids are 3M.

I only use DeKups and I normally turn my gun over when needed then pull the trigger until the air is out of the cup then continue spraying. After that I don't need to deal with air in the cup. I used 3M for a while but didn't like the way the adapter fastened to the cup.

Are you using 3M's original or their second type of adapter?