Spray gun air pressure query

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PostPosted: Wed Nov 24, 2021 12:40 pm
Eliminate any connection smaller than 1/2" inbetween compressor and Paint booth plumb regulator with 1/2" fittings use Hi flow quick disconnects only.

I run a Devilbis DAD500 triple air filter unit with desiccant drier awesome unit!
Devilbiss does offer the same desiccant drier alone at a much reduced price.

https://www.zoro.com/devilbiss-desiccan ... VcQAvD_BwE

https://www.jbtools.com/devilbiss-13052 ... asQAvD_BwE

Again change all fittings and pipe from Air compressor to paint booth to be no smaller than half inch.
I use 1 inch pipe myself but still smallest fitting in system is 1/2" Too Paint booth air regulator and 50 foot 3/8 air hose with Hi flow disconnects only on the gun. Air hose is plumbed to regulator with no disconnects so air hose cannot be take out of booth! dedicated to booth only! No contamination issues that way.
I also do not run a regulator at my compressor all Shop air sees what ever is in tank only have one regulator in system and that's in the paint booth.

Image



The Devilbiss Desiccant "Air Snake" is a good choice for inline air driers.
https://www.amazon.com/DeVilbiss-130502 ... B000UZPPKA
Has good flow numbers while providing a decent amount of protection for a limited amount of time, Do not expect it to last and their is not a good way to tell if its saturated!

When fighting water in system its best to build a water Trap after about 20 feet from compressor make or build a metal water cooler and water trap.
This guy is a bit too much for me and his design is a bit over kill with all the drains doesnt need to be this extravagant.
https://www.youtube.com/watch?v=DPX48WuaIhw

This one is better and guy down to earth My set up is similar to this. with my own twist I use expansion tanks to get a temp drop which works extremely well.
https://www.youtube.com/watch?v=RutBpkvSG_M

When you couple a well designed water Trap with a desiccant drier You don't have water issues and your Desiccant lasts for years. I have only ever had to dry my Desiccant once ever.
Dennis B.
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.



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PostPosted: Wed Nov 24, 2021 5:36 pm
Thanks mate....I now have 10 metres of 1/2" hose with 1/2" fittings and 7 metres of 3/8" hose in the booth (like you, it will be have a fixed connection in the booth). I eliminated all the quick connects in the system except on gun hose end so will see how that goes once the filters arrive.

I have that high flowing 1/2" SMC water seperator on order and I ordered a cheap 1/2" desicannt to see its effect on the air flow before I shell out any decent money.

My original design was like those videos and had the 3/8" hose snaking up and down with water traps at the bottom of each section but I had used those regulator / water traps as opposed to just a drain value and I had too much hose in the system.

I'll just try the basic setup above as I am a long ways off (years) doing any final base / clear so will test it out and beef it up along the way if necessary.

Do those T fittings that continue down to a water trap slow your air down much? Might be worth putting one of those in before the filters like you have done.



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PostPosted: Thu Nov 25, 2021 1:00 pm
From my compressor to my Air/Water cooler Trap all my hose connections are short as possible and all of it is 3/4" hose to 1 inch steel pipe. (No air restrictions!)
My water Trap consists of 80 feet of 1 inch pipe all laid horizontally for Temp drop To two large Air Tanks for air expansion for an additional Temp drop from expansion in the air tanks were water drops out and is collected in the tanks, Air is then plumbed throughout the shop in 1 inch pipe with Air quick disconnects where needed then onto my Paint booth where I have an air shut off to keep air from the filters and drier when not in use. And yes their is a Final last chance drain before my Filters and drier but I have never had any moisture collected their ever.

I am in Death Valley and you would be amazed by the amount of water my system collects in my water trap.

I depend on Devilbiss Air filters and Desiccant drier They are Professional level equipment and pose no air restrictions as I said before The Smallest diameter pipe in my system is 1/2" going to my Air Pressure regulator from the drier and a 3/8" air hose then the Devilbiss Hiflo quick disconnect to the guns.

Air hose use before your water trap should be avoided as Hose dose not dissipate heat like Pipe does steel or Copper.

A lot of people disagree with using steel pipe because of corrosion and possible rupture from rust and possible contamination of rust in air, But I run filters so I am not worried about it been using Pipe for years and never had any problems my self.

Your water trap needs to be 20 feet from your compressor in PIPE to get the Temp drop.
The Temp drop allows Moisture in the air to drop out where it can be trapped.

IF your reading your air pressure at the base of your gun as You should be and adjusting your air at the wall with Hi flow connections gun trigger pulled and setting your air pressure you should be good. if pressure creeps up higher with trigger not pulled I would suspect a Bad air pressure regulator.
It is not uncommon for Air pressure regulators to go bad even when new It is also not uncommon to have a Bad Pressure gauge on the gun These are small cheap gauges even the ones from Devillbiss are fairly cheap and their reading taken used only as a Guide to get you close don't believe them to be 100% accurate because they are not.
Unless you have had its calibration checked so you know exactly how far off it is.

We have Professional level Regulators and Gauges at work that we use for all kinds of things Nitrogen, Oxygen etc. and no two read exactly the same. and yet all are calibrated to be within a certain spec +- deal.
Dennis B.
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.



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PostPosted: Sun Jan 30, 2022 11:02 pm
Gents

I've attached below a quick snapshot of my current air line setup...works well although the desicannt beads are capturing moisture even though the preceding water trap captures nothing.

If I wanted to convert over to a copper piping setup to better get any condensation out of the line - any recommendations on how you would do it with my current setup.....should I just run copper in lieu of the 1/2" hose and call it a day?

https://youtu.be/1zVoihsyNY8

https://photos.app.goo.gl/PKg5DYwj2aG3H3KZA

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PostPosted: Mon Jan 31, 2022 10:44 am
There are about a zillion threads here covering drier setups. Do a search and be amazed at the variety.

As for your setup, the first thing I'd do is lose the LPG bottle. Just one connection, no drain and no safety valve is asking for trouble. You have a good sized tank on that compressor already.

Most people put the drier system on the outlet side of the compressor, between the tank and the tools. This always seemed a bit illogical to me since you'd just be feeding it with moisture rich air from the tank. So, I built a copper line cooling system that goes between the compressor pump and the tank. Water condenses before it gets to the tank and, for the few weeks I've had operating, not a drop of water in the tank.

Have a look here for some pictures. Seems to me a similar arrangement would work in your situation.

Lots of good advice in Dennis' posts but I tend to think that 25mm pipe and fittings is overkill unless you have a big shop with a couple of booths and a series of prep bays manned by 10 or more painters and beaters. 10mm hose and 15mm (nominal) copper tube works just fine for a lower use case.
Chris



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PostPosted: Mon Jan 31, 2022 3:56 pm
Thanks mate. I've seen all those drier setups. I should have been specific about asking whether the copper setups are only useful if done as an air drier setup like you have created in your link.

After seeing your oil less compressor, you got me regretting the big McMillan purchase a little given you sub 60 decibel outputs. I looked at oil less but was worried about longevity at the time....I may have to mock up some kind of sound deadening enclosure to knock off some decibels and make sure I don't overheat it in the process.

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PostPosted: Mon Jan 31, 2022 11:18 pm
No, copper tube would probably work if just done as a single line, albeit not as well since each vertical tube in mine condenses water that then doesn't go on to the next upright. Each elbow or T also works as a surface that the moisture hits and can condense on.Just need the overall length, in my case about 20m and the way I've done it keeps it compact which suits both what I have now and my future plans.

Nothing wrong with those big McMillans - they will last a very long time. Much longer than I need one to last given that I'm not painting every day like I was in the shop.
Chris



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PostPosted: Tue Feb 01, 2022 3:16 am
Thanks mate, I've got the copper piping setup on my build list but not for a while.

Guys, after your opinion on this exhaust filter setup and whether it would last one paint session of bc / cc. My usage will be to paint one Ford F truck and I'm happy to replace filters frequently if needed given the low usage so just the need the setup to last my biggest paint session day (bc/cc) without clogging up.

I've got a Dwyer vaneometer on order just to test how the booth flows with different levels of filters.

My original exhaust setup is about 1.5m of andrea pleated cardboard filter though a 24 inch industrial extraction fan and it flowed great. They are supposed to be around 95% effective and I have no doubt that would last easily given overspray that gets through will be vented.

I'm playing around with testing to see if I can scrub some VOC's with an activated carbon filter. I planned on keeping the Andrea filter, then have a 3d polycomb filter (99% effective per the marketing) then the activated carbon filter but only sized to fit the fan housing as per the pics below.

Do you reckon this would last one days painting or would the fan housing sized filters be too small?

https://photos.app.goo.gl/sGfTtTvX37JEGLwGA

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PostPosted: Tue Feb 01, 2022 3:30 am
I'd keep the cardboard filter and add the activated carbon just in front of the fan. Should have no problem with a single job.
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PostPosted: Tue Feb 01, 2022 3:40 am
Whats your thought behind removing the 3d polycomb filter?

I heard those carbon filters clog quickly, so thought the cardboard filter would catch a lot of overspray, then the 3d polycomb would hopefully catch most of the rest and keep the carbon filter clean to potentially scrub VOC's.
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