Spray gun air pressure query

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PostPosted: Sat Nov 20, 2021 4:30 pm
Appreciate the reply guys..

I did some testing and isolated each component and essentially one water trap, the amaxi filtration and the 20m retractable hose elements are causing the drop so I need to reposition my compressor and simplify my setup (frustrating that I wasted $300 on the amaxi unit). The devilbiss gun regulator I hooked up seems to have larger ports than the cheapie I had on the AZ3 initially.

NFT5, what air filtration brand / setup do you have / can recommend in Australia?

I was thinking I probably just need to bite the bullet and get a 3/4" or 1/2" 3 stage system with barbed connectors (no quick connects) as that shouldn't impact flow on a 3/8" hose setup but they are expensive. The cheaper 3/8" 3 stage systems seem to max out at 300l/m.

The joys of single phase power...I bought the second biggest McMillan single phase on the market at the time as I still needed to run an industrial extraction fan etc on a 32 amp circuit. Luckily the GTI pro lite is only a 250l/m odd with the smaller tip....I plan on priming a panel / section at a time as I do the body work so the AZ3 should be okay - in the past I just stopped for a minute with a smaller compressor plus I plumbed in an additional air tank.

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PostPosted: Sat Nov 20, 2021 6:32 pm
LittleJerry wrote:NFT5, what air filtration brand / setup do you have / can recommend in Australia?


This is what I had in the shop:

20200611_160153.jpg

The alloy tank works to cool the air and condense moisture. Works a treat.

Picture 006.jpg

For years I've just used to little wall filter/regulator on the left, but recently changed over to the big one on the right. In terms of your problem, no real difference. Also have a dual unit that I bought from Gasweld. It worked pretty well too.

Generally I run wall pressure at about 65psi and then take that down to 28-30 at the gun. Using the gun regulator is good in terms of getting consistent pressure but you do get that initial burst that then drops back to what you've set. I'd prefer to go back to not using regulators at the gun and controlling just from the wall and will do that in the new booth, once it's built.

I have a couple of AZ3s. Good guns but mine are not HVLP, so aren't air hogs like yours. Happily use about 9cfm, even the 1.8mm.

Only use good quality 10mm hose. That stuff in the pics with the yellow stripe has lasted for 10 years plus and still as good as the day I put it in. Don't know the brand but I do see it around from time to time. From the wall to the gun I use a CIG no-kink hose that I cut down to about 10m. It also lasts forever and is much nicer to use. Don't buy the shiny **** from Supercheap or Bunnings.

This is the new compressor. 475 l/m.

2020-11-23 19.04.52.jpg


It does make some water, so I'm building a copper tube array to deal with that and adding a couple of 50l tanks from old compressors that I picked up cheap because they don't work.
Chris



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PostPosted: Sat Nov 20, 2021 10:19 pm
Thanks for the info mate. It's very relevant as you have a proper setup but are still running affordable gear for DIY guys like me.

How much hose are you running from your compressor to your booth entry? I was thinking I could run 1/2" hose until I get to the booth (and replace all my filters with one 3 stage filter and no quick connects)...I have the blue / yellow stripe 3/8" hose currently from total tools. I was thinking then I could cut down the 20m retractable to say 8m-10m inside the booth.

Is there a product name for that alloy tank setup? Or is it just a universal alloy tank with air fittings that force the air up and to condensate on the tank walls?

What size ports does your new 3 stage filter setup have? I could only find a 3/8" 2 stage on the gasweld site...not sure that would flow well enough and not bottleneck the system.

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PostPosted: Sun Nov 21, 2021 2:41 am
The compressor sat just outside the door, so really just the hose you can see in the photo, plus a bit for the drop on the other side. There was another wall fitting/regulator further down the booth but I never used it unless I needed air outside the main doors, for blowing off the floor usually. In the new booth I'm using 12mm copper tube. Not really that expensive and it's permanent. Only flexible hose will then be from the wall fittings.

The alloy tank was something I bought for a set of air horns for the Triton I had at the time. Never got around to fitting them, sold the Triton and bought a Pajero and the tank wouldn't fit. Get them on Ebay.

Standard Nitto fittings on the new setup. Never measured the internal size but looks like high flow. 3/8" is near enough to 10mm and that's the size. Except for the big ones, most are only 1/4" and, although it's ok if just one fitting, 1/4" does create a bit too much restriction.
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PostPosted: Sun Nov 21, 2021 3:35 am
I must be missing something..all the 3/8" and 1/2" 3 stage setups like the one you seem to have that I am seeing say a max of 300l/m and i am guessing that would be at some high psi...I would have presumed that would have given any hvlp / gravity fed spray gun issues (they all seem around the 250+ l/m) - you are only setting your tank pressure to 65psi but your saying its flowing fine for you - can you tell me the brand of your unit?.

How did you plumb from outside your booth to inside for the hose? You just feed the hose through and silicone it up or is there wall mount connections? Does your hose come in from up high or at a lower height?

It's annoying as I am happy to spend $300 on a 3 stage if I know it's going to flow good and keep any moisture out as I already wasted money on that amaxi unit...but there is a price jump to the 3/4"+ units which advertise better flow rates that it's almost worth just swapping to a lesser air hog gun.



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PostPosted: Sun Nov 21, 2021 5:45 am
On a side note - you mentioned you had like 22 guns...do you have the Devilbiss FLG 5? If so, how do you rate it as a primer gun? Gets the air usage down a little to 9's CFM if I decide the AZ3 is too much for my setup.

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PostPosted: Sun Nov 21, 2021 10:30 am
Just remember, just because a gun takes less CFM that doesn't mean
you'll use a lot less air, those lower CFM guns takes more passes to cover a panel.
My "air hog" gun will cover a panel in half the passes as my less lower CFM gun
so my compressor doesn't seem to really run any longer, in fact, it seems to run less.
JC.

(It's not custom painting-it's custom sanding)



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PostPosted: Sun Nov 21, 2021 3:20 pm
It was more about potentially being able to operate under the max flow rate of some of these more affordable 3 stage filter systems - NPT5 seems to operate perfectly fine running a similar unit.

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PostPosted: Sun Nov 21, 2021 4:33 pm
LittleJerry wrote:do you have the Devilbiss FLG 5? If so, how do you rate it as a primer gun?


Yes, but it's a 1.4mm. Was. Sold it with the shop. I kept the Pro Lites, Tekna and AZ3s, along with some midi/mini guns.

Good gun, exceptional for the price. Still not in the same class as a Pro Lite, especially in terms of longevity, but ideal for a hobby painter with a nice big, very even fan and great atomisation.
Chris



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PostPosted: Sun Nov 21, 2021 9:38 pm
Turns out I had 35 metres of 3/8" hose and 7 sets of quick connects running through 3 filters...I wonder why I had flow issues lol....I had no moisture in my setup but also no volume.

I cannot relocate my compressor so I'm going to upsize to 1/2" hose outside the booth with 1 non quick connect fitting to one filtration unit and another non quick connect fitting to 7 metres of 3/8" hose in the booth.

Just got to determine if I need a desiccant filter as I think the beads hurt the flow more than any port size etc.

Turns out that Amaxi toilet roll type filter will flow enough for the HVLP, but it creates a bit of turbulence stopping the pressure dropping rapidly from about 40psi to 30psi which would give inconsistent spray finish each time the trigger is pulled so I will swap that over as a filter for my air tool line.

Talking to a local shop - they recommended this https://airtoolswa.com.au/water-separat ... g350c-04d/ which would be a nice simple option and said to throw the Amaxi unit in the bin lol.

Appreciate all the input guys.
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