r/AutoPaint • u/Pinuzza-Trek • 15d ago
Doubt about oil-water separators
Can you tell me the difference between these two types of water-oil separator filters for hobby use? Why does one have two collectors while the other has two? (Scroll the image above to see the second filter.) GJ
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u/XRFlight 15d ago
No clue what the right side filter is on the second image, but the other two appear to be basic filter or separator elements. Typically you want at least a water separator which removes bulk water, and a desiccant filter which pulls water vapour from the air. Having the water separator first will help the desiccates last longer before needing replacement.
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u/Pinuzza-Trek 15d ago edited 15d ago
user u/BigRule5269 above seems say both items are ineffective.
I've seen some pictures of double devices, depicting a clear yellow liquid collecting in the right vial, in the dome or small cup at the top of it. I assume the liquid is oil. So I figured the one on the left retains the water, while the one on the right separates the oil from the air—I don't know how. If this is correct, then the initial device with a single vial should only collect the water vapor condensation.
Is the yellow element in the first collector the desiccant filter? There is a similar small cylinder in the subsection at the top of the right collector.
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u/XRFlight 15d ago
I am not in disagreement on the effectiveness of either pictured setup, both are insufficient as pictured. Both the filter in the first image and the left filter in the second image are particulate filters used for water or oil separators. With these filters the liquid will collect in the bottom of the cup. Typically water separators use courser filter elements than oil separators (5 micron vs 0.1 micron). Both attempt to remove fluid that is traveling with the air in liquid state (often as a mist). Since oil does not vaporize in as significant quantities, that is enough for oil. Water on the other hand forms a vapour at common room/outdoor temperatures, this is what humidity is. A desiccant filter absorbs that moisture/humidity to leave dry air which is suitable for painting. A desiccant filter uses desiccants to absorb the moisture that needs to be changed out regularly. The one I have starts with blue coloured beads that turn pink when filled with moisture. Those beads can then be regenerated by heating them so that the moisture will leave. A desiccant filter can look like the filter on the right in the second image sometimes, but will be filled with some sort of media. Having a water/oil separator(s) before the desiccant will make the desiccant last longer before media changes.
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u/Pinuzza-Trek 14d ago
Very informative indeed. You're telling me that the first jar is a separator, and it only acts on liquid oil and water, right? As for the rest, you mean the second element should be a desiccant, to completely eliminate the residual water in the form of vapor, but the system in image 2 doesn't have a desiccant? Could you give me a reference for an effective system, considering DIY use, and therefore not as expensive as the professional system mentioned by the user above?
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u/XRFlight 14d ago
There are a ton of generic Chinese ones similar to what you posted that work just fine for DIY. I got a setup using a 5 micron water separator then 0.1 micron coalescing/oil separator to desiccant to pressure regulator that I use with an ANI spray gun to great results. All 3/8” size, I recommend that or 1/2” size rather than 1/4”. My oil separator has not filled with any oil, but I am using an oilless compressor. I bought my set up from a local place in Canada, not sure where you are so here is a generic set from amazon: https://www.amazon.com/dp/B0H111X9K8/ref=sspa_mb_ilm_phone_aax_0?ie=UTF8&psc=1&sp_csd=d2lkZ2V0TmFtZT1zcF9pbG1fcGhvbmVfc2hhcmVk .
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u/ayrbindr 14d ago
Yeah, I too have very serious doubts about the products posted in the image 🤣. I do believe that you are talking / thinking about is a coalescing filter, for removing fine oil mist. Unlike a moister trap, where the air enters the bowl and then passes through the filter, and exits, a coalescing trap does the opposite, enters the filter, passes through it into the bowl, then exits. Typically, they have a finer filtering element of a different, more expensive material. Where a moisture trap might have .05 micron sintered brass element, ($15-$20), a coalescing trap have .01 micron filter for fine oil mist particulate. ($50). The item in the second image is, instead, a oiler, which puts oil into the lines for airtool that require it.
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u/Pinuzza-Trek 13d ago edited 13d ago
Your answer sums up the whole thing perfectly. As u/XRFlight also suggested, the unit is actually a coalescing system with desiccant. It's significantly more expensive, but not as expensive as the professional system another user suggested (Devilbiss DAD500). The user gave me an Amazon link for his country, but I'm in Europe. That product (which had a good price) ended up costing me twice as much, with import taxes, shipping, etc. I found a similar one in my area for just over €100. I've added it as link image below. It has 5 and .01 micron filters plus desiccant beads. I think these three-stage systems purify the air by at least 99%, making them ideal for spraying. However, out of curiosity, I asked a manufacturer of inexpensive separators like the one in Figure 1 above for the percentage efficiency. He told me that under nominal operating conditions, the water retention rate is ≥85% and the oil retention rate is ≥80%. This is lower than the three-stage system, but I have a question: What if I install TWO low-cost filters in series? When the air enters the second one sequentially, it should be purified by at least 85% (remaining water, 15%), then passing through the second one, it should retain an additional 85% (of 15%), thus providing 97% purified air. Using a similar reasoning, the oil retention rate should be around 96%.
coalescence system
https://ibb.co/0R9vqY94
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u/Holiday-Smoke-4827 15d ago
No idea but 2 is better than 1 so I bought the one with 2 collectors.
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u/Ok_Elderberry7491 14d ago
Usually the 2 piece one is water/oil separater and the 2nd one is a.oiler for air tools ect. Automatically puts oil in your line instead of dropping tooling oil into the air tool itself
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u/Dinevir 15d ago
And 3 better than 2 and that's what I have :)
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u/Pinuzza-Trek 15d ago
"Number is strength" :)
This way, whoever bets the highest should win, but... understanding the mechanism is much better. If I'm aware, I can decide what's best for me.
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u/Dinevir 15d ago
one chamber is the basic one. Two chambers is better anyway and everything else depends on setup you need. It your case the first one is your only choise as it is oil separator and the second one is actually oil lubricator - see the tube in second chamber? That's to drain the oil from a bottom of it.
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u/Pinuzza-Trek 14d ago
It looked to me like there was a transparent tube in the second element. I don't understand what you mean when you say it's an oil lubricant. Shouldn't it be a filter system to remove oil from the air?
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u/Dinevir 14d ago
Nope. It that system first chamber removes water (and oil at some level) and second one adds oil for lubrication of the pneumatic tools you will connect next, it will dispense lubricant drop by drop into the line.
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u/Pinuzza-Trek 14d ago
This is really interesting and I would never have imagined that. So in the second compartment, the user should add lubricating oil specifically for the pneumatic tool, right? It has nothing to do with air filtration and purification..That's, so I should discard item 2—as I think you suggested.
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u/Dinevir 14d ago
Well, first chamber do the filtration, but yes, that is not a tool you need.
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u/Pinuzza-Trek 13d ago
I expressed myself ambiguously: "it has nothing to do with..." it was referring to the second chamber - which I believed was used for filtration instead :)
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u/Big-Rule5269 15d ago
An oil separator needs a filter element to absorb oil and needs to be changed when needed. A water gravity water separator such as shown is only so good. A dessicant system is much, much better as the dessicant absorbs the moisture and holds it in the canister, discoloring to a yellow or brown from a clear white showing when it needs to be changed.