Coalescer vs. Condenser vs. Dissipator... etc.

[SurfLung]

I'd appreciate if someone would explain something: My understanding is that air purification has two phases. First is the condensation and drain off of moisture. Second is to filter the tiny remains of humidity and contaminants. The first part... the condensation and drain system is mechanical and referred to by many names. I've seen amazing differences in these systems.

The RIX has two moisture towers. One after the first stage and one after the 3rd stage. On the inside, they have ducting that spins the incoming air to help moisture settle out.

Max Air 35 has one moisture tower after the 4th stage and uses a lateral pointing nozzle to get the air spinning and settle moisture out.

I have an old Olmeva 6000 filter array that has a moisture tower after the 4th stage and it has an inverted dip tube with tiny holes to help the moisture settle out of the incoming air.

And finally, I have seen pictures of what looks like a solid substance but it is porous and incoming air condensces through that?

I know all of these are doing a same thing... Condensing moisture. I'd like to know if one is better than the other and if the various names mean the same thing.

 

[tbone1004]

Water Separator-bulk liquid removal, aka condenser. This is what is on the Rixes. They typically have a mesh element in them for the liquid to stick to and condense out, but can also be diverted around like a vortex. They are cleanable and only drop out heavy bulk liquid. The higher the pressure, the lower the dewpoint, the more effective they are, same with the colder they run. They are very effective and knocking stuff out, and anything that condenses in the liquid will fall out. If you're going to spend money, this is where to do it IMO because the more you can get out here, the better everything else is going to work, and they ALWAYS go first in the system. Coalescing efficiency in this is around 99% depending on the specific unit and is good to maybe 100um for things that get caught in the liquid. Almost no pressure drop as well which is good. These do not typically knock out oil. Some will come out, but not much because there isn't anything for it to stick to. This is not a

Next step is a coalescing filter. If you have a dedicated coalescing filter, they will typically have a special fiberglass filter element inside of them and have a coalescing efficiency from 95-99.99% depending on the element, and can knock oil down to 0.9 or all the way down to 0.003ppm with particulate filtration down to 0.01um. The tighter the glass the more filtration you'll have, but they'll also clog faster, so pros and cons. Not really needed on a Rix, but if you get a dedicated coalescing tower on an oiled compressor, your main filter stacks will last forever. This is built into most filter cartridges, but isn't as effective as a dedicated tower.

Next step is an adsorbing filter. Adsorbers knock out oil vapor/hydrocarbons and is basically the activated carbon portion of a filter cartridge. Not needed on a Rix, but obviously is on any oiled pump.

The key with all of these is to size them appropriately so they are effective. The more effective the water separator is, the less the coalescing filter has to do. The less it has to do, the longer it lasts. Same with the adsorber. All of these are removing particulates and liquid and as you get farther up the road, they are filtering smaller and smaller. The bold bits are there to emphasize what they're doing and how the water separator is different. They are all coalescing in that small bits are collecting together to form big bits, but the water separator is not "filtering" anything. All of the particulate that comes out is because it was stuck to the water that was condensing out and fell out of the gas. In the coalescing filters and adsorbers, they're actually mechanically filtering the gas to help with coalescing.

That make sense?

 

[SurfLung]

Thanks T-bone that explains a lot but also raises a few new questions and a comment or two.

1. Something to "Stick" to. I am surprised to hear that those screens in the RIX condensers are not just filters for particulates. I've had those condensers apart and they really are a fascinating design. Since RIX SA3 and SA6 don't come with filters, I thought that was what the screens were for. And it makes total sense that they're something to stick to because RIX don't have any oil to condense and clog them up.

2. But on the subject of "something to stick to" I tried using a stainless "Chore-Boy" dish scrubber to replace the broken dissipator screen in my 1980's MCH6. It seemed to work to some degree but I could see it getting all clogged up with oil and moisture and not really letting the condensate run freely to the bottom where it could be drained. It was regurgitating the condensate around and around in the condenser tube instead of letting it drain out. (I think the original screen system might have blown/broke off from pressure when it got clogged.)

3. So then, I looked at the condenser tube on my Olmeva 6000 filter array and it has a verticle dip tube coming up from the bottom with a bunch of tiny holes... So that incoming air enters the condensation tube near the middle of the tube. I think this system creates condensation by a pressure reduction as the air leaves the tube? Anyway I can see the necessity of doing it this way on an oil lubricated compressor. I was able to make up something similar for my old MCH6 and it seems to get alot of the moisture and oil into drainable condition and improved the life of my filters by a lot... Without clogging up.

4. Question: When you speak of a Coalescing Filter, are you talking about the the 3-part filter cartridges I get from Lawrence Factor? ie. Are you saying the 13X Sieve is a "Coalescing" filter? I guess I don't understand the difference between coalescing and condensing. I understand "adsorbing" and that's what I thought the 13X sieve is.

5. For example, I've seen some things that look like they're a porous rock material that the incoming air is forced thru in the condenser tube. I thought those were coalescers. Am I right? If not what ARE those things?

 

[tbone1004]

1. there shouldn't be much in terms of particulate, but the goal is for the water to condense on the surface *think on outside of a cold glass*, and trap the particles in the moisture. I'll have to pull the condensate filter apart in mine to look since I don't use the stock ones but still have them and see how tight it is. Do you have a picture of it readily accessible, and the other stuff you've been using out of curiosity?

2. Dish scrubber material will be too thick and that is where it shouldn't be the "first" place that you pull water out. Having a water separator with open pores to drop the majority of the moisture out will allow the filters to do less "work" and clog up much less.

3. it shouldn't be from pressure reduction, likely just turbulence.

4. The 13x is an adsorber which should go after a coalescing filter. Coalescing is essentially the same as condensing in that it is trapped against a physical barrier and when the drops get big enough, they SHOULD fall off and be able to be blown out. Adsorbing is completely different in that it "sucks up" the contaminant and while some of them can release *think zeolites in O2 or N2 generators when the pressure is released, or when baked out, etc*, but once it sticks to the barrier, it is meant to stay there. Coalescing is a type of mechanical filtration where adsorbing is more chemical filtration *with obviously a mechanical component*.

5. probably coalescing filters, yes.

 

[SurfLung]

Here Are the RIX Seperators...

And Here's an Article on my "disipater" for the 1980 Aerotecnica MCH6
A New Moisture Dissipator for my Aero...
- I removed the make-shift vortex generator (chore-boy) from the Moisture separator tower and found it was heavily coated with gunky condensate. So I decided to take the Moisture separator tower apart and see what could be done. Fortunately, I have a nearly identical Olmeva separator tower on the filter array for my RIX compressor. So I took the bottom off that one apart to compare. Below you see the broken Aerotecnica dissipator on the right.

- The original dissipator was a micro screen with the air inlet below it. The design allowed for a chamber below the screen and condensate tends to accumulate in that chamber. I think the gunky oil and water condensate clogged the screen so eventually it blew out of its mounting, breaking the mounting in the process. So now, the gunky condensate pools in the chamber above the inlet and just keeps shooting up and down and pooling without ever completely draining the condensate.

- In contrast, the Olmeva dissipator vents the incoming air through small holes in a verticle tube... The holes are located above the condensate drain pool so they're not blowing air through it AND the condensate can settled and be drained more completely.

- I replaced the broken microscreen dissipator with a home made dissipator along similar lines to the Olmeva dissipator. I used a concrete floor anchor just like the one Rich (50,001 Questions) came up with for replacing a dip tube on a tank valve. You can see how the slots will dissipate the incoming air above the condensate drain pool. This allows the condensate to pool unmolested at the bottom, and drain completely when the drain is opened.

- I've used this now for a couple of tank fills at home and three fills at our most recent dive trip to Fortune Pond. It seems to be working VERY well.