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Thread: Water Filtration Dust Collection?

  1. #1

    Water Filtration Dust Collection?

    I grew up in a household where the vacuum cleaner was a Rexair (now Rainbow) which removes the dust from the air using a wet filtration system. It was very effective at removing dust and it didn't clog up. Has anyone seen a small shop dust filtration system that works on this principle? I can see a downside, all the dust (sawdust and chips) would end up suspended in water. Could this be composted? Perhaps there are air volume considerations inherent in the technology in its simplest form? Perhaps knocking most of the dust out with a cyclone would make it more workable.

    John

  2. #2
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    Seems like a lot of air to move through the water so it would likely require a lot of water, would probably require a larger motor, and then, it would be very difficult to empty and clean.

  3. #3
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    Isn't that how a drywall sanding system works? Shop vac hooked up to 5 gal bucket filled with water.
    - Bob R.
    Collegeville PA (30 minutes west of Philly)

  4. #4
    Great idea, now you have your chance to invent a new shop air cleaner!

  5. #5
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    Quote Originally Posted by Bob Riefer View Post
    Isn't that how a drywall sanding system works? Shop vac hooked up to 5 gal bucket filled with water.
    We have a Rainbow vac and were told that it wouldn't work with drywall dust. Dunno why, and I haven't tried it, but that's what we were told.

    To the OP, you'd have one heck of a mess on your hands with that type of system. It's bad enough dumping a cannister of chips as it is; I can't imagine trying to handle a bucket of wet (heavy) chips... If you're talking about using a cyclone or seperator before the dust hits the water, maybe it would work.

    As far as composting the stuff, I suppose it would work well if you're not using plywood or MDF (glue & other chems).

  6. #6
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    I somewhat doubt that something like a Rainbow vac would work on the fine dust that woodworkers need to be concerned about. I hate to use the example, but think about the smoking water pipes that people use. If the smoke can get through the water, why not .5 to 5 micron dust?
    Trying to follow the example of the master...

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    If all the air passes through a wet filter, does that raise the humidity of the air? This might not be an issue with a house vacuum, which moves only a small fraction of the air in a house. But with a big DC system you might be significantly raising the humidity in your shop. That might be enough to make wood warp and machine surfaces rust.

  8. #8
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    If you use the water filter as the only filter, you get a bin of waterlogged chips and dust. That would certainly be a bear to dispose of. If you use the water filter with a cyclone in front of it, you're solving a non-problem. A good cyclone design extracts so much of the dust that the filter only rarely needs cleaning.

  9. #9
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    I've been digging into this same concept for a few weeks now. If you google "wet air scrubber" you'll get various hits on the application. The tech is mostly reserved for industry where vapour, and extremely small dust particle filtration is needed. The premise is to increase the size of the dust (we're not dealing with vapour), with water so it's more easily removed from the air stream. This is more involved then simply blowing dirty air through a bucket of water though.

    I envisioned a two stage system where a cyclone would remove the standard >98% of the fine dust, and then the "scrubber" would capture the remaining sub micron particles. Keep in mind that those using appropraitely designed cyclones report "tea spoons" of fine dust in their standard fiber based filters, after mulitple bins of cylcone separated material has been disposed of. If that's true I wouldn't expect much of a mess using water to collect that fine dust.

    Quote Originally Posted by Jamie Buxton View Post
    If all the air passes through a wet filter, does that raise the humidity of the air? This might not be an issue with a house vacuum, which moves only a small fraction of the air in a house. But with a big DC system you might be significantly raising the humidity in your shop. That might be enough to make wood warp and machine surfaces rust.
    ^^^^This is the problem that has my wheels turning. My whole reason for wanting sub-micron filtration is the fact that my "small" shop is in the basement of my home. Whatever my DC pulls in, must be returned into my shop, and obviously increasing the humidity isn't something any of us would want to do.

    My current line of thinking is the use of a second cyclone to spin the moisture out of the air, just like the first stage did with the larger chips/particles. Whether that has any merit or could really remove enough of the humidity...I don't know. However, I'm at the earily stages and I'm hoping for an epiphany at some point .

    At any rate... I don't think the idea is all that practical for the marketplace. Simply because doing it "right" would be costly, and complicated to say the least.

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    Quote Originally Posted by David Hostetler View Post
    I somewhat doubt that something like a Rainbow vac would work on the fine dust that woodworkers need to be concerned about. I hate to use the example, but think about the smoking water pipes that people use. If the smoke can get through the water, why not .5 to 5 micron dust?
    Treading on thin ice here...
    I think that has something to do with the oils in the smoke (same issue as the drywall dust I think). If you look at a used water pipe, they collect plenty of particulates (tar and whatever else is in the smoke). Er... at least... that's what I've seen in the movies

    It's an interesting experiment. I'll see if I can remember to clean out the HEPA Exhaust filter on our Rainbow and then go after a pile of fine dust (if I get enough time off of work to make dust in the next month ).

  11. #11
    I would think that water filtration of saw dust from a table saw would require a pretty deep reservoir of water so the soggy chips could sink other wise, I'm not sure the air would pull trough the water. As others have mentioned, dealing with soggy sawdust is going to be pretty messy and heavy.

    You might want to do research on the Rainbow cleaners as I understand it they had problems with mold growth and weren't all that effective in capturing fine dust.
    Lee Schierer - McKean, PA

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    For the smaller sawdust particles suspended in air it would be ideal. If you could find a wet air scrubber.

    But for the shop as a whole it would be a disaster. Raising the air humidity would rust out machinery and cause stored wood to swell.

  13. #13
    I'm not at all an expert in this, but I bet the reason a rainbow wouldn't work for drywall dust is that you're pulling bubbles through the water and the dust is floating in the air inside the bubble and makes it through the water. You'd have to blend the air/water together to minimize the bubble size to trap that fine dust.

    Totally a guess on my part.

  14. #14
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    Oil-bath air cleaners have been used for years on compressor engines, vintage autos, tractors, etc. The principle being that, the air is forced to make a 180 degree turn, but the inertia of the particulate matter causes it to be driven into the oil bath. I saw a Rainbow years ago and, unlike the oil-bath filters, I remember the water swirling around the canister. Maybe the air flow follows a different path than the oil-bath type filters. I don't remember any bubbles, and I don't believe the air went through the water...just past the surface.

    It seems logical (to me anyway) that a trash can, cyclone, or some other primary filter with a large water or oil bath as a secondary filter would produce good results. As others have said, water would increase the humidity.
    Last edited by Todd Willhoit; 12-18-2010 at 1:16 AM. Reason: Add info.

  15. #15
    It's been about 12 years since I touched a Rainbow, but I believe it had a dirt intake which came in below the surface of the water and the motor above the surface. Probably some guides which swirled the flow. I remember thinking I could improvise something similar with a shop vac and an elbow which would send the intake below the waterline.

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