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Thread: Plumbing question: What kind of check valve should I use for an air/water mixture?

  1. #1
    Let's positive thinking! seedjar's Avatar
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    Plumbing question: What kind of check valve should I use for an air/water mixture?

    So, I don't know much about plumbing, but I know that many plumbing parts are specialized with a certain type of fluid in mind in their design. I'm wondering if this is true of check valves, and if so what kind of valve I should use for a line where water will run one way and air will be exerting pressure against the flow. I'm building a box for dispensing CO2 by evaporating dry ice. There will be an adjustable valve for the output and an air line input to force gas out. I plan to put a check valve and a shutoff valve on the air input so that I can seal up the box when not in use.
    I'd also like to add something to raise the heat inside the box when I want a higher CO2 concentration. I'm not certain about what kind of heating element would be advised, and I prefer mechanical tools over electric anyways, so my idea was to have an optional water input. Like the air input, it would have a shutoff valve as well as a check valve to prevent backflow. But do I need to use a special type of check valve if I want water to flow through it but expect the stuff that tries to flow the other way will be air?
    My gut tells me that no, a valve built for a dense, hard-to-compress fluid like water should have no problem resisting the physical stresses of air. But I've been wrong about this kind of thing before. Also, since there will be low temperatures, what type of material will resist cracking/freezing up? Is there a certain check valve design that's better suited to this application?
    Thanks,
    ~Joe
    o//~ Livin' like a bug ain't easy / My old clothes don't seem to fit me /
    I got little tiny bug feet / I don't really know what bugs eat /
    Don't want no one steppin' on me / Now I'm sympathizin' with fleas /
    Livin' like a bug ain't easy / Livin' like a bug ain't easy... o//~

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    Av8tor1's Avatar
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    I use to maintain a system that provided an air charge to the sprinkler system in a large area that was -40f.

    We used air under pressure to keep water from entering the sprinkler lines. Once a sprnkler head was set off, the air pressure would drop and the water was then allowed to flow.

    We also used reverse flow protection.

    one thing you dont want is water filled sprinkler lines at -40f, when it happened you had 30 mins to get it out or things got exciting.

    Buttttttttttttttt back to your project,

    One concern would be long term corrosive attack from the CO2 or moisture in the air (industrial grade pneumatics components should suffice)

    What flow rates do you expect, what pressure differentials?

    I have bunches of check valves and flow controls mate, just PM me your specs and Ill see if i dont have something laying around you can use.

    One thing, have you considered compressed CO2 as opposed to dry ice?... it will be much cheaper to operate mate

    You can get tanks on ebay on the cheap (paintball gun tanks are appox 10-20USD) or buy a planted aquarium co2 system (nice)

    PM me with your pressure and flow specs,
    Av

  3. #3
    Not Growing Up! GrowinOld's Avatar
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    Well....!

    I don't know what you are looking for,
    as I don't have experience with that,
    however while looking around on ebay
    I saw this and thought of your request.

    http://cgi.ebay.com/CO2-Regulator-Gr...item3a54e6ef04

    I doubt it will help, but do know I am thinking of you!
    No, not that way
    and not on purpose!
    Ewww!

    Well, good luck in your venture.

    Oh, speaking of CO2, do people really notice a change in plant growth
    by pumping CO2 into their grow chamber? I figured that the air had
    more than enough CO2 for normal growth. (Breathe heavy in on your plants
    a few times a day, and that should do it, right?)
    I do know that people have talked about it helping plant growth in aquariums,
    however that is gasses dissolved in water, which can vary depending on water
    conditions.... but I didn't think it had as much effect on terrestrial plants.

    Although I have seen CO2 devices being sold for "herb" growers, but figured it
    was overkill, and more hype than useful, sold to people that didn't know how to
    grow anything to begin with.

    If anyone has any experience with this (the CO2 growth effect), I would love to hear!
    Paul
    Experience is the best teacher. At least it used to be.
    But then, common sense isn't so common anymore, is it.


    http://www.terraforums.com/forums/sh...d.php?t=113866

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    Av8tor1's Avatar
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    The benefits of CO2 would depend on if its the limiting factor.

    If one of the other variables are insufficent, then CO2 will not be much help. But, if everything else is spot on the CO2 use can provide significant results.

    All depends on if it is the weak link in the chain or not. Like everything else, many variables are at play

    Av

  5. #5
    Let's positive thinking! seedjar's Avatar
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    I'm mostly building this as a pest controller, not for regular duty. For CO2 enrichment I'm going to build a yeast burper or something - I've seen a number of types of plans for them. This one I want to use to fill containers like garbage bags or the like. Still trying to figure out a good way to skim the input air off the top of the CO2 as it settles, but I think if I use large enough containers it shouldn't be an issue. As for the specs, I plan to use a small aquarium air pump as the air source, so while I'm not sure of the exact numbers I doubt it will be over 50 PSI and 100 GPH. Water would be input at more or less neutral pressure - I was thinking gravity-fed. The flow on the water won't be very strong at all; since the water won't be evaporating much at the temperature of dry ice, I had intended to use a trickle or intermittent drip of hot water.
    It occurs to me now - are there any readily available household items that would work to provide heat in place of water? Maybe a heating pad or something? Really, I just don't trust most household electronics to last. Add below freezing temperatures to that and it isn't promising.
    Thanks for the tips - it hadn't even occurred to me that pure CO2 is corrosive to some materials. I guess I think of it as one of those things that's only really hazardous to squishy things like animals.
    ~Joe
    o//~ Livin' like a bug ain't easy / My old clothes don't seem to fit me /
    I got little tiny bug feet / I don't really know what bugs eat /
    Don't want no one steppin' on me / Now I'm sympathizin' with fleas /
    Livin' like a bug ain't easy / Livin' like a bug ain't easy... o//~

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    Av8tor1's Avatar
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    ahhh, well then Joe

    I would probably just use inexpensive aquarium "duckbill" checkvalves. Anything much more intense will be either expensive or require a greater pressure drop to open.

    Im not sure where the 50psi comes in at now though.... that would definitely be too much for the aqaurium valves.... but if ya need something that can deal with that just hollar. (I would expect someting more along the lines of "inches of water column" pressure values

    What about the lava lamp model, put an incandescent light bulb under the container that holds the dry ice?

    Regardless, Im sure I have industrial grade valves in several flavors mate

    My first impression would be to install a bulkhead fitting in the top of a wide mouth mason jar, put the dry ice in it and set it on the heat source with the hose running into the bag.
    The Co2 expansion rate will be in the hundreds or thousands as it turns from a solid to a gas, so no external pressure source will be needed as long as there is little resistance to the flow of CO2 (I would think)

    caveat, if for some reason the output was to be completely blocked, you will have a viiolent explosion, something will give... you have lots of potential energy wanting to go kinetic :P

    A safer alternative might be a big storage tote, poke a small hole in it somewhere...put in the plant/s in it and a small pan of dry ice... insert a duckbill checkvalve in some aquarium tubing and insert the tubing into the small hole. (or even just a cotton ball in the hole)

    as pressure builds higher than atmospheric the excess will vent out the duckbill/cottonball...

    just brainstorming

    Av

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    billylh's Avatar
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    i used to work for a distributor of these valves and fittings, quality stuff, down to 1/8 " thread sized

    http://www.swagelok.com/search/find_...0000272/type-1

    and for the heating, you could try a reptile heating pad?

  8. #8
    Let's positive thinking! seedjar's Avatar
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    Quote Originally Posted by Av8tor1 View Post
    The Co2 expansion rate will be in the hundreds or thousands as it turns from a solid to a gas, so no external pressure source will be needed as long as there is little resistance to the flow of CO2 (I would think)
    D'oh! I can't believe I overlooked that - I guess the "ice" in the name makes me think of way water expands as a solid. I feel really stupid now. In my defense, I've been losing a lot of sleep this past week.
    I like the lightbulb idea too - they're cheap, replaceable and I can put them on a dimmer. I still think I might want the air in, though, so I can get a variable mixture if I find other uses for this box. And maybe a coolant conduit to add a chiller later? In the event that sublimation at the ambient temperature is too rapid.
    I think I'll use a chest cooler with a custom lid, or perhaps a modified lid or an insert that fits between the lid and body. How close do you think I could get the lightbulb to the ice in practice? I'd have the two physically separated somehow, maybe with a thin layer of plexiglass or a jar or something. Still though, this is no Easy Bake Oven. Would canning glass stand up to dry ice temperatures, or will I need lab glassware?
    Would it really be that much cheaper to go with tanks and refills? I looked at a few prices for refills at various brewery stores and such and it looks like about $1 for one pound, which is like 10-15 cubic feet when expanded at room temperature if my rounding wasn't too sloppy. I don't have any CO2 enrichment experiments planned yet, but my guess would be that a five pound tank would only last a week or two if I were making substantial changes to the enclosure's I'd be building. I've gotten dry ice before for free from Baskin Robbins just by asking nice, but to look at the prices it seems like I'd be paying about twice as much by mass to buy solid over liquid. It seems like refilling tanks would be a pain in the butt, but there are a few Airgas distributors around here so maybe I could order them... Dry ice is only about twice as dense as liquid CO2, which surprised me when I looked it up. I was thinking there might be a bigger difference and that I could save on storage space and effort transporting it.
    I suppose there's a reason that people use it in tanks and not as a solid. (Sigh.) My way sounded so much more fun, though.
    Quote Originally Posted by billylh View Post
    and for the heating, you could try a reptile heating pad?
    That was one of my initial thoughts, but heat pads die like crazy on me. Especially greenhouse/reptile ones. Maybe it's because I was kind of rough on them in the past, but I just don't trust them. I think incandescent light bulbs will be the cheapest, most worry-free solution. That is, until incandescent bulbs are relegated to being quirky retro throwback decor items.
    ~Joe
    o//~ Livin' like a bug ain't easy / My old clothes don't seem to fit me /
    I got little tiny bug feet / I don't really know what bugs eat /
    Don't want no one steppin' on me / Now I'm sympathizin' with fleas /
    Livin' like a bug ain't easy / Livin' like a bug ain't easy... o//~

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