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CO2 Regulator for transfers

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  • #31
    O2, baby

    hey Hutch. Good to hear from you. Did you get home safe from Ommegang? Dude, what a great time! Also, you going to GABF? We are looking for a 4th for our Long's peak trip if your interested.

    O2....I'd purge from the bottom for at least 10mins for your tanks. Try the "sniff test". You should do it a little longer then just topping off. Doesn't cost much (time or gas) and your beer will thank you. Don't forget to purge your hoses and filter too!

    the answer to the question "is your beer oxidized" is; yeah sure, you betcha. Unless you've measured it and determined your airs are low I'd bet a sawbuck they're too high. Hutch's beers taste great and sell fast....so the level of o2 may not be contributing to long term instability ('cause the beer is gone) but that doesn't mean they're not oxidized. the question should be, 'how important is it that your beers are oxidized'

    for pub brewers this could be less of a consideration.... but maybe not. Just something to think about.
    Larry Horwitz

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    • #32
      Hello all,

      Just a thought about gas dynamics relating to Crassbrauer's comment on allowing time for the gases to separate. Correct me, but gas law dictates that a mix of different gasses will come to an equilibrium state. Meaning all gas molecules and concentrations will be equal at all points. More or less. So two gasses left overnight will not separate as liquids will, but rather mix together. Perhaps I am wrong on this? Chem class was oh so very long ago. Or I misunderstood the post? But all those cylinders of blended N2 / CO2 never seemed to first over carbonate then flatten the beer, so...

      I would think the best procedure would be a relatively quick purge / vent procedure that would not allow the gasses to combine.

      But again, no O2 meter. So no real data.

      Cheers,
      Ron
      Jolly Pumpkin Artisan Ales

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      • #33
        I'm no physicist, but I do know why CO2 settles out:

        Density of CO2: 1.98 kg/m³
        Density of O2: 1.429 kg/m³

        The unfortunate experiment I mentioned above, conducted seasonally by the Austrian farmer/vintners, along with the numerous other industrial accidents involving CO2 in low-lying areas or in tanks verifies this. Cold air and warm air also fall and rise respectively.

        I believe what you're referring to (my memory of this is also a bit rusty) is that the same number of molecules will be present in a given volume anywhere within the tank, given that the temperature is the same all over. More clearly stated: With all ideal gases at the same pressure, the same temperature and the same volume, the same number of molecules are present. (This is known as Avogadro's law, I think.)
        Last edited by crassbrauer; 08-10-2006, 03:25 PM.

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        • #34
          Larry makes a couple good points. Our gas supplier agrees the 'CO2 settling model' is inaccurate in the case of purging. He says that mixed gasses just don't settle out that quickly. However it's a comforting old wife's tale and we cling to it here in lieu of a better model. I also agree with your comments regarding Fixx. I admire him for championing an analytical approach to home/craft brewing, but a lot of his conclusions do not scale up. His book *is* the only one I've found that advises a specific tank purging technique for CO2, though I guess if you rule out settling you're only reducing the O2 by half.

          I made a quick review of the bookshelf and found the following. MBAA's Practical Handbook recommends "...purging for a period of time..." in addition to what it calls 'water gassing' or purging with de-aerated, sanitized water. Kunze makes several references to minimizing O2 uptake with the use of “degassed, biologically clean water” and none to CO2 purging. Malting and Brewing Science vol. 2 says “...a thin blanket of carbon dioxide may be readily produced above the beer in the donor tank, and a top-pressure of air used to move the beer out of the tank. A small amount of carbon dioxide may be injected into the main as the beer passes to the recipient tank, in such a way that it readily escapes as a gas when the beer enters the tank. Again a thin blanket of carbon dioxide covers the beer, this time in the recipient tank.” Alternatively it suggests water gassing. Siebel's notes say a tank can be “...purged with CO2, but this is an inefficient and ineffective way to achieve the CO2 atmosphere. The most effective way is to fill the tank with water, push the water out with CO2 and the fill with beer.”

          The literature seems to agree with David, though I sure don't want to work out the de-aeration, UV sanitizing and storage problems that approach presents. It seems with a proper O2 meter you could pretty easily say “blowing 3 psi CO2 into your 15 bbl tank for X mins. results in a O2 level of Y”.

          On top of oxidation concerns our CO2 is barged in rail cars from Seattle and at $0.85/lb I'd sure like to use less of it.

          Take care all.
          Clarke Pelz
          Cynosure Brewing

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          • #35
            If gases separated over time, we wouldn't have the mixed atmosphere we breathe-entropy is stronger than the different densities. It is more like the "strong" mixed drink where the liquor is poured on the top...it will only slowly diffuse until it is mixed. Ditto a black and tan. If your CO2 can go in so non-turbulently from the bottom, there will be less mixing of the gases for a while. I know that in my cold room with the blowers off, after opening a tank, the CO2 is dang strong near the floor as it is heavier, but not after a half hour or less.
            Without expensive CO2 meters, it seems like gentle (maybe by stone?) purging from the bottom has got to help especially with "Rob's Nose Hair Method." I use the same method after the tank is full of beer after three high pressure purges. Purging after filling may be more cost effective especially for that CO2 shipped in from Seattle.
            If your nose doesn't burn then there IS oxygen left, but burn doesn't prove it is all gone. I would be more concerned about air in bottles than a brewpub.
            Last edited by Moonlight; 08-11-2006, 02:56 AM.

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            • #36
              I agree. That CO2 settles is indisputable. How it does it and how fast are the questions. The model accepted by much of the brewing world is very simplified, i.e. in reality there's a lot more mixing, and settling occurs more slowly. Obviously, the CO2 has to far outweigh the air to achieve much, and regardless, the CO2 is never completely free of air. I guess if one were to grab the old physics book, it'd be possible to figure the time it takes for CO2 molecules to settle out in an undisturbed tank of CO2 mixed with air under certain conditions. Sorry, I don't have the time to play with the formulas right now...
              Last edited by crassbrauer; 08-11-2006, 05:29 AM.

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              • #37
                idea

                Great thread gang. love the discussion.

                two things...just to clarify my position on CO2 settling: I do get worried about CO2 in the cellar near the floor (there is some settling, no dispute) I also know that if my tank isn't purged totally it'll have O2.

                anyway....so I was talking with another brewer friend of mine and he uses a method I've got to tell you guys about. He routes the offgas from fermentation into his clean empty bright tanks. He just leaves the CIP arm open on the bright. Very elegant, very cheap, very effective. I'm gonna try this one out!
                Larry Horwitz

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                • #38
                  A word of caution

                  CO2-recycling is used widely in Europe, and it's a wonderful way to save money, only if you clean it and filter it first. There's all sorts of crap in there. CO2-recycling equipment cleanses the CO2 numerous times, using various methods before it's ready for use again in the brewery. Just running a hose straight to your bright tank sends anything that gets carried out with the CO2 or any of the other volatile substances created during fermentation right into your bright tank - stuff that you don't want coming into contact with your beer. Plus you're creating a substrate for infection. Your wort-/beer-spoilers will love you for it. Not cleansing it can result in infection from lactos, pedios, even other weird microbes drawn to the particular mix of substances found in fermentation blow-off. Besides, beer maturation involves getting rid of a lot things which give the beer a "young beer" flavor (acetaldehyd is commonly cited, but countless other substances are in there, like H2S, DMS, etc.). These things should be allowed to leave, not be sent to your bright tank. Odd off-flavors and aromas have resulted from reuse of funky CO2. There's a reason this is not common or mentioned in any books dealing with relatively small-scale brewing. It's also the reason brewers buy CO2 if they don't have the equipment for recycling it: It has the potential for becoming a very nasty problem.

                  Don't quote me on this, but I seem to recall a figure that CO2 recycling starts to pay for itself around 200K hl per year. This figure comes from Germany, i.e. where the Reinheitsgebot covers CO2 usage, so it may be even more in the States.
                  Last edited by crassbrauer; 08-11-2006, 12:33 PM.

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                  • #39
                    Further thoughts on "settling" of gases...a cylinder of Guinness gas doesn't give nitrogen first, then later CO2... it is mixed and stays that way.
                    As for pressurizing and venting a tank before filling, perhaps we remember from some old chemistry class that atmospheric pressure (0 psi on your gauge) is really 15 psi "absolute" (above a vacuum.) So if you have a bright tank with regular atmosphere of about 20% oxygen, and you pressurize it with pure CO2 to 15 psi on your gauge, then vent the tank down to zero again, you have only diluted the oxygen in your tank by half, or 10% oxygen. It will be 50% CO2, but this is still way too much oxygen to have in contact with your beer. Another identical purge will drop the oxygen to 5% and so on.

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                    • #40
                      Once you start talking about pressurised gas in cylinders (e.g. nitrogen/CO2 cellarmix), the much higher cylinder pressures than at relatively lower fermentation pressures make the density difference negligible. The driving force to settling out/layering depends on this difference alone, so it won't settle.

                      Also, the time to reach a signficiant settled equilbrium is probably more than any of us will live, plus the power of the Expanding Universe (entropy) will cause homogenous mixing quicker than the settling effect.

                      Now, don't mistake a strong smell of CO2 as being pure CO2 - the Austrian winemakers will kark it at CO2 levels any higher than 10% CO2. Apparently, it takes only 0.5% to cause an increase in breathing rate (and possibly burning nose hairs?), and only 3% to cause breathing at twice normal rates. Obviously, these are insiginficient concentrations when we are talking about eliminating O2 to avoid beer spoilage, and we would need to do a better job than that.

                      Reading all of the forum discussion, it sounds to me like the only acceptable method of signficiantly displacing O2 with CO2 is the water-purge method, using new CO2. However, this needs to be traded off against a) the need, depending on how long it takes to sell your beer; b) the beer storage conditions (warm or chilled); and c) any history of problems. Oh, and d) the cost (in time and $$).

                      Don't neglect the fact that quietly filling your brite tank with beer from your fermenter is necessary so as to minimise disturbance of the liquid/vapour interface - this will help reduce the instance of O2 dissolution in the beer, compared with a fountain effect inside the tank.

                      Finally, you need to check what the actual limiting factor is - is it O2 dissolved from the brite tank, or through a non-perfect pump seal, or through your filter, or residual O2 from your sterilizer (oxine?), or even hot-side oxidation back at the kettle. If any of these other sources of oxidation are sigificantly neglected, what is the point of getting a perfect transfer environment if the beer is already 'spoiled'? Take a holistic approach.

                      My 2c worth...

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                      • #41
                        What a great thread this is. Yet another reason I love these forums!
                        "By man's sweat and God's love, beer came into the world" -- St. Arnold of Metz

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                        • #42
                          Yes, apparently, gases which have been mixed, for example in a cylinder, don’t separate again, given that temperature and pressure are constant all over. I remember learning in ag shop way back in high school that you could put one component of a mixed gas in a cylinder, then another and then roll the cylinders. This didn’t mix them right away, but they would eventually mix. I think we were told to wait a week or two. (These were gases for metal shop.) As mentioned above I’m a little rusty on this, but I think this has something to do with Avogadro, the law of partial pressures, etc.

                          I think the reason a lot of the CO2 settles out and doesn’t immediately mix in an open fermentation cellar is that there’s a lot of it, and there’s very little movement to speed up the mixing, which takes a little while. It just sort of “flows” out of the fermenting beer and forms a blanket of gas on the floor. (The fans for blowing the CO2 out of open fermentation cellars are at the bottom of the room.) I think that’s why letting CO2 very slowly seep into the bottom of tank works OK for purging a bright tank. As you mentioned, Moonlight, given enough time and/or movement, the air and the CO2 in the fermenation cellar would become homogenously mixed, but I guess they’re not given the chance.

                          As done in numerous college chemistry classes, if you fill balloons with different gases, for example, helium, CO2, air and xenon gas (or some other heavy gas), they’ll rise or sink according to their density compared with air. If you pop a helium balloon, though, the gas disperses around the room, because the room is huge compared to the tiny volume of the balloon. One thing this thread speaks for is the importance of some knowledge of physics and chemistry for brewers. I’ll put dusting the cobwebs off of those subjects on my long list of things to do.

                          As already mentioned a few times in this thread, the first question to ask yourself before taking drastic measures is: Do I have an oxygen problem, and if so, where is it?
                          Last edited by crassbrauer; 08-13-2006, 12:28 PM. Reason: can't spell

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                          • #43
                            If you like toys, check out the Oxy/Nitro gas meter in the Micromatic catalog. It is a bit crude but basically tells you the amount of CO2 in a venting gas, so you can see how effective your purging is.

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