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Thread: 50 SCFM for a spunding valve on 15bbl tanks?

  1. #1
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    50 SCFM for a spunding valve on 15bbl tanks?

    was offered some back pressure regulator valves that are 2 bar and 50 SCFM rated. psi is fine, but is the SCFM rating enough for a typical 15bbl FV?

    i attempted to crunch numbers in my head until i realized that while i could approximate the static volumes involved, i had no idea how fast the co2 is being generated in any technical sense outside of "few bubbles" "alot of bubbling" and "outboard motor in a bucket."

    so hopefully someone can chime in here who has a firm grasp of the details.

    thanks

  2. #2
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    Somebody had better check my calculations but based on a 12 plato (approx. 48 SG) wort, volume 17.5 hl (15 US brl) fermenting at a steady state over 4 days (96 hours) this would give off 560 litres of CO2 at STP (which is not quite the same value as SCFM, but close enough for a VERY crude calculation) per hour, or .35 cu ft / minute.

    So even allowing for changes in standard temperature an pressures, by my calcs an understanding of SCFM it looks as though this is plenty big enough capacity.

    I haven't used the calculation, but check out

    https://farnam-custom.com/resources/...he-difference/

    Where they give a better pressure / temperature conversion than I could be bothered to do in a few minutes.


    If someone wants to give a more accurate figure, I would be pleased to see the results of a better calculation.
    dick

  3. #3
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    I've wondered about using back pressure regulators in this application before, yet all the spunding valves I've seen (admittedly not that many) have a water seal on them. Is this really necessary, or would a regular sanitary BPR work as well?

    Regards,
    Mike Sharp

  4. #4
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    unfortunately these arent sanitary. so my thought was to run blow off tube to a small pressure vessel like a corny or hopback or something similar. fill with no foam sanitizer, then mount the regulator above the vessel. not a perfect solution but should keep some distance between any krauzen and the regulator.

    i've never conditioned in a fermenter before so this is a bit new to me. planning to add a bit of dextrose and some F2 to do a dryhop/ carbing combo, hoping that F2 is not a huge krauzen generator and that the hops help keep it from foaming up too much to cause any issues.

  5. #5
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    Quote Originally Posted by brain medicine View Post
    unfortunately these arent sanitary. so my thought was to run blow off tube to a small pressure vessel like a corny or hopback or something similar. fill with no foam sanitizer, then mount the regulator above the vessel. not a perfect solution but should keep some distance between any krauzen and the regulator.

    i've never conditioned in a fermenter before so this is a bit new to me. planning to add a bit of dextrose and some F2 to do a dryhop/ carbing combo, hoping that F2 is not a huge krauzen generator and that the hops help keep it from foaming up too much to cause any issues.
    Make sure there's no way for the liquid in the secondary vessel to make it back into your fermenter, in case temperature drops, or you drain something off the tank. I realize it's under pressure, but I think the spunding valves are constructed like a homebrewing airlock so that it's not possible to suck that liquid back in. Your PRV will protect the tank from vacuum, but I'll bet there's a point between zero pressure and the level of vacuum that activates your PRV where blowoff can get sucked back.

    In fact, now I think on it, if your pressure is, say 5psi, and for whatever reason the pressure in the FV drops, then you have more pressure in the secondary vessel than the FV, and it will push that liquid right back in the FV.

    Regards,
    Mike Sharp

  6. #6
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    The figured spund at room temp and about 25 or 27 psi as I recall. But keeping a CO2 line on it at 12 with check valve. Once it's done carbing then disconnect the spund and then slowly cool to crash temp.

    Beer absorbs the CO2, pressure goes from 25ish to 12ish, and CO2 supply only kicks in if tank goes below 12. You'd need failure of pvrv as well as CO2 to get vacuum. Few folks I've talked to reported a period of days to week for natural carb. So I got the impression these aren't t fast drastic changes in temp and psi.

    As for suck back, I'd think that's only solved with two cornys. First is empty with two short dip tubes. Second holds sanitizer.

    Although at that point you might be approaching the cost of a real spund valve?

  7. #7
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    Quote Originally Posted by brain medicine View Post
    [...]

    As for suck back, I'd think that's only solved with two cornys. First is empty with two short dip tubes. Second holds sanitizer.

    Although at that point you might be approaching the cost of a real spund valve?
    Hey, that's a clever idea. Maybe if you had a short and long dip tube in the first one, but connect the long tube to the second corny, once the CO2 started flowing again, I think it would simply push that sanitizer back into the second one.

    But yeah, probably as costly, and certainly a lot more trouble, and ultimately less sanitary.

    Regards,
    Mike Sharp

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