Author Topic: Pediococcus...Diacetyl...Causes?  (Read 2827 times)

Offline roguejim

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Re: Pediococcus...Diacetyl...Causes?
« Reply #15 on: February 23, 2012, 02:25:29 PM »
Not to derail the original posting much further, but I'm not understanding all of this.  After you've purged the keg, what happens when you remove the lid to introduce your siphon tubing?  Does the CO2 not escape?  O2 doesn't enter the keg, displacing the CO2?

Offline morticaixavier

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Re: Pediococcus...Diacetyl...Causes?
« Reply #16 on: February 23, 2012, 02:28:51 PM »
Not to derail the original posting much further, but I'm not understanding all of this.  After you've purged the keg, what happens when you remove the lid to introduce your siphon tubing?  Does the CO2 not escape?  O2 doesn't enter the keg, displacing the CO2?

no, now the relative densities do indeed come into play. as long as you are careful not to move the keg much after opening, and you don't tip the keg at all then the co2 sitting in the keg will not allow air to enter. co2 is heavier than air. you will see it if you dump the presure and open the lid the whole keg will be filled with vapour. that's the co2 and it just sits there, although you can see it swirling around at the keg mouth a bit. then you attach your syphon hose to a QD and attach that to the beer out post and rack you beer gently to the bottom of the keg. This will force the co2 up and out as the beer fills and any minor amount of 02 that did mix at the keg mouth will leave quickish.
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Offline majorvices

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Re: Pediococcus...Diacetyl...Causes?
« Reply #17 on: February 23, 2012, 02:33:50 PM »
I agree absolutely that having a medium in the keg (or whatever) assures that you purge out all the o2. But I disagree that if you let the co2 run long enough that you don't purge out most if not all of the co2. If you have a glass of milk and you pour water into it the water and milk will mix. But if you pour long enough you will end up with all water.
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Offline morticaixavier

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Re: Pediococcus...Diacetyl...Causes?
« Reply #18 on: February 23, 2012, 02:36:09 PM »
I agree absolutely that having a medium in the keg (or whatever) assures that you purge out all the o2. But I disagree that if you let the co2 run long enough that you don't purge out most if not all of the co2. If you have a glass of milk and you pour water into it the water and milk will mix. But if you pour long enough you will end up with all water.
yeah, I admit it borders on ocd and probably doesn't matter either way. just being a pedant.
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Offline kylekohlmorgen

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Re: Pediococcus...Diacetyl...Causes?
« Reply #19 on: February 27, 2012, 09:39:45 PM »

purgeing kegs: If you add co2 to an empty (air filled) keg and then release the presure and then repeat you will not get all the o2 out. yes o2 is lighter than co2 but it is still a gas. alchahol is lighter than water but if you pour water into a glass of rubbing alchahol until it overflows an amount equal to the volume of alchahol you do not end up with pure water. fluids mix. They may not stay mixed but they do mix...


Fluids DO mix. However, with gases you can take advantage of the pressure difference from your resident gas (air - oxygen) and your purging gas (CO2).

If you're purging with CO2, you're using 5-20 psig gas to purge 0 psig (atmospheric) gas. A few purges is with pressurized CO2 is PLENTY - as long as the purges come up to pressure and you're not just blowing CO2 through an open valve.

When we have to push ALL the oxygen out of our batch reactors (at work), we use nitrogen at 30 psig. We use 3-30psig purges to get the O2 levels < 0.5%. Obviously, N2 and O2 are miscible - its the pressure difference that counts.
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Offline tschmidlin

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Re: Pediococcus...Diacetyl...Causes?
« Reply #20 on: February 27, 2012, 11:11:41 PM »
When we have to push ALL the oxygen out of our batch reactors (at work), we use nitrogen at 30 psig. We use 3-30psig purges to get the O2 levels < 0.5%. Obviously, N2 and O2 are miscible - its the pressure difference that counts.
That's an interesting method I hadn't considered.  Of course it would work, you're adding ~30 times more N2, venting, repeat.  The O2 level will fall ~30 fold each time you do it.  Clever.  :)  It will take a lot of gas that way, more than just pushing out starsan, but if that's not a concern for you then it's a great way to do it.
Tom Schmidlin