[BrewBama]

So, I am reading an email notification for a tweet sent to me by AHA today. Source: “A Bottler’s Guide to Kegging” by Ed Westemeier (Summer 1995 Zymurgy) https://www.homebrewersassociation.org/how-to-brew/an-introduction-to-kegging-homebrew/

In this article it says “Once the keg is sanitized, it is time to prepare for racking by purging the keg of oxygen, which could cause oxidation. Connect the CO2 tank to the gas-in fitting and set the regulator to 5 PSI. Turn on the CO2, allow gas to flow for five seconds or so, and then turn off the CO2. Because CO2 is heavier than oxygen, it will fall to the bottom of the keg, forming a protective layer against oxygen as the beer is racked.”

It goes on to say “After the initial purge, rack the beer into the keg and seal the hatch. Again, set the regulator to 5 PSI, turn on the CO2 to fill the keg’s head space, and turn off once you can no longer hear gas flowing. Open the pressure release valve to let the pressure out. Continue this process three or more times to purge remaining air from the headspace, and then shut off the CO2.”

Can we get an instant replay ‘under further review from the officials’ style decision from the AHA on this along with an edited/corrected article?  I do not believe CO2 will settle to the bottom of a vessel and create a blanket of gas under which a liquid can be racked.  Also, purging a keg a few times will not eliminate oxygen. ...I’ve read it’s more like thirty times. Of course, I guess thirty is more than three so the article is accurate but misleading in this regard. The AHA should be the go-to source for homebrewers and therefore misinformation should be corrected.


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[Robert]

As far as I know you're absolutely right, except maybe even 30 times will leave significant O2. I can never keep all those gas laws straight, but I know I learned at some point that gases will always exchange and mix. (Why you can loosely cover a starter with foil an O2 will get through the CO2 blanket, for instance.) Especially when you're blasting one into the other!  Simple sure way to totally purge? Fill keg completely with water and push it out with CO2. I'd wager you use less gas too. (I'm guessing thats what you do?)

[hopfenundmalz]

I looked at it in this thread. Take away - purge 11 times at 30 PSI to get ~1ppm. Yeah, 5PSI for a few times won’t get it low enough.

https://www.homebrewersassociation.org/forum/index.php?topic=23682.msg302849#msg302849

[Robert]

I looked at it in this thread. Take away - purge 11 times at 30 PSI to get ~1ppm. Yeah, 5PSI for a few times won’t get it low enough.

https://www.homebrewersassociation.org/forum/index.php?topic=23682.msg302849#msg302849

Wow, those calculations got my head spinning, glad somebody else did them for us!  Makes my adopted procedure seem a lot simpler  -- liquid out with gas, beer in through the spear pushing gas back out the PRV.  No cipherin' needed, not much gas wasted.  Even a beginning kegger could do this.  The only additional item they'd need is a flare nut on the end of their racking tube.

[BrewBama]

I looked at it in this thread. Take away - purge 11 times at 30 PSI to get ~1ppm. Yeah, 5PSI for a few times won’t get it low enough.

https://www.homebrewersassociation.org/forum/index.php?topic=23682.msg302849#msg302849

Thank you for this. If this information is accurate, I believe the article should be edited with this vs the current method. Can we get a correction in the interest of accuracy?


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[Richard]

If you pull a vacuum to pump out all the gas before filling with CO2 you can reduce the number of cycles to just a few to get to 1 ppm, depending on how low you can go in pressure. Of course your keg may crumple when you try this because it isn't designed to withstand pressure from the outside.

[Robert]

See that's why using water or sanitizer is good, no imploding kegs. Of course there's dissolved O2 in the liquid, but somebody could probably tell us how many cycles it would take to purge that to safe level, and I'm sure it would save much gas. Or maybe that level (in water adhering to sides of keg) is already acceptable.  I never worry about it.

[Stevie]

Wait, a 22 year-old article, written by total amateurs, has bad information?

[Robert]

^^^^  😂

[klickitat jim]

I think that's passed the statue of limitations

[Robert]

I think that's passed the statue of limitations

Okay,  so we won't prosecute the author for passing counterfeit info.  But the OP makes a good point, AHA ought to endeavor to provide up-to-date info (back in the day that was conventional wisdom,  none of us had those übergeeky equations Jeff posted!)  I've had the same thought about some of the ridiculously outdated  books still in print.  Beginners aren't well served by this organization if they can't benefit  from the decades of learning from mistakes that the rest of the hobby has gone through.

[hopfenundmalz]

The AHA staff has been contacted, they will decide the appropriate action.

[Robert]

The AHA staff has been contacted, they will decide the appropriate action.

Great to hear that!

[RC]

I do not believe CO2 will settle to the bottom of a vessel and create a blanket of gas under which a liquid can be racked. 

The laws of physics and chemistry contradict this. CO2 is heavier than O2, and so CO2 will settle to the bottom of the vessel and create a blanket of gas under which a liquid can be racked. Does this eliminate all O2 pickup? No. Gasses of different density will always mix a bit, especially at their interface. Which leads to another question: does it matter (at the homebrew level)? No, as long as one takes reasonable care to minimize O2 pickup while racking. Also, drink your homebrew fresh! (i.e., quickly, which has never been a problem in my house). I don't mean to start an O2 debate here, but oxygenation at the homebrew level is a colossally overblown non-issue. There seems to be an endless debate about the effect of O2 on homebrew, when really, there are so many other variables that matter far, far more. Here's one (and only one, granted) bit of evidence: http://brulosophy.com/2016/12/19/post-fermentation-oxidation-pt-1-normal-vs-high-oxidation-exbeeriment-results/

[Robert]

I do not believe CO2 will settle to the bottom of a vessel and create a blanket of gas under which a liquid can be racked. 

The laws of physics and chemistry contradict this. CO2 is heavier than O2, and so CO2 will settle to the bottom of the vessel and create a blanket of gas under which a liquid can be racked. Does this eliminate all O2 pickup? No. Gasses of different density will always mix a bit, especially at their interface. Which leads to another question: does it matter (at the homebrew level)? No, as long as one takes reasonable care to minimize O2 pickup while racking. Also, drink your homebrew fresh! (i.e., quickly, which has never been a problem in my house). I don't mean to start an O2 debate here, but oxygenation at the homebrew level is a colossally overblown non-issue. There seems to be an endless debate about the effect of O2 on homebrew, when really, there are so many other variables that matter far, far more. Here's one (and only one, granted) bit of evidence: http://brulosophy.com/2016/12/19/post-fermentation-oxidation-pt-1-normal-vs-high-oxidation-exbeeriment-results/

I think the issue here is, not how worried should homebrewers be about this, but giving them the correct information so they can make that decision for themselves. Especially in an article presented as an introduction for people looking to learn a new aspect of brewing technique.
And really, the CO2 will settle out if you blow it into a keg of air? How long will that take? Won't whoever's law it is that says that gases in a mixture will behave as if the others don't exist take precedence? (I said in an earlier reply I can't keep those laws straight. )
My point is, information should be made available so that, at whatever level you find yourself , you can proceed in an informed way,  making your own choices. Knowledge is power, ignorance is, well, ignorance.  Antiquated dogma that says "do this, it must work, everybody does it" is not educational.

EDIT: Guess what I'm saying is, beginners should be given a thorough overview and then given choices:  What's your level of risk aversion?  If low , this will do.  If high,  click here for more options.   Something like that.  That would be a good intro article. And once every generation, all publications need to be replaced.