Is this chart strictly for a 5 gallon keg and since I use 2.5 gallon kegs would I have to purge half as many times?
No. The headspace is just as wide.
Is this chart strictly for a 5 gallon keg and since I use 2.5 gallon kegs would I have to purge half as many times?
For those who are filling thru the liquid out posts after liquid purging their kegs, how do you deal with existent O2 in the lines when transferring beer from the FV? That would still seem to be part of the "closed system".
For those who are filling thru the liquid out posts after liquid purging their kegs, how do you deal with existent O2 in the lines when transferring beer from the FV? That would still seem to be part of the "closed system".
I use the same tubing I used to drain the StarSan for racking. No disconnection between processes. The tubing is full of CO2 after all the SS is blown out.
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So are you using a quick disconnect to evacuate the starsan, and connecting that same disconnect attached to your fermenter?
That will do a pretty good job of getting the O2 level down. It's not because of diffusion however. The reduction in O2 (and N2) is strictly due to dilution. The purge pressure affects how many purge cycles you need to get to a particular O2 level. The table and chart below shows how pressure and number of cycles affects the O2 levels. The values are percent of original remaining, not mass of remaining. The mass remaining depends on the headspace volume.
View attachment 323772
View attachment 323773
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What is your definition of a purge cycle for your charts, a complete depressurization and pressurize or a blast/burp release from the PRV?
Pressurize again to 14.7 psig, and the headspace is now 1/4 air and 3/4 CO2, and the O2 percentage is down to 5.25%. Rinse and repeat.
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This is a really good example of why CO2 purging is not a sufficiently effective process for O2 reduction . No question it reduces it, but even after a dozen purge cycles it's still above the thresholds. Air just has a huge concentration of oxygen...
Water purging an empty keg is the only way to go.
My first ever starter keg kit arrived yesterday. No instructions came with it at all so started some research.
Now after reading this I think I may stick to bottles no for now. Is it really this complicated?
It just seemed to me people are getting fixated with wiping out all oxygen, so that was putting me off. When you bottle you leave an inch at the top so what's the issue? Just do a bit of purging and should be ok right?
Good info in here, just a question. How long can you store a corny full with star at room temp??
1. Pushing Star San will still leave a few oz of star san in the keg.
2. I almost never have a gallon's worth of head space in my keg. Maybe more like an 1/8 to a 1/4 gallon. So, then the purge the headspace technique might use less than pushing 5 gallons of Star San.
3. Now comes the question part. [...]
...
If i remember correctly it takes like 30 purges at 30 psi to dilute the air inside the keg down to what is considered ok levels. This also assumes perfect mixing. ...
The diffusion of oxygen from air into water (or beer) is actually quite fast. The calculations and numbers have been discussed around here before. Maybe someone can dig up a thread link.
Folks there is a ton of incorrect information in this thread. Trying to correct a couple inaccuracies to help out here and save folks a lot of cash.
1) I hate to be the bearer of bad news but one should never put unsanitized tap water in a sanitized keg without resanitizing prior to adding your brew. If you think tap water is “clean” you are mistaken and it doesn’t matter where you live.
2) CO2 is quite a bit heavier than O2 (remember the C in CO2 is Carbon) so CO2 is C+O2. Given this quality it is not necessary to purge a keg multiple times to remove virtually 100% of O2.
3) Simply pushing CO2 through liquid post at low psi while opening keg safety release valve for a few seconds is sufficient to remove O2 from a keg. As CO2 is heavier than O2 it will not “leak” out if keg topper is opened (this should be done in a draft free environment).
4) Here is a simple video that clearly shows the weight differences between CO2 and O2.
If gases worked this way, we would all die of suffocation as all the O2 went to the top of our atmosphere and all the CO2 settled. Well, Denver might survive...Folks there is a ton of incorrect information in this thread. Trying to correct a couple inaccuracies to help out here and save folks a lot of cash.
2) CO2 is quite a bit heavier than O2 (remember the C in CO2 is Carbon) so CO2 is C+O2. Given this quality it is not necessary to purge a keg multiple times to remove virtually 100% of O2.
I actually authorized this post out of the moderation hold queue, but it was time to leave for dinner, so I was hoping someone else would step up to the plate with corrections. @schematix covered the errors pretty well. It anyone wants more gory detail and references, let me know.Noobs are fun, especially with fundamental stuff.
@doug293cz should be along any minute to fix all the broken china
So where is the DO measurement to support all this purging math?
The dilution math has been established p-chem for more than a century. The limitations to the analysis are:I believe @schematix on this stuff very much more than I believe the survival doc. However I’d really like to see some experimental data using a ppb sensitive DO meter on some of the keg purging techniques that I see on this and other forums being supported by lots of math and pretty graphs.
I’d like to see...
DO in beer in purged keg using the following techniques
No purge, just gravity fill with minimal splashing then purge the headspace with CO2 half a dozen times
Purge keg a few times then fill closed transfer
Purge keg with a full star San push then fill closed transfer
Purge keg with boiled water push then fill closed transfer
All of the above followed by
Force carbing
Opening top and priming sugar followed by purging head space
Spunding
Then finally don’t forget keg after one week hooked up to CO2 in kegerator
It’s not like I don’t believe math but you know what the say about figures never lie but liars do figure.
So where is the DO measurement to support all this purging math?
Not really. As moderators, we only check to see that the held posts comply with HBT rules, and approve anything that does. We don't pass judgement on technical validity. And, I don't think you would want us to do so. So, my only choice was to approve the post, and come back later and address the technical inaccuracies in a reply post. That gives the OP, and other members, a chance to weigh in on both the OP and any replies.So you could have prevented a train wreck but you thought it would be entertaining?
Cheers!
I knew it was probably a rhetorical question, but thought that providing a little insight into how moderation is done might be helpful to people (especially those that didn't realize it was a rhetorical question.)Of course, I totally get all that.
I should have stuck the "Rhetorical Question" tag on that. My bad...
Cheers!
There's a lot of info out there already so i'm not going to rehash it all. This link has been posted here before and is one of the most thorough explanations i've seen: http://www.********************/brewing-methods/beer-serving-oxygen-ingress/
The gist of it is that oxygen comes from multiple sources, including packaging and even after that since there's no such thing as a perfect seal. It is also consumed (i.e. reacts with other compounds) inside the keg so that it's not just free dissolved oxygen anymore. You can't measure that.
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