How does one purge a vessel with CO2?

Tippsy-Turvy · Mar 29, 2016

New to kegging here, having just found a CO2 supplier that did not cost an arm and leg (just a lower leg).

How does one purge any vessel without posts eg bottling buckets, secondary carboys etc? My regulator & tube connections are all tightly clamped after tracking down a small leak and I can't imagine whenever I want to purge something having to unscrew the joints, reattaching something else and re-screwing on the joints.

GilSwillBasementBrews · Mar 29, 2016

I fill the keg with water and push it out till empty with co2. Purged empty pressurized keg waiting for filling. Doesn't happen often but that's how I do when I need to.

GilSwillBasementBrews · Mar 29, 2016

Oh I misunderstood your post. I would just use a ball lock gas post or carbonator cap if you have one. Or unscrew the disconnect from the flare fitting.
Edit: nevermind I see you have barbed hose connections. I have flare connections so not as much a PITA for me to unscrew and rescrew the disconnect.

jcav · Mar 29, 2016

You could buy a gas keg post and snap it on your gas disconnect, and then hang the post into the opening of whatever type of vessel you want to put C02 into (carboy, bucket, or whatever). This is one way of getting there......Just a thought.

John

k1ngl1ves · Mar 29, 2016

MFL is your friend...

jcav · Mar 29, 2016

k1ngl1ves said:
MFL is your friend...

Exactly, that is the best route, but I saw you already had barbed fittings....

k1ngl1ves · Mar 29, 2016

jcav said:
Exactly, that is the best route, but I saw you already had barbed fittings....

It's very cheap to switch over with the limited setup pictured. $10 or less. Probably the cheapest solution...

Tippsy-Turvy · Mar 29, 2016

Thanks guys, except you're speaking an alien language to me!

What's MFL? The extra post is an interesting idea, but wouldn't a standalone post need the poppet thing inside it in order to press the pin-thing that's inside the gas disconnect-thing?

jcav · Mar 29, 2016

You could change your gas disconnect to this MFL type fitting: http://www.northernbrewer.com/brewing/kegging/gas-hardware/gas-disconnects/ball-disc-1-4-mfl-gas
Then screw on this barbed swivel nut to your gas lines: http://www.northernbrewer.com/barbed-swivel-nut-k163
Then you just unscrew the connection and put the gas line into your carboy. This is a much easier way of doing it. Hope this helps.....

John

Tippsy-Turvy · Mar 30, 2016

Outstanding!

MLF is my new friend.

jddevinn · Mar 30, 2016

Remember you are not "purging" by simply injecting CO2 into a container, you need to push out the air that is in there with something other than CO2 (CO2 will mix with the air not displace it), most people use sanitizer solution for this.

You should really have a check valve in the assembly as well (so say if you hook up a keg that is at a higher pressure than the regulator setting you don't flood the regulator with beer). When you switch to flared fittings adding a manifold with multiple connections doesn't cost much.http://www.northernbrewer.com/brewing/kegging/gas-hardware/gas-distributors

k1ngl1ves · Mar 30, 2016

jddevinn said:
Remember you are not "purging" by simply injecting CO2 into a container, you need to push out the air that is in there with something other than CO2 (CO2 will mix with the air not displace it), most people use sanitizer solution for this.

While true, displacing with a liquid is a bit overboard. People here get pretty crazy when discussing oxidation. (And no, I'm not singling you out jd. Just making an observation from the countless times I see this posted.

)

In a small open top vessel, flushing it with co2 from the bottom at an adequate pressure (anywhere from 10-20psi) will lower the oxygen content immensely. Yes, it will mix with the gasses already in the vessel, but gasses are also escaping out the top. You can lower the oxygen content to to a negligible level in a very short time. You won't get all the oxygen out, but it's not necessary anyways.

I should become a vendor here and start selling tinfoil hats with a big "O2" on them. I'll make a killing...

:ban:

Tippsy-Turvy · Mar 30, 2016

Great pointer. But how about purging with a really low flow rate, say 1 psi? Wouldn't that minimize gas mixing and push out the air more effectively?

k1ngl1ves · Mar 30, 2016

Tippsy-Turvy said:
Great pointer. But how about purging with a really low flow rate, say 1 psi? Wouldn't that minimize gas mixing and push out the air more effectively?

I would rather use more force, and try and push more air faster. Quicker is better, imo. The gases are going to mix no matter what. Concentrate the air with co2, and in turn minimize the amount of o2 by pushing the mixed air out the top.

jddevinn · Mar 30, 2016

k1ngl1ves said:
While true, displacing with a liquid is a bit overboard. People here get pretty crazy when discussing oxidation. (And no, I'm not singling you out jd. Just making an observation from the countless times I see this posted. )

In a small open top vessel, flushing it with co2 from the bottom at an adequate pressure (anywhere from 10-20psi) will lower the oxygen content immensely. Yes, it will mix with the gasses already in the vessel, but gasses are also escaping out the top. You can lower the oxygen content to to a negligible level in a very short time. You won't get all the oxygen out, but it's not necessary anyways.

I should become a vendor here and start selling tinfoil hats with a big "O2" on them. I'll make a killing...

The issue with what you describe is that is it is not how gases interact (although you do acknowledge that the gasses will mix

). Pushing a cubic meter of O2 into the bottom of a carboy/keg/whatever does not mean that you push a cubic meter of the gas that is in the top of the carboy out. For the pressure to exert on gas in the top the particles underneath must push on it. Mixing of gases in this environment is very fast. In reality the gas "pushed" out of the top of the container is a mixture of what was in the container to begin with and what was added. The size opening in the top of the vessel has zero affect on the mixing of the gases internally (unless the opening is small enough for the internal gas to pressurize). The flow rate will have the effect of higher flow will promote faster mixing of the gasses but offset diffusion from outside of the container.

Quick math on a 5 gallon container with the assumptions of below shows the amount of #'s CO2 and PPM of O2 remaining with a "constant" flush. If you want to ignore all technical publications/books I have found or say that you drink your beer before oxidation effects take place then do so.... however, it can not be said that methods other than vacuum/pressure combination or positive displacement of liquids reduces concentration of 02 to a the range recommended by all technical sources. One of these days I'm going to find a decent dissolved O2 meter for cheap and get some empirical results.

Many people do ignore O2, many people don't control fermentation temp, many people ignore yeast counts, many people do lots of things and still make decent to good beer.

1.standard atmospheric conditions
2.mean free paths are not calculated, gases are assume to mix (this will make the calc slightly conservative)
3.Simplified to multiple small steps to eliminate integration
4.flow rate effects are not considered
5.pressurization of the vessel due to inlet vs discharge flow rates are not considered

jddevinn · Mar 30, 2016

I've never done a bucket but kegs are easy to purge with sanitizer and carboys can be purged with a simple cap and racking cane (configured like below). Pushing a sanitizer will also use less gas than a two or three step or continuous purge. If you have an extra keg just keep one with 5 gals of sanitizer at all time!

k1ngl1ves · Mar 30, 2016

jddevinn said:
The issue with what you describe is that is it is not how gases interact (although you do acknowledge that the gasses will mix ). Pushing a cubic meter of O2 into the bottom of a carboy/keg/whatever does not mean that you push a cubic meter of the gas that is in the top of the carboy out. For the pressure to exert on gas in the top the particles underneath must push on it. Mixing of gases in this environment is very fast. In reality the gas "pushed" out of the top of the container is a mixture of what was in the container to begin with and what was added. The size opening in the top of the vessel has zero affect on the mixing of the gases internally (unless the opening is small enough for the internal gas to pressurize). The flow rate will have the effect of higher flow will promote faster mixing of the gasses but offset diffusion from outside of the container.

Quick math on a 5 gallon container with the assumptions of below shows the amount of #'s CO2 and PPM of O2 remaining with a "constant" flush. If you want to ignore all technical publications/books I have found or say that you drink your beer before oxidation effects take place then do so.... however, it can not be said that methods other than vacuum/pressure combination or positive displacement of liquids reduces concentration of 02 to a the range recommended by all technical sources. One of these days I'm going to find a decent dissolved O2 meter for cheap and get some empirical results.

Many people do ignore O2, many people don't control fermentation temp, many people ignore yeast counts, many people do lots of things and still make decent to good beer.

1.standard atmospheric conditions
2.mean free paths are not calculated, gases are assume to mix (this will make the calc slightly conservative)
3.Simplified to multiple small steps to eliminate integration
4.flow rate effects are not considered
5.pressurization of the vessel due to inlet vs discharge flow rates are not considered

Hmmm. I look at the graph you provided, and it does appear that the concentration of O2 drops rather quickly! Of course, I could be (and most likely) interpreting it incorrectly. What would you say is a safe level of O2, or rather what range is "recommended by all technical sources"? I mean, based on your findings, then pretty much 99.999999999% of all homebrewed, kegged, then aged stouts are oxidized and a subpar product? I'm not sure. After all, the standard practice is to quick purge the keg with co2 and then rack the beer into the keg.

So almost every homebrewing kegger makes subpar, oxidized libations. This saddens me. Now I'm always gonna have to ask if someone displaced the air in their keg with liquid before racking. If not, then I'll turn my nose up to their crappy oxidized beverages and proclaim "There's no replacement for liquid displacement!" (Am I going too far? It is a catchy slogan!)

Anyways, I thought I'd post my own spiffy graph that I found on the internets for your critique. Let me know if there's any questions, and I'll try to decipher for you!
:ban:

jddevinn · Mar 30, 2016

k1ngl1ves said:
Hmmm. I look at the graph you provided, and it does appear that the concentration of O2 drops rather quickly! Of course, I could be (and most likely) interpreting it incorrectly. What would you say is a safe level of O2, or rather what range is "recommended by all technical sources"? I mean, based on your findings, then pretty much 99.999999999% of all homebrewed, kegged, then aged stouts are oxidized and a subpar product? I'm not sure. After all, the standard practice is to quick purge the keg with co2 and then rack the beer into the keg.

So almost every homebrewing kegger makes subpar, oxidized libations. This saddens me. Now I'm always gonna have to ask if someone displaced the air in their keg with liquid before racking. If not, then I'll turn my nose up to their crappy oxidized beverages and proclaim "There's no replacement for liquid displacement!" (Am I going too far? It is a catchy slogan!)

Anyways, I thought I'd post my own spiffy graph that I found on the internets for your critique. Let me know if there's any questions, and I'll try to decipher for you!

hahaha

The drop is rapid...However when I stopped copy pasting iterations I was sitting at .068#'s of CO2 used and >1,500ppm O2 remaining! I of course made some assumptions, and this is likely conservative however illustrates the trend....an open air purge will never get to what I consider an OK oxygen concentration. Pushing sanitizer will use LESS gas and get a much LOWER O2 content with little to no additional effort.

Sources used to teach brewing science such as Brewing Science and Practice are of course more stringent than most homebrewers and assume the finished product should be consistent and have a several month shelf life.

Commercially, piping and fermenters are flushed with nitrogen, alternatively the beer is supersaturated with CO2 during transfer so that when it arrives at the location it is being transferred to it off gasses CO2 itself and displaces the air in the vessel. Or they fill the receiving tank with a deaerated (I don't go this far!!!) liquor that they push out with CO2.

Target for transfer to a brite tank (secondary) is around 50ppm or less. At the end of maturation the target should be <0.01ppm and at packing should be <0.2ppm.

Of course these targets are unreasonable with homebrewing equipment and are exacerbated by the use (sometimes) of pasteurization. However roughly 1ppm is enough to oxidize all reductones in a light beer, of course darker beers will require more and the off flavors will be harder to detect.

Yes I would say ALL brew is oxidized to a point, with MOST homebrew exceeding the commercial recommendations and a Majority of it contributing to off tastes either immediately or over time.

All the dissolved oxygen limits here come from Brewing Science and Practice. Attached are curves made by doug293cz showing the oxygen content of pressure purged vessels.

k1ngl1ves · Mar 30, 2016

jddevinn said:
hahaha

The drop is rapid...However when I stopped copy pasting iterations I was sitting at .068#'s of CO2 used and >1,500ppm O2 remaining! I of course made some assumptions, and this is likely conservative however illustrates the trend....an open air purge will never get to what I consider an OK oxygen concentration. Pushing sanitizer will use LESS gas and get a much LOWER O2 content with little to no additional effort.

Sources used to teach brewing science such as Brewing Science and Practice are of course more stringent than most homebrewers and assume the finished product should be consistent and have a several month shelf life.

Commercially, piping and fermenters are flushed with nitrogen, alternatively the beer is supersaturated with CO2 during transfer so that when it arrives at the location it is being transferred to it off gasses CO2 itself and displaces the air in the vessel. Or they fill the receiving tank with a deaerated (I don't go this far!!!) liquor that they push out with CO2.

Target for transfer to a brite tank (secondary) is around 50ppm or less. At the end of maturation the target should be <0.01ppm and at packing should be <0.2ppm.

Of course these targets are unreasonable with homebrewing equipment and are exacerbated by the use (sometimes) of pasteurization. However roughly 1ppm is enough to oxidize all reductones in a light beer, of course darker beers will require more and the off flavors will be harder to detect.

Yes I would say ALL brew is oxidized to a point, with MOST homebrew exceeding the commercial recommendations and a Majority of it contributing to off tastes either immediately or over time.

All the dissolved oxygen limits here come from Brewing Science and Practice. Attached are curves made by doug293cz showing the oxygen content of pressure purged vessels.

So what you're saying is... I can't stop oxidizing my beer. But I can fill my 5g corney keg with 4.8 g (normally about what I put in), purge it 15 times at 20 psi, and I should be good to go? No?

I seriously think this is gonna take more graphics... :ban:

jddevinn · Mar 30, 2016

k1ngl1ves said:
So what you're saying is... I can't stop oxidizing my beer. But I can fill my 5g corney keg with 4.8 g (normally about what I put in), purge it 15 times at 20 psi, and I should be good to go? No?

I seriously think this is gonna take more graphics...

You could do this, you are going to get some oxygen uptake during the transfer and probably use more CO2 than if you push a keg of sanitizer. However, the beer IS slightly carbonated (especially if cold crashed under positive pressure) and will off gas some during transfer to protect it. The PPM count in multi purge charts are not volume dependent so yes you would get to less than 1ppm in the headspace

Seriously though... my cleaning process is

clean keg
rinse keg
grab my keg of sanitizer
hook a small beer line connected to (2) beer out quick disconnects to both kegs out posts
Hook up a QD with hose into a bucket, or just open the PRV on the empty keg (messier)
attach gas to sanitizer keg
makes a lot of noise when done transferring because it starts "spitting" starsan foam CO2 mix
store sanitizer keg
have cleaned, sanitized purged keg

If I (rarely) need my last keg for some reason other than storing sanitizer I either dump and make a new batch next time or push into a bucket, store, then poor into the new keg.

Less CO2 wasted and less O2 uptake.

k1ngl1ves · Mar 30, 2016

I think I like where this conversation is going...

jddevinn · Mar 30, 2016

k1ngl1ves said:
I think I like where this conversation is going...

haha,yes. For kegs and carboys I would summerise

Best method, fill as much with sanitizer and push out with CO2. Least amount of O2, uses the least amount of CO2, easy. Drink beer at your leisure as if other process are good it's as stable as you can get. (great if you, like me have 8+ taps)
OK method, purge keg a couple dozen times, transfer beer, purge headspace a couple dozen times. Similar amount of O2as 1, wastes a lot of CO2
Decent, transfer beer with minimum agitation, purge headspace a couple dozen times. More O2 than 1 and 2, saves gas over 2 but probably still uses more than 1
Open keg top and push CO2 into the bottom of the keg with lid open. Transfer beer with minimum agitation, purge headspace a couple dozen times. Pretty much same as 3 but wasted CO2
Not care, dump beer into keg, don't purge headspace, hook to CO2 and force carb. Come online and ask about the color change (darkening) of your light beer, the off flavors and change in taste while storing.

zoom out on that animal a bit...

Tippsy-Turvy · Mar 30, 2016

jddevinn said:
haha,yes. For kegs and carboys I would summerise

Best method, fill as much with sanitizer and push out with CO2. Least amount of O2, uses the least amount of CO2, easy. Drink beer at your leisure as if other process are good it's as stable as you can get. (great if you, like me have 8+ taps)

OK method, purge keg a couple dozen times, transfer beer, purge headspace a couple dozen times. Similar amount of O2as 1, wastes a lot of CO2

Decent, transfer beer with minimum agitation, purge headspace a couple dozen times. More O2 than 1 and 2, saves gas over 2 but probably still uses more than 1

Open keg top and push CO2 into the bottom of the keg with lid open. Transfer beer with minimum agitation, purge headspace a couple dozen times. Pretty much same as 3 but wasted CO2

Not care, dump beer into keg, don't purge headspace, hook to CO2 and force carb. Come online and ask about the color change (darkening) of your light beer, the off flavors and change in taste while storing.

zoom out on that animal a bit...

How would you go about purging by displacement a vessel like a bucket?

Yooper · Mar 30, 2016

Tippsy-Turvy said:
How would you go about purging by displacement a vessel like a bucket?

While you can flood with co2 prior to filling, you can't really "purge" a bucket as the headspace is far too wide and it's not airtight like a keg. O2 can enter a bucket even through the water in the airlock, the plastic in the airlock, the plastic in a bucket, etc. That is one of the reasons why a secondary in a bucket is never recommended. Primary is fine, and then a keg or bottles to follow (or a carboy).

A keg is a perfect aging vessel- no light penetration, no oxygen allowed through airlocks or seams, etc.

Tippsy-Turvy · Mar 30, 2016

Got it, thank you.

Great tip on using the keg for a secondary! Will try displacement-purging with my keg in the future when I need a secondary for a full batch. For now, I'll just flood my vessels with CO2 (plastic bucket for bottling and wide mouth glass jars for split-batch secondaries).

jddevinn · Mar 30, 2016

Tippsy-Turvy said:
Got it, thank you.

Great tip on using the keg for a secondary! Will try displacement-purging with my keg in the future when I need a secondary for a full batch. For now, I'll just flood my vessels with CO2 (plastic bucket for bottling and wide mouth glass jars for split-batch secondaries).

With bottling and bottle conditioning, although it should be minimized, you have a little more leeway with oxygen uptake as the yeast will consume some of it with the priming sugar.

There are very very few beers that I feel need a "secondary" and these are things with "odd" addictions and long term bulk aging. I would skip the wide mouth glass jar secondaries unless you are split batching aditions or something.

Tippsy-Turvy · Mar 30, 2016

I would skip the wide mouth glass jar secondaries unless you are split batching aditions or something.

Exactly what I'm doing with my glass jar secondaries.

How does one purge a vessel with CO2?

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