[majorvices]

I often notice that the same draft beers consistently taste better at certain bars, and worse at certain other bars. I know for a fact that some of them disconnect the tap lines from their kegs overnight.

This is very interesting! Thanks for that info.

[Robert]

Now somebody out there is going to start thinking about the best way to purge a keezer.

[Stevie]

Do commercial breweries typically force carbonate their beer with non-fermentation produced CO2 (excluding bottle conditioned beers and RHGB compliant breweries)?

Almost every one I'm aware of does.

I’ve toured plenty of breweries, even smaller 15-30bbl, that capture their co2.

[The Beerery]

Thanks Tech, very great points often overlooked.  On a side note you stole our next topic we were going to touch on! Working on a series of these. As I said before at GBF(or maybe HBT, or wherever), I run special lines.  In my trials of the disconnection vs lines I saw no noticeable increase  one over the other when measuring via sulfite strips or sensory. 
However the best practice is certainly disconnect.  For those disconnecting make sure to purge your lines and connectors when you go to put them back on!  Otherwise you just injected basically pure o2 from the lines.


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[tommymorris]

The amount of oxygen introduced by non-pure CO2 is insignificant to the amount you get by leaving your keg connected to plastic liquid and gas tubing lines. This ingress will happen regardless of how pure your CO2 source is.

You can calculate the amount of atmospheric oxygen that will permeate through the plastic tubing membrane over a given period of time with this equation:

v = P * A * t * (p_1 - p_0) / d

Where

v = the volume of oxygen that diffuses across the membrane
P = the permeability coefficient of the membrane material
A = the area of the membrane
t = time
p_1 = the partial pressure of oxygen in the atmosphere
p_0 = the partial pressure of oxygen inside the tubing
d = the thickness of the membrane

Non-plasticized PVC tubing has a permeability coefficient of P = 0.045 x 10^-10 cm3 (STP)· cm /cm2 · s · cm-Hg (http://www.faybutler.com/pdf_files/HowHoseMaterialsAffectGas3.pdf). Unfortunately, the plasticized version that is required to make flexible tubing has a P that is about 18.75 times higher (http://www.tappi.org/content/events/07place/papers/fischer.pdf). So our P is .84375 x 10^-10 cm3 (STP)· cm /cm2 · s · cm-Hg.

A beverage line with 7/16” = 1.11125 cm OD and 3/16” = 0.47625 cm ID gives you a membrane thickness of 4/16” = 0.635 cm, which is our d. Let’s assume a 1 meter (= 100 cm) tube length which gives an A of pi * OD * 100 = 349.109 cm^2

A gas line with a 9/16” = 1.42875 cm OD and 5/16” ID also has a 4/16” thickness, so we can use the same d = 0.635 cm. The area will be larger: A = pi * 1.42875 * 100 = 448.855 cm^2

Let’s calculate how much oxygen ingress we would get per day. There are 24 * 60 * 60 = 86400 seconds in 1 day, so that’s our t.

p_1 is the partial pressure of oxygen in the atmosphere, which is 0.21 * 76 cm-Hg = 15.96 cm-Hg

p_0 can be assumed to be zero. If it wasn’t there wouldn’t be much point to this exercise in the first place.

Let’s plug it in:

Volume of oxygen that permeates across 1 meter of beer tubing per day:

v =  P * A * t * (p_1 - p_0) / d = 0.84375x10^-10 * 349.109 * 86400 * (15.96 - 0) / 0.635 = 0.06396 cm^3 (STP)

cm^3 (STP) is equivalent to the amount of oxygen that would fill one cubic centimeter at standard temperature and pressure. This happens to be 1.43 milligrams worth of oxygen.

Now let’s do the gas line:

v =  P * A * t * (p_1 - p_0) / d = 0.84375x10^-10 * 448.855 * 86400 * (15.96 - 0) / 0.635 = 0.08224 cm^3 (STP)

Converting the volumes to weights gives us

0.06396 * 1.43 = 0.09146 milligrams per day through the beer line
0.08224 * 1.43 = 0.11760 milligrams per day through the gas line

But wait. We only considered a 1 meter long length of beer tubing and a 1 meter long length of gas tubing. Most people use a lot more than that! 15 feet seems to be a standard length of beer tubing. Let’s assume 15 feet worth of gas tubing as well. 15 feet is 4.572 meters, so we have to multiply the numbers we found above by 4.572, giving us

0.09146 * 4.572 = 0.41815 milligrams per day through the beer line
0.11760 *4.572 = 0.53767 milligrams per day through the gas line

Alright, so that’s a grand total of 0.95582 milligrams of oxygen per day getting into our beer. Assuming we have 20 liters of beer sitting in the keg, that’s 0.047791 mg/l = 47.79 ppb per day, or 334.5 ppb per week.

There are better materials out there than plasticized PVC, but all of them will leak gas to a certain degree.

I often notice that the same draft beers consistently taste better at certain bars, and worse at certain other bars. I know for a fact that some of them disconnect the tap lines from their kegs overnight.

Won’t the oxygen that seeps in overnight just push into the keg the first time they reconnect to the keg and serve a beer?

PS. I guess this is an argument for drinking faster.

[techbrau]

Won’t the oxygen that seeps in overnight just push into the keg the first time they reconnect to the keg and serve a beer?

PS. I guess this is an argument for drinking faster.

Which is why you should blow CO2 through the lines before reconnecting them.

It is of course worth considering using a better tubing material, like Bev-Seal Ultra from Accuflex. Personally I would still not keep 30' worth of that line attached to my kegs permanently.

[hopfenundmalz]

The amount of oxygen introduced by non-pure CO2 is insignificant to the amount you get by leaving your keg connected to plastic liquid and gas tubing lines. This ingress will happen regardless of how pure your CO2 source is.

You can calculate the amount of atmospheric oxygen that will permeate through the plastic tubing membrane over a given period of time with this equation:

v = P * A * t * (p_1 - p_0) / d

Where

v = the volume of oxygen that diffuses across the membrane
P = the permeability coefficient of the membrane material
A = the area of the membrane
t = time
p_1 = the partial pressure of oxygen in the atmosphere
p_0 = the partial pressure of oxygen inside the tubing
d = the thickness of the membrane

Non-plasticized PVC tubing has a permeability coefficient of P = 0.045 x 10^-10 cm3 (STP)· cm /cm2 · s · cm-Hg (http://www.faybutler.com/pdf_files/HowHoseMaterialsAffectGas3.pdf). Unfortunately, the plasticized version that is required to make flexible tubing has a P that is about 18.75 times higher (http://www.tappi.org/content/events/07place/papers/fischer.pdf). So our P is .84375 x 10^-10 cm3 (STP)· cm /cm2 · s · cm-Hg.

A beverage line with 7/16” = 1.11125 cm OD and 3/16” = 0.47625 cm ID gives you a membrane thickness of 4/16” = 0.635 cm, which is our d. Let’s assume a 1 meter (= 100 cm) tube length which gives an A of pi * OD * 100 = 349.109 cm^2

A gas line with a 9/16” = 1.42875 cm OD and 5/16” ID also has a 4/16” thickness, so we can use the same d = 0.635 cm. The area will be larger: A = pi * 1.42875 * 100 = 448.855 cm^2

Let’s calculate how much oxygen ingress we would get per day. There are 24 * 60 * 60 = 86400 seconds in 1 day, so that’s our t.

p_1 is the partial pressure of oxygen in the atmosphere, which is 0.21 * 76 cm-Hg = 15.96 cm-Hg

p_0 can be assumed to be zero. If it wasn’t there wouldn’t be much point to this exercise in the first place.

Let’s plug it in:

Volume of oxygen that permeates across 1 meter of beer tubing per day:

v =  P * A * t * (p_1 - p_0) / d = 0.84375x10^-10 * 349.109 * 86400 * (15.96 - 0) / 0.635 = 0.06396 cm^3 (STP)

cm^3 (STP) is equivalent to the amount of oxygen that would fill one cubic centimeter at standard temperature and pressure. This happens to be 1.43 milligrams worth of oxygen.

Now let’s do the gas line:

v =  P * A * t * (p_1 - p_0) / d = 0.84375x10^-10 * 448.855 * 86400 * (15.96 - 0) / 0.635 = 0.08224 cm^3 (STP)

Converting the volumes to weights gives us

0.06396 * 1.43 = 0.09146 milligrams per day through the beer line
0.08224 * 1.43 = 0.11760 milligrams per day through the gas line

But wait. We only considered a 1 meter long length of beer tubing and a 1 meter long length of gas tubing. Most people use a lot more than that! 15 feet seems to be a standard length of beer tubing. Let’s assume 15 feet worth of gas tubing as well. 15 feet is 4.572 meters, so we have to multiply the numbers we found above by 4.572, giving us

0.09146 * 4.572 = 0.41815 milligrams per day through the beer line
0.11760 *4.572 = 0.53767 milligrams per day through the gas line

Alright, so that’s a grand total of 0.95582 milligrams of oxygen per day getting into our beer. Assuming we have 20 liters of beer sitting in the keg, that’s 0.047791 mg/l = 47.79 ppb per day, or 334.5 ppb per week.

There are better materials out there than plasticized PVC, but all of them will leak gas to a certain degree.

I often notice that the same draft beers consistently taste better at certain bars, and worse at certain other bars. I know for a fact that some of them disconnect the tap lines from their kegs overnight.

I’ve often wondered about the permeability of the lines. Thanks for running the numbers, and the disconnect advice.

[Robert]

But it seems to me that disconnecting and purgung, by my understanding of the numbers, only gives a SLIGHT delay to reaching "unacceptable" DO. I joked in an earlier reply about "purging a keezer," but anything short really doesn't pay off, does it?  I'm putting th is into the category of things you really can't -- practically, in the real world, for most of us -- do anything about.  And I see no point in worrying about things you can't do anything about. (Your therapist thanks you, though.  Boat payments.)  That's where I'm coming back around to on this whole subject. Nice to know, but focus your attention on things that will get you more  bang for the buck.  Just me.

[Big Monk]

But it seems to me that disconnecting and purgung, by my understanding of the numbers, only gives a SLIGHT delay to reaching "unacceptable" DO. I joked in an earlier reply about "purging a keezer," but anything short really doesn't pay off, does it?  I'm putting th is into the category of things you really can't -- practically, in the real world, for most of us -- do anything about.  And I see no point in worrying about things you can't do anything about. (Your therapist thanks you, though.  Boat payments.)  That's where I'm coming back around to on this whole subject. Nice to know, but focus your attention on things that will get you more  bang for the buck.  Just me.

Yes but when the buck is banged you need to look at these things!

That’s kind of what got us here. We were investigating these things because they are crucial for what we do but also had relevance for ALL, even if for some it’s not high on the list for everyone.

[The Beerery]

Actually we had a member semi put this to the test.  We are currently in production phase of that article. 


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[Robert]

But it seems to me that disconnecting and purgung, by my understanding of the numbers, only gives a SLIGHT delay to reaching "unacceptable" DO. I joked in an earlier reply about "purging a keezer," but anything short really doesn't pay off, does it?  I'm putting th is into the category of things you really can't -- practically, in the real world, for most of us -- do anything about.  And I see no point in worrying about things you can't do anything about. (Your therapist thanks you, though.  Boat payments.)  That's where I'm coming back around to on this whole subject. Nice to know, but focus your attention on things that will get you more  bang for the buck.  Just me.

Yes but when the buck is banged you need to look at these things!

That’s kind of what got us here. We were investigating these things because they are crucial for what we do but also had relevance for ALL, even if for some it’s not high on the list for everyone.

I agree these things are crucial to know about.  I just think this just emphasizes the need to tighten the screws on every part of your process you do have full control over, as insurance against the things you can't control. Some of which you still may not know about.  Sometimes the solution to a problem is not directly addressing it but rendering it less relevant.  Nothing's perfect.

[klickitat jim]

How much o2 uptake between spigot and glass? It freaks me out just imagining it

Not really, relax

[Robert]

How much o2 uptake between spigot and glass? It freaks me out just imagining it

Not really, relax

No, you just have to purge your taproom with sani.

[klickitat jim]

K

[Stevie]

How much o2 uptake between spigot and glass? It freaks me out just imagining it

Not really, relax

It’s enough of a concern that some bars pour Pilsner Urquell “wet.” The foam protects the beer from oxygen. It’s a real thing.

http://pilsnerurquell.com/us/article/classic-pilsner-pours-hladinka