How are my Kegs getting Overcarbed?

[Premnasbiaculeatus]

I brew 15 gallon batches which I rack directly into 3 cornies at a time. I force carb at 30psi for six minutes. I put one keg in the kegerator if there is space and put the other two on the shelf.

When the first keg gets cold I vent it down to 0psi and then hook up my dispensing CO2 at 10 psi. This first of three usually pours fine.

The second is usually fairly overcarbed after a few to several weeks and the third after a couple to a few months is a foam grenade.

Recently I've been using a spunding valve on the older kegs in my pipeline to fix the carbonation issues they have, but I still can't figure where this excessive carbonation is coming from overtime.

I recently had a 3 month old keg of an abbey style ale that got up to 65psi.

Are my yeast waking back up in the keg? Are there remnant yeast in the keg more attenuative than the yeast I brewed with?

I'm thinking of pressure as a matter of force and surface area. The surface area of the keg should remain constant. The additional force must be do to an increasing volume of CO2. The tempeature stays pretty consistently between 68 and 72. Any other factor that could affect the solvency of beer? Its got to be yeast right?

 

[Horseflesh]

If kegs not hooked up to gas are increasing in pressure over time, that has got to be yeast activity. What are your FGs like?

Also, 30 psi for 6 minutes isn't going to dissolve much gas into the beer unless you are shaking that keg like a crying baby.

 

[SleepyCreekBrews]

...so you carbonate it at room temp?
My rule of thumb is, it you can't cool it, don't pressurize it because
it generally pressurizes on its own.

 

[pdxal]

Check final gravity at kegging and later on the over carbed beer after it has gone flat to tell if there is additional fermentation/attenuation in the keg.
Failing an infection in each of the kegs that get over carbonated, you are probably kegging before fermentation has finished.

 

[MaryB]

#1 Fermentation isn't finished
#2 infection

 

[Premnasbiaculeatus]

If kegs not hooked up to gas are increasing in pressure over time, that has got to be yeast activity. What are your FGs like?

Also, 30 psi for 6 minutes isn't going to dissolve much gas into the beer unless you are shaking that keg like a crying baby.

FG's are variable I can think of one recent high gravity IPA /DIPA that only got 63% attenuation, but for the most part the majority of my batches see attenuation % in the mid 70s. Is there some property of yeast behavior that makes them 'wake up' under pressure. Or is it just me stirring them up during kegging putting them back into suspension?

I do sit on the floor and rock the keg vigorously for the full 6 minutes. It works very well especially if I want to drink it same day.

...so you carbonate it at room temp?
My rule of thumb is, it you can't cool it, don't pressurize it because
it generally pressurizes on its own.

That would be ideal and is typically how I make seltzer, set the reg to 20 PSI and let it sit n the fridge for 4-5 days. With the spunding valve though I can make my beer a perfect 22PSI @ 68 degrees and know with confidence I have 2.5ish volumes of CO2. So room temperature is not a big deal. I just want to solve the mystery of my mysteriously rising CO2 pressure...

Check final gravity at kegging and later on the over carbed beer after it has gone flat to tell if there is additional fermentation/attenuation in the keg.
Failing an infection in each of the kegs that get over carbonated, you are probably kegging before fermentation has finished.

I guess I would have to be... right? It's hard for me to accept as weeks pass without activity or a gravity change in the fermenter, that it would start back up in the keg?

#1 Fermentation isn't finished
#2 infection

#1 seems like the most likely scenario, but it was at least halted at or near target FG, why is it coming back to life. Do yeast like being under pressure?
#2 I like this idea, but what is the infector? Wild yeast, a remnant yeast from beers long past, maybe something like CBC-1? I scour my kegs with hot water and rinse with starsan, but I'm not super thorough, I don't pull the tubes or ball locks

 

[Upthewazzu]

Is your regulator busted? 65PSI is way out of spec and I have a hard time believing a little leftover fermentation would be causing it to spike that high.

FWIW, I keg after the beer has been cold crashed, so the beer is always ~35° when it goes into the keg. From there, I force carb at 30PSI for 24 hours before backing down to ~9-12PSI.

 

[glugglug]

I don't pull the tubes or ball locks

Start pulling and cleaning these also. I bought a dip tube brush. Amazing what I first saw come out of the tubes.

 

[glugglug]

Start pulling and cleaning dip types and take apart and clean liquid and gas connections. I bought a dip tube brush. Very handy.

 

[doug293cz]

... With the spunding valve though I can make my beer a perfect 22PSI @ 68 degrees and know with confidence I have 2.5ish volumes of CO2. ...

What source tells you that 22 psi @ 68°F results in ~2.5 volumes? The most used chart says 22 psi @ 65°F gives 2.11 volumes, and the equation here says 22 psi @ 68°F gives 2.10 volumes.

Brew on

 

[Premnasbiaculeatus]

Is your regulator busted? 65PSI is way out of spec and I have a hard time believing a little leftover fermentation would be causing it to spike that high.

FWIW, I keg after the beer has been cold crashed, so the beer is always ~35° when it goes into the keg. From there, I force carb at 30PSI for 24 hours before backing down to ~9-12PSI.

I would need a bigger seperate fridge to cold crash three carboys (or a 15 gallon drum)at a time. My limitation force me to make ales at room temperatures.

I'm pretty sure the reg on my force carbing tank is ok, it's gauge matches the gauge reading on the spunding valve. This 65 PSI was on keg 3 of 3, after sitting on the shelf for a few months. 1 of 3 was perfect, and 2 of 3 was probably about 45 Psi after 5-6 weeks.

Start pulling and cleaning dip types and take apart and clean liquid and gas connections. I bought a dip tube brush. Very handy.

I might start doing this, but it's difficult because I'm lazy.

What source tells you that 22 psi @ 68°F results in ~2.5 volumes? The most used chart says 22 psi @ 65°F gives 2.11 volumes, and the equation here says 22 psi @ 68°F gives 2.10 volumes.

Brew on

A different chart... Hmm, looks like I'm in the greyzone. Maybe I should start doing 26-28 PSI for non stouts. Although, 22 has been working out and I super hate having to pour foam.

 

[Quaker]

The act of racking could be rousing and oxygenating the yeast, and it's likely fermenting further during the extra time at room temp while your first keg is served. I second the idea to pull a sample from an over carbonated keg, knock the CO2 out of it, and take a gravity reading. That'll definitively say if it's your kegging/carbing practice or fermentation process.

 

[Premnasbiaculeatus]

The act of racking could be rousing and oxygenating the yeast, and it's likely fermenting further during the extra time at room temp while your first keg is served. I second the idea to pull a sample from an over carbonated keg, knock the CO2 out of it, and take a gravity reading. That'll definitively say if it's your kegging/carbing practice or fermentation process.

I'm definitely going to do this, but I'll probably to dab some on the refractometer.

But you favor the stirring the yeast back into suspension theory above the foreign yeast in the keg's dip tube theory?

 

[doug293cz]

I'm definitely going to do this, but I'll probably to dab some on the refractometer.

...

Refracts don't read correctly when there is alcohol present in the liquid. There are calculators that will do a reasonable correction for the error, but if you don't have refract readings for your original FG, then your comparison will be flawed. If you used a hydrometer for your original FG reading, you need to use the same hydrometer for the new reading.

Brew on

 

[doug293cz]

...

A different chart... Hmm, looks like I'm in the greyzone. Maybe I should start doing 26-28 PSI for non stouts. Although, 22 has been working out and I super hate having to pour foam.

If it is a bad chart, then people need to know which chart it is so that they can avoid using it. I ask again: where did you find that chart?

And, if you are happy with the carb level you get at 22 lbs @ 68°, then it doesn't really matter what the actual CO2 volumes are. Just keep doing what you are doing to get your beer the way you like it.

Foaming during pours is most often due to lines that are too short, and/or to large of an inside diameter. Lines should be 3/16" ID with about 1 foot of line for every PSI of serving pressure. And serving pressure should be the chart pressure for the carb level and temp of the beer. If the serving pressure is either higher or lower than the chart pressure you will gain or loose carbonation respectively over time.

However, if your beer is severely over carbed, like your kegs 2 & 3, then you are likely to have foaming problems no matter what your line length or serving pressure. You need to fix the over carb issue. Over carbed beers often seem flat after a foamy pour since the foaming knocks most of the CO2 out of the beer.

Brew on

 

[MaryB]

I use BLC to clean the posts/dip tubes. I made up 2 adapter lines that run to a pump that pulls from a 5 gallon bucket, pumps up through both dip tubes into a keg suspended upside down over the 5 gallon bucket with a gallon of BLC in it. Cleans everything, liquid dip tube sprays onto bottom of keg and it flows down the walls. 15 minutes then rinse and done.

 

[Quaker]

But you favor the stirring the yeast back into suspension theory above the foreign yeast in the keg's dip tube theory?

I'm giving you the benefit of a doubt and trusting you'd have been able to identify off flavors by now if these were caused by an infection. Plus the attenuation levels mentioned above seemed on the low side with room for a little more fermentation to happen.

 

[Premnasbiaculeatus]

If it is a bad chart, then people need to know which chart it is so that they can avoid using it. I ask again: where did you find that chart?

And, if you are happy with the carb level you get at 22 lbs @ 68°, then it doesn't really matter what the actual CO2 volumes are. Just keep doing what you are doing to get your beer the way you like it.

Foaming during pours is most often due to lines that are too short, and/or to large of an inside diameter. Lines should be 3/16" ID with about 1 foot of line for every PSI of serving pressure. And serving pressure should be the chart pressure for the carb level and temp of the beer. If the serving pressure is either higher or lower than the chart pressure you will gain or loose carbonation respectively over time.

However, if your beer is severely over carbed, like your kegs 2 & 3, then you are likely to have foaming problems no matter what your line length or serving pressure. You need to fix the over carb issue. Over carbed beers often seem flat after a foamy pour since the foaming knocks most of the CO2 out of the beer.

Brew on

I made my own chart with excel, and guestimated my own formula based on the values in the mainstream chart that ends at 65 degrees. I obviously made an error, but I will use the equation you shared to fix it. Thanks for that.

My lines are 7' and 3/16"; my serving pressure is usually 10ish psi. Most of my kegs are coke kegs that were retrofitted to ball locks, but I also have a 6th keg and a pepsi keg which are slightly taller and foam worse because the are at the same or greater elevation than my door mounted faucets. Usually 22 psi @ 68, gets me to 8-10 PSI @ 38, without major foaming issues on my shorter wider kegs. I maintain 10 PSI for serving pressure.

I'm aware of the draw backs of over carbing. I've basically circumvented my overcarbing issue by spunding the older kegs in my production pipeline. My main interest is solving the mystery of where the excess carbonation is coming from.

I use BLC to clean the posts/dip tubes. I made up 2 adapter lines that run to a pump that pulls from a 5 gallon bucket, pumps up through both dip tubes into a keg suspended upside down over the 5 gallon bucket with a gallon of BLC in it. Cleans everything, liquid dip tube sprays onto bottom of keg and it flows down the walls. 15 minutes then rinse and done.

This is very clever, and I might give it a try. Couldn't I also fill a keg with BLC and just put CO2 on it to push the BLC through the dip tube and out of a picnic faucet?

I'm giving you the benefit of a doubt and trusting you'd have been able to identify off flavors by now if these were caused by an infection. Plus the attenuation levels mentioned above seemed on the low side with room for a little more fermentation to happen.

If infected it's not anything foul tasting, but I believe most ester/ fusel / phenol/ etc, gets produced during aerobic metabolism / early fermentation. I'm not sure an infection this late in fermentation would be easy to taste. Especially if I'm getting infected by brewing yeast. I think everyone's had that one 'Brett Porter' that was pitched with an S. cerevisiea strain, and then barrel aged with Brett, and when you taste it there is no perceivable contribution to the flavor from the Brett at all. and then the brewer is like "we didn't want it to be overpowering" and I'm all like "no, you didn't want it to be existent..." That said my palette is not the kind of princess that can feel a pea through a mattress. It could be possible, I can only taste infection if it's really infected.

At this point no one has been like "oh yeah, the exact same thing happens to me all the time". So, I'm on board with believing it's got to be additional fermentation. And at this point my next step is measuring the brix / plato on keg 3 of 3, to see if it's markedly lower than keg 1 of 3 was.

If it is, next time I'm going to stir up my yeast after it seems like fermentation is over, and see if fermentation restarts, if it doesn't and I keep getting over pressurization in the kegs, then I'll start cleaning my ball locks and dip tubes, and see if that changes anything.

Thanks everyone for your input.

 

[Premnasbiaculeatus]

Refracts don't read correctly when there is alcohol present in the liquid. There are calculators that will do a reasonable correction for the error, but if you don't have refract readings for your original FG, then your comparison will be flawed. If you used a hydrometer for your original FG reading, you need to use the same hydrometer for the new reading.

The most used chart says 22 psi @ 65°F gives 2.11 volumes, and the equation here says 22 psi @ 68°F gives 2.10 volumes.
Brew on

I only use a refract, and work in Brix and/or Plato, original FG would be called OG, wouldn't it? Or do you mean the FG on keg 1 of 3 before I drank it? Regardless, I measured that(and everything else) with my refract.

I cannot make AJdelange's equation work, doing it by hand or putting it into excel. How did you end up with 2.1? It give's me 3.6... Using his RMS and polynomial corrections gives me other wildly different values. Are these equations using a european or asian form of order of operations? Because, PEMDAS isn't working... Only the differential equations get me somewhat close if I subsequently convert Atmospheres to PSI ,moles to pounds and Kelvins to farenheit. That takes forever, but hat gives me 2.14 (brewer's friend gives me almost the same thing so eventually I just started testing everything with the BF calculator)... Anyway, I made a new chart that algebraically infers a palabraic slope using temperature and pressure as X and Y respectively. Between 1 and 65 degrees it's true to the popular chart within + or - 5%. Beyond 65 degress... I have no idea.But for 22@68 I get 1.88. However, the most popular chart itself doesn't seem to conform to henry's law as far as I can tell, and I have no idea what math / physics created it or if it's accurate or not...

I'm just going to stick with 22psi @ 68 and not worry about quantifying my volumes for now... The chart I made is below. If anyone wants to play with, fix, improve, criticize , mock, etc.. Feel free to have some fun.



http://mikejewel.webs.com/MJCarbonation.xlsx

 

[doug293cz]

I only use a refract, and work in Brix and/or Plato, original FG would be called OG, wouldn't it? Or do you mean the FG on keg 1 of 3 before I drank it? Regardless, I measured that(and everything else) with my refract.

I cannot make AJdelange's equation work, doing it by hand or putting it into excel. How did you end up with 2.1? It give's me 3.6... Using his RMS and polynomial corrections gives me other wildly different values. Are these equations using a european or asian form of order of operations? Because, PEMDAS isn't working... Only the differential equations get me somewhat close if I subsequently convert Atmospheres to PSI ,moles to pounds and Kelvins to farenheit. That takes forever, but hat gives me 2.14 (brewer's friend gives me almost the same thing so eventually I just started testing everything with the BF calculator)... Anyway, I made a new chart that algebraically infers a palabraic slope using temperature and pressure as X and Y respectively. Between 1 and 65 degrees it's true to the popular chart within + or - 5%. Beyond 65 degress... I have no idea.But for 22@68 I get 1.88. However, the most popular chart itself doesn't seem to conform to henry's law as far as I can tell, and I have no idea what math / physics created it or if it's accurate or not...

I'm just going to stick with 22psi @ 68 and not worry about quantifying my volumes for now... The chart I made is below. If anyone wants to play with, fix, improve, criticize , mock, etc.. Feel free to have some fun.



http://mikejewel.webs.com/MJCarbonation.xlsx

OG always means SG into the fermenter prior to yeast pitch. By original FG, I meant the FG reading you took at the time of kegging. Later readings should be the same if fermentation was complete at the time of kegging. If the later readings are lower, then that is evidence of additional fermentation occurring after kegging. Could be from original yeast and residual fermentable sugar, or a tramp microbe that is fermenting things the original yeast can't.

Unfortunately the AJdelange post I linked to earlier had a typo in the equation (I have since corrected the typo.) The reference for the equation is section 2.1 of http://www.wetnewf.org/pdfs/Brewing_articles/CO2 Volumes.pdf The correct factor in the equation is 0.01821, not 0.0181 Here's the (correctred) equation as given by AJ in the previously linked post:

V = (P + 14.695) * (0.01821 + 0.090115 * exp( (32 - T) / 43.11) ) - 0.003342​

I don't know if the equation error was enough to explain your results or not.

In the above equation "P" is the gauge pressure. If using absolute pressure (i.e. the CO2 partial pressure), then the 14.695 should not be added to "P". So the equation becomes:

V = P[abs] * (0.01821 + 0.090115 * exp( (32 - T) / 43.11) ) - 0.003342​

In a carbonation calculator you know "V" and "T" and want to solve for P[gauge]. If you solve the equation above for "P" you get:

P[abs] = (V + 0.003342) / (0.01821 + 0.090115 * exp( (32 - T) / 43.11) ), and
P[gauge] = -14.695 + (V + 0.003342) / (0.01821 + 0.090115 * exp( (32 - T) / 43.11) )​

Here's my force carbonation spreadsheet that implements the AJ equation, with an added twist of a correction for local barometric pressure.

View attachment Carbonation Pressure Calculator-2.xlsx.xml

The .xml file extension is a dummy, and needs to be deleted to open the file. The calculator part works with the P[abs} form of the equation, but the table is built from the unmodified AJ form.

For reference here is the "official" ASBC carbonation chart to which AJ's equation was fit.

View attachment Carbonation_Volumes_Pressure_Temperature_Chart.pdf

Brew on

 

[Premnasbiaculeatus]

OG always means SG into the fermenter prior to yeast pitch. By original FG, I meant the FG reading you took at the time of kegging. Later readings should be the same if fermentation was complete at the time of kegging. If the later readings are lower, then that is evidence of additional fermentation occurring after kegging. Could be from original yeast and residual fermentable sugar, or a tramp microbe that is fermenting things the original yeast can't.

Unfortunately the AJdelange post I linked to earlier had a typo in the equation (I have since corrected the typo.) The reference for the equation is section 2.1 of http://www.wetnewf.org/pdfs/Brewing_articles/CO2 Volumes.pdf The correct factor in the equation is 0.01821, not 0.0181 Here's the (correctred) equation as given by AJ in the previously linked post:

V = (P + 14.695) * (0.01821 + 0.090115 * exp( (32 - T) / 43.11) ) - 0.003342​

I don't know if the equation error was enough to explain your results or not.

In the above equation "P" is the gauge pressure. If using absolute pressure (i.e. the CO2 partial pressure), then the 14.695 should not be added to "P". So the equation becomes:

V = P[abs] * (0.01821 + 0.090115 * exp( (32 - T) / 43.11) ) - 0.003342​

In a carbonation calculator you know "V" and "T" and want to solve for P[gauge]. If you solve the equation above for "P" you get:

P[abs] = (V + 0.003342) / (0.01821 + 0.090115 * exp( (32 - T) / 43.11) ), and
P[gauge] = -14.695 + (V + 0.003342) / (0.01821 + 0.090115 * exp( (32 - T) / 43.11) )​

Here's my force carbonation spreadsheet that implements the AJ equation, with an added twist of a correction for local barometric pressure.

View attachment 416245

The .xml file extension is a dummy, and needs to be deleted to open the file. The calculator part works with the P[abs} form of the equation, but the table is built from the unmodified AJ form.

For reference here is the "official" ASBC carbonation chart to which AJ's equation was fit.

View attachment 416244

Brew on

Awesome!!! Thank you very much!

The equation works fine with either .0181 or .01821. I'm an idiot who didn't know what exponential looked like in a arithmetic equation. I was interpreting *EXP to mean ^. A couple times I even tried putting '*^' into excel. It totally make sense that the chart would be logarithmic. I kept trying to make this work by moving and adding captions ' =SUM(B1+14.695)*(0.0181+0.090115^(-(32-A2)/43.11))-0.00334'(B1 was P A2 was T. Obviously, I was very confused... But now I got it(now that you did all the work). If I keep posting problems like this on HBT I might eventually be as smart as I used to be in college.

Anyway thank you very much for the chart, I imagine it will be much more reliable than the one I cobbled together. To make it similar to the 'most popular chart' I added custom formatting to it for styles by color, and added carbonation ranges for Soda and sparkling mead wine and root beer.

Thanks again! This will be a great tool!

 

[MaryB]

I used to add a gallon of BLC to the keg, roll it around for awhile to make sure all the sides got clean, stood it upside down for 15 minutes to clean the top, then pumped it through the tap it came from with CO2 but why waste gas? Alternative is a small air compressor at 15psi, I have used my air brush compressor with the oil and water trap.

I made my own chart with excel, and guestimated my own formula based on the values in the mainstream chart that ends at 65 degrees. I obviously made an error, but I will use the equation you shared to fix it. Thanks for that.

My lines are 7' and 3/16"; my serving pressure is usually 10ish psi. Most of my kegs are coke kegs that were retrofitted to ball locks, but I also have a 6th keg and a pepsi keg which are slightly taller and foam worse because the are at the same or greater elevation than my door mounted faucets. Usually 22 psi @ 68, gets me to 8-10 PSI @ 38, without major foaming issues on my shorter wider kegs. I maintain 10 PSI for serving pressure.

I'm aware of the draw backs of over carbing. I've basically circumvented my overcarbing issue by spunding the older kegs in my production pipeline. My main interest is solving the mystery of where the excess carbonation is coming from.


This is very clever, and I might give it a try. Couldn't I also fill a keg with BLC and just put CO2 on it to push the BLC through the dip tube and out of a picnic faucet?



If infected it's not anything foul tasting, but I believe most ester/ fusel / phenol/ etc, gets produced during aerobic metabolism / early fermentation. I'm not sure an infection this late in fermentation would be easy to taste. Especially if I'm getting infected by brewing yeast. I think everyone's had that one 'Brett Porter' that was pitched with an S. cerevisiea strain, and then barrel aged with Brett, and when you taste it there is no perceivable contribution to the flavor from the Brett at all. and then the brewer is like "we didn't want it to be overpowering" and I'm all like "no, you didn't want it to be existent..." That said my palette is not the kind of princess that can feel a pea through a mattress. It could be possible, I can only taste infection if it's really infected.

At this point no one has been like "oh yeah, the exact same thing happens to me all the time". So, I'm on board with believing it's got to be additional fermentation. And at this point my next step is measuring the brix / plato on keg 3 of 3, to see if it's markedly lower than keg 1 of 3 was.

If it is, next time I'm going to stir up my yeast after it seems like fermentation is over, and see if fermentation restarts, if it doesn't and I keep getting over pressurization in the kegs, then I'll start cleaning my ball locks and dip tubes, and see if that changes anything.

Thanks everyone for your input.

 

[BrewieVessi]

Awesome!!! Thank you very much!

The equation works fine with either .0181 or .01821. I'm an idiot who didn't know what exponential looked like in a arithmetic equation. I was interpreting *EXP to mean ^. A couple times I even tried putting '*^' into excel. It totally make sense that the chart would be logarithmic. I kept trying to make this work by moving and adding captions ' =SUM(B1+14.695)*(0.0181+0.090115^(-(32-A2)/43.11))-0.00334'(B1 was P A2 was T. Obviously, I was very confused... But now I got it(now that you did all the work). If I keep posting problems like this on HBT I might eventually be as smart as I used to be in college.

Anyway thank you very much for the chart, I imagine it will be much more reliable than the one I cobbled together. To make it similar to the 'most popular chart' I added custom formatting to it for styles by color, and added carbonation ranges for Soda and sparkling mead wine and root beer.

Thanks again! This will be a great tool!

This is SUPER helpful, as it goes to temps as high as 80F which is great for fermenting under pressure. I use Vessi and when you first start out fermenting, it's usually around room room temp for the first day. Need to know what PSI to dial in pressure relief valve and this will tell me. Thank you!

 

[Jako]

Start pulling and cleaning these also. I bought a dip tube brush. Amazing what I first saw come out of the tubes.

I think this recently caused issues for me. This and cleaning keg lines and tap after each batch is finished. Before I would just hook the next keg up and let it rip and clean every other keg.