CO2 Breakout, secondary fermentation and serving pressure

[yeastfromtheeast]

Hi all,

Just to share some discussion I had with some fellow dispensing vendors. This is about increasing the applied pressure to pack the lines to prevent CO2 breakout within the lines.
Some claim that for certain beer styles and also this is due to secondary fermentation happening within the keg which caused the increase in carbonation levels within the beer. Hence if they see some foaming in the line, just after the coupler, they see it as CO2 coming out of solution and increased the applied pressure to keep it back into solution. This happens more as the keg finishes. And with the increased applied pressure, you're inherently increasing the carbonation level in the beer. And this leads to a vicious cycle where the applied pressure can go all the way up to 30PSI. If the establishment has a gas blender, then they'll switch to the gas blend in order to increase the pressure, without adding the CO2 to the solution.

I'm not sure what to make of this increasing the applied pressure more than the system's resistance.
Never read about this from the BA's draught manual. Anybody has this experience?

First, I'm not sure what is the extent of secondary fermentation that is happening within the keg that requires an increase in applied pressure.

Second, I thought the gas regulator supposed to regulate the keg's internal pressure even though there is an increase in pressure due to secondary fermentation.

I thought its a just a balancing act. First you determine the applied pressure based on the CO2 vol and storage temperature. Then you calculate the total resistance with the length of lines, elevation etc. After they are balanced, then you're set for the long haul.

[djc]

Who are these ‘fellow dispensing vendors’? What they are describing isn’t correct, your understanding in the last paragraph is correct. They have other issues. To answer your regulator question, the regulator controls pressure coming from a low value to a high value, it cannot not vent pressure to reduce it from a value higher than its set point.

[mikejferrari]

Regulators will vent pressures higher than the set point. If the pressure in the outflow line is higher than the setting the excess pressure will bleed out of the weep hole. However, keg couplers have check valves that will prevent excess pressure in the keg from reaching the regulator so you don't end up with beer back-flowing into the regulator as it vents. All that doesn't matter in this scenario though, because kegs don't go through secondary fermentation unless the brewery really screwed up.

[yeastfromtheeast]

They are some folks who sells kegerators and dispensing equipment to home owners.

So what about this CO2 breakout?

And increasing the serving pressure by a few PSI to prevent CO2 breakout from higher carbonated beers like saisons, sours, hefes?

About secondary fermentation, not exactly secondary fermentation per se, but its more of "oh theres still yeast in the beer, so its continuing the fermentation process", so the carbonation level in the keg is increasing.

[mikejferrari]

Almost all commercial draft beer falls in the 2.5-2.7 v/v CO2 range (including saisons hefes, etc), so adjustments to the CO2 pressure are almost never necessary. If you do get a beer that has higher carbonation, then you would need to increase the applied pressure to keep the CO2 in solution and avoid breakout, but you would also need to compensate by adding restriction to your system to keep the flow rate consistent. That could be adding a flow-control faucet, or increasing the length of your beer line.

Fermentation should be complete when the beer goes into the kegs, so even if there is still yeast, it would have nothing to eat to produce more carbon dioxide. Even if the keg was filled too soon or there was some unintended bacterial contamination, fermentation wouldn't happen at cooler temps or would happen so slowly that it wouldn't create a noticeable increase in carbonation.

[yeastfromtheeast]

Almost all commercial draft beer falls in the 2.5-2.7 v/v CO2 range (including saisons hefes, etc), so adjustments to the CO2 pressure are almost never necessary. If you do get a beer that has higher carbonation, then you would need to increase the applied pressure to keep the CO2 in solution and avoid breakout, but you would also need to compensate by adding restriction to your system to keep the flow rate consistent. That could be adding a flow-control faucet, or increasing the length of your beer line.

Fermentation should be complete when the beer goes into the kegs, so even if there is still yeast, it would have nothing to eat to produce more carbon dioxide. Even if the keg was filled too soon or there was some unintended bacterial contamination, fermentation wouldn't happen at cooler temps or would happen so slowly that it wouldn't create a noticeable increase in carbonation.

Thanks for the reply. makes a lot of sense now.

Sidetrack to adding restriction. What do you think about MM's flow restrictor sticks? Whats your opinion of them?

[mikejferrari]

I love the MM restrictor sticks. Unless I'm building a keg box I use them exclusively for restriction over vinyl. You can use them with 1/4" barrier in a keg box too, but the tubing is prone to kinking when used in tight spaces.