Fermentation for 3 weeks (ale)? 1st time this long. Under pressure. Questions

[Panderson1]

This is odd for me. I use a Firmzilla55L 11 gal batches. Probably 40 batches in this same fermenter.

Mostly IPA with same gravity numbers. Most beers finish by 7-12 days.

Once visual fermentation seems to look dying down I add a spunding valve and add natural pressure (for cold crashing later). This one has been building up 10 psi every 12 hours from about day 12 to day 24. I should have taken a picture but the beer looks nice and flat. No signs of infection, but I have never had one before. Maybe i should taste it but I don't know what to taste for.

This was a harvested slurry (white labs english ale 2nd gen). It was a little slow to start. Around 30 hours. But it took off nicely and seemed to start finishing off after 3-4 days. But it keeps building pressure 2 weeks after initial fermentation seemed to finish off (visually). I haven't taken i reading. I guess I should build it keeps building pressure each day. Never had anything like this happen before.

 

[VikeMan]

This one has been building up 10 psi every 12 hours from about day 12 to day 24.

So the pressure is at 240 PSI? That doesn't seem likely. What pressure is actually on the spunding valve's gauge?

Or do you mean you've been letting the pressure build to 10 PSI, then relieving the pressure and starting over? That's not how spunding works.

My advice is to set your spunding valve to the pressure needed to get the volumes of CO2 you want at equilibrium, given the beer's temperature. But at this point, you may not ever reach that pressure, if you've been relieving it.

And, stop guessing about fermentation and get a gravity sample. After measuring the gravity, taste the sample and see if anything seems off. My guess is that your fermentation is finished.

 

[Panderson1]

So the pressure is at 240 PSI? That doesn't seem likely. What pressure is actually on the spunding valve's gauge?

Or do you mean you've been letting the pressure build to 10 PSI, then relieving the pressure and starting over? That's not how spunding works.

My advice is to set your spunding valve to the pressure needed to get the volumes of CO2 you want at equilibrium, given the beer's temperature. But at this point, you may not ever reach that pressure, if you've been relieving it.

And, stop guessing about fermentation and get a gravity sample. After measuring the gravity, taste the sample and see if anything seems off. My guess is that your fermentation is finished.

Yeah, sorry. I have been relieving the pressure. At one point it almost got to 35psi. I don't want it to explode. Normally (in the past) the pressure only builds up to 10-15 then no more. Then i let it sit a few days before cold crashing -- this time not the case -- it's been 3 weeks.

If fermentation has completed, what would explain the build up in pressure? Especially so fast at 10 PSI every 12 hours -- ongoing for 2 weeks AFTER krausen has fallen

 

[marc1]

Yeah, sorry. I have been relieving the pressure. At one point it almost got to 35psi. I don't want it to explode. Normally (in the past) the pressure only builds up to 10-15 then no more. Then i let it sit a few days before cold crashing -- this time not the case -- it's been 3 weeks.

If fermentation has completed, what would explain the build up in pressure? Especially so fast at 10 PSI every 12 hours -- ongoing for 2 weeks AFTER krausen has fallen

If you set the spunding vale to 15PSI, then you shouldn't have to be doing any manual relief. That's the whole purpose of a spunding valve. Is yours defective?

 

[VikeMan]

Yeah, sorry. I have been relieving the pressure. At one point it almost got to 35psi. I don't want it to explode. Normally (in the past) the pressure only builds up to 10-15 then no more. Then i let it sit a few days before cold crashing -- this time not the case -- it's been 3 weeks.

The whole idea with spunding is to set the valve to the pressure you want to build to, after which pressure in excess of that setting is automatically released. That's what spunding is. If your previous batches only got as high as 10-15 PSI, either that's what you had the valve set to for those batches -or- by the time you began spunding those batches there was only enough sugar left to reach 10-15 PSI.

If fermentation has completed, what would explain the build up in pressure? Especially so fast at 10 PSI every 12 hours -- ongoing for 2 weeks AFTER krausen has fallen

How do you know fermentation had completed? Did you take some gravity readings that you didn't mention?

 

[Panderson1]

The whole idea with spunding is to set the valve to the pressure you want to build to, after which pressure in excess of that setting is automatically released. That's what spunding is. If your previous batches only got as high as 10-15 PSI, either that's what you had the valve set to for those batches -or- by the time you began spunding those batches there was only enough sugar left to reach 10-15 PSI.



How do you know fermentation had completed? Did you take some gravity readings that you didn't mention?

Yes. I believe my spunding valve is defective. I could never seem to get it to work properly so I just keep an eye on it while completely closed off. The gauge matches up with my keg regulator. I should order a new one no doubt.

And I don't know about fermentation. I was just asking "If" it is complete (hypothetically) what could cause a build up in pressure? That's all

 

[marc1]

Yes. I believe my spunding valve is defective. I could never seem to get it to work properly so I just keep an eye on it while completely closed off. The gauge matches up with my keg regulator. I should order a new one no doubt.

And I don't know about fermentation. I was just asking "If" it is complete (hypothetically) what could cause a build up in pressure? That's all

If there is pressure building up repeatedly, then something is fermenting.

 

[Panderson1]

If there is pressure building up repeatedly, then something is fermenting.

Kinda my thoughts on why bother checking. But i'm also lazy. It's all new and bizarre to me. Never had this happen

 

[marc1]

Kinda my thoughts on why bother checking. But i'm also lazy. It's all new and bizarre to me. Never had this happen

If your spunding valve worked, it wouldn't matter. I had one of the all brass ones and it was terrible. The Kegland one works great for me.

 

[Panderson1]

If your spunding valve worked, it wouldn't matter. I had one of the all brass ones and it was terrible. The Kegland one works great for me.

Yeah, I ordered the kegland one but I dropped it pretty hard on accident before ever using it. I must have busted something. I can't set a threshold. Tried it like 20 times then just adjusted to my own ways. It's either on or off basically

 

[odie]

If fermentation has completed, what would explain the build up in pressure? Especially so fast at 10 PSI every 12 hours -- ongoing for 2 weeks AFTER krausen has fallen

Simple...your beer has already finished fermenting and is fully carbed to the spunding valve set point. Every time you vent and release the headspace pressure, the carbed beer gasses off into that now zero psi headspace until it reaches equilibrium with the beer. Every time you release it it will gas off again until it re-pressurizes the headspace.

 

[balrog]

I was thinking along the same lines @odie, but it would be diminishing "rebuild" of pressure.
If it was still creating CO2 and built pressure to 35psi, there would be lots of dissolved CO2 in the beer. Releasing the pressure on the headspace would allow new equilibrium as dissolved CO2 under less headspace pressure would come out of solution. But without new CO2 created, the new equilibrium would be less than 35. I'm sure @doug293cz could calculate it, but it would be less. Then the next time would be even less.

But if CO2 is still being generated, and it goes to 35 daily, I have to think something is still generating CO2.

 

[odie]

I don't think any new CO2 is being generated at this point. Sounds like the OP spunding valve is set way above 10psi and the beer is highly carbed.

It's just gassing off at a rate so that the headspace rises to around 10 psi after several hours at which point he is dumping it to zero and then the cycle starts over. Each cycle, yes it would build a little less, but not enough less to be obvious over a single cycle.

It will be several cycles until it drops to around 10psi and holds there.

 

[doug293cz]

I was thinking along the same lines @odie, but it would be diminishing "rebuild" of pressure.
If it was still creating CO2 and built pressure to 35psi, there would be lots of dissolved CO2 in the beer. Releasing the pressure on the headspace would allow new equilibrium as dissolved CO2 under less headspace pressure would come out of solution. But without new CO2 created, the new equilibrium would be less than 35. I'm sure @doug293cz could calculate it, but it would be less. Then the next time would be even less.

But if CO2 is still being generated, and it goes to 35 daily, I have to think something is still generating CO2.

This analysis is correct. If it was initially in equilibrium at 35 psi, and you then vented, and started to repeat the venting every time it got to 10 psi, you could do this many times before the pressure would no longer rebuild to 10 psi. Basically you have to drop the carbonation level of the beer to where it would be in equilibrium at 10 psi, and then venting cycles after that would no longer rebuild to 10 psi.

It is possible to calculate this, but I'm not sure it's worth the trouble. If people are really interested in a quantitative example of what I have said above, I can do the math.

Brew on