How much pressure is too much pressure?

[BarbarianBrewer]

I'm fermenting a Vienna Lager in a fermzilla 30L. After 3 days I attached a blow-tie spunding valve to start fermenting under pressure. A couple days later I check and saw the pressure gauge read zero. I discovered I didn't have the spunding valve seated properly so the Fermzilla was sealed up tight. I seated it properly but nothing. Tried the other blow-tie spunding valve. Same result. Then I noticed it wasn't reading zero it was off the scale! I pulled the PRV until kreuzen spit out the PRV. I got the pressure down to 10 psi.
So I have 3 questions:
1) Will the high pressure stress the yeast and impact the final beer? (The fermzilla has a 35 psi PRV so max pressure wasn't over that.)
2) Same question for the rapid drop in pressure to 10 psi
3) Does this qualify for the bi-annual pressure test?

 

[Dave Y]

1) Will the high pressure stress the yeast and impact the final beer? (The fermzilla has a 35 psi PRV so max pressure wasn't over that.)

ZOINKS! The answer is, possibly. What temp were you fermenting at?
I've been able to get lagers to finish at 15 psi for the entire length of fermentation ( and that was too much. Also a Vienna lager ). Pressure does inhibit -I suppose would be the best descriptor, normal fermentation speed a bit. @Bigbre04 might be able to shed some light on higher psi effects.

How has this fermentation progressed compared to previous ones?
Yeast was fresh & healthy?
Solid pitch?

For my Vienna lager, I had to depressurize it. So I get the keg on the tap and ... "hmm... that's a lot of foam". Next day, "hmm... that's still a lot of foam".
So I pulled the gas line from it and just did slow pours for a few days

Next time out I ramped it up, first to 5 psi, then 8-10 to finish out.

2) Same question for the rapid drop in pressure to 10 psi

No, I don't think this in and of itself will affect the yeast attenuation or create any other side effects.

3) Does this qualify for the bi-annual pressure test?

It does now.

 

[Bigbre04]

Damn man be careful.

My tanks are rated to 35psi, but they would probably hold 40 or 45psi a couple times. The biggest damaging thing is actually heat cycling. it can cause stress cracks to form on the welds.

I tried spunding at 18psi and that was one of the 3 batches out of 280 at this spot that i have dumped. I set my spunding valve to 10psi and the ramp it up to 15 at the same time i increase temp for the d rest.

pressure especially before the yeast gets rolling can cause some gross off flavors. BUT it is also very dependent on the yeast and the temp.

 

[BarbarianBrewer]

How has this fermentation progressed compared to previous ones?
Yeast was fresh & healthy?
Solid pitch?

I brew lagers infrequently so it's hard to make a comparison. But kreuzen before and after the high pressure incident looked and still looks good. Nice foamy 1/2" head. The yeast was Cellar Science German and was fairly young. I used 3 sachets for 6 gallons of 1.051 wort; so about 330 billion cells. The temps were at the max for that yeast, approximately 61-62°F (16C).

pressure especially before the yeast gets rolling can cause some gross off flavors. BUT it is also very dependent on the yeast and the temp.

I let it ferment without pressure for the first 3 days before pressurizing. I remember someone recommending that recently (don't remember who). So, a bit of good luck there. Thanks for that comment! It makes me feel a little better...in a "you could have screwed it up worse" kind of way...but, I'll take it!

 

[HighVoltageMan!]

The pressure itself is not the problem, it’s the dissolved co2 that causes problems. If it were that of pressure for extended periods of time I would worry, but a day or two is fine. The sudden drop in pressure shouldn’t be a problem, yeast are super tough when it comes to external physical pressure, they react more to dissolved co2 then pressure. So even if the pressure drops suddenly, it still takes time for the beer to degas.

 

[Bigbre04]

I brew lagers infrequently so it's hard to make a comparison. But kreuzen before and after the high pressure incident looked and still looks good. Nice foamy 1/2" head. The yeast was Cellar Science German and was fairly young. I used 3 sachets for 6 gallons of 1.051 wort; so about 330 billion cells. The temps were at the max for that yeast, approximately 61-62°F (16C).


I let it ferment without pressure for the first 3 days before pressurizing. I remember someone recommending that recently (don't remember who). So, a bit of good luck there. Thanks for that comment! It makes me feel a little better...in a "you could have screwed it up worse" kind of way...but, I'll take it!

yup i should have clarified. i leave the tank open for the first 24 hours(until there is active fermentation in the blow off bucket. then cap it and set the spunding valve to 10. when i am brewing a double(2 back to back brew days into one tank) i generally cap it when i leave work on the second brew. by this point there is usually plenty of activity to confirm that the yeast is rolling.