How much pressure can fermentation build up?

[m3B.eer]

You are experiencing the warm carbed bottle of beer being opened. When pressure fermenting there is a lot more gas in the beer, when you release the pressure it wants to normalise. Hence it foams up like a warm bottle of beer being opened. This as you know is messy.
My experience and the video suggests it as well that the yeast keeps going. If I want yeast expression I don't use pressure or just a minimal amount to control the krausen ( I do use a fermentasaurus so I can see what's going on), then dial up the pressure towards the end of fermentation to get the carbonation built up.
If I don't want much yeast character ( lager ) or a recipe that says WLP 001 I tend to use opshaug kveik and set the dial to 15 psi from the off and then turn it up more to get the correct vols of CO2 towards the end of ferment ( this is temp related of course).
Beware that if you pressure ferment and then release the pressure to dry hop you can get a real boilover with gassy beer nucleated with dry hops. I have my hops in the fermenter on magnets ready to move them in at the time I want and don't open the fermenter for this. It's much less hassle.
You really do need a spunding valve for safety and control.

So you mean I could have left the keg closed without blowoff tube, and still be okay?
Using a sounding valve at a low control (how much?) would reduce Krausen?

So if you want to dry hop, you mean you already have your hops stuck on a magnet, but not in the wort, inside the fermenter? What If you want to dry-hop then without having those magnet? Slowly dialing down the pressure valve until it's safe to open?

 

[DuncB]

So you mean I could have left the keg closed without blowoff tube, and still be okay?

Maybe, but I'd favour a spunding valve or a blowoff tube or an airlock or just leave the Pressure relief valve open when first starting

Using a sounding valve at a low control (how much?) would reduce Krausen?

Often only need 5 psi to keep the krausen from coming out but some yeasts are really vigorous and it depends also on the headspace in your fermenter.



So if you want to dry hop, you mean you already have your hops stuck on a magnet, but not in the wort, inside the fermenter?
Yes

The magnets have been vacuum sealed in before sanitising and putting inside the hop bags.


What If you want to dry-hop then without having those magnet? Slowly dialing down the pressure valve until it's safe to open?

You can do that dial it down ( do it at a rate that doesn't have it all fizz up which might only take you ten minutes if you watch whilst you do it) open it up drop the hops in and then I tend to give a squirt of CO2 from a cylinder to stop it all fizzing up otherwise you can get all those hops you added stuck on the side of the fermenting vessel not in the wort / beer. Beware you have to be quick

see this video to give yourself an idea

I've added my replies into your text above.

 

[m3B.eer]

Thanks Dunc

 

[DuncB]

Thanks Dunc

No worries, there's a lot of pressure ferment stuff on that Dr Hans playlist.
ALso David Heath Homebrew has some advice as well.

 

[Brooothru]

No worries, there's a lot of pressure ferment stuff on that Dr Hans playlist.
ALso David Heath Homebrew has some advice as well.

Interesting topic (and video) about how dry hops provide millions of nucleation sites to liberate dissolved CO2 into a "beercano". I've gotten away from dry hopping in the last year or so, but recently have been working on a 'dry hop dropper' system to once again start using the process. I don't per se ferment under pressure but I do spund once fermentation slows to within ~5 points of final gravity. This results in about 1 bar/15 psig in the fermenter at ambient temperature ~65-70F/18-21C, which gives me 2.5-ish volumes at serving temperatures.

I'm not particularly interested in biotransformation of hops as a goal. Fine if it happens, but not what I'm seeking. I just want a way to get some dry hops into the fermenter that doesn't result in an eruption of CO2 violently coming out of solution. It seems like slowly depressurizing the fermenter defeats the purpose of spunding. The hop dropper design I've come up with allows the hop dropper to be pressurized equal to/greater than the 1 bar pressure in the fermenter, so am I correct to assume this would prevent the rapid dissolution of C02 when I open the butterfly valve between it and the fermenter?

Temperature obviously affects the solubility of the CO2. If I "soft crash" the spunded beer, does this mitigate the release of CO2? Once the hops are in the fermenter, does the CO2 tend to keep the hops in suspension and interfere with settling and clearing of the finished beer?

The end game of all this is a low oxygen process for stability and shelf-life that produces a naturally fermented clear beer that maintains its hop character for the 2~3 months it takes me to empty a keg. Without making a sticky mess. What are some 'best practices' that can get me to this goal?

 

[Homebrew Harry]

...Beer pipe bombs are hard to fuse.

Have you tried a blasting cap ?

 

[DuncB]

@Brooothru
I had a " beercano " early in my dry hopping pressure attempts and agree doesn't really seem much point working under pressure and then releasing it. I also only dry hop when necessary and most of my beers don't require it. But when needed I do the bag thing, however the various " sight glass " type dry hoppers are working at the same pressure as the beer or higher to blast the hops in. So I don't think there would be much nucleation issue occurring it's the pressure difference that makes the difference I think. Much like a beer can widget only works when the can is opened or the mintoe in a coke bottle, if you could drop that mintoe in with a sealed coke bottle I don't think you'd get a bottle bomb.

I haven't had a problem of getting the beer to clear when I've dry hopped and I do cold crash and drop out the trub / yeast and hop residue under pressure. I find the hops can still get out of the bags I use so they are in the cone. Some people advocate moving these sunk hops around so they don't just sit at the bottom using CO2 injection from the bottom, shaking or pumps to do this. I can't say whether it's necessary or not.

I don't " drop " the hop bag off the magnet but slide it down, this ensures the hops are submerged and then I can " waft " the hops in the bag around which does stir up the beer and can move any around in the cone.

My end game like yours is if I'm going to the trouble of dry hopping I don't want any oxygen near the beer, I purge the kegs using ferment pressure having filled them with starsan, purge any lines used for transfer and then run ferment gas thru them before disconnecting when they are at my target beer pressure.
I then cold crash and transfer using the pressure which is higher in the receiving kegs to run the transfer. So if the intended vols are 2.3 the pressure might need to be 22.55 at 18 celsius. So at the end of ferment I have 2 kegs at 22.55 psi and the fermenter. Your figure of 15psi and 18 celsius would give 1.8 vols on my calculator.
Disconnect the kegs and then cold crash the beer, the pressure drops say it's 4 celsius then it'll go down to well below 22.5 psi. Then when I transfer keg pressure equalises into the fermenter and the closed siphon pressure transfer occurs. If needs be I use the other keg gas reserve to keep the transfer going.
Picture of keg train below with spunding valve on the end of the train.

This does mean the beer that goes into the keg is at the correct vols straightaway and is clear ( though not if hazy!) , maturing/ development can occur in the keg fridge whilst it's being sampled.

It's all a fair bit of hassle but, for the only NEIPA I brewed double dry hopped and the above it really didn't oxidise over the few months it took to drink so it was worth it but stressful and the beer never ever got warm after the cold crash. Surprisingly I tried a bottle of it counterpressure filled from the fermenter that was hiding in the keg fridge months after the keg was finished and that hadn't oxidised either although not as vibrant as a first pour.

As a final thought on keeping oxygen out I'm not sure how much oxygen is between the hop particles making up a pellet, I hope with my having the hops in the fermenter any there is displaced by the only CO2 environment that is made by the yeast. It's probably not an issue though.

Given the smell of hops during a ferment and the dry hopping I'd love to catch that " hop gas " compress it and use it as my gas for serving the hoppy beers, but that is a bit of a challenge I reckon that I won't be taking on.
When my PID is fixed on my brew system I'll be at it again and a remake of the NEIPA is in the brew plan. Until then I'm on rations but should last out!