Cold crash Unitank

[Qhrumphf]

Why do you dump before dry hopping if you don't intend to harvest the yeast?.. Or am I just over thinking your "and/or"

Hops seem to be cleaner and more expressive. I assume some of the hops are getting bound up in yeast as they settle. Not sure why, just my experience. Also less autolysis risk when the beer no longer needs to be on the yeast. Definitely easier to dump dry hops later on though without all the yeast continuing to sit and compact.

Not looking to harvest or age. I just want the beer carb as soon as possible. I crashed down from 68 to 60 and just did the first dumb but was pretty much all hops. I will lower to 55 or 50 and do another one. But now it looks like my carb stone is clogged as I have the co2 hooked up to 8psi but only see 4psi in the tank.

likely an issue of the "wetting pressure" of your stone. The stone adds enough resistance to the gas that it may not be able to push any more in. You could try pushing gas through your stone while under atmospheric pressure. Start at near zero PSI with your stone submerged in star san, and slowly raise the pressure until you start seeing bubbles. Should give you an idea of the wetting pressure of your stone (though I imagine in a pressurized vessel it's probably more complicated than that)

 

[Tonypr24]

Hops seem to be cleaner and more expressive. I assume some of the hops are getting bound up in yeast as they settle. Not sure why, just my experience. Also less autolysis risk when the beer no longer needs to be on the yeast. Definitely easier to dump dry hops later on though without all the yeast continuing to sit and compact.

likely an issue of the "wetting pressure" of your stone. The stone adds enough resistance to the gas that it may not be able to push any more in. You could try pushing gas through your stone while under atmospheric pressure. Start at near zero PSI with your stone submerged in star san, and slowly raise the pressure until you start seeing bubbles. Should give you an idea of the wetting pressure of your stone (though I imagine in a pressurized vessel it's probably more complicated than that)

Thank you. I was not aware of wetting pressure. I just read a whole article about it but unfortunately i cant just take out the stone now while I have it the tank. I might have to move the co2 to the blow off valve.

 

[CodeSection]

Not looking to harvest or age. I just want the beer carb as soon as possible. I crashed down from 68 to 60 and just did the first dumb but was pretty much all hops. I will lower to 55 or 50 and do another one. But now it looks like my carb stone is clogged as I have the co2 hooked up to 8psi but only see 4psi in the tank.

What is your wetting pressure of your carb stone? I seriously doubt your carb stone is clog. More than likely, your carb stone's wetting pressure is roughly 4 psi. Therefore, it will take 4 psi just to get the CO2 out. Thus, if the carb stone's wetting pressure was 4 psi and your CO2 tank regulator is showing 8 psi, then your tank would show roughly 4 psi (8 psi - 4 psi wetting pressure).

Edit: Ahh, just noticed Ohrumpf's post after I posted mine. I shouldn't have waited to post.....oh well.

 

[CodeSection]

Thank you. I was not aware of wetting pressure. I just read a whole article about it but unfortunately i cant just take out the stone now while I have it the tank. I might have to move the co2 to the blow off valve.

I wouldn't worry about it as I'm guessing the wetting pressure is roughly 4 psi since that is what you are describing. You can adjust the CO2 tank regulator up and see if the tank pressure increases by the same amount and still shows a 4 psi difference between the two.

Later when you are disassembling things to clean, you can test out your carb stone if you want to.

Here is a response from SSB when I asked them back in January 2020 about their carb stone wetting pressure since they had no information on their website as other manufacturers do.....

"Ss JC (Ss Brewtech)

Jan 31, 11:06 AM PST

Hey,

Thanks for reaching out. The diffusion/carbonation/oxygen stones are 0.5micron pores and the wetting pressure varies from stone to stone but is usually in the range of 2-5psi. You can test this by placing your stone in a jar of water and slowly increasing pressure.
Cheers!
JC"

 

[Tonypr24]

I should have mentioned that the 4psi in the tank was already there from when I closed the blow off valve when I had a few points left of fermentation and had 6 psi in the tank. I then dumped some yeast and lost 2 psi now in have 4 left. The co2 has done nothing to be honest. I set up the co2 to 8psi and I see nothing going up in the tank for psi. That's why I'm thinking its clogged.

 

[Qhrumphf]

Stone wetting pressure can vary and some could be as high as 8psi (meaning you'd have to put more than 12psi into the stone to bring your fermenter above 4 psi). If you still have fermentation happening, don't apply more pressure. Wait to do that until it's done. If you were 4 pts above your FG, that can put you up to the operating limit of your unitank without any additional CO2 being added.

Depending on your yeast, you could soft crash it now to the low 50s and hold it there until you know it's fully done. Some yeasts will drop prematurely or not clean up after themselves as well if you do that though (namely English yeasts).

At that point, put 15 PSI onto your stone and see what happens.

 

[Brooothru]

Show your work.

Assume room temperature 65F. SG has dropped to within 5 points of predicted Final Gravity. A spunding valve is attached to the fermenter, set to release at 15 psig. Fermentation continues at 65F and pressure rises inside the sealed fermenter until reaching 15 psig when the spunding valve begins to vent CO2, maintaining the internal 15 psig pressure. Due to the increased partial pressure within the fermenter, CO2 is forced into solution in the beer until the liquid becomes saturated. The chart above indicates that the volume of CO2 contained in the liquid is 1.70 volumes.

At Final Gravity when equilibrium is reached, the saturated liquid (beer) is transferred under 15 psig pressure to a CO2 purged, sealed keg via the black Liquid Out post. A keg mounted spunding valve is placed on the gray Gas In post, with a release pressure set to 'something less' than 15 psig. 65F beer (saturated with CO2 @15 psi) flows into the keg. When the transfer is complete, we nominally have 5 gallons of beer at 65F at 15 psig that contains 1.70 volumes of CO2. There are variables of course, including the dimensions and geometry of "sending" fermenter and the "receiving" keg, the pressure differential between the two of the vessels, the headspace between the beer column and the keg lid, the presence of any residual sugar or non-dormant yeast that slipped from the fermenter to the keg, etc., etc., ad infinitum. As you said, the math is complicated and is above my pay grade as well. But I think we can agree that we have at least, nominally, 65F beer saturated with CO2 amounting to 1.70 volumes under 15 psi differential pressure in a sealed keg.

Now we change one variable in the equation. We place the sealed keg in a 38F refrigerator to let it condition for a week or two, even though temperature equilibrium will be reached much sooner. After two weeks we measure the pressure in the keg and find that it has fallen to 11 psig. Does that mean that 4 psi worth of CO2 escaped? No. It went into solution under 15 psig pressure until saturation and equilibration were achieved at 11 psig. The chart above indicates that the volume of saturated CO2 in the beer at that temperature and pressure is 2.48 volumes. The "additional" CO2 wasn't created in a vacuum. It was absorbed into the liquid under pressure from gas in the headspace in a sealed vessel when the temperature was reduced and the liquid was able to hold more of the gas before a new saturation level was reached.

So when I switch the empty keg in my kegerator with a freshly conditioned or lagered keg from my beer fridge, it's usually at 11 psi, which coincidentally is the regulator pressure set point for my kegerator, balanced to deliver beer to the tap at the proper level of carbonation. The kegerator is also set to 38F. The beer is always properly carbonated, even on the first pull.

When I first started kegging nearly 20 years ago (Gawd, am I really getting this old?) I used force carbonation rather than bottle priming. For the longest time I used the "shake and bake/crash and carb" method to get the fizz in. The results were usually random and mixed, but usually over- or under-carbed so I switched to "set and forget" process which took longer but provided consistent, repeatable results. If I wanted an IPA carbonated to 2.5 volumes with a rocky 1½" head that lingered like Belgian Lace leaving notches on the side of the glass marking each sip, I'd hook up the uncarbed keg to 11 psi CO2 and put it in the beer fridge for a week or so. Now I just cut out the middleman, as well as an extra week or two of time, by spunding and cold crashing in a unitank before conditioning or lagering.

What I've outlined is the process I have used for at least my last 10-12 brew sessions since I started using a unitank. My experience has been repeatable and is verifiable based on my brew notes. I'll concede that I don't have scientifically measured empirical data able to pass peer reviewed scrutiny, nor the background or credentials to claim unassailable knowledge of the underlying physics, but these are things I've observed and recorded using the rudimentary tools at my disposal. But that's kinda' the whole reason home brewing exists: to gain more insight, share ideas, improve our methods and brew better (no, GREAT!) beer. Cheers!

Brooo Brother
An Old Dog always wanting and willing to learn New Tricks

 

[TheMadKing]

Now we change one variable in the equation. We place the sealed keg in a 38F refrigerator to let it condition for a week or two, even though temperature equilibrium will be reached much sooner. After two weeks we measure the pressure in the keg and find that it has fallen to 11 psig. Does that mean that 4 psi worth of CO2 escaped? No. It went into solution under 15 psig pressure until saturation and equilibration were achieved at 11 psig. The chart above indicates that the volume of saturated CO2 in the beer at that temperature and pressure is 2.48 volumes.

Brooo Brother
An Old Dog always wanting and willing to learn New Tricks

I think I understand the confusion here.

What you are measuring is the pressure in the headspace of the keg which is = to x value for a given equilibrium and a given amount of CO2 dissolved into the beer. but your carbonation level is determined by volumes dissolved into solution. A volume is the amount of CO2 that will pressurize a vacuum evacuated vessel to 1 atmosphere - no matter what size that vessel is BUT when we are talking about volumes of CO2 in solution, the "vessel" is the liquid, not the keg.

So as temperature drops, the volume absorbed into the liquid increased while the pressure in the headspace decreases. the TOTAL volume of CO2 in the keg does not change, but the equilibrium between the amount in solution in the liquid vs the amount creating pressure in the headspace changes.

Qhrumphf, I think you are mixing up the volume of CO2 in the keg vs the volume of CO2 dissolved into solution on this one.

I just realized when talking this through that this carbonation chart has a trick to it - It does not show you the total volume of CO2 in the keg at all. It only shows you the volume of CO2 that will be dissolved into liquid AT EQUILIBRIUM at a given temperature and pressure.

So if there were no liquid in the keg at all, there would not be 1.7 volumes of CO2 in the keg at 65F and 15 PSI - there would be some unknown number of volumes that this chart cannot show us. But then (hypothetically) if you magically added liquid to the keg without changing temperature or pressure, the pressure would drop to some unknown level because CO2 would dissolve into solution, and an equilibrium would form at some lower pressure and lower volumes

Edit: based on the weight calculations below the theory that we are only seeing a new equilibrium due to temperature is wrong - disregard.

But my point about the carbonation chart showing only volumes of CO2 in liquid at equilibrium is still valid though - good info to remember

 

[Vale71]

Assume room temperature 65F. SG has dropped to within 5 points of predicted Final Gravity. A spunding valve is attached to the fermenter, set to release at 15 psig. Fermentation continues at 65F and pressure rises inside the sealed fermenter until reaching 15 psig when the spunding valve begins to vent CO2, maintaining the internal 15 psig pressure. Due to the increased partial pressure within the fermenter, CO2 is forced into solution in the beer until the liquid becomes saturated. The chart above indicates that the volume of CO2 contained in the liquid is 1.70 volumes.

At Final Gravity when equilibrium is reached, the saturated liquid (beer) is transferred under 15 psig pressure to a CO2 purged, sealed keg via the black Liquid Out post. A keg mounted spunding valve is placed on the gray Gas In post, with a release pressure set to 'something less' than 15 psig. 65F beer (saturated with CO2 @15 psi) flows into the keg. When the transfer is complete, we nominally have 5 gallons of beer at 65F at 15 psig that contains 1.70 volumes of CO2. There are variables of course, including the dimensions and geometry of "sending" fermenter and the "receiving" keg, the pressure differential between the two of the vessels, the headspace between the beer column and the keg lid, the presence of any residual sugar or non-dormant yeast that slipped from the fermenter to the keg, etc., etc., ad infinitum. As you said, the math is complicated and is above my pay grade as well. But I think we can agree that we have at least, nominally, 65F beer saturated with CO2 amounting to 1.70 volumes under 15 psi differential pressure in a sealed keg.

Now we change one variable in the equation. We place the sealed keg in a 38F refrigerator to let it condition for a week or two, even though temperature equilibrium will be reached much sooner. After two weeks we measure the pressure in the keg and find that it has fallen to 11 psig. Does that mean that 4 psi worth of CO2 escaped? No. It went into solution under 15 psig pressure until saturation and equilibration were achieved at 11 psig. The chart above indicates that the volume of saturated CO2 in the beer at that temperature and pressure is 2.48 volumes. The "additional" CO2 wasn't created in a vacuum. It was absorbed into the liquid under pressure from gas in the headspace in a sealed vessel when the temperature was reduced and the liquid was able to hold more of the gas before a new saturation level was reached.

The problem with this example, which if I understood correctly comes from your practical experience, is that under those conditions and assuming a 5 gallon keg filled to nominal capacity, which would contain 5 gallons of beer and 0.35 gallons of headspace, the amount of CO2 in solution by weight is:

75.7g at 15PSI@65°F
110.5g at 11PSI@38°F

You obtain these values by multiplying the number of volumes according to the table times the total beer volume times the density of CO2 (1.96 g/l).
So from transfer to end of conditioning your beer has acquired an additional amount of CO2 equal to almost 35 grams. The problem is that assuming 0.35g headspace at 15PSI@68°F you have a total of 5.9g of CO2 in the headspace, which equals only about 1/6th of the increase you experienced. This can only mean that most of the CO2 came from another source and that source can only be residual fermentable extract that was fermented by the yeast during conditioning. In other words, your beer was not at actual FG when you kegged it. If your beer had only absorbed CO2 from the headspace, with so little headspace and so little CO2 in the gas phase available the carbonation increase would have been much more modest and the drop in headspace pressure much more evident.

 

[TheMadKing]

The problem with this example, which if I understood correctly comes from your practical experience, is that under those conditions and assuming a 5 gallon keg filled to nominal capacity, which would contain 5 gallons of beer and 0.35 gallons of headspace, the amount of CO2 in solution by weight is:

75.7g at 15PSI@65°F
110.5g at 11PSI@38°F

You obtain these values by multiplying the number of volumes according to the table times the total beer volume times the density of CO2 (1.96 g/l).
So from transfer to end of conditioning your beer has acquired an additional amount of CO2 equal to almost 35 grams. The problem is that assuming 0.35g headspace at 15PSI@68°F you have a total of 5.9g of CO2 in the headspace,

How are you accounting for the pressure in this calculation of mass of CO2 in the headspace? at 15PSI the volume of CO2 is not equal to 0.35 gallons, but some higher amount equilibrated to 1 atmosphere right? I'm just trying to get my head around the calculation you're doing.

edit: I just used a Boyle's Law Calculator and I am getting 1.32 liters @ 15PSIG = ~200 liters @ 0 PSIG

edit edit: I put the parameters into the calculator wrong - the actual final volume should be 0.7 gallons or 3.18 liters which weighs 5.8 grams - so I concur with your calculation

 

[Advance]

You might find this thread/post helpful:

https://www.homebrewtalk.com/threads/carbonation-help.680106/post-8885395
With regards to your stone potentially being clogged, try increasing the pressure on your regulator and put your ear near the unitank. You should be able to hear the micro bubbles flowing from the stone.

 

[Brooothru]

Aahh, Yesss. Grasshopper now sees, and is enlightened.

Thanks to @TheMadKing and @Vale71 for the explanation and taking the time to correct my thinking. I see where I was mistaken in my logic. Now back to originally scheduled conflating of apples and oranges.

 

[Qhrumphf]

Yes, the difference in partial pressures between headspace and liquid when not at equilibrium is the math above my pay grade. Where I was getting hung up was your 11 PSI assertion. If you move the beer to a different sized container or anything like that, or anything else that'd change it from being a sealed system, then again above my pay grade. But if you take your sealed unitank at 65F and 15 PSI and 1.7 volumes, and you drop that sealed system to 38F, it should eventually drop a lot lower than 11 PSI. My experience shows that. And the math above seems to say that as well. Only way it does is if you're adding gas or still getting fermentation. I stand my beer bottle allegory. A beer that was packaged at 32F and 2.5 volumes will not jump to 4 volumes just because you warm it up. A unitank is no different.

To the point that it's the volumes in solution only, that makes sense. But if we're talking about a system that's at equilibrium, it's not relevant unless we alter the system to take it out of equilibrium.

Now if you take 5 gallons of beer in a 6 gal unitank at 15 PSI and 65F, but you transfer it to a 15.5gal sankey keg and put THAT under 15 PSI and chill it down, you're gonna end up with a higher amount of eventual volumes than you had before.

 

[Brooothru]

The problem with this example, which if I understood correctly comes from your practical experience, is that under those conditions and assuming a 5 gallon keg filled to nominal capacity, which would contain 5 gallons of beer and 0.35 gallons of headspace, the amount of CO2 in solution by weight is:

75.7g at 15PSI@65°F
110.5g at 11PSI@38°F

You obtain these values by multiplying the number of volumes according to the table times the total beer volume times the density of CO2 (1.96 g/l).
So from transfer to end of conditioning your beer has acquired an additional amount of CO2 equal to almost 35 grams. The problem is that assuming 0.35g headspace at 15PSI@68°F you have a total of 5.9g of CO2 in the headspace, which equals only about 1/6th of the increase you experienced. This can only mean that most of the CO2 came from another source and that source can only be residual fermentable extract that was fermented by the yeast during conditioning. In other words, your beer was not at actual FG when you kegged it. If your beer had only absorbed CO2 from the headspace, with so little headspace and so little CO2 in the gas phase available the carbonation increase would have been much more modest and the drop in headspace pressure much more evident.

I had considered a continuing fermentation as a possible contributing factor but figured it wasn't sufficient. Your math shows that to be true. I also looked at CO2 pickup caused by pressure transferring, but don't understand how to account for it or measure any amount of absorption. I'll take your calculations as accurate that 5.9 gr is the amount of 'headspace' CO2 that could be the theoretical maximum amount to be absorbed and that it would only account for 1/6 th of the weight needed to equal the numbers my observations suggest. I can't imagine that an additional ~29 grams came from a pressurized transfer. So I'm at a loss to explain what I've observed on multiple occasions. I know I'm not accounting for something. Just don't know what it is. But I'll keep trying to find an answer.

Brooo Brother

 

[Vale71]

5.9g is actually the total amount of CO2 you have in the headspace of your keg at that temperature and that pressure. Your beer couldn't even absorb all that or it would create a vacuum in the keg.

 

[Tonypr24]

Guys
So I just ordered my spunding valve but now reading a lot of spunding information here at homebrew talk fermenting under pressure is mostly for lagers...i dont really brew lagers i only do Ales. What is the benefit of a spunding valve for an Ale?

 

[TheMadKing]

Guys
So I just ordered my spunding valve but now reading a lot of spunding information here at homebrew talk fermenting under pressure is mostly for lagers...i dont really brew lagers i only do Ales. What is the benefit of a spunding valve for an Ale?

The main benefit is carbonation using CO2 from the yeast as fermentation winds down rather than an exterior CO2 source. It's a valuable tool to have. It CAN be used to suppress ester formation by stressing the yeast and slowing their reproductive rate, but that is not it's main use.

 

[Qhrumphf]

Pressure fermentation suppresses esters. It allows a cleaner, faster, warmer fermentation for a lager (at the expense of often increased sulfur). It's not beneficial for most ales. However, closing off late fermentation works well with ales to build up (some) natural carbonation, as well allowing pressure for things like crashing. Dry hopping can be a complication, as dry hopping under any level of carbonation can be problematic (hop geyser, though more conmon/dangerous at commercial scale). Dry hopping under pressure is the solution, but requires some additional technique/equipment.

So basically you could close your blowoff 6 pts above your target with your spunding valve at 15 PSI (or 0-1psi if you're gonna dry hop the old fashioned way), allowing fermentation to finish and the spunding valve prohibits any excess pressure.

An airlock or blowoff basically does the same thing. It closes fermentation off until enough pressure is generated to overcome the hydrostatic pressure (ie gravity of liquid) of the height of liquid. Except where a spunding valve might be set at 1bar (just shy of 15 psi), airlock/blowoff pressure would be in the millibar range.

 

[Tonypr24]

Sounds good guys thanks for the info...you guys ever drink the beer straight out of the unitank? Beer is fully carbonated..will move to keg tomorrow but temp is 36 and I just cant stop pouring me some beers. Best hobby in the world.

 

[Qhrumphf]

Yep. All the time. That is hands down your lowest oxygen exposure method of serving, ie the freshest and best shelf life. You just wanna drop the yeast out every few days for a bit, since it's otherwise just sitting on yeast cake. Carb it with the stone if it's not already, get yourself a pigtail if you don't have one, and you're set.

 

[Vale71]

Sounds good guys thanks for the info...you guys ever drink the beer straight out of the unitank? Beer is fully carbonated..will move to keg tomorrow but temp is 36 and I just cant stop pouring me some beers. Best hobby in the world.

I do it all the time. I attach a flow-control faucet directly to the racking port via a QD. That way there are no lines to clean, I just flush the faucet with hot water after every session. It has to be a flow-control faucet though as with no beer line there is no way to balance the system either than with flow-control.

 

[Qhrumphf]

I prefer a pigtail to a flow control faucet. Pours a little better IMO and less moving parts. But your way works too.

 

[SanPancho]

It's perfectly possible to dump yeast and dry hop in a pressurized fermenter. I've done both from day 1 as a Unitank owner and there are plenty of threads on HBT discussing how to do this, even with zero O2 ingress as an addedd bonus. If you don't want to make the effort it's perfectly OK but you're really missing out on a lot by using a Unitank as if it were a glorified SS bucket.

So your process for dry hopping carbonated beer is......

 

[SanPancho]

(though I imagine in a pressurized vessel it's probably more complicated than that)

not really. Co2 line should have a check valve on it (crack pressure). Wetting pressure of stone. Hydrostatic pressure is 1psi per 28” vertical water column.

desired carb pressure + crack + wet + hydro is where you set regulator, I.e. 13psi carb + 1 + 3 + 0.5 ( 14” of beer over stone) means set pressure to 17.5 and let it run for few hours. Easy peasy.

assumptions- Pressures all calibrated with same gauge, beer is at proper temp for psi/volumes, headspace pressure is less than carb target pressure. (Otherwise you’re carbing by head pressure and not the stone)

Also nice to add a little flow meter with a floating ball to gas line so you can see when flow stops.

 

[Advance]

So your process for dry hopping carbonated beer is......

This thread should answer your question:

https://www.homebrewtalk.com/threads/hop-dropper-for-ssb-unitank.680865/

 

[Jtvann]

This thread should answer your question:

https://www.homebrewtalk.com/threads/hop-dropper-for-ssb-unitank.680865/

The question of dry hopping into carbonated beer isn't addressed in that thread. It's easy to to throw hops in, or dump hops in from a canister. Have you ever seen what happens to heavily, or even normally, carbonated beer when you dump hops in? Skip to 1:30 seconds.



That was my comment earlier in the thread that I dont feel was ever addressed.

1- Can you harvest clean yeast. Meaning yeast that does not have dry hops in it. No post cleaning or washing.

2- Can you dry hop with little to no 02

3- Can you spund to naturally carbonate.

4- I know how to individually do any of these. I could even do 2 out of 3 pretty easy. Still havent heard how to do all 3. Any help is appreciated.

 

[SanPancho]

Exactly. That link talks about devices. I asked about process.

even Under pressure you still get breakout of co2 to a degree and foaming. Wastes hops.

 

[Vale71]

Yes you most definitely can do all three of these things.

Near the end of fermentation you'll spund and let your beer carbonate. Only after fermentation has completed do you start collecting yeast, either for dumping or for reuse. To dump yeast under pressure you just need to place a very restrictive attachment on the dump valve. I use a TC to 1/4" barb adapter with 3-4 feet of 1/4" silicone tubing attached. This slows the flow of yeast down enough that you can collect it in a bucket without being showered with yeast yourself.
At this point conditioning starts so your beer will follow the temperature profile you've chosen. You'll keep dumping yeast as it collects to prevent autolysis flavors and to keep the racking port clear of yeast.
As your beer nears maturation you'll dump dry-hops in under pressure without O2 ingress using a rig similar to the ones discussed in several threads on HBT. Half the fun is indeed in figuring out your own contraption and testing it, am I right?
As hop material drops to the dump port you'll dump it and discard. It normally takes 7 to 10 days for beer in a 14 gal Unitank to clear of all hop material depending on temperature (warmer beer clears faster), in the meantime your beer will be ready to be packaged/served. Et voilà.

 

[Jtvann]

Yes you most definitely can do all three of these things.

Near the end of fermentation you'll spund and let your beer carbonate. Only after fermentation has completed do you start collecting yeast, either for dumping or for reuse. To dump yeast under pressure you just need to place a very restrictive attachment on the dump valve. I use a TC to 1/4" barb adapter with 3-4 feet of 1/4" silicone tubing attached. This slows the flow of yeast down enough that you can collect it in a bucket without being showered with yeast yourself.
At this point conditioning starts so your beer will follow the temperature profile you've chosen. You'll keep dumping yeast as it collects to prevent autolysis flavors and to keep the racking port clear of yeast.
As your beer nears maturation you'll dump dry-hops in under pressure without O2 ingress using a rig similar to the ones discussed in several threads on HBT. Half the fun is indeed in figuring out your own contraption and testing it, am I right?
As hop material drops to the dump port you'll dump it and discard. It normally takes 7 to 10 days for beer in a 14 gal Unitank to clear of all hop material depending on temperature (warmer beer clears faster), in the meantime your beer will be ready to be packaged/served. Et voilà.

Thanks Vale

I had read somewhere before, and I have no proof as to its accuracy, that yeast under pressure would suffer when taking them suddenly to a lower pressure. Something about the cell walls rupturing due to sudden pressure change.

I didnt read much into it. I did use a jaybird yeast harvester once to get yeast out, and upon removal I had a yeast volcano. Your constricted line from the dump seems easy, and I've done that before on non carbonated dumps just to control it better.

Question is there though, does a sudden drop on pressure harm yeast in any way?

 

[Vale71]

If your fermenter where 3-4 stories high then possibly yes. At our scale you'll just have to deal with the initial foaming as it degasses and for that you just need a big enough bucket.

 

[Jtvann]

If your fermenter where 3-4 stories high then possibly yes. At our scale you'll just have to deal with the initial foaming as it degasses and for that you just need a big enough bucket.

And then the obligatory question on the dry hop volcano. Do you just dump the dry hops then try to close off all valves before it blows ... thus trapping in the pressure and hops?

 

[Vale71]

And then the obligatory question on the dry hop volcano. Do you just dump the dry hops then try to close off all valves before it blows ... thus trapping in the pressure and hops?

The fermenter is never depressurized even when dumping in hops. The dry-hopping contraption is evacuated and then pressurized to the same level as the fermenter so that all that happens when you open the valve is that the hops fall in. You don't even hear the faintest "hissss" sound.

 

[Jtvann]

The fermenter is never depressurized even when dumping in hops. The dry-hopping contraption is evacuated and then pressurized to the same level as the fermenter so that all that happens when you open the valve is that the hops fall in. You don't even hear the faintest "hissss" sound.

Alrighty, all I really need is a 3 inch butterfly. I can use my inline filter housing for holding hops, and set a tee on top for spunding and pressure release. I already have everything except the valve. Might have to give it a whirl on my next brew.

 

[Vale71]

Ideally you should also get a cheap vacuum pump. It's hard to get most of the O2 out just with CO2 washing, multiple evacuation cycles is really the way to go.

 

[Jtvann]

Ideally you should also get a cheap vacuum pump. It's hard to get most of the O2 out just with CO2 washing, multiple evacuation cycles is really the way to go.

Eh, what I'm doing now is producing good beer. Any improvement on that is gonna have to be enough for me. I'm close to done with tinkering.

 

[Vale71]

I'm close to done with tinkering.

There's no such thing, really. It's like a drug addict saying "I can quit any time". You'll see...

 

[Advance]

Exactly. That link talks about devices. I asked about process.

even Under pressure you still get breakout of co2 to a degree and foaming. Wastes hops.

I outlined the equipment and my step by step procedure in post #22 from the thread I listed on my prior post. I have never had a hop eruption using this method. Even when dumping 12 oz of hops into beer that has been sitting at 15 psi head pressure from spunding. The trick is to match the head pressure with the pressure in the spool containing the dry hops before dropping them into the fermenter. The videos of dry hop euruptions I have seen, including the one posted in this thread have all resulted from brewers releasing the head pressure on the fermenter, then dumping the dry hops from a open port. The massive number of nucleation sites coupled with zero head pressure is what is causing all the CO2 to come out of solution.

 

[Vale71]

even Under pressure you still get breakout of co2 to a degree and foaming. Wastes hops.

How does that waste hops? I've never seen any hop material jump out of the fermenter, it all gets and then stays in the beer. As for CO2 breaking out I have a very sensitive electronic manometer with 0.01 bar resolution and I've never seen the headspace pressure go up even by just that tiny amount after dropping in hops so any CO2 release has to be really negligible. If even that is unacceptable to you then I don't see any other possibility but to fully degas the beer before dropping in the hops and that seems a bit excessive, wouldn't you agree?

 

[TheMadKing]

Ideally you should also get a cheap vacuum pump. It's hard to get most of the O2 out just with CO2 washing, multiple evacuation cycles is really the way to go.

I posted a thread on this awhile back, do you have any measurements showing the relative effectiveness of each method?

 

[Qhrumphf]

I'd be very cautious using a vacuum pump unless you know that the vessel you're using it on can withstand it. For example, a commercial bottling line will usually use a vacuum while purging bottles where canning lines cannot without collapsing the cans. Many conical fermenters (unitank and otherwise) cannot handle much for negative pressure despite being able to handle lots of positive pressure.

If you wanna build something and try it with a vacuum pump, safely test it first and understand the chance to collapse it is there. If you're buying something, I'd ask. If they don't know the answer, see above.