Cold crash Unitank

[Tonypr24]

Hello

Was wondering if anyone can give me some advice on what to do for cold crashing in SS brewtech unitank. I just got it and this is my first batch fermenting. Beer has been fermenting for almost 7 days now and I am getting ready to cold crash but as I read more and more about negative pressure caused by cold crashing you want to make sure I supply CO2 thru either carb stone..Ok I get this part.
What I don't get is that SS brewtech tech suggest
"The blow off apparatus should be removed, and the blow
off cane ball valve should remain open during cold crashing to keep the vessel at atmospheric pressure."

The blow off ball valveshould remain open??? This makes no sense. What is preventing infection from this open valve? What is the purpose of th PRV if I have to leave the blown off valve open?

 

[Jtvann]

Blow off apparatus removed means take away your jar of starsan. You dont want that sucked back up.

You have 2 options:

1- Attach your CO2 to blow back into the blow off cane, at which point it will need to be open.

2- Attach your CO2 to the carb stone. With this option, keep the blow off cane closed.

 

[Vale71]

The real question is: why is your beer not already carbonated via spunding? Seems like a waste of a perfectly good unitank to me...

 

[Tonypr24]

The real question is: why is your beer not already carbonated via spunding? Seems like a waste of a perfectly good unitank to me...

I know..I've been brewing for a long time but I've been doing it the cheap way using glass carboy. I am not too familiar with Unitank but a spunding valve will be my next purchase.

I thought I could use the PRV as a spunding valve when I got the unitank but now find out I'm not supposed to.

 

[Jtvann]

The real question is: why is your beer not already carbonated via spunding? Seems like a waste of a perfectly good unitank to me...

If you harvest your yeast and/or dry hop, spunding is a little more of a hassle. If theres a better way, and I'm missing something, please let me know.

To harvest, I need to let the yeast finish. I ideally need the yeast to be clean, so harvest before dry hopping. If both of those are true, plus I need to dry hop, then I can't spund.

 

[Vale71]

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.

 

[Jtvann]

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.

I hear ya. I'm going to pull the lazy card for now on searching the forums. Do you mind laying out a time frame for how to do it? I'm cold crashing a neipa right now with a stupid amount of hops that I did spund to same aroma.

How do you save good clean yeast, dry hop with minimal O2, and spund?

I'm assuming it involves a dry hop canister similar to one like mongoose uses?

 

[Brooothru]

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.

Exactly what @Vale71 said. In this case, a spunding valve is your best friend. IIRC your Unitank came with a TC port on the manifold for a spunding valve. The one Ss Brew Tech sells is a little pricey, but is well worth the investment. Set it to about 15 psig, which is the advertised maximum normal operating pressure for the Unitank. When fermentation is nearing the end (about 5 points before terminal gravity), close the blow-off ball valve. Fermentation will continue and pressure will build inside the fermenter. When it reaches your set point, little bubbles will start escaping from the cup on the spunding valve, and will stop when fermentation is complete. Say your predicted final gravity is 1.010. You'd want to "cap" the fermenter (install the spunding valve and close the blow-off valve) somewhere around 1.015 SG. It doesn't matter if you cap too early, say 1.018~1.020 SG, because excess pressure will simply bleed off through the spunding valve. Once the bubbles stop, you know fermentation has stopped. Now you can cold crash.

You don't need to worry about negative pressure or suck-back, because you have an excess of positive pressure in the Unitank. As the temperature goes down, so does the pressure, but it is still positive pressure. Let's say you want your beer carbonated to 2.5 volumes (just about right for most lagers and ales). At 15 psig and 65F temperature you're only carbed to 1.7 volumes, but when you lower the temperature to 38F, your tank pressure will be 11 psig but the CO2 volumes will be 2.47, right at your desired 2.5 volumes carbonation. You'll be perfectly carbed up and cold crashed without any danger of sucking up Star San or imploding your Unitank, all in one easy step!

I usually let things settle out for several days after cold crashing and then transfer under pressure to a keg. At some point you'll reach equilibrium between pressure in the Unitank and pressure inside the keg. You can bleed off keg pressure by opening the PRV on the keg or attaching a keg post mounted spunding valve to slowly bleed off pressure, or attach a CO2 source to the carbonating stone on the Unitank (or both, to speed things up). When the transfer is complete, top off the CO2 pressure in the keg to match your serving temperature and desired carbonation volumes. Then condition/lager for 2 weeks for ales, 2 months for lagers. Done deal. These Unitanks are really versatile. Make use of all their capabilities.

Brooo Brother

 

[Brooothru]

I know..I've been brewing for a long time but I've been doing it the cheap way using glass carboy. I am not too familiar with Unitank but a spunding valve will be my next purchase.

I thought I could use the PRV as a spunding valve when I got the unitank but now find out I'm not supposed to.

Yeah, that would be a really bad idea. The PRV is a last ditch safety device to prevent us mere mortals from killing ourselves or otherwise ruining our day. It's the "if everything else has failed, this might prevent loss of life or serious damage to the immediate surroundings" kind of device. Remember, the maximum normal operating pressure of your tank is 15 psig. It won't explode if you get to 20 psi (probably). Might even make it to 25 psig (less likely) or 30 psig ("Are ya' feelin' lucky, punk?"). If you and it survive such a stress test, you'll still never know what permanent internal stresses or deformations have been suffered by the pressure vessel. Over-stresses are cumulative, and cyclical repeated stresses will result in material failure at some unknown future time, possibly at a pressure as low as the advertised maximum normal operating pressure. Best not to tempt fate or tease the animals.

Brooo Brother

 

[Tonypr24]

Guys thanks for all this info. 2 more questions...
So can I dump yeast without a hooking up CO2 or would that also cause negative pressure?

2nd..can I carbonate in the unitank without a spunding valve if I set CO2 to 12psi?

 

[Qhrumphf]

Exactly what @Vale71 said. In this case, a spunding valve is your best friend. IIRC your Unitank came with a TC port on the manifold for a spunding valve. The one Ss Brew Tech sells is a little pricey, but is well worth the investment. Set it to about 15 psig, which is the advertised maximum normal operating pressure for the Unitank. When fermentation is nearing the end (about 5 points before terminal gravity), close the blow-off ball valve. Fermentation will continue and pressure will build inside the fermenter. When it reaches your set point, little bubbles will start escaping from the cup on the spunding valve, and will stop when fermentation is complete. Say your predicted final gravity is 1.010. You'd want to "cap" the fermenter (install the spunding valve and close the blow-off valve) somewhere around 1.015 SG. It doesn't matter if you cap too early, say 1.018~1.020 SG, because excess pressure will simply bleed off through the spunding valve. Once the bubbles stop, you know fermentation has stopped. Now you can cold crash.

You don't need to worry about negative pressure or suck-back, because you have an excess of positive pressure in the Unitank. As the temperature goes down, so does the pressure, but it is still positive pressure. Let's say you want your beer carbonated to 2.5 volumes (just about right for most lagers and ales). At 15 psig and 65F temperature you're only carbed to 1.7 volumes, but when you lower the temperature to 38F, your tank pressure will be 11 psig but the CO2 volumes will be 2.47, right at your desired 2.5 volumes carbonation. You'll be perfectly carbed up and cold crashed without any danger of sucking up Star San or imploding your Unitank, all in one easy step!

I usually let things settle out for several days after cold crashing and then transfer under pressure to a keg. At some point you'll reach equilibrium between pressure in the Unitank and pressure inside the keg. You can bleed off keg pressure by opening the PRV on the keg or attaching a keg post mounted spunding valve to slowly bleed off pressure, or attach a CO2 source to the carbonating stone on the Unitank (or both, to speed things up). When the transfer is complete, top off the CO2 pressure in the keg to match your serving temperature and desired carbonation volumes. Then condition/lager for 2 weeks for ales, 2 months for lagers. Done deal. These Unitanks are really versatile. Make use of all their capabilities.

Brooo Brother

Either you've found a way to create CO2 in a vacuum, or you're not as carbed as you think you are. You can't reach 2.5 volumes with 15 psi at room temp. Unless you continue to generate pressure by fermentation after crashing, you're not gonna increase the volumes. You need about 30psi to carb at room temp. If you can't do that safely you'll have to carb some other way.

Guys thanks for all this info. 2 more questions...
So can I dump yeast without a hooking up CO2 or would that also cause negative pressure?

2nd..can I carbonate in the unitank without a spunding valve if I set CO2 to 12psi?

1. Yes, dropping yeast will create negative pressure in a sealed tank. Applying a few PSI of head pressure (or doing after spunding when pressure has already developed) is plenty.

2. If you keep the psi below the operating limit of your tank, you can absolutely carb that way.

 

[Qhrumphf]

Look at it this way: volumes of CO2 is a measurement of the amount of CO2 present. The temp and pressure are adjustable and related to each other. For a certain volumes of CO2 in a sealed container, changing the temp will change the pressure, or vice versa. In either cases, the volumes of CO2 do not change. 1.7 volumes at 68F will still be 1.7.volumes at 38F. The only way to increase the volumes of CO2 is to add CO2. Either created by fermentation or externally supplied. If you were experiencing something different, your tank probably wasn't at equilibrium on either end (likely on the crash end), or you had continued fermentation after crashing generating additional CO2.

 

[Tonypr24]

Any of you ever had the sampling valve clogged? I am still seeing bubbles come out of the blow off valve and I dont want to reli on the bubbles to figure out where my beer is but I can't take a sample of it to take a reading. I also don't want to dump out the yeast if it's not done yet. Any suggestions?

 

[Qhrumphf]

Where is your sampling port? If it's on the racking arm and the arm was pointed up such that yeast could settle in there, then yes, absolutely it could clog. If there's a valve before it you can close off, you could remove it and check.

 

[Tonypr24]

Where is your sampling port? If it's on the racking arm and the arm was pointed up such that yeast could settle in there, then yes, absolutely it could clog. If there's a valve before it you can close off, you could remove it and check.

Its seperate from the tracking valve. It has it's own port just above the racking valve.

 

[Tonypr24]

Its seperate from the tracking valve. It has it's own port just above the racking valve.

Meant racking valve

 

[Qhrumphf]

Definitely possible it's still clogged.

First I'd try closing your blowoff, put maybe 10 PSI on your tank, and see if you can't blow out the clog with some pressure behind it. Blow that pressure back down when you're done.

If that doesn't work, if there's a way to do so without contamination or introducing a bunch of oxygen, could try and backflush it out with CO2.

 

[Tonypr24]

Definitely possible it's still clogged.

First I'd try closing your blowoff, put maybe 10 PSI on your tank, and see if you can't blow out the clog with some pressure behind it. Blow that pressure back down when you're done.

If that doesn't work, if there's a way to do so without contamination or introducing a bunch of oxygen, could try and backflush it out with CO2.

Yea just closed the blow off. Will let it get to maybe 5psi and try it.

Thanks

 

[Qhrumphf]

Unless you want to ferment under pressure, I'd just hook up CO2 and raise it manually, then burp it back off when you're done. Without a spunding valve and unknown level of attenuation, I wouldn't risk that regardless.

 

[Vale71]

Unless you want to ferment under pressure, I'd just hook up CO2 and raise it manually, then burp it back off when you're done. Without a spunding valve and unknown level of attenuation, I wouldn't risk that regardless.

Unless the user removed it the SSB Unitank has a PRV so no there is no risk involved in closing off the racking arm at any time.

 

[Qhrumphf]

PRVs can and do fail. Relying on a PRV is like relying on a GFCI. Test it regularly and use good practice, and don't rely on it to save your ass.

 

[Qhrumphf]

Otherwise, if what you were saying was true, you could just use it as a spunding valve.

There's a reason most commercial fermenters and brites have not one but two PRVs, in case it's needed and one of em fails.

 

[Vale71]

PRVs can and do fail. Relying on a PRV is like relying on a GFCI. Test it regularly and use good practice, and don't rely on it to save your ass.

So you're saying that a safety feature is inherently unreliable and should not be relied upon to ensure your safety? Seems a bit contradictory to me.
Do you actually have two PRVs on your Unitanks? And in case you don't, have you removed the shutoff valve on the blow-off port to ensure that under no circumstances the fermenter could be sealed and allowed to build up pressure while in an inherently unsafe configuration?

 

[Qhrumphf]

Do you actually have two PRVs on your Unitanks?

Yes. And I test them between every batch.

 

[Vale71]

Then you are indeed more safety conscious then the rest of the world...

 

[Qhrumphf]

Lemme put it this way. Even if it's hooked up to a GFCI, would you take a hair dryer into the bathtub?

Seems pretty standard safety practice in all walks of life to me. Have the safety feature, verify the safety feature, but use good practice such that you don't need the safety feature.

I've had a PRV get enough krausen in it to interfere with operation. This is quite common. Fortunately it blew a sight glass hose clamp before anything more dangerous. Also blew the top off a non-unitank doing a pressure transfer because the PRV on the lid couldn't keep up with the level of gas going in (at only a couple PSI fortunately). After those I take no more chances.

 

[Vale71]

Your simile is a bit forced. Our body is not meant to be electrocuted routinely, a pressurized vessel is meant to be pressurized and there are safety margins built in.

Fact is, I've never seen, even in commercial operations, more than one PRV installed. Apparently your safety requirements are higher than those that commercial operations abide by. Good for you but I think that accusing everybody else of being suicidal is a bit over the top.
As for the PRV getting clogged with Kräusen I guess it was one of those teeny tiny things some manufacturers use? SSB's PRV is massive and I've never heard of one getting clogged with debris, much less of it being a common occurrence.

Personally I would never put pressure on a vessel that is not pressure rated, not even a couple PSI and not even if the manufacturer says it's OK.

 

[Qhrumphf]

Oh for sure that last example was user error on my part. No question about that one.

 

[Tonypr24]

Guys
I left the blow off valve off overnight and I have about 5psi in the Unitank now. I was able to open my sampling valve and got it unclogged.

Can I use this same 5psi to cold crash or do I still need to hook up CO2 to maintain the pressure?

 

[Qhrumphf]

What does the gravity look like? If it's close to your target (4 points or less, especially if within that much of a FFT) you should be fine to leave it as is.

If it's more than that, I wouldn't leave it without a spunding valve in addition to the PRV, so I'd blow the pressure down and check again tomorrow, and the next day, until you're 4 points or less above target. If you wanna trust the PRV to handle the excess that's up to you.

5psi is plenty to crash.

 

[Tonypr24]

What does the gravity look like? If it's close to your target (4 points or less, especially if within that much of a FFT) you should be fine to leave it as is.

If it's more than that, I wouldn't leave it without a spunding valve in addition to the PRV, so I'd blow the pressure down and check again tomorrow, and the next day, until you're 4 points or less above target. If you wanna trust the PRV to handle the excess that's up to you.

5psi is plenty to crash.

I'm exactly 4 points from FG. I'll leave it as is until Its completely done but watching the psi then cold crash.
Thanks everyone for all your help and good info

 

[Tonypr24]

I promise last question..
You guys dumb the first yeast then cold crash or do you cold crash first then dumb out?

 

[Brooothru]

Either you've found a way to create CO2 in a vacuum, or you're not as carbed as you think you are. You can't reach 2.5 volumes with 15 psi at room temp. Unless you continue to generate pressure by fermentation after crashing, you're not gonna increase the volumes. You need about 30psi to carb at room temp. If you can't do that safely you'll have to carb some other way.

No, what I said was if your tank pressure is 15 psig @ 65F, it would yield 1.7 volumes CO2, assuming saturation. If you then lower the temperature to 38F the pressure in the tank falls to 11 psig. The forced carbonation tables indicate that 11 psig @ 38F (saturated) is 2.47 volumes CO2. Conversely, if you force carbonated 65F beer to 2.5 volumes CO2 is would take approximately 19 psig pressure (not 30) to reach that level of carbonation (allowing for gas equilibration, not "crash and dash" carbonation). Once saturated, if the temperature of the beer was lowered to 38F is would contain 4.15 volumes, or over-carbonated for virtually all styles. And yes, a small amount of carbonation likely continues to be produced if any viable yeast remain, though not in a vacuum.

Brooo Brother

 

[Vale71]

You can't predict at what pressure beer will reach equilibrium based on temperature difference alone. CO2 will be absorbed by the beer until a new equilibrium is reached. How far this goes will also depend on the headspace to beer volume ratios and it's a bit more complicated to calculate.

 

[Tonypr24]

I promise last question..
You guys dumb the first yeast then cold crash or do you cold crash first then dumb out?

Anyone?

 

[CodeSection]

I promise last question..
You guys dumb the first yeast then cold crash or do you cold crash first then dumb out?

Anyone?

As I stated in another thread.....
FWIW, I usually perform my first dump just prior to cold crashing. I perform a second dump after waiting at least 24 hours from the start of cold crashing (somewhere between 24-36 hours). I perform my third dump just prior to performing a closed transfer to my bright tank.

I measure the volume of all dumps and keep that info in the particular recipe I brewed so as I can compare it to future brews. As you can imagine, each dump produces less volume.

Since I use Norcal's yeast brink to inject hops when dry hopping, I perform a dump prior to injecting the hops. Then I follow the procedures described above.

 

[Qhrumphf]

.If you then lower the temperature to 38F the pressure in the tank falls to 11 psig.

Show your work. This is where I'm losing you. My understanding of the physics as well as my practical experience says that in a sealed, saturated, equilibrium state, the pressure will fall further than that- eventually to 3 PSI. Unless additional CO2 is provided or supplied to the system.

If what you're saying was true, take a bottle of beer packaged at 32F and 2.5 volumes, warm it up and let it stabilize and you suddenly have champagne levels of carbonation? It doesn't work that way. The pressure will increase. When you open it carbonation will come out of solution faster. But it won't be more carbonated.

Either I'm completely misunderstanding what you're trying to say, or you're wrong.

Now if you're dealing with a system that's not under equilibrium, that's more complicated and that math is above my pay grade.

 

[Qhrumphf]

I promise last question..
You guys dumb the first yeast then cold crash or do you cold crash first then dumb out?

Depends on what you're trying to accomplish. If you're already fully crashing a finished beer and you're disposing of the yeast, I'd fully crash and then dump. If you're looking to age it in bulk in the fermenter, I'd do small periodic dumps while at storage temp. If you want to harvest yeast and/or dry hop, I would probably soft crash (like lower 50s rather than 30s), for maybe 48 hrs then harvest/dump and if applicable then dry hop after it's dumped.

 

[Tonypr24]

Depends on what you're trying to accomplish. If you're already fully crashing a finished beer and you're disposing of the yeast, I'd fully crash and then dump. If you're looking to age it in bulk in the fermenter, I'd do small periodic dumps while at storage temp. If you want to harvest yeast and/or dry hop, I would probably soft crash (like lower 50s rather than 30s), for maybe 48 hrs then harvest/dump and if applicable then dry hop after it's dumped.

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.

 

[TheMadKing]

Depends on what you're trying to accomplish. If you're already fully crashing a finished beer and you're disposing of the yeast, I'd fully crash and then dump. If you're looking to age it in bulk in the fermenter, I'd do small periodic dumps while at storage temp. If you want to harvest yeast and/or dry hop, I would probably soft crash (like lower 50s rather than 30s), for maybe 48 hrs then harvest/dump and if applicable then dry hop after it's dumped.

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"