Pressure Ferment / Closed CO2 Pressure Keg Transfer Questions / How to?

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haeffnkr

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Hi,
My process to transfer beer lately has been to catch the beer in the fermenter with 1 to 4 points left of sugar left in it ( add a bit of sugar to the keg if needed to get carb level right ) and push beer from fermenter into purged keg with co2 and a spund valve on the gas post to keep it all closed loop. Any oxygen in the keg is eaten by the remaining fermentation in the keg. I then let the keg set at high end of yeast temps for about a week then put in the kegerator and serve.

Now I am trying my hand at pressure fermentaton. I have an ale at 70F and the pressure is 23 psi so far with the spund valve set at 28 to carbonate to around 2.4 vols.

What do I do next? Cold crash and then hook up co2 to the fermenter ( with floating dip tube ) at 15 psi then push the beer over to kegs with the spund valve set lower, say 5 pounds to keep the transfer closed and purged of 02? Is cold crashing going to help or hurt the beer/02 level in the beer? I guess i would make the beer clearer in the keg but I dont really have any issues with clearing of beer regardless and I thought the cold crash would get the beer pressure lower than 28 so I can transfer over?

Or?

thanks in advance for the help!
haeffnkr
 

eric19312

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The cold crash will decrease pressure in the keg. If you are at 28 PSI in a 70F keg and drop temperature of the keg (and the beer in the keg) to 38F pressure in the keg should drop to about 10.1 PSI.

To pressure transfer beer from a keg at 10.1 PSI you will purge the receiving keg, and pressurize it to something a little less than 10.1...could be 8-9 PSI with spunding valve on the receiving keg maintaining that pressure. Then put something like 12 PSI on top of the beer and push it over. By having a relatively small difference in pressure of the beer and pressure in the receiving keg you limit foaming. The pressure above the beer helps the beer flow a little faster.
 

DuncB

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Agree with @eric19312
The other thing that helps is get your donating fermenter higher than receiving keg and if you have any larger diameter tube for beer transfer line it will speed things up a bit.
Don't be tempted to bleed out pressure in receiving keg to accelerate transfer as you will lose some carbonation and make foam.
The process takes time I find at least half an hour.
If you get your pressures right during ferment and they will change during cold crash the beer should be cold and calmed correctly immediately after transfer. But some time conditioning will improve the beer no doubt.
 
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renstyle

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Hi,
My process to transfer beer lately has been to catch the beer in the fermenter with 1 to 4 points left of sugar left in it ( add a bit of sugar to the keg if needed to get carb level right ) and push beer from fermenter into purged keg with co2 and a spund valve on the gas post to keep it all closed loop. Any oxygen in the keg is eaten by the remaining fermentation in the keg. I then let the keg set at high end of yeast temps for about a week then put in the kegerator and serve.
If you're pushing beer to a purged keg, whether it is multiple "burps" of CO2 from the tank on the headspace, or a liquid purge a-la starSan, there should be *very* minimal O2 in the headspace. The priming sugar will create your carbonation, yes.

Now I am trying my hand at pressure fermentaton. I have an ale at 70F and the pressure is 23 psi so far with the spund valve set at 28 to carbonate to around 2.4 vols.

What do I do next? Cold crash and then hook up co2 to the fermenter ( with floating dip tube ) at 15 psi then push the beer over to kegs with the spund valve set lower, say 5 pounds to keep the transfer closed and purged of 02? Is cold crashing going to help or hurt the beer/02 level in the beer? I guess i would make the beer clearer in the keg but I dont really have any issues with clearing of beer regardless and I thought the cold crash would get the beer pressure lower than 28 so I can transfer over?

Or?

thanks in advance for the help!
haeffnkr

I am one day into cold crashing a pressure-BoPils. I set my spund to 12PSI during fermentation.

When I moved the ferm-keg into the keezer to crash at 44F, serving (tank) pressure is dialed in at 13PSI.

I hooked up the tank to compensate for the drop in pressure due to temp and to prep the batch for serving. Now once I am ready to transfer the batch will be fully carbonated, coincidentally also at 2.4 vol.

You'll do the same steps to purge the eventual serving keg (I do the starSan liquid purge), then pressurize up to serving pressure and add the spunding valve.

Add the liquid-to-liquid jumper between the fermenter and serving keg. There should be minimal flow initially because the serving keg is also at pressure.

Then you can decide how fast you wish to transfer.

Turn the dial way down (up?) beyond the tank pressure, and slowly dial it back. I have a mesh screen intake on the end of a floating dip tube in the ferm-keg, so the flow is fairly clear from the outset.

My spunding valve is usually reading 11-12PSI while it whistles. I take a good 30 mins to transfer 5gal this way, very slow but it works pretty well.
 

DuncB

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If you purge the starsan during the ferment and also get the receiving keg to your ferment pressure ( 27psi in your case). Then disconnect and continue spund and cold crash as normal.
Then when transfer time comes gas to gas will equalise with keg but more pressure will be raised in your fermenter as it will have dropped during cold crash.
This gives you a " free " start to the transfer, you just need to kick off transfer with a little receiving keg purge.
I have seen transfer done with gas to gas connected once the siphon starts but haven't found it very successful in my hands and normally need to add more gas. Of course if you purge a couple of kegs to 27psi then the spare one can be used as a gas supply as well.
Not sure on the cost saving but it's a little bit of planet saving.
My last CO2 cylinder refill cost 80 us dollars for a 12lb refill which was pretty steep as previously it cost 40 dollars.
 

renstyle

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If you purge the starsan during the ferment and also get the receiving keg to your ferment pressure ( 27psi in your case). Then disconnect and continue spund and cold crash as normal.
Then when transfer time comes gas to gas will equalise with keg but more pressure will be raised in your fermenter as it will have dropped during cold crash.
This gives you a " free " start to the transfer, you just need to kick off transfer with a little receiving keg purge.
I have seen transfer done with gas to gas connected once the siphon starts but haven't found it very successful in my hands and normally need to add more gas. Of course if you purge a couple of kegs to 27psi then the spare one can be used as a gas supply as well.
Not sure on the cost saving but it's a little bit of planet saving.
My last CO2 cylinder refill cost 80 us dollars for a 12lb refill which was pretty steep as previously it cost 40 dollars.

I wasn't following initially when you suggested getting the serving keg up to 27PSI, then cold crashed the fermenter.

Would both vessels be chilled down to cold crash temps (keeping the internal pressures similar) or just the fermenter? If it is both I follow, but if only one not so sure.

On the other hand: using ferm-gas to purge & over-pressurize an empty keg to utilize later as FREE transfer pressure? That's a very intriguing idea!
 

DuncB

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@renstyle
The op mentions that the fermenter set at 23psi but rising to 28psi.

You purge the receiving keg ( with ferment gas ) in your usual way but then let it fill it to 28psi say with spunding valve on gas post (you do have to make a gas to liquid line to do this).

Then disconnect it and you have a keg at 28psi ( or two if you do more than one).
Keep that keg at room temp or cool it down to kegerator temp ready to transfer.
At transfer time the fermented keg pressure will have dropped but the receiving keg still around 28psi as pressure can't drop as no liquid in that keg to absorb the gas. I don't bother chilling the keg, as it soon gets cold and the cold crash is lower than my serving keg fridge anyway.

Connect gas to gas and the pressure will equalize, disconnect gas line.

Liquid to liquid and a little purge of receiving keg and transfer starts. If you reconnect gas to gas and a good enough siphon occurring a lot of transfer can occur especially with a good height difference or you are emptying your fermenter from the bottom. I empty the fermentasaurus from the top so there's bit of uphill and find this doesn't work that well and the process needs driving with CO2 and spunding on the receiving keg.
If you filled another keg to 28psi you can use that to drive the process a bit as well.

Does that make a bit more sense?

IMG_20210513_000730_1.jpg
 

renstyle

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At transfer time the fermented keg pressure will have dropped but the receiving keg still around 28psi as pressure can't drop as no liquid in that keg to absorb the gas. I don't bother chilling the keg, as it soon gets cold and the cold crash is lower than my serving keg fridge anyway.

Connect gas to gas and the pressure will equalize, disconnect gas line.

That was the part that I was unclear on. Even with no liquid in the keg, chilling a purged vessel will still drop the internal pressure below 28PSI to something.... less (math is hard). I thought that difference was important to the story.

Turns out I was overthinking it, as your very next sentence made the pressure differences irrelevant, you start with equalized pressure between the two, then went about starting up the closed-transfer-siphon.

Thanks for sticking with me on that, much clearer now!
 

DuncB

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Glad we got there. It seems to work quite well. Basically I use very little cylinder gas for purging or transfers.
In fact the fermenter that I transfer the beer out of is full of gas at say 12 psi at the end. I actually use that gas to purge the next keg or at least start the purge. After all it is ferment gas so might be purer than CO2 from a cylinder and saves some time at the next keg purge / pressurising phase.
You are right the pressure will drop if the keg is cooled ( boyles law perhaps for the maths ?) but as you say complicated and not that relevant.
 

Red over White

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All great points above, a few things that work for the "clearest" xfers on my gear are gravity, jumper length and minimum pressure differences between the two vessels. Closed loop gravity xfers are slow as Christmas, but work great for not stirring up the bottom or the top with ales. Co2 breakout with the wrong diameter or length jumper hoses can work against you just like when serving. Keeping the fermenter and receiving vessel within 1-2 psi runs the least risk of breaking up and floating any yeast from the bottom of the fermenter that can happen if you depressurize the fermenter quickly. Good luck
 

DuncB

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@Red over White
Agreed keep donor pressure higher than receiver target at all times. I've quite often managed to get all the yeast dropped into the collection bottle on my setup and can close the valve to it to prevent it rising up. But getting the pressures right stops this.
I reckon if I got some 6mm internal diameter liquid tube and transferred off the bottom of my fermentasaurus the process would be much quicker.
I find it difficult to not stand around and keep an eye / ear out for problems.
End of floating dip tube popping above beer surface occasionally happens and the fermenter needs a bang on the side to sort that out. But will only occur once I'm low in the cone part of the fermenter.
 
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haeffnkr

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Hey All,
Thanks for the replies!

So nothing really changes from my current process. Purge the receiving keg, apply co2 to the fermenter and push beer to the receiving keg with the spund valve set just below my pushing/fermenter pressure.

When do you transfer to a keg in the fermentation schedule? Soon as the beer is FG or a point above FG to clean up an o2 in the serving keg? If after cold crashing, beer is clearer but has no working yeast so purge / transfer process must be good to keep any 02 out of the serving keg right?

thanks again
haeffnkr
 

DuncB

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Well I purge a keg filled to the brim with starsan ( you can save this and reuse it) there's very little oxygen in the keg after this method esp if you also purged for a while with late ferment gas.
I tend to cold crash the beer and finings if being used so that I'm transferring clear beer to my serving keg.
If I was going to naturally carbonate in the keg I wouldn't necessarily go to all that trouble just transfer a few points above final and let it finish off in the keg. But that way there is more yeast in your serving keg and it takes a bit of time to settle.

Clear beer still will have yeast in it unless it has been filtered. But if you've crashed it to clear it and then transfer into a poorly prepared keg that you need to second ferment in to get rid of oxygen you could have avoided in the first place and make yeast again it seems a little counter productive. It would be a particularly bad plan if it was a very hoppy beer as you are planning for deterioration.
 

renstyle

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I starSan purge my serving keg also, so oxygen has been reduced to concentrations that (for me) it's essentially zero for all intents and purposes in the serving keg.

I generally let my batches run all the way to FG while still in primary, whether under pressure or not.

I always ferment in a corny keg, so as long as I don't open the fermenter, no oxygen will be introduced.

Transferring with a spunding valve keeping the pressure differential at 1-2PSI maintains this. No need for any priming sugar to consume residual oxygen.
 

renstyle

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Had a related question regarding a diacetyl rest with a pressure fermented lager (two actually).

I just finished transferring a BoPils pressure fermented with Wy2001 to a serving keg. I have another BoPils about ready to transfer to serving that used 34/70 dry yeast.

I skipped the d-rest on both of these batches, thinking it wasn't necessary as I was working with elevated temperatures the whole time.

Curious to your thoughts and experiences in this regard?
 
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