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Author Topic: Spunding process question  (Read 398 times)

Offline tferguson

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Spunding process question
« on: May 09, 2024, 03:22:14 pm »
I am getting ready to try using a spunding valve for the first time.  I ferment in full size sanke keg.

If I spund the keg near terminal gravity with the hopes of getting carbonation around 2.3 volumes I will need to set the valve around 25 psi at normal fermentation temperature for an ale.

If I then try to transfer this beer at ale temperatures won't I have a foaming mess?  If I actively cool the finished beer before kegging won't I have an issue with the internal sealed keg pressure dropping as the temperature drops in the beer?

Anyone have any tips?   

Offline Drewch

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Re: Spunding process question
« Reply #1 on: May 09, 2024, 07:58:34 pm »
I'm curious to hear what more experienced voices say on this.

My own experience has been that since your temperature drop in absolute terms isn't that much (from say 525 Rankine to 500 Rankine or so, or about a 5% ish drop in absolute temperature), the pressure drop isn't that big either.

But my experience is limited, and I'm not a physicist. So make sure you film it so that if it does implode, at least you can go viral.
« Last Edit: May 09, 2024, 08:03:45 pm by Drewch »
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Offline Richard

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Re: Spunding process question
« Reply #2 on: May 09, 2024, 10:52:23 pm »
I have no experience with spunding, but I am a physicist and I have experience with cooling beer and transferring carbonated beer.

There are 3 factors that affect the pressure when cooling beer from ale fermentation temperature to near freezing: 1) the shrinkage of the liquid volume (look up water density vs temperature), 2) the shrinkage of the gas volume in the head space according to PV=NRT, and 3) the solubility of CO2 as a function of temperature. The first one is minor. The pressure change from the second one is significant, and the third is a function of the ratio of liquid to head space volume. CO2 solubility increases as you cool the beer, so the beer dissolves gas from the head space and reduces the pressure. My experience is with using a mylar balloon to supply the CO2 to keep the pressure from going negative as the beer cools. but I would be very surprised if the pressure drop would exceed 25 psi in any reasonable temperature drop and  liquid/gas ratio. When starting with 25 psi at 20 C I would expect that you would still end up with positive pressure even when cooling to near 0 C.

Now for the foaming issue. My experience is with using a beer gun to transfer carbonated beer from a pressurized keg into bottles. The first step is to drop the head pressure to a few psi for the transfer. The cooling will help with that, but you will probably still need to open a pressure relief valve to lower the pressure even more. That will not affect the carbonation level in the beer in the short run, but will slow the transfer rate. To deal with the carbonation of the beer you need a long transfer line with a small inner diameter so there is a large pressure drop along the line, so the beer will emerge without foaming. It is not much different than balancing a draft system, but your end goal is no foam instead of a desirable amount of foam. Using 10 feet of a small diameter tubing should be enough. The transfer will take a long time with low head pressure and a high impedance line, but that is the price you need to pay to eliminate foaming.

To repeat, I have no experience with spunding, so I am extrapolating from what I do know.
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Offline lupulus

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Re: Spunding process question
« Reply #3 on: May 10, 2024, 02:39:10 am »
You won't have issues.
There will still be positive pressure in the spunding keg in the situation you described.
Transfer at 0C to a 0C receiving vessel, use a spunding valve in the receiving keg (ZERO oxygen in receiving keg).
Note: Many spund in the final keg to ensure zero oxygen.


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Offline Richard

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Re: Spunding process question
« Reply #4 on: May 10, 2024, 10:09:06 am »
Thinking about it a bit more, you don't need to lower the pressure in your fermenter before the transfer. What matters is the pressure difference between the sending and receiving kegs. The pressure will build up in the receiver until it matches the pressure in the sender, at which point the transfer will stop. If you put a spunding valve on the receiver and set it to a pressure slightly below the pressure of the fermenter you will continue to transfer with a small pressure difference. A long line is still helpful for the initial part of the transfer, when the pressure difference is high.

And yes, transferring into a cold receiver also helps with foaming.
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Offline jjflash

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Re: Spunding process question
« Reply #5 on: May 10, 2024, 04:42:40 pm »
I use corny kegs but the concept is the same.
Anytime you transfer carbonated beer foaming will be an issue.
The only question is how badly it occurs.
The whole system needs to be equally CO2 pressurized to minimize foam.

This is my technique:
Check the pressure in the beer corny keg first, lets say 20 psi.
The secondary corny is sanitized and pressurized with CO2 to 20 psi.
A spundig vale is attached to the secondary corny and also set for 20 psi.
The beer is pushed with CO2 at 24 psi from the beer corny into the secondary corny.
I always vent the spundig in a soda bottle with water to monitor the progress of transfer.

Works well for me and minimizes foam.
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Offline erockrph

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Re: Spunding process question
« Reply #6 on: May 11, 2024, 08:04:27 am »
I use corny kegs but the concept is the same.
Anytime you transfer carbonated beer foaming will be an issue.
The only question is how badly it occurs.
The whole system needs to be equally CO2 pressurized to minimize foam.

This is my technique:
Check the pressure in the beer corny keg first, lets say 20 psi.
The secondary corny is sanitized and pressurized with CO2 to 20 psi.
A spundig vale is attached to the secondary corny and also set for 20 psi.
The beer is pushed with CO2 at 24 psi from the beer corny into the secondary corny.
I always vent the spundig in a soda bottle with water to monitor the progress of transfer.

Works well for me and minimizes foam.
Similar process here. I fill the receiving keg with sanitizer, then push it out with CO2 and let the receiving keg pressurize. Then I move my spunding valve to the out post of the receiving keg and keep it set so there's just a bare hiss coming out of it during transfer. There's about a 2-4 PSI difference between the pressure I put on the fermenter and the valve on the receiving keg. That seems to be the sweet spot to allow a reasonable flow rate between the kegs while keeping the beer from foaming up.
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