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Reverse Spunding Valve for Cold Crashing

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agentbud

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If a spunding valve is intended to release excess pressure from a container, would it be possible to do it in reverse to only allow CO2 (from a tank) into the container when a specific negative pressure is reached inside the container during cold crash? Think spunding valve in reverse. Valve is connected to fermentation container and other end of valve is connected to Co2 tank. When negative pressure inside fermentation container reaches the setting on the valve, it opens to allow CO2 in and then closes when pressure is equalized again. Thoughts?
 
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agentbud

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Maybe I am over thinking it then. But a regulator would keep constant pressure in the container, whereas what I explained above would only allow CO2 in when there was negative pressure in the fermenter and then shut it off when equalized. My scenario would assume use of a fermenter not rated to be pressurized so this would help maintain a zero pressure during cold crash.
 

Cptblamo

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The regulator would achieve equilibrium eventually. If u have 30 lbs of pressure, the co2 will fill the head space then start dissolving into the beer. When the beer is carbonated and the keg is full of of co2, it pushes back towards the tank not allowing any more co2 in. Unless u pull the purging valve lowering the pressure of the keg or let beer out creating more headspace allowing more co2 to come in. Is that a good explanation?
 

wsmith1625

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Bleme is correct about a regulator being the reverse of a spunding valve, but if you set your regulator to 0 it's off and won't turn on when internal pressure drops in the fermenter. Check out the Cold Crash Guardian. I thinks it's close to what you're looking for.

 

Brettomomyces

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Maybe I am over thinking it then. But a regulator would keep constant pressure in the container, whereas what I explained above would only allow CO2 in when there was negative pressure in the fermenter and then shut it off when equalized. My scenario would assume use of a fermenter not rated to be pressurized so this would help maintain a zero pressure during cold crash.
Just set it for 1-2 PSI
 

Vale71

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Maybe I am over thinking it then. But a regulator would keep constant pressure in the container, whereas what I explained above would only allow CO2 in when there was negative pressure in the fermenter and then shut it off when equalized. My scenario would assume use of a fermenter not rated to be pressurized so this would help maintain a zero pressure during cold crash.
A fermenter that cannot withstand even minum pressure will probably fare even worse with vacuum.
 

bleme

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If he ferments in a bucket, setting pressure on it would just leak co2 until the tank is empty. This would only work in a pressurized fermenter.
A bucket with a decent gasket can hold 1-2 psi. I do low pressure transfers often. I don't know how much pressure it takes to blow a lid off and spatter the ceiling, but I've done that too....
 

Cptblamo

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There is no reason to connect a co2 tank to a fermenter unless maybe secondary (which would only result in carbonated beer and not cleaner flavor) or like bleme said a pressurized transfer. Fermentation will create enough pressure as it is using "free" co2 from the beer.
 

bleme

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There is no reason to connect a co2 tank to a fermenter unless maybe secondary (which would only result in carbonated beer and not cleaner flavor) or like bleme said a pressurized transfer. Fermentation will create enough pressure as it is using "free" co2 from the beer.
OP specifically mentioned using it for cold crashing. As you chill, it will suck air into the vessel. It is better if you can keep O2 out of that air.
 
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agentbud

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Correct - for cold crashing. To clarify, I ferment in ss brewtech brew buckets which I think are only rated for 1, maybe 2 psi. I was worried that normal co2 regulators are not precise enough to maintain that low pressure during cold crash. I could be wrong or maybe there are some regulators made for lower pressures?
 

Jayjay1976

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Its a small volume of gas that is needed, at a very low pressure. Maybe an 8- or 16-gram CO2 cartridge and mini regulator would be an option? That way you wouldn't risk losing an entire tank of gas if there was a small leak.

OR....fill a balloon with CO2 and attach that to your airlock. Kinda like a suckback guardian only you provide the gas vs. collecting gas from fermentation. As the beer contracts the balloon will deflate, and you can easily add more if it needs topping up to maintain positive pressure. I think a balloon would only provide 1/4 PSI tops, but that is plenty for this purpose.
 

bleme

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My Taprite regulator does 1 psi fine for my purposes but an inline secondary regulator, like the ones from Duotight, might be more reliable for a long-term application like you are talking about. Personally, I used to use a bladder like @wsmith1625 linked, except homemade with a Mylar balloon (and that worked well). Now I crash in the keg, hooked to a CO2 tank, just because it simplified the process for me.
 

Cptblamo

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I'm sorry, I got carried away with myself. Correct me if I am wrong, but the vacuum created during cold crashing is because water molecules contract when approaching freezing. Its somewhere around 1%. Feeding any co2 into the new headspace would make up for the vacuum. As the beer shrinks, the extra co2 will fill the space.
 

bleme

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I'm sorry, I got carried away with myself. Correct me if I am wrong, but the vacuum created during cold crashing is because water molecules contract when approaching freezing. Its somewhere around 1%. Feeding any co2 into the new headspace would make up for the vacuum. As the beer shrinks, the extra co2 will fill the space.
Correct, and the gas in the headspace shrinks even more.
 

Gnomebrewer

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Why not use a spunding valve at 2psi during the tail end of the ferment, then remove it for the cold crash (or just leave it on, even though the pressure will drop below 2psi)?
 
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agentbud

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My Taprite regulator does 1 psi fine for my purposes but an inline secondary regulator, like the ones from Duotight, might be more reliable for a long-term application like you are talking about. Personally, I used to use a bladder like @wsmith1625 linked, except homemade with a Mylar balloon (and that worked well). Now I crash in the keg, hooked to a CO2 tank, just because it simplified the process for me.
I have read that alot of people use a mylar balloon for this purpose but that seems like it takes a little timing. What if you divert the co2 output to the balloon too early - will it eventually pop? What if too late and not enough co2 gets into the balloon to cover the suckback ?
 

day_trippr

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fwiw, I insert an $8 barbecue grill regulator (fixed ~.4 psi) in my fermenter chamber CO2 system for cold crashing. Works perfectly with glass...

Cheers!
 

Jayjay1976

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I have read that alot of people use a mylar balloon for this purpose but that seems like it takes a little timing. What if you divert the co2 output to the balloon too early - will it eventually pop? What if too late and not enough co2 gets into the balloon to cover the suckback ?
Another super cheap option would be to purge and pressurize an empty 2L bottle with a carb cap, and use an in-line regulator set to 1psi.

EDIT: Google says soda bottles can handle ~150 psi. I would pressurize the bottle with my force carbing line which is set at 55psi and call it good. 12 psi serving pressure might even do it.

WTF I'm going to build one myself to expedite closed transfers from my fermenters.
 
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bleme

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I have read that alot of people use a mylar balloon for this purpose but that seems like it takes a little timing. What if you divert the co2 output to the balloon too early - will it eventually pop? What if too late and not enough co2 gets into the balloon to cover the suckback ?
I just filled the balloon off my CO2 tank.
 

Pkrd

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Correct me if I am wrong, but the vacuum created during cold crashing is because water molecules contract when approaching freezing. Its somewhere around 1%. Feeding any co2 into the new headspace would make up for the vacuum. As the beer shrinks, the extra co2 will fill the space.
It's mostly the solubility of the CO2 into the beer increases as the temperature drops. Effectively the CO2 in the headspace is getting sucked into the beer.
 

wsmith1625

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Another super cheap option would be to purge and pressurize an empty 2L bottle with a carb cap, and use an in-line regulator set to 1psi.

EDIT: Google says soda bottles can handle ~150 psi. I would pressurize the bottle with my force carbing line which is set at 55psi and call it good. 12 psi serving pressure might even do it.

WTF I'm going to build one myself to help expedite closed transfers from my fermenters.
Brilliant! Awesome idea. You have to let it's know how it works out.
 

Qhrumphf

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There's a device called a cask breather used in (non-CAMRA approved) cask ale that does exactly what you're looking for. As beer is pulled out (creating a vaccuum) it allows in CO2 to keep the pin/firkin at atmospheric pressure. Normally in traditional cask ale air is pulled in instead. The breather is a means for pubs to extend the shelf life of their cask ale, to the chagrin of real ale puritans.
 

Jayjay1976

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There's a device called a cask breather used in (non-CAMRA approved) cask ale that does exactly what you're looking for. As beer is pulled out (creating a vaccuum) it allows in CO2 to keep the pin/firkin at atmospheric pressure. Normally in traditional cask ale air is pulled in instead. The breather is a means for pubs to extend the shelf life of their cask ale, to the chagrin of real ale puritans.
Well if it has anything to do with real cask ales, it's bound to be quite expensive.

Just googled it, yep, $99 for the regulator, connect it up to your primary regulator set to 5psi and it will maintain several casks.
This would be the most expensive way to go but probably also super reliable.
 

Bobby_M

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A spunding is a pressure regulator. If you had precise regulator with a narrow band gauge, setting it to .25 psi would deal with it in almost any fermenter type.
 
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agentbud

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There's a device called a cask breather used in (non-CAMRA approved) cask ale that does exactly what you're looking for. As beer is pulled out (creating a vaccuum) it allows in CO2 to keep the pin/firkin at atmospheric pressure. Normally in traditional cask ale air is pulled in instead. The breather is a means for pubs to extend the shelf life of their cask ale, to the chagrin of real ale puritans.
Well that looks exactly what I was talking about. Is kinda expensive but considering what we spend in this hobby, its not too bad. Thanks!
 
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agentbud

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I ended up getting a cask breather. Actually, I found a good deal on them from a place in the UK but had to get 5 to make shipping cost effective. Sold 2 already. Still have 2 left that I need to sell if anyone is interested. $65 shipped free to lower 48.
 

oddcopter

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Supposedly, CO2 in a tank is not very pure. So, if you could capture pure CO2 in an external container during fermentation, then reverse your spunding valve, perhaps, this would work. The kegland spunding valves are easily reversible.

I ferment In a Fermzilla and spund the last few gravity points at 15 psi. When I cold crash, the PSI drops just a little. I get carbonated beer and no suck back of oxygen!
 

SanPancho

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Spunding valve is not a regulator. Regulators take upstream flows and limit downstream pressure. Spunding valve limits upstream pressure with no regard to downstream pressure or flow. They’re not the same.

spunding valve is most correctly described as a back pressure regulating /bypass valve. that’s a hint for anyone who wants to find nice used ones on eBay.
 

oddcopter

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What do you mean by that?
I have never done this, but the duotight fittings are easy to disconnect and there is a fitting on both sides, so perhaps, it could be reversed to pull co2 from a container (maybe a balloon) through the diaphragm into the fermenter when cold crashing.

 
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VikeMan

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I have never done this, but the duotight fittings are easy to disconnect and there is a fitting on both sides, so perhaps, it could be reversed to pull co2 from a container (maybe a balloon) through the diaphragm into the fermenter when cold crashing.
If you want to have CO2 that has been collected in a balloon pulled back into the fermenter as pressure drops, you wouldn't want a spunding valve in between. The valve can't pull anything.
 

oddcopter

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If you want to have CO2 that has been collected in a balloon pulled back into the fermenter as pressure drops, you wouldn't want a spunding valve in between. The valve can't pull anything.
The pulling would come from the pressure drop in the fermenter. I'll have to check if the diaphragm opens when pulled rather than pushed. The advantage might be an external source of c02 that is purged and sealed from air and only activated when pressure needs to be equalized, which might be useful in a fermenter that can't handle pressure, like a carboy.

It's probably easier to just hook up a balloon to a blow off tube near the end of fermentation, but I don't see how air doesn't get in.

All of these rigs are pretty wonky.

A pressurized Fermzilla costing $70, or a used keg even less, is so much better. Spund, carbonate, and zero suck back!
 
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