Purging keg with CO2 from fermentation: liquid or gas post?

[TheMadKing]

Trust me, these kegs are truly gas tight. I was going light on your proposition...

Cheers!

What does that mean? I'm 100% correct about my own kegs. It sounds like yours behave quite differently.

Mine most definitely leak without pressure, so maybe I'm doing something wrong and have the wrong o rings in there, or maybe it's just pin locks?

Some of my lids have actually been dented and bent and I had to do my best to straighten it them before I could get a seal at all

 

[day_trippr]

No doubt the key difference is the condition of your kegs vs mine. As I mentioned I have one keg that has a sealing issue and it's because the lid opening is distorted from mishandling by some former owner. Otoh, the other fifteen have by any measure perfect fits with their lids and with a film of silicone lube on the lid gaskets are tight with just the pressure of the bail.

This really shouldn't be that hard to comprehend. Do you think every cornelius keg is afflicted like yours from birth?

Cheers!

 

[Deadalus]

Hey I had two thoughts regarding the 3 fl. oz air that can't get out of the lid. May have already been covered. First thought was, could you fill the keg up with water inside a clean garbage can or other vessel filled with water? Starsan could be injected later. Or second thought, how about filling the lid with water (upside down) and freezing it?

 

[Carolina_Matt]

What does that mean? I'm 100% correct about my own kegs. It sounds like yours behave quite differently.

Mine most definitely leak without pressure, so maybe I'm doing something wrong and have the wrong o rings in there, or maybe it's just pin locks?

Some of my lids have actually been dented and bent and I had to do my best to straighten it them before I could get a seal at all

Most of my kegs seal fine, but I have a 2 gallon keg that refused to seal. I switched orings, tried silicone, and it didn't work. Bought an oversized oring from Williams and it seals perfectly. They're more expensive than regular orings, but it was well worth it for me.

 

[TheMadKing]

Most of my kegs seal fine, but I have a 2 gallon keg that refused to seal. I switched orings, tried silicone, and it didn't work. Bought an oversized oring from Williams and it seals perfectly. They're more expensive than regular orings, but it was well worth it for me.

Thanks, I'll give that a try

I honestly thought everyone had this problem and never knew this was abnormal until this conversation

 

[TheMadKing]

No doubt the key difference is the condition of your kegs vs mine. As I mentioned I have one keg that has a sealing issue and it's because the lid opening is distorted from mishandling by some former owner. Otoh, the other fifteen have by any measure perfect fits with their lids and with a film of silicone lube on the lid gaskets are tight with just the pressure of the bail.

This really shouldn't be that hard to comprehend. Do you think every cornelius keg is afflicted like yours from birth?

Cheers!

I don't appreciate nor do I deserve the condescending tone you've assumed, nor the insults to my intelligence. I'm asking an honest question and trying to have a conversation here. Please enhance your chill.

Having never used anyone else's kegs except for my own, I have no frame of reference from which to base any other opinion. So yes, I believed (apparently erroneously) that all corny kegs cannot be sealed without pressure applied as a byproduct of their design, since I have had no experience that demonstrated otherwise to me.

The simple fact that I have this issue though, should tell you that the advice to use fermentation CO2 will not work equally well for everyone, so that might be something to consider adding to any future advice to do so. It sounds like it works very well IF you have corny kegs that properly seal without any pressure inside (though I don't necessarily know how you can prove this, since you need pressure to do a bubble test).

 

[SanPancho]

Thanks, I'll give that a try

I honestly thought everyone had this problem and never knew this was abnormal until this conversation

It’s not you. Some of my kegs seal on their own, most don’t.

there’s no reason to stop using ferm gas to purge, even for your English stuff. pretty much any commercial ferm over 10bbl is gonna have 2-3-4-5 psi pressure on it just from hydrostatic. If the 2 or 3psi needed to seal your keg killed your esters then just build them back up. you can warm the temp, decrease the pitch rate, don’t oxygenate, add a lot of zinc/nutrients, or start warm then finish cool. For simplicity I’d set your ferm temp based on esters as opposed to the yeasts “preferred” temp range.

also id Point out that for anyone fermenting under pressure, we’re losing co2 blow off by sealing the ferm and spunding. somebody would have to do the calcs but if that gas is still in ferm it’s not available to purge the keg. The higher the pressure the less purging you get. Not sure how significant but it definitely made me stop and think the last ferm I did under pressure. Maybe a sanitizer fill might be necessary when spunding.

lastly I think this 3oz of air trapped in lid space is overestimated. you fill the keg to the rim. Then you hit te poppets to let water into your gas/beer lines. Add bit more water, filling back up to rim. Now putting in your lid requires it to be slid in vertically, which is to say at least 50% of this “under the lid” area is below the water line. Probably closer to 2/3. I’d wager it’s more like 1oz, 1.5 at most if you fill and seal this way.

 

[day_trippr]

I don't appreciate nor do I deserve the condescending tone you've assumed, nor the insults to my intelligence. I'm asking an honest question and trying to have a conversation here. Please enhance your chill.

Seriously? You argued against everything I related about MY KEGS like you knew what you were talking about...

 

[TheMadKing]

Seriously? You argued against everything I related about MY KEGS like you knew what you were talking about...

My very first post directed to you said "my experience has been the opposite" and then I proceeded to relate my experience. I never argued that you were wrong or that it wasn't working for you, but I did put forward a counterpoint to your "proof" of lid sealing since I don't agree that it empirically shows that you have zero air diffusion in through your lid.. maybe a simple misunderstanding here?

My first post on this thread was directed at island lizard and included my erroneous assumption that all kegs require pressure to seal. Thank you for educating me otherwise. I then asked a couple questions about how you all are doing it, which you have also answered, so thank you.

I came here to learn my friend, not sure what I've done wrong here

 

[Red over White]

Hey I had two thoughts regarding the 3 fl. oz air that can't get out of the lid. May have already been covered. First thought was, could you fill the keg up with water inside a clean garbage can or other vessel filled with water? Starsan could be injected later. Or second thought, how about filling the lid with water (upside down) and freezing it?

Freezing the lid full of starsan/sani clean is a truly genius idea! Kudos

 

[OakIslandBrewery]

Interesting thread - I learned a long time ago to jack up the CO2 pressure to seal the keg lid and that's what I still do. I figure it's good insurance, perhaps not needed as I see by some here.

It's all about sharing and learning, yes that's why I come to this site too!

 

[Deadalus]

Freezing the lid full of starsan/sani clean is a truly genius idea! Kudos

Thanks! I wasn't exactly thinking of freezing the Starsan too but that might be workable. I don't know Starsan's freezing point, I had in mind to just add it afterwards in the large vessel case. It could be added to the water already in the keg in the freezing lid idea. I was trying to think of a liquid that freezes around the temps of water that would be food safe because water expands when it freezes so it would contract when melting. I don't see it as an issue given the small volume, the keg is closed so the pressure might drop ever so slightly.

 

[AlexKay]

Whether or not pushing sanitizer out with CO2 results in lower O2 depends on whether you use bottled CO2 or fermentation CO2 to push.

Bottled CO2 is less pure (has higher O2 contamination) than fermentation produced CO2. Bottled CO2 is only guaranteed to have less than 30ppm of O2, but is usually much less (more like 50ppb [0.05ppm].) When purging with bottled CO2, the O2 level cannot be driven lower than the O2 content of the CO2 doing the purging. Therefore, if you purge with bottled CO2, you can’t get lower final O2 than 50ppb, or more.

If you push sanitizer out with fermentation CO2, then you will end up with even lower O2 than if you start with an air filled keg. But since even an air filled keg gets below 5ppb (the analysis was pessimistic, and measured results are even better than predicted) there is no need to worry about it. It won’t hurt anything to fill the keg with sanitizer first, but the improvement will be insignificant.

Brew on

I think we've been here before, but if bottled CO2 is 30 ppm O2, that's by volume (or number, same thing.) Concentration of O2 in beer is by weight (1 ppm = 1 mg O2(aq)/kg).

If the CO2 is 30 ppm O2, then pressurizing a tank to 2 bar with this CO2/O2 mixture (if my back-of-the-envelope calculation is right) gives about a milligram of O2 in a 5-gallon tank. A milligram of O2 in 5 gallons of beer is roughly 50 ppb by weight. That's at or below the threshold professionals will aim for.

But you don't need to worry about a full 5-gallon tank of gas, you need to worry about the headspace. Say that's a liter, and the rest of the gas is displaced when you fill it with beer. That liter of headspace has about 50 micrograms of O2(g) in it, which when it fully dissolves into and reacts with your beer (not when it comes into equilibrium through Henry's Law, that's much less O2(aq)), is the equivalent of about 2.5 ppb total oxygen, which is a ridiculously low level, almost certainly less than you've introduced in other steps of the process.

TL; DR: if your tank CO2 is at 30 ppm O2, you have nothing to worry about ...

... as long as you can effectively purge your keg with it. This is not easy in practice. Filling with liquid and pushing out, you're limited by the unavoidable air-filled headspace (even a few milliliters maters), and @doug293cz has already shown it's not straightforward with pressurize-vent cycles. But impurities in the tank are never the problem. (Edit: provided that you're in fact at that 30 ppm level.)

 

[belgabrewing]

Most of my kegs seal fine, but I have a 2 gallon keg that refused to seal. I switched orings, tried silicone, and it didn't work. Bought an oversized oring from Williams and it seals perfectly. They're more expensive than regular orings, but it was well worth it for me.