Pressurized Closed Loop Corny Keg Fermenting

[The_Glue]

If someone googles for "oxygen permeability of plastics" or similar search terms you will quickly find that silicone has biggest oxygen uptake (it is pretty much breathing) so i'd suggest retiring our silicone keg o-rings and tubing for maximum LODO effect.

 

[schematix]

and what do you suggest replacing them with?

 

[orangehero]

I don't see any silicone in the OP's setup. It looks like he uses the most common black Buna-N rubber o-rings, which are just fine. They have the lowest permeability of any other common o-ring materials.

http://www.mtm-inc.com/av-20101216-how-to-select-o-ring-materials-for-vacuum-applications.html

 

[The_Glue]

and what do you suggest replacing them with?

Anything else, there is a thread here about o-rings (McMaster Keg O-Ring List) they mention Buna-N (nitrile rubber), my tubes are John Guest LLDPE tubes and something called Lupulus II which is for beer tap systems, made of nylon.

Some sources about silicone having the biggest O2 permeability:

page 4.
page 9.

 

[schematix]

Anything else, there is a thread here about o-rings (McMaster Keg O-Ring List) they mention Buna-N (nitrile rubber), my tubes are John Guest LLDPE tubes and something called Lupulus II which is for beer tap systems, made of nylon.

Some sources about silicone having the biggest O2 permeability:

page 4.
page 9.

As far as I am aware, keg o-rings are not silicone so those should be ok.

Ideally we'd all stop using corny kegs and move to sanke, but that's not realistic for the home brew market right now.

So I guess your suggestion is specific to the materials used during wort production? Best i can find that LLDPE tubing is only good to 150F, so no good for me.

BTW good links. I hadn't seen that one comparing the different closures before, but i had suspected those results when i moved to corny kegs.. it was a major consideration in fact.

 

[The_Glue]

As far as I am aware, keg o-rings are not silicone so those should be ok.

Ideally we'd all stop using corny kegs and move to sanke, but that's not realistic for the home brew market right now.

So I guess your suggestion is specific to the materials used during wort production? Best i can find that LLDPE tubing is only good to 150F, so no good for me.

BTW good links. I hadn't seen that one comparing the different closures before, but i had suspected those results when i moved to corny kegs.. it was a major consideration in fact.

I think the only time this stuff matters is long term storage (fermentation, serving) and probably the small contact area of o-rings with air makes diffusion a non-issue but i have heard about people getting consistently oxidized beer in their tap lines so maybe we should avoid silicon tubes for serving. (my tap line stores about 1/10 litre of beer, but with bigger diameters and longer tap lines for the compensation of the diamter you can easily geet 1-2 litres of beer in there)

I should have worded my first post better, it was more like a general warning for anybody who is interested in eliminating oxygen.

 

[schematix]

I've never heard of silicone tubing being used for bev lines.

 

[Sadu]

Question.

I have recently got on board with this idea of purging a keg using natural fermentation gas, linked somewhere in this thread. I already had a pressure conical so really I just needed an extra keg for this to happen, which I now have.

So I have the fermentor gas port connected to the sanitised empty keg's liquid port. Spunding valve on the keg's gas port set to 5psi, increasing to 15psi later on. The fermentng batch should get me a properly purged keg by the time I'm ready to do a closed transfer.

Now my second fermentor is not pressurised. I rack into kegs the old-fashioned way then purge the old-fashioned way. I was wondering if I could purge the headspace of this full keg in the same way as the empty kegs? Ie connect it to the pressure fermenting batch and let the natural CO2 purge the headspace and maybe even partially carbonate the keg? I happen to have lagers in the pressure fermentor so maybe some of the CO2 would stay in solution at the cooler temperatures?

I'm thinking someone has surely tried this before, for better or worse

 

[Mer-man]

Your problem is not the volume of CO2 available but the time of exposure via partially purged headspace. Not sure you could carbonate that way.

 

[Hannabrew]

Ah, no, kegs (both corny and sanke) have a single, fairly thin, stainless steel wall.

That said, I've just bought a ported Fermonster for closed transfers, because I want to do full 5 gallons into the keg batches.

So while I did get those fermonster lids modded and they work great, I needed an extra fermenter yesterday so I used a corny for the first time.

My question is if blow off gets into the SK, what do you do about it? Just leave it?

 

[schematix]

My question is if blow off gets into the SK, what do you do about it? Just leave it?

I usually backflow it... just blip the FV PRV a little bit and it'll suck it right back to the main. Still closed loop.

 

[SanPancho]

two Qs about process and then one general Q-

so when we are talking about adding sugar/finings/etc to the keg, and going through the PRV hole with a funnel- is there an easy way/trick to do this? or just wrench the PRV out and then quickly screw it back once done? some positive co2 pressure?

and no need for CBC or F2, we are just using the main yeast for carbing?

lastly-

in the event that i have a lager and ale going at same time in same cooler, are the typical 40w fermwraps powerful enough to keep the ale in the upper 60s if the cooler ambient is only low to mid 50s for the lager? i assume i'd need to insulate the ale with reflectix, neoprene, etc. over the fermwrap, but wondering if thats enough or should i try a heating pad with more power. i have the heating pad already, would have to buy the fermwrap.....

 

[schematix]

so when we are talking about adding sugar/finings/etc to the keg, and going through the PRV hole with a funnel- is there an easy way/trick to do this? or just wrench the PRV out and then quickly screw it back once done? some positive co2 pressure?

and no need for CBC or F2, we are just using the main yeast for carbing?

I hook up co2 at a pressure of about 5 psi for positive pressure. I then use a large 100mL syringe to inject the solution. The PRV can be unscrewed with your fingers, definitely don’t wrench it.

And the yeast in the keg is enough. No additional bottling yeast needed.

 

[daveMN]

I'm finally getting around to setting this up and have a couple of questions:
1. When you water purge your kegs, do you deaerate or scavenge the water first? There isn't much left in the keg, granted, but it seems like a potential oxygen source. I've been using StarSan for my keg purges.
2. My fermentation chamber isn't big enough for two kegs, so before I drill a hole through the side of it, what pressure should I have the SK set to, given the different volume and temperature compared to the FV headspace and lower fermentation temp?
Thanks!

 

[schematix]

I'm finally getting around to setting this up and have a couple of questions:
1. When you water purge your kegs, do you deaerate or scavenge the water first? There isn't much left in the keg, granted, but it seems like a potential oxygen source. I've been using StarSan for my keg purges.

Very good point. I probably should, but i don't. Boiling that much water is just way too much time/effort/energy, even for me. I also spund so i get active scavenging, which is perfect for that.

I have recently considered is adding sulfites to the water. I just need to calculate how much and i'll probably do it next time or two.

2. My fermentation chamber isn't big enough for two kegs, so before I drill a hole through the side of it, what pressure should I have the SK set to, given the different volume and temperature compared to the FV headspace and lower fermentation temp?
Thanks!

I'd probably do the same "few psi". Once you rack to the SK and spund that keg then i'd go by the standard co2 volumes/temperature/pressure charts.

 

[daveMN]

Thanks! That was easy! Just need one of those cool thermowell corny lids. :beer:

View attachment 1510627368827.jpg

 

[cheesebach]

Thanks! That was easy! Just need one of those cool thermowell corny lids. :beer:

Just to get a better reading of the liquid temp? I think a nice bonus of fermenting in a keg (or any stainless fermenter) vs. a plastic fermenter is that you can get an accurate reading of the liquid temp externally for free since steel is a much better conductor of heat than plastic. I just put a blob of plumbers putty to shield the temperature probe from the ambient air, and if there is any difference between the actual temp of the liquid and what the probe reads, it’s a couple tenths of a degree at most.

 

[schematix]

I just put a blob of plumbers putty to shield the temperature probe from the ambient air, and if there is any difference between the actual temp of the liquid and what the probe reads, it’s a couple tenths of a degree at most.

When i tried to insulate the probe on the outside of the keg it was a couple degrees different than the thermowell probe registered. It was warmer in the thermowell than the external probe registered. Greatest difference was during peak fermentation and got lesser as fermentation progressed.

Better than nothing for sure, but it's much more stable in the thermowell. Consequently the compressor cycles less too.

 

[cheesebach]

When i tried to insulate the probe on the outside of the keg it was a couple degrees different than the thermowell probe registered. It was warmer in the thermowell than the external probe registered. Greatest difference was during peak fermentation and got lesser as fermentation progressed.



Better than nothing for sure, but it's much more stable in the thermowell. Consequently the compressor cycles less too.

Using bubble wrap or something like plumbers putty? I’ve been skeptical of how good a job bubble wrap can do unless its taped up really well to seal in the probe from any outside air. With a big blob of putty on the side (facing away from the walls of the freezer), I’ve had to lower my hysteresis down to 0.2F, or my compressor isn’t even coming on once an hour during fermentation. Even at 0.2F, it takes a good 10-15 minutes of run time to come back down to target and another 30-60 minutes to rise back up. With my plastic Speidel, hysteresis is usually set to 1F, and this still seems to cycle more often than 0.2F with the keg.

 

[Bigdaddyale]

sub

 

[schematix]

Filled lager fermenter. Removed gas posts and installed blow off. Working well. Don’t be scared to fill these up when doing lagers and using a blow off early.


View attachment 420599

I pitched another 500mL of yeast to this too.

 

[daveMN]

I think I just learned that a spund valve is key to this process. And I don't think I put enough Fermcap in the FV keg. Luckily I have a couple extra fully purged kegs handy. And yes, a spund valve is my next purchase!

 

[schematix]

Yah spunding is one of the most highly underrated processes in home brewing. So many advantages.

I'm becoming less of a fan of it early in fermentation though. I find it easier just to blow off and once things calm down, then spund.

 

[Sadu]

Spunding is awesome. Does great things for lagers IMO and I love using the fermentation gas to purge the keg properly and for free. I brew up to 32L in a 35L vessel and have been starting off at 5psi to compact the krauesen, otherwise blowoffs happen. What are your thoughts against using mild pressure at the start of fermentation?

 

[daveMN]

Yah spunding is one of the most highly underrated processes in home brewing. So many advantages.

I'm becoming less of a fan of it early in fermentation though. I find it easier just to blow off and once things calm down, then spund.

I'm still impressed with how much CO2 fermentation kicks out. A bubbling airlock doesn't show it like a climbing pressure gauge.

I'm thinking about putting two kegs in series, the first one to catch the blow off, and spund with the second. What's one more keg to clean, right?

 

[schematix]

What are your thoughts against using mild pressure at the start of fermentation?

The only reason I have recently stopped doing pressure early in the ferment is that i've been traveling a lot M-F, and i'm terrified of leaving something like that unattended. With a blow off tube i know when i come back a few days later that it'll then be time to spund and start building pressure. That coupled with the fact i've been filling the kegs more and more full each time increases the risk of a clog in the gas QD and a big mess.

I'm thinking about putting two kegs in series, the first one to catch the blow off, and spund with the second. What's one more keg to clean, right?

Probably easier and cheaper to get something like a filter housing.

 

[Sadu]

@schematix (sorry having trouble figuring out this new quoting thing)

I gather you are using a spunding / aka variable pressure relief valve on your empty keg, but you are saying that if the gas line in the fermenting keg gets blocked you end up with potential for 100 psi and at best a wrecked batch?

That's something I haven't considered. I have a bit more headspace in my fermentor, and the pressure works to keep the head nice and small.

 

[schematix]

but you are saying that if the gas line in the fermenting keg gets blocked you end up with potential for 100 psi and at best a wrecked batch?

My concern lies more in the gas post poppet and the QD poppet than in the keg itself. Those pieces have very small cross section and they are also not smooth, so are just asking for something to get stuck. I really try to max out the keg volume (i'm currently going above the top weld by about 1/2" so it's virtually guaranteed something is going to come out the gas port.

In a perfect world i'd have more head space and i'd just let it stay pressurized the whole time. But for right now i'm just throwing a blow off tube on for a few days, then once the highly active fermentation is done, i snap on the adjustable pressure relieve valve.

 

[stonebrewer]

Time for a dumb idea...feel free to tell me what I am missing:

Setup - I have a Zymatic, so I do smaller 3 gallon batches. Keep that in mind. Means a lot more headspace in the keg and thus a lot more oxygen, so I have to purge the kegs of O2 or the batches get brown in a week or less. I ferment under pressure with a spunding valve and have regularly kept it set at 20 PSI without any issues. Fermentation is usually done in about a week. I have a clear draught system in my serving keg with a stainless screen I designed/built over the intake.

Here's the idea - instead of (or in addition too?) water purging the serving vessel, why not just push a half gallon or so over from the FV while at peak fermentation? Yeast move over with some wort, eat all the O2, and Bob's your uncle? I am a firm believer of the KISS principle (yeah, even though I am a DIY homebrewer!) and it seems to me that this might work well. What am I missing here? Could even work for the times when I use my larger system for 5 or 10 gallon batches.

 

[schematix]

Time for a dumb idea...feel free to tell me what I am missing:

Here's the idea - instead of (or in addition too?) water purging the serving vessel, why not just push a half gallon or so over from the FV while at peak fermentation? Yeast move over with some wort, eat all the O2, and Bob's your uncle? I am a firm believer of the KISS principle (yeah, even though I am a DIY homebrewer!) and it seems to me that this might work well. What am I missing here? Could even work for the times when I use my larger system for 5 or 10 gallon batches.

You are thinking in the right direction!

Perhaps here's an easier way to execute though:

1. Water purge serving keg.
2. Ferment as usual in standard corny fermentation vessel, using whatever pressure you like and have success with.
3. When you are about 4 gravity points above final gravity, rack to the serving keg using the closed loop transferring method, being sure to CO2 purge all your lines. To do this you'll need to perform a force ferment test.

a. To do the FFT, when you see signs of fermentation (lots of gas), pull a sample through the liquid dip tube, approx 150mL, into a container. Put this in a warm place on a stir plate and let it run to FG. This should ideally finish before the main batch. You want to rack roughly 4 gravity points above FG, so monitor your main batch.​

4. Seal the serving keg and allow to come to desired pressure/carbation level. Attach spund valve if pressure is too high.

The yeast still being active when you rack is your protection against oxygen in the second keg. If you miss the window to rack at FG+4, don't worry. Make up a small amount of priming solution, roughly 2:1 by weight of water to sugar, boil it, and inject it through the FV keg's prv while you are applyign gas pressure to the gas side. If you do this with a day or two of reaching final gravity it'll start bubbling away within the hour. Then rack it.

It's a bit of a pain if you miss the window but i've had great success with priming that way. The key is to get it out of primary the moment its ready.... no 28 days on the cake! You're looking at 2-5 days for ales and 5-10 days for lagers depending upon some other variables.