Fermenting in a corny keg?

[dsdunbar]

@McKnuckle @moreb33rplz
Follow up question: I have finally setup the corny kegs as primary fermentors and am using a spunding valve. I brewed a pale ale on 4/10/2021 and have active fermentation going on (the pressure is higher than when started). The question is, the spunding valve is releasing the gasses as it exceeds the set pressure (which is around 12psi), do I need to be pushing that CO2 into a starsan solution blowoff setup? I think the spunding valve protects me from sucking air back into the keg (plus it should always have a positive pressure on the inside of the keg, so no back suction). When I open my converted fridge to fermentation chamber door I can get a pleasent smell of the off gassing. Does this seem like an acceptable way forward (to let it vent to the interior of the chamber)? I know I could try to capture the CO2, but my space is really limited to put in another vessel. See pictures.

Bit more information:
Hi All, So I appreciate the guidance you all provided for my questions back in Nov of 2020. I brewed my first 10 gal batch in January and decided to stick to the fermenting buckets for that batch (minimize the amount of new things, brewing AG fr the first time was enough newness). Fast forward to April 10 2021 and my friend and I just brewed a pale ale, and I am attempting the corny keg fermentation.

I am using three kegs for the batch size was 13 gallons, so roughly have the following volumes for 3 kegs: 4.5, 4.5, and 3 gallons.

I used my CFC to get the temp down to 70F in each vessel and then pitched my yeast, and closed the kegs up, hit it with CO2 and bled the air out through the Pressure relief valve. I put 12 psi of CO2 in each keg, attached a blowtie spunding valve, and have the kegs stored in a fridge converted to fermentation chamber with temp set to 70F.

After 24 hours it is apparent that the yeast is doing its thing, the pressure climbed in each vessel (I have had to manually adjusted the spunding valves to try and keep the pressure close to 12 psi, for the pressure had risen to 18psi in two of the kegs, the third I suspect had a slow leak so I took care of that and it rose to 15 psi).

So here are pictures, I didnt take any pictures of the corny kegs interior (with the fine mesh Hop cylinder as a filter around the pick up tubes, but it looks the same as McKnuckle showed in his pics (for I copied based on his pics).

 

[VirginiaHops1]

Follow up question: I have finally setup the corny kegs as primary fermentors and am using a spunding valve. I brewed a pale ale on 4/10/2021 and have active fermentation going on (the pressure is higher than when started). The question is, the spunding valve is releasing the gasses as it exceeds the set pressure (which is around 12psi), do I need to be pushing that CO2 into a starsan solution blowoff setup? I think the spunding valve protects me from sucking air back into the keg (plus it should always have a positive pressure on the inside of the keg, so no back suction). When I open my converted fridge to fermentation chamber door I can get a pleasent smell of the off gassing. Does this seem like an acceptable way forward (to let it vent to the interior of the chamber)? I know I could try to capture the CO2, but my space is really limited to put in another vessel. See pictures.

Spunding valves are sealed and can only release pressure. No air entering backwards. I generally let my keg fermentations go for a couple days in the blow off jar then put the spunding valve on inside my fermentation fridge

 

[dsdunbar]

Spunding valves are sealed and can only release pressure. No air entering backwards. I generally let my keg fermentations go for a couple days in the blow off jar then put the spunding valve on inside my fermentation fridge

Thanks, I've done a bit of reading of doing primary fermentation under pressure (like 12psi), I decided to take that route, I know for some styles it is not advised but my understanding is for hoppy beers it helps with minimizing esters. Is there a reason you do not ferment underpressure to start? Just curious for this is all very new...

 

[VirginiaHops1]

Thanks, I've done a bit of reading of doing primary fermentation under pressure (like 12psi), I decided to take that route, I know for some styles it is not advised but my understanding is for hoppy beers it helps with minimizing esters. Is there a reason you do not ferment underpressure to start? Just curious for this is all very new...

I do primarily all hoppy beers and select my yeast based on the characteristics I want in that beer and ferment them within their optimum temp ranges. So I don't really feel the need to suppress anything. I guess if you're fermenting warmer than usual and you may get undesirable esters or something I could see it. I've heard of people fermenting lagers under pressure so they could go warmer without off-flavors. If it works for you though have at it

 

[mattman91]

Has anyone fermented in a keg and just left the standard dip tube in without cutting/bending/replacing with a floating dip tube?

Would the trub cause the flow to not start, or would it just blast the trub out, then to the clean beer?

 

[VirginiaHops1]

Has anyone fermented in a keg and just left the standard dip tube in without cutting/bending/replacing with a floating dip tube?

Would the trub cause the flow to not start, or would it just blast the trub out, then to the clean beer?

I think there's a very good chance you'll get a clog. Nothing worse than having a clog and having to open up the fermenter totally negating the whole point of fermenting in the keg to limit O2. I would either use the floating dip tube or cut the reg dip tube slightly and put a filter around it. I use one of those hop canisters.

 

[cmac62]

Has anyone fermented in a keg and just left the standard dip tube in without cutting/bending/replacing with a floating dip tube?

Would the trub cause the flow to not start, or would it just blast the trub out, then to the clean beer?

there is a long thread have you tried fermenting and serving from the same keg without transferring? about fermenting and serving in the same keg. I haven't yet tried it, but it seems to work both ways according to folks on the other thread.

 

[odie]

Has anyone fermented in a keg and just left the standard dip tube in without cutting/bending/replacing with a floating dip tube?

Would the trub cause the flow to not start, or would it just blast the trub out, then to the clean beer?

Nope...You just get a yeast harvest in your first pint. But it's best to filter/screen your wort from kettle to keg so you get max yeast cake and minimal trub.

 

[odie]

Thanks, I've done a bit of reading of doing primary fermentation under pressure (like 12psi), I decided to take that route, I know for some styles it is not advised but my understanding is for hoppy beers it helps with minimizing esters. Is there a reason you do not ferment underpressure to start? Just curious for this is all very new...

I've found that lagers are fine under pressure from the start...not huge pressure but just a few PSI...5/10/15 something like that is probably fine.

I've found that ales do not produce the desired "yeast expressions" (especially hefe) under pressure...so use a blow off tube first. When it slows and is winding down, remove blow off tube and seal/spund for the finish.

 

[mattman91]

Nope...You just get a yeast harvest in your first pint. But it's best to filter/screen your wort from kettle to keg so you get max yeast cake and minimal trub.

Very interesting..I may try this next time. I usually filter from my kettle to the keg already.

The only other concern I would have is that it might gunk up the dip tube/beer line causing several pours to be yeasty. Maybe pour the first pint or two from a picnic tap?

 

[rkhanso]

Question - is it generally bad practice to use an iSpindel when pressure fermenting in a corny keg? I'm thinking for two reasons (one catastrophic).
1. The iSPindel can't take the pressure and will fill up with beer and contaminate the beer.
2. The WiFi signal can't penetrate the Stainless Steel keg to talk to my Fermentrack controller.

 

[RyPA]

I did this for the first time last month with success. Recommend floating dip tube, spunding valve, and magnets. Here's the thread if you want to take a look. The keg didn't stand a chance once tapped, already kicked.

https://www.homebrewtalk.com/threads/upcoming-single-hop-neipa-brew-day.697951/

 

[Ki-ri-n]

Question - is it generally bad practice to use an iSpindel when pressure fermenting in a corny keg? I'm thinking for two reasons (one catastrophic).
1. The iSPindel can't take the pressure and will fill up with beer and contaminate the beer.
2. The WiFi signal can't penetrate the Stainless Steel keg to talk to my Fermentrack controller.

I ferment in cornies within iSpindel. It works just fine, except I needed to add a a repeater to get the signal back to the router.
I pressure ferment too. I had one seep a little bit, the other was just fine. I only let it get to 10-15 PSI. Haven't tried higher yet. It might depend on the pelting being used. Some also try to add an o-oring to help seal it.

 

[Cider Wraith]

Or, you can capture fermentation CO2 in a second keg, either with spunding to retain pressure or with the blow-off on the second keg. Either way, it will purge that keg easily. Then you can transfer from the ferment keg into the serving keg with no oxygen exposure

Ah - ingenious ... if intending to transfer, let the fermenting keg vent through the serving keg to mostly purge air with C02 without running down a tank - nice

 

[BongoYodeler]

Wow!! Nearly three years since I started this topic and I still haven't fermented in a keg.
But...I think I'm going to give it a go with my next brew. Does anyone reading this know if 4.5 gallons of fermenting beer in a keg will CO2-purge two other 5 gallon corny kegs set up in a chain? I have an experiment I want to try using three kegs.

 

[RyPA]

Wow!! Nearly three years since I started this topic and I still haven't fermented in a keg.
But...I think I'm going to give it a go with my next brew. Does anyone reading this know if 4.5 gallons of fermenting beer in a keg will CO2-purge two other 5 gallon corny kegs set up in a chain? I have an experiment I want to try using three kegs.

It's the only way I brew anymore, you have to try it.

 

[VirginiaHops1]

Wow!! Nearly three years since I started this topic and I still haven't fermented in a keg.
But...I think I'm going to give it a go with my next brew. Does anyone reading this know if 4.5 gallons of fermenting beer in a keg will CO2-purge two other 5 gallon corny kegs set up in a chain? I have an experiment I want to try using three kegs.

People here have posted the math related to the amount of CO2 created in a fermentation and it seems plenty sufficient to purge 2 kegs. I often have 2 kegs(dry hop keg, serving keg) daisy chained to my ferm keg to be purged and it seems to work fine

 

[Grizwold1]

Watch this space. Imma write a epic response that will leave you amazed and enthused (or dazed and confused , or just whatever ... )

Stay tuned

Brew on

============================================================================

Ok, you've waited long enough, here is my analysis of the OP's questions. You be the judge, is it epic or not? Worth the wait, or a big let down?

Pull up your waders, it's gonna get deep here. You might want to take this on while drinking coffee rather than beer.

============================================================================

Let's break this down into manageable pieces, and then look at them one at a time.

First question: Does the continuous flow of CO2 from the fermenter create any different dilution kinetics than the typical multiple cycles of pressurize then vent?

When we pressurize the headspace of a keg we produce a burst of CO2 gas originating at the gas in tube. This burst creates turbulence in the headspace which very effectively mixes the starting headspace gas and the added CO2. We can safely assume that the gases are well mixed prior to the vent cycle. This means we can use static, or equilibrium, math to determine the amount of dilution. We want to know solute concentration in a solution when additional diluent is added to a solution. In our case the solution is a gas solution, the solute is oxygen (O2), and the diluent is CO2. For one dilution (purge) cycle, the change in solute concentration is:

New_Conc = Prev_Conc * Starting_Amount / (Starting_Amount + Diluent_Amount)​

When working with gases in fixed volume vessels, the "amount" of gas is proportional to the absolute pressure (psia), and absolute pressure equals gauge pressure (psig) plus atmospheric pressure (14.695 psia at sea level.) This follows from the universal gas law: PV = nRT. Thus the original "amount" of gas is 14.7 psia, and the diluent amount of gas is the pressure that we add to the keg, so the dilution per cycle becomes:

New_O2_Conc = Prev_O2_Conc * 14.7 psia / (14.7 psia + Purge_Pressure)​

After we pressurize for the purge, we still have the same amount of O2 in the headspace that we started with, but the concentration is lower. Once we vent the headspace, the pressure drops back to 14.7 psia, and we have less total gas than we had before. Venting doesn't change the O2 concentration in the headspace, but since it does reduce the total amount of gas in the headspace, the amount of O2 goes down as well. The pressurize part of the purge cycle reduces the O2 concentration in the gas mix, and the venting then reduces the O2 amount. The effect of additional purge cycles is multiplicative, so the formula for multiple purge cycles is:

Final_O2_Conc = Orig_O2_Conc * (14.7 / (14.7 + Purge_Pressure)) ^ N​

Where N = number of purge cycles​

The O2 concentration in air is 21% or 210,000 ppm. If we assume that the keg headspace starts out as air, then we can calculate and plot the resultant headspace O2 concentration for various numbers of purge cycles at different pressures.

View attachment 402029

View attachment 402030

So, what happens if instead of doing pressurize/vent cycles, we flow CO2 into a vessel that originally contains air? Does the flow improve the dilution and removal efficiency of O2 compared to the cyclic process? We can argue that if the CO2 inflow is fast enough that CO2 comes in faster than it can mix with the air, then it could form a sort of gas piston that would push air ahead of it towards the vent, and that this would push out more O2 per volume of CO2 than if complete mixing of incoming CO2 and existing gas occurred (as it does in the pressurize/vent case.)

The best case for non-mixing of CO2 and headspace would be if there were absolutely no internal "air" currents, such that the only mixing of CO2 with headspace gas would be via diffusion. So the question comes down to: Is the linear CO2 flow rate faster than the diffusion velocity of CO2 in air? If the CO2 flow rate were much faster than diffusion, then mixing would be limited, and continuous flow would be more efficient than purge/vent. If CO2 flow rate were much slower than diffusion, then gases would be mostly mixed, and continuous flow would not be any more efficient than pressurize/vent. If the flow rate and diffusion rates were of the same order of magnitude, then there would be significant, but not complete, mixing, making this the most complex scenario to analyze.

To start we need to get an estimate of the diffusion velocity of CO2 in air. If we limit our analysis to one dimensional flow (say from bottom to top of a keg, uniform velocity across the width), things will be much simpler, but still valid. Fick's first law of diffusion is (ref: Diffusion - Wikipedia):

Flux = -D * (𝚫Conc / 𝚫Dist)​

Where Flux is in mass/area-time,​

D is the diffusion coefficient, and​

𝚫Conc / 𝚫Dist is the concentration gradient​

If we divide Flux [mass/area-time] by density [mass/volume] we get linear velocity [dist/time] which is what we are looking for.

The diffusion coefficient for CO2 in air is about 0.15 cm^2/sec (ref: Oxygen Diffusion/Air - Cornell Composting) Now if we make some assumptions about gradients we might encounter, we can estimate a linear CO2 flow rate due to diffusion. We will use approximate numbers for simplicity, since we are only looking for order of magnitude estimates of velocity.

A corny keg has a volume of about 20 L or 20,000 cm^3, and a height of about 55 cm, leaving a cross sectional area of about 20,000 cm^3 / 55 cm = 364 cm^2. The density of CO2 at STP is about 2 g/L or 0.002 g/cm^3 (ref: Gases - Densities.) If we assume 2.5 cm of pure CO2 at the bottom of the keg, and 2.5 cm of air at the top of the keg, and a uniform concentration gradient from the bottom to the top, the CO2 gradient becomes:

𝚫Conc / 𝚫Dist = (0 - 0.002 g/cm^3) / 50 cm = -4.0e-5 g/cm^4​

The CO2 flux becomes:

Flux = -D * (𝚫Conc / 𝚫Dist) = -0.15 cm^2/sec * (-4.0e-5 g/cm^4) = 6.0e-6 g/cm^2-sec​

And finally the linear velocity of CO2 due to diffusion is:

CO2_Diffusion_Velosity = CO2_Flux / CO2_Density = 6.0e-6 g/cm^2-sec / 0.002 g/cm^3 = 0.003 cm/sec​

Next we need to determine the linear flow velocity of CO2 being fed through a keg from an active fermentation.

The reaction for fermentation of maltose is:

Maltose + H2O --> 2 Dextrose --> 4 Ethanol + 4 CO2​

Maltose has a molecular weight of 342.30 g/mol and CO2 has a molecular weight of 44.01 g/mol, so each gram of maltose fermented generates 4 * 44.01 / 342.3 = 0.5143 gram of CO2. So, if we determine how much sugar we ferment over what period of time, we can calculate how much CO2 we created and calculate an average flow rate over the cross section of a keg.

Let's work an example assuming 20 L of wort with an OG of 1.050 that achieves 80% apparent attenuation over a four day fermentation. First we have to determine how much sugar we started with. An SG of 1.050 is equivalent to 12.39°Plato, or 12.39% sugar by weight. To convert SG to plato use the following formula (ref: Brix - Wikipedia):

°Plato = -616.868 + 1111.14 * SG - 630.272 * SG^2 + 135.9975 * SG^3 @ 20°C​

Water at 20°C has a density of 0.9982 kg/L, so the weight of 20 L of wort @ 1.050 is:

20 L * 1.050 * 0.9982 kg/L = 20.96 kg​

This wort is 12.39% sugar by weight, so the weight of sugar is 2.597 kg. At 80% apparent attenuation, this beer would have an FG of 1.010, or 2.561°Plato. Since the presence of alcohol affects the SG the actual attenuation of the beer is lower (the final °Plato is higher), we must correct the final °Plato using the Balling approximation (ref: https://byo.com/hops/item/408-calcu...ion-extract-and-calories-advanced-homebrewing):

Real_Final_°P = Apparent_Final_°P * 0.8114 + Original_°P * 0.1886​

And, plugging in the numbers for our example:

Real_Final_°P = 2.561 * 0.8114 + 12.39 * 0.1886 = 4.415°P​

Thus the finished beer contains 4.415% by weight of sugar, which works out to:

Final_Sugar_Weight = 20 L * 1.010 * 0.9982 kg/L * 0.04415 = 0.890 kg​

The total sugar fermented works out to:

Fermented_Sugar_Weight = 2.597 kg - 0.890 kg = 1.707 kg​

And the total weight of CO2 created works out to:

CO2_Weight_Created = 1.707 kg_Maltose * 0.5143 kg_CO2/kg_Maltose = 0.878 kg or 878 g of CO2​

Since CO2 has a density of about 2 g/L, we created about 439 L or 439,000 cm^3 of CO2.

If we push our CO2 through the keg at a constant rate over a four day fermentation, the flow rate of the CO2 over the 364 cm^2 cross section of the keg works out to:

​

CO2_Velocity = 439000 cm^3 / (4 days * 24 hr/day * 3600 sec/hr * 364 cm^2) = 0.0035 cm/sec​

Damn, that works out almost the same as our diffusion velocity of 0.003 cm/sec. So, we are in the complex, hard (i.e. infeasible) to analyze regime of relative flow rates. So, what do we do now? Well, we punt, and do the worst case analysis which would assume that we get no O2 removal assist from the sweeping action of the bulk CO2 flow. As a result of doing this our residual O2 levels will be less than we calculate, so we will have a built in safety factor.

So, the answer to our first question is: Yes, the bulk CO2 flow probably helps sweep out more O2 than do simple pressurize/vent cycles, but the analysis is too difficult, so we'll just ignore the flow sweep effect, and end up with a pessimistic estimate of our final purged keg O2 levels (i.e. things will actually be better than the calculations show.)

Second question: What's the worst case O2 levels left in a keg purged with the output of an active fermentation?

So, just how do we attack a continuous slow purge flow analytically? Assume a tube runs from the fermenter to the keg liquid post, and an airlock is fitted to the keg gas post. Then every time the airlock bubbles you lose a small volume of the current gas mix (which we are assuming is homogeneous) from the keg and fermenter headspace. Let's call this volume "𝚫V", and the total volume of the fermenter headspace, keg, tube, etc. "V". Furthermore, let's call the current concentration of O2 in V "C". We then have the following:

Total O2 in V before bubble = C * V​

O2 lost to bubble = C * 𝚫V​

Total O2 in V after bubble = C (V - 𝚫V)​

Concentration of O2 in V after bubble = C * (V - 𝚫V) / V​

If C[0] is the concentration of O2 initially, then after "N" bubbles, the current concentration of O2 is:

C = C[0] * ((V - 𝚫V) / V)^N​

For V = 25 L and 𝚫V = 0.0001 L (0.1 mL), (V - 𝚫V) / V = 0.9999960. We're not getting much purging action per bubble; this doesn't look very promising yet.

So, where will we end up at the end of the example fermentation above? Well, we generate 439 L of CO2 from fermentation, and if we divide that into 0.0001 L bubbles, we produce a total of 4,390,000 bubbles. If we plug that into our formula above, and start with 210,000 ppm of O2 in V, then we have:

Final O2 Conc = 210000 ppm * ((25 L - 0.0001 L) / 25 L)^4390000 = 0.005 ppm​

Believe it or not, we reduce the O2 concentration from 21% by volume to 5 parts per billion by volume! :smack: Talk about the power of compounding!

We can only conclude that using the output of a reasonable size fermentation can very effectively purge a keg of O2.

Coming next, the spreadsheet to allow you to do your own calculations.

Brew on

The definitive answer.

 

[RyPA]

People here have posted the math related to the amount of CO2 created in a fermentation and it seems plenty sufficient to purge 2 kegs. I often have 2 kegs(dry hop keg, serving keg) daisy chained to my ferm keg to be purged and it seems to work fine

How do you dry hop in this case? Isn't the intent to have an O2 free sanitized keg? How do you get the hops in?

 

[redrocker652002]

Lots of good reading on this thread and perfect timing as I have been thinking of doing this and ditching my buckets and all the other crud I bought with my starter kit (my brother is getting into it so I might just give it to him with a small delivery fee, LOL). My question is, I have a 5 gallon Torpedo keg and I do 5 gallon batches. Usually what ends up in the fermenter is about 5 gallons, so what, if any, cautions do I have to have when fermenting? I have read some have had some blow off issues, but the kegs will be in a closet that is easily cleaned. If I am going to run a Spunding valve and try to catch the CO2 from the fermentation how would I get the Ferm CO2 from the fermenting keg to the serving keg? This is all very new to me, but seems to be a nice way to ditch a lot of extra equipment and make better beers.

 

[BongoYodeler]

People here have posted the math related to the amount of CO2 created in a fermentation and it seems plenty sufficient to purge 2 kegs. I often have 2 kegs(dry hop keg, serving keg) daisy chained to my ferm keg to be purged and it seems to work fine

This is exactly what I plan to do. Thanks.

 

[BongoYodeler]

How do you dry hop in this case? Isn't the intent to have an O2 free sanitized keg? How do you get the hops in?

Here's my thought. 3 kegs daisy-chained. Keg1 is the fermenter. Keg2 is the dry hop keg. Keg3 is the serving keg, with a blowoff.

Keg2 will have a floating dip tube, and I'll start with no hops in it. Once fermentation really gets going, as evidenced by increased blowoff activity, I'll quickly open the lid of keg2 and dump in the hops, loose. I figure most/all oxygen that enters while the lid is off will rather quickly be pushed out by the continued fermentation. They'll then sit in a CO2 environment until it's time to dry hop.

After fermentation is over I can disconnect the chain and throw keg1 into my keezer to cold crash. After cold crashing for a couple days I can transfer the beer to keg2 at 37° and keep it at that temperature, shaking the keg every few hours to help keep the hops in solution. Or pull the keg from the keezer and transfer to keg2 a bit warmer and not need to shake it.

After a 2-3 day dry hop, transfer to keg3 via floating dip tube hopefully avoiding hop debris. All transfers will be done under pressure, oxygen free.

 

[BongoYodeler]

Lots of good reading on this thread and perfect timing as I have been thinking of doing this and ditching my buckets and all the other crud I bought with my starter kit (my brother is getting into it so I might just give it to him with a small delivery fee, LOL). My question is, I have a 5 gallon Torpedo keg and I do 5 gallon batches. Usually what ends up in the fermenter is about 5 gallons, so what, if any, cautions do I have to have when fermenting? I have read some have had some blow off issues, but the kegs will be in a closet that is easily cleaned. If I am going to run a Spunding valve and try to catch the CO2 from the fermentation how would I get the Ferm CO2 from the fermenting keg to the serving keg? This is all very new to me, but seems to be a nice way to ditch a lot of extra equipment and make better beers.

I'm going to shoot for 4.5 gallons into the keg fermenter.

Connect the gas-in port on your fermenting keg to the beer-out port on your serving keg. Connect the gas-in port on your serving keg to either a spunding valve or some tubing going to a jar of water/StarSan.

I bought some Ferm Cap to add to the fermentation keg to help keep the krausen down. But I've never done this before so I'm not sure of the best time to add it. Hopefully someone will chime in.

 

[doug293cz]

Keg2 will have a floating dip tube, and I'll start with no hops in it. Once fermentation really gets going, as evidenced by increased blowoff activity, I'll quickly open the lid of keg2 and dump in the hops, loose. I figure most/all oxygen that enters while the lid is off will rather quickly be pushed out by the continued fermentation. They'll then sit in a CO2 environment until it's time to dry hop.

I would put the hops in the 2nd keg at the very beginning. CO2 production is highest early in the fermentation cycle. If you wait until you have "increased blowoff activity," as much as 1/3 - 1/2 of the CO2 may have been created already. You will then undo a lot of the purge "work" already done by adding significant O2 to the system (by opening one of the lids), and not have sufficient CO2 production after that to adequately finish the purging. It might be OK, or it might not.

Brew on

 

[BongoYodeler]

I would put the hops in the 2nd keg at the very beginning. CO2 production is highest early in the fermentation cycle. If you wait until you have "increased blowoff activity," as much as 1/3 - 1/2 of the CO2 may have been created already. You will then undo a lot of the purge "work" already done by adding significant O2 to the system (by opening one of the lids), and not have sufficient CO2 production after that to adequately finish the purging. It might be OK, or it might not.

Brew on

Thanks Doug, I'll do that. My intent was to limit the hops from sitting in an oxygen-rich environment for as long as possible. Hopefully the few hours it would take for fermentation to kick off won't be too long for them.

Also, I looked at your post, referenced above, on CO2 displacement. I have to admit it made my eyes glaze over But it looks like enough CO2 is created to fill two 5 gallon corny kegs, while (hopefully) displacing all the oxygen.

 

[Adam Zerwick]

Thanks Doug, I'll do that. My intent was to limit the hops from sitting in an oxygen-rich environment for as long as possible. Hopefully the few hours it would take for fermentation to kick off won't be too long for them.

Also, I looked at your post, referenced above, on CO2 displacement. I have to admit it made my eyes glaze over But it looks like enough CO2 is created to fill two 5 gallon corny kegs, while (hopefully) displacing all the oxygen.

I wonder if it would be any better to purge the empty dry hop and serving kegs in parallel instead of serially. My guess is that it would take less fermentation CO2 to purge both kegs when done in parallel but that's just a hunch.

 

[BongoYodeler]

I wonder if it would be any better to purge the empty dry hop and serving kegs in parallel instead of serially. My guess is that it would take less fermentation CO2 to purge both kegs when done in parallel but that's just a hunch.

Well darn it, now something else to consider. This could set me back another three years. LOL!!

 

[RyPA]

Lots of good reading on this thread and perfect timing as I have been thinking of doing this and ditching my buckets and all the other crud I bought with my starter kit (my brother is getting into it so I might just give it to him with a small delivery fee, LOL). My question is, I have a 5 gallon Torpedo keg and I do 5 gallon batches. Usually what ends up in the fermenter is about 5 gallons, so what, if any, cautions do I have to have when fermenting? I have read some have had some blow off issues, but the kegs will be in a closet that is easily cleaned. If I am going to run a Spunding valve and try to catch the CO2 from the fermentation how would I get the Ferm CO2 from the fermenting keg to the serving keg? This is all very new to me, but seems to be a nice way to ditch a lot of extra equipment and make better beers.

I don't think you have any cautions, just use a blow off tube in a pitcher/bowl of sanitizer. I use a 6.5g Torpedo and fill it to probably a little over 6g. There's should be no risk of an exploding keg if that's what you're concerned with, as the force needed to explode a keg would easily clear out a clogged up ball lock fitting that may have crap in it. Once you try it you won't go back.

Here's my thought. 3 kegs daisy-chained. Keg1 is the fermenter. Keg2 is the dry hop keg. Keg3 is the serving keg, with a blowoff.

Keg2 will have a floating dip tube, and I'll start with no hops in it. Once fermentation really gets going, as evidenced by increased blowoff activity, I'll quickly open the lid of keg2 and dump in the hops, loose. I figure most/all oxygen that enters while the lid is off will rather quickly be pushed out by the continued fermentation. They'll then sit in a CO2 environment until it's time to dry hop.

After fermentation is over I can disconnect the chain and throw keg1 into my keezer to cold crash. After cold crashing for a couple days I can transfer the beer to keg2 at 37° and keep it at that temperature, shaking the keg every few hours to help keep the hops in solution. Or pull the keg from the keezer and transfer to keg2 a bit warmer and not need to shake it.

After a 2-3 day dry hop, transfer to keg3 via floating dip tube hopefully avoiding hop debris. All transfers will be done under pressure, oxygen free.

Just my opinion, but all of the work involved with daisy chaining when you have to crack open the keg anyway to dry hop seems to defeat the purpose. I did a few NEIPA's earlier this year using this purging with fermentation gas method and I didn't see a noticeable difference compared to keg fermenting (which also purges out all o2) and then quickly popping the lid to drop hops in then doing 10 or so co2 purges. My NEIPA's taste better than they ever have and look like OJ until they kick.

Here's what I have on tap now

 

[Adam Zerwick]

Well darn it, now something else to consider. This could set me back another three years. LOL!!

Here's my current process for fermentation keg + dry hop keg + serving keg:

1) Ferment as normal with fermentation keg blowing off into bucket of starsan until the headspace in fermentation keg is at target O2 level. I created a spreadsheet to help me calculate the gravity at which this happens... I think the calculator is shared in the other thread. The assumption is that O2 in headspace doesn't get consumed by yeast.

2) Once I reach this target gravity I'll connect ferm. keg to dry hop keg (gas post to gas post). The dry hop keg is filled to the brim with sanitizer and has floating dip tube with filter. The dry hop keg is connected to serving keg (liquid to liquid post).

3) Once all sanitizer is pushed into serving keg I'll disconnect dry hop keg. Then connect ferm. keg to serving keg (gas post to gas post) and have liquid post go into liquid post of a storage keg or a bucket.

4) Once fermentation is complete, soft/cold crash.

5) Gravity closed transfer fermentation keg to dry hop keg. Usually I'll have enough gravity points left after liquid purge to build up pressure in the kegs.

6) Open dry hop keg lid and toss dry hops and some metabisulfite (0.1 g) into beer. Purge a few times. My thinking here is there is minimal headspace since the dry hop keg is full of beer... so any oxygen in there can be purged more efficiently and has less drastic effect than opening up an empty keg to throw dry hops into.

7) Rouse a few times a day for couple of days by rolling the keg around.

8) Cold crash dry hop keg for 1-2 days

9) Transfer to serving keg


I'd really like to avoid opening up the dry hop keg but haven't figured out an elegant way of doing this with my setup and volumes.

 

[BongoYodeler]

Just my opinion, but all of the work involved with daisy chaining when you have to crack open the keg anyway to dry hop seems to defeat the purpose. I did a few NEIPA's earlier this year using this purging with fermentation gas method and I didn't see a noticeable difference compared to keg fermenting (which also purges out all o2) and then quickly popping the lid to drop hops in then doing 10 or so co2 purges. My NEIPA's taste better than they ever have and look like OJ until they kick.

Here's what I have on tap now
View attachment 806854 View attachment 806855

Great looking beers!!

As I said, this is an experiment. Doing this with an APA as proof of concept, with eventual plans of trying it with a neipa. Here's a neipa I brewed a couple years ago..and it turned out quite good. I'm just looking for process improvements and a simpler method.

But as far as "all that work," I just don't see it. The purge lines are all assembled. With MFL QD's, Duotight fittings, and EVABarrier tubing it took all of a minute or two to put them together. I have the extra kegs. Per my normal process they're already cleaned and sitting half filled with StarSan, ready to go. This setup will be much faster and easier than my normal routine of fermenting in my Speidel fermenter, which has its own cold crashing issues, and having to dry hop with magnets. All doable but I'm looking for something with less variables.

 

[redrocker652002]

Just a thought as I am sitting here at work. How would you check gravity during the fermentation to see if it has completed? The reason for doing this is to keep the O2 out, but to check the gravity the only way I can see doing it is opening the lid of the fermenting keg and grab some beer out. I really am thinking of doing this, but wondering about that one issue.

 

[McMullan]

How would you check gravity during the fermentation to see if it has completed?

As it's under pressure, you simply pour a sample. It's usually quite foamy so the sample needs to settle and, ideally, decarbonate. No need to open the lid.

 

[doug293cz]

Just a thought as I am sitting here at work. How would you check gravity during the fermentation to see if it has completed? The reason for doing this is to keep the O2 out, but to check the gravity the only way I can see doing it is opening the lid of the fermenting keg and grab some beer out. I really am thinking of doing this, but wondering about that one issue.

You do have a beer out post on the keg you can use to pull a sample. Or, you can use one of the tilting, in-situ, hydrometers.

Brew on

 

[redrocker652002]

As it's under pressure, you simply pour a sample. It's usually quite foamy so the sample needs to settle and, ideally, decarbonate. No need to open the lid.

But it is a closed transfer setup, or do i have an additional line available with a picnic tap or something? Sorry, I am not understanding how I would just pour a sample

https://www.morebeer.com/products/b...MIuJbvwM3k-wIVwR6tBh0elQwiEAQYAiABEgJrsfD_BwE

 

[redrocker652002]

You do have a beer out post on the keg you can use to pull a sample. Or, you can use one of the tilting, in-situ, hydrometers.

Brew on

So I would need to have another line set up and connect it to the liquid line out? I was thinking that would be how, but wasn't sure.

 

[McMullan]

Yes, connect a picnic tap to the liquid-out post and pour off a sample.

 

[RyPA]

Get a rapt pill