Pressurised fermentation/spunding in a Type A keg

[squirt in the turns]

I've got a 50 L type A keg that I want to use for pressurised fermentation. I plan to get a Micro Matic coupler, and would like to have to modify both the keg and coupler as little as possible. I think the keg should be fine as is, other than grinding off the lug on the spear as described in numerous threads on AHB. I realise that without shortening the spear I'll likely pick up a lot of trub, but I'll filter to solve that issue.

The Micro Matic coupler has a non-return valve (on the gas-in?). This is presumably going to make releasing gas pressure via the coupler impossible. Does anyone know if this is either an optional extra or can be removed or disabled?

Once the wort is in the keg, I'd like to pressurise with pure O2. How would I go about calculating the required pressure to get roughly the right volume of O2 into the wort?

 

[wobbly]

If you haven't already check out these two threads.

http://www.homebrewtalk.com/wiki/index.php/Closed-system_pressurized_fermentation

This one is a long read being some 100+ pages long

http://www.homebrewtalk.com/f13/closed-system-pressurized-fermentation-technique-44344/

Cheers

Wobbly

 

[wobbly]

Once the wort is in the keg, I'd like to pressurise with pure O2. How would I go about calculating the required pressure to get roughly the right volume of O2 into the wort?

At the risk of copping a bagging from the Williamswarn detractors if I understand you correctly why are you going to add CO2 to pressurise the keg?

If you set out to ferment under pressure and set your spudding vale to about 1.5 bar the system(fermenting wort) will build up to that pressure within 24hours and hold it throughout the fermentation period and your finished beer will be naturally carbonated to what ever level you set your spudding valve to. I find most/all my beers nicely carbonated by setting the WW variable pressure relief valve at 1.5 bar(15psi) from the start to the finish of the fermentation

Cheers

Wobbly

 

[dent]

Just be careful using the coupler as part of your spunding relief. I've found a couple times that krausen and hops have gotten stuck in the keg side of the coupler enough so that I couldn't get the pressure out of the keg even with the spunding valve disconnected. This can be dangerous.

I would stick to 40L batches with that setup.

As far as O2 goes, I used to put in about 20psi and shake it up. But since you now have the option of pressure, you can jam 40psi of air in there, and then you can dissolve much more oxygen in the wort with air than you could at atmospheric pressure. So then you no longer need the O2 bottle.

 

[squirt in the turns]

At the risk of copping a bagging from the Williamswarn detractors if I understand you correctly why are you going to add CO2 to pressurise the keg?

If you set out to ferment under pressure and set your spudding vale to about 1.5 bar the system(fermenting wort) will build up to that pressure within 24hours and hold it throughout the fermentation period and your finished beer will be naturally carbonated to what ever level you set your spudding valve to. I find most/all my beers nicely carbonated by setting the WW variable pressure relief valve at 1.5 bar(15psi) from the start to the finish of the fermentation

Cheers

Wobbly

No, no intent to force carb by adding CO2. I think you misread my post - I'm tallking about adding oxygen, hence my question about trying to work out what level of pressure will get the right amount of oxygen into the wort. I would obviously set the spunding valve higher than whatever level I pressurise to with O2, and adjust to lower pressure if required as the O2 is replaced by CO2.

I'd still be aiming for naturally carbonated beer at the end of primary. I'm hoping that transferring to a serving keg via a filter, with a completely closed and pressurised system, will prevent any loss of carbonation as the beer goes through the filter.

 

[squirt in the turns]

Just be careful using the coupler as part of your spunding relief. I've found a couple times that krausen and hops have gotten stuck in the keg side of the coupler enough so that I couldn't get the pressure out of the keg even with the spunding valve disconnected. This can be dangerous.

I would stick to 40L batches with that setup.

As far as O2 goes, I used to put in about 20psi and shake it up. But since you now have the option of pressure, you can jam 40psi of air in there, and then you can dissolve much more oxygen in the wort with air than you could at atmospheric pressure. So then you no longer need the O2 bottle.

Thanks dent. Yeah, don't really want to get coupler or valve assembly full of krausen. Was hoping it'd go ok with 10 L head space as that'll allow me to fill 2 cornies from a single batch.

I have the O2 bottle already but your suggestion of just using air and really cranking up the pressure is interesting. What would you suggest to pump air in? A bicycle pump? I'd guess that a compressor would be a bad idea even with an air filter in line due to oil and other contaminants.

Wobbly, thanks for those links, BTW. I had already read the first one. That 100 page thread is a lot of info to wade through but I'll see what I can get from it.

So, does anyone know what the go is with the non return valve on the coupler? Can it be removed?

 

[dent]

I dunno about the micromaster coupler, but in the cheapo ones I have there is a little silicon check valve inside the gas end which is easily removable.

I don't think there is anything wrong with compressor air - between the water / oil separator in the regulator, and the sanitary filter, I don't think anything nasty is getting through.

 

[squirt in the turns]

Cheers dent. I might just go for the cheap chrome plated version for the time being, especially if there's any chance I'll have to do something severe to it to get the NRV out.

How did you arrive at that figure of 40 PSI? Is it possible, within reason, to get too much air dissolved in the wort? Also, if that were 40 PSI of CO2, I believe it'd be well above the level that causes yeast stress. Maybe 40 PSI of air wouldn't have the same effect, and that the gas would be quite rapidly absorbed by the wort and the pressure would drop reasonably quickly anyway.

 

[dent]

Yeah the constituents of air (including the O2 you want) aren't particularly soluble in the wort, so pressure is good, and I don't believe it is harmful to the yeast - same how if you're scuba diving you don't get crushed by the water pressure. My yeast have been happy enough anyhow.

As to the figure - well, they say 8ppm is the max with air, but that is with a stone for extended time etc. Since we are just shaking the keg for a bit, I figure it needs all the help it can get for the 12ppm or so we want. I was going to test it but the DO meter I borrowed was dead

 

[squirt in the turns]

Ok, I'm dragging this topic up again as I'm nearly ready to try this. I'm planning a 40 L batch of pilsener. I normally only do 20 L batches of lager and I only have one 5L Erlenmeyer flask. However, as the keg is 50 L, I'll do the whole 40 L in one go. I'll be no chilling, reserving wort on brewday for use as a starter, so will be happy to pitch the entire starter volume rather than decant the "spent" wort.

How's this schedule sound:
step 1 - pitch a pack of WY2001 (Urquell Lager) into 5L (reserved from brewday) on a stir plate, at normal lager fermentation temperature (~9 degrees)
step 2 - at high krausen (or later?), pitch that 5L plus another 10L (also reserved from brewday) into primary (the keg), allow to go until nearly fermented out, with no agitation
step 3 - pitch 28L at 9 degrees to make up a total volume of 43L, allowing 3 or 4 L loss to trub, to make enough to fill 2 cornies. Oxygenate with pure O2 under pressure, ferment under pressure, allowing temp to rise to maybe 16 or so as per accepted techniques for fermenting under pressure.

Would there be any benefit to fermenting step 2 under pressure, and/or oxygenating the starter wort under pressure?

Alternatively to the above, would it work if I just made a 5L starter, pitched that into primary with one 18L cube of wort, then pitch the remaining 20L cube 24 or 48 hours later with additional oxygen?

I appreciate Dent's comments above about not needing oxygen, but I've already got the O2 kit so feel I might as well try oxygenating under pressure. Also the only compressor I have is a dirty tyre-inflator one from Super Cheap that I wouldn't trust anywhere near my wort. My concern is that in a sealed environment it's probably possible to dissolve toxic levels of O2 in the wort. Does anyone have any advice to offer on techniques or maximum pressures to prevent this?

 

[dent]

Yeah I used to charge up the vessel with pure O2 (to 20psi once, shake it up, that's it) while I still had the cylinder, might as well use up the gas while it's there. Worked great.

Theoretically every time you expect yeast to multiply adding more O2 is good.

I like your ferment schedule, only thing I'd change is on step 3 to chill both your wort and small-ferment to 6 degrees or so before pitching, then wait for activity before cranking the temp to your normal lager temps.

If it was me I'd be too lazy and skip step 2 altogether, but if you can be bothered it looks like a great way to get a buttload of yeast cranking.

 

[///]

most NRV in couplers are plastic inserts easily removed. For a standard 4.5-5% beer, capping off with 2-3 points plato will give you 1.5 bar at the end.

High levels of CO2 can cause yeast issues thru the primary ferment, i would leave till the end to recover so there is not ester issues and the like.

Scotty

 

[rehabs_for_quitters]

Looking at doing this myself but all the reading I have been doing some places start off using a blow off tube then after the growth phase of the yeast is done they use a PRV, which is apparently better for yeast growth and less chance of off flavours, others say do the whole thing under pressure but don't exceed 15 psi?

Who is one to believe has anyone done a side by side of these approaches, I am looking at using a blow off for 24 hours then attach a PRV would this be alright?

 

[///]

See what this fella says, knows his stuff ...

https://books.google.com.au/books?id=QpDVsu-vaBcC&pg=PT438&lpg=PT438&dq=oxygen+pressure+wort&source=bl&ots=_Kk_K36BTJ&sig=av-LQ4njm4RiR25wvOkFJXmEn1o&hl=en&sa=X&ei=3texVNiLEIHQmwW12ICYDg&ved=0CEcQ6AEwBg#v=onepage&q=oxygen%20pressure%20wort&f=false

 

[droid]

my head hurts

 

[dent]

others say do the whole thing under pressure but don't exceed 15 psi?

I never have CO2 pressure on at the yeast growth phase. I don't see the benefit of CO2 pressure at that point, and the yeast aren't going to enjoy it. There isn't any CO2 at that point anyhow unless you're adding it in yourself.

Basically I just close it up and after the yeast are finished the growth phase, that is when they start generating enough CO2 to bring the pressure up, so it all sorts itself out.

 

[rehabs_for_quitters]

Dent, so you just set your PRV and let it go, that's good to know and nice and easy, I am looking at going for around 12 to 15PSI what pressure are you using, and at that level how well carbonated is the beer after primary?

 

[dent]

I don't think it matters a lot, I've run it at various pressures and I haven't seen a lot of difference either way. 12 to 15 is good - at that pressure once the ferment is done the beer is mostly / half carbed depending on your final temperature.

 

[rehabs_for_quitters]

Excellent info thanks, going to be setting the controller at 16 deg and 15 PSI on the PRV and let it do its thing looking forward to giving it a go

 

[booargy]

I set the PRV to carbonation pressure at the highest temp