How To Make A 15 Gallon Fermenter

first i started with getting the keg top cut out. since i had an 8" flange, i had the hole in the keg cut appropriately. i then had the flange welded on to the keg top. (I'm neither a cutter nor a welder so i had to out source these procedures)

what we're looking for here is a smooth, sanitary weld.

i cut the lexan circle to fit the top of the flange lip. the lid was then drilled, and tapped to fit my compression fillings.

the gasket material i fashioned from a piece of latex tubing. i rolled the tubing back on itself, and snapped it over the other end.

we're almost there!

place the gasket on the flange

place the lexan lid on the gasket

apply your clamps

finished keg

during fermentation one of the ports will be capped off while the other will be the blow off tube. when primary fermentation is complete all you need to do is insert a tube into the portal, pressurize the keg through the other portal with co3, and extract the yeast from the bottom of the keg. now you're ready for secondary clarification.
after clarification is complete you pressurize4 the keg using similar technique as above and push the beer into kegs for carbonation.
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many thanks to TC, SWL, and Brewgeek for their help. without them i'd still just have an idea.

Well that's a one off design.
Cool.
Where did you get the 8" flange?


What boil kettle are you using for 15 gallon batches?

8" flange was a freebie from a member of our brew club who does polimars and high end chemicals.

i'm using a 20 gallon boil kettle to do 15 gallon batches on this:



we also have a club 50 gallon kettle and fermenter



we'll be using this one to do our 55 gallon bourbon barrel brew this fall that will condition in cold storage until next fall

I'm assuming all the work putting the flange on was to acheive more headspace right? I was going to make a lexan cover and put it directly down on the top of the keg, but that would limit me to 12 gallons or less.

that would absolutely work bobby - in fact that was my original idea - but then i happened upon the flange - and i thought - BAM ! more head space - more beer YEAH!

Brewhead, can you tell me how that lexan was cut? I actually need to cut a circle out of some 1/4" lexan myself, and was really wondering how to go about it without getting a nasty lop-sided mess.

Thanks in advance!

BTW the fermenter looks great!

i cut the lexan with a craftsman scroll saw and smoothed it all out with the belt sander. the thinner the blade the better the cut will go. it will take you prob 15 minutes or so of cutting if you are patient. push it and you'll be breaking blades

I hate to rain on anyone's parade or efforts, but I don't think the Lexan is going to stand up to much pressure before it breaks or cracks.

An 8 inch hole has an area of 8^2*pi/4 = 50 in^2. Applying 3 psi to the vessel will result in a 150 pound force to the lexan. I guess it depends on the thickness of the lexan.

Otherwise it looks great.

Lexan is a trade name for polycarbonate (i.e. bulletproof glass). I'm sure it can handle the 2 PSI or so to do force transfers. The math says that would put a total of 100 pounds on the entire disc. The design could really be improved by going up to 1/2" lexan or even plain acrylic or by using more clamps (or a metal ring to spread the load). Check out freckleface.com for cheap small quantities of plastic sheet.

actually, the easiest way to improve the design is to put a bar across the upper face of the lexan to prevent it from bulging out. Maybe a hub with 4, 6 or 8 spokes and then clamp the spokes down sandwiching the lexan between the hub and the flange.

From the pic, that Lexan looks pretty thick to me - I thought it was 1/2". I think it would be fine as is. The only place I could see a problem is cracking around the two holes.

I would not bee worried about lexan failing in this situation. I took a Nalgene bottle (made of lexan and put it under water to fill it (no air space) and put the cap on. I put it in the freezer expecting to see the side of the bottle blown out instead it pushed the cap apart and pushed ice about an 1.5" out the top. The cap is mad from polypropylene rather than lexan. I would guess that whatever is holding the lexan to the keg or the metal lip would fail first. I would not be worried about it failing with 50 lbs on it. Plus if it begins to deform the seal will be compromised and then the pressure will release till the lexan returns to its original shape.

and thats my 2¢

I think it's possible to split the Lexan under pressure, but only time will tell. The more likely result is that you'll crack it with repeated clamping pressure.

The welds look a little sketchy from the outside, but the inside appears nice and clean.

I like the overall idea! Good luck with it!

Ethanol CH3CH2OH said:

I would not bee worried about lexan failing in this situation. I took a Nalgene bottle (made of lexan and put it under water to fill it (no air space) and put the cap on. I put it in the freezer expecting to see the side of the bottle blown out instead it pushed the cap apart and pushed ice about an 1.5" out the top. The cap is mad from polypropylene rather than lexan. I would guess that whatever is holding the lexan to the keg or the metal lip would fail first. I would not be worried about it failing with 50 lbs on it. Plus if it begins to deform the seal will be compromised and then the pressure will release till the lexan returns to its original shape.

and thats my 2¢

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Bottles are small diameter. Bottles don't have large flat surfaces, do they ? Everything is convex.

Actually now that I look at it, it does look like 1/2". Really the only thing I see as a weakness is only holding it down at 4 points. That setup would actually hold a vaccuum really well being supported all the way around the flange (but that's not the situation here obviously). While I wouldn't suggest using this as a serving vessel at 20 psi, I have no doubt the 2-5 psi for liquid transfer will be fine. I've built SCUBA camera housings with 1/2" acrylic and they hold up down at 100 feet. Of course, my disc is only 4" in diameter so it's not a perfect comparison.

have you done a liquid transfer??? how did it go???
JJ

brewman ! said:

Bottles are small diameter. Bottles don't have large flat surfaces, do they ? Everything is convex.

Click to expand...

The flat bottom did bulge out approximately 3/8"-1/2" from its original position, but it returned to its original shape with no leaks or cracks, but I am sure it would fatigue and fail with repeated stress. I ran across a data sheet on Lexan.
http://www.envplastics.com/ftpgetfile.php?id=13
sheer strength at yield is 6000 psi over an area of 50 sq. in. gives 120 lbs of pressue.
ultimate strength is 10000 psi over 50 sq. in. gives 200 lbs of pressure.

brewman ! said:

I hate to rain on anyone's parade or efforts, but I don't think the Lexan is going to stand up to much pressure before it breaks or cracks.

An 8 inch hole has an area of 8^2*pi/4 = 50 in^2. Applying 3 psi to the vessel will result in a 150 pound force to the lexan. I guess it depends on the thickness of the lexan.

Otherwise it looks great.

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i'll take that under advisement - though with one initial batch run through it and one on the way tomorrow - i'll have to say i've not had any psi problems.

the lid to the plastic bucket that most of us started with is way more flimsy

guys - it has a blow off tube just like any fermenter. there is virtually no psi build up. yes it is a 1/2" thick piece of lexan. if i build up enough psi to break it - we're in trouble. if the lexan bulges - then we've got problems. but so far - works like a charm.

have you done a liquid transfer??? how did it go???

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yes. the liquid xfer into the out post on the corny worked like a charm. the yeast extraction was not spot on as i would have wanted tho i did get a lot of it out. there was a thin layer on the bottom even with the diptube all the way down and curved to the inside of the keg. no worries tho - the thin layer was not enough to cause me worry and the beer is aging as we speak. all i did was raise the dip tube up a bit and mark it for referance...and transfer under co2 pressure.

i think you guys have missed the mark with the psi build up. with a blow off tube there is virtually none as it is released through the blow off much like a class carboy.

this makes two of these fermenters in our club and one has been used extensivly...without failure.

brewhead, that is awesome! Now you've got my the DIY-er inside of me thinking.....

go for it man - i am really pleased with mine.

The welds look a little sketchy from the outside, but the inside appears nice and clean

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in defence of the weld, the man who welded it for me is a master welder, and a microbrewer who handles not only his own brews but contract brews for many companies such as orange blossom and Charleston brewery.

the flange set right over much of the star pattern on the keg and much filling was needed...all the time making sure we were doing a sanitary weld. not easy.the inside was ground and welded then ground and polished. there are no nooks and crannies inside - where it counts.

Anybody know where to source a flange like this? I would love to have at least one big fermenter for my bigger brews instead of splitting up to multiple carboys.

Brewhead-Any chance the friend of yours can point us in the right direction for sourcing these flanges?

I've got a peice of lexan (mines only 1/4" thick) and a seal I'm plannning on putting directly over the cut out top of a Sanke. I'm having trouble finding the parts/thread sizes that will match up to the posts on my cornies. I see them in your pics, but could you give specifics regarding thread size etc.

I don't think those are corny posts you see in the picture. They look more like compression fittings with NPT threads either tapped into the hole in the lexan or held with a backing lock nut.

I realize a gas-side corny post would be ideal there but I don't know of anyone that sells any kind of fitting with that kind of thread on it.

Bobby_M said:

I don't think those are corny posts you see in the picture. They look more like compression fittings with NPT threads either tapped into the hole in the lexan or held with a backing lock nut.

I realize a gas-side corny post would be ideal there but I don't know of anyone that sells any kind of fitting with that kind of thread on it.

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I think you're right. Looking at the pic showing it in use, it's not what I was thinking about with a ball lock type of connection. I had taken the post from my corny to Home Depot to try and match up the threads so I could just screw it down on the lid and attach my existing CO2 line to it, but I couldn't find anything that had the same thread pattern (like you said).

dont they make bullet proof glass out of lexan composit