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Old 10-11-2011, 10:08 PM   #1
dekesdad
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Default Buy or Build: 3.5 -4 gallon pressurized conical fermenter

I've lurked here forever, it seems like. OK, more like 3 or 4 years.

I want a pressurize-able 'unitank' conical fermenter for my project to experiment with single step fermenting & carbonating. BUT, I want to do 2.5gallon half batches.

I figure (that means I'm completely guessing) I'll need a half gallon to 1.5 gallons of headspace for this since it'll be closed and pressurized. Sound about right?

It doesn't look like anyone makes a conical fermenter smaller than 6.5 gallon..Not that I found anyway. Before I go drop $$ on welder and spend some time frigging with it to weld this up myself: anyone seen smaller pressurized conical fermenters?

Here's another question: if it don't need to be pretty, what would prevent me from brazing it up instead of welding it if I end up DIY to get it built?

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Old 10-11-2011, 10:46 PM   #2
DrJerryrigger
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I haven't seen any small ones for sale either. It seems like there must be something available premade that could be a good start for a welding project, like a big SS funnel welded half of a SS tank, maybe a little keg....

How much pressure do you want this to hold up to? Brazing would likely do the trick, but will never be as strong as a good weld.

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Old 10-12-2011, 01:28 AM   #3
dekesdad
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Quote:
Originally Posted by DrJerryrigger View Post
I haven't seen any small ones for sale either. It seems like there must be something available premade that could be a good start for a welding project, like a big SS funnel welded half of a SS tank, maybe a little keg....

How much pressure do you want this to hold up to? Brazing would likely do the trick, but will never be as strong as a good weld.
Thanks for the reply on this one - barring finding anything already available I was thinking the same thing: using a SS funnel welded to a small SS pot.

To answer your question, I was thinking about 15 PSI might work. I could braze or weld the relief valve of any off-the-shelf pressure cooker right on there since most of those are preset at 15PSI blowoff..

I found a 8 qt SS stockpot in Walmart tonight for under $7. I wandered around in the store with it for a bit and discovered that it marries up pretty nice to the SS 4.5 quart mixing bowl on a Hobart kitchen mixer. The two together is 3.5 gallons right there. So, I'm going shopping around the net tonight for price on replacement Hobart mixing bowl and thinking about that combination for a bit.

Welding of course would be desireable, but to be as shoestring about it as possible, it would be obviously cheaper to go buy a torch at Home Depot and silver braze and then finish grind it than to go buy a welding setup..If it would hold up to being watertight and staying watertight under pressure my wallet would rather braze than weld I'm really interested in thoughts on this one.
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Old 10-12-2011, 03:39 AM   #4
jerdes
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If you are planning to do pressure fermenting you want something with more structural integrity than a cheap pot soldered to a mixing bowl. At minimum this seam should be welded and I still would hesitate to put anything over a few psi in it. Even at that, you risk creating a bomb if your pressure relief fails. Why not just use a corny? Yeast collection is more difficult but they are designed to hold 130 psi I believe, way more pressure than the yeast can create before dying off. a corny would be cheaper, easier and its a tried and true pressure fermenting vessel.

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Old 10-12-2011, 03:47 AM   #5
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I think you could be alright with brazing for 15psi. But be perpared for it to start spraying beer from a pin hole in it some where. If not exploding.

I don't know about the pressure cooker blow off. There are some that may work, but not the ones I've used. Often the pressure in regulated by a weight on an orifice. This only works when there is a strong pressure build up. It does not hold existing pressure in all that well. It would work during fast fermentation, but the pressure would leak out when things slow down.
The safty values on pressure cookers are often a bit for rubber which will just blow out, the purpous being; it will blow out before the pot blows up. Not an exact pressure, just an intended weakest spot.

There are better pressure regulators available. Ones on Cornie kegs work I've heard, and I'm sure you can get them online for a reasonable price.

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Old 10-12-2011, 05:11 PM   #6
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im sure you could experiment with some different (lighter) springs on a corney keg pressure relief valve. they come apart and you can swap the springs out fairly easily. the stock ones release pressure somewhere above 100 psi. although the above is true; if the spring opens all the way at, say 20psi, its going to partially creep open when it nears that pressure. meaning a slow buildup of gas might be vented completely at only half that (meaning it would only hold maybe 10psi of a slow trickle of gas).

i would think that the cheapest thing for you to experiment with, would be to get a corney keg and cut a section off the bottom, and just weld/braze on a S.S. funnel. it will certainly take some skill (or atleast luck) to get it airtight, but a good braze should be able to hold 15psi like that.

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