Making a unitank

[Nommag]

Hello all,

My brother in law is a welder working for an engineering company that makes, repairs and installs various kinds of tanks (and things) including large Unitanks. As someone who wants a pressure fermenter but doesn't really want to pay for one, I requested he build me a 50litre Unitank in exchange for beer. He said he would try find time for it at some point (hopefully soon) but had some questions about specifications and required functionality. Has anyone built a unitank or done specifications to have one made. I've never even used a pressure fermenter so any help would be appreciated.

Information on DIY homebrew unitanks is impossible to find!

 

[SanPancho]

60 degree cone. 20-30% headspace for your desired batch size. Probably gonna need 3ml steel if you want 1 bar/15psi rating. Then just spec out the ports you want. For his sake id say get a 4 or 6” tc ferrule to use as your lid. Alot easier for him than making one himself. Aa for the steel 316 is great, 304 will do fine.

also- plan out whether you want feet that will take casters or not.

 

[Nommag]

It sounds like you have built one of these before, do you have any photos of your build (if possible)?

 

[SanPancho]

nope, i cant weld stainless, dont have a garage or workspace. just that i've spec'd and ordered multiple tanks from china direct from manufacturer. we have 2bar rated tanks, they required 4mil steel, so im assuming 3mil was fine for the 1 bar tanks. if you only need them to hold a few psi for doing transfers then you could even do 2mil.

i dont have any easily accessible at the moment, but you can probably google "conical fermenter drawing" or something like that and get a bunch of drawings and plans for big tanks. since the 60 degree cone defines the ratio between cone and body you can pretty easily just scale them up and down to get approximate dimensions for your build. if you cant find something decent you can pm me and i'll try and dig up our spec sheets. but i gotta imagine there's tons online.

 

[Nommag]

Thanks for your help - The search for conical drawings turns up a bit more that is helpful. I was using the 'unitank' term just because a lot of the DIY fermenters arn't intended for pressure brewing. But 'unitank' is a bad search term it turns out.

 

[SanPancho]

But 'unitank' is a bad search term it turns out.

YESSSS. its annoying as hell how folks have just started using the term willy nilly. as i was always told, unitank means it can ferment as well as brite/carb. meaning that it should be a pressure vessel, at least 1 bar, if not 2 or even 3.

i actually had a guy from a pretty large local brewery offer some "unitanks" for sale, only to find out that they didnt hold any pressure at all. they were basically open top fermenters. WTF.

anyways, that's my rant. good luck on the build.

 

[SanPancho]

also- dont be afraid to use ebay and aliexpress for fittings like tc clamps, ferrules, butterfly valves, elbows, tees, etc. takes a little while to arrive but saves you quite a bit of coin.

 

[Nommag]

I'm never afraid to use Aliexpress (except for the fact all of my stuff is stuck at the airport in China due to New Zealand having closed their borders to everyone).

Some of those big expensive stainless conical fermenters that dont hold pressure annoy me the most. But your rant is spot on, Unitank literally describes its use in the name.

 

[apache_brew]

I'm mustering up my own plan for something similar right now. My plan is modify a 1/2 bbl keg by welding on 60 degree cone with 2" drain, and add (4) 1.5" ferrules for racking,sampling,oxygenating/carbonating, and temp probe. The top of the keg will have a 6" tri clamp for access and incorporated 2" ferrule for dry hopping, ball lock disconnects for blowoff/pressurizing. I'm planning on using it in a regulated freezer, but you could always add an internal coil and run glycol instead.

I ordered all the parts from eBay and Aliexpress. Some raw materials like sheet and tube will be sourced through local suppliers.

That being said, I like spending time drawing things like this up, I have a TIG welder and shop tools to build it myself, and I want two of them (cheap). Look really hard at the Spike CF15 unitank. Its a great value and I'm sure won't disappoint.

 

[Nommag]

also- dont be afraid to use ebay and aliexpress for fittings like tc clamps, ferrules, butterfly valves, elbows, tees, etc. takes a little while to arrive but saves you quite a bit of coin.

Good morning, so the unitank is almost done and ready to get some fittings. Do you have any AliExpress links to good fittings you have personally used (I'm thinking pressure relief valves, gauges etc).

 

[apache_brew]

Damn, nice fabwork right there. Post more pictures of the progress. At this time I would source parts shipped domestically via various ebay sellers or better yet LHBS's. International shipping seems like a crap shoot these days.

 

[Nommag]

Damn, nice fabwork right there. Post more pictures of the progress. At this time I would source parts shipped domestically via various ebay sellers or better yet LHBS's. International shipping seems like a crap shoot these days.

Maybe if lived in the States that would be reasonable. Unitank components are uncommon here and are 3-5 times if not more expensive than places like AliExpress. I would prefer local if I could but at that point it would be easier and not much more expensive to just buy the ss brewtech unitank.

 

[SanPancho]

Not for aliexpress. seems like most of my buys there are for homebrew type stuff. but have bought a bunch off of ebay. no particular vendors stand out in my mind. didnt do bulk orders, just a few pieces here, a few pieces there, etc. etc.

for the most part it seems like its just a decision on 304 or 316 stainless. most pricing (at least on ebay) seems pretty competitive. personally i go with 304. you gotta really abuse this stuff to have to worry about needing 316 in my opinion.

looks like its gonna be a nice tank.

 

[Nommag]

So the tank is mostly done, just needs a blow off cane made. I'm looking at AliExpress for pressure relief valves and the cheapest are these adjustible kind with what appears to be a hand crank. I don't get why they are cheaper than the ones that are set to a fixed pressure or even how to use them. Any advice on that would be great.

 

[SanPancho]

nice looking tank! ****, i'd have your man weld me one if it wasnt across the damn ocean.

not sure which prv you're referring to but from what you're describing it sounds like a standard prv. they all essentially have a spring that has a set tension on it, and its equals 15psi or 10 or 20 or whatever. so in reality you can just set it to whatever pressure you want it at and leave it there.

setting it initially is a bit of a pain, as you would want to wait at least a few hours if not even a day between the time you set it and when you check it to see what level of pressure you're at. but in reality, its a safety device, so as long as it releases at 5 or 10 or whatever you're good. once you've got it set, you;re done.

now- the million dollar question is what sort of pressure rating you're gonna give this tank, i.e. how high you wanna set that prv.

 

[Nommag]

Thanks for your awesome responses - ill keep the pictures coming.

So i've been looking at aliexpress and these are the two different options (the first is fixed at 2bar, the second adjusts between 0.5 and 5 bar)



Basically I just want to know which one to get. I would presume I just turn the hand crank on the adjustable one and tighten it to increase/decrease the pressure it lets off.

I did pass on the recommendation of 3mm thick steel. However, what I got is mostly 2mm with some 1mm. My brother in law is certain that that is more than enough to hold up to 3bar. He can pressure test it at work when it is done to determine. That is why the 2bar relief valve seems like a good option.

 

[apache_brew]

I'd go for an adjustable type and couple it with a pressure gauge on the tank. That way you could use it as a spunding valve too. You could always incorporate ball lock fittings too and couple npt fittings off a single ball lock connector to minimize tri clamp tank ferrule space. They sell the weld in ball lock post threads on Aliexpress too.

 

[Nommag]

It's a shame the adjustible ones don't have an indication on them of what pressure they release on to take the guess work out of it.

 

[Qhrumphf]

A PRV is *not* a spunding valve and should *never* be used as such. It is a *safety device* and should not be tampered with. It should be set at the rated pressure of your tank, preferably two of em in case one fails. If you want a spunding valve as well, add that in addition and keep it below the rated pressure of the tank.

 

[apache_brew]

I'd rather trust a decent pressure gauge anyways, no guess work. And I'm sure your brother in law knows better, but please pressure test the tank hydro-statically full of water.

 

[Qhrumphf]

As for testing PRVs, hook em straight up to a CO2 supply, regulator set below their pop point, and adjust up slowly until they blow.

 

[apache_brew]

A PRV is *not* a spunding valve and should *never* be used as such. It is a *safety device* and should not be tampered with. It should be set at the rated pressure of your tank, preferably two of em in case one fails. If you want a spunding valve as well, add that in addition and keep it below the rated pressure of the tank.

Agreed. I didn't catch on that the discussion was revolved around PRVs as safety devices. Another reason to have dedicated pressure gauges in the tank in order to visually monitor the pressure at all times.

 

[day_trippr]

This is so cool. Please be sure to take a bunch of detail shots when it's all done and done and post them here

Cheers!

 

[SanPancho]

Thanks for your awesome responses - ill keep the pictures coming.

So i've been looking at aliexpress and these are the two different options (the first is fixed at 2bar, the second adjusts between 0.5 and 5 bar)

View attachment 680540View attachment 680541

Basically I just want to know which one to get. I would presume I just turn the hand crank on the adjustable one and tighten it to increase/decrease the pressure it lets off.

I did pass on the recommendation of 3mm thick steel. However, what I got is mostly 2mm with some 1mm. My brother in law is certain that that is more than enough to hold up to 3bar. He can pressure test it at work when it is done to determine. That is why the 2bar relief valve seems like a good option.

so what i'd say is that you should definitely let your BIL pressure test that sucker, assuming this is something the shop does often and car perform safely. should it ever fail, even at 1 bar, you're looking at flying shrapnel and bad consequences if you are anywhere near it.

as noted above, prv is a safety device. that's why i'm saying it should be a set it and forget it situation on an adjustable type.

if you want to use high pressures for natural carb, then it depends on what sort of testing you get back. if BIL gets it up to 3 bar, then you wanna use 2 bar prv. that's very very common- "rated at 2 bar, tested at 3 bar" that's about as high as beer fermenters need to go. 2bar will carb a beer at room temp. if he stops at 2 bar, use a 1 bar prv.

so lets say BIL does get it to 3 bar, you could use the 2bar unit as your safety, and the adjustable unit as your spunding device.

 

[Nommag]

so what i'd say is that you should definitely let your BIL pressure test that sucker, assuming this is something the shop does often and car perform safely. should it ever fail, even at 1 bar, you're looking at flying shrapnel and bad consequences if you are anywhere near it.

as noted above, prv is a safety device. that's why i'm saying it should be a set it and forget it situation on an adjustable type.

if you want to use high pressures for natural carb, then it depends on what sort of testing you get back. if BIL gets it up to 3 bar, then you wanna use 2 bar prv. that's very very common- "rated at 2 bar, tested at 3 bar" that's about as high as beer fermenters need to go. 2bar will carb a beer at room temp. if he stops at 2 bar, use a 1 bar prv.

so lets say BIL does get it to 3 bar, you could use the 2bar unit as your safety, and the adjustable unit as your spunding device.

My BIL thinks it could hold 9bar no worries, still going to get it checked though. He said the way its shaped helps with the load. Thing is an absolute beast, compared to corney kegs.

 

[Qhrumphf]

Functionally 2 bar will do all you need. As long as it's pressure tested above 2 bar you'll be fine. Most commerical vessels are only tested/rated +1 bar (though many commercial brite tanks are +2 bar)

 

[Nommag]

Its very difficult building your own unitank and figuring out its use - especially considering im at the point in brewing where im considering buying a robobrew so i can go all grain.

Also its a shame ss brewtech dont ship internationally, they have all the parts I need and are cheap compared to the same parts here.

 

[ethan44]

Man this is awesome. I'm in NZ too and really disappointed about the lack of pressure fermenter options we have here. Sadly the SS Brewtech Chronicals are not rated for pressure. Can't get Spike here either as their options look decent. No other good stainless options really. Wishing I knew how to weld right about now...

 

[Vale71]

Thanks for your awesome responses - ill keep the pictures coming.

So i've been looking at aliexpress and these are the two different options (the first is fixed at 2bar, the second adjusts between 0.5 and 5 bar)

View attachment 680540View attachment 680541

Basically I just want to know which one to get. I would presume I just turn the hand crank on the adjustable one and tighten it to increase/decrease the pressure it lets off.

I did pass on the recommendation of 3mm thick steel. However, what I got is mostly 2mm with some 1mm. My brother in law is certain that that is more than enough to hold up to 3bar. He can pressure test it at work when it is done to determine. That is why the 2bar relief valve seems like a good option.

You'll need a non-adjustable valve set to whatever you decide your tank's pressure limit is that must be attached and fully operational at all times. Then if you want to do spunding/pressure fermentations you'll need a good adjustable spunding valve such as this:

https://www.aliexpress.com/item/328...earchweb0_0,searchweb201602_,searchweb201603_
It's basically the same one that SS Brewtech sells, I've no idea if it will be cheaper for you source it directly from China. In all honesty, I dont' have the slightest idea how much a Kiw... a New Zealand Dollar might be worth at the moment...

 

[Nommag]

Man this is awesome. I'm in NZ too and really disappointed about the lack of pressure fermenter options we have here. Sadly the SS Brewtech Chronicals are not rated for pressure. Can't get Spike here either as their options look decent. No other good stainless options really. Wishing I knew how to weld right about now...

The spike stuff would be sweet for US prices - A couple of friends here who brew wanted their own unitanks, but if I was paying market value for time, it would work out cheaper just to buy a brewtech unitank. I'm only getting it for free because my BIL wanted to make one for fun and he tried my blackrock draught I made (he only drinks waikato #Hamilton) and liked it so wants me to make him some more.

You'll need a non-adjustable valve set to whatever you decide your tank's pressure limit is that must be attached and fully operational at all times. Then if you want to do spunding/pressure fermentations you'll need a good adjustable spunding valve such as this:

https://www.aliexpress.com/item/328...earchweb0_0,searchweb201602_,searchweb201603_
It's basically the same one that SS Brewtech sells, I've no idea if it will be cheaper for you source it directly from China. In all honesty, I dont' have the slightest idea how much a Kiw... a New Zealand Dollar might be worth at the moment...

Thanks, ill get a fixed one. The SS brewtech spunding valve is $170 local ($102.50usd) so that's actually not terrible. The pressure relief valve local is a $130nzd ($78.50usd) That is well over priced

 

[ethan44]

The spike stuff would be sweet for US prices - A couple of friends here who brew wanted their own unitanks, but if I was paying market value for time, it would work out cheaper just to buy a brewtech unitank. I'm only getting it for free because my BIL wanted to make one for fun and he tried my blackrock draught I made (he only drinks waikato #Hamilton) and liked it so wants me to make him some more.

Yeah I've been researching it a little bit and can see that the cost of a quality stainless steel welder's time is quite high. My workmate and I are (teachers in Christchurch) are always thinking about different career paths and that would be an awesome one for NZ. Considering that SS Brewtech 26L unitank is $1545, I don't think I'll be getting one (let alone 2) any time soon.

 

[Nommag]

Yeah I've been researching it a little bit and can see that the cost of a quality stainless steel welder's time is quite high. My workmate and I are (teachers in Christchurch) are always thinking about different career paths and that would be an awesome one for NZ. Considering that SS Brewtech 26L unitank is $1545, I don't think I'll be getting one (let alone 2) any time soon.

I mean the $1550 isn't even that bad when you consider time to make, materials, shipping to nz, all the accessories (which as I've found out are hugely expensive) and then on top of that pressure certification. You literally can't make them cheaper if you have to pay for time (it's taken 20 hours to get this far) and even just being able to weld isn't enough. My BIL is trained specifically to weld these sorts of things. I've really hit the jackpot, he is even considering building a copy of one of those like 30k brewtech minibreweries because he can. Sky's the limit.

 

[Nommag]

Just an update, the unitank has been sitting around in my brewing room for a few weeks now since my BIL lost interest in it. I was advised that it still needs an acid wash and he can build a blow off cane. The interest in it is gone for him though and he didn't want it at his house anymore but will finish it when I get the parts to start using it. It fits perfectly into my fermentation fridge which is great. But I'm very confused still at what parts I need to buy and if it will even work. I have ordered a bunch of cheap stuff off Ali like gaskets, tri clamp covers and a couple of tri clover barbed 10mm hose tails. But who really knows if they will fit probably since I only just measured it up today. I thought before I payed around $100nzd to buy the PRV and Pressure gauge i'd check what I have in front of me is practical and functional. The whole setup was free so its hard to be fussy at what I have, but i'd like to get some use out of it if I can.

The below image is the top, there are 2 small tri clover openings that are 50mm OD and 35mm ID. The middle opening is 167mm OD and 146 ID


The midrift has three tri clover openings that are 50mm OD and 35mm ID and the upper ball lock valve is also 50mm OD and 35mm ID. The large ball lock valve opening at the very bottom is 64mm OD and 48mm ID.



The bottom has a weird shape because my BIL wanted it to meet the fridge measurements, who knows how the shape will affect the draining of yeast and trub out of the bottom.

 

[SanPancho]

top needs a blow off port which can be a hose barb You’ll want co2 port which can either be the second small tc port or you can buy a cap for the big port that also includes a small tc port in it. The PRV is usually better off at highest point to prevent fouling but as long as you don’t fill tank too full it can go on smaller side tc port. You got options. You’ll want to be able to blow in co2 while adding dry hops so maybe side small port for co2 and prv in the cap of the big port. Shouldn’t be hard to find a cap with a port in it. Pretty common.

at the bottom of the cylinder you’ll want One port for your thermometer / thermowell, one for carb stone and then the third can be for racking arm. They look kinda close together so don’t get a big old racking arm as it will hit the temp probe or carb stone and won’t rotate. They’re too close together but that’s too late to change. Just make sure you buy parts that work together, or lose te stone and naturally carb.

no idea what to do with the port way down towards bottom of cone. Maybe a 3/4” tc ball valve to collect yeast? Never seen one there before so just spitballing ideas here.

 

[Qhrumphf]

Ideally that lower port would be your racking arm but it seems like it's a little low for that unless you could find a suitable arm that both gets high enough and rotates enough.

In lieu if that, i would out a second temp probe there.

 

[Nommag]

Thanks for the responses. That is a pain in regards to the lower arm being too low. I was hoping to rack from that. Its also a bit annoying that the ball valves are welded on, not attached with tri clamps. Is it possible to get a raking arm for an existing ball valve?

The tank size I believe is around 71-76 litres and the bottom cone is about 30 litres so the bottom cone is deceptively big.

The top port I believe is 6 inches so I'd need to find a 6inch to 1.5inch lid to put the prv on it

 

[Nommag]

It may pay to add my bil doesn't homebrew, he just welds. He has welded together milk tanks and beer tanks in the past but to spec. I was able to offer no real specs because I've never used a unitank. I just sent him some pictures I found on Google and the information I gathered here and that is what he dropped off. So if there is anything unusual it's not some kind of secret, just something we got wrong

 

[Qhrumphf]

Those are butterfly valves, not ball valves. You won't be able to put anything through them without disabling the valve. If that butterfly is welded on then it's basically useless.

 

[Nommag]

Those are butterfly valves, not ball valves. You won't be able to put anything through them without disabling the valve. If that butterfly is welded on then it's basically useless.

Damn! I'll have to have a yarn with my Bil maybe he can replace it with a tri clover port.

 

[Qhrumphf]

Remove the valve, weld on a TC ferrule. TC racking arm goes through it. Butterfly then connects to racking arm.

If you religiously and repeatedly dump your cone you *may* be able to rack from that port, but that's a long steep cone and you're right at the bottom. Your upper ports would do for a racking arm but you'd need one long enough. If he's gonna custom fab for you you'll want a pretty steep one and may have just accept you can't get full rotation and have the arm be long enough (from either port, really)

Think if your average losses. If you never dumped you might have 10% of your volume be yeast/trub (more if you dry hop heavily). If you dump it properly twice, might knock that down to 3-5%. I'd fill it with those volumes of water and see where it sits in relation to that valve (ie if your normal batch size is 60L put in 3L, have a look, then another 3L. Might be able to sight out a racking arm length that way.