7.6 gallon fermentation keg modification

[JerryMc]

I have this Kegmenter Fermentation Keg - 7.6 gal. | MoreBeer to ferment under pressure in. I'm thinking to get my welder guy to weld this Stainless Steel Weldless Thermowell - 100 mm - FT-ATW-01 into it so I can get accurate temp readings without having to tape the probe to the side of the keg. I don't want to deal with the plumbers putty David Heath mentions in one of his videos. Would work but looks messy.

I did brew a batch in the keg already and had the temp probe taped on. Not the best solution IMO.

If anyone knows of a reason why I shouldn't do this please let me know.

 

[GilSwillBasementBrews]

The only thing I can come up with is that it says it’s a weldless thermowell so why weld it. But other than that, I don’t see why it wouldn’t work.

 

[Golddiggie]

I'd opt to get one of these (whatever length works best for that keg) welded into the lid. Or get a new lid with the fittings made up.

Straight-Walled Thermowells for Fermenters from Brewers Hardware

Thermowells > Straight-Wall Thermowells

www.brewershardware.com

I've used them in kegmenters while I still had those. Worked very well since the probe was close to the center of the batch (height wise, since I place the thermowell in the center of the cap).

Make damned sure you get this TIG welded in and then passivate the thing after it's done (if the welder doesn't do that for you). Get the thermowell welded from the underside (or the part facing the beer).

 

[JerryMc]

My reason for welding it is to make sure it never leaks pressure. I don't think the lid is the best place to weld it because it would be above the liquid. I'm thinking to put it maybe 5 inches or so from the bottom would be best. The reason I chose this particular thermowell is due to the larger surface area the welder will have to work with and more rigidity so I don't break it off when cleaning. Maybe I'm overthinking it, I dunno.

 

[Golddiggie]

IME, going from the top/lid with a long enough thermowell is the better solution. FAR easier to passivate than something in the side of the fermenter. Plus, you can always get another lid and change things up. Once something is welded into the keg body, you're done. If the hole is F'd up, you just wasted it. Also, welding inside a keg, with a 4" opening is not as easy as welding the lid. I'd had plenty of kegs welded up for fermenting in over the years. Cleaning up after is never fun. For lids, it's 10000000x easier.

Something else to keep in mind. TIG welding something that's treaded makes it more difficult for the person doing the welding. Pretty sure that's true for all processes (not just TIG). Which means you'll need to remove the threads from that weldless thermowell before you make the hole and get it welded. If you don't have a lathe, or access to one, that's not as easy. Especially if you want to make it a true round object once the threads are removed.

 

[JerryMc]

@Golddiggie You think it possible to put a thermowell in this cap? Maybe drill a little under center of the (ar) in warning? Lids a little crowded but I think it'll fit there...

The vessel measures about 12 inches deep so I'm thinking a thermowell about 8" long. The webpage you listed doesn't have an 8 inch length listed. Get a longer one and cut to desired length? TIA

 

[Golddiggie]

I've cut down the thermowells from BH before. Just use a good pipe cutter (I have one I bought for stainless tubing years back that works great).

For the cap you have, pull off the ball lock posts, lock it into a three jaw chuck, and drill into it. I have a rotary table setup with a chuck that can handle 4" OD items without issue. IMO, you don't need the thermowell dead center. Since it's not going all the way to the bottom, just have it where it can fit in among the other items in that cap.

The BH thermowells are 3/8" OD (actual). Last cap I put a hole into, I used a 3/8" end mill (better than using a drill bit since there was zero slop).

If the welder you plan to use has a milling machine, and rotary table (with a three, or four jaw chuck) then he shouldn't have any issue making the hole for you.

If you were in the area I am (Southern NH) I'd tell you to bring it over and we'd get the hole into it. I could even sell you one of the spare thermowells I have (from BH).

 

[JerryMc]

@Golddiggie I have a drill press and I have lettered bits so I'm thinking I can get a very tight fit. I also have a 3 jaw chuck on a crappy lathe and a drill chuck on the tail piece but that would only do a center hole. It won't do offsets. I think I'll clamp it down to the drill press table and drill it. My welder does all types of welding and has all the right equipment but he isn't a machinist.
Thanks for the info, I have a tubing cutter I've cut stainless with before so hopefully no issues.

 

[Brooothru]

Have you considered a weldless bulkhead TC on top of the keg? There's plenty of real estate to mount one (or more) up there. It would be easy to do and would accommodate the maximum 2 bar pressure rating of the keg.

Put in two, one for the thermowell and one for a CoolStix. Instant unitank. Let me know if you do the mod. I've got the same keg and have thought about doing it to use it as a brite tank.

 

[JerryMc]

@Brooothru I have an Inkbird TC-308 WIFI with temp probe. I want to place it inside the fermentation for better accuracy. I decided I wanted it welded in so I would never have any leaks. I know the maximum 2.5 BAR is relatively low pressure and I'll never reach the maximum pressure making beer but it doesn't take much monkeying around to get a leak started especially when the probe has to be at minimum 6 inches in length to insure it reaches the liquid.

As for the CoolStix I don't need that due to placing the keg inside a small fridge with a heat blanket wrapped around it. I discussed this arrangement in another post here: Fermenting under pressure and this worked out fine on my first trial run.

 

[Golddiggie]

@JerryMc If you're going to use letter bits, you'll need to get a .375" reamer to go with the U size bit. You could just get a 4 flute 3/8" end mill (carbide) and use that for final size.

As for your crappy lathe 3 jaw chuck, make sure it can grab something 4" in size. IME, most 'crappy' lathes don't have chucks that can (I had a 7x14 that I don't think it could have grabbed even with it's "4 inch" chuck). "Plan B" could be placing the cap on something sacrificial, and simply clamping everything down to the German standard. You know, Gudentite.

I used my drill press for the first time in over a year this weekend. Drilling holes that needed to be tapped either 1/4-28 or 1/4-20. The collets for my mill (I'm using ER32 collets with an R8 holder, so I don't need to wrench on the drawbar every bit change) to make things easy. I need one more collet that didn't come with the latest 32nd increment set I bought (need the 7/32, not in that set, one is on it's way now). That should hole either a #3 or #7 drill bit.

You'll want to have your drill press spinning as slow as possible. <200rpm is good. <100rpm is even better. Use either cobalt or carbide drill bits. If you spin too fast, you'll case/work harden the 304SS cap and it will be a pain to try and make a hole in it (if you even can). Anytime I drill into (or machine) 304SS I use the 90rpm speed on my mill and work it slow. 4 flute, carbide, end mills are typically what I use. I've dropped not a small amount of $$ on cutting tools. Not to mention work holding, tool holding, and the DROs on the machine. Probably going to get another item for the mill that could be a bit up there in cost too (depends on which option I go with) but it will make setting up on the mill easier/faster.

 

[JerryMc]

@Golddiggie I just bought a carbide 4 flute 3/8" end mill. Thanks

 

[Golddiggie]

@Golddiggie I just bought a carbide 4 flute 3/8" end mill. Thanks

Assuming your drill press has at least a 3/8" chuck. Even my old (as in gone for about a decade now) benchtop had a 1/2" chuck. Current floor model has a 5/8" chuck IIRC. Not that I use it all that much.

 

[apache_brew]

Before you go and touch the lid, what have your results been with the probe taped and insulated to the side of the keg? I ferment in 1/2 bbls and tape the temp probe on the side wall, then tape a 4"x4" piece of scrap R-13 insulation with duct tape over it. Duct tape the heating pad to the other side of the keg as well. The inkbird controls the upright freezer and heating pad. No issues whatsoever with ramping up for diacetyl rests or dropping down for cold crashes. In my opinion, it's not worth the extra effort for this configuration, especially given the results I've had.

That being said, if your welder guy can do stainless tig, and you really want a thermowell, I'd consider welding in a 1/2" tri clamp ferrule into the top of the end cap. 7.42US $ 10% OFF|12.7mm 108mm(3/4” 4.25”)Sanitary Weld Ferrule + Tri Clamp + Silicon Gasket Union Set SS304 Stainless Steel For Homebrew|Pipe Fittings| - AliExpress Get the 12.7 mm one (1/2" OD on the weld connection), it should be long enough for you to drill the 1/2" hole into the end cap, then weld the ferrule to the end cap from the beer side of the connection. this can be done without any filler rod if the clearance is tight (which is easy because you're just drilling a hole to match the ferrule size). now you have a 1/2" tri clamp ferrule sticking upwards out of your keg assembly, grab a 1/2" tri clamp end cap 3.59US $ 10% OFF|3/4"1“ 2” 3“ 4” 6" Tri Clamp SS304 316L Stainless Sanitary Tri Clamp TC Blind Cover End Cap Home Brew Wine Ferrule OD25.4 183mm|Pipe Fittings| - AliExpress and drill/weld your thermowell into that. The tri clamp parts allow you to have sanitary connections and by compartmentalizing the components, you can either use them, or not and just put a cap on.

 

[JerryMc]

@apache_brew Interesting, I absolutely want a thermowell in the cap. I like you're idea, just ordered the parts. Thanks

 

[JerryMc]

Finally finished this small project. Here are a few pics. Passivated with Barkeepers Friend. I still need to clean and sanitize before next use. All things considered I'm happy with the way it turned out.

 

[Brooothru]

That's a good looking mod. Right now the only piece missing for my hop dropper mod of a 7.6 gal kegmenter is for Spike to make their new spunding all-in-one available. Could be this week, I'm told. I got the CoolStix, Top Draw, PRV, piping, etc., all in place. All I need now is the spunding valve. My plan is to use the tank more like a brite, for carbing, crashing and conditioning, and only secondarily as a fermenter. That way I'll have a ton of options to keep the pipeline flowing between the kegmenter, conical and unitank. Really glad I bought a glycol chiller with three output channels.