Keg Brazing

Well now I finished cutting the tops out of my kegs i'm about ready to start getting the fittings installed for sight glasses and ball valves.

I decided that i'm going to go with brazing since I don't have a welder and everyone i've called down here doesn't seem to want to attack it. Also would be cool to learn how to do it myself.

I'm just stuck on which direction to go

A. Drill hole in keg and place half coupling halfway through the hole and then braze into place. My only fear with this setup is it won't be very strong since nothing is sitting up against the keg wall. But I think it would be cleaner looking and be just like the welded versions.

B. Drill hole in keg and place stainless pipe nipple with half coupling on the inside of the keg, would be just like the weldless kits except no o rings and no washer on the outside. I know this method is the strongest but it'll probably look ugly.

I'm going to be doing this for both the 1/2" in/out connections and the 1/4" sight gauge/temp connections.

I don't think there is anywhere local that I can get cadmium free silver solder so i'll have to order the 76955A72 silver solder from mcmaster.



Any opinions?

Check with the local welding supply companies to see if they carry Harris Safety Silv 56 silver braze in 1/16 dia. size, and the stay silv white flux to go with. Should be around $40 or less for both. Would suggest a female pipe by 1/2" compression fitting like this from 1/2” Tube x 1/2” NPT Female Connector 316 SS as the shoulder on the fitting will give enough area to prevent cracking under normal use.

damn they are proud of the connector. so your saying to put the compression fitting inside the keg and leave the coupling side outside the keg, that way it could be used for a pickup tube as well right?

Yes, with compression fitting inside it takes up less room and dip tube connection can be finger tightened after initial swageing. Have tried soldering tubing into kegs but it did not have enough bonding area to prevent joint cracking under normal use. Installing pipe or tubing through keg wall might work if one used a thicker piece of material like a washer or backing plate to increase joint thickness.

I would also contact companies that make duct work. that who is doing mine. they weld stainless all the time

kladue said:

Yes, with compression fitting inside it takes up less room and dip tube connection can be finger tightened after initial swageing. Have tried soldering tubing into kegs but it did not have enough bonding area to prevent joint cracking under normal use. Installing pipe or tubing through keg wall might work if one used a thicker piece of material like a washer or backing plate to increase joint thickness.

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Hmm, I wish that damn connector wasn't so expensive, i'll have to price out what it would be to use a half coupler with a compression fitting and a pipe nipple to see if comes out cheaper in the long run

monty73741 said:

I would also contact companies that make duct work. that who is doing mine. they weld stainless all the time

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thanks i'll give that a try, I swear even though I live in such a huge city it's such a pain to find anything useful.

I've brazed/silver soldered several nipples onto pots and haven't had a problem. SS Pots (10 gal), not kegs though. I did put some fillet in, up the nipple threads. I've got the ball valves threaded down pretty tight on the outside and the fittings on the inside is tightened down pretty well so there is not much flex possible for the nipple. I am carefull to not put a lot of stress in the fittings. I never handle the pots by the fitting.

pjj2ba said:

I've brazed/silver soldered several nipples onto pots and haven't had a problem. SS Pots (10 gal), not kegs though. I did put some fillet in, up the nipple threads. I've got the ball valves threaded down pretty tight on the outside and the fittings on the inside is tightened down pretty well so there is not much flex possible for the nipple. I am carefull to not put a lot of stress in the fittings. I never handle the pots by the fitting.

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What solder did you end up using?

Man I can't remember. I'll see if I still have some left. I bought a small packet that had 3 ~10" flux coated (blue) rods. I vaguely recall buying it twice, once from a Sears of all places, and the second time I think was my local welding shop

yeah I think I remember reading something about the blue rods in another thread, thanks.

Can't remember all the details but I'll try. A guy on the green board, aka brewboard, had a nice method. He drilled and tapped the keg to recieve a male ss fitting, then he threaded the fitting into the keg and silver soldered the joint to make it leakproof / stronger. This seemed like a great way to go about this because you are making it a mechanical joint (stronger) and also sealing it w/ the solder. I would imagine this would be plenty strong!

Search brewboard for silver solder??

thats pretty much the plan at this point. I ordered the stainless fittings and will try brazing them in sometime this week. I am going to see if I can find some of those blue brazing rods.

jcdillin said:

thats pretty much the plan at this point. I ordered the stainless fittings and will try brazing them in sometime this week. I am going to see if I can find some of those blue brazing rods.

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Make sure you keep us updated with pictures and whatever. I'd be interested to see how this comes out for you as I'd like to try something similar on another keg I have.

Update

Well I found the blue brazing rods at Home Depot and they were only like $3 for a pack of 2.

So I practiced on some scrap metal and was able to get it to tin pretty well but when I tried the same thing on my keg it was pretty much impossible to get anything to tin and I ended up overheating the keg. Now I have small stress cracks on the inside from the extreme heat not to mention a very lumpy braze. Looks like a 5 year old learning how to solder .

Even with a crappy braze the connection is super strong and I feel very confident that it will be a great solution.

At least I did this on the top connection and not the bottom so the keg can still be used as a boil kettle. I am going to practice a bit more on washers and stuff and try to find out where I went wrong.

Focus all of your heat on the fitting. I didn't even think about putting any heat to my pots until I already had the fitting heated and some filler melted to it. Then I would move the heat down to the pot, and the filler with it. Then I moved around the fitting with the flame pointing mostly at the fitting, but giving just enough heat to the pot so the filler would flow on it.

If you are going to practice, make sure you use pieces of different mass. Maybe try brazing the head of a large bolt to a thin washer to approximate your fitting and the kettle

Ok thats a good tip

Thanks!

One other question

Do you touch the filler rod to the piece and let the work melt it or do you melt it with the flame and let it drop onto the work?

Do you touch the filler rod to the piece and let the work melt it

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or do you melt it with the flame and let it drop onto the work?

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Unlike soldering, when you braze you actually get some of the brazing rod to "soak" into the metals being joined. This will only happen if the metal is hot enough. Back in High School welding shop one of the tests of your brazing skill was to braze two items together at a 90 degree angle and than whack it with a large hammer. If you did a good job, the metal would split away from the joint. If you didn't, the piece would split right at the braze and go flying.

this may help some who want to braze rather then solder their valves.

[youtube]ZojIpKCo4TQ[/youtube]

It takes to much heat to brass braze stainless (1600 deg) vs. (1200 deg) for 56% silver. Brass works well on carbon steel scrap but stainless turns black and sometimes sugars at the brass brazing temps.

how would you get that flame going underneath a fitting inside a keggle? That space is tight. I can hardly fit a wrench in there! Do they make bent torches and bent rods? How would you see to know you had it right?

(btw, I used weldless cause I'm a pansy and drilling holes in my keggles was quite enough for me)

kladue said:

It takes to much heat to brass braze stainless (1600 deg) vs. (1200 deg) for 56% silver. Brass works well on carbon steel scrap but stainless turns black and sometimes sugars at the brass brazing temps.

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hmm that makes sense, everything i've been reading says that brazing with silver is right at the edge where stainless can lose it's chromium and cause stress cracks. Which is what I saw on my overheated connection.

I may end up silver soldering this but brazing seemed much stronger and was the logical choice. I wish I just had a tig welder and could just do it that way. But I only have a cheapo flux cored mig.

The 1200 deg F solder is right at the limit for most 304SS kegs, much hotter then the chrome creates a tight black oxide/carbide that causes big problems. Usally you can sand the metal clean and start over, use a flux like stay-silv white, or for bigger joints and more heat use the stay-silv black. Always flux both sides , parts, and at out to at least 1 inch away from the joint to save the surrounding metal from burning during brazing.

I soldered my fittings to my kegs. I know you were talking about brazing and not soldering (right?) but it's worked well for me.

Used Harris Stay-Brite (not Sta-Brite 8) solder and Stay-Clean flux. I tapped the holes just big enough for the threaded fittings to thread tight into the hole, then I soldered it together.

Not as strong as brazing in theory, but the tensile strength is plenty in practice for what I'm doing. I wouldn't solder a load-bearing part like a frame piece, but for quick-connect fittings, soldering with high-strength solder works fine.
-keith

I had success with Dyna-Grip 430 silver soldering kit. I think the 430 is the melting temp. It was $20 at the welding supply shop but I did see the Stay Brite kit for $5. Counter guy told me the $20 was better and being no expert, I paid. In any case, if you can solder copper tube fittings, you can use this stuff. I'd suggest a mapp gas torch though but the bottles fit regular propane torches.

Very interesting, does it seem strong? Did you just thread it in and solder from there? I may have to see if I can find a welding supply shop and pick some up.

I just set mine up as weldless for the time being so I can practice some AG brews and then i'll worry about getting it soldered up later on.

I didn't do it for kettle bulkheads but I wouldn't hesitate to do so if you can't find a cheap welder to have it TIG'd. I have found that silver soldering is best used when you can create a pretty tight gap between parts. I tried filling a 1/16th inch gap and the solder just runs out. I can see why keeping the hole small and threading the fitting in would be ideal. You could also just remove the Orings from the weldless and tighten until the fittings are touching the kettle wall.

I pretty much did what Bobby_M is talking about.

The male fittings going into the keg hold fairly tight on their own without soldering, but certainly not water-tight. The solder just makes it that much stronger.

I did have one fitting that was fairly loose. THAT was a b1tch to finally get soldered - solder kept dripping through the back side. It turned out ok, and holds strong enough for a quick disconnect and ball valve. The body of the fitting was next to the keg, but the threads couldn't grab well.

I can't stress enough how important prep-work and a good flux are. Plus heating the work properly. Certainly hot enough, but not too hot - which you figure out quickly after a few attempts that discolor metal but don't make the solder stick too much.

But given that Stay-Brite (or SB 8), or Lennox 96/4 (or 94/6) solders are used in HVAC applications that have to keep pressurized refrigerant in, they seem to perform well enough. I've "chiseled" the solder joints a little to pretty them up and get rid of excess solder, and the high-strength stuff doesn't scrape off nearly as easy as regular 60/40 lead solder.
-keith