Soldering Stainless - Adding Ss Fittings To Keggles -

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in true tight arse brewer fashion i have been mucking a about with soldering stainless to stianless and brass / copper to stainless.
in someways to save on all the extra "weldless" fittings and also it looks nice and neat

i am building a 3V rig (in progress) electric HLT and HERMS and maybe electric boiler.
I aim to solder in all the fittings including bushing or lock nuts for screw in elements etc.
at this stage i have just had a couple of practice goes but it seems promising

there are a few threads on AHB about it, some good discussion but no pics...

a very good thread over at HBT with pics and a very good video using a "dimpling" method

i have to create my dimple tool but here are some pics of what i did today on the scrap keg lid
i used a BBQ gas powered torch i have (propane torch) lead free solder (aquasafe 100 - copper/tin)
for flux i used hydrochloric acid from my pool as the real flux i had was not "right" for ss work. (the hydro acid worked well but i will by the right stuff)
i created a RING of solder, sanded bright the fittings and base, wiped it all with alcohol and fluxed it up fairly wet

i heated the base 1st then the fitting, back to the base and then the fitting till the solder melted and flowed.
heating a larger area of the base stopped it sucking out the heat, the keg lid is thick and needs some heat
in the dimpling vid the pot is very thin and you see he only heats the fitting

this is not brazing or high silver content, but really just soft soldering (lead free or soft silver solder +-8%)

tomorrow i was going to do the drain on my HLT in the base of the keggle

here are some pics and a video of me hitting it with a hammer.
vid hammer test (thats water flying off when hit not metal)
pics are brass 1" bush
stainless elbow
1/2 copper pipe though hole (failed hammer test after i sanded it flush, prior to sanding it held very well)



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From what I can tell you are using threaded fittings, so what additional benefit (compared to weldless fittings) does all the effort of soldering them in give you?
An assured water-tight seal?
I believe the op said he wanted to save a bit of money and achieve a neater look and I would guess that the threaded fittings are for practise and he'll be using something else for real. Otherwise, its always nice to see a bit of soldering. :)
Man, I was going to ask how strong those joins would be but then I watched you smacking them with a hammer.

Question answered.
Soft soldering to Stainless isnt all that hard but its a bit of a knack and practice makes it look easy.
Key is getting a good wetting of the solder to the stainless first, you need what is called inter granular penetration, unfortunately this requires temperatures up near where the solder starts to oxidise badly, good wetting of the stainless, clean off flux and make the joint to the copper or brass which happens much cooler.

The one problem you are likely to run into is that the solder tends to crack over time. This is caused by the different rates of thermal expansion. The fact that you are putting two or three different metals together makes this worse. With the two metals expanding at different rates, the layer of solder between the two is subject to a lot of sheer force and will eventually crack.
If you do Stainless to Stainless the long term prospects are much better far less stress, might be worth buying a couple of stainless nipples or sockets (pretty cheap) cutting them in half and making them what you connect to the keggle rather than copper/brass
I think a clear RTV would make a threaded fitting look better.

My son has take 3 years of welding classes and says, "don't try it unless you do it for a living".

Thin metal, high carbon, easy to burn holes and make uglier...also chrome gas is toxic.

My father in law built fire engines for 40 years. I'll ask him.
Have done with succes. The trick is to get the right flux, there is a special flux for stainless to brass, just cant remeber the name of it, it is made by CIG
@ wolfy

No additional benefit really, I am just not keen on having all the weldless fittings inside my system.
I think whatever i build it is going to need threaded fittings used.
As using tube and compression fittings to avoid threads inside pipe is beyond my budget (all triclamp etc)
I might try a bit of stainless pipe to stainless and see how it goes. if i get some annealed SS tube i might be able to flange the pipe and dimple the keg
giving a solid join ? That would allow a compression fitting / barrel union on the out side


Great input thanks, i have considered the metal fatigue issue and aim to use stainless to stainless and use 8% silver solder.
I have seen solder used in similar conditions last years and have also seen it fail just as you describe.
Thanks for the input about thermal expansion. i thought the "slow" temp change situation may negate that a little ?
Going to give it a go and if i get multiple failures i would move to welding or weldless i guess...

@ Ducatiboy

"staybright for SS" or somthing is the go, going past the welding shop today to have a look-see the acid worked surprisingly well <_<

I aim to add to the dimple method in the linked video up ^^ as i think it will add extra strength and longevity.

Thanks for the comments, I did not intend it to be a solution for everyone or best practice, just something i tried after doing some reading and thought it might be helpful to someone and show an idea (not a new one). i will post a few pics as i go.

@ wolfy

No additional benefit really, I am just not keen on having all the weldless fittings inside my system.
Fair enough, my soldering skills are such that the effort and result would not be worth the additional cost of a $2 nut and washer. :)
My budget is also does not stretch to stainless compression fittings, so I understand where you are coming from.
In my case a bit of creative design and some silicon hose has hopefully eliminated the need for them.
I silver soldered SS fittings on the last brewbot.

Was easy enough to do and turned out ok.

One advantage over weldless fittings is just the cost. You need less fittings which are pricey in SS.

So instead of a nipple, socket and tap, I just soldered the tap straight to the kettle. Or cut a single socket in half and soldered on.




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