Soldering 1" Locknut to outside of Stainless Steel Kettle to connect element

[gmcardle]

So I recently converted my 70L stainless steel pot into an electric kettle using the old Grainfather control box connected to an element I purchased online along with a few other essential parts. I've drilled the hole required to run the elements treads from inside the kettle through to a metal junction box on the outside of the kettle. Initially I used a silicon O ring to seal around where the element meets the kettle wall along with plumbers tape on the treads and although it appeared to work/seal, after testing the setup initially I began to see droplets of water on the other seal once it began heating up! As this is too close to the wiring I don't want to take any further changes with a weldless solution, to be honest the hole I made isn't the cleanest either!!!

So after a little research I believe I can solder the 1" S/S locknut to the outter side of the pot and attach the element that way (similar to attached images I found on Google). Now I've never done anything like this and just want to get advise on the following:

A. What food safe flux should I use with silver solder and where can I get it? (or do I need with D below?)
B. How long will the solder weld hold for (I've read that it can hold for up to 2 years, can it just come apart then)?
C. Should I use a solder gas flame/pen or electric solder iron or this?
D. Will this silver solder work? https://www.amazon.co.uk/MG-Chemicals-SAC305-Copper-Diameter/dp/B003D8O7UA/ref=sr_1_1?ie=UTF8&qid=1499953800&sr=8-1&keywords=silver+solder

BTW: I visited a stainless steel sanitary welder in Cork to be told 'that a s/s weld could potentially distort the treads on the locknut due to the heat during the weld!" and a s/s weld job could cost €40-€60

As I said, never done anything like this so advise greatly received.

IMAGES ATTACHED ARE NOT MINE - ONLY REFERENCE IMAGES I FOUND ON GOOGLE.

[Shanna]

Can't comment on the welds as I don't have direct experience. However I would think you want to get the nuts welded in place without the heating elements as you would want to be able to replace the heating elements. I had a similar problem to yourself and I used a silicone oring, loads of ptfe tape & also this stuff.

https://www.fernox.com/plumbing-consumables/ls-x-external-leak-sealer-50ml

It's foodsafe, won't react with wort & crucially while it makes a seal you can remove it by pealing it off if required. I had a drip leak that I could not fix & that stuff nailed it for me.

Shanna

[gmcardle]

Can't comment on the welds as I don't have direct experience. However I would think you want to get the nuts welded in place without the heating elements as you would want to be able to replace the heating elements. I had a similar problem to yourself and I used a silicone oring, loads of ptfe tape & also this stuff.

https://www.fernox.com/plumbing-consumables/ls-x-external-leak-sealer-50ml

It's foodsafe, won't react with wort & crucially while it makes a seal you can remove it by pealing it off if required. I had a drip leak that I could not fix & that stuff nailed it for me.

Shanna

Thanks Shanna! That sounds like a very good option indeed and I think that could do the tick!!!

[gmcardle]

https://www.fernox.com/plumbing-consumables/ls-x-external-leak-sealer-50ml

It's foodsafe, won't react with wort & crucially while it makes a seal you can remove it by pealing it off if required. I had a drip leak that I could not fix & that stuff nailed it for me.

Shanna

So it's absolutely 100% ok to use this stuff on the inside of the kettle? What I am going to try is using lots of PTFE on the treads, exchange my s/s 1" locknut for one with an O-Ring Groove and use a proper O ring rather than the silicone ring that came with the element and then seal around everything once tightened using LS-X?

[Shanna]

https://www.fernox.com/plumbing-consumables/ls-x-external-leak-sealer-50ml

It's foodsafe, won't react with wort & crucially while it makes a seal you can remove it by pealing it off if required. I had a drip leak that I could not fix & that stuff nailed it for me.

Shanna

So it's absolutely 100% ok to use this stuff on the inside of the kettle? What I am going to try is using lots of PTFE on the treads, exchange my s/s 1" locknut for one with an O-Ring Groove and use a proper O ring rather than the silicone ring that came with the element and then seal around everything once tightened using LS-X?

Instructions say it okay to use it with drinking water. I can't 100%.say it's okay with wort due to the acidity. However I reckon I have used about 5 grams of it smeared over the inside of two heating elements. I have done about 10 * 30 ltr boils & have not noticed any off flavours or any health issues. Other option is to try & fabricate a larger home cut oring from a silicon baking sheet. Don't spare the ptfe tape either 😁

Shanna

[Beerbuddha]

I tig welded the nut onto my keg. It did not cause issues with the threads. But the stainless nuts I bought in e bay where crap stainless and rusted soon after installation. So leave them in water for a day or two to make sure they are good quality. I had to cut them out and then weld in a flat plate with new nut to cover the damage caused by removal.

[SkiBeagle]

Weldless could be an option. Something like https://www.brewbuilder.co.uk/weldless-triclamp-bulkhead.html