Silver solder

Why didn’t I do this a couple years ago instead of trying to seal bulkhead fittings? I’ll never do that again. This was way to simple and foolproof. Hoping to get the port for my elements in tonight.
To anyone converting a keg, I can reccomend enough, draw your fitting through a tight hole and silver solder. Simple as can be.

Yep. One of my clubmates did this a couple of years ago and it made me realize that silver soldering is fine for a liquid filled container. It never exceeds about 212F and that is far below the temperature needed to liquify solder. Super easy and secure. It is the way to go.

What gas is needed to solder silver?  I doubt propane is hot enough. Will MAPP gas work? What flux is necessary?

When I worked as a radio and TV engineer before retiring and becoming a pro-brewer (yeah, I did that too), we used silver solder to bond copper ground systems for AM radio stations together.  You need at least MAPP gas to get enough heat to melt the silver solder.  Oxygen and Acetylene are better because the get higher temps, however are a bit more dangerous to work with.  Since SS is a pretty good conductor of heat, it will take a while to get it hot enough (because of the large surface area of the keg) to melt the solder so patience is a virtue here.
Caveat:  make sure that you do not have a ball valve that contains plastic or teflon connected to the fitting you are silver soldering. The heat will melt the insides and destroy the valve and they might catch fire as well.

And make sure you heat the fitting, not the kettle.