Sterile Welding Ball Valve

I'm sure this has been asked before, but I can't seem to find an answer to my specific question. Here goes:

I bought a stainless steel 10.5 gallon brew kettle and want to add a stainless 1/2" ball valve. I've heard mixed reviews of the weldless add-on valves and my neighbor (a plumber and steelworker) has offered to weld one onto my kettle for me instead. However, I've read that you need to be careful to have a sterile weld. Does "sterile" refer to eliminating any places for microbes to hide near the weld site (i.e., a smooth weld) or does "sterile" mean something else?

Thanks in advance for the help!

A Newbie

Its sanitary welding, where you use a back purge and a few different techniques. Your boil kettle does not need to be welded this way.

If you are modifying a fermenter or anything that touches your beer after it is cooled then it is recommended to use sanitary welding techniques.

When you get your fittings welded on just purge the rear of the weld, or you can do what I do instead of wasting argon to fill the kettle and welding it out of position. I use solar flux B on the back side of the weld after I put a small tack to hold it in place. I welded the first one without. It would be nice to be able to make a copper ring on the backside of the weld, that would make life soo much easier and you wouldn't have the carbide precipitation from no purge.