We didn't need that, of course, but because high pressure steam is so dangerous we used only union welders who were rated master and who already had experience in steam plumbing. I don't remember if there was a special ticket for that, but everybody we hired was interviewed and had to do some welding as a part of it (the equivalent of a leetcode test on the whiteboard I suppose). If it isn't obvious: I was not qualified to usefully interview any of them.

These guys were great to hang around with. go have a beer, horse around, etc with but wow, when they were on the clock all of them (machinists, etc too) were deadly serious. No fucking around.