I'm looking at rounding up some propane tanks to use as storage and a buffer. I'm looking to buy a welder that is capable of welding ports in the tanks without them leaking. I'm just wondering what any of you have used as far as the welding process required for asme grade welding. I would like to buy a good sized mig welder. I have heard that dual shield welding can be used. Maybe the same as intershield welding? Also where would i go to get the ports to weld into the tanks? Kevin