Have a crack in corner of copper firebox (abt 7/8" thick) on a Steam Locomotive. Would like to weld repair same. Looking for general info on electrical process welding same, anyone in midwest area experienced on welding this material in a pressure vessel.

Specifed electrical process, because it would take a huge torch to gas weld on this huge heat sink.

Out of position on a vertical surface, 150# working pressure, should be certified, but not under 49CFR part 230 locomotive inspection requirements.