I worked with a company called GEA Air exchangers back in the 80’s, they made giant cooling radiators for power stations. These consisted of hundred of 1” finned cooling tubes welded into 18” diameter round end boxes. The brought in specialist welders to tig weld the huge nest of tubings, that were so closely places it was impossible to even see where they needed welding. Row after row went in, welded as they were installed, using a variety of real oddball shaped hand sets, and when pressure tested to some astronomical pressure they never had a leak, not once. If they did have it would have meant basically tearing dozens of tubes out to effect repairs. Those welders were on £100 a day, back in the 70’s. I was on about £25 a week as an apprentice. My part of the company closed down in 1987, I got laid off, but the cooling company is still there, called something like Spirogills now.