Note that the price in US$ . I do not know if the US has its own "bliue book" but litigation would sort it all out.

There is at least 1 company supplying Tig Welded Copper boilers, I am assuming that these meet the regulations.

Sorry but I don't know about Mig/Tig Welding for Steel Boilers. (Not sure if the Blue Book specifies method of Welding — My book is not to hand)

I am sure that when the Blue Book is revised, it will take account of the more modern welding technologies that are now available.

Dave

Ady;

Expand them in place. Sometimes use a copper ferrule between tube and tube sheet to help seal.

Welding really started with the Germans in WW2 from what I understand; stays were starting to be welded then, as it's a lot faster than tapping and threading and peaning the ends over.

I used to do a fair amount with full sized stuff in North America; although I still hold my provincial license for "Steam Traction Operator" have not bothered to use it in a good few years now.

I think rolling tubes is easier; when you take the tubes out, you of course have to use a torch to cut tubes just inside the sheets, then carefully remove the remainders. There always ("over here" practice, anyway) a king hole in the front tube sheet; all tubes come out of that hole, and can be "safe ended" and re-used, if ok. Safe ending is just welding on a bit more tube, maybe not worth it for the tubes, but the larger superheater flues it is/was usually done in "excursion" years. (IIRC, you can safe-end flues twice only)

Google "49 cfr 230 steam" should bring up the US rules, Canadian rules are identical, except for the spelling (again, IIRC)

Another JohnS