I know for sure that this is possible to copy and fabricate the corroded element of a pipe without its dismantling in order to replace later when it is ready. How is this achieved? For example, we need to make a copy of one of these elements so that it takes only to remove the old one and fit the new.
The common practice is to remove the old one, weld it to the deck, attach the new set of flanges, then to remove and fit it back. After that to fabricate the new piece and finally to install it. Like here:
The pipe diameter can reach 300 mm, its thickness 15 mm. So the 0.5 mm clearance can not be compensated.
But once it was impossible to remove the leaking pipe and the fitters came, measured the element and fabricated it, brought it and it fitted perfectly in place of the old pipe..
Does anybody know such technique?