I once saw a guy use a bolt on a vertical pipe with differnt wall thicknesses.   He put the put the pipe in the clamp and welded a bolt in the gap.  Took the pipeclamp off and cut the top and bottom with an oki beveler.  On the bottom was hooked up too a strap and excavator.  Some shop tests here do this too see what you do know.  Over most companies that deal with pipe here also deal with the refineries.
robert