Method of welding lined pipe

Abstract From the Canadian patent

The ends of two sections of lined pipe (e.g. polyurethane lined steel pipe) in which the lining, terminates a definite distance from each pipe end are butted together, with an internal concentric sleeve spanning the unlined pipe ends and defining an annular hollow casting space at the area to be joined. The butted ends are then welded together at the joint. Thereafter a curable liquid polymer (e.g. liquid polyurethane composition) is introduced into the casting space through an opening in the unlined section of pipe, and cured to a solid state in situ. The opening is then plugged.