DIAMETER CONTRACTION METHOD FOR BRANCH PIPE

PROBLEM TO BE SOLVED: To facilitate pullout of a branch pipe 3 by efficiently contracting the diameter of an enlargement work part 3b of the branch pipe 3 fixed to a hole 2 of a pipe support plate 1. SOLUTION: A narrow-width section 3g in one end of the pipe enlargement work part 3b enlarged and fixed to the hole 2 of the pipe support plate 1 is annually heated from the inside of the branch pipe into a red-hot state, the red-hot narrow width section is pulled and made to yield by applying a tensile force to the pipe end so as to be contracted. The same operation is performed on an adjoining narrow width section 3h and the same operation is repeatedly performed by moving the position of the red-hot narrow width section in order after that. The approximately whole area of the pipe enlargement work part 3b tensely attached to the pipe support plate can be thus contracted to facilitate the pullout. COPYRIGHT: (C)2003,JPO