Heat-treating method of weld portion of piping system and heating coil for the heat treatment

摘要

Herein disclosed are a method of heat-treating a weld zone of a piping system, in which the outer wall of a pipe is heated by means of a heating coil, while a coolant is present in said pipe, to establish a temperature difference between the inner and outer walls of said pipe thereby to prevent the weld zone of said pipe from corroding and cracking due to stress, and a heating coil therefor. The aforementioned heating coil is wound on the parent tube and the pipe welding desk generally concentrically thereof thereby to heat substantially uniformly all over the region of said weld zone.