To make the residual stress in a weld metal zone and a weld heat-affected zone on inner faces of piping compressive stress.
A heat treatment device in this piping system is formed by wrapping a heating coil whose sectional form length along a radial direction of a pipe 1a is shorter than that along the central axis of the pipe 1a around the outer peripheral surface of the pipe 1a two or more times after assembling the piping system and is so constituted that a cooling water circulator 19 is used to allow a cooling fluid to flow inside the pipe 1a. A high-frequency heater with the heating coil, a power source and a transformer 16 causes the temperature difference between the inner and outer faces of the pipe 1a. A controller 18 is constituted so as to control the temperature distributions in the circumferential and axial directions of the pipe 1a based on the temperature in a heated zone detected by a thermo-couple 22.
IDE KAZUMASA
SAITO HIDEYO
HAYASHI SHOJI
Manabu Inoue