Hitachi, Ltd.

Tsukasa Ikegami

Tasuku Shimizu

Isao Sugihara

Kunio Enomoto

Shinji Sakata

Nobuo Shimizu

Wataru Sagawa

Terunobu Koike

A method for improving residual stress in a circumferential weld zone of a piping and the like which includes preventing deformation of the weld zone, and causing a local expansion or contraction of a portion of the piping axially spaced from the weld zone thereby effecting a plastic working so as to increase or decrease the diameter of piping. The method can effectively be applied to apparatus and pipe system which are used in a corrosive environment and under action of a static or dynamic outer load.

Method of improving residual stress in circumferential weld zone

The invention relates to a method of heating a piping arrangement and a heating coil used in the heating process by heating pipes through a high frequency wave induction. A spacing between the pipe outer surface and the heating coil is varied in compliance with a change in configuration of the heating coil. According to the invention, even if the coil configuration is particularly changed, it is possible to heat the pipes uniformly to obtain a uniform temperature distribution.

Method of heating piping arrangement and heating coil

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.

Heat-treating method of weld portion of piping system and heating coil

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Hitachi, Japan

Tsukasa Ikegami