Heat treatment method and device for piping

Abstract

In a method for heat treatment of an existing pipe constituting a piping system, for converting the residual stress at a welded metallic portion and a welding heat influenced portion of the inside surface of the pipe, into a compressive stress and thereby generate the compressive stress in the inside surface of the existing pipe, a coolant is retained in the pipe; an arbitrary portion of the outside surface of the pipe is heated; thereby a temperature distribution little in temperature difference is produced in the wall surface of the pipe at the heated portion; and then the coolant is allowed to flow. By converting the residual stress at the welded metallic portion and the welding heat influenced portion of the inside surface of the pipe, into the compressive stress, stress corrosion cracking generated from the welded metallic portion and the welding heat influenced portion can be suppressed.

1 . A method for heat treatment of a pipe constituting a plant, the method comprising: 
 retaining a coolant in the pipe;    heating the pipe in a state wherein the coolant is retained; and    allowing the coolant to flow after heating.    
   
   
       2 . The method according to  claim 1 , wherein the coolant is water.  
   
   
       3 . The method according to  claim 1 , wherein the pipe is heated to 100° C. or more at an inside surface of the pipe.  
   
   
       4 . The method according to  claim 1 , wherein the pipe constitutes a piping system of a reactor, and the coolant is reactor water.  
   
   
       5 . The method according to  claim 1 , wherein the pipe is heated by induction heating or direct electrical heating.  
   
   
       6 . A method for weld repair of a pipe constituting a plant, the method comprising the steps of: 
 welding a pipe;    allowing water to stagnate in at least a weld-repaired portion of the pipe;    heating the weld-repaired portion; and    allowing the water to flow in the pipe which is being heated.    
   
   
       7 . An apparatus for heat treatment of a pipe containing Cr, the apparatus comprising: 
 a circulating system;    a heating coil for induction heating;    a spacer for keeping the heating coil at a constant distance from an outside surface of the pipe; and    a transformer and a power supply for applying an electric current to the heating coil.