Method for repairing heat recovery steam generator tube-to-header damage

Abstract

A method for repairing a heat recovery steam generator (HSRG) header to tube attachment damage, includes providing an access window in the header opposite the damaged header to tube attachment location; removing the header to tube attachment damage; inserting a tapered stub tube into a header penetration centered axially immediately over the tube; effecting a profile weld between the header and the tapered stub tube at the header penetration from the inside surface of the header; welding the tapered stub tube to the existing tube through the header inside diameter; welding shut the access window; and completing a post weld heat treatment of all the welds.

1 . A method for repairing header to tube attachment damage, comprising:
 providing an access window in a header opposite the attachment damage location;   removing the attachment damage;   inserting a tapered stub tube into a header penetration centered axially immediately over the tube;   effecting a profile weld between the header and the tapered stub tube at the header penetration from the inside surface of the header;   welding the tapered stub tube to the existing tube through the header inside diameter;   welding shut the header access window; and   completing a post weld heat treatment of all welds.   
   
   
       2 . The method of  claim 1 , including preparing said tube for welding with a cutting assembly having a cutting tool prior to inserting the tapered stub tube into the header penetration. 
   
   
       3 . The method of  claim 2  wherein said preparing the tube for welding with a cutting assembly having a cutting tool comprises:
 replacing the cutting tool with an end-prep tool;   positioning the end-prep tool; and   chamfering the end of said prepared tube.   
   
   
       4 . The method of  claim 3  wherein the end-prep tool is a dual tool cutter head. 
   
   
       5 . The method of  claim 1 , including heating the header, stub tube, and tube after inserting the tapered stub tube into the header penetration. 
   
   
       6 . The method of  claim 1 , including preparing the header and stub tube for welding prior to effecting a profile weld. 
   
   
       7 . The method of  claim 6  wherein said preparing the header and stub tube for welding comprises:
 mounting an EDM assembly with a profiled electrode to a base plate; and   chamfering the header and top of the stub tube.