A heat exchanger and a method of manufacturing it

Abstract

The wall of the water chamber is welded to the tube plate via a connection ring projecting from the tube plate. The wall of the water chamber is welded to the tube plate after the bundle of tubes has been secured to the tube plate. The connection ring presents a length in the axial direction that is equal to or greater than 250 mm.

1 . A steam generator, comprising: 
 a bundle of tubes,    at least one tube plate in the form of a substantially circular disk having an axial direction and pierced between first and second faces by openings, said openings receiving end portions of tubes of the bundle to constitute connections between the end portions and the tube plate,    an outer casing of substantially cylindrical shape around the axial direction and enclosing the bundle of tubes and welded to the periphery of the first face of the tube plate,    at least one water chamber comprising a substantially circularly symmetrical wall,    a cylindrical connection ring axially projecting from the tube plate, the connection ring having a first axial end lying substantially in the plane of the second face of the tube plate and having a second end that is welded to the wall of the water chamber,    the connection ring having a length in the axial direction between its first and second ends that is equal to or greater than 250 mm to prevent heat damage to the connections between the tubes and the tube plate during welding of the wall of the water chamber to the second end of the connection ring or during a subsequent relieving stress treatment of the weld between the wall of the water chamber and the second end of the connection ring.    
   
   
       2 . A steam generator according to  claim 1 , wherein the connection ring is of a length equal to or greater than 270 mm.  
   
   
       3 . A steam generator according to  claim 1 , wherein the connection ring is of a length equal to or greater than 400 mm.  
   
   
       4 . A steam generator according to  claim 1 , wherein the tube plate has a diameter between approximately 3-4 meters.  
   
   
       5 . A steam generator according to  claim 1 , wherein the tubes have a U-shaped form, and wherein the steam generator has a single tube plate and a single water chamber with a circularly symmetrical wall, and further wherein the wall of the single water chamber is welded around its periphery to the second end of the connection ring.  
   
   
       6 . A steam generator according to  claim 5 , wherein the tube plate has a diameter between approximately 3-4 meters.  
   
   
       7 . A steam generator according to  claim 5 , the steam generator having a top portion of diameter greater than a bottom portion, the bottom portion comprising said single tube plate and said single water chamber.  
   
   
       8 . A steam generator according to  claim 6 , the steam generator having a top portion of diameter greater than a bottom portion, the bottom portion comprising said single tube plate and said single water chamber.  
   
   
       9 . A steam generator according to  claim 5 , the tube plate further comprising a annular flange which protrudes radially.  
   
   
       10 . A steam generator according to  claim 1  wherein the tubes are straight tubes connected at their respective ends to first and second tube plates, the steam generator having a first water chamber with a wall welded to the first tube plate, and a second water chamber having a wall welded to the second tube plate via respective connection rings axially projecting from the first and second tube plates.  
   
   
       11 . A steam generator according to  claim 1 , wherein the connection ring of the tube plate is integral with the tube plate.  
   
   
       12 . A method of manufacturing a steam generator comprising a bundle of tubes, 
 at least one tube plate and at least one water chamber, the tube plate being in the form of a substantially circular disk having an axial direction and pierced between first and second faces by openings for engaging and securing end portions of tubes of the bundle,    a water chamber with a substantially circularly symmetrical wall, and    an outer casing of substantially cylindrical shape around the axial direction and enclosing the bundle of tubes,    the method comprising the steps of:    providing the bundle of tubes, the tube plate and the water chamber, the tube plate having a connection ring axially projecting from the periphery of the second face, the connection ring having a first end engaging the tube plate substantially in the plane of the second face and a second end for welding to the wall of the water chamber;    securing the tubes of the bundle in the openings of the tube plate;    butt welding the wall of the water chamber to the second end of the connection ring of the tube plate having the tubes of the bundle secured thereto; the connection ring having a length in the axial direction between its first and second ends that is equal to or greater than 250 mm to prevent heat damage to the connections between the tubes and the tube plate during welding of the wall of the water chamber to the second end of the connection ring or during a subsequent relieving stress treatment of the weld between the wall of the water chamber and the second end of the connection ring; and    relieving stress in the weld connecting the wall of the water chamber to the connection ring of the corresponding tube plate by heating the welded zone.    
   
   
       13 . A method according to  claim 11 , wherein said length is equal to or greater than 270 mm.