Heat exchanger and a method of manufacturing it

Abstract

The wall ( 6 ) of the water chamber ( 5 ) is welded to the tube plate ( 4 ) via a connection ring ( 10 ) projecting from the tube plate ( 4 ). The wall ( 6 ) of the water chamber is welded to the tube plate ( 4 ) after the bundle of tubes ( 3 ) has been secured to the tube plate ( 4 ). The connection ring ( 10 ) presents a length in the axial direction that is not less than 300 mm and that is preferably about 370 mm.

1 . A heat exchanger, in particular a steam generator, comprising a bundle ( 3 ) of tubes ( 9 ), at least one tube plate ( 4 ,  4 ′,  4 ″) in the form of a generally circular disk pierced between first and second faces ( 4   a  &  4   b ,  4 ′ a  &  4 ′ b ,  4 ″ a  &  4 ″ b ) by openings ( 8 ) for receiving and securing end portions of tubes ( 9 ) of the bundle ( 3 ), an outer casing ( 2 ,  2   a ,  2   b ) of generally cylindrical shape enclosing the bundle ( 3 ) of tubes ( 9 ) fixed to the periphery of the first face ( 4   a ) of at least one tube plate ( 4 ′,  4 ′,  4 ″), and at least one water chamber ( 5 ) comprising a circularly symmetrical wall ( 6 ,  6 ′,  6 ″) secured by welding to the periphery of the second face ( 4   b ) of at least one tube plate ( 4 ) via a cylindrical connection ring ( 10 ,  10 ′,  10 ″) projecting from at least one tube plate ( 4 ,  4 ′,  4 ″), having a first axial end lying substantially in the plane of the second face ( 4   b ) of the tube plate ( 4 ,  4 ′,  4 ″) and having a second end ( 10   a ) that is free for connection purposes, the outer casing ( 2 ,  2   a ,  2   b ), the at least one tube plate ( 4 ,  4 ′,  4 ″), and at least one water chamber ( 5 ) being assembled together about a common axis by welding, wherein the connection ring ( 10 ,  10 ′,  10 ″) for connecting to the wall ( 6 ,  6 ′,  6 ″) of the water chamber ( 5 ) is of a length in the axial direction between its first and second ends of not less than 300 mm.  
   
   
       2 . A heat exchanger according to  claim 1 , wherein the connection ring ( 10 ) for connecting the tube plate ( 4 ) to the water chamber wall ( 6 ) is of a length substantially equal to or greater than 400 mm.  
   
   
       3 . A heat exchanger according to  claim 1 , constituting a steam generator comprising a bundle ( 3 ) of U-shaped tubes ( 9 ), a single tube plate ( 4 ), and a single circularly symmetrical wall ( 6 ) for a water chamber ( 5 ), wherein the wall ( 6 ) of the water chamber ( 5 ) is secured around its entire periphery to the free end ( 10   a ) of the connection ring ( 10 ) of the tube plate ( 4 ), said ring having a length of not less than 300 mm.  
   
   
       4 . A heat exchanger according to  claim 1 , constituting a steam generator having straight tubes connected at their respective ends to first and second tube plates ( 4 ′,  4 ″), having a first water chamber with its wall ( 6 ′) secured to the first tube plate ( 4 ′), and a second water chamber having its wall ( 6 ″) secured to the second tube plate ( 4 ″) via respective connection rings ( 10 ′,  10 ″) of the first and second tube plates ( 4 ′,  4 ″), wherein the wall ( 6 ′) of the first water chamber and the wall ( 6 ″) of the second water chamber are secured around their peripheries respectively to the free end of the connection ring ( 10 ′) of the first tube plate ( 4 ′), and to the free end of the connection ring ( 10 ″) of the second tube plate ( 4 ″), each of said rings having a length of not less than 300 mm.  
   
   
       5 . A heat exchanger according to  claim 1 , wherein the cylindrical connection ring ( 10 ) of at least one tube plate ( 4 ,  4 ′,  4 ″) is made integrally with the tube plate ( 4 ,  4 ′,  4 ″), which tube plate is in the form of a circular disk.  
   
   
       6 . A method of manufacturing a heat exchanger such as a steam generator comprising a bundle ( 3 ) of tubes ( 9 ), at least one tube plate ( 4 ,  4 ′,  4 ″) in the form of a generally circular disk pierced between first and second faces ( 4   a  &  4   b ,  4 ′ a  &  4 ′ b ,  4 ″ a  &  4 ″ b ) by openings for engaging and securing ( 8 ) end portions of tubes ( 9 ) of the bundle ( 3 ), and an outer casing ( 2 ,  2   a ,  2   b ) of generally cylindrical shape enclosing the bundle ( 3 ) of tubes ( 9 ), the outer casing ( 2 ,  2   a ,  2   b ), the at least one tube plate ( 4 ), and the at least one water chamber ( 5 ) being assembled together about a common axis by welding, the method consisting of the steps of: 
 using forging and machining to make at least one tube plate ( 4 ,  4 ′,  4 ″) having a connection ring ( 10 ) projecting from the periphery of one of its faces ( 4   b ) that is to constitute the second face of the tube plate, the connection ring ( 10 ) being coaxial about the same axis as the tube plate ( 4 ,  4 ′,  4 ″), being of a length not less than 300 mm, having a first end engaging the tube plate substantially in the plane of the second face ( 4   b ,  4 ′ b ,  4 ″ b ) of the tube plate ( 4 ,  4 ′,  4 ″), and having a second end ( 10   a ) that is free in preparation for connection;    securing the tubes ( 9 ) of the bundle ( 3 ) in the through holes ( 8 ) of at least one tube plate ( 4 ,  4 ′,  4 ″);    butt welding the wall ( 6 ,  6 ′,  6 ″) of the at least one water chamber ( 5 ) to the free end ( 10   a ) of the connection ring ( 10 ,  10 ′,  10 ″) of the at least one tube plate ( 4 ,  4 ′,  4 ″) having the tubes ( 9 ) of the bundle ( 3 ) secured thereto; and    relieving stress in the weld connecting the wall ( 6 ,  6 ′,  6 ″) of the at least one water chamber ( 5 ) to the connection ring ( 10 ) of the corresponding tube plate ( 4 ,  4 ′,  4 ″) by heating the welded zone.