Watertube, Header and Watertube Assembly, Boiler having the Assembly, and Method of Assembling Same

Abstract

A boiler is provided that has an elongate base header, an elongate dome header, and a plurality of separate watertubes each having an intermediate section and opposite end sections. An upper one of the end sections of each watertube is connected to the dome header and a lower one of the end sections of each watertube is connected to the base header such that the intermediate section extends through a combustion chamber of the boiler. The intermediate section of each watertube has a substantially constant outer diameter along its full length and is closely spaced to adjacent watertubes within the combustion chamber. At least one of the end sections of each watertube has a transition that reduces the diameter of the watertube as it extends from the intermediate section to an outwardly-extending circumferential flange. This arrangement permits close spacing of the connection sites of the watertubes to the header and permits the connection sites to be provided in a linear array. The structure of a watertube, an assembly of a watertube and header, and a method of assembling a boiler are also disclosed.

1 . A boiler, comprising:
 an elongate base header located adjacent a base of the boiler and an elongate dome header located at the top of the boiler; and   a plurality of watertubes each having an intermediate section and opposite end sections, an upper one of said end sections of each of said watertubes connecting to said dome header and a lower one of said end sections of each of said watertubes connecting to said base header such that said intermediate section extends through a combustion chamber of the boiler;   said intermediate section of each of said watertubes having a substantially constant outer diameter along its full length and being closely spaced to adjacent watertubes within said combustion chamber; and   at least one of said end sections of each of said watertubes having a transition that reduces the diameter of the watertube as it extends from the intermediate section.   
     
     
         2 . A boiler according to  claim 1 , wherein said at least one of said end sections has an outwardly-extending circumferential flange located on an opposite side of said transition from said intermediate section such that said flange extends from a part of said end section of reduced diameter. 
     
     
         3 . A boiler according to  claim 2 , wherein said outwardly-extending circumferential flange has a peripheral outer edge of a predetermined diameter that closes matches or is not significantly greater than said outer diameter of said intermediate section. 
     
     
         4 . A boiler according at  claim 3 , wherein said base header and said dome header have a series of sockets for receiving a portion of said end sections of said watertubes, and wherein said series of sockets of at least one of said base header and said dome header are provided solely as a closely-spaced, non-staggered, linear array of sockets. 
     
     
         5 . A boiler according to  claim 4 , wherein a fastener is secured to said at least one of said base header and dome header in between each of said sockets and extends over and engages top surfaces of said outwardly-extending circumferential flanges of an adjacent pair of said watertubes to prevent withdraw of said watertubes from said sockets. 
     
     
         6 . A boiler according to  claim 5 , wherein each of said watertubes are identical and made of a single length of tube with integral end sections having said transition and outwardly-extending circumferential flange formed by a forming operation. 
     
     
         7 . A boiler according to  claim 5 , wherein each of said watertubes are identical and include an end fitting welded thereto for providing said outwardly-extending circumferential flange. 
     
     
         8 . A boiler according to  claim 5 , wherein each of said end sections of each of said watertubes includes said transition and said outwardly-extending circumferential flange. 
     
     
         9 . A boiler according to  claim 8 , wherein each of said dome header and said base header includes said closely-spaced linear array of sockets. 
     
     
         10 . A boiler according to  claim 9 , wherein said intermediate section of each of said watertubes extends in a non-linear, serpentine path through said combustion chamber. 
     
     
         11 . A watertube and header assembly for a boiler or heat exchanger, comprising:
 an elongate, hollow header extending within the boiler or heat exchanger; and   a plurality of separate, closely-spaced, elongate watertubes extending from said header;   each of said watertubes having an intermediate section and at least one end section, said end section of each of said watertubes being connected to said header;   said intermediate section of each of said watertubes having a substantially constant outer diameter along its full length and being closely spaced to adjacent watertubes; and   said end section of each of said watertubes having a transition that reduces the diameter of the watertube as it extends from said intermediate section to an outwardly-extending circumferential flange located on an opposite side of said transition relative to said intermediate section such that said flange extends from a reduced-diameter part of said end section.   
     
     
         12 . A watertube and header assembly according to  claim 11 , wherein said outwardly-extending circumferential flange has a peripheral outer edge of a predetermined diameter that closes matches said outer diameter of said intermediate section. 
     
     
         13 . A watertube and boiler assembly according at  claim 12 , wherein said header has a series of sockets for receiving free end tip portions of said end sections of said watertubes, said series of sockets being provided as a closely-spaced linear array of sockets along a length of said header. 
     
     
         14 . A watertube and boiler according to  claim 13 , wherein a fastener is secured to said header in between each of said sockets and extends over and engages upper surfaces of said outwardly-extending circumferential flanges of an adjacent pair of said watertubes to prevent withdraw of said free end tip portions of said watertubes from said sockets. 
     
     
         15 . A watertube for a boiler or heat exchanger, comprising an elongate watertube having an intermediate section and opposite end sections, said intermediate section having a substantially constant outer diameter along its full length and having bends providing said intermediate section with a serpentine-like shape, each of said opposite end sections having a transition that reduces the diameter of the watertube as it extends from said intermediate section to an outwardly-extending circumferential flange located on an opposite side of said transition relative to said intermediate section such that said flange extends from a part of said end section of reduced diameter, said outward-extending circumferential flanges having a peripheral outer edge of a predetermined diameter that closes matches said outer diameter of said intermediate section. 
     
     
         16 . A watertube according to  claim 15 , wherein said transitions and outwardly-extending circumferential flanges are integral, formed parts of said watertube. 
     
     
         17 . A watertube according to  claim 15 , wherein said outwardly-extending circumferential flanges are provided by separately-manufactured end fittings that are welded to said end sections. 
     
     
         18 . A method of assembling a boiler, comprising:
 mounting an elongate hollow base header below a combustion chamber of the boiler and mounting an elongate hollow dome header above the combustion chamber of the boiler such that said base header and dome header extend parallel with one another; and   providing only a linear, non-staggered array of sockets in each of the base and dome headers;   providing a plurality of watertubes such that each of the watertubes includes an intermediate section of substantially constant outer diameter and opposite end sections, each of the end sections having a transition that reduces the outer diameter of the watertube as it extends from the intermediate section to an outward-extending circumferential flange located on an opposite side of the transition relative to the intermediate section such that the flange extends from a part of the end section of reduced diameter, each outward-extending circumferential flange has a peripheral outer edge of a predetermined diameter that closes matches the outer diameter of said intermediate section; and   connecting the plurality of watertubes to the linear array of sockets of the base and dome headers such that the intermediate sections of the watertubes extends through the combustion chamber of the boiler closely-spaced to intermediate sections of adjacent watertubes.   
     
     
         19 . A method according to  claim 18 , wherein fasteners are secured to the base and dome headers to secure each adjacent pair of watertubes to the base and dome headers, each fastener extending from one of the base and dome headers between an adjacent pair of sockets and extending over and engaging top surfaces of the outwardly-extending circumferential flanges of the adjacent pair of watertubes. 
     
     
         20 . A method according to  claim 19 , wherein each of the watertubes is identical and each of said outward-extending circumferential flanges is provided by a separately-manufactured end fitting or an integral formed section of the watertube.