US20100313828A1

US20100313828A1 - Watertube, Header and Watertube Assembly, Boiler having the Assembly, and Method of Assembling Same

Info

Publication number: US20100313828A1
Application number: US12/483,593
Authority: US
Inventors: Thomas Wayne MOORE
Original assignee: Burnham Services Inc
Current assignee: Burnham Services Inc
Priority date: 2009-06-12
Filing date: 2009-06-12
Publication date: 2010-12-16

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.

Description

BACKGROUND OF THE INVENTION

The present invention relates to a boiler and/or heat exchanger used in a domestic and/or commercial heating and/or hot water system, and more specifically, the present invention relates to a watertube, a header and watertube assembly, a boiler having the header and watertube assembly, and a method of assembling the boiler.
A watertube boiler has a series of bent tubes, hereafter referred to as watertubes, extending from a base header, such as a pipe, manifold, or like casting, to an upper or dome header, such as a pipe, manifold, or like casting, through a combustion chamber of the boiler. For examples of watertube boilers, see U.S. Pat. No. 4,993,368 issued to Jones et al. and U.S. Pat. No. 1,824,256 issued to Bryan. A return pipe of the heating system is connected to the base header for returning cool water or like fluid to the boiler. The cool water or like fluid flows upward into the plurality of closely-spaced watertubes where the water or like fluid is heated as it passes through and/or adjacent the combustion chamber. A delivery pipe connects to the top of the dome header which receives the heater water, like fluid, or steam from the watertubes and delivers the steam and/or heated water or fluid to the system via the delivery pipe.
Typically, such a boiler will have a front and a rear with the headers extending horizontally in a front-to-rear direction at the top and bottom of the boiler. A plurality of closely-spaced watertubes typically having undulating intermediate sections extends through the combustion chamber. The upper end sections of the watertubes connect to the dome header, and lower end sections connect to the base header. Each watertube essentially extends through the boiler within a vertically-disposed plane that is parallel with the front and rear of the boiler and that is parallel to all other planes defined by the other watertubes.
Each manifold, dome, header, or like casting is typically provided in the form of an elongate hollow pipe or the like that has a relatively large diameter as compared to the diameter of the watertubes. Conventionally, the end sections of the watertubes connect to the manifolds, headers, domes, or castings via separately manufactured nipple fasteners or end fittings. The separately-manufactured fitting typically provides the end of the watertube with an outwardly-extending circumferential ring, or flange, and a tapered end tip. The tapered tip is inserted into a corresponding tapered hole, port or socket in the water dome, manifold, header or like casting, and a clip, clasp or like fastener is typically applied over the circumferential rings, or flanges, to mechanically secure the inserted tube end to the water dome, manifold, header or like casting. As best illustrated in FIG. 5 of U.S. Pat. No. 1,824,256, the holes in the headers are formed in a staggered, offset pattern required to permit close spacing of adjacent watertubes despite the existence of the outwardly-extending, circumferential flanges or rings of the watertubes.
The conventional watertube is made of steel, has constant inner and outer diameters from end-to-end, and weights at least about fifty pounds. The intermediate sections extend in various bent, serpentine, or other shapes as they extend within the combustion chamber of the boiler. The separately-manufactured fittings are typically welded to each free end to enable the ends of the watertubes to be connected in a fluid-tight and secure manner to water domes, manifolds, headers, and like castings as discussed above.

BRIEF SUMMARY OF THE INVENTION

According to a first aspect of the present invention, a boiler is provided that has an elongate base header located adjacent a base of the boiler, an elongate dome header located at the top of the boiler, 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 and transitions to a reduced-diameter free end tip of the end section.
According to some embodiments, the above referenced end section of the watertube has an outwardly-extending circumferential flange. The flange is located on an opposite side of the transition from the intermediate section of the watertube such that the flange extends from a reduced-diameter part of the end section adjacent the free end tip. The outwardly-extending circumferential flange has a peripheral outer edge of a predetermined diameter that closes matches or is not significantly greater than the constant outer diameter of the intermediate section. Further, the base header and the dome header have a series of sockets for receiving the tip portion of the end sections of the watertubes, and preferably the series of sockets of at least one of the base header and dome header is provided as a closely-spaced linear (non-staggered) array of sockets.
According to another aspect of the present invention, a watertube and header assembly for a boiler or heat exchanger is provided and includes an elongate, hollow header extending within the boiler or heat exchanger and a plurality of separate, closely-spaced, elongate watertubes extending from the header. Each of the watertubes has an intermediate section and at least one end section. The end section is the part of the watertube that connects to the header, and the intermediate section has a substantially constant outer diameter along its full length and is closely spaced to adjacent intermediate sections of like watertubes. The end section of each watertube has a transition that reduces the 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. Thus, the flange extends from a part of the end section having a reduced diameter. Preferably, the outward-extending circumferential flange has a peripheral outer edge of a predetermined diameter that closes matches the outer diameter of said intermediate section, and the header has a series of sockets for receiving the free end tip portions of the end sections of the watertubes. The series of sockets are provided as a closely-spaced linear array of sockets along a length of the header.
According to yet another aspect of the present invention, a watertube for a boiler or heat exchanger is provided and comprises an elongate tube having an intermediate section and opposite end sections. The intermediate section has a substantially constant outer diameter along its full length and bends providing the intermediate section with a serpentine-like shape. Each of the end sections has a transition that reduces the diameter of the watertube as it extends from the intermediate section to an outwardly-extending circumferential flange located on an opposite side of the transition relative to the intermediate section. Thus, the flange extends from a reduced-diameter part of the end section. The outwardly-extending circumferential flange has a peripheral outer edge of a predetermined diameter that closes matches the outer diameter of the intermediate section.
According to a final aspect of the present invention, a method of assembling a boiler is provided. The method includes the steps of mounting an elongate hollow base header below a combustion chamber of the boiler, mounting an elongate hollow dome header above the combustion chamber of the boiler, and providing only a linear array of sockets in each of the base and dome headers. A plurality of watertubes is provided such that each of the watertubes includes an intermediate section of substantially constant outer diameter and opposite end sections. Each of the end sections has a transition that reduces the outer diameter of the watertube as it extends from the intermediate section to an outwardly-extending circumferential flange located on an opposite side of the transition relative to the intermediate section. Each outward-extending circumferential flange has a peripheral outer edge of a predetermined diameter that closes matches the outer diameter of the intermediate section. The method further includes the step of 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 extend through the combustion chamber of the boiler closely-spaced to intermediate sections of adjacent watertubes.

BRIEF DESCRIPTION OF THE DRAWINGS

The features and advantages of the present invention should become apparent from the following description when taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of an end section of a known watertube;

FIG. 2 is a cross-sectional view of FIG. 1.

FIG. 3 is a view illustrating the staggered connection pattern of prior art watertubes to a header;

FIG. 4 is a front view of a watertube according to the present invention;

FIG. 5 is a side view of the watertube of FIG. 4;

FIG. 6 is an enlarged view of an end section of the watertube of FIG. 4;

FIG. 7 is a perspective view of a watertube and header assembly according to the present invention;

FIG. 8 is a cross-sectional view taken along line 8-8 of FIG. 7;

FIG. 9 is a cross-sectional view of the watertube of FIG. 4 assembled to a header according to the present invention; and

FIG. 10 is front elevation view of an assembly of the watertube of FIG. 4 connected to upper and lower headers.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to tubes or pipes used in boilers, heat exchangers, and like apparatus. For example, the present invention relates to so-called watertubes and the connection of the watertubes to manifolds, headers or the like of domestic and commercial boilers.
For purposes of comparison, a known configuration of an end section of a watertube is provided in FIGS. 1 and 2. More specifically, FIGS. 1 and 2 illustrate the configuration of the end 10 of the watertube 12 according to the invention disclosed in co-pending U.S. patent application Ser. No. 11/380,456 filed on Apr. 27, 2006 and published as U.S. Patent Application Publication No. 2007/0251684 A1 on Nov. 1, 2007.
The watertube 12 has a constant outer diameter “A” from a circumferential flange 14 at end 10 of the watertube 12 to a like circumferential flange at the opposite end (not shown) of the watertube 12. The tip 16 of the watertube 12 extending forward of the circumferential flange 14 provides a slight inward taper for enabling ready insertion within a hole of a manifold, header or the like.
For purposes merely of example, a typical watertube is made of steel, weighs about fifty pounds or more, has a constant outer diameter of about 1.5 inch, and has a constant inner diameter of about 1.25 inch thereby providing a tube wall thickness of about 0.25 inch. Of course, other dimensions can be utilized. The watertubes can extend in a serpentine or other shaped path between opposite ends through a combustion chamber of a boiler.
The watertube 12 of FIGS. 1 and 2 has an end 10 in which the circumferential flange 14 and inward taper of the tip 14 is formed via a tube forming operation. However, the use of separately-manufactured end fittings (not shown) that are applied to the ends of a watertube and that provide circumferential flanges and tapered tips is also known. For example, the separately-manufactured end fitting can be welded with a fillet weld to the free end of a watertube. In both of the above described watertube configurations (one in which the end of the watertube is formed into a desired configuration and one in which a separate end fitting is welded to the end of the watertube), the watertube has a constant outer diameter “A” between circumferential flanges located at opposite ends of the watertube.
The circumferential flanges 14 extend outwardly well beyond the outer diameter “A” of the watertube 12. Thus, when securing the watertube 12 to a header, a staggered offset pattern of connection sites is required to provide the desired close spacing of adjacent watertubes. The staggered connection pattern accommodates the circumferential flanges while permitting the intermediate sections of the watertubes to extend through a combustion chamber in a closely-spaced arrangement.
By way of example, FIG. 3 illustrates a conventional staggered pattern of watertubes 12 connected to a header 20. As shown in FIG. 3, the circumferential flanges 14 extend radially outward of the outer diameter “A” of the watertubes 12. Thus, the existence of the flanges 14 requires sufficient spacing between adjacent watertubes. However, since a given number of closely-spaced watertubes are required along a given length of the header, the connections of the watertubes to the header must be staggered or offset. As shown in FIG. 3, a spacing “B” is required between adjacent watertubes 12 to accommodate the circumferential flanges 14, and the staggering of the connection sites permits the walls of the intermediate sections of the watertubes 12 to have a spacing “C” as viewed from the direction represented by arrow 26. A disadvantage of the staggered pattern of connection sites is that it requires the header 20 to be of an increased size or diameter than otherwise would be desired or necessary.
With the above discussion in mind, a watertube 30 according to the present invention is illustrated in FIGS. 4-6. The watertube 30 has an undulating intermediate section 32 that extends through the combustion chamber of a boiler. The outer diameter “D” of the watertube 30 is substantially constant along the full length of the intermediate section 32 and can be equal to the outer diameter “A” of watertube 12. End sections 34 and 36 extend from the opposite ends of the intermediate section 32. Somewhat similar to the circumferential flange 14 and tip 16 of the watertube 12, the watertube 30 of the present invention can also have outwardly-extending circumferential flanges 38 and free end tips 40 which may or may not be tapered.
However, unlike the watertubes 12, the watertube 30 of the present invention is not of a constant diameter between opposite circumferential flanges 38. Rather, each end section, 34 and 36, includes a transition 42 located between the intermediate section 32 and each circumferential flange 38. See FIG. 6. The transition 42 reduces the inner and outer diameters of the watertube 30 as it extends from the intermediate section 32 toward the circumferential flange 38. For example, the outer diameter “E” of the transition 42 adjacent the circumferential flange 38 is less than that of the outer diameter “D” of the transition 42 adjacent the intermediate section 32. The transition 42 can be provide by tapered walls as shown in FIG. 6 or by walls have a stepped configuration.
The circumferential flange 38, as illustrated in FIG. 6, extends from a part of the watertube 30 having the reduced outer diameter of “E”, and its outermost circumferential edge extends to a diameter of “F”. The outer diameter “F” of the circumferential flange 38 closely matches the outer diameter “D” of the intermediate section 32 of the watertube 30. Accordingly, the existence of the outwardly-extending circumferential flanges 38 from the end sections, 34 and 36, provides no limitation with respect to close-spacing of watertubes 30 where they connect to a header. For example, as best illustrated in FIG. 7, the watertubes according to the present invention can be closely-spaced together in a linear pattern where they extend from header 44 despite the presence of the circumferential flanges.
Accordingly, the transition 42 of the watertube 30 adjacent the circumferential flange 38 accommodates the existence of the outwardly-extending circumferential flange 38 thereby eliminating any spacing requirements as a result of the circumferential flange 38. For example, see FIG. 9. Thus, the watertubes 30 can be spaced together as close as desired in any pattern, linear or otherwise. This, in turn, enables the size or diameter of the header 44 to be reduced. For example, the header 20 required by the staggered pattern of FIG. 3 may need to have a diameter of at least about eight inches to accommodate the offset spacing of the connection sites; whereas, for similar-sized watertube diameters, the header 44 in FIGS. 7-10 may require a diameter of only three inches due to the linear connection site pattern. This provides advantages with respect to increasing the velocity of the fluid through the boiler, improving convective heat transfer within the boiler, and reducing costs with respect to making and assembling the boiler.
In the embodiment of the present invention illustrated in FIGS. 4-6 and 9, the end sections 34 and 36 of the watertube 30 are produced as a result of a forming operation applied to the ends of the watertube 30. Thus, the watertube 30 comprises a single piece of tube in which the transition sections 42 and circumferential flanges 38 are formed using appropriate forming dies or the like.
In contrast, FIGS. 7 and 8 illustrate another embodiment of a watertube 50 according to the present invention. These watertubes have separately applied end fittings 52. The end fitting 52 is secured to a free end of the watertube 50, such as by being welded thereto (the existence of the fillet weld is not shown for purposes of ease of illustration). An intermediate section 54 of the watertube 50 can have a constant outer diameter between opposite end sections. However, at end sections of the watertubes 50, where the watertubes 50 are required to connect to manifolds, headers, domes or like castings 44, the watertubes 50 are provided with a transition 56 that tapers inward from the intermediate section 54 to a reduced outer diameter section 58. The end fitting 52 is secured to the reduced outer diameter section 58, and the circumferential flange 60 provided by the end fitting 52 extends outward from the reduced diameter section 58. As discussed above, the transition 56 enables the outer diameter of the circumferential flange 60 to substantially and closely match the outer diameter of the intermediate section 54. Thus, the existence of the circumferential flange 60 does not restrict close spacing of adjacent watertubes 50 regardless of the connection pattern (staggered, linear, or otherwise).
The transitions 42 and 56 of the watertubes 30 and 50 also accommodate the installation of clips, clasps, fasteners or the like 62 that mechanically secure the watertubes 30 and 50 to the headers, manifolds, domes, castings or the like 44. For instance, as illustrated in FIGS. 7-9, threaded shafts 64 extend from the header 44 and permit the placement of washers 66 or the like that overlaps with and engages the upper surfaces of circumferential flanges 38 and 60 of adjacent watertubes 30 and 50 and secures the watertubes 30 and 50 to the header 44 via placement of a securement nut 68 or the like. Of course, other fastening mechanisms can be used. Thus, the transitions 42 and 56 not only permit close spacing of watertubes 30 and 50 on the header 44, but also accommodate the placement of fasteners 62 that prevent undesired withdrawal of the watertubes 30 and 50 from the header 44 during assembly or use.
FIG. 10 provides a simplified example of a boiler 70 having watertubes 30 and headers 44. The headers 44 are illustrated as being in the form of pipes of a given diameter. This diameter can be reduced as desired due to the use of a linear connection pattern of the watertubes to the header; for instance, see the linear pattern of FIG. 7. A combustion chamber 72 is located at an elevation between the headers 44, and the watertubes 30 extend from the base header through the combustion chamber 72 to the upper header.
The watertubes of the present invention can be efficiently and readily driven into water domes, manifolds, headers and the like despite their close spacing. In addition, the end forming process used to form the ends of watertube 30 enables better control over tube tolerances with respect to diameters, tapers and the like to ensure the formation of fluid-tight connections.
Various changes can be made to the above referenced watertubes, assemblies, and methods of assembly. For example, the circumferential flanges can be continuous or discontinuous, and can be formed with a surface having a series of slots, recesses, or the like adapted to engage the head of a driving tool. Alternatively, the watertubes can be provided with ends not having circumferential flanges. Also, one or both ends of the watertube can have a formed end, and the intermediate section of the watertube can extend in a bent or linear path. The taper of the transition can be a gradually continuous uniform taper or a non-uniform varying taper.
Accordingly, the present invention provides a watertube configuration and watertube-to-header assembly that permits close-spacing of adjacent watertubes without the use of staggered connection patterns. Further, the headers or manifolds to which the watertubes of the present invention connect can be provided of smaller diameters or sizes yet still enable a desired number of watertubes to be connected thereto in a closely-spaced manner. The benefits that will be achieved with such an assembly include improving the velocity of the water, steam, or like fluid through the watertube and header assembly, improving convective heat transfer to the water or like fluid, and reducing manufacturing and assembly costs.
While preferred watertubes, assemblies, and methods have been described in detail, various modifications, alterations, and changes may be made to the present invention without departing from the spirit and scope of the present invention as defined in the appended claims.

Claims

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.