CUFF FOR BOILER TUBE ASSEMBLY AND METHOD OF MANUFACTURE

Abstract

A system for retaining boiler tubes in an array includes a bracket having a contoured surface defining at least one channel, the channel being semi-cylindrical and defined by an elongated cross section having a rounded portion and two elongated legs extending therefrom to define a substantially U-shaped cross section, and a planar section located at a terminus of each leg. The system also comprises a plate connectable to at least one planar section of the bracket. A method of manufacturing a cuff for a boiler tube assembly includes bending a bracket having at least one channel therein, the channel being configured to receive a boiler tube of the boiler tube assembly; and machining a plate, the plate being configured and sized to be positioned over the channel.

Description

TECHNICAL FIELD

The disclosure herein is generally directed to systems for retaining boiler tubes in place during boiler operation. More particularly, the disclosure is directed to a cuff for retaining and maintaining boiler tubes in place during high temperature and high pressure operation of a boiler. The present disclosure is further directed to a method of manufacturing the cuff.

BACKGROUND

A boiler is typically a closed pressure vessel defined by one or more walls and containing a liquid that can be heated under controlled conditions. As the liquid is heated to a certain temperature, the liquid vaporizes causing an increase in pressure within the boiler. This high-pressure vaporized liquid can then be used to provide work, or it can be used as a source of heat.

Typical boilers may include a hundred or more boiler tubes arranged in parallel in a single array. Because these boiler tubes are long and relatively thin-walled, they are subjected to significant heat stress, giving them the tendency to warp and shift out of parallel alignment thereby reducing the uniformity and efficiency of heat transfer to the liquid in the tubes.

The industry standard for keeping the boiler tubes in alignment is a boiler tube cuff, which comprises an elongated set of mating elements that resemble handcuffs. This cuff is defined by semi-circular portions that are radially mated over a set of boiler tubes. One exemplary embodiment of such a cuff is shown generally in FIGS. 1 and 2 and is designated by the reference number 10. As can be seen, the cuff 10 comprises a first portion 12 that is attached to a mating second portion 14 after both portions are placed such that the semi-circular portions 16 accommodate the outer surfaces of the boiler tubes. After being placed over a set of boiler tubes in an array, the first portion 12 and the second portion 14 are secured to one another using interlocking devices 18 such as weldable posts or threaded bolts. In instances in which the boiler tubes over which the portions of the cuff 10 are warped and misaligned, the boiler tubes are often pre-clamped in parallel before the cuff can be mated over them.

The mating handcuff-like devices (such as cuff 10) are typically cast, which means that the tolerances between mating portions are generally fairly close such that contacting portions of each can suitably coincide. Casting the first portion 12 and the second portion 14 to have such close tolerances generally adds substantial costs to the processes of manufacturing the cuff 10. Furthermore, the orientation of the mating portions of cuff 10 typically hinders the fastening of such portions to each other, which may lead to deficiencies in the welds used to secure the portions together.

SUMMARY

According to one aspect described herein, there is provided a system for retaining boiler tubes in an array. This system comprises a bracket having a contoured surface defining at least one channel, the channel being semi-cylindrical and defined by an elongated cross section having a rounded portion and two elongated legs extending therefrom to define a substantially U-shaped cross section, and a planar section located at a terminus of each leg. The system also comprises a plate connectable to at least one planar section of the bracket. The connection of the plate to the at least one planar section of the bracket closes the two legs of the U-shaped cross section such that a boiler tube can be retained in the channel.

According to another aspect, there is provided a cuff for boiler tubes. This cuff comprises a bracket having a contoured surface that defines at least one channel having open ends and an open top, the channel being configured to receive a boiler tube therein. The cuff also comprises a plate located on the bracket to close the open top of the at least one channel, thereby allowing the boiler tube to extend from at least one of the open ends of the channel.

According to another aspect, there is provided a method of manufacturing a cuff for a boiler tube assembly comprising a bracket fabricated from flat stock having at least one channel therein, the at least one channel being defined by open ends and an open top, the channel being configured to receive a boiler tube of the boiler tube assembly; and machining a plate, the plate being configured and sized to be positioned over the open top of the channel. In using the cuff, the plate is attachable to the bracket upon receiving the boiler tube in the channel.

BRIEF DESCRIPTION OF THE DRAWINGS

Referring now to the Figures, which illustrate exemplary embodiments, and wherein like elements are numbered alike:

FIG. 1 is a perspective view of a typical boiler tube cuff.

FIG. 2 is a perspective exploded view of the boiler tube cuff of FIG. 1.

FIG. 3 is a perspective exploded view of a U-cuff.

FIG. 4 is a perspective view of a portion of a U-cuff in which a plate is attached to a bracket using bolts and nuts.

FIG. 5 is a front view of the U-cuff having three boiler tubes inserted therethrough.

DETAILED DESCRIPTION

Referring now to FIG. 3, a system for retaining and maintaining boiler tubes in an array in a boiler during operation of the boiler comprises a plate-fabricated U-cuff, which is designated generally by the reference number 20 and is hereinafter referred to as “U-cuff 20.” The U-cuff 20 comprises a bracket 22 having a contoured surface that defines U-shaped channels and a plate 24 to which the bracket can be attached such that boiler tubes are accommodated in the channels of the bracket and retained therein by the plate.

The bracket 22 is an elongated member defining a plurality of channels 30 along a length L thereof. Each of the channels 30 is substantially U-shaped in cross section and has an open top and open ends. The U-shape of the cross section is configured and sized to accommodate a portion of an outer surface of a tube extending perpendicular to the direction in which the bracket 22 extends when the U-cuff 20 is located on the array of the boiler tubes (or at least one boiler tube). In particular, each channel 30 is a structure of a semi-cylindrical configuration having an elongated rounded portion and elongated legs such that the U-shape of the cross section of the channel is defined thereby, each channel being connected to an adjacent channel via a planar section 34 such that the bracket 22 is a series of alternating channels and planar sections. Although the U-cuff 20 is shown in FIG. 3 as including three channels 30, the U-cuff is not so limited as the bracket 22 can comprise any desired number of alternatingly positioned channels and planar sections.

The plate 24 of the U-cuff 20 comprises a planar member of substantially the length L (or slightly longer). A width W of the plate 24 substantially corresponds to a width of the bracket 22. The plate 24 comprises a plurality of weldment slots 38 located therein such that upon assembling the plate and the bracket 22, the plate can be welded or brazed to the bracket at the weldment slots. The connection of the plate 24 to the bracket 22 is not limited to being effected using weldment slots 38 at which welds can be made, however, as either the bracket or the plate may include tangs or posts that extend through openings in the other of the plate or the bracket to facilitate the joining of the bracket and the plate by welding.

The joining of the bracket 22 and the plate 24 is also not limited to welding or brazing, as other methods of attaching the bracket to the plate can be employed. Referring now to FIG. 4, the bracket 22 can be attached to the plate 24 via the use of threaded bolts 138. The threaded bolts 138 may be integral with the planar sections 34 on the bracket 22, or they may be inserted through openings in both the planar sections and the bracket. In either embodiment, nuts 140 are located on the threaded bolts 138 and tightened to fasten the plate to the bracket. Other methods of securing the plate 24 to the bracket 22 include, but are not limited to, pins, rivets, and any other suitable device inserted through the planar sections 34 and the plate.

Referring now to FIG. 5, the U-cuff 20 is shown with a boiler tube 40 located in a channel 30. The plate 24 is also shown being mounted on the bracket 22, thereby holding the boiler tube 40 in the U-cuff 20. A portion of an inner surface of each channel 30 of the bracket 22 is configured to correspond to a portion of an outer surface of each boiler tube 40 located therein. A depth D of each channel 30 substantially corresponds to the diameter of the boiler tube 40. In doing so, a boiler tube 40 is retained in the U-cuff 20 by being held by the inner surface of the rounded portion and the inner surfaces of the legs of the channel 30 and the surface of the plate 24 that faces the bracket 22. Tolerances between the outer surface of the boiler tube 40 and the surfaces of the channel 30 and/or the plate 24 can be introduced as desired.

Materials from which the U-cuff 20 may be fabricated include, but are not limited to, alloys of nickel, chromium, and iron and alloys of chromium and nickel. One exemplary Ni—Cr—Fe alloy is Alloy 601, also known as 60Ni-23Cr—Fe. Alloy 601 is especially desirable for the bracket 22 because it is highly resistant to oxidation up to about 1,250 degrees C. and can weather severe conditions such as cyclical heating and cooling in a boiler environment. One exemplary Cr—Ni alloy is Alloy 309 (austenitic stainless steel), which is 23Cr-12Ni. Alloy 309 is especially desirable for the plate 24 as it is highly weldable and exhibits high resistance to aqueous corrosion.

Although the bracket 22 as shown in FIG. 3 has three channels 30 and the bracket 22 as shown in FIG. 5 has seven channels 30, the U-cuff 20 is not limited in either of these regards as any suitable number of channels may be incorporated into the bracket to accommodate any desired number of boiler tubes 40.

The U-cuff 20 can be produced at far less cost than cast cuff alignment devices and is therefore less expensive per boiler tube aligned. More specifically, by manufacturing the U-cuff 20 by a method of bending the bracket 22 and machining the plate 24 from flat stock, the cost of producing the U-cuff 20 is substantially reduced as compared to cuffs comprising two or more mating portions that are cast. Furthermore, because the plate 24 is manufactured from a material that is highly weldable as compared to cast materials, the welding costs associated with installing a boiler tube assembly using the U-cuff 20 are further reduced. By reducing the overall cost of the product, bids for the installation of boiler tube assemblies in boilers can become more competitive in the boiler industry.

Although this invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those of skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed in the above description, but that the invention will include all embodiments falling within the scope of the appended claims.

Claims

1. A system for retaining boiler tubes in an array, the system comprising:

a bracket comprising, a contoured surface defining at least one channel, the channel being semi-cylindrical and defined by an elongated rounded portion and two elongated legs extending therefrom to define a substantially U-shaped cross section, and a planar section located at a terminus of each leg; and

a plate connectable to at least one planar section of the bracket;

wherein the connection of the plate to the at least one planar section of the bracket closes the two legs of the U-shaped cross section; and

wherein a boiler tube can be retained in the channel.

2. The system of claim 1, wherein the plate includes at least one weldment slot located therein, the at least one weldment slot being configured to correspond with at least one planar section of the bracket.

3. The system of claim 2, wherein the plate is welded to the at least one planar section of the bracket at the at least one weldment slot.

4. The system of claim 1, wherein the plate is connectable to the at least one planar section of the bracket using a bolt and nut.

5. The system of claim 1, wherein the bracket is fabricated from a Ni—Cr—Fe alloy.

6. The system of claim 5, wherein the Ni—Cr—Fe alloy is Alloy 601.

7. The system of claim 1, wherein the plate is fabricated from a stainless steel alloy.

8. The system of claim 7, wherein the stainless steel alloy is Alloy 309.

9. A cuff for boiler tubes, the cuff comprising:

a bracket having a contoured surface that defines at least one channel having open ends and an open top, the channel being configured to receive a boiler tube therein; and

a plate located on the bracket to close the open top of the at least one channel, thereby allowing the boiler tube to extend from at least one of the open ends of the channel.

10. The cuff of claim 9, further comprising at least one opening on the plate at which the bracket can be attached to the plate.

11. The cuff of claim 10, wherein the opening on the plate is a weldment slot at which a weld can be made to attach the bracket to the plate.

12. The cuff of claim 9, wherein the bracket is a Ni—Cr—Fe alloy.

13. The cuff of claim 9, wherein the plate is a stainless steel alloy.

14. A method of manufacturing a cuff for a boiler tube assembly, the method comprising the steps of:

bending a bracket having at least one channel therein, the at least one channel being defined by open ends and an open top, the channel being configured to receive a boiler tube of the boiler tube assembly therein; and

machining a plate, the plate being configured and sized to be positioned over the open top of the channel;

wherein the plate is attachable to the bracket upon receiving the boiler tube in the channel.

15. The method of claim 14, further comprising welding the bracket to the plate.

16. The method of claim 14, wherein the bracket is bent from a Ni—Cr—Fe alloy flat stock.

17. The method of claim 14, wherein the plate is machined from a stainless steel alloy flat stock.