Patent Application
20110146598
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.
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
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.
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.
Referring now to the Figures, which illustrate exemplary embodiments, and wherein like elements are numbered alike:
Referring now to
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
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
Referring now to
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
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.
