Abstract:
A method and apparatus particularly suited to the manufacture and assembly of cage-like, substantially cylindrical structures made of long, slender tubular components which, by themselves, are not self-supporting, employs an exo-skeleton structure to assemble cage-like, tubular structures in pie-shaped, longitudinal segments while in a horizontal or vertical position utilizing longitudinal or circumferential attachments. The apparatus comprises at least two segments which permit construction of subassemblies of the cage-like, tubular structure and their transportation, if necessary, to a remote site where they may be finally assembled.

Description:
FIELD AND BACKGROUND OF THE INVENTION 
     The present invention relates generally to the manufacture of heat transfer apparatus and, in particular, to methods and apparatus for assembling vessels or vessel internals such as substantially cylindrical, cage-like structures made of tubular components, in pie-shaped, longitudinal segments while in a horizontal or vertical position utilizing longitudinal or circumferential attachments. 
     Certain types of heat transfer apparatus comprise tubular, fluid conveying structures arranged in specified geometries. During operation, these tubular structures convey a cooling fluid, such as water, steam or mixtures thereof through an interior portion of the tubes, while hot gases are conveyed around outside surfaces of the tubes. Heat from the hot gases is conveyed through the tube walls into the cooling fluid which is conveyed to other locations or devices, such as turbines or other devices, for use. The properties of the hot gases, which include but are not limited to their temperature, chemical constituents, corrosion potential, emissivity, and their slagging and/or fouling potential, influence the geometries, spacing, arrangement, materials, and sizing of the tubular structures to a great degree. 
     The construction of radiant synthesis gas (syngas) cooler apparatus used to contain and cool the synthesis gas produced by a coal gasification process such as an Integrated Gasification Combined Cycle (IGCC) power plant is a classic example of one type of heat transfer apparatus where the properties of the hot gases influence the tubular, fluid conveying structures provided within the syngas cooler. These syngas coolers are typically long, substantially cylindrical pressure vessels which contain within an external shell of the vessel a specific arrangement of tubular, fluid conveying structures which are used to extract heat from the hot synthesis gas and when erected may be on the order of 100 feet tall or more, and have a diameter on the order of 20 feet or more. 
     The tubular, fluid conveying structures within such syngas coolers typically comprise a substantially cylindrical, cage-like structure within which may be located additional tubular structures known as division or platen walls. The cage-like structure may be substantially cylindrical along a central portion thereof, and provided with inlet and outlet structures which may be frustoconical or tapered to admit and exhaust, respectively, the hot synthesis gases into the cage-like structure during operation. Headers and/or manifolds are generally provided at both the inlet and outlet structures to provide common locations for the delivery and removal of the fluid conveyed through the cage-like structure. 
     While the headers and manifolds may have substantial diameters and wall thicknesses, the majority of the cage-like, tubular structure is comprised of long, slender tubes on the order of 2″ outside diameter (O.D.). These tubes are generally straight, and only bent as necessary to accommodate the aforementioned inlet and outlet structures. The substantially cylindrical walls of the cage-like structure are formed of these tubes and welded to one another by means of a membrane structure as is known to those skilled in the boiler arts. Furthermore, while the division or platen walls which may be provided in an interior portion are generally planar structures comprised of membraned tubes, they may have other shapes, such as an angled or “dog leg” configuration, and they may not be attached to the substantially cylindrical walls or to the inlet and outlet structures and thus the entire cage-like, tubular structure is not a rigid, easily handled structure nor can it be easily manipulated. 
     It is thus clear that development of an efficient technique for manufacturing and transporting heat transfer devices comprising substantially cylindrical, cage-like structures made of long, slender tubular components would be welcomed by industry. 
     SUMMARY OF THE INVENTION 
     One aspect of the present invention is drawn to an apparatus, referred to as a Polygon Tumble Assembler, which employs an exo-skeleton structure to assemble vessels and/or vessel internals in pie-shaped, longitudinal segments while in a horizontal or vertical position utilizing longitudinal or circumferential attachments. The vessel internals may comprise a substantially cylindrical, cage-like structure made of tubular components. The apparatus comprises at least two segments which permit construction of subassemblies of the cage-like structure made of tubular components and their transportation, if necessary, to a remote site where they may be finally assembled. As used herein, pie-shaped embraces any generally triangular- or wedge-shapes, where all sides are substantially straight or where one side may be in the form of an arc or curved, as well as wedge-shapes formed by taking a triangular shape and removing a portion of the narrow end to produce a four-sided shape. 
     Another aspect of the present invention is drawn to a method of manufacturing vessels and or vessel internals in pie-shaped, longitudinal segments while in a horizontal or vertical position utilizing longitudinal or circumferential attachments. The vessel internals may comprise a substantially cylindrical, cage-like structure made of tubular components. The method employs an exo-skeleton structure to permit construction of subassemblies of the cage-like structure made of tubular components and their transportation, if necessary, to a remote site where the vessels may be finally assembled. 
     The exo-skeleton apparatus of the present invention allows for the assembly of a 360 (or more or less) degree cage-like, tubular structure or vessel in pie-shaped, longitudinal segments, in addition to conventional circular segments. It reduces the needed weight capacity requirements of cranes, allowing for the assembly of complex heavy vessels in the shop or in the field. It provides fixturing for accurate placement of vessel internals during assembly. It functions as a shipping rig or transport device for the unit being built. Depending upon the final method of assembly, it may function as an up-ending device for vessel internals or as a conveying structure to permit the cage-like, tubular structure to be slid into an external vessel shell. The exo-skeleton apparatus used in the methods of the present invention are reusable. It allows for an assembly line approach for the construction of many subassemblies and final assemblies to occur simultaneously. 
     The present invention is particularly suited to the manufacture and assembly of cage-like, substantially cylindrical structures made of long, slender tubular components which, by themselves, are not self-supporting. 
     The present invention may be used in the construction of radiant synthesis gas (syngas) cooler apparatus used to contain and cool the synthesis gas produced by a coal gasification process such as an Integrated Gasification Combined Cycle (IGCC) power plant. 
     The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific benefits attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the Figures: 
         FIG. 1  is a perspective view, partly in section, of a cage-like tubular structure to which the principles of the present invention may be applied; 
         FIG. 2  is a sectional view of  FIG. 1  viewed in the direction of arrows  2 - 2  of  FIG. 1 ; 
         FIG. 3  is a perspective view of a first embodiment of an exo-skeleton apparatus subassembly according to the present invention; 
         FIG. 4  is a is a close-up view of the lower left-hand portion of  FIG. 3 ; 
         FIG. 5  is an end view of an individual arch support according to the present invention; 
         FIG. 6  is an end view of an assembled exo-skeleton comprised of four (4) exo-skeleton subassemblies and their associated segments of the cage-like, tubular structure, according to the present invention; 
         FIGS. 7 ,  8  and  9  are schematic representations of how one exo-skeleton subassembly is rolled into position adjacent to another exo-skeleton sub assembly to form a “half” subassembly) and then how the two halves are then rolled together to create a complete exo-skeleton according to the present invention; 
         FIG. 10  is a perspective view, partly in section, of one end of an exo-skeleton subassembly illustrating the assembly of a segment of the cage-like, tube assembly according to the present invention; 
         FIGS. 11 and 12  illustrate keystone bracing which is provided between individual platens to support and locate the platens within the cage-like, tubular structure according to the present invention; 
         FIGS. 13 and 13A  illustrate the horizontal insertion of the cage-like, tubular structure into a vessel using the exo-skeleton according to the present invention; 
         FIG. 14  illustrates the use of the exo-skeleton according to the present invention to upend the entire cage-like, tubular structure contained therein to permit the structure to be lowered into a vessel; 
         FIG. 15  illustrates an apparatus and method for positioning a vessel head adjacent the end of the cage-like, tubular structure once the latter has been completely assembled within the exo-skeleton according to the present invention; 
         FIG. 16  illustrates how a typical, elongated panel of tubes behaves when lifted for placement on an exo-skeleton subassembly according to the present invention; 
         FIGS. 17 and 18  illustrates a panel/header tube end guide tool according to the present invention,  FIG. 18  being a view of  FIG. 17  taken in the direction of arrows  18 - 18 ; and 
         FIG. 19  illustrates the keystone bracing as provided between individual platens to support and locate the platens within the cage-like, tubular structure according to the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings generally, wherein like reference numerals designate the same or functionally similar elements throughout the several drawings, and to  FIG. 1  in particular, there is shown a perspective view, partly in section, of a cage-like tubular structure to which the principles of the present invention may be applied.  FIG. 2  is a sectional view of  FIG. 1  taken in a plane perpendicular to the longitudinal axis of  FIG. 1 . 
     Briefly, the cage-like tubular structure, generally designated  10 , is predominantly a cylindrical structure which, when erected, has its longitudinal axis A oriented vertically. The structure  10  has a substantially cylindrical enclosure wall  12  which is comprised of tubes  14 . In addition, the structure  10  may also be provided with other tubular structures  16  which lie outboard of the enclosure wall  12 . 
     The cage-like tubular structure may also comprise internal tubular structures or platens  18 , each of which may be generally constructed as a planar, “dog leg” or other shape bank of tubes  14  provided adjacent to one another, and which may be provided with inlet and outlet manifolds or headers  20 . The number and arrangement of the platens  18  can vary depending upon the service requirements of the cage-like tubular structure  10 ; they can be arranged radially as shown; they can be fewer or greater in number, and they are not necessarily identical to one another (although symmetrical arrangements are likely to predominate). The tubes  14  forming the enclosure wall  12  and platens  18  may be, for example, 2″ OD tubes of relatively thin wall thickness and narrow spacing. The tubes  14  forming the enclosure wall  12  may be membraned wall construction as described above. The tubes  14  forming the platens  18  may incorporate loose tube construction, membrane wall construction, or tangent tube construction with a full weld between the tubes to form a tangent tube panel. Loose tube constructions, or for portions of the platens where no membrane is provided, may be provided with split ring castings as is known to those skilled in the boiler arts to preserve tube alignment under various operating conditions. There may be a small gap between the tube enclosure wall  12  and the platens  18 , or there may be a weld along a portion, portions, or along the entire length of an edge tube  14  of some or all of the platens  18  to a tube of the enclosure wall  12 . 
     The cage-like tubular structure  10  may be provided with inlet  22  (not shown in  FIG. 1 ) and outlet  24  structures which may be frustoconical or tapered as shown at  24 , and to which the aforementioned manifolds or headers  20 , as well as the other tubular structures  16 , may be attached. While the term substantially cylindrical is used to refer to the fact that the cage-like tubular structure  10  has an enclosure wall  12  which is cylindrical for a majority of its length, save for the inlet and outlet structures  22 ,  24 , it will be appreciated that the term substantially is also employed since the enclosure wall  12  is actually comprised of a plurality of planar sections as will be described later. 
     Referring now to  FIG. 3 , there is illustrated an embodiment of an exo-skeleton apparatus subassembly, generally designated  30 , according to the present invention. In its most basic form, the subassembly  30  comprises a plurality of saddles or arch supports  32  spaced from one another along a length of the subassembly  30 . The arch supports  32  are interconnected and fixed relative to one another by longitudinal members  34 , advantageously structural I-beams or the like. The combination of the arch supports  32  and the interconnecting longitudinal members  34  provide a relatively stiff structural base upon which the cage-like, tubular structure  10  will be assembled, one segment at a time. The number of arch supports  32  may be selected to provide sufficient spaced support for the tubes  14  so that excessive bowing or sagging of the tubes  14  is avoided. 
     Each of the arch supports  32  has a curved, upper portion  36  which will support the tubes  14  making up the enclosure wall  12  of the tubular structure  10 . The curvature of the upper portion  36  closely matches the curvature of the enclosure wall  14 . The upper portion  36  of each arch support  32  is also provided with plurality of pushers  38  which are used to adjust the positions of tubes  14  which are laid thereupon during assembly of the tubular structure  10 . Each of the arch supports  32  also has a lower or base portion  40  which will rest upon the ground or floor during construction of an individual segment of the cage-like, tubular structure  10 , or on the surface of a transportation device such as a flatbed rail car, truck bed, barge or ship. Each of the arch supports  32  may also be provided with a pivot means  42  at one or both ends which permits the exo-skeleton subassembly  30  to be rolled to better position the subassembly  30  as required to facilitate manufacture of the segment of the cage-like, tubular structure  10 . 
     The number of subassemblies  30  is a matter of choice; in the embodiments shown, four (4) such subassemblies  30  are used to create four (4) individual segments of the cage-like, tubular structure  10 , and in this embodiment each of the exo-skeleton subassemblies spans approximately 90 degrees of the circumference of the enclosure wall  12 . Fewer or greater numbers of subassemblies  30  may be employed, however, it is envisioned that at least two (2) such subassemblies  30  would be employed due to the large size of the cage-like, tubular structures  10  which must be assembled and eventually transported to its final destination in the field. For example, if three (3) subassemblies  30  are employed, each would span 120 degrees of the circumference of the enclosure wall  12 . Five (5) such subassemblies  30  results in each such subassembly  30  spanning 72 degrees, and so on. It will thus be seen that by breaking the tubular structure  10  into smaller, more manageable parts or segments, their assembly, manipulation and transportation is facilitated since their size, weight and height is a fraction of that possessed by the final tubular structure  10 . 
     Referring now to  FIG. 4 , which is a close-up view of the lower left-hand portion of  FIG. 3 , additional details of the construction of the individual arch supports  32  may be seen. Each arch support  32  is provided with cut-outs or notches  44  on the lower portion  40  which engage adjustable jacks or supports  60  (not shown in  FIG. 4 ) to hold the subassembly  30  in position when it is rolled about the pivot means  42 . Cut-outs or notches  46  are also provided on the curved upper portion  36  of each arch support  32 , but their purpose is to accept the tubular structures  16  which lie outboard of the enclosure wall  12  of the tubular structure  10 . Each of the pushers  38  is advantageously provided with a bearing plate  48  which will support the tubes  14  laid thereupon. As indicated earlier, the term substantially cylindrical when applied to the cage-like, tubular structure  10  is also employed to clarify that the tubular structure  10  may actually be comprised of a plurality of planar sections. In other words, the enclosure wall  12  is actually a polygon made up of a plurality of “n-packs”  50  of tubes  14  (not shown in  FIG. 4  but shown in  FIG. 5 ); where n is typically 4, but where it can be a larger or smaller number. The larger the number of tubes  14  in a planar section, the fewer the number of planar sections which will have to be welded to one another as they rest upon the bearing plates  48  of the arch supports; however, this increases the degree to which the outer circumference of the enclosure wall  12  departs from a true cylindrical configuration. Thus, in order to increase manufacturing efficiency and reduce manufacturing costs, the enclosure wall  12  will typically be made of 4-packs of tubes assembled and welded together to form the enclosure wall  12 . 
     The bearing plate  48  will thus have a length sufficient to span the number of tubes  14  forming an “n-pack”  50  of tubes  14 . The width of the bearing plate  48  will likely be selected to ensure that the bearing load on an individual bearing plate  48  will not cause deformation or kinking of the tubes  14  as they rest upon the bearing plate  48 . 
       FIG. 5  is an end view of an individual arch support  32  according to the present invention, illustrating an array of n-packs  50  of tubes  14  which have been positioned upon the subassembly  30 . Since this arch support is one of four (4) individual exo-skeleton subassemblies  30 , the curved upper portion  36  spans 90 degrees of the enclosure wall  12 . The individual pushers  38  may comprise simple threaded bolt and nut assemblies or other more complex devices which can be extended towards or away from the tubes  14  to provide for alignment of the tubes  14  in one n-pack  50  with the tubes  14  in an adjacent n-pack  50 . Multiple pushers  38  may be provided for individual n-packs  50  if required. This is especially important when these separate n-packs  50  are to be connected together by the welding of membrane in between the tubes  14  of one n-pack  50  and the tubes  14  of an adjacent n-pack  50 . 
       FIG. 6  is an end view of an assembled exo-skeleton, generally designated  3000 , comprised of four (4) exo-skeleton subassemblies  30  and their associated segments of the cage-like, tubular structure  10  which together make up the tubular structure  10 . Each of the arch supports  30  has ends  52 , each one of which is connected to an adjacent end  52  of another arch support  30  by means of an adjustable turnbuckle type or other type of device  54 . Device  54  may comprise come alongs, or hydraulic, pneumatic, electrical, cable or chain types of devices and the term turnbuckle will be used for the sake of simplicity to refer to such devices and their equivalents. The turnbuckles  54  are used to control the final increments of the positioning of one exo-skeleton subassembly  30  as it is rolled into position adjacent another exo-skeleton sub assembly  30  and those two subassemblies  30  are drawn together to form a “half” subassembly  300 . Additional plating or bracing spanning the joint between separate arch supports  32  may be applied to further stiffen and strengthen the half subassembly  300 . The procedure is repeated for another “half” subassembly  300 , and then the two halves are then rolled together to create the complete exo-skeleton  3000 . A schematic representation of this assembly process is illustrated in  FIGS. 7 ,  8  and  9 .  FIG. 7  illustrates a ¼ cage assembly, completed.  FIG. 8  illustrates two ¼ cages assembled on a floor or transport device.  FIG. 9  illustrates two ½ cages assembled on a floor or transport device. 
       FIG. 10  is a perspective view, partly in section, of one end of an exo-skeleton subassembly  30  illustrating the assembly of a segment of the cage-like, tube assembly  10  according to the present invention. A lower end of the cage-like, tubular structure  10  is illustrated. Once the various n-packs  50  of tubes have been positioned on the subassembly  30  and welded together, the placement and assembly of the platens  18  is begun. The platens  18  are lowered into the subassembly  30  using a crane and the headers  20  are fit into pre-positioned saddles or saddle-like structures  70  attached to a header fixture  72 . A similar procedure is used at the opposite end of the tubular structure  10 . 
     Next, keystone bracing  80 , as illustrated in  FIGS. 11 and 12 , is provided between individual platens  18  at (or near) each of the arch supports  32  which serve to support and locate the platens  18  within the cage-like, tubular structure  10 . One or more removable attachment means  82  are provided on one or both edges of an individual keystone brace  80  to attach the brace  80  to one or both adjacent platens  18 , while adjustable pusher means  84  are provided on one or both edges to engage the adjacent platens  18 . To keep the braces  80  against the enclosure wall  12 , a removable, folding structure  86  is provided and attached to each keystone brace  80 . The folding structure may advantageously be comprised of rectangular tubing with slots, adjustable all thread, hex nut pushers or other means (such as hydraulic, pneumatic, or electrical). Once the exo-skeleton subassemblies  30  have been assembled to a sufficient degree to provide at least 180 degrees of cage-like, tubular structure  10 , and up to the point of completion of the complete exo-skeleton  3000 , the folding structure  86  is provided and adjusted to outwardly force diametrically opposed keystone braces  80  against the enclosure wall  12  to fix them and their associated platens  18  in place until the folding structure  86  can be removed after final assembly and vertical erection of the cage-like, tubular structure  10  has been completed in the field. 
       FIGS. 13 ,  13 A and  14  illustrate two alternate methods by which the complete cage-like, tubular structure  10  contained within the exo-skeleton  3000  may be inserted into a vessel  90 . In  FIGS. 13 and 13A , the tubular structure  10 , to which a vessel head  92  has been attached, is rolled horizontally into the vessel  90 . The upper three arch supports  32  are removed prior to jacking up the cage-like, tubular structure  10  and lower arch support  32  and then lowering the arch support assembly  32  to allow for clearance of the vessel head  92  past the arch support  32 . As the tubular structure  10  is inserted into the vessel  90 , the cage-like, tubular structure  10  becomes supported by the vessel shell inside diameter. Rolls  94  and associated track or rails are employed for this purpose. The rolls may be provided on the cage-like, tubular structure  10  and the rails below, or vice versa; rolls and rails also would be provided for the vessel head  92  to separately support it as it is inserted into the vessel.  FIG. 14  illustrates how the exo-skeleton  3000  may be employed to upend the entire cage-like, tubular structure  10  contained therein to permit the structure  10  to be lowered into the vessel  90  (not shown in  FIG. 14 ). 
       FIG. 15  illustrates an apparatus and method for positioning the vessel head  92  adjacent the end of the cage-like, tubular structure  10  once the latter has been completely assembled within the exo-skeleton  3000 . An upending fixture  94  having a curved portion is removably attached to the vessel head  92 . The dimensions of the fixture  94  are selected to match up and position the vessel head  92  in alignment with the mating portions of the headers  20  and other portions of the cage-like, tubular structure  10 , once the fixture  94  has been lifted and rotated counterclockwise about the curved portion as shown. Pushers, come-alongs or other devices can then be used to bring the vessel head  92  into mating position with the tubular structure  10 . 
       FIG. 16  illustrates how a typical, elongated n-pack  50  of tubes  14  would behave when lifted for placement onto an exo-skeleton subassembly  30  (not shown in  FIG. 16  for clarity). The same curvature of the n-pack panel  50  which facilitates insertion of the ends of the tubes  14  into the headers  20  at each end of the subassembly  30  (due to shortening of the n-pack  50  overall length) may also create the need for a panel/header tube end guide tool  100  as illustrated in  FIGS. 17 and 18 . The tool  100  is a C-clamp type device that has a claw action to retain its location when installed on the header  20 . There are four bosses in an end  102  of the tool  100  which fit the tube pattern in the header  20 . The other end of the C has a fastener that pushes into the OD of the header  20  in the opposite direction creating a lock of the tool  100  onto the header  20 . The ends of the tubes  14  will come to rest in the grooves in the tool  100 . As the n-pack panel  50  is lowered, the arch in the panel  50  begins to subside and the ends of the tubes  14  move outwardly towards and into the header  20  weld preps. Pushers  104  may be provided to keep the tubes  14  from gouging into the tool  100  too sharply as well as to push them down if they do not lay flat in the grooves. A wedging device  106  may also be provided to spread the tubes  14 , if required. A coating of nylon or other low friction material may be provided to allow slippage of the tubes  14  while clamped. 
       FIG. 19  illustrates how the keystone bracing  80  of  FIGS. 11 and 12  is provided to support and locate the platens  18  within the cage-like, tubular structure  10 . The folding structure  86  extends diametrically across the cage-like, tubular structure  10 , engaging opposed pairs of keystone bracing  80 . The pairs of keystone braces  80  may be spaced axially along the longitudinal axis A so as to not interfere with one another. 
     While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, those skilled in the art will appreciate that changes may be made in the form of the invention covered by the following claims without departing from such principles. For example, while the method and apparatus of the present invention has been described in the context of a cage-like structure for a synthesis gas cooler, it will be appreciated that the principles of the present invention may be applied to the manufacture, assembly and/or transportation of other cage-like structures having substantially cylindrical walls but which are not rigid, easily handled structures which can be easily manipulated. The present invention is particularly suited to the manufacture and assembly of cage-like, substantially cylindrical structures made of long, slender tubular components which, by themselves, are not self-supporting. Similarly, in some circumstances it may be desirable to install all the n-packs  50  for a given subassembly  30 , but not weld them to one another until after all tube  14  to header  20  welds have been seal welded, in order to seal, position, and manage distortion and shrinkage. Thus, in some embodiments of the invention, certain features of the invention may sometimes be used to advantage without a corresponding use of the other features, and certain features may be employed in a different order. Accordingly, all such changes and embodiments properly fall within the scope of the following claims.