Abstract:
A system for protecting tubes in a heat recovery system is provided. Such tubes are often protected by shielding that is attached thereto the tubes by a plurality of band clamps. Each band clamp is associated with a guard that protects the same from the hot gases traveling through the field of tubes. In addition, an automated tool is provided for tensioning the bands about the shields. The automated tool allows the band clamps to be properly interconnected to the shields in a preferred manner.

Description:
[0001]    This application claims the benefit of U.S. Provisional Patent Application Ser. No. 61/382,830, filed Sep. 14, 2010, entitled “Band Tensioning Tool,” and U.S. Provisional Patent Application Ser. No. 61/382,833, filed Sep. 14, 2010, entitled “Band Clamp Guard,” the entire disclosures of which are incorporated by reference herein. 
     
    
     FIELD OF THE INVENTION 
       [0002]    Embodiments of the present invention are generally related to band clamps used to secure protective shielding onto tubes, pipes, or other structures (hereinafter “tubes”) used in high temperature and harsh environments. The band clamps employ a protective guard that helps maintain the integrity of the band clamp. The band clamps described herein may be secured about the shield using an easy to use hand-held tensioning tool. 
       BACKGROUND OF THE INVENTION 
       [0003]    Fuel burning power plants employ steam generating boilers that remove heat from exhaust generated by the combustion of coal, oil, gas, or other fuel. The heat obtained from the exhaust is used to produce steam by transferring heat from hot, fast-moving exhaust gases to water or other heat transfer fluid flowing in a series of horizontally or vertically oriented tubes that are positioned in the path of the exhaust. Such exhaust contains heated gas and significant particulate in the form of carbon, acidic materials, caustic materials, etc. that contact the tubes at high speed. Further, over time, the tubes often become coated or caked with soot, an insulator, which adversely affects heat transfer and boiler performance. The soot is removed by soot blowers that employ a series of nozzles that direct high speed steam at the tubes to remove the soot. Continued exposure to the particulate and hot gases generated by the coal burning process and the soot removal process will erode and weaken the tubes and eventually cause the tubes to leak or burst. After a number of tubes deteriorate to such a degree which is evidenced by an unacceptable coolant pressure drop. When this occurs, the furnace must be shut down and the boiler must be removed from service so that costly and time consuming repairs may be performed on the network of tubes in the system. 
         [0004]    To address the erosion issue, the tubes are protected by a contoured shield that covers the outer surface of the tube. In most instances, the shield covers and protects approximately one-half of the surface of the tube, namely the surface of the tube that is in the direct path of the particulate generated by the furnace. Shields commonly protect an area defined by the length of the tube and about 120 to 220 degrees about the tube&#39;s outer surface. In some instances, a plurality of shields are abutted or interlocked to protect longer tube spans. To maximize heat transfer in the presence of a shield, shields are configured such that their inner surface snuggly and fully engages the outer surface of the tube. The tubes are held in place by support members including straps, hose clamps, metal bands, or by other methods known in the art, which may be welded or otherwise interconnected to the shield. In some applications the shield is welded directly to the tube. Because the support members are also exposed to high temperatures and the same abrasive conditions as the tubes, it is desirable to protect support members from particulate impingement and increased heat which, over time, may lead to failure and cause the shield to separate from the tube thereby exposing the tube to the abrasive conditions. 
         [0005]    Band clamps are generally comprised of a band having a free end and an opposing end having a buckle, or other member, for receiving the free end. In operation, the band is wrapped about the tube and associated shield and the free end is placed within a buckle. A powered or hand-operated tool is used to tension the band about the shield. After a predetermined tension has been achieved, the buckle and band are interconnected or interlocked, and excess band length extending from the buckle is severed from the band at a point adjacent to the buckle. The buckle is typically positioned behind the shielded tube away from the abrasive flow. That is, the interconnection between the band and the buckle is a prime yielding spot, and as such, it is desirable to place the interlocking portion of the band clamp in a location where it will be exposed to less heat and debris. Thus, an operator or installer is instructed to position the buckle on the downstream side of the tube out of the direct path of particulate. Unfortunately, the size of the tubes and spacing between tubes often render it very difficult for an operator to properly locate the tensioning tool behind or on the downstream side of the shielded tube. Furthermore, the cutting operation performed by existing tools is not very precise and the sharp severed portion of the band often injures installers as they try to tension nearby bands or work in the vicinity of these bands. 
         [0006]    Thus, it has been a long-felt need to provide a system for securing a shield onto a tube that is capable of withstanding harsh environments and that is easy to install. It has also been a long felt need to provide a system that cuts a band in a manner that reduces exposure to sharp edges of a cut band. The following disclosure is generally directed to a guard that protects a band clamp to which it is interconnected and to a tool that facilitates proper interconnection of the band clamp to the tube. 
       SUMMARY OF THE INVENTION 
       [0007]    It is one aspect of the present invention to provide a band clamp that employs a protective guard. Band clamps of embodiments of the present invention include a free end and an opposing end, which includes a buckle for receiving and securing the band. To secure the band clamp about a shield and tube, the band is wrapped at least once around a shield and tube and the free end is placed within the buckle. Transitioning and locking the band securely engages the shield in contacting relation to the tube so that efficient heat transfer can occur across the thickness of the shield and the tube. The band clamp used in one embodiment of the present invention will provide a retained force of about 400-900 lbs. with a looped tensile force of about 1,750 lbs. 
         [0008]    The protective guard used by some embodiments protects the band clamp from hot, high-speed, particulate-laden exhaust gasses. The guard may be made of a material that is capable of withstanding temperatures up to about 880° F. and which is similar to that of the band clamp so that efficient heat transfer to the tube and inner coolant will occur across the thickness of the guard and the band. In one embodiment the guard is made of 310 stainless steel, carbon steel, inconel, or other similar material and is about 0.090 inches thick. Those of skill in the art will appreciate that the material of manufacture, thickness, width, material properties, etc. of the guard may vary as a function of shield and band clamp size, material, etc. Further, in some embodiments, the guard is made of a material that is easy to conform to the outer shape of the shield, i.e., bend into a curved shape, to facilitate engagement with a curved band clamp that is to be positioned about a shielded tube. The guards may be pre-bent or otherwise formed. The guard of some embodiments is adhered, bonded, or welded to, or otherwise interconnected to the band clamp. In one embodiment, the guard possesses openings that receive the free end of the band to facilitate interconnection of the band clamp and shield, which will be apparent upon review of the figures discussed below. In this way, it is ensured that the guard is correctly associated with the band clamps. It is another aspect of the present invention to provide a guard that is easy to install as band clamps are sometimes used in hard-to-access places. 
         [0009]    It is a related aspect of the present invention that the guard be able to accommodate band clamps of various types and/or sizes. More specifically, as the tubes used in heat recovery steam generators vary in size, so must the band clamps that secure the shields to the tubes. Accordingly, in another embodiment of this invention, the width of the guard is large enough that a variety of band clamps of different widths may be used and not exposed to abrasive material in the flow stream. 
         [0010]    It is another aspect of the present invention to provide a compact and light-weight tool that facilitates interconnection of the band about a shielded tube. A commonly used tool employs a cutting member having an opening for receipt of the free end of the band. The opening is further defined by upper and lower cutting members that selectively move together to sever the band. After passing through the opening, the free end of the band is associated with a winding mandrel and tensioned. After a predetermined tension is reached, the cutting mechanism is used to sever and bend the band at a point adjacent to the buckle. 
         [0011]    As briefly mentioned above, it is often difficult to access a buckle located behind a shielded tube with hand-held tools currently used. More specifically, because spacing between adjacent tubes and surrounding structure is often small, it is difficult to position and use traditional tools to tension the band clamp about a shielded tube with the buckle located on the downstream side of the tube. As a result, band clamps are often fastened to the shielded tubing in an incorrect orientation, exposing the buckle and the band to the abrasive environment, which accelerates band clamp deterioration and which may also locate the severed portion of the band in such a way that will increase the risk of injury. In addition, a lack of clearance or proper access to the buckle and free end of the band may also affect the application of the proper amount of band tension when a manually- actuated hand-held tool is used. To address these issues, an automated tool is provided. 
         [0012]    More specifically, an automated tensioning tool is provided that employs a powered winding mandrel. Preferably, the tool is battery powered, but one of skill in the art will appreciate that the tool may receive the required power by way of a cord or be hydraulically driven. The power source associated with the tool of one embodiment is a replaceable battery that allows for the installation of about 60 to 70 band clamps. In one embodiment of the present invention, the mandrel is interconnected to a rotary shaft by way of a gearing system that ensures that the proper tension will be applied to the band. Further, to improve band cutting, the cutting mechanism of embodiments of the present invention extends laterally from the longitudinal axis of the mandrel as opposed to coaxial therewith. Initiation of mandrel winding is accomplished by depression of a button located on or near the hand grip. After the band reaches a predetermined tension, an easy-to-access cutter mechanism is used to sever the free end of the band. The predetermined amount of tension may be controlled by a clutch that will slip, thereby preventing further tensioning, when a preset tension level is reached. The cutter mechanism of some embodiments has the advantage of decreasing the amount of severed band extending from the buckle and thereby reducing exposure to the cut edge. 
         [0013]    It is another aspect of the present invention to provide a tensioning tool that employs a gear box that increases the torque provided by the motor. More specifically, common, commercially available drills provide about 250 in lbs. of torque. However, in order to tension the bands effectively, a torque of between about 1,800 to 3,000 in lbs. is needed. The gear box of embodiments of the present invention produces the required increase in torque. 
         [0014]    It is another aspect of the present invention to provide a band tensioning and cutting tool, comprising: a power source for providing rotational movement to a shaft; a gear box mechanically associated with the shaft; a rotating mandrel associated with the gear box wherein rotation of the shaft will rotate the mandrel, the mandrel adapted to receive a band and tension the same, the gear box having a means for preventing over tensioning the band; and a cutting mechanism positioned adjacent to the mandrel, the cutting mechanism also adapted to receive a portion of the band. 
         [0015]    It is yet another aspect of the present invention to provide a band tensioning and cutting tool, comprising: a drill having a rotating shaft; a gear box interconnected to the drill with an adapter, the gear box operatively associated with a winding mandrel such that rotation of the shaft rotates the mandrel, and a clutch that prevents over tensioning the band; and a cutting mechanism positioned adjacent to the mandrel, the cutting mechanism also adapted to receive a portion of the band. 
         [0016]    It is another aspect of the present invention to provide a guarded band clamp that will hold a shield onto a tube over many heating and cooling cycles. In one embodiment an Ultra-Lok® band clamp, which is described in U.S. Pat. No. 6,014,792 (which is incorporated by reference herein), or similar band clamp is used to secure the shield to the tube. The contemplated tool tensions the band to such a degree that even if the retained force decreases over time as a result of repeated heat cycles, the shield will remain securely engaged onto the tube. Further, the guarded band clamp of one embodiment will function for about 5 to 8 years. In addition, the band tension provided by the band will overcome bent or deformed shields and force the shield to conform to the exterior shape of the shield and the tube. Such functionality ensures that the shield is in contact with the tube, thereby increasing heat transfer. 
         [0017]    It is another aspect of the present invention to provide a tensioning tool that provides smooth, continuous tensioning as opposed to incremental, ratchet-type tensioning which provides tension in a series of discreet tensioning steps. As those of skill in the art will appreciate, a ratcheting mechanism employs a toothed wheel that is rotatable in only one direction. Rotation in an opposite direction is prevented by interaction between the toothed wheel with a movable pawl. The tool and associated gear box of embodiments of the present invention do not have such limitation because tensioning increments are very small or non-existent and are provided by a one way clutch bearing. 
         [0018]    It is yet another aspect of the present invention to provide a system for protecting tubes that may be exposed to extreme temperatures, moving particulate and other harsh environments. The system of one embodiment includes a band clamp, an associated guard, and a tool for tensioning the guarded band clamp about a shielded tube of a boiler. The system of one embodiment of the present invention works with about 1 to 4 inch diameter tubes that are about 0.1 to 0.3 in. (about 3, 5, and 7 mm) thick that protect 180 degrees of the tube. 
         [0019]    It is another aspect of the present invention to provide a combination band clamp and guard, comprising: a band clamp comprised of a band having a buckle associated with one end and a free end; a guard having a first end and a second end, the first end of the guard located adjacent to the buckle and the second end spaced from the first end wherein the guard contacts at least a portion of the band. 
         [0020]    It is still yet another aspect of the present invention to provide a method of shielding a tube comprising: providing a shield about at least a portion of the tube; providing a band clamp having a first free end and a second end having a buckle; providing a clamp guard interconnected to the band clamp; placing the band clamp and guard about the shield; placing the free end of the band into the buckle; and pulling the free end of the band relative to the buckle to tensioned band about the shield. 
         [0021]    The Summary of the Invention is neither intended nor should it be construed as being representative of the full extent and scope of the present invention. Moreover, references made herein to “the present invention” or aspects thereof should be understood to mean certain embodiments of the present invention and should not necessarily be construed as limiting all embodiments to a particular description. The present invention is set forth in various levels of detail in the Summary of the Invention as well as in the attached drawings and the Detailed Description of the Invention and no limitation as to the scope of the present invention is intended by either the inclusion or non-inclusion of elements, components, etc. in this Summary of the Invention. Additional aspects of the present invention will become more readily apparent from the Detail Description, particularly when taken together with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]    The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate embodiments of the invention and together with the general description of the invention given above and the detailed description of the drawings given below, serve to explain the principles of these inventions. 
           [0023]      FIG. 1  is a partial perspective view showing a shield interconnected to a tube with a guarded band clamp; 
           [0024]      FIG. 2  is a front elevation view of  FIG. 1 ; 
           [0025]      FIG. 3  is a perspective view showing a guard incorporated on a band clamp; 
           [0026]      FIG. 4  is a front elevation view of a guarded band positioned about a shielded tube; 
           [0027]      FIG. 5  is a perspective view of the guard of one embodiment of the present invention; 
           [0028]      FIG. 6  is a front elevation view of  FIG. 5 ; 
           [0029]      FIG. 7  is a schematic of an automated band tensioning tool of one embodiment of the present invention; 
           [0030]      FIG. 8  is a perspective view of an automated band tensioning tool of one embodiment of the present invention that employs a drill; 
           [0031]      FIG. 9  is a front elevation view of  FIG. 8 ; 
           [0032]      FIG. 10  is a perspective view showing portions of a plurality of shielded tubes as may be oriented in the exhaust path of a boiler with a tool of one embodiment positioned between adjacent tubes; 
           [0033]      FIG. 11  is a top plan view of  FIG. 10 ; 
           [0034]      FIG. 12  is a cross-sectional of a gear box used in the embodiment of the present invention shown in  FIG. 8 ; and 
           [0035]      FIG. 13  is an exploded perspective view of  FIG. 12 . 
       
    
    
       [0036]    It should be understood that the drawings are not necessarily to scale. In certain instances, details that are not necessary for an understanding of the invention or that render other details difficult to perceive may have been omitted. It should be understood, of course, that the invention is not necessarily limited to the particular embodiments illustrated herein. 
       DETAILED DESCRIPTION 
       [0037]      FIGS. 1 and 2  show a tube  2  associated with a boiler. One of skill in the art will appreciate that boiler tubes  2  may be oriented in a variety of positions, including vertical, horizontal, and in-between. The tubes  2  are protected by shields  6  that are interconnected thereto by a plurality of band clamps  10  positioned at spaced intervals. Preferably, a buckle  14  and severed end  18  of the band clamps  10  are positioned downstream relative to the oncoming flow  22  of hot gases traveling through boiler. In some boiler systems, the tubes  2  are spaced approximately 1.3 inches by 8 inches apart and thus interconnecting the band clamps  10  in the preferred matter is difficult. To secure the band clamp  18  about a shielded tube, a free end  64  of the band clamp  18  is placed in the buckle  14  and the band  42  is tensioned using a tool. After tensioning, the excess band is severed from the band and the guard  26  remains in place to protect the band clamp  10 . 
         [0038]      FIGS. 3-7  show a band clamp  10  associated with a guard  26  of one embodiment of the present invention that has a first end  30  and a second end  34 . The band clamp  10  shown may be any type of band clamp comprising a band with interconnected buckle, or other means for interconnecting, known in the art. Slots  38  are positioned adjacent to each end that are adapted to receive a band  42  of the band clamp  10 . Further, the slots  38  may be located in a jog  44  or transition area of the guard  26 . The band  42  of the band clamp  10  is received within the slots  38  and positioned such that an outer surface  48  of the band  42  is abutted against the inner surface  52  of the guard  26 . The first end of the guard  30  is positioned adjacent to the buckle  14  of the band clamp  10 , which helps maintain the guard  26  in place as the band clamp  10  is tensioned. Further, the guard is spot welded  56  or otherwise secured to the band, which ensures that the position of the guard relative to the buckle  14  is maintained during tensioning. 
         [0039]    As shown in  FIG. 4 , the guard  26  of one embodiment is curved to generally match the contour of the shield. In operation, the guard  26  is resiliently deflected outwardly and engaged onto the shield  6 . The jogs  44  are designed to coincide with and engage the edges  60  of the shield  6 , which maintains the position of the guard  26  on the shield  6 . Further, as the weld  56  maintains the position of the buckle  14 , relative to the shield, engagement of the jog  44  onto the edge  60  of the shield will locate the buckle  14  on the downstream side of the pipe and generally out of the flow stream. 
         [0040]      FIG. 4  also shows that the band  42  of one embodiment has bent ends  64  and  68  that assist threading the band within the buckle  14  and tightening by hand before using a tool to perform the final tightening and complete the installation. More specifically, the bent end  64  allows the free end tip to pass thru the buckle  14  and not become obstructed by the jog  44 . Further, the bent end  68  near the buckle  14 , which is bent in an opposite direction from the free end  64 , allows the band  42  to be pulled without digging into end  68 , which reduces friction during installation. 
         [0041]    Referring now to  FIGS. 8-11 , an automated tensioning tool  100  of one embodiment of the present invention is shown that uses a rotary tensioning device, such as a drill  102  to rotate a winding mandrel  106 . The rotary tensioning device  102  is associated with a tool head  110  and winding mandrel  106  via a clutch  114 , gear box  118 , and bearing  122 . 
         [0042]    Referring now specifically to  FIGS. 8 and 9 , in one embodiment of the present invention a conventional battery powered hand drill  102  is utilized. The drill  102  is interconnected to a gear box  118  via an adapter  126 . The gear box  118  is interconnected to the drill  102  with the adapter  126  supporting the weight of the gear box  118 . The gear box  118  is also associated with a head  110  that includes the winding mandrel  106 . In operation, a portion of the wrapped band is placed through a front slot  130  or side slot  134  of a cutting mechanism  138  and then positioned within a slot  142  of the winding mandrel  106 . Actuation of a button or other switch directs the drill  102  to begin winding the band around the mandrel  106 . The a clutch associated with the gear box  118  ensures that the winding torque provided to the mandrel  106  does not over tighten or under tighten the band clamp. After the desired tension is achieved an adjustable torque- limiting clutch associated with the gear box  118 , as is known in the art, slips and prevents over tensioning of the band. The slipping clutch may make a noise to notify the operator that the proper amount of tension has been reached. A cutter arm  150  is rotated to cause a blade  154  to sever the excess portion of the band. The cutting mechanism may be automatic wherein after a predetermined tension is reached, the band is automatically severed. Alternatively, after tensioning is complete, the operator may actuate a button, for example, to cause the cutting mechanism to sever the band. 
         [0043]      FIGS. 10 and 11  are a representation of vertically-oriented tubes  2  of a boiler  160 . As outlined above, the tubes  2  may be positioned in most any orientation. The tubes  2  are protected by shields  6  that are interconnected thereto by a plurality of spaced band clamps  10 . Preferably, the buckle  14  and severed end  18  of the band clamps  10  are positioned downstream relative to the oncoming flow  22  of hot gases and particulate traveling through the boiler  160 . In some instances, the tubes  2  are spaced approximately 1.3 inches apart and thus interconnecting the band clamps  10  in the preferred manner is difficult. 
         [0044]    Referring now specifically to  FIGS. 12 and 13 , the gear box  118  of one embodiment of the present invention has an input shaft  170  that is associated with the drill. The input shaft  170  is also associated with a planetary gear system  174  that provides the proper torsion to the winding mandrel. The planetary gear system  174  is designed for high tension workloads wherein over 100 times the amount of torque that is input into the gear box  118  by the drill may be delivered to the mandrel  106 . In one embodiment the tool is able to provide about 1200 to 1500 lbs. of tension. The tool of one embodiment of the invention uses a gear box commonly used in vehicle winches manufactured by Warn Industries. Although a planetary gear system is shown and described herein, one of skill in the art will appreciate that the other torque increasing mechanisms may be employed without departing from the scope of the present invention. The tool may employ a tension clutch bearing and a holding clutch bearing that holds the mandrel in place and prevents it from recoiling. 
         [0045]    In one embodiment of the present invention is adapted to tension an about 3 mm thick by about 1.75 inch diameter half-moon mild steel shield to a tube. Furthermore, embodiments of the present invention disclosed herein are battery operated and thus do not have cords or pneumatic air lines. Some embodiments of the present invention provide a maximum clamping force of about 690 lbs. It will also be apparent from the review of the figures that the band can be loaded into the tool by either threading it into the cutting mechanism  138  directly into the front slot  130  or side loaded through the side slot  134 , which allows the tool to fit in the limited space available. In addition, the mandrel  106  can accept the band regardless of tool grip  178  orientation. More specifically, the mandrel  106  of some embodiments employs at least two slots  142  for receiving the band. For example, the grip  178  can be positioned at three-o&#39;clock or nine o&#39;clock and the mandrel  106  can be selectively rotated to properly align a slot  142  to receive the band. The band can be inserted sideways into the aligned slots  142 , or the free end of the band can be threaded directly through cutting mechanism into the mandrel  106 . Having the option of side to or direct loading allows operation in tight spaces. End loading also allows the band to be received at any point along the length of the band. To further aid the operator, tools of embodiments of the present invention employ a removable cut off handle  150  wherein different cut off handles can be used depending on the work space. 
         [0046]    Furthermore, the buckle of the band clamp is locked into place by the tool which prevents the buckle from slipping out of the blade during forming and band cutoff. More specifically, the cutting mechanism  138  is equipped with a feature that catches the buckle and will not allow the buckle to move away from the cutting mechanism during cutoff. The cutting mechanism pushes down on the buckle which forces the band down against the blade and a shear plate to sever the band. As the band is severed, the band also stretches which allows room for the buckle to move away from the blade and shear plate. The buckle catch on the cutting mechanism will not allow the buckle to move away from the blade and shear plate which improves cut-off. That is, the blade maintains proper alignment between the cutting planes of the blade and the buckle to perform cuts under no tension as a one-way bearing in the gear box will maintain band tension when winding is ceased. 
         [0047]    While various embodiments of the present invention have been described in detail, it is apparent that modifications and alterations of those embodiments will occur to those skilled in the art. However, it is to be expressly understood that such modifications and alterations are within the scope and spirit of the present invention, as set forth in the following claims. Further, the invention(s) described herein is capable of other embodiments and of being practiced or of being carried out in various ways. In addition, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.