Abstract:
A cleaning apparatus for removing a blockage from a heat exchanger tube of a steam generator, or the like, having a plurality of tubes extending between a pair of tube sheets. Anchor plate fasteners, which are expandable inside tubes adjacent to the blocked tube, are used to mount an anchor plate to one of the tube sheets. The anchor plate has an opening for aligning in registry with the condenser tube having the blockage and provides a solid platform for mounting either a mechanical device or a fluid pressure device for providing a force against the blockage for removal of the blockage. The cleaning apparatus enables a force to be applied which is significantly greater than that which can be applied with known hand-held devices for removing blockages.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an apparatus and method for removing a blockage from a heat exchanger tube, such as a condenser tube of a steam generator. 
       BACKGROUND OF THE INVENTION 
       [0002]    Heat exchanger tubes, such as those provided in a condenser for a steam generator, often suffer from blockages which render the tube inoperative and reduces the efficiency of the steam generator. Various methods have been used to remove such a blockage, such as forcing a fluid driven projectile or scraper through the tube from an opening in a tube sheet, that aligns a plurality of tubes having openings through which fluid can flow. However, it is not always possible to remove a blockage by this known method, especially if the blockage is across the entire opening of the tube. 
       SUMMARY OF THE INVENTION 
       [0003]    A tube cleaner is provided for removing a blockage from a heat exchanger tube, where the blocked tube is part of an array of tubes and where a tube sheet has spaced openings in alignment with open ends of the tube array. The tube cleaner includes an anchor-plate mountable on the tube sheet, and the anchor plate has a plurality of anchor plate openings passing through the plate, that are in registry with the openings in the tube sheet. At least one anchor plate fastener is provided on the anchor plate that secures the anchor plate to the tube sheet, with the open end of a blocked tube in registry with another anchor plate opening of the anchor plate. The anchor plate also includes means for mounting thereon a tube cleaner apparatus with access to the blocked tube and means for providing a driving force into the blocked tube, to dislodge and remove the blockage from the tube. 
         [0004]    The force for removal of the blockage may be provided, for example, by a flexible coil spring that is inserted through the anchor plate and into the open end of the tube, where the flexible coil spring is driven by a hydraulic drive to incrementally urge the same against the blockage to clear the blockage from the tube, or by a pressurized water gun that dislodges the blockage and urges the blockage through the tube. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]    The invention will become more readily apparent from the following description of preferred embodiments thereof shown, by way of example, in the accompanying drawings, wherein: 
           [0006]      FIG. 1  is a perspective view of a tube sheet and a blocked tube of an array of tubes, with the other tubes removed for clarity; 
           [0007]      FIG. 2  is a perspective view showing an anchor plate of the tube cleaner of the present invention, with a flexible coil spring of the tube cleaner inserted into a blocked tube; 
           [0008]      FIG. 3  is a side view similar to that of  FIG. 2  showing an expanded anchor plate fastener of the tube cleaner and the flexible coil spring manually inserted into the blocked tube to contact the blockage; 
           [0009]      FIG. 3A  is an enlarged view of a portion of  FIG. 3  for showing details of the anchor plate fastener of the tube cleaner; 
           [0010]      FIG. 3B  is an enlarged view of a portion of  FIG. 3  for showing details of a tube entry guide and a quick disconnect connector of the present invention; 
           [0011]      FIG. 4  is a side view similar to  FIG. 3  showing use of a driver for the flexible coil spring, the driver being set in a non-locked position and connected to a hydraulic advancer in a retracted condition; 
           [0012]      FIG. 4A  is an enlarged view of a portion of  FIG. 4  for showing details of the tube entry guide having the driver mounted thereon; 
           [0013]      FIG. 4B  is an enlarged view of a portion of  FIG. 4  for showing details of the attachment of the driver to the anchor plate, it is a cross-sectional view through a central axis of the quick disconnect connector; 
           [0014]      FIG. 5  is a view similar to  FIG. 4  showing a gripper of the driver in a locked position with the flexible coil spring; 
           [0015]      FIG. 6  is a view similar to  FIG. 5  showing completion of a hydraulic advancer stroke, with the hydraulic advancer in an extended condition, and advancement of the flexible coil spring against the blockage in the tube; 
           [0016]      FIG. 7  is a view similar to  FIG. 6  showing the gripper of the driver unlocked so that the hydraulic advancer can be pulled back and the gripper locked on the flexible coil spring again, for a further incremental advancement of the flexible coil spring; 
           [0017]      FIG. 8  shows, in views  8 A through  8 D, the sequence of the driver and the incremental advancement of the flexible coil spring; 
           [0018]      FIG. 9  shows a second embodiment of the heat exchanger tube cleaner wherein a pressurized fluid gun is used in conjunction with the anchor plate, as a method for removing a blockage; 
           [0019]      FIG. 10  shows the pressurized fluid gun attached to the tube entry guide for impingement of the pressurized water from the pressurized fluid gun to remove the blockage from a tube; 
           [0020]      FIG. 11  is a side view similar to that of  FIG. 10  showing impingement of the pressurized water from the pressurized fluid gun to remove the blockage from the tube; 
           [0021]      FIG. 11A  is an enlarged view of a portion of  FIG. 11 , for showing details of the tube entry guide having the pressurized fluid gun mounted thereon, and 
           [0022]      FIG. 12  is an enlarged view of an advancing end of the flexible coil spring for showing a plug attached thereto. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    The device of the present invention is for use on equipment of the type having a plurality of tubes arrayed between two tube sheets to which ends of the tubes are welded or mechanically connected. The equipment is most often used for exchanging heat to or from a medium inside the tube to a medium outside the tube. For efficient operation of the equipment, deposits formed on the inside of the tubes must be removed periodically. 
         [0024]      FIG. 1  shows one of the tube sheets  1  and, for clarity, only one of the tubes  2 . Typically, one tube would be associated with each opening  3  in the tube sheet. A blockage in the tube is indicated at  4 . The blockage might extend completely across the cross-section of the tube or might only partially block the tube. As discussed above, another tube sheet would typically be connected to the other end of the tube and the tube sheets would have a mirror image arrangement of openings. As shown in the example of  FIG. 1 , the openings are typically arranged in an orderly pattern, however, such an arrangement is not necessary for use of the present device. 
         [0025]    The present device is most useful for deposits on the insides of the tubes that are not removable by known brushes or scrapers that are forced through the tubes with use of water pressure, or the like, as a larger force is possible with the present device. Known devices primarily consist of operator-held high-pressure guns, having a nozzle which is inserted into the end of the tube, for forcing a brush or scrapper through the tube. In the operator-held high-pressure guns the pressure is limited to that which can be opposed to by the operator. The present device enables the use of much higher pressures, as is discussed below. 
         [0026]    In order to provide the force required to remove the blockage, an anchor plate  5 , which is of a size to extend across a plurality of openings  3  in the tube sheet, has preferably two anchor plate fasteners  6  that are arranged to be inserted into two of the plurality of tubes  2 , one on each side of the tube to be cleaned, as shown in  FIGS. 2 and 3 .  FIGS. 3 and 3A  show more clearly the anchor plate fastener  6  inserted in the tube  2 . Although two anchor plate fasteners are shown, any number are possible in practice of the invention. 
         [0027]    Each anchor plate fastener  6  is elongated and is of a diameter slightly less than the inner diameter of the tube to initially slide into the tube. Then, the anchor plate fastener is expanded in order to contact the inside surface of the tube to an extent that pressure used for clearing the blockage (to be described below) does not move the anchor plate fastener in the tube. The expandable portion of the anchor plate fastener is preferably disposed in the tube near a portion of the tube which is surrounded by the tube sheet in order that pressure from the expandable portion is less likely to damage the tube. Any type of known anchoring means, in which an outer diameter expands, is possible for use in the present invention. 
         [0028]    At a central portion of the anchor plate an anchor plate entry opening  8 , best viewed in  FIG. 2  is provided for positioning in registry with the tube  2 , which is to be cleared. In order to obtain the registry, the anchor plate can be provided with openings, for insertion of the anchor plate fasteners, which are properly spaced relative to the entry opening  8  for a particular heat exchanger or the like being repaired, or the openings  7  in the anchor plate for the anchor plate fasteners can be elongated for easily aligning the anchor plate fasteners  6  and aligning the entry opening  8  with the tubes, as shown in  FIG. 9  at  7 . 
         [0029]    The anchor plate further includes a means for mounting additional components of the tube cleaner for cleaning the blocked or partially blocked tube. The tube cleaner can provide either a fluid device for removing the blockage or a mechanical device for applying pressure and removing the blockage. One means for mounting either of the devices, although in differing manners, is the known quick disconnect connector manufactured for example by Snap-Tite, Union City, Pa., which is best viewed in  FIGS. 3-3A  at  9 , and in  FIGS. 9  at  9  and  17 . As shown in more detail in  FIG. 3B , which is a cross-sectional view through a central axis of the quick disconnect connector, one mating portion  9  of the quick disconnect connector is connected to a tube entry guide  10  mounted on the anchor plate.  FIGS. 3A-3C  show the mating portion  9  attached to the tube entry guide  10 , prior to mounting either the mechanical device or the fluid device. 
         [0030]      FIGS. 4A-4B  show the driver  12  of the mechanical device, mounted to the anchor plate  5  by sliding a slotted portion of the driver, indicated at  12   a , to be disposed between the anchor plate  5  and a flange  9   a  of the quick disconnect connector. As mentioned above the quick disconnect connector is used in different manners for mounting either the fluid device or the mechanical device and  FIG. 9  shows the same mating portion  9  of the quick disconnect connector, prior to having the fluid pressure device coupled with use of mating portion  17 .  FIG. 10  shows the fluid pressure device mounted by engaging the mating portions  9  and  17  of the quick disconnect connector. The mating portion  17  preferably is not a part of the driver  12  of the mechanical device, however the other mating portion  9  can remain in place on the anchor plate for later use with the fluid pressure device. 
         [0031]      FIGS. 4-8  show the use of the mechanical device of the cleaning apparatus for removing the blockage. The mechanical device includes a flexible coil spring  11  that is preferably initially inserted by hand into the blocked tube. The flexible coil spring  11  is of a diameter slightly smaller than the inside diameter of the tube, and it is inserted until it makes contact with the blockage. An outer diameter of the flexible coil spring is preferably 80-90% of the inside diameter of the tube. The flexible coil spring is preferably made of metal and is of a length to enable advancement of the blockage to the distal end of the tube and then finally out the distal opening of the tube, if necessary. The flexible coil spring is of the type referred to as a tension flexible coil spring in which the wire of the spring is helically wound, with each successive winding being in contact with the previous winding. 
         [0032]      FIGS. 4-8  show the driver  12  for advancing the flexible coil spring and applying pressure on the blockage. The driver  12  includes a mechanical means for locking a gripper  13  on the flexible coil spring with use of a lever  14 . The gripper is in turn attached to a hydraulic advancer  15  which advances the flexible coil spring and which can apply a pressure of up to about 5,000 pounds to the blockage. 
         [0033]    Although the flexible coil spring has flexibility, which facilitates transporting and usage, when it is constrained within the tube  2  it has the properties of a solid rod to transfer the force from the hydraulic advancer  15  to the blockage in the tube. Use of a flexible coil spring having a diameter less than that indicated above, however, may cause the flexible coil spring to buckle inside the tube and possibly rupturing the tube. 
         [0034]    To provide lateral constraint for the portion of the flexible coil spring outside of the tube and to facilitate feeding the flexible coil spring into the tube, a tube entry guide  10  is provided in the anchor plate entry opening  8  as shown in  FIGS. 3A-3C . Preferably the tube entry guide extends a short distance into the tube when the anchor plate is mounted to the tube sheet. 
         [0035]      FIGS. 4-6  show the driver  12  in various stages of its usage, and  FIG. 8  shows the sequence of operation of the driver. In  FIG. 4 , the flexible coil spring  11  is positioned through the gripper  13 , however the gripper is not yet locked on the flexible coil spring. In  FIG. 5 , the lever  14  is shown rotated in a counter-clockwise direction so as to lock the gripper on the flexible coil spring. In both  FIGS. 4 and 5  a piston  16  of the hydraulic advancer  15  is at a retracted position. Also, a distal end of the flexible coil spring is in contact with the blockage  4 . 
         [0036]      FIG. 6  shows the driver  12  as it is positioned following advancement of the piston  16  of the advancer to it&#39;s extended position. Advancement of the piston moves the flexible coil spring deeper into the tube thus applying pressure to the blockage in order to advance the blockage in the tube. Depending on the nature and material of the blockage, the blockage may be fractured into smaller pieces when first advanced, leading to easy removal, or additional movement of the blockage toward the distal end of the tube may be required, if the blockage is not freed. 
         [0037]      FIG. 7  shows the lever  14  rotated clockwise from the position shown in  FIG. 6 , thus releasing the locking of the gripper on the flexible coil spring. Following the releasing from the flexible coil spring, the piston  16  of the hydraulic advancer  15  is free to return to the retracted position in order to carry out additional advancements of the flexible coil spring. 
         [0038]      FIG. 8  shows the above described sequence for advancing the flexible coil spring. The sequence begins at  8 A at the top drawing and advances as indicated by the arrows to finish at  8 D. The sequence can be repeated as many times as necessary until the blockage is removed. 
         [0039]    As mentioned above, the blockage may fracture into smaller pieces with one application of the pressure, however it might be necessary to advance the blockage entirely to the end of the tube in order to remove it. Upon elimination of the blockage, the flexible coil spring can be removed from the tube manually by releasing it from the gripper and pulling it backward out of the tube. With the coil spring being flexible, it is easily stored or transported. 
         [0040]    In some applications a plug  20 , as shown in  FIG. 12 , can be used at the advancing end of the flexible coil spring. Preferably, the plug has a diameter slightly larger than the outer diameter of the flexible coil spring, and it can have threads for screwing into the hollow core of the flexible coil spring. A flat advancing face is preferred on the plug. 
         [0041]    Another method for removing a blockage is with the use of a liquid under high pressure. The anchor plate, described above, along with the tube entry guide  10 , is used for connecting the above-discussed quick disconnect connector  9 , as shown in  FIGS. 9-11 . Preferably, when the high pressure liquid device is used, an 0-ring, or the like is used between the outer surface of the tube entry guide and the inside of the tube, in order to prevent leakage of the high pressure liquid. 
         [0042]    The high pressure liquid device is attached to a high pressure source of fluid, such as water, having a pressure up to about 2000 pounds/in 2 . A preferred operating range is from about 800-2000 pounds/in 2 . The high pressure fluid gun  18  includes a pressure gauge  19  for use in monitoring the pressure of the fluid. With use of the anchor plate  5  of the invention having the tube entry guide  10  and the quick disconnect connector, it is convenient to switch between the high pressure fluid gun  18  and the driver  12 , in order to remove the blockage from the tube in the most efficient manner.  FIGS. 4A-B  show, in an enlarged view, the anchor plate  5  having the driver  12  mounted, and  FIG. 11A  shows, in an enlarged view, the anchor plate  5  having the high pressure fluid gun  18  mounted.