Abstract:
A nozzle assembly for use in cleaning tubular members of a tube-type heat exchange having a protective coating. A metal nozzle core for communicating with a source of high-pressure water is covered at an exterior portion thereof with a plastic nozzle sleeve for engagement with the heat exchanger. A circumferential ridge of the nozzle core disposed in a circumferential groove of the nozzle sleeve prevents separation of the nozzle core and nozzle sleeve during use.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to an apparatus for cleaning tubular members of a tube-type heat exchanger. 
       BACKGROUND OF THE INVENTION 
       [0002]    Tube-type heat exchangers are typically made up of a large number of tubes extending between spaced-apart tube sheets. Walls of the tubes are relied upon for transferring heat from a medium on one side of the wall to a medium on the other side. During extended use of the heat exchanger, material from the various mediums is known to collect on both inner and outer surfaces of the tubes, causing a substantial decrease in the rate of heat transfer, and a decrease in the efficiency of the device. 
         [0003]    In order to properly maintain a heat-exchanger, surfaces of the heat exchanger tubes are periodically cleaned in order to remove any material which has accumulated on the surfaces. 
         [0004]    The present invention is concerned with cleaning inner surfaces of the tubes. A method is known in which a brush or scraping device of a generally cylindrical shape is moved through a tube from one end to the other end so as to brush or scrape away the accumulated material. In one known method a diameter of the brush or scraper is selected to be slightly less than an inner diameter of the tube and water at a high pressure is used to move the brush or scraper through each tube. The brush or scraper is manually inserted into one end of the tube, then a nozzle, through which the high pressure water flows, is positioned and held against the end of the tube in order to direct the high pressure water through the tube to transport the brush or scrapper through the tube. The accumulated material is removed from the inner surface of the tube and flushed out the other end by the water. Such method is known to provide a very effective tube cleaning method, however, when used on certain types of heat exchangers, damage to tubes or tube sheets of the heat exchanger can result. In particular, some heat exchangers are fabricated to have a protective coating on the tubes and tube sheets in order to control corrosion of their surfaces and when the nozzle, through which the high pressure water flows, is made to contact the heat exchange, damage may result. 
       OBJECT OF THE INVENTION 
       [0005]    It is an object of the present invention to provide a means for directing a high pressure stream of water to move a cleaning device along the inner surface of heat exchanger tubes without causing damage to surfaces of the tubes or the tube sheets supporting the tubes. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention is a nozzle assembly for use in a cleaning process using cleaning devices for tubular members of a heat exchanger. The nozzle assembly has a nozzle core for communicating at an input end thereof with a source of high pressure fluid to direct same along a central axis to an output end thereof, and a nozzle sleeve, for engaging an external portion of the nozzle core at the output end. The nozzle sleeve bears against the end of the tubular member of the heat exchanger to protect the tubular member and properly locate the nozzle assembly in the tubular member during the cleaning process. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The invention will become more readily apparent from the following description of a preferred embodiment thereof shown, by way of example only, in the accompanying drawings, wherein: 
           [0008]      FIG. 1  is a section drawing showing a method of cleaning tubes of a heat exchanger in which a nozzle assembly of the invention is used; 
           [0009]      FIG. 2  is a perspective view of the nozzle assembly of the invention; 
           [0010]      FIG. 3  is a perspective view of a nozzle core component of the invention; 
           [0011]      FIG. 4  is a side view of the nozzle core component of the invention; 
           [0012]      FIG. 5  is a side view of the nozzle sleeve component of the invention; 
           [0013]      FIG. 6  is a sectional view of the nozzle core of the invention; 
           [0014]      FIG. 7  is a sectional view of the nozzle sleeve of the invention; and 
           [0015]      FIG. 8  is a sectional view of the nozzle assembly of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    The present invention is a nozzle assembly having an inner nozzle core of a high strength material for containing and directing high pressure water or other cleaning fluid, and an outer nozzle sleeve, for engaging the nozzle core, of a material that does not result in damage to heat exchanger tubes or tube sheets during a cleaning operation. 
         [0017]      FIG. 1  is a sectional view of a known heat exchanger tube and tube sheets which support the tube, a known cylindrical cleaning brush, and the nozzle assembly of the invention. The heat exchange tube  1  is typically a thin-walled metal tube which extends from a first tube sheet  2  to a second tube sheet  3 . The tube is typically sealed to the tube sheets by welding or mechanically rolling an end portion of the tube with an edge portion of a hole in the tube sheet through which the tube is inserted. In order to control corrosion of the surfaces of the tubes and tube sheets a coating  4  can be applied to their surfaces. In order for the coatings to be completely effective, a continuous coating, absent any nicks or scratches, is necessary. 
         [0018]    Shown inside heat exchange tube  1  is a tube cleaning brush  5  which is moved along the length of the tube in order to remove material which has accumulated on the surface of the tube during use of the heat exchanger. The brush is typically moved along the tube with use of high-pressure water and it exits the tube at the other end. In addition to a cleaning brush, scrappers or the like (not shown) can be used in the cleaning process. 
         [0019]    The nozzle assembly of the invention is shown at  6 . In carrying out the method of cleaning, the nozzle is inserted into an end of the tube  1  to direct a high-pressure stream of water through the tube to propel the brush through the tube and exit the other end. The high-pressure stream of water both propels the brush and flushes the removed material from the tube. The nozzle assembly  6  is in communication with a source of the high-pressure water (not shown) having a valve for interrupting the flow. A gun having a trigger mechanism for operating the valve, for example, can be used with nozzle assembly  6 . 
         [0020]    Nozzle assembly  6  is shown in perspective view in  FIG. 2 . The nozzle assembly is made up of a nozzle core  7  and a nozzle sleeve  8 . In a preferred embodiment the nozzle core is fabricated of stainless steel and the nozzle sleeve is fabricated of a plastic such as Delrin, which is manufactured by Dupont, Inc., Delaware.  FIG. 3  shows a perspective view of the nozzle core  7  without the nozzle sleeve  8  in place. When assembled the nozzle sleeve  8  covers a portion of the nozzle core and is held in place by solely mechanical means. 
         [0021]      FIGS. 4 and 5  show side views of the nozzle core  7  and the nozzle sleeve  8 , respectively, and  FIGS. 6-8  show cross sectional views, through a central axis of the nozzle core, the nozzle sleeve, and the nozzle assembly. Nozzle core  7  has a substantially constant inner bore  9  extending from an input end  10  to an output end  11 . The length of the nozzle core is sufficient to form a columnar stream of water and in the preferred embodiment the length is about 5-10 times the diameter of the inner bore  9 . At an outer surface of the nozzle core, at input end  10 , means such as threads  12  are provided for connecting the nozzle core to a high-pressure water supply. Means for tightening the nozzle core to the high-pressure water supply, preferably hexagonally arranged flat surfaces  13  for applying a wrench, are provided along the length of the nozzle core. At the output end  11  of the nozzle core, the outer surface is preferably cylindrical in shape and dimensioned to accept an inner bore of nozzle sleeve  8 . The dimensional relationship between the outer sleeve of the nozzle core and the inner bore of the nozzle sleeve is discussed below. The outer surface of the output end  11  of the nozzle core is substantially uniform in diameter except for a ridge  14  extending circumferentially around the outer surface at a point along the length of the uniform diameter portion. As discussed later, the ridge engages a complimentary groove of the nozzle sleeve, to hold the two components together when the nozzle assembly is assembled. The thickness of the walls of the output end portion of the nozzle core preferably is between 0.10 and 0.15 inches. 
         [0022]    Referring to  FIGS. 7 and 8 , nozzle sleeve  8  has an inner bore  15  at an output end  16  the inner diameter of which substantially matches the inner bore  9  of the nozzle core  7 . Adjacent to inner bore  15 , in an axial direction toward an input end  17 , a central portion having a substantially constant inner bore  18  is provided for insertion of output end portion  11  of the nozzle core. Inner bore  18  is dimensioned to have an inner diameter of about 1-2 mils greater than the outer diameter of the nozzle core at the output end  11 . The nozzle sleeve preferably can easily slide over the nozzle core at this portion until a ridge  14  of the nozzle core is reached. When the nozzle sleeve  8  is fully engaged with the nozzle core  7 , ridge  14  engages with groove  19  of the nozzle sleeve. In the preferred embodiment an outer diameter of ridge  14  is about 5-10 mils less than an outer diameter of groove  19 . The remaining portion  20  of the nozzle sleeve, that is the portion at input end  17 , has a constant bore of a diameter which will hold the nozzle sleeve  8  in place on the nozzle core  7  when the nozzle assembly is in use and high-pressure water is flowing through it. In the preferred embodiment the diameter of portion  20  is about 5-10 mils less than the outer diameter of ridge  14  of the nozzle core. In view of the portion  20  being a smaller diameter than the outer diameter of ridge  14 , a substantial pressing force is required to assemble the nozzle assembly. A vise or bearing press can be used in the assembly. Although the diameter of the nozzle sleeve bore is less than the diameter of the ridge  14 , in view of the fact that the nozzle sleeve is fabricated of a plastic material, such as Delrin, the nozzle sleeve can deform a small amount to enable the ridge  14  of the nozzle core to pass from entry end  17  of the nozzle sleeve to groove  19 . When ridge  14  is seated in groove  19 , the nozzle sleeve  8  is secured to the nozzle core  7  such that the high-pressure water flowing through the nozzle does not remove the nozzle sleeve from the nozzle core. In the preferred embodiment, groove  19  is at least 0.25 inch from the entry end of the sleeve in order to provide a sufficient length of material in the axial direction for resisting displacement of the ridge  14  from the groove  19 . Also, in order to facilitate assembly of the nozzle core and the nozzle sleeve, the bore in the nozzle sleeve, at the entry end, is chambered at about a 45° angle a distance of about 0.030-0.040 inches as shown at  21 . 
         [0023]    The nozzle assembly is shown assembled in the sectional view of  FIG. 8 . As mentioned above, preferably an inner bore of the nozzle assembly, which includes a portion of the nozzle core and a portion of the nozzle sleeve, is a constant diameter from input end  10  to output end  16 . Although a change in the diameter of the bore of the nozzle assembly is possible in practice of the invention, a reduction in the diameter of the bore for the nozzle assembly should not be made at the point at which the nozzle core meets the nozzle sleeve, as a force from the high-pressure water against a step resulting from a decrease in diameter could result in the nozzle sleeve being forced from the nozzle core by the pressure of the water. 
         [0024]    As shown in  FIG. 8  the nozzle sleeve  8  is dimensioned in the axial direction such that the output end  11  of the nozzle core makes contact with step  22  formed by the change in bore diameter of the nozzle sleeve  8  and the input end  17  of the nozzle sleeve  8  makes contact with an edge of the hexagonally arranged flat surfaces  13 . 
         [0025]    An outer surface  23  of the nozzle sleeve  8 , which contacts a portion of a heat exchanger tube near the heat exchanger tube sheet during the cleaning process, is tapered at an angle of about 5-10° in relation to the central axis  9  as best viewed in  FIG. 7 . 
         [0026]    In order to facilitate removal of the nozzle sleeve  8  from the nozzle core  7 , recesses  24 , as best shown in  FIG. 3 , are provided for insertion of a tool to move the nozzle sleeve  8  axially along the nozzle core  7 . 
         [0027]    While specific materials, dimensional data, and the like have been set forth for purposes of describing embodiments of the invention, various modifications can be resorted to, in light of the above teachings, without departing from Applicant&#39;s novel contributions; therefore in determining the scope of the present invention, reference shall be made to the appended claims.