Abstract:
A method for marking a first tube in a shell and tube heat exchanger includes inserting a directional pointer into a second tube and directing the directional pointer toward the first tube.

Description:
This application claims priority from U.S. Patent Application Ser. No. 61/245,079, filed Sep. 23, 2009, which is hereby incorporated herein by reference. 
    
    
     BACKGROUND 
     The present invention relates to shell and tube heat exchangers and, in particular, to an arrangement for marking specific tubes, for example tubes that need to be repaired or otherwise corrected. Shell and tube heat exchangers that are used as chemical reactors may have many thousands of open-ended tubes. Various methods have been used in the past to mark the tubes that need to be corrected. Usually, a marker has been inserted into the open end of the tube that needs to be corrected, but those markers can come loose when people walk on top of the tube sheet, and they require the marker to be removed in order to treat the tube. Also, when the marker is removed in order to correct the tube, the location of the tube may be lost. 
     SUMMARY 
     One embodiment of the present invention provides an arrangement by which one or more directional pointers are inserted into the open ends of one or more tubes adjacent to the tube that needs to be corrected, with the pointers being directed toward the tube that needs to be corrected. The directional pointer may be secured in place by a mechanism that requires the use of a special tool in order to reduce the opportunity for it to be removed accidentally or to be removed by someone who does not have authorization. It also may include an indicator to indicate the type of action that needs to be taken for the tube it is marking. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a broken away, schematic top view of a tube sheet in which a directional pointer has been inserted into a tube adjacent to a tube that requires correction; 
         FIG. 1A  is the same view as  FIG. 1  but with three directional pointers inserted adjacent to a tube that requires correction; 
         FIG. 2  is a front section view of the directional pointer of  FIG. 1  in an expanded condition; 
         FIG. 2A  is a front section view of an alternate embodiment of the directional pointer of  FIG. 2 ; 
         FIG. 2B  is a front section view of two of the directional pointers of  FIG. 2  inserted into tubes in a tubesheet, one directional pointer in an expanded condition and the other in a non-expanded condition; 
         FIG. 3  is a front section view of the directional pointer of  FIG. 2  in a non-expanded condition, before it is inserted into the tube; 
         FIG. 4  is a top view of the toothed plate of the directional pointer of  FIG. 2 ; 
         FIG. 5  is a top view of the rubber cylinder of  FIG. 3 ; 
         FIG. 6  is a top view of an alternate directional pointer plate for the directional pointer of  FIG. 2 ; 
         FIG. 7  is a top view of the directional pointer plate of  FIG. 2 ; 
         FIG. 8  is a top view of another alternative directional pointer plate; 
         FIG. 9  is a top view of another alternative directional pointer plate; 
         FIG. 10  is a top view of another alternative directional pointer plate; 
         FIG. 11  is a top view of another alternative directional pointer plate; 
         FIG. 12  is a top view of the directional pointer plate of  FIG. 7  on an assembled directional pointer; 
         FIG. 13  is a top view of another alternative directional pointer plate; 
         FIG. 14  is a top view of another alternative directional pointer plate; 
         FIG. 15  is a front section view of another alternative directional pointer; 
         FIG. 16  is a bottom view of the directional pointer of  FIG. 15 ; 
         FIG. 17  is a front view of the cap of the directional pointer of  FIG. 15 ; and 
         FIG. 18  is a schematic view showing the directional pointers of  FIG. 15  being used on the bottom of a vertical tube shell and tube heat exchanger. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a broken-away, schematic top view of the top tube sheet  10  of a vertical tube shell and tube heat exchanger, showing a plurality of tubes  12 . In this case, the tube  12 A needs some type of attention. For example, it may have been found in a back pressure test to have a back pressure that is too high or too low, indicating some type of problem with the catalyst loading that needs to be corrected. A directional pointer  14  has been inserted into the tube  12 B, which is adjacent to the tube  12 A that needs to be corrected. That directional pointer  14  includes a directional indicator  16 , pointing to the tube  12 A that needs to be corrected. In this case, the directional indicator  16  is a small hole in the plate  26  that is offset in a radial direction from the longitudinal axis of the plate  26  (which is the same as the longitudinal axis of the directional pointer  14  and of the bolt  18 ). 
     As explained later, especially with respect to  FIGS. 2-2B , it can be seen that the directional pointer  14  is secured in place by the radial expansion of a compressible cylindrical member  21 , which is deformed due to compression exerted by a nut  22  threading up onto a bolt  18 . This causes the cylindrical member  21  to compress in the axial direction and expand in the radial direction. The bolt  18  has a head  18 A with a hexagonal-shaped recess  18 B for receiving an Allen wrench having a hexagonal cross-section. Also, the directional pointer  14  includes a plate  20 , having a diameter that is larger than the inside diameter of the tube  12 B, so the plate  20  rests on the top surface of the tube sheet  10  and prevents the directional pointer  14  from falling into the tube  12 B. All the open tubes  12 ,  12 A,  12 B have the same diameter, and there may be thousands of tubes secured to the tube sheet  10 . 
       FIGS. 2 ,  2 B, and  3  show the directional pointer  14  in more detail.  FIG. 2  and the left side of  FIG. 2B  show the directional pointer  14  in an expanded condition, in which it exerts a radially outwardly-directed force against the inner wall of the tube  12 B. This secures the directional pointer  14  in the tube  12 B.  FIG. 3  and the right side of  FIG. 2B  show the directional pointer  14  in a non-expanded condition, before it has been secured in the tube  12 B. 
     The directional pointer  14  includes a cylindrical compressible member  21  (made of rubber or a flexible, rubbery type of material) defining an axial hole  23  (See also  FIG. 5 ) extending from one end to the other. A cap bolt  18  extends through the axial hole  23  and has a threaded end  18 C onto which a nut  22  has been threaded. As was explained earlier, the head  18 A of the bolt  18  has a hexagonal-shaped recess  18 B (shown in  FIG. 1 ). Between the head of the bolt  18  and the compressible member  21  are a large washer or plate  20 , having an outside diameter that is larger than the inside diameter of the tubes  12  and a directional indicator plate  26 , having an outside diameter that is somewhat less than the outside diameter of the plate  20 . At the other end of the bolt  18  is a toothed plate  28  with upwardly projecting teeth  30  that dig into the compressible member  21 . The nut  22  is fixed to the plate  28  (or alternatively there is sufficient friction between the nut  22  and the bottom surface of the plate  28 ) so the nut  22  does not rotate relative to the plate  28  when the bolt  18  is being rotated, and since the plate  28  digs into the compressible member  21 , the plate and nut also do not rotate relative to the compressible member  21 . This enables the user to tighten the nut  22  up onto the bolt  18  just by rotating the head of the bolt  18 . At first, the loose fit between the bolt  18  and the opening  23  and the mass of the compressible member  21  prevent the compressible member  21  from rotating as the bolt is tightened, and then, as the compressible member  21  moves to its expanded state, in which it presses against the inner wall of the tube  12 , the friction between the compressible member  21  and the inner wall of the tube  12  prevents the compressible member  21  (and the toothed plate  28  and the nut  22 ) from rotating. 
     When the bolt  18  is tightened (threaded into the nut  22 ), it causes the compressible member  21  to shorten axially and expand radially, so it presses against the inner wall of the tube  12 B, causing the directional pointer  14  to be secured within the tube  12 B. 
     If desired, the plate  20  may be secured to the compressible member  21 , which would allow the worker to prevent the compressible member  21  from rotating while he is rotating the bolt  18  simply by holding the plate  20  with one hand as he rotates the bolt  18  with the other hand. 
     The directional indicator plate  26  may have a variety of configurations. It may have a small hole  16  offset from the axis to serve as a directional indicator as shown in  FIGS. 1 ,  7  and  9 . The hole  16  is offset radially from the axis of the directional indicator plate  26 , indicating a direction from the axis to the hole  16  which serves as a pointer that can be used to point toward the tube  12 A that needs correction, as illustrated in  FIG. 1 . Instead of a hole  16 , the directional indicator plate  26 ″ may have a small nick or indentation  16 ″ as shown in  FIG. 8 , or some other reference mark (not shown). 
     The directional indicator plates  26  also may be made in various colors, with each color indicating a different type of condition within the tube  12 A to be corrected. For example, red may indicate that the pressure in the tube was too high, and yellow may indicate that the pressure in the tube was too low, and violet may indicate that the height of catalyst in the tube was too low. 
     Instead of using color to indicate the type of correction that is needed, the directional indicator plate  26 ″ may be textured, as shown in  FIG. 8 , or may have a certain pattern to indicate the type of correction, as shown in  FIG. 9 . 
     The plate  26 ′, shown in  FIG. 6 , does not have a hole to serve as a directional indicator or pointer but instead has markings  24  on its top surface that may serve both as a pointer and as an indication of the type of correction that is needed. Those markings may be engraved, printed, or even hand-applied using a pencil, an indelible pen, a piece of tape, or the like. 
       FIGS. 10 ,  11 ,  13  and  14  show various directional indicator plates  26 A-D that have different shapes to indicate the type of correction that is needed. 
     One example of how these directional pointers  14  may be used is after a vertical tube chemical reactor has been loaded with catalyst and has been pressure tested. These directional pointers  14  may then be installed to indicate which tubes had a back pressure that was too high, which tubes had a back pressure that was too low, which tubes need to be plugged, and so forth. The directional pointers  14  are installed by a person who has the special tool that can fit into the hex recess of the head of the bolt  18 . This tool usually is L-shaped and has a cross-section that matches the hexagonal recess, with both legs of the L being long enough that the tool cannot fall into one of the tubes  12 . Also, the directional pointers  14  are made so they will not come apart so there will be no loose parts that could fall into one of the tubes  12 . 
     When using the directional pointers  14 , the installer installs the directional pointer  14  in a tube  12 B that is adjacent to the tube  12 A that needs to be corrected, and he installs it with the pointer  16  directed toward the tube  12 A that needs correction, so that the tube  12 A becomes the “marked tube”, that is, the tube toward which the pointer on the directional pointer  14  is pointing. He tightens the directional pointer  14  with the special tool so the pointer  16  cannot be rotated relative to the tube  12 B, and the directional pointer  14  cannot be removed from the tube  12 B by someone who does not have authorization to carry one of the special tools. This means that the directional indicator  16  will be directed toward the tube  12 A until an authorized person comes with the special tool to rotate the bolt  18  in the opposite direction, moving the compressible member  21  to a less expanded condition, and allowing the directional pointer  14  to be removed from the tube  12 B. (While a hexagonal recess is shown here, there are various known types of driving arrangements that require special tools that could be used instead, such as star-shaped, and so forth.) 
     The directional pointer  14  would remain in place (such as in tube  12 B in  FIG. 1 ) as the corrections are being made so the person making the corrections does not lose track of the tube  12 A being corrected. Once the corrections are made, the directional pointer  14  may also be used to help a worker find the corrected tubes so they can be re-tested. 
     After the tubes have been corrected and retested, a person with authorization to carry the special tool would then go around and remove the directional pointers  14 . 
     It should be noted that it also would be possible to use the directional pointer  14  to provide further indication of activities that have occurred relating to the marked tube  12 A. For example, a worker may use an indelible pen to mark on top of the plate  26  to indicate that the marked tube has been corrected or that it has been retested. The marking may be a symbol such as a check-mark “√” or a number sign, “#”, a letter, such as “C” for “corrected” and “R” for “retested”, a shape, such as an unfilled-in triangle or a filled-in square, or different colors, such as a blue mark to indicate that a correction has been done and a green mark to indicate that the tube has been retested, or anything else that will tell the workers what has been done to the marked tube. 
     While  FIG. 1  shows the directional pointers  14  being used on the top tube sheet  10  to mark the tops of the tubes  12 , it also may be helpful to mark the bottom of the tubes  12  at the bottom tube sheet  10 B, as shown in  FIG. 18 . In that case, the directional indicator plate  126  may be used in a directional pointer  114  that is otherwise very similar to the directional pointer  14 . This directional indicator plate  126  differs from the original directional indicator plate  26  in that it has a cylindrical shape so it projects axially beyond the washer  20  and therefore can be seen more easily by a worker walking along the ground or on a platform below the reactor. This directional indicator plate  126  also has a hole  116  through the side wall which serves as a directional indicator or pointer. The directional indicator plate  126  may also have identification markings  124  as shown in  FIG. 17  instead of, or in addition to the opening  116 . It also may be made in a color or have a texture or marking or other indication of the type of correction that needs to be made. In general, it may have all the same features as the directional indicator plate that is used on the top of the tubesheet  10 . 
     These directional pointers  114  are inserted into the bottom of the tubes  12 B and point toward the adjacent tubes  12 A that need to be corrected. A flag, streamer, or tag (not shown) may be tied to the directional pointer  114 , for example by threading a streamer through the opening  116 , to make the directional pointer  114  easier to see. The markings  124  may refer to the condition of the tube  12 A to be corrected, or to some other characteristic of interest, such as the location of the tube  12 B or of the tube  12 A to be corrected. 
     Referring back briefly to  FIG. 6 , a line  32  (or some other reference mark) may be added by the user onto the directional indicator plate  26 ′, either before or after the directional pointer  14  has been installed in the tube  12 B. The line  32  may be added to the plate  26 ′ by the user with a pencil, pen, decal, or other mechanism after the directional pointer has been installed and secured in the reactor tube. In this instance, there is no need to align the directional indicator of the directional pointer  14  with the tube  12 A to be corrected before tightening the directional pointer  14 ′ in place, since the line  32  is used instead as the directional indicator and this line  32  can be applied after the directional pointer is installed in the tube  12 B. It also should be noted that it may be desirable for the directional indicator plate  26 ′ to be the same as the plate  20  that rests on the tubesheet rather than using a separate plate. 
     It will be obvious to those skilled in the art that modifications may be made to the embodiments described above without departing from the scope of the present invention.