Patent Publication Number: US-2006016249-A1

Title: Heat recovery test apparatus and method for making and testing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
      This application claims priority to U.S. Provisional Application No. 60/584,390, filed on Jun. 30, 2004, the contents of which are incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates generally to a test apparatus and method and more specifically to a heat recovery test apparatus and system and a method of making and testing such heat recovery apparatus and system.  
      2. Description of the Prior Art  
      Heat recovery systems are known in the art. One such heat recovery system is often referred to as a heat recovery steam generator (HRSG). HRSGs typically utilize waste heat from a variety of sources such as a combustion gas turbine or the like and convert the same into steam for reuse. HRSGs typically include a vertical header or manifold and a plurality (in some cases 10 or more to as many as 100 or more) horizontally positioned heat exchange tubes or pipes. These tubes or pipes are connected with the header via tube-to-pipe header connections so that the interior of the tubes or pipes communicate with, or are in flow engagement with, the interior of the header. These tubes are normally connected to the header via welding, brazing or the like. An essential step in the manufacture of an HRSG involves the testing of the tube-to-header connections to ensure that there are no leaks. Although the HRSG headers are normally vertically oriented and the tubes or pipes are horizontally oriented, the orientation of the completed panel is dependent on the gas flow in the final assembly and the orientation of the headers is dependent upon the facility and fabrication sequence. Usually, the tubes and pipes are perpendicular to the headers.  
      Conventional HRSG tube-to-header testing utilizes a hydrostatic test. This involves filling the HRSG unit or system with water at high pressure and visually observing whether any leaks exist around the tube-to-header connections. If a leak does exist, it is identified and repaired. This normally requires draining the test water from the system, re-welding the defective tube-to-header connection and then repeating the hydrostatic test as described above. Hydrostatic can be, and often is, conducted on the system during fabrication at the manufacturing facility or after installation at the user&#39;s site, or both.  
      Although hydrostatic testing is the conventional and generally accepted method for testing HRSG tube-to-header connections, numerous limitations exist. One disadvantage of hydrostatic testing is that the use of water within the system “wets” the system and often leads to corrosion when the test is completed and the system is exposed to atmospheric conditions. Further, because of the high water pressures (as high as 2,000 psi or more) needed to conduct a satisfactory hydrostatic test, many of the system drains and/or vents need to be welded shut during the test process, and then opened with a cutting torch when the test is completed. This often introduces impurities into the interior of the system. Still further, a hydrostatic testing system requires significant capital expenditure and has limited portability. In many cases, this limits the ability or increases the costs and time to check a leak in an HRSG system located in the field or at its installation site.  
      Accordingly, there is a need in the art for a heat recovery system test apparatus and a method of making and testing a heat recovery system which overcomes the limitations in the art.  
     SUMMARY OF THE INVENTION  
      The present invention relates to a test apparatus for a heat recovery system and a method for making and testing a heat recovery system which has particular applicability to a heat recovery system commonly referred to as a heat recovery steam generator (HRSG).  
      The test apparatus and methods in accordance with the present invention eliminates the use of a hydrostatic or water pressure test, thus minimizing or eliminating atmospheric corrosion caused by wetting of the system. Further, the test apparatus and methods in accordance with the present invention function at relatively low pressures, thereby eliminating the need to close vents and/or drains in the header by welding and then reopening the same with cutting torch. Still further, the test apparatus and methods in accordance with the present invention provide a test which is extremely sensitive, is highly portable and requires limited capital expenditure and labor to perform.  
      In one embodiment of the present invention, the test apparatus includes a shroud or housing which is positionable around a portion of the header and a portion of the heat exchange tubes, a source of hydrogen, helium or other detectable test gas and a means for detecting the presence of such gas. In this embodiment, the shroud is positioned around a portion of the header and a portion of the tubes whose connections are to be tested. Such positioning forms a gas containment or test chamber. A gas test mechanism is positioned at either the bottom end or the top end of the test chamber, depending upon whether the test gas is heavier or lighter than ambient air, to determine the level of test gas, if any, within such chamber. A further component of the test apparatus is a test member for testing an individual tube-to-header connection. This member includes a shroud or housing which substantially surrounds an individual tube-to-header connection and a means in communication with such shroud or housing to detect the existence of a test gas.  
      The method of testing in accordance with the present invention includes positioning a shroud or housing around a portion of a header and plurality of tube-to-header connections to be tested, introducing hydrogen, helium or some other test gas into the heat recovery system and then testing a sample of air from the interior of the shroud or housing to determine the amount of test gas, if any, within such chamber. If a predetermined level of test gas is detected within the test chamber, it can be concluded that a leak exists and each individual tube-to-header connection (or selected tube-to-header connections) is further tested to isolate the defective tube-to-header connection or connections.  
      The method of making a heat recovery system in accordance with the present invention includes providing a header having a plurality of openings for connecting heat exchange tubes, connecting a plurality of heat exchange tubes to the header in the area of the plurality of openings via welding, brazing, or the like, and then testing the tube-to-header connections for leaks via the test method described above.  
      The above features, structural elements and method steps will become more apparent with reference to the drawings, the description of the preferred embodiment and the appended claims.  
    
    
     DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is an isometric view of the heat recovery portion of a heat recovery steam generator (HRSG) system.  
       FIG. 2  is a top, elevational view, with portions broken away, of one of the headers and a portion of the connected tubes of  FIG. 1 .  
       FIG. 3  is a top, elevational view, with portions broken away, of a shroud surrounding a portion of one of the headers and a plurality of tubes connected thereto.  
       FIG. 4  is a side elevational, fragmentary view of a shroud connected with one of the headers and a plurality of tubes extending therefrom.  
       FIG. 5  is a view, partially in section, as viewed along the section line  5 - 5  of  FIG. 4 .  
       FIG. 6  is a front elevational, fragmentary view of the shroud connected with one of the headers.  
       FIG. 7  is an isometric, fragmentary view of one side portion of the shroud.  
       FIG. 8  is a view, partially in section, showing the relationship of the tube engagement seal of the shroud in  FIG. 7  relative to a plurality of tubes.  
       FIG. 9  is an isometric, fragmentary view of a further embodiment of a shroud in accordance with the present invention.  
       FIG. 10  is a view, partially in section, showing the relationship between a portion of the shroud of  FIG. 9  and the plurality of the tubes.  
       FIG. 11  is a view, partially in section, as viewed along the section line  11 - 11  of  FIG. 5 .  
       FIG. 12  is an isometric view showing connection of an individual tube-to-header connection test member.  
       FIG. 13  is a view, partially in section, as viewed along the section line  13 - 13  of  FIG. 12 .  
       FIG. 14  is a view, partially in section, as viewed along the section line  14 - 14  of  FIG. 13 .  
       FIG. 15  is a view, similar to that of  FIG. 13 , showing the test member being connected to the tube to be tested.  
       FIG. 16  is a schematic view of the test system in accordance with the present invention.  
       FIG. 17  is a view, partially in section, of a further embodiment of an individual tube-to-header connection test unit as shown being used with a center tube.  
       FIG. 18  is a view, partially in section, of the individual connection test unit of  FIG. 17 , but used with an outer tube.  
       FIG. 19  is an isometric view of the test unit of  FIGS. 17 and 18 .  
       FIG. 20  is an elevational view of a further embodiment of a shroud assembly with the top part removed.  
       FIG. 21  is a view, partially in section, as viewed along the section lines  21 - 21  of  FIG. 20 .  
       FIG. 22  is an elevational top view showing the pair of side panels of the shroud assembly of  FIG. 20 .  
       FIG. 23  is an elevational side view showing one of the side panels and the tube engaging edge thereof.  
       FIG. 24  is an elevational rear view of the tube engaging bladder of the shroud assembly of  FIG. 20 .  
       FIG. 25  is an elevational top view of the bladder shown in  FIG. 24 .  
       FIG. 26  is a view, partially in section, as viewed along the section line  26 - 26  of  FIG. 24 . 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT AND METHOD  
      The present invention is directed to a test apparatus for a heat recovery system and a method of making and testing a heat recovery system. More specifically, the invention is directed to a test apparatus for a heat exchanger portion of a heat recovery system and a method of making and testing such heat exchanger portion. Although the present invention is useful for a variety of heat recovery systems with different structures, it has particular applicability to a heat recovery system commonly referred to as a heat recovery steam generator (HRSG) and in particular a heat exchange component or panel of such HRSG. Accordingly, the description of the preferred embodiment and methods will be described with reference to an HRSG.  
      With reference to  FIG. 1 , an HRSG system typically includes one or more heat recovery or heat exchange units or panels  10 . Each of these units  10  includes a pair of headers or manifolds  11 , 11  and an array or plurality of tubes  12  extending between the headers  11 , 11 . When the units  10  are installed and when the units  10  are tested during fabrication, these headers  11 , 11  are generally vertically positioned, with the array of tubes  12  extending horizontally between the headers  11 , 11 . The headers  11 , 11  have a hollow interior and closed ends. As known in the art, an HRSG system may be installed as a panelized design in which the panels  10  are individually installed, as a module design in which modules comprised of two or more panels are installed as a unit and C-panel design in which panels are supported and installed as part of a generally C-shaped frame structure.  
      As shown in  FIG. 2 , the individual tubes  18 ,  19 ,  20  within the array of tubes  12  are connected to openings in the walls of the headers  11 , 11  via welding, brazing or the like  16  so that the hollow interior of the tubes are in communication with the hollow interior of the headers. During use, a heat exchange (or cooling) fluid or medium flows through the tubes  18 ,  19 ,  20  from one header  11  to the other  11  and from one unit  10  to the other  10 , if desired. The tubes within the array  12  may include a series of laterally spaced tubes  18 ,  19  and  20  in a horizontal plane or a series of tubes or tube clusters which are staggered from one another.  
      One step in the manufacture or fabrication of a heat exchange or recovery unit or panel  10 , such as that shown in  FIG. 1 , or after the installation of the panel and before use, involves the testing of the tube-to-header connections between the individual tubes in the array  12  to the headers  11  to ensure that the connections are tight and no leaks exist.  
      Each of the headers  11  may include one or more vents  14  or drains  15 . Further, each of the units  10 , if desired, may embody flow conduits to facilitate flow of the heat exchange or cooling medium between adjacent units  10 . At least one of the units  10  within each heat recovery system also includes a heat exchange or cooling medium inlet and a heat exchange or cooling medium outlet.  
      Reference is next made to  FIGS. 3, 4 ,  5 ,  6  and  7  showing various views or portions of a test shroud or housing  21  connected with a portion of the header  11  and a portion of the tubes in the area of the tube-to-header connections being tested. As will be described below, the shroud  21  forms a test chamber or test gas flow chamber  17  surrounding the tube-to-header connections to be tested. The shroud  21  includes a pair of side walls  22  and  24 , a pair of top wall sections  23  and  25  and a pair of front wall sections  26  and  27 . Each of the side walls  22  and  24  is an elongated structure having a length which preferably at least approximates the height of the header  11 . Each of the side walls  22 ,  24  includes a header seal  30  and a tube seal  31 . As shown best in  FIGS. 5 and 6 , the header seal  30  is formed on an inner surface portion along the front edge  28  of each side wall  22  and  24  and extends substantially the entire length of the side walls  22  and  24 . When assembled for use, the header seal  30  engages an outer surface portion of the header  11  as shown in  FIGS. 5 and 6 .  
      The tube seal  31  is formed on an inner surface of the rearward edge  29  of each of the side walls  22  and  24  and extends substantially the entire length of the side walls  22  and  24 . During use, the tube seal  31  engages surface portions of each of the outer tubes  18  and  20  as shown in  FIGS. 3, 5  and  8 .  
      The seals  30  and  31  can be constructed of a variety of seal materials. In the preferred embodiment, however, the seals  30  and  31  are constructed of a soft rubber or rubber-type synthetic material. The side walls  22  and  24  may also be constructed from a variety of materials such as various metals and plastics. In the preferred embodiment, however, the side walls  22  and  24  are constructed of sheet metal.  
      The top portion of the shroud  21  includes the top wall sections  23  and  25  ( FIGS. 3 and 4 ) and the front wall sections  26  and  27  ( FIGS. 4 and 6 ). The top wall section  25  is connected with the side wall  22  along the top edge of the side wall  22  and the top wall section  23  is connected with the side wall  22  along the top edge of the side wall  24 . When the shroud  21  is connected with the header  11  and tube array  12 , the tube wall sections  23  and  25  are joined to one another by a latch member  32 .  
      With reference to  FIG. 6 , the front wall section  27  is connected with an upper portion of the side wall  22  along its front edge  28  and a portion of the top wall section  25 . The front wall section  26  is connected with an upper portion of the side wall  24  along its front edge  28  and a portion of the top wall section  23 . As shown, the inner edges of the front wall sections  26  and  27  are intended to be joined together and retained in that position by a latch member  34 . When the shroud  21  is in its assembled form and ready for use, the bottom edges of the wall sections  26  and  27  rest on or engage the top surface of the header  11 . If desired, the upper portion of the shroud  21  can be provided with similar rear wall sections (not shown) which are also connected with a latch member and which assist in defining and isolating the test chamber  17  within the shroud  21 .  
      One embodiment of the tube seal member  31  is shown in  FIGS. 7 and 8 . In this embodiment, the tube seal member  31  comprises an elongated seal member  31  having an inner seal edge  35  for engaging a peripheral surface portion of the outer tubes  18  and  20  in the tube array  12  of  FIGS. 2, 3  and  5 . A further embodiment of a tube seal member is illustrated in  FIGS. 9 and 10  by the reference character  36 . This seal member  36  includes a plurality of concave portions with a seal edge  38  for engagement with a peripheral portion of the outer tubes  18  and  20  and an intermediate portion  39  which extends at least partially between adjacent outer tubes  18  and adjacent outer tubes  20 .  
      If desired, and as shown best in  FIGS. 5 and 11 , the area or space between the outer tubes  18  and  20  and the inner tube  19  may be partially sealed by a pair of hanging seal members  40 . Such seal members  40  extend from near the upper end of the shroud  21  to the lower or bottom end of the shroud  21 , and are positioned between the tubes  18  and  19  and between the tubes  19 ,  20 . If provided, these hanging seals  40  are flexible so that they can be rolled up when not in use or allowed to hang as shown best in  FIG. 11  when in use. When in use, the hanging seal members  40  assist in defining the test chamber  17 .  
      It should be noted that the header seals  30  do not need to form a perfect airtight seal with the side walls of the header  11 , nor do the tube seals  31  need to form a perfect airtight seal with the outer tubes  18  and  20 . Further, the shroud may or may not include the hanging seals  40 . As discussed below, this all depends on the specific test gas being used, the amount of the test gas which occurs naturally in the ambient atmosphere and the sensitivity of the testing apparatus for such test gas. If the test gas is the preferred test gas hydrogen or helium which can be detected and measured at extremely low concentrations and is naturally present in the ambient atmosphere at a lever where a deviation from that level can be readily detected, the hanging seal members  40  can be eliminated, if desired. All that is needed is for the shroud to roughly define a test chamber  17  which will confine at least a portion of the test gas (assuming a leak) and allow it to rise to the top of the shroud  21  for detection.  
      As shown best in  FIGS. 3, 4  and  6 , the top wall section  25  is provided with a test gas detection tube  41  which is connected to the wall section  25  via the fitting  42 . The tube  41  extends to and is connected to a test instrument  44  which is capable of detecting the presence of the test gas in a quantity that would indicate a leak in one of the tube-to-header connections. When the preferred test gas is hydrogen or a diluted form of hydrogen such as a non-flammable combination of hydrogen and nitrogen, the test instrument  44  may be any one of a variety of available microelectric hydrogen sensors. When the preferred test gas is helium (He 2 ), the test instrument  44  is a mass spectrometer which is capable of detecting the presence of helium in amounts as little as 1×10 −6  cc/second leak rate. By providing the interior of the header  11  and tubes  12  with test gas at a pressure of about 15 psig or more, a leak in one of the tube-to-header connections will provide test gas at the test instrument well in excess of the level that can be readily detected, thus providing a means for detecting leaks.  
      The test apparatus in accordance with the present invention also includes the individual tube-to-header connection test unit shown in  FIGS. 12-15 . This unit is used if a leak is detected in one or more of the tube-to-header connections. Such unit includes the individual connection test shroud  45 . The shroud  45  is a collar-type structure which, when assembled, comprises a generally cylindrical configuration having a cylindrical outer wall portion  46  and an annular wall portion  48  which are connected with one another at the corner  49 . The end of the cylindrical wall portion  46  opposite to the corner  49  includes a header seal  50  while the edge of the annular wall portion  48  opposite to the corner  49  includes a tube seal  51 . As shown best in  FIG. 15 , the test member  45  is hinged at the point  52  to allow the test member  45  to be positioned around one of the tubes  18 ,  19 ,  20  when being tested, and to be removed when the testing is complete. When in use, the shroud  45  forms a test chamber  47  around an individual tube-to-header connection.  
      A top portion of the cylindrical wall  46  is provided with a test gas detection tube  54  which is in communication with the chamber  47 . The opposite end of this tube  54  is connected with a test instrument  44  such as a microelectronic hydrogen sensor, a mass spectrometer or other gas test instrument as described above. To use the test member  45 , the cylinder wall  46  is opened along the hinge  52 , as shown in  FIG. 15 , positioned around the tube to be tested, and then closed and pressed against the header  11  as shown in  FIGS. 13 and 14 . In this position, the header seal  50  engages the outer surface of the header  11  in the area adjacent to the tube connection and the tube seal  51  engages the outer surface of the tube  18 ,  19 ,  20 . If no test gas is detected after a predetermined period of time, which should be at least 10 minutes, it can be concluded that the tested tube-to-header connection is leak free and the test member  46  is moved to another tube-to-header connection site. This process is repeated until all connections have been tested or until the defective connection or connections have been located.  
      The use of the test apparatus of the present invention and the method aspect of the present invention can be described as follows. First, the shroud  21  is positioned around a portion of the header and tube array connections which are to be tested. The test gas is then introduced into the header and tube array at a pressure which is sufficient to pass through a leak in a tube-to-header connection if such a leak exists and to provide a sufficient amount of test gas to be detected. With hydrogen, helium (He 2 ) or diluted forms thereof as the test gas, the heat exchange system is pressurized with the test gas to a pressure of about 15 psig or more and maintained at that pressure for a period of time which is sufficient to allow the test gas to enter the interior of the header and the entire tube array and, if there is a leak in one or more of the tube-to-header connections, pass through such leak, flow to the top of the shroud  21 , through the tube  42  and to the test instrument  44 . For this occur, the test gas should be maintained at the above pressure for at least about 10 minutes.  
      If there is a leak at one of the tube-to-header connections, the test gas (preferably hydrogen or helium) will flow through the leak and, because both of such gases are lighter than atmospheric air, will rise to the top of the shroud  21  and enter the tube  42 . If needed or desired, a low level vacuum can be applied to the tube  44  to assist in moving the air within the test chamber to the top of the test chamber and through the tube  42  to the test instrument  44 . If a sufficient quantity of the test gas (greater than that present in ambient atmosphere) is detected by the test instrument  44  to indicate a leak in one or more of the tube-to-header connections, a process is initiated to isolate and identify the particular tube-to-header connection or connections which leak. This process involves using the individual tube-to-header connection shroud  45  of  FIGS. 12-15  to test each of the individual tube-to-header connections. An apparatus can also be used, if desired, for testing groups (more than one) of tube-to-header connections such as groups of connections in a lateral or vertical row. Such an apparatus would have a shroud or housing that substantially isolates the group of connections so that any leak in such group can be detected.  
      Alternatively, to assist in isolating the defective tube-to-header connection, the individual test member  45  (or the inlet end of the gas detection tube  54 ) can be positioned within the test chamber at a location between the bottom and top of the shroud  21 . If no test gas is detected after a predetermined period of time at that position, it can be concluded, that the leak does not exist below that point because the preferred test gases (hydrogen or helium) are lighter than air and will rise from the leak. This process can be repeated to narrow the number of individual connections which must be checked.  
      Accordingly, one method in accordance with the present invention is a method for testing a heat recovery system, and more particularly a heat exchange portion of an HRSG (for leaks). This method includes defining a test chamber by positioning a shroud  21  around a portion of the header and tube array to be tested, or otherwise isolating an exterior portion of the header and tube array to be tested. A test gas such as hydrogen or helium is then introduced into the HRSG panel or system at a preselected pressure and for a preselected period of time which will result in the test gas entering the test chamber if a leak exists in one of the tube-to-header connections. A test gas detection instrument, such as a microelectronic hydrogen sensor or a mass spectrometer, is provided to determine whether test gas exists in the test chamber at a sufficient level to indicate a leak. If it does not, it can be concluded that there is no leak. If a leak is detected, each individual tube-to-header connection, or group of tube-to-header connections (within the test area), is individually checked by continuing the introduction of test gas into the system and determining whether the amount of test gas at that connection or at that group of connections, is sufficient to indicate a leak. This is done by using the apparatus of  FIGS. 12-15  to define a test chamber around an individual tube-to-header connection or a similar apparatus to define a test chamber around a group of tube-to-header connections. If no leak is detected at a particular tube-to-header connection or group of tube-to-header connections, the process is repeated for each tube-to-header connection or group of tube-to-header connections. If a leak is detected, the defective tube-to-header connection is re-welded or otherwise repaired and the repaired connection, and preferably also the entire panel or system, is retested.  
      The method of making a heat recovery system and in particular a heat exchange component for a HRSG includes providing a header  11  having a plurality of holes for connection of a plurality of tubes, welding or otherwise connecting a plurality of tubes to such plurality of holes and testing the tube-to-header connections for leaks via the above-described method.  
       FIG. 16  is a schematic diagram showing the present invention. In  FIG. 16 , a source of test gas such as hydrogen, helium or a diluted form thereof is delivered from the reservoir or test gas container  55  via the conduit  56  to an inlet of the heat exchange unit or component  10  whose connections are to be tested. The shroud  21  is positioned over a portion of the unit  10  including the header and a portion of the tube-to-header connections to define a test chamber and the test gas is introduced into the unit  10 . Air within the test chamber defined by the shroud  21  is directed through the conduit or line  41  to the test device  44 . In the preferred embodiment, the test device  44  is a microelectronic hydrogen sensor or a mass spectrometer.  
       FIGS. 17, 18  and  19  show a further embodiment of an individual test member  60  for forming a sealed relationship relative to one of the horizontal tubes  18 ,  19  or  20 , and the header  11  and for defining a test chamber  64 . In this embodiment, the test member  60  is comprised of a relatively flexible, rubber or rubber-type cup-shaped member  61  having an edge  65  for engagement with an exterior surface of the horizontal tube  18 ,  19  or  20  and an opposite edge  66  for engagement with an exterior surface of the header  11 . Preferably, the edge  66  has an edge configuration which conforms to the generally cylindrical exterior surface of the header  11 .  
      As shown, the member  61  is a generally cup-shaped member having a side wall and a slot in such wall which extends from the edge  65  to the edge  66  and which is defined by the edges  68 , 68 . This permits the member  61  to be opened up and slipped over one of the tubes  18 ,  19  or  20  whose connection to the header  11  is to be tested. Specifically, after being positioned over one of the tubes  18 ,  19  or  20 , the two edges  68  are held together manually or via a clamp or connection member and the edges  65  and  66  are held against the exterior surfaces of the tubes  18 ,  19  or  20  and header  11 , respectively. The side wall of the member  61  includes a tube through which the air within the chamber  64  can be directed to a test instrument  44  (as previously described) and tested. As shown in  FIGS. 17 and 18 , the member  61  is sufficiently flexible and pliable so that its configuration can be altered to accommodate either one of the center tubes  19  ( FIG. 17 ) or one of the outer tubes  18 , 20  ( FIG. 18 ).  
      To use the test member  60 , a test gas is introduced into the system, i.e., the tubes and header, and the air within the chamber  64  is tested to determine whether any test gas is detected.  
      Reference is next made generally to  FIGS. 20-26  showing a further embodiment of a shroud assembly for multiple tube-to-header connections, with more specific reference to  FIG. 20 .  FIG. 20  is an elevational view of this further shroud assembly as viewed from the top, with the top or end panel removed. This assembly includes a pair of side panels  69  and  70 , a bladder  71  and a plurality of bungee cords  72 ,  74  or other similar devices for retaining the shroud assembly in operational position relative to the header  11  and the tubes  18 ,  19  and  20 .  
      With continuing reference to  FIG. 20  and further reference to  FIG. 22 , each of the side panels  69  and  70  includes a soft seal member  75  extending along the entirety of one of its edges for engagement with a portion of the outer tubes  18  and  20 . A soft seal member  76  also extends along the entirety of the other edge of each of the side panels  69  and  70  for engagement with the outer surface of the header  11 . Preferably, both of the seal members  75  and  76  are soft seal members constructed of a rubber, rubber-type or foam material to conform in a substantial engaging relationship relative to the tubes  18  and  20  and the surface of the header  11 . As shown in  FIG. 23 , the seal members  75  have concave or scalloped portions  78  (similar to that shown in  FIGS. 9 and 10 ) for engagement with a greater portion of the exterior surfaces of the tubes  18  and  20 . In this embodiment, a test gas sample tube  79  is provided in the side panel  70  near the top. This tube  79  is connected with a test instrument  44  of the type described above.  
      As shown best in  FIG. 20 , the side panels  69  and  70  are connected with the header  11  and with the tubes  18 ,  19  and  20  by a series of bungee cords  72  and  74 . One end of each of the bungee cords  74  is connected with an edge portion of the side panel  69  in the area of the seal  76 , with the other end of the bungee cord extending around the exterior of the header  11  as shown and being connected to the other side panel in the area of the seal  76 . A plurality of these bungee cords  74  are spaced vertically along the header  11  and the side panels  69  and  70 .  
      One end of each of the bungee cords  72  is connected with an edge portion of the side panel  69  in the area of the seal  75 , with the other end extending past the tubes  18 ,  19  and  20  and being connected to the edge of the other side panel  70  in the area of the seal  75 . As with bungee cord  74 , a plurality of these bungee cords  72  are spaced vertically along the tubes  18 ,  19  and  20  and the side panels  69  and  70 .  
      With continuing reference to  FIG. 20  and additional reference to  FIGS. 24, 25  and  26 , the bladder structure  71  is more specifically shown. As shown, the bladder  71  includes a pair of elongated side portions  80  and  81  which are adjacent to one another along their inner edges  87  and which are connected at their tops in the area  84 . Each of the outer edges  77  and  83  of the sides  80  and  81  is provided with a plurality of concave or scalloped portions  85  and are designed to engage an inwardly facing surface portion of the tubes  18  and  20 . Thus, the spacing between the portions  85  correspond to the vertical spacing between the outer tubes  18  and the outer tubes  20 . Further, as shown best in  FIG. 21 , the outer edge portions of the sides  80  and  81  between the concave portions  85  are designed to extend a limited distance between the tubes  18  and  20  and preferably engage corresponding portions of the seal members  75  between the concave portions  78  ( FIG. 23 ).  
      The inner edges  87  of each of the sides  80  and  81  is also provided with a plurality of concave portions  86 . These portions  86  are configured and spaced so that they match up or mate with each other, thereby forming the generally circular openings  88  when positioned next to one another. As shown in  FIG. 21 , these openings  88  are designed to fit around the centrally positioned tubes  19 .  
      The lower ends of the sides  80  and  81  are disconnected from one another to permit the sides  80  and  81  to be inserted between the vertical rows of tubes  20  and  19  and between the vertical rows of tubes  18  and  19 , respectively. This is done by inserting the lower ends of the sides  80  and  81  between the vertical tube sets from the top of a panel to be tested.  
      As shown in  FIG. 26  comprised of a cross-section of the bladder  71 , the bladder  71  is comprised of a pair of bladder walls  89  and  90  which are joined together and sealed at their outer edges  77  and  83  and at their inner edges  87 . These sealed and joined edges  77 ,  83  and  87  follow the configuration of the edges  77 ,  83  and  87  shown in  FIG. 24 , including the concave portions  85  and the concave portions  86 .  
      The bladder  71  is also provided with a filling tube  91  into which air or other fluid can be introduced. This enables the bladder  71  to be selectively inflated so as to further press the sides  80  and  81 , and in particular the concave portions  85  and  86 , into engagement with the surfaces of the tubes  18  and  20  and the tubes  19 , respectively. When installed, the sides  80  and  81  are positioned between the set of tubes  20  and  19  and the set of tubes  19  and  18  in a collapsed or deflated state. Then after installed, air is introduced into the bladder  71  through the tube  91 . This causes engagement between the edges of the sides  80  and  81  and the respective tubes.  
      Although the description of the preferred embodiment has been quite specific, it is contemplated that various modifications could be made without deviating from the spirit of the present invention. Accordingly, it is intended that the scope of the present invention be dictated by the appended claims rather than by the description of the preferred embodiment.