Abstract:
A conduit length adjustment apparatus having first and second housings each having a member structured to engage the respective housing with a first conduit. A housing movement device is connected between the first and second housings and configured to change a distance between the first and second housings. Selective operation of the members and housing movement device causes the first conduit to move into or out of a second conduit.

Description:
BACKGROUND 
       [0001]    1. Field 
         [0002]    The present invention relates generally to conduit length adjustment apparatuses for steam generators and more particularly to a conduit length adjustment apparatus between a probe pusher and a steam generator tube sheet in a steam generator. 
         [0003]    2. Related Art 
         [0004]    Pressurized water nuclear reactors employ steam generators to isolate and place a radioactive coolant, flowing in a primary circulation loop, in heat exchange relationship with a secondary fluid flowing in a secondary circulation loop. Steam is generated from the secondary fluid. The steam generally is employed to drive a turbine to perform work, e.g., an electric generator. In the primary loop the reactor coolant is heated by the nuclear reactions occurring in the reactor core and circulated through a hot piping leg to a hemispherical bowl shaped portion of the primary side of the steam generator generally known as the channel head. The channel head is separated, by a partition across its diameter, into inlet and outlet plenums, which are covered by a tube sheet through which the terminating ends of U-shaped heat exchanger tubes are fastened. Each of the U-shaped heat exchanger tubes originate in a bore in the tube sheet passing from the inlet plenum of the channel head and terminate in a bore in the tube sheet that communicates with the outlet plenum of the channel head. A cylindrically shaped secondary side of the steam generator is disposed around and over the tube sheet and the U-shaped heat transfer tubes. Hot, radioactive water from the reactor core circulates through the primary side of the steam generator, while non-radioactive water is introduced into the secondary side. The tube sheet and heat exchanger tubes hydraulically isolate but thermally connect the primary side to the secondary side. Hot radioactive water from the primary side flows through the interior of these heat exchanger tubes while the exterior of these tubes come into contact with the non-radioactive water in the secondary side in order to generate nonradioactive steam. 
         [0005]    In the secondary side of the steam generator exterior portions of the U-shaped heat exchanger tubes are supported by and extend through bores present in a plurality of horizontally supported plates that are vertically spaced along the elongated length of the tubes. Small annual spaces are present between the heat exchanger tubes and the bores in the support plates, and the tube sheet, which are known in the art as “crevice regions.” Such crevice regions provide only a very limited flow path for the feed water that circulates throughout the secondary side of the steam generator, which causes “dry boiling” to occur wherein the feed water boils so rapidly that these regions can actually dry out during operation of the steam generator. This chronic drying out causes impurities in the water to precipitate and collect in these crevice regions. These precipitates ultimately create sludge and other debris that promotes the occurrence of corrosion in the crevice regions which, if not repaired, can ultimately cause the tube to crack and to allow radioactive water from the primary side to contaminate the non-radioactive water in the secondary side of the steam generator. 
         [0006]    Eddy current probe systems are employed to monitor the extent of degradation in the walls of the heat exchanger tubes that result from corrosion. One such system is described in U.S. Pat. No. 5,174,165 issued Dec. 29, 1992 to the assignee hereof. One of the services performed at a nuclear power plant is eddy current inspection of the steam generator tubing using such a system. The inspection involves insertion and removal of various configurations of eddy current probes in the high radiation and contaminated area of a nuclear steam generator. Minimizing personal time and equipment near the manway opening through which access to the interior of the steam generator is obtained (generally referred to as the steam generator platform) is highly desirable due to the elevated radiation level in that area. Typically the probes are attached to a long flexible piece of tubing (poly) and driven with a probe pusher through a flexible conduit to an area of interest or the entire length of the steam generated tube. One end of the flexible conduit is generally fixed to the probe pusher while the opposite end is attached to and positioned under the steam generator tube with a robotic manipulator. 
         [0007]    A problem during eddy current inspection is that the amount of conduit in the steam generator needs to be increased or decreased as the robotic manipulator moves to various tube locations. This task is typically accomplished by manually adding or removing sections of the flexible conduit on the steam generator platform, which is a source of radiation exposure time for the field service operators. One method that does not require conduit length change is described in U.S. Pat. No. 6,606,920 issued Aug. 19, 2003 to the assignee hereof U.S. Pat. No. 6,606,920 describes a system in which the probe pusher is mounted to a drive system which enables both the probe pusher and the conduit to reposition during eddy current inspection. While the arrangement described in U.S. Pat. No. 6,606,920 is effective, the amount of working space required to translate the probe pusher is not available at many power plants. 
         [0008]    It is an object of this invention to overcome these difficulties. 
       SUMMARY 
       [0009]    These and other objects are achieved by a conduit length adjustment apparatus including a first conduit, a second conduit, and a conduit length adjustment device. The conduit length adjustment device includes a first housing including a first member structured to selectively engage the first housing with the first conduit, a second housing attached to the second conduit and including a second member structured to selectively engage the second housing with the first conduit, and a housing movement device coupled to the first housing and the second housing. An operation of the housing movement device changes a distance between the first housing and the second housing. When the first housing is engaged with the first conduit, the second housing is disengaged from the first conduit, and the housing movement device is operated, a portion of the first conduit moves into or out of the second conduit. 
         [0010]    The first member and the second member may be bladders. The housing movement device may be a piston. The piston may be annular and disposed around the first conduit. The first housing and the second housing may be annular and disposed around the first conduit. In one embodiment, when the first housing is disengaged from the first conduit, the second housing is engaged with the first conduit, and the housing movement device is operated, the first conduit does not move with respect to the second conduit. In one embodiment, when the first housing is engaged with the first conduit and the second housing is engaged with the first conduit, the first conduit does not move with respect to the second conduit. In one embodiment, the conduit length adjustment device includes a first port configured to receive pressure to operate the first member to selectively engage the first housing with the first conduit, a second port configured to receive pressure to operate the second member to selectively engage the second housing with the first conduit, a third port configured to receive pressure to operate the housing movement device to increase the distance between the first housing and the second housing, and a fourth port configured to receive pressure to operate the housing movement to decrease the distance between the first housing and the second housing, wherein the first port, the second port, the third port, and the fourth port are axially aligned. The first conduit and the second conduit may include flexible tubing. 
         [0011]    Features and utilities of the present inventive concept may also be realized by a steam generator tube inspection system including a robotic manipulator configured to move a conduit to a selected steam generator tube, a probe pusher connected to the conduit and configured to feed a probe through the conduit to the selected steam generator tube, and a conduit length adjustment apparatus. The conduit length adjustment apparatus is disposed along the conduit between the robotic manipulator and the probe pusher. The conduit length adjustment apparatus includes a first conduit, a second conduit, and a conduit length adjustment device. The conduit length adjustment device includes a first housing including a first member structured to selectively engage the first housing with the first conduit, a second housing attached to the second conduit and including a second member structured to selectively engage the second housing with the first conduit, and a housing movement device coupled to the first housing and the second housing. An operation of the housing movement device changes a distance between the first housing and the second housing. When the first housing is engaged with the first conduit, the second housing is disengaged from the first conduit, and the housing movement device is operated, a portion of the first conduit moves into or out of the second conduit. 
         [0012]    Features and utilities of the present inventive concept may also be realized by a method for adjusting a length of a conduit in a steam generator tube inspection system. The method includes providing a conduit length adjustment apparatus between a probe pusher and a steam generator tube sheet. The conduit length adjustment apparatus includes a first housing including a first member structured to selectively engage the first housing with the first conduit, a second housing attached to the second conduit and including a second member structured to selectively engage the second housing with the first conduit, and a housing movement device coupled to the first housing and the second housing. An operation of the housing movement device changes a distance between the first housing and the second housing. The method further includes engaging the first housing with the first conduit, disengaging the second housing from the first conduit, and while the first housing is engaged with the first conduit and the second housing is disengaged from the first conduit, operating the housing movement device to move the first conduit into or out of the second conduit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    A further understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which: 
           [0014]      FIG. 1  is a cross sectional view of the inlet side of the steam generator channel head with the conduit length adjustment apparatus installed between the probe pusher and steam generator tube according to an embodiment of the invention; 
           [0015]      FIG. 2  is a cross sectional view of a conduit length adjustment assembly according to an embodiment of the invention; 
           [0016]      FIG. 3  is a cross sectional view of the conduit length adjustment apparatus according to an embodiment of the invention; and 
           [0017]      FIG. 4  is a cross sectional view of a conduit length adjustment apparatus according to another embodiment of the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]      FIG. 1  is a cross sectional view of the inlet side of a steam generator channel head  2  with a conduit length adjustment device  100  installed between a probe pusher  6  and a steam generator tube  5 . 
         [0019]    The channel head  2  area is defined by the channel head housing  3  and the steam generator tube sheet  4 . The steam generator tubes, such as steam generator tube  5 , are accessed through the steam generator tube sheet  4 . A robotic manipulator  1  is in the channel head  2  and is used to position the conduit  8  near the steam generator tube sheet  4  at a location of a steam generator tube to be inspected. As illustrated in  FIG. 1 , the conduit  8  is positioned at the location of the steam generator tube  5 . The probe pusher  6  pushes an eddy current probe (not shown) through the conduits  7 ,  8 ,  101 , and  102  and into the steam generator tube  5  to be inspected. 
         [0020]    As illustrated in  FIG. 1 , the conduit between the probe pusher  6  and steam generator sheet  4  is composed of four conduits  7 ,  8 ,  101 , and  102 . One end of conduit  7  is connected to probe pusher  6  and the other end of conduit  7  is connected to conduit  101  by connector  9 . One end of conduit  101  is connected to conduit  7  by connector  9  and the other end of conduit  101  is connected to the conduit length adjustment device  100 . One end of conduit  102  is inserted through the conduit length adjustment device  100  and into conduit  101 . The other end of conduit  102  is connected to conduit  8  by connector  10 . One end of conduit  8  is connected to conduit  102  by connector  10  and the other end of conduit  8  is disposed near the steam generator tube sheet  4  and is manipulated by the robotic manipulator  1  so as to be positioned by the steam generator tube  5  to be inspected. Although connectors  9  and  10  are illustrated as two part connectors with connector portions  9   a,    9   b,    10   a,  and  10   b,  it is contemplated that connectors  9  and  10  may be any type of connector suitable for connecting the conduits. Conduits  7 ,  8 ,  101 , and  102  may each be flexible or rigid conduits. 
         [0021]    Although  FIG. 1  illustrates four conduits  7 ,  8 ,  101 , and  102  between the probe pusher  6  and the steam generator tube sheet  4 , it is appreciated that the present invention is not limited thereto. Any number of conduits greater than two may be included between the probe pusher  6  and the steam generator tube sheet  4 . Additionally, conduits  7  and  8  may be omitted and conduits  101  and  102  may be directly connect to probe pusher  6  and steam generator tube sheet  4  without any intervening conduits. 
         [0022]    The conduit length adjustment device  100  is used to move conduit  102  into conduit  101  and move conduit  102  out of conduit  101 . Moving conduit  102  into conduit  101  shortens the length of conduit between probe pusher  6  and steam generator tube sheet  4  and moving conduit  102  out of conduit  101  increases the length of conduit between probe pusher  6  and steam generator tube sheet  4 . 
         [0023]    Although  FIG. 1  illustrates the conduit length adjustment device  100  inside the channel head  2 , the present invention is not limited thereto. The conduit length adjustment device  100  may be located anywhere between probe pusher  6  and steam generator tube sheet  4 . Additionally, it is contemplated to be within the scope of the invention that any number of conduit length adjustment devices  100  may be located between probe pusher  6  and steam generator tube sheet  4 . Furthermore, it is contemplated that the conduit length adjustment device  100  may be reversed such that the conduit  102  connects to conduit  7  or probe pusher  6  and conduit  101  connects to conduit  8  or robotic manipulator  1  while remaining within the scope of the invention. 
         [0024]      FIG. 2  is a cross sectional view of a conduit length adjustment assembly  50 . The conduit length adjustment assembly  50  includes connector portions  9   a  and  10   a , conduits  101  and  102 , and conduit length adjustment device  100 . In the example embodiment illustrated in  FIG. 2 , connector portion  9   a  is a male connector portion and connector portion  10   a  is a female connector portion. The conduit length adjustment assembly  50  may be inserted as a segment of conduit between the probe pusher  6  and the steam generator tube sheet  4 . The conduit length adjustment assembly  50  may also connect directly to the probe pusher  6  and steam generator tube sheet  4  and serve as the entire conduit between the probe pusher  6  and the steam generator tube sheet  4 . 
         [0025]      FIG. 3  is a cross sectional view of the conduit length adjustment device  100  according to an embodiment of the present invention. As illustrated in  FIG. 3 , one end of the conduit length adjustment device  100  is connected to conduit  101 . Conduit  102  is inserted into the other end of the conduit length adjustment device  100  and continues into conduit  101 . The conduit length adjustment device  100  is used to move conduit  102  into conduit  101  or move conduit  102  out of conduit  101 , as described in more detail below. 
         [0026]    The conduit length adjustment device  100  includes a first bladder housing  105  which includes a first port  104  in fluid communication with a first bladder  103 . When pressure is applied to the first port  104 , the first bladder  103  engages the first bladder housing  105  with conduit  102  so as to hold the first bladder housing  105  at the engaged location on the conduit  102 . The conduit length adjustment device  100  also includes a second bladder housing  116  which includes a second port  115  and a second bladder  114 . When a pressure is applied to the second port  115 , the second bladder  114  engages the second bladder housing  116  with the conduit  102  so as to hold the second bladder housing  116  at the engaged location on the conduit  102 . As employed herein, the statement that a housing is engaged with a conduit shall mean that the positions of the housing and the conduit are fixed with respect to each other. When a housing is disengaged from a conduit, it shall mean that the housing and the conduit can move with respect to each other. 
         [0027]    In the exemplary embodiment illustrated in  FIG. 3 , the first and second bladders  103  and  114  can additionally provide a leak tight pressure boundary. While the exemplary embodiment illustrated in  FIG. 3  includes bladders to engage, it is contemplated that any suitable member may be used to selectively engage the first and second housings  105  and  116  with the conduit  102 . For example and without limitation, solenoids may be used to selectively engage the first and second housings  105  and  116  with the conduit  102 . 
         [0028]    The conduit length adjustment device  100  also includes a piston  107 . In the example embodiment illustrated in  FIG. 3 , the piston  107  is annular and arranged around the conduit  101 . Additionally, the first bladder housing  105  and second bladder housing  116  are annular and arranged around conduit  101 . This arrangement permits a high translation force within a minimum amount of space. However, the present invention is not limited to this arrangement and other arrangements of the piston  107  and housings  105  and  107  are contemplated to be within the scope of the invention. 
         [0029]    Pressure is applied to the piston through port  106  or  108  so as to move the piston  107  in the desired direction. The piston  107  slides along inner housing  111  and the piston&#39;s  107  sliding motion is guided by split bushings  109  and  119 . Wiper  110  helps to prevent contamination of the piston  107  and split bushings  109  and  119 . 
         [0030]    One end of the piston  107  is connected to the second bladder housing  116  so that the movement of the piston  107  changes the distance between the first bladder housing  105  and the second bladder housing  116 . By controlling the engagement and disengagement of the first bladder  103  and the second bladder  114  and the operation of the piston  107 , moving conduit  102  into conduit  101  and moving conduit  102  out of conduit  101  can be controlled. Although the exemplary embodiment shown in  FIG. 3  includes a piston  107 , it is contemplated that any suitable housing movement device may be used to change the distance between the first housing  105  and the second housing  116 . 
         [0031]    The following are exemplary operations of the conduit length adjustment device  100 . To move the conduit  102  out of the conduit  101 , the first bladder  103  is engaged with the first conduit  102 , the second bladder  114  is disengaged from conduit  102 , and the piston  107  is operated to increase the distance between the first bladder housing  105  and the second bladder housing  116 . The second bladder  114  is then disengaged with the conduit  102 , the first bladder  103  is disengaged from the first conduit  102 , and the piston  107  is operated to decrease the distance between the first bladder housing  105 . By repeating this process of engaging and disengaging the first and second bladders  103  and  114  and operating the piston  107 , the conduit  102  can be moved out of conduit  101  by a desired amount, thus increasing the length of the conduit between the probe pusher  6  and the steam generator tube sheet  4  by the desired amount. After the length is adjusted by the desired amount, both the first bladder  103  and the second bladder  114  can be engaged to secure the conduit  102  in place. In an example embodiment, the sequencing of engagement and disengagement of the first and second bladders  103  and  114 , along with operation of the piston  107 , is controlled by an electronic controller, such as, for example and without limitation, a computer, so as to provide efficient operation and prevent the simultaneous release of both the first and second bladders  103  and  114 . 
         [0032]    Similarly, to move the conduit  102  into the conduit  101 , the second bladder  114  is engaged with the conduit  102 , then the first bladder  103  is disengaged from the conduit  102 , and the piston  107  is operated to increase the distance between the first bladder housing  105  and the second bladder housing  116 . The first bladder  103  is then engaged with conduit  102  and the second bladder  114  is disengaged from conduit  102 , then the piston  107  is operated to decrease the distance between the first bladder housing  105  and the second bladder housing  116 . By repeating this process of engaging and disengaging the first and second bladders  103  and  114 , and operating the piston  107 , the conduit  102  can be moved into conduit  101  by a desired amount, thus decreasing the length of the conduit between the probe pusher  6  and the steam generator tube sheet  4  by a desired amount. After the length is adjusted by the desired amount, both the first bladder  103  and the second bladder  114  can be engaged to secure the conduit  102  in place. 
         [0033]    The conduit length adjustment device  100  also includes bushing  113  and shaft  112 . Shaft  112  is slidably connected to bushing  113  and outer housing  117  so as keep port  115  axially aligned with ports  106  and  108 . The conduit length adjustment device  100  can also include shim  118 . A size of the shim  118  can be adjusted so as to change the amount threads of outer housing  117  engage with threads of inner housing  111 , and thereby axially align port  104  with ports  106  and  108 . Axially aligning ports  104 ,  106 ,  108 , and  115  permits an efficient connection to the ports. 
         [0034]      FIG. 4  illustrates a conduit length adjustment apparatus according to another exemplary embodiment of the invention. The conduit length adjustment apparatus includes a first housing  205  and second housing  216 . The first housing  205  includes a first port  204  and a first bladder  203 . The first housing  205  also includes a third port  206  and fourth port  208  which receive pressure to operate the piston  207 . The second housing  216  includes the second bladder  214  and second port  215 . 
         [0035]    The conduit length adjustment apparatus illustrated in  FIG. 4  moves conduit  202  into and out of conduit  201  by selectively engaging and disengaging the first and second bladders  203  and  214  and operating piston  207 , similar to the operation of the conduit length adjustment apparatus described above with respect to  FIGS. 2 and 3 . However, the conduit length adjustment apparatus illustrated in  FIG. 4  differs in that the first housing  205 , second housing  216 , and piston are not annular. Additionally, in the embodiment illustrated in  FIG. 4 , conduit  202  includes a chamfered end which allows easy passage a probe into conduit  202 . It is contemplated that a chamfered end can readily be incorporated into conduit  102  in the embodiment illustrated in  FIG. 1  while remaining within the scope of the invention. 
         [0036]    While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.