Patent Publication Number: US-2015059177-A1

Title: Method for removing an end cap of a combustor cap assembly

Description:
FIELD OF THE INVENTION 
     The present invention generally involves a cap assembly of a gas turbine combustor. More specifically, the invention relates to a method for removing an end cap assembly from the cap assembly for repair or replacement. 
     BACKGROUND OF THE INVENTION 
     In particular gas turbine designs, a combustion section includes an outer casing and a plurality of combustors that is arranged in an annular array around the outer casing. Each combustor includes an end cover that is coupled to the outer casing and one or more axially extending fuel nozzles that extend inward from the end cover within the outer casing. Each combustor may also include an annular cap assembly that extends radially, circumferentially and axially within the outer casing. The fuel nozzles extend at least partially through one or more fuel nozzle passages that are defined within the cap assembly. The cap assembly may provide radial support for the fuel nozzles and/or may provide for mitigation of combustion dynamics. 
     A conventional cap assembly includes an outer barrel, an inner barrel assembly that is rigidly connected to the outer barrel, and an end cap assembly that is inserted into one end of the inner barrel assembly. The end cap assembly typically comprises an outer ring, a cap plate or effusion plate that extends radially and circumferentially around one end of the outer ring, and one or more axially extending fuel nozzle collars that each at least partially define the fuel nozzle passages of the cap assembly. A compression seal such as a spring or hula seal circumferentially surrounds the ring. 
     During assembly, the end cap assembly is pressed into the inner barrel assembly. The compression springs provide radial support to the end cap assembly and also may allow for thermal growth and/or relative movement between the inner barrel assembly and the end cap assembly during operation of the combustor. One or more mechanical fasteners such as rivets or bolts may extend between the inner barrel assembly and the ring of the end cap assembly to hold the end cap assembly in position. Over time, oxidation, thermal cycling and/or combustion dynamics may cause weakening and/or damage to the cap plate. As a result, the cap assembly must be removed from the combustor and the cap plate must be repaired or replaced. 
     Current methods for removing the end cap assembly from the inner barrel require disassembly of a major portion of the cap assembly. This process is complex and time consuming In addition, known methods for removing the end cap assembly potentially result in damage such as deformation to or perforation of the cap plate, thus substantially increasing repair time and costs. Therefore, an improved method for removing the end cap assembly from the inner barrel which reduces repair time and decreases the potential for damage to the cap plate would be useful. 
     BRIEF DESCRIPTION OF THE INVENTION 
     Aspects and advantages of the invention are set forth below in the following description, or may be obvious from the description, or may be learned through practice of the invention. 
     One embodiment of the present invention is a method for removing an end cap assembly from a combustor cap assembly. The method includes inserting a push rod through an opening in a back plate portion of the cap assembly, engaging one end of the push rod with a radial support feature of the end cap assembly and applying a force to the push rod. 
     Another embodiment of the present invention is a method for removing an end cap assembly from a combustor cap assembly. The method comprises inserting a plurality of push rods through a plurality of corresponding openings defined in a back plate of the cap assembly, engaging one end of each push rod with a radial support feature of the end cap assembly, mounting the cap assembly within a press and applying a force to the push rods via the press. 
     Another embodiment of the present invention includes a method for separating an end cap assembly from an inner barrel of a combustor cap assembly. The method comprises removing a plurality of mechanical fasteners that extend between the inner barrel and the end cap assembly, inserting a plurality of push rods through a corresponding plurality of openings defined within one or more retention plates of the cap assembly, engaging one end of each push rod with a radial support feature of the end cap assembly, positioning an outer barrel portion of the cap assembly atop one or more vertical supports and applying a force to the push rods. 
     Those of ordinary skill in the art will better appreciate the features and aspects of such embodiments, and others, upon review of the specification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A full and enabling disclosure of the present invention, including the best mode thereof to one skilled in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying figures, in which: 
         FIG. 1  illustrates a perspective view of an exemplary cap assembly as may be found in a conventional combustor of a turbo-machine such as a gas turbine; 
         FIG. 2  illustrates an exploded perspective view of the cap assembly as shown in  FIG. 1 ; 
         FIG. 3  provides a perspective view of a backside of an end cap assembly according to one embodiment of the present invention; 
         FIG. 3  provides a perspective view of a backside of an end cap assembly of the cap assembly as shown in  FIGS. 1 and 2 ; 
         FIG. 4  provides an enlarged partial back side view of the cap assembly as shown in  FIG. 1 , according to one embodiment of the present invention; 
         FIG. 5  provides an assembled perspective view of the back side of the cap assembly as shown in  FIG. 2 , according to one embodiment of the present invention; 
         FIG. 6  provides a perspective cutaway view of the cap assembly as shown in  FIG. 5 ; 
         FIG. 7  provides a perspective cutaway view of the cap assembly as shown in  FIG. 6 , according to one embodiment of the present invention; 
         FIG. 8  provides a perspective cutaway view of the cap assembly as shown in  FIG. 6 , according to one embodiment of the present invention; 
         FIG. 9  provides a perspective view of the cap assembly as shown in  FIG. 8 , according to one embodiment of the present invention; 
         FIG. 10  provides a perspective view of a push rod connected to an alignment plate according to one embodiment of the present invention; 
         FIG. 11  provides a perspective cutaway view of the cap assembly including the push rods and the alignment plate as shown in  FIG. 10 , according one embodiment of the present invention; 
         FIG. 12  provides a perspective cutaway view of the cap assembly as shown in  FIG. 1 , according to one embodiment of the present invention; 
         FIG. 13  provides a perspective view of a cap assembly mounted in an exemplary press, according to one embodiment of the present invention; 
         FIG. 14  illustrates a method for loosening and/or removing the end cap assembly from the cap assembly according to an exemplary embodiment of the present subject matter; 
         FIG. 15  illustrates a method for loosening and/or removing the end cap assembly from the cap assembly according to an exemplary embodiment of the present subject matter; and 
         FIG. 16  illustrates a method for loosening and/or removing the end cap assembly from the cap assembly according to an exemplary embodiment of the present subject matter. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to present embodiments of the invention, one or more examples of which are illustrated in the accompanying drawings. The detailed description uses numerical and letter designations to refer to features in the drawings. Like or similar designations in the drawings and description have been used to refer to like or similar parts of the invention. As used herein, the term “radially” refers to the relative direction that is substantially perpendicular to an axial centerline of a particular component, and the term “axially” refers to the relative direction that is substantially parallel to an axial centerline of a particular component. 
     Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that modifications and variations can be made in the present invention without departing from the scope or spirit thereof. For instance, features or steps illustrated or described as part of one embodiment may be used on another embodiment or in another step to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents. 
     Certain gas turbine combustors include one or more axially extending fuel nozzles that extend downstream from an end cover. The fuel nozzles are cantilevered to the end cover at one end and extend at least partially through a cap assembly that is disposed within the combustor. The cap assembly extends radially, circumferentially and axially within the combustor. Typically, the cap assembly provides radial support to the cantilevered fuel nozzles and may also help control combustion dynamics within the combustor. An exemplary cap assembly may include multiple subassemblies including an outer barrel assembly, an inner barrel assembly and an end cap assembly which includes a cap plate. The end cap assembly is positioned generally adjacent to an outlet end of the fuel nozzles. 
     In operation, fuel is injected into the combustor from the outlet end of the fuel nozzle where it is mixed with air and burned proximate to the cap plate of the end cap assembly. As a result, the cap plate is exposed to high thermal stresses caused by the combustion flame. In addition, the cap plate may be exposed to large mechanical stresses typically caused by combustor dynamics. Consequently, the cap plate may develop cracks or other damage which requires repair or replacement of the component. In order to repair the cap plate, the end cap assembly must be removed from the cap assembly. However, various factors such as oxidation and/or material deformation create challenges to separating the end cap assembly from the cap assembly without damaging the cap plate. Therefore, an improved method for removing the end cap assembly from the cap assembly and/or the inner barrel assembly which avoids damage to the cap plate is provided herein. 
     Referring now to the drawings, wherein like numerals refer to like components,  FIG. 1  illustrates a perspective view of an exemplary cap assembly  10  as may be found in a conventional combustor of a turbo-machine such as a gas turbine, and  FIG. 2  provides an exploded perspective view of the cap assembly  10  as shown in  FIG. 1 . As shown in  FIGS. 1 and 2 , the cap assembly  10  generally includes an outer barrel  12 , an inner barrel assembly  14  that is rigidly connected to the outer barrel  12  via one or more struts  16 , and an end cap assembly  18  that is inserted into a forward end portion  20  of the inner barrel assembly  14 . The outer barrel  12  is typically coupled to an outer casing (not shown) that surrounds the combustor. 
       FIG. 3  provides a perspective view of a backside of the end cap assembly  18  as shown in  FIGS. 1 and 2 . As shown in  FIGS. 2 and 3 , the end cap assembly  18  generally includes an outer ring or band  22 . As shown in  FIGS. 1 and 2 , a cap plate or effusion plate  24  extends radially and circumferentially around one end of the outer band  22 . The cap plate  24  may at least partially define a plurality of cooling passages (not shown). In particular designs, as shown in  FIGS. 1 and 2  the cap plate  24  at least partially defines one or more fuel nozzle passages  26 . As shown in  FIGS. 1 ,  2  and  3 , the end cap assembly  18  may further include one or more fuel nozzle sleeves  28 . As shown in  FIGS. 1 and 2 , the fuel nozzle sleeves  28  are substantially coaxially aligned with the one or more fuel nozzle passages  26 . 
     As shown in  FIG. 2 , a compression seal  30  such as a spring or hula seal circumferentially surrounds the outer band  22 . Generally, the compression seal  30  provides radial support for the end cap assembly  18  during and/or after insertion into the end portion  20  of the inner barrel assembly  14  while allowing for relative movement and/or thermal growth between the end cap assembly  18  and the inner barrel assembly  14  during operation of the combustor. 
     As shown in  FIG. 2 , a plurality of radially extending retention holes  32  may be defined in the outer band  22 . The retention holes  32  may generally align with a plurality of complementary retention holes  34  ( FIG. 1 ) defined by an outer ring  36  of the inner barrel assembly  14 . As shown in  FIGS. 1 and 2 , a plurality of mechanical fasteners  38  such as rivets or bolts may be inserted through the retention holes  32 ,  34  ( FIG. 1 ) so as to fix the end cap assembly  18  to the inner barrel assembly  14 . 
     In particular embodiments, as shown in  FIG. 3 , the end cap assembly  18  includes a radial support feature  40 . In one embodiment, the radial support feature  40  includes an inner ring  42  and a plurality of support members or arms  44  that extend radially between the inner ring  42  and the outer band  22 . In particular configurations, the support members  44  extend between the inner ring  42  and an outer ring  46  that is disposed along an inside wall of the outer band  22 . The support members  44  may be disposed between adjacent fuel nozzle sleeves  28 . The radial support feature  40  generally provides structural support to the end cap assembly  18  to prevent and/or reduce undesirable deformation of the end cap assembly  18  during operation of the combustor. 
     Referring back to  FIG. 2 , the cap assembly  10  includes a back plate  48  and a plurality of fuel nozzle collars  50  that extend through the back plate  48 . The fuel nozzle collars  50  are substantially coaxially aligned with the fuel nozzle sleeves  28  of the end cap assembly  18 . In particular designs, one or more retention plates  52  may be bolted, welded or otherwise mechanically connected to the back plate  48  to hold the fuel nozzle collars  50  in position. In other designs, the back plate  48  may hold the fuel nozzle collars  50  in position. 
     As shown in  FIG. 2 , one or more openings  54  may extend through each or some of the retention plates  52  and/or through the back plate  48 . The openings  54  may be provided prior to assembly of the cap assembly  10 . In other embodiments, the openings  54  may be machined, cut or formed in each or some of the retention plates  52  and/or the back plate  48  post assembly of the cap assembly  10  so as to facilitate disassembly of the cap assembly  10 . 
       FIG. 4  provides an enlarged partial view of the back side of the cap assembly  10  according to one embodiment, and  FIG. 5  provides an assembled perspective view of the backside of the cap assembly  10  as shown in  FIG. 2 , according to one embodiment of the present invention. As shown in  FIG. 4 , at least some of the openings  54  may include threads  55 . The threads  55  may be cut into the one or both of the retention plates  52  and/or the back plate  48 . In other embodiments, the threads  55  may be provided by an insert (not shown) that is seated within the opening  54 . In other embodiments, the threads  55  may be provided by a fastener such as a nut that has been affixed to the retention plates  52  and/or the back plate  48 . In certain configurations, as shown in  FIGS. 2 and 5 , a plurality of mechanical fasteners or plugs  56  such as rivets or bolts may be used to seal the openings  54  during operation of the combustor. 
       FIG. 6  provides a perspective cutaway view of the cap assembly  10  as shown in  FIG. 5  with the openings  54  extending through the retaining plates  52  and the back plate  48 . As shown in  FIG. 6 , the openings  54  are generally aligned with at least a portion of the radial support feature  40 . For example, in particular embodiments, each of the openings  54  are aligned with a corresponding support member  44 . 
       FIG. 6  also illustrates a portion of a system  100  for loosening and/or separating the end cap assembly  18  from the inner barrel assembly  14  and/or the cap assembly  10 , according to one embodiment of the present subject matter. As shown in  FIG. 6 , the system  100  generally includes one or more push rods or pins  102  that extend through the openings  54  and engage with the radial support feature  40  of the end cap assembly  18 . In one embodiment, one end of each push rod  102  is aligned with a corresponding support member  44  of the radial support feature  40 . As shown, the push rods  102  are of a sufficient length so as to engage with the radial support feature  40  while extending through the inner barrel assembly  14  and outward through the back plate  48  and/or the retention plates  52  a sufficient distance so as to provide clearance with respect to the fuel nozzle collars  50 . 
     In particular embodiments, as shown in  FIG. 6 , a substantially linear force F may be applied to each push rod  102  so as to loosen and/or remove the end cap assembly  18  from the inner barrel assembly  14 , as illustrated in  FIG. 7 . In particular embodiments, the force F may be applied via a manual tool such as a mallet (not shown) or the like. Because the force F is directed into the support member  44  of the radial support feature  40 , damage to the cap plate  24  is avoided. In one embodiment, the force F may be applied to a single push rod  102  which is interchanged between the various openings to loosen and/or remove the end cap assembly  18  from the inner barrel assembly  14 . For example, a single push rod  102  may be inserted into one of the openings  54  and the force applied by a hammer or other tool. The push rod  102  may then be interchanged between the various openings  54  until the end cap assembly  18  is loose or removed from the cap assembly  10 . 
       FIG. 8  provides a perspective cutaway view of the cap assembly  10  as shown in  FIG. 6 , according to one embodiment of the present invention. As shown in  FIG. 8 , at least some of the push rods  102  may include threads  103 . The threads  103  may be complementary to the threads  55  disposed at and/or in the openings  54 . In this manner, the push rods  102  may be threaded into the openings  54  until the one end of each of the push rods  102  engages with a corresponding portion of the radial support feature  40  such as one or more of the support members  44 . In this embodiment, as shown in  FIG. 9 , the force F may be provided by applying torque T to turn the push rods  102  towards the end cap assembly  10 , thus loosening and/or removing the end cap assembly from the cap assembly. 
       FIG. 10  provides a perspective view of the push rods  102  connected to an alignment plate  104  according to one embodiment of the present subject matter. The alignment plate  104  may assure proper alignment of each push rod  102  with a corresponding opening  54  and may improve overall repair time. Although the alignment plate  104  is illustrated as a singular circular component, it should be known that the alignment plate  104  may have any shape and may comprise of multiple plates coupled together. For example, the alignment plate  104  may be triangular, square, rectangular, or oval shaped. In particular embodiments, the alignment plate  104  may be configured for coupling to a press. 
       FIG. 11  provides a perspective cutaway view of the cap assembly  10  including the push rods  102  and the alignment plate  104 . As shown, a substantially linear force F may be applied to the alignment plate  104  so as to loosen and/or remove the end cap assembly  18  from the inner barrel assembly  14 . The alignment plate  104  also may provide a substantially even distribution of the force F and may improve the time required to separate the end cap assembly  18  from the cap assembly  10 . 
       FIG. 12  provides a perspective cutaway view of the cap assembly  10  according to one embodiment of the present invention. Once the push rods  102  have been inserted into the openings  54 , the cap assembly  10  may be placed in an orientation such that the push rods  102  and/or the alignment plate  104  are in contact with a surface  106  such as a work bench, floor, repair fixture or the like. In this manner, the force F may be applied to the push rods  102  by providing an opposing or opposite force OF to at least one of the outer barrel  12  and the inner barrel assembly  14  so as to loosen and/or remove the end cap assembly  18  from the inner barrel assembly  14 . 
       FIG. 13  provides a perspective view of the cap assembly  10  including the push rods  102  and the alignment plate  104  mounted in an exemplary press  106 , according to one embodiment of the present subject matter. As shown in  FIG. 13 , the system  100  may include a press  106 . The press  106  may be manually operated or automated. The press  106  may be a pneumatic, hydraulic, electric or any other type of press that is capable of providing the substantially liner force F to the push rods  102  and/or the alignment plate  104 . 
     As shown in  FIG. 13 , the system  100  may include one or more vertical supports  108 . The vertical supports  108  may be placed under the cap assembly  10  during removal of the end cap assembly  18  to provide clearance for the end cap assembly  10  to translate out of the inner barrel  18  assembly. For example, the vertical supports  108  may be positioned in an annular array under the outer barrel  12 . 
     The system  100  shown and described herein with respect to  FIGS. 6 ,  7 ,  8 ,  9 ,  10 ,  11 ,  12  and  13  provides a method for loosening and/or removing the end cap assembly  18  from the cap assembly  10  as illustrated in  FIGS. 1 ,  2 ,  3 ,  4  and  5 . For example,  FIG. 14  illustrates a method  200  for loosening and/or removing the end cap assembly  18  from the cap assembly  10  according to an exemplary embodiment of the present subject matter. 
     At step  202 , the method  200  includes inserting at least one of the push rods  102  through a corresponding one of the openings  54  in the back plate portion  48  of the cap assembly  10 . Step  202  may further comprise boring the opening into the back plate  48  and/or the retention plate  52  prior to inserting the push rod  102  through the opening  54 . Step  202  also may include removing a mechanical fastener  56  from the opening  54  prior to inserting the push rod  102 . Step  202  also may include coupling the push rod  102  to the alignment plate  104  prior to or after inserting the push rod  102  through the opening  54 . Step  202  also may include threading the push rod  102  into the opening  54 . 
     At step  204 , the method  200  includes engaging one end of the push rod  102  with the radial support feature  40  of the end cap assembly  18 . For example, step  204  may include aligning and/or engaging the one end of the push rod  102  with one of the support members  44  such that the push rod  102  does not engage and/or otherwise interact with the cap plate  24 . 
     At step  206 , the method  200  includes applying force F to the push rod  102 . The force F is generally sufficient to loosen and/or completely remove the end cap assembly  18  from the cap assembly  10 . In particular embodiments, the force F may be applied via the press  106  and/or via a manual tool such as a mallet or the like. The force F is transferred to through the push rod  102  to the radial support feature  40 , thereby preventing deformation and/or damage to the cap plate  24  during disassembly. The force F also may be applied by providing an opposing or opposite force OF to at least one of the inner barrel assembly  14  or the outer barrel  12 . In particular embodiments, the method  200  also includes removing the plurality of mechanical fasteners  38  that extend radially between the inner barrel  14  of the cap assembly  10  and the end cap assembly  18  prior to applying the force F to the push rod  102 . 
       FIG. 15  illustrates a method  300  for loosening and/or removing the end cap assembly  18  from the cap assembly  10  according to another exemplary embodiment of the present subject matter. As shown at step  302 , the method  300  includes inserting a plurality of the push rods  102  through a plurality of corresponding openings  54  defined in the back plate  48  of the cap assembly  10 . In addition or in the alternative, the openings  54  may be defined within the retention plates  52 . Step  302  may further comprise boring the openings into the back plate  48  prior to inserting the push rods  102 . In addition, step  302  may include removing a plurality of mechanical fasteners  56  from each or some of the openings  54  prior to inserting the push rods  102 . Step  302  also may include coupling the push rods  102  to the alignment plate  104  prior to or after inserting the push rods  102  through the openings  54 . 
     At step  304 , the method  300  includes engaging one end of each push rod  102  with the radial support feature  40  of the end cap assembly  18 . For example, step  304  may include aligning and/or engaging the one end of each of the push rods  102  with one of the support members  44  such that the push rods  102  do not engage and/or otherwise interact with the cap plate  24 . 
     At step  306 , the method  300  includes mounting and/or positioning the cap assembly  10  within the press  106 . Step  306  also may include positioning the outer barrel  12  of the cap assembly  10  atop the vertical supports  108 . 
     At step  308 , the method  300  includes applying the force F to the push rods  102  via the press. The force F may be provided by applying an opposing force via the press  106  to at least one of the outer barrel  12  or the inner barrel assembly  14  of the cap assembly  10 . Step  308  may further include removing the plurality of mechanical fasteners  38  that extend radially between an inner barrel assembly  14  and the end cap assembly  18  prior to applying the force F to the push rods  102 . The force F may be applied to the push rods via the alignment plate  104 . 
       FIG. 16  illustrates a method  400  for loosening and/or removing the end cap assembly  18  from the inner barrel assembly  14  and/or the cap assembly  10  according to another exemplary embodiment of the present subject matter. As shown at step  402 , the method  400  includes removing the plurality of mechanical fasteners  38  that extend between the inner barrel assembly  14  and the end cap assembly  18 . The mechanical fasteners  38  may be removed by cutting, prying or any other suitable method. Step  402  may further comprise boring the openings  54  into the retention plates  52  and/or the back plate  48 . Step  402  also may include removing the plurality of mechanical fasteners  56  from each or some of the openings  54 . The mechanical fasteners  56  may be removed by cutting, prying or any other suitable method. 
     At step  404 , the method  400  includes inserting a plurality of the push rods  102  through a corresponding plurality of the openings  54  defined within one or more of the retention plates  52  and/or the back plate  48  of the cap assembly  10 . Step  404  also may include threading the push rods  102  into the openings  54 . Step  404  also may include coupling the push rods  102  to the alignment plate  104  prior to or after inserting the push rods  102  through the openings  54 . 
     At step  406 , the method  400  includes engaging one end of each push rod  102  with the radial support feature  40  of the end cap assembly  10 . For example, step  406  may include aligning and/or engaging the one end of each of the push rods  102  with one of the support members  44  such that the push rods  102  do not engage and/or otherwise interact with the cap plate  24 . 
     At step  408 , the method  400  includes positioning the outer barrel  12  of the cap assembly  10  atop one or more of the vertical supports  108  to provide clearance for the end cap assembly  18  to translate out of the inner barrel assembly  14 . 
     At step  410 , the method  400  includes applying a force F to the push rods. The force F is generally sufficient to loosen and/or completely remove the end cap assembly  18  from the cap assembly  10 . In particular embodiments, the force F may be applied via a manual tool such as a mallet or the like. In particular embodiments, the force F is applied to the push rods by applying torque to the push rods. The force F is transferred to through the push rod  102  to the radial support feature  40 , thereby preventing deformation and/or damage to the cap plate  24  during disassembly. 
     In addition, method  400  may further include positioning the cap assembly  10  within the press  106  and applying the force F via the press  106 . Again, the force F is transferred to through the push rod  102  to the radial support feature  40 , thereby preventing deformation and/or damage to the cap plate  24  during disassembly. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.