Abstract:
The present application provides an extraction system for removing a retaining pin from a turbine engine. The extraction system may include a pin extraction fixture and a drill such that the pin extraction fixture positions the drill about the retaining pin. The pin extraction fixture may include a collet and one or more expanders positioned thereabout.

Description:
TECHNICAL FIELD 
       [0001]    The present application relates generally to gas turbine engines and more particularly relates to systems and methods for extracting broken shroud retaining pin plugs from a turbine casing in a fast, safe, and efficient manner. 
       BACKGROUND OF THE INVENTION 
       [0002]    Gas turbine engines and other types of turbo-machinery require routine field maintenance and/or repair. Such maintenance or repair may require the disassembly of certain components of the gas turbine engine. For example, turbine shroud blocks may need to be removed in order to obtain access to the turbine buckets. These turbine shroud blocks generally are positioned just outboard of the turbine buckets and may be held in position by a number of retaining pins. The retaining pins typically are installed radially through threads in a turbine casing and into a receiving hole in the shroud block. The retaining pins generally include a plug at one end thereof. The retaining pins may be difficult to remove during maintenance. Specifically, the application of too much torque may shear off the plug in the turbine casing. 
         [0003]    When retaining pin plugs are sheared off during field maintenance, the plugs generally are drilled out by hand using numerous drill bits, grinding burs, and the like. This hand drilling, however, sometimes causes damage to the turbine casing threads or elsewhere. Moreover, access to the broken plugs on, for example, the lower half of the turbine casing may be difficult to reach and requires precision work in often cramped quarters. 
         [0004]    There is therefore a desire for improved systems and methods for removing broken shroud retaining pins and the like from a turbine casing. Such systems and methods should provide for quick removal of the broken shroud retaining pins while preventing damage to the turbine casing. 
       SUMMARY OF THE INVENTION 
       [0005]    The present application thus provides an extraction system for removing a retaining pin from a turbine engine. The extraction system may include a pin extraction fixture and a drill such that the pin extraction fixture positions the drill about the retaining pin. The pin extraction fixture may include a collet and one or more expanders positioned thereabout. 
         [0006]    The present application further provides for a method of extracting a retaining pin plug from a turbine casing of a turbine engine. The method may include the steps of positioning a pin extraction fixture within a counter-bore of the turbine casing, positioning a drill bushing within the pin extraction fixture, positioning a drill bit within the drill bushing, drilling the plug with the drill bit, removing the drill bit, the drill bushing, and the pin extraction fixture from the counter-bore of the turbine casing, inserting a screw extractor into the counter-bore of the turbine casing and the plug, and removing the plug from the counter-bore of the turbine casing with the screw extractor. 
         [0007]    The present application further provides a pin extraction fixture. The pin extraction feature may include a collet, a lower collet expander, a torque wheel, and an upper collet expander. 
         [0008]    These and other features and improvements of the present application will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a schematic view of a gas turbine engine. 
           [0010]      FIG. 2  is a side cross-sectional view of portions of a turbine showing the casing, a shroud block, and a one piece retaining pin. 
           [0011]      FIG. 3  is a side cross-sectional view of portions of a turbine showing the casing, a shroud block, and a two piece retaining pin. 
           [0012]      FIG. 4  is an exploded view of a pin extraction system as may he described herein. 
           [0013]      FIG. 5  is a side cross-sectional view of a pin extraction fixture of the pin extraction system of  FIG. 4 . 
           [0014]      FIG. 6  is a perspective view of a collet of the pin extraction fixture of  FIG. 5 . 
           [0015]      FIG. 7  is a side cross-sectional view of the collet of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Referring now to the drawings, in which like numerals refer to like elements throughout the several views,  FIG. 1  shows a schematic view of gas turbine engine  10  as may be described herein. The gas turbine engine  10  may include a compressor  15 . The compressor  15  compresses an incoming flow of air  20 . The compressor  10  delivers the compressed flow of air  20  to a combustor  25 . The combustor  25  mixes the compressed flow of air  20  with a compressed flow of fuel  30  and ignites the mixture to create a flow of combustion gases  35 . Although only a single combustor  25  is shown, the gas turbine engine  10  may include any number of combustors  25 . The flow of combustion gases  35  is in turn delivered to a turbine  40 . The flow of combustion gases  35  drives the turbine  40  so as to produce mechanical work. As described above, the mechanical work produced in the turbine  40  drives the compressor  15  via a shaft  45  and an external load  50  such as an electrical generator and the like. 
         [0017]    The gas turbine engine  10  may use natural gas, various types of syngas, and/or other types of fuels. The gas turbine engine  10  may be any one of a number of different gas turbine engines offered by General Electric Company of Schenectady, N.Y. and the like. The gas turbine engine  10  may have different configurations and may use other types of components. Other types of gas turbine engines also may be used herein. Multiple gas turbine engines, other types of turbines, and other types of power generation equipment also may be used herein together. 
         [0018]      FIG. 2  shows a portion of the turbine  40 . Specifically, a shroud Hock  55  is attached to a turbine casing  60  via a retaining pin  65 . The retaining pin  65  may extend through a counter-bore  70  within the turbine casing  60  and extend into a receiving hole  75  within the shroud block  55 . In the example of  FIG. 2 , a one-piece retaining pin is used  80 . The one-piece retaining pin  80  has integral plug  85  and pin portions  90 .  FIG. 3  shows a two-piece retaining pin  95  with separate plug  85  and pin portions  90 . In either case, a number of plug threads  96  cooperate with a number of casing threads  97  to position the retaining pin  65  in place. As described above, the application of too much torque may cause the plug  85  to shear off. 
         [0019]      FIG. 4  shows a pin extraction system  100  as may be described herein. The pin extraction system  100  may include a pin extraction fixture  110  as is shown in  FIGS. 4 and 5 . The pin extraction fixture  110  may include a collet  120  as is also shown in  FIGS. 5-7 . As is known, a collet  110  is a type of chuck so as to provide a damping force on a work piece or a tool. The collet  120  may have a spring surface  130  with a number of kerfs  140  cut therein to allow for expansion and contraction. Likewise, the spring surface  130  may have an inner taper  150  with a largely hourglass-like shape. One end of collet  120  may have a collet alignment hole  160  therein. The other end of the collet  120  may have a number of internal bosses  165 . Other configurations and other components may be used herein. 
         [0020]    A lower collet expander  170  may be positioned within one end of the collet  120 . (The terms “lower”, “upper”, and the like are meant to signify relative positions only. Either direction may be considered upper or lower.) The lower collet expander  170  may have a generally conical shape  180  so as to mate with the inner taper  150  of the collet  120 . The lower collet expander  170  also may have a number of lower expander threads  190  on an interior thereof. The lower collet expander  170  also may have a lower expander alignment hole  200 . The internal bosses  165  of the collet  120  may interface with the lower collet expander  170  to prevent rotation during tightening. A pin also may be used therein. Other configurations and other components may be used herein. 
         [0021]    The other end of the collet  120  may be positioned within a torque wheel  210 . The torque wheel  210  may have a largely flat donut like shape with an aperture  220  therein. The collet  120  may be positioned within the aperture  220  and locked into place via a number of set screws  230  or other types of attachment devices via the collet alignment holes  160 . Other configurations and other components also may be used herein. 
         [0022]    An upper collet expander  240  may be positioned within the collet  120  and the torque wheel  210 . The upper collet expander  240  may have an upper expander plate  250  and an upper expander tube  260  attached thereto. The upper expander plate  250  may have a largely hexagon-like shape  270  and the like. The hexagon shape  270  allows the tightening of the upper collet expander  240  via a wrench and the like. The upper expander tube  260  includes a number of upper expander threads  280  thereon. The upper expander threads  280  mate with the lower expander threads  190  of the lower collet expander  170 . The upper expander plate  250  may have a plate aperture  290  therein. A lock screw  300  may be positioned therein so as to position a drill bushing  310  within the upper collet expander  240 . Other configurations and other components may be used herein. 
         [0023]    As above, the drill bushing  310  may be positioned within the upper collet expander  240 . The drill bushing  310  may be sized for the appropriate drill bit as will be described in more detail below. A number of drill bushings  310  may be used herein. Other configurations and other components may be used herein. 
         [0024]    Referring again to  FIG. 4 , the pin extraction system  100  also may include a drill  320  for use with the pin extraction fixture  110 . The drill  320  may be of conventional hand drill design and may be electric, pneumatic, and the like. The drill  320  may have a drill bit  330  therein. The drill  320  may use many different types and sizes of drill bits  330 . Other configurations and other components may be used herein. The drill  320  also may be used with a locating cylinder  325 . The drill  320  with the locating cylinder  325  may be used in lieu of the pin extraction fixture  110  when there may be insufficient counterbore depth. 
         [0025]    In use the pin extraction system  100  may be used with many different types of gas turbine engines  10 . As such, multiple pin extraction fixtures  110  and/or multiple components thereof may be used and sized for a particular type of turbine  40  and/or retaining pin  65 . The pin extraction system  100  may be used with any threaded plug in an type of casing, i.e., a gas turbine, a stream turbine, a heavy duty compressor, or other types of industrial equipment. 
         [0026]    In order to remove a broken retaining pin  65 , the pin extraction fixture  110  may be positioned within the counter-bore  70  of the casing  60 . The collet  120  may be expanded therein by tightening the upper expander plate  250  with respect to the torque wheel  210 . The appropriately sized drill bushing  310  may be positioned therein. The drill bit  330  of the drill  320  then may be positioned within the drill bushing  310  so as to drill the plug  85  of the retaining pin  65 . Differently sized drill bits  330  and/or different types of drills  320  may be used. Once the plug  85  has been drilled through, the pin extraction fixture  110  may be removed. A screw extractor  340  may be positioned within the drilled hole so as to remove the plug  85  if needed. 
         [0027]    The pin extraction system  100  thus allows quick and efficient removal of retaining pins  65  from the casing  60 . Moreover, the retaining pins  65  may be removed without causing damage to the turbine casing  60 . The pin extraction system  100  thus reduces the time required for field maintenance and the like. The pin extraction system  100  and the pin extraction fixture  110  may be used to remove any type of embedded fixture within a bore. 
         [0028]    The use of the drill  320  with the locating cylinder  325  allows the drill centerline to be placed on within a shallow counterbore or spotface that lacks ample depth for the pin extraction fixture  110 . The locating cylinder  325  may be sized to fit within the spotface diameter with an end that is perpendicular to the rotation axis. The operator places the location cylinder  325  into the spotface and then overcomes the spring force to drill a hole through the sheared plug. 
         [0029]    It should be apparent that the foregoing relates only to certain embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.