Abstract:
A support arrangement for a diaphragm segment in a turbine casing that includes: 1) a support bar joined to a diaphragm segment; 2) a turbine casing comprising a vertical wall and a horizontal shoulder, wherein a portion of the horizontal shoulder underlies the support bar; 3) a cut out area defined by the vertical wall and an outer edge of the support bar; and 4) a shim interposed between the horizontal shoulder and the support bar. The cut out area may be a size that allows the shim to pass through.

Description:
TECHNICAL FIELD 
       [0001]    This present application relates generally to power generating turbines. More specifically, but not by way of limitation, the present application relates to systems for to support arrangements for diaphragms within a turbine casing. 
       BACKGROUND OF THE INVENTION 
       [0002]    A typical double-flow, low pressure (LP) steam turbine includes a pair of LP rotor sections surrounded, respectively, by diaphragms, each of which is comprised of a pair of semi-annular diaphragm ring segments that are joined at horizontal joints, spaced 180° from each other. Each ring segment supports a plurality of static nozzles that direct flow into the rotating buckets on axially spaced rotor wheels. The diaphragms are typically located axially between the rows of buckets and are typically supported vertically by any of several known methods. These include support bars, pins or support screws. Each design has its own advantages and disadvantages. 
         [0003]    Support bars, for example, currently require that the diaphragm be installed before alignment. After the required measurements are recorded, the diaphragm and rotor are removed so the support bar can be machined to adjust the vertical position of the diaphragm. The sequence is then repeated as necessary to verify the diaphragm position. In addition, current diaphragm adjustment requires removal of both the diaphragm and the rotor as well as bolted-in shims, and can thus take several shifts or days to adjust. 
         [0004]    Current support screw designs can only be used on the smaller HP stages because the weight of IP and LP stages is too great. Further, support pins, which are generally used in LP turbines, cannot support as much weight as support bar designs. 
         [0005]    Accordingly, there remains a need for an easily accessible support arrangement that facilitates vertical adjustment of the diaphragm ring segment in a relatively quick and efficient manner. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    The present application thus describes a support arrangement for a diaphragm segment in a turbine casing that includes: 1) a support bar joined to a diaphragm segment; 2) a turbine casing comprising a vertical wall and a horizontal shoulder, wherein a portion of the horizontal shoulder underlies the support bar; 3) a cut out area defined by the vertical wall and an outer edge of the support bar; and 4) a shim interposed between the horizontal shoulder and the support bar. The cut out area may be a size that allows the shim to pass through. 
         [0007]    The support bar may include a flange that engages an outwardly facing slot in the diaphragm segment. One or more bolts may extend through the flange and into the diaphragm segment. 
         [0008]    The support arrangement may include means for retaining the shim between the horizontal shoulder and the support bar. In some embodiments, the means for retaining the shim between the horizontal shoulder and the support bar may include a shim retainment step in the horizontal shoulder. The shim retainment step may include a step that at least partially encloses the shim when the shim is positioned between the horizontal shoulder and the support bar. In other embodiments, the means for retaining the shim between the horizontal shoulder and the support bar comprises a back block positioned in the cutout area. The back block may abut the shim and the vertical wall of the turbine casing. The back block may be secured to the turbine casing by a bolt that passes through the back block into the horizontal shoulder. The height of the back block may be approximately the same as the height of the shim. In other embodiments, the height of the back block is approximately the same as the height of the support bar. 
         [0009]    In some embodiments, the shim may include a removal hole. The support arrangement may further include a puller with a threaded insert that may engage the removal hole. In some embodiments, at least one of the sides of the shim may extend beyond an edge of the support bar, and the removal hole may be positioned within a portion of the shim that extends beyond the edge of the support bar. 
         [0010]    The present application further describes a turbine, that includes: 1) a diaphragm that includes a lower diaphragm segment and an upper diaphragm segment that join at a horizontal split; 2) a support bar that attaches to the lower diaphragm segment; 3) a turbine casing that includes a vertical wall and a horizontal shoulder, wherein a portion of the horizontal shoulder underlies the support bar; 4) a cut out area defined by the vertical wall and an outer edge of the support bar; and 5) a shim interposed between the horizontal shoulder and the support bar. The cut out area comprises a size that allows the shim to pass through. 
         [0011]    In some embodiments, at least one of the sides of the shim may extend beyond an edge of the support bar, the shim further comprises a removal hole that may be positioned within a portion of the shim that extends beyond the edge of the support bar. The turbine may further include a puller with a threaded insert that may engage the removal hole. 
         [0012]    In some embodiments, the turbine may further include a shim retainment step in the horizontal shoulder. The shim retainment step may include a step that at least partially encloses the shim when the shim is positioned between the horizontal shoulder and the support bar. In other embodiments, the turbine may include a back block positioned in the cutout area such that the back block abuts the shim and the vertical wall of the turbine casing. The back block may be secured to the turbine casing by a bolt that passes through the back block into the horizontal shoulder. 
         [0013]    In some embodiments, the support bar may include a flange that engages an outwardly facing slot in the lower diaphragm segment. These and other features of the present application will become apparent upon review of the following detailed description of the preferred embodiments when taken in conjunction with the drawings and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a cross section, in partially schematic form, illustrating a conventional double flow, low pressure steam turbine; 
           [0015]      FIG. 2  is a generally schematic end elevation of a pair of annular diaphragm ring segments joined at a horizontal split surface; 
           [0016]      FIG. 3  is a partial end elevation of a conventional diaphragm support bar attached to a lower diaphragm ring segment; 
           [0017]      FIG. 4  is a partial end elevation of a support bar attached to a lower diaphragm segment in accordance with an exemplary embodiment of the invention; 
           [0018]      FIG. 5  is a partial plan view of the support bar illustrated in  FIG. 4 ; 
           [0019]      FIG. 6  is a partial end elevation of a support bar attached to a lower diaphragm segment in accordance with an alternative embodiment of the invention; and 
           [0020]      FIG. 7  is a partial plan view of the support bar illustrated in  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    Referring now to the figures, where the various numbers represent like parts throughout the several views,  FIG. 1  illustrates a conventional double-flow, low pressure (LP) steam turbine  10  that includes first and second low pressure (LP) turbine sections  12 ,  14  surrounded by diaphragm assemblies  16 ,  18 , respectively. 
         [0022]    Each diaphragm is composed of a pair of semi-annular diaphragm ring segments  20 ,  22  ( FIG. 2 ) joined at a horizontal split or joint surfaces  24 . Each diaphragm segment supports a semi-annular row of nozzles  26  and an inner web  28 . 
         [0023]    With reference now to  FIG. 3 , the lower diaphragm ring segment  22  is shown to be vertically supported within a turbine casing half (or simply, casing)  30  by a support bar  32  bolted to the diaphragm segment  22  by bolt(s)  34  extending through the support bar, and specifically through an inwardly directed flange  36  of the support bar that is received in a mating slot  38  in the lower diaphragm segment. The support bar otherwise extends vertically along the casing  30  on one side and the diaphragm segment  22  on the other side. The lower surface  40  of the support bar faces a shoulder  42  formed in the casing  30 , with a shim block  44  interposed between the shoulder  42  and the lower surface  40  and typically bolted to the casing  30 . A second shim block  46  is shown seated on the upper surface  48  of the support bar to effectively make the upper end of the support bar flush with the horizontal joint surfaces  50 ,  52  of the casing and diaphragm half, respectively, enabling the support bar  32  to be sandwiched between the upper and lower casing sections. The other side of the lower diaphragm segment  22  is similarly supported at the opposite side of the casing. 
         [0024]      FIGS. 4 and 5  illustrate a newly designed support arrangement for a diaphragm segment in a turbine casing in accordance with an exemplary embodiment of this invention. A support bar  54  is formed with a flange  58 . The lower diaphragm segment  66  is formed with an outwardly facing slot  68  that receives the flange  58 . The support bar  54  is attached to the lower diaphragm segment  66  with bolts  69 , which extend laterally through the support bar  54  and the flange  58  into the diaphragm segment  66 . 
         [0025]    A lower turbine casing or turbine casing  72  is formed with a cutout area  74  that includes a vertical wall  76  and a horizontal shoulder  78 , a portion of which underlies the support bar  54 . The cutout area  74 , thus, is defined by the vertical wall  76  of the turbine casing  72  and an outer edge  79  of the support bar  54 . In some embodiments, the shoulder  78  is formed with a shim retainment step  80  that is shaped to receive and at least partially enclose a shim  82 . The shim  82  may be a single block. Thus, when the diaphragm segment  66  is located within the lower turbine casing  72 , it is vertically supported by the bottom edge of the support bar  54  engaged indirectly with the casing shoulder  78 , with the shim  82  interposed therebetween. It will be appreciated that a similar support bar is employed on the other side of the diaphragm segment, along the horizontal joint or split line. 
         [0026]      FIG. 5  illustrates a plan view of the support bar  54 . As shown, when installed, the sides of the shim  82  may extend beyond the edge of the support bar  54 . In either of these sides, a removal hole  89  may be positioned. The removal hole  89  may be sized such that it may be engaged by a threaded insert  90  of a puller  92 , as illustrated on  FIG. 4 . 
         [0027]    With the above arrangement, adjustment of the vertical position of the diaphragm segment  66  in the lower casing  72  may be achieved with reduced downtime. It is only necessary to raise the lower diaphragm segment  66  an amount sufficient to allow removal of the shim  82  from the shim retainment step  80  so that the shim  82  can be removed and a differently-sized shim located in the shim retainment step  80 . The removal of the shim  82  may be aided with the puller  92 , which may be lowered through the cutout area  74 . The threaded insert  90  of the puller  92  may engage the removal hole  89  of the shim  82  such that the shim  82  may be removed from underneath the support bar  54 . Once the shim  82  is no longer beneath the support bar  54  (see a shim in removal position  94 ), the shim  82  may be removed vertically through the cutout area  74 . 
         [0028]    Thus, in use, the shim  82  may be removed and replaced as follows. First, the lower diaphragm segment  66  and the support bar  54  may be raised such that the lower surface of the support bar  54  no longer engages the shim  82 . The lower diaphragm segment  66  and the support bar  54  may be further raised so that the shim  82  may clear the shim retainment step  80 . Then, the puller  92  may be lowered through the cutout area  74  and positioned so that the threaded insert  90  engages the removal hole  89 . Thus engaged, the puller  92  may be used to lift the shim  82  over the shim retainment step  80  and slide the shim  82  into the cutout area  74  (see the shim in removal position  94 ). The puller  82  then lifts the shim  82  through the cutout area  74  so that it may be removed. Once removed the shim  82  may be machined so that the proper vertical alignment of the lower diaphragm segment is achieved. The steps then may be reversed for the repositioning of the shim  82  under the support bar  54 . 
         [0029]    In an alternative embodiment, as illustrated in  FIGS. 6 and 7 , the shim  82  may be secured in place beneath the support bar  54  by a back block  100 . The back block  100  may include a solid block that is positioned in the cutout area  74  such that it prevents the shim  82  from moving into the cutout area  74  during operation. As shown, the back block  100  may be a rectangular block that, once installed in the cutout area  74 , generally abuts the shim  82  and the vertical wall  76  of the turbine casing  72 . The back block  100  may be held into place by a bolt  102 . In some embodiments, the height of the back block  100  may be approximately the same as the shim  82 . In other embodiments, as shown, the vertical height of the back block  100  may be much greater so that it has approximately the same vertical height as the support bar  54 . In such an arrangement, more efficient access to the bolt  102  may be achieved, which may allow the bolt  102  to be efficiently staked during installation. 
         [0030]    With back block  100  holding the shim  82  in place, the shim retainment step  80  may be unnecessary. Thus, in use, the shim  82  may be removed and replaced as follows. First, the lower diaphragm segment  66  and the support bar  54  may be raised such that the lower surface of the support bar  54  no longer engages the shim  82 . Because there is no shim retainment step  80 , further raising of the lower diaphragm segment  66  and the support bar  54  is unnecessary. The bolt  102  may be disengaged and the back block  100  removed. Then, the puller  90  may be lowered through the cutout area  74  and positioned so that the threaded insert  92  engages the removal hole  89 . Thus engaged, the puller may be used to slide the shim  82  into the cutout area  74  (see the shim in removal position  94 ) and then to remove the shim  82  through the cutout area  74 . Once removed, the shim  82  may be machined so that the proper vertical alignment of the lower diaphragm segment is achieved. The steps then may be reversed for the repositioning of the shim  82  under the support bar  54 . 
         [0031]    From the above description of preferred embodiments of the invention, those skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims. Further, it should be apparent that the foregoing relates only to the described embodiments of the present application and that numerous changes and modifications may be made herein without departing from the spirit and scope of the application as defined by the following claims and the equivalents thereof.