Abstract:
A method of assembling a turbine casing is provided. The method includes inserting a bolt assembly through a first opening defined generally vertically through a first flange extending from a first casing member, such that a portion of the bolt assembly extends a distance upward from an upper surface of the first casing flange and such that the bolt assembly is retained within the first opening. The method further includes positioning a second casing member including a second flange including a second opening defined therein against the first casing member such that a portion of the bolt assembly extends through the opening defined in the second casing flange.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates generally to steam turbine engines, and more particularly, to bolt assemblies used with steam turbine engines. 
         [0002]    At least some known steam turbine engines include an upper half casing and a lower half casing wherein the upper half casing includes a horizontal joint flange feature and the lower half casing includes a horizontal joint flange feature. The upper half horizontal joint casing flange and the lower half horizontal joint casing flange are coupled together with a number of bolt and nut assemblies. At least one known bolt assembly, sometimes referred to as a “through” bolt assembly, includes a single bolt, suitably threaded on both ends, and a pair of nuts that are used to couple the pair of flanges together. For example, a single threaded bolt may be inserted through an opening defined within each flange. Moreover, a first nut may be threadably coupled to a first end of the bolt such that the first nut is substantially flush with a surface of the first horizontal joint flange, and a second nut may be threadably coupled to a second end of the bolt such that the second nut is substantially flush with a surface of the second horizontal joint flange. This at least one known bolt assembly is often referred to as a “through” bolt assembly. During assembly of at least one known “through” bolt assembly, when the bolt is inserted through a flange opening, the bolt will fall out of the opening until at least one nut is coupled to the bolt to retain the bolt within the flange. Coupling a nut to the bolt can present difficulty due to space constraints around each flange and due to the difficulty of simultaneously tightening both ends of the bolt assembly. 
         [0003]    At least one known bolt assembly, sometimes referred to as a “tapped” bolt assembly, is used when structural sub-assemblies of a steam turbine engine are completely contained within the body of the engine making access to the sub-assembly difficult. At least one known “tapped” bolt assembly includes a threaded hole integral to the lower half horizontal joint flanges. The threaded hole eliminates the need for a second nut coupled to the second horizontal joint flange. Threading the hole integral to a horizontal joint flange can present difficulty due to space constraints. Moreover, during assembly and use of the “tapped” bolt assembly, the threads integral to the horizontal joint flange may be easily worn and/or stripped. When the threads of the hole integral to the horizontal joint flange are worn and/or stripped, the threads are difficult to repair and/or replace. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0004]    In one aspect, a method of assembling a turbine casing is provided. The method includes inserting a bolt assembly through a first opening defined generally vertically through a first flange extending from a first casing member, such that a portion of the bolt assembly extends a distance upward from an upper surface of the first casing flange such that the bolt assembly is retained within the first opening. The method further includes positioning a second casing member including a second flange including a second opening defined therein against the first casing member such that a portion of the bolt assembly extends through the opening defined in the second casing flange. 
         [0005]    In a further aspect, a steam turbine engine assembly is provided. The steam turbine engine includes at least one casing including a flange including at least one opening extending through the flange. The steam turbine engine assembly also includes a bolt assembly configured to be inserted within the at least one casing. The bolt assembly including a bolt and a retaining mechanism, the bolt configured to be inserted from a lower surface of the flange through the at least one opening such that a portion of the bolt extends a distance above an upper surface of the flange, the bolt retaining mechanism at least partially circumscribes the bolt to facilitate retaining the bolt within the at least one opening. 
         [0006]    In another aspect, a bolt assembly for a steam turbine engine assembly is provided. The steam turbine engine assembly includes at least one casing including a flange including at least one opening extending through the flange. The bolt assembly includes a bolt configured to be inserted within the at least one casing. The bolt is configured to be inserted from a lower surface of the flange through the at least one opening such that a portion of the bolt extends a distance above an upper surface of the flange. The bolt assembly also includes a retaining ring coupled to the bolt such that the retaining ring at least partially circumscribes the bolt to facilitate retaining the bolt within the at least one opening. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]      FIG. 1  is a schematic illustration of an exemplary opposed-flow steam turbine engine; 
           [0008]      FIG. 2  is a perspective view of an exemplary shell casing that may be used with the steam turbine shown in  FIG. 1 ; 
           [0009]      FIG. 3  is a perspective view of an exemplary bolt assembly that may be used with the shell casing shown in  FIG. 2 ; 
           [0010]      FIG. 4  is a perspective view of a first alternative bolt assembly that may be used with the shell casing shown in  FIG. 2 ; 
           [0011]      FIG. 5  is a perspective view of a second alternative bolt assembly that may be used with the shell casing shown in  FIG. 2 ; 
           [0012]      FIG. 6  is a perspective view of the bolt assembly shown in  FIG. 3  and in a partially assembled configuration; and 
           [0013]      FIG. 7  is a perspective view of the bolt assembly shown in  FIG. 3  in a fully assembled configuration. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0014]      FIG. 1  is a schematic illustration of an exemplary opposed-flow steam turbine engine  100  including a high pressure (HP) section  102  and an intermediate pressure (IP) section  104 . An HP shell, or casing,  106  is divided axially into upper and lower half sections  108  and  110 , respectively. Similarly, an IP shell  112  is divided axially into upper and lower half sections  114  and  116 , respectively. In the exemplary embodiment, shells  106  and  112  are inner casings. Alternatively, shells  106  and  112  are outer casings. A central section  118  positioned between HP section  102  and IP section  104  includes a high pressure steam inlet  120  and an intermediate pressure steam inlet  122 . 
         [0015]    An annular section divider  134  extends radially inwardly from central section  118  towards a rotor shaft  140  that extends between HP section  102  and IP section  104 . More specifically, divider  134  extends circumferentially around a portion of rotor shaft  140  between a first HP section inlet nozzle  136  and a first IP section inlet nozzle  138 . Divider  134  is received in a channel  142 . 
         [0016]    During operation, high pressure steam inlet  120  receives high pressure/high temperature steam from a steam source, for example, a power boiler (not shown in  FIG. 1 ). Steam is routed through HP section  102  from inlet nozzle  136  wherein work is extracted from the steam to rotate rotor shaft  140  via a plurality of turbine blades, or buckets (not shown in  FIG. 1 ) that are coupled to shaft  140 . Each set of buckets includes a corresponding stator assembly (not shown in  FIG. 1 ) that facilitates routing of steam to the associated buckets. The steam exits HP section  102  and is returned to the boiler wherein it is reheated. Reheated steam is then routed to intermediate pressure steam inlet  122  and returned to IP section  104  via inlet nozzle  138  at a reduced pressure than steam entering HP section  102 , but at a temperature that is approximately equal to the temperature of steam entering HP section  102 . Work is extracted from the steam in IP section  104  in a manner substantially similar to that used for HP section  102  via a system of rotating and stationary components. Accordingly, an operating pressure within HP section  102  is higher than an operating pressure within IP section  104 , such that steam within HP section  102  tends to flow towards IP section  104  through leakage paths that may develop between HP section  102  and IP section  104 . 
         [0017]    In the exemplary embodiment, steam turbine engine  100  is an opposed-flow high pressure and intermediate pressure steam turbine combination. Alternatively, steam turbine engine  100  may be used with any individual turbine including, but not being limited to low pressure turbines. In addition, the present invention is not limited to being used with opposed-flow steam turbines, but rather may be used with steam turbine configurations that include, but are not limited to, single-flow and double-flow turbine steam turbines. Moreover, the present invention is not limited to steam turbines, but rather may be used with gas turbine engines. 
         [0018]      FIG. 2  is a perspective view of an exemplary shell casing  200  that may be used with the steam turbine  100 . Shell casing  200  includes an upper casing  202  and a lower casing  204 . Each casing  202  and  204  includes a radially inner surface  203  and an opposite radially outer surface  205 . Each casing  202  and  204  may include, but is not limited to including, a line of cap screws, a line of studs, and/or any combination thereof. 
         [0019]    In the exemplary embodiment, casing  202  includes at least one flange  206 , and casing  204  includes at least one flange  208 . In the exemplary embodiment, flanges  206  and  208  extend outward from radially outer surfaces  205 . In the exemplary embodiment, flanges  206  and  208  receive a bolt assembly  300  therein, as will be discussed in more detail herein. In an alternative embodiment, bolt assembly  300  may be used with any pair of flanges that facilitate coupling casing  202  to casing  204 . In an alternative embodiment, shell casing  200  includes a plurality of pairs of flanges  206  and  208  wherein each pair of flanges receives bolt assembly  300 . 
         [0020]    Each flange  206  and  208  includes at least one opening  210  and  212 , respectively, defined therein and sized to receive at least a portion of bolt assembly  300  therethrough. Opening  210  extends between a first surface  207  and a second surface  209  of flange  206 , and opening  212  extends between a first surface  211  and a second surface  213  of flange  208 . In the exemplary embodiment, opening  210  is counterbored, as will be discussed in more detail below. Moreover, each casing  202  and  204  includes a plurality of openings  214  (shown in  FIG. 6 ) defined at least partially therein. Each opening  214  is sized to receive a dowel (not shown) therein that facilitates assembly of shell casings  202  and  204  and that facilitates aligning casing  202  with casing  204 . In an alternative embodiment, each opening  214  receives known traditional hardware that ease assembly. During assembly, in the exemplary embodiment, casings  202  and  204  are coupled together via flanges  206  and  208  such that openings  210  and  212  are substantially concentrically aligned with respect to each other and such that surfaces  209  and  211  are positioned in mating contact with each other. 
         [0021]      FIG. 3  is a perspective view of an exemplary bolt assembly  300  that may be used with shell casing  200 . Bolt assembly  300  includes a bolt  302  and a nut  304  is configured to threadably couple to bolt  302 . The thread orientation on bolt assembly  300  facilitates reducing the amount of rotation necessary to fully assemble assembly  300 . In the exemplary embodiment, bolt  302  is a through bolt that includes a first end or a head  301  and an opposing second end  303 . 
         [0022]    Bolt  302  includes a plurality of portions  308 ,  310 ,  312 ,  314 ,  316  that extend through flange openings  206  and  208 . In the exemplary embodiment, portions  308 ,  310 ,  312 ,  314 ,  316  are integrally formed together. Moreover, bolt  302  is formed with a bore  306  that extends longitudinally and concentrically therethrough. Bore  306  is sized to receive an electric heater therein. In the exemplary embodiment, bolt  302  is fabricated from at least one of, but is not limited to being fabricated from, an alloy steel, a metallic material, a plastic material, and/or any combination thereof. In an alternative embodiment, portions  308 ,  310 ,  312 ,  314 ,  316  are independently formed and subsequently coupled together. 
         [0023]    In the exemplary embodiment, first portion  308  extends from a first end  317  to an opposite second end  320 , and has a substantially cylindrical shape defined by an outer diameter  322 . First portion  308  is also defined by an inner diameter  324 . In an alternative embodiment, first portion  308  may be formed with any suitable shape that enables bolt assembly  300  to function as described herein. 
         [0024]    In the exemplary embodiment, second portion  310  extends from a first end  326  adjacent first portion second end  320  to an opposite second end  328 . Second portion  310  is substantially cylindrical and has an outer diameter  330  that is approximately equal to first portion inner diameter  324 . As such, the outer diameter  330  of second portion  310  is smaller than the outer diameter  318  of first portion  308 . Moreover, second portion  310  is formed with a groove  332  that is defined within an outer surface  334  of second portion  310 . In the exemplary embodiment, groove  332  extends circumferentially about second portion  310 . 
         [0025]    Groove  332  is sized to receive a retaining ring  342  therein. Second portion  310  and ring  342  are sized to ensure load capacity. Moreover, retaining ring  342  is sized such that a portion of retaining ring  342  extends outward from surface  334  when ring  342  is fully seated within groove  332 . Retaining ring  342  facilitates retaining bolt  302  within flange  208  during assembly, as will be described in more detail below. In the exemplary embodiment, retaining ring  342  is split and includes a slot  348  that facilitates the assembly of bolt assembly  300 . 
         [0026]    Third portion  312 , in the exemplary embodiment, includes a frusto-conical portion  350  and a substantially cylindrical portion  352 . Frusto-conical portion  350  includes a first end  354  formed with a first diameter  356  adjacent second portion second end  328 , and a second end  358  formed with a second diameter  360 . In the exemplary embodiment, diameter  356  is approximately equal to diameter  330 , and is larger than diameter  360 . As such, frusto-conical portion  350  tapers inward from first end  354  to second end  358 . Cylindrical portion  352  is formed with an outer diameter  360  that is substantially constant from a first end  362 , adjacent frusto-conical second end  358 , to a second end  364 . In the exemplary embodiment, third portion  312  is configured to be inserted into counterbored opening  210 . 
         [0027]    In the exemplary embodiment, fourth portion  314  is formed with a substantially cylindrical portion  365 , a frusto-conical portion  372 , and a substantially cylindrical portion  374 . Portion  365  has a first end  366  that extends from third portion second end  364  and an opposite second end  368 . Moreover, portion  365  is formed with a substantially constant diameter  370 . In the exemplary embodiment, diameter  370  is larger than third portion diameter  360 . Moreover, fourth portion  314  includes a plurality of threads  373  that extend about an outer surface outer surface  375  of portion  365 . Threads  373  are oriented to engage threads (not shown) defined within nut  304 , as described in more detail below. 
         [0028]    Frusto-conical portion  372  includes a first end  376 , adjacent to second end  368  and formed with a diameter  370 , and a second end  380  formed with a second diameter  381  that is smaller than diameter  370 . As such, frusto-conical portion  372  tapers from first end  376  to second end  380 . Portion  374  has substantially constant diameter  381  from a first end  382 , adjacent second end  380 , to a second end  383 . 
         [0029]    Fifth portion  316  has a first end  386  adjacent to fourth portion second end  380 , and an opposite second end  388 . In the exemplary embodiment, fifth portion  316  has a substantially hexagonal cross-sectional profile. Specifically, fifth portion  316  includes a plurality of wrench flats that facilitate assembly of bolt assembly  300 . Alternatively, fifth portion  316  may have any non-hexagonal shape that enables bolt assembly  300  to function as described herein. 
         [0030]    In the exemplary embodiment, nut  304  is sized and shaped to threadably couple to bolt  302 . Nut  304  extends from a first side  390  to an opposite second end  392  and includes a bore  393  extending therebetween. Nut  304  is substantially cylindrical and has an inner diameter  391  and an outer diameter  394 . In the exemplary embodiment, bore diameter  391  is sized to enable nut  304  to engage bolt fourth portion  314 . As such, nut  304  includes a plurality of threads  395  formed within an inner surface  397  of nut  304 . 
         [0031]    In the exemplary embodiment, nut second end  392  includes a plurality of radial slots  396  that are oriented to enable a wrench to engage nut  304  during assembly of bolt assembly  300 . Moreover, nut  304  also includes a groove  398  that extends circumferentially about an outer surface  399  of nut  304 . Alternatively, nut  304  may be formed with any suitable shape and/or size that enables bolt assembly  300  to function as described herein. 
         [0032]      FIG. 4  is a perspective view of a first alternative bolt assembly  500  that may be used with shell casing  200 . As shown in  FIG. 4 , bolt assembly  500  is similar to bolt assembly  300  and like components are identified with like reference numerals.  FIG. 4  includes a bolt  502  that is similar to bolt  302  and like components are identified with like reference numerals. 
         [0033]    Bolt  502  does not include groove  332  defined within outer surface  334  of second portion  310 . As such, a retaining ring  342  is not coupled within groove  332 . Rather, bolt  502  includes an opening  532  defined therein. Specifically, bolt  502  includes opening  352  defined within portion  310  such that opening  532  extends diametrically through portion  310 . Opening  532  is configured to receive a radial pin  542  therein. Radial pin  542  is sized such that a portion of radial pin  542  extends outward from surface  334  when radial pin  542  is positioned within opening  352 . Radial pin  542  facilitates retaining bolt  502  within flange  208  during assembly similar to retaining ring  342 . 
         [0034]      FIG. 5  is a perspective view of a second alternative bolt assembly  600  that may be used with shell casing  200 . As shown in  FIG. 5 , bolt assembly  600  is similar to bolt assembly  300  and like components are identified with like reference numerals.  FIG. 5  includes a bolt  602  that is similar to bolt  302  and like components are identified with like reference numerals. 
         [0035]    Bolt  602  does not include groove  332  defined within outer surface  334  of second portion  310 . As such, a retaining ring  342  is not coupled within groove  332 . Rather, bolt  602  includes a plurality of threads  632  defined therein. Specifically, threads  632  are defined along surface  334  of portion  310  and are configured to engage a nut (not shown). The nut is sized to facilitate retaining bolt  602  within flange  208  during assembly. 
         [0036]      FIG. 6  illustrates a perspective view of bolt assembly  300  in a partially assembled configuration  402 .  FIG. 7  is a perspective view of bolt assembly  300  in a fully assembled configuration  404 . During assembly, bolt  302  is inserted into flange opening  212  in an upward direction  397 . Bolt second end  303  is inserted from surface  213  through opening  212  such that a portion of bolt  302  extends a distance above surface  211 . When bolt  302  is within opening  212 , bolt second end  320  contacts flange surface  213  and second portion  310  is received within opening  212 . In the exemplary embodiment, retaining ring  342  is then coupled within groove  332  to facilitate retaining bolt  302  within opening  212 . Specifically, a portion of retaining ring  342  extending outward from portion  310  engages first surface  211 , and prevents bolt  302  from falling out of opening  212  during assembly. Retaining ring  342  is sized to ensure load capacity and effectively “hold” bolt  302  within opening  212  during assembly. 
         [0037]    In the first alternative embodiment, radial pin  542  is inserted at least partially through opening  532  such that a portion of radial pin  542  extends diametrically through bolt  502 . Specifically, at least a portion of radial pin  542  extends outward from surface  334  of portion  310  to engage first surface  211  of flange  208  and to prevent bolt  502  from falling out of opening  212  during assembly. 
         [0038]    In the second alternative embodiment, the second portion nut is threadably coupled to at least a portion of threads  632  to facilitate retaining bolt  602  within opening  212 . Specifically, a portion of second portion nut engages first surface  211  and prevents bolt  602  from falling out of opening  212  during assembly. 
         [0039]    Each opening  214  defined within casings  202  and  204  receives a dowel therein that facilitates the assembly of shell casing. Specifically, as upper casing  202  is coupled to casing  204 , dowels facilitate aligning casing  202  and  204 . Moreover, while coupling casing  202  to casing  204 , bolt  302  is inserted into flange opening  210 . Specifically, bolt end  303  is inserted into flange opening  210  in upward direction  397  until bolt  302  extends upward a distance from surface  207  of flange  206 . Inserting bolt  302  into opening  210  and  212  in an upward direction eases assembly. 
         [0040]    When bolt  302  is inserted through both casings  202  and  204 , nut  304  is threadably coupled to bolt  302  coupling flanges  206  and  208  together. Specifically, nut  304  is threadably coupled to bolt portion  314 . Bolt end  303  is inserted into nut opening  393 , and nut  304  is rotated to tighten nut  304  to bolt  302 . More specifically, at least one wrench (not shown) engages bolt portion  316  to prevent bolt  302  from rotating within openings  210  and  212 . At least one wrench (not shown) engages nut slots  396  to rotate nut  304  with respect to stationary bolt  302  to couple nut  304  to bolt  302 . As such, both wrenches are utilized on a single end of bolt  302 . The two wrenches facilitate ensuring that nut  304  is properly tightened with an amount of torque that does not shred threads  373  and/or  395  and/or that does not adversely affect the structural integrity of bolt  302  and nut  304 . To facilitate assembly of bolt assembly  300 , heat may be applied into opening  306  to heat bolt  302  causing bolt  302  to thermally expand. Second portion  310  is sized to absorb most of the load applied to bolt  302  during thermal expansion. When bolt  302  cools, nut  304  is securely coupled to bolt  302 . 
         [0041]    During operation of steam turbine engine  100 , bolt assembly  300  secures casing  202  and  204  together via flanges  206  and  208 . When steam turbine engine  100  is not in operation, nut  304  may be removed from bolt  302 , and bolt  302  removed from flanges  206  and/or  208 . Moreover, bolt assembly  300  may be used in various engines and/or machines including a pair of flanges. 
         [0042]    Described herein is a bolt assembly that may be used on a wide variety of engine assemblies and casings. The bolt assembly described herein uses an integrally formed bolt having a threaded portion configured to receive a threaded nut. The bolt assembly is configured to be inserted in an upward direction enabling a pair of flanges to be coupled together. A groove, an opening, and/or a plurality of threads are formed within a portion of the bolt such that the groove, the opening, and/or the plurality of threads are configured to receive a retaining ring, a radial pin, and/or a nut to ease assembly. The retaining ring, radial pin, and/or nut prevent the bolt from slipping and/or falling out of the flange opening during assembly. 
         [0043]    Furthermore, the above-described assembly enables the nut to be threadably coupled to the bolt utilizing only one end of the bolt. Specifically, at least one first wrench engages a first end of the bolt to prevent the bolt from rotating within the flange openings, and at least one second wrench engages a portion of the nut to couple the nut to the first end of the bolt. The configuration of the bolt assembly enables the bolt assembly to be coupled within the flange openings when space constraints are present. Moreover, the configuration of the nut and bolt assembly enables the nut to be coupled and tightened to the bolt with an amount of torque that does not shred the threads defined within the bolt and/or within the nut. The above-described bolt assembly improves the assembly of steam turbine engines with a low cost modification. 
         [0044]    An exemplary embodiment of a bolt assembly for an engine assembly is described above in detail. The bolt assembly illustrated is not limited to the specific embodiments described herein, but rather, components of each assembly may be utilized independently and separately from other components described herein. 
         [0045]    While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.