Abstract:
A rotary machine and a method of assembling a rotary machine having a casing extending at least partially around a rotor are provided. The method includes providing a diaphragm patch ring. The method also includes assembling a diaphragm assembly by configuring a diaphragm bore portion to receive the diaphragm patch ring and forming a diaphragm patch member sub-assembly by coupling the diaphragm patch ring to the configured diaphragm bore portion, such that the diaphragm bore portion defines at least one dowel passage and at least one bolt passage. The method further includes inserting at least one dowel generally radially into the at least one dowel passage, inserting at least one fastening bolt generally radially into the at least one bolt passage to secure the diaphragm patch ring to the diaphragm bore portion, and positioning the diaphragm assembly in a gap formed by the casing and the rotor.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to rotary machines and more particularly, to diaphragm patch rings for use in a rotary machine. 
   At least some steam turbines have a defined steam path which includes, in serial-flow relationship, a steam inlet, a turbine, and a steam outlet. Many of these steam turbines include stationary nozzle segments that direct a flow of steam towards rotating buckets, or turbine blades, that are coupled to a rotatable member. The nozzle airfoil construction is typically called a diaphragm assembly. Each diaphragm assembly is usually referred to as a stage and most steam turbines have a configuration that includes a plurality of diaphragm assembly stages. 
   Steam leakage, either out of the steam path or into the steam path, from an area of higher pressure to an area of lower pressure may adversely affect an operating efficiency of the turbine. For example, steam-path leakage in the turbine between a rotating rotor shaft of the turbine and a circumferentially surrounding turbine casing may lower the efficiency of the turbine. Additionally, steam-path leakage between a shell and the portion of the casing extending between adjacent turbines may reduce the operating efficiency of the steam turbine and over time, may lead to increased fuel costs. 
   In addition to facilitating steam flow, to facilitate minimizing steam-path leakage as described above, at least some known steam turbines use a plurality of labyrinth seals that are integral to the diaphragm assemblies. The seals are typically ring segments that are inserted into circumferential grooves at the radially innermost section of the diaphragm assembly, often referred to as a bore. Some known labyrinth seals include longitudinally spaced rows of labyrinth seal teeth which are used to seal against pressure differentials that may be present in the steam turbine. 
   Some steam turbine maintenance activities periodically include reducing the associated rotor diameters for a variety of reasons that include accommodating new features such as longer buckets, enhancing rotor stability, and/or mitigating rotor thrust values. In some of these instances, it is desirable to retain and reuse the existing diaphragm assemblies. In the event that the aforementioned seals alone cannot be modified to accommodate the extended gap between the diaphragm assemblies and the rotor, the existing diaphragm may be modified such that the bore of the diaphragm assembly and associated seals can mate with the reduced rotor diameter. In those steam turbine configurations where sufficient radial space exists, welding a diaphragm extension to existing diaphragms may suffice. Furthermore, alternative methods of extension attachment may be considered, such as for example, coupling extensions to existing diaphragms with a dowel-type configuration. However, in some known steam turbines, sufficient space for the aforementioned welding and dowel configurations may not be present and a low-profile, self-supporting configuration may be a solution. 
   BRIEF DESCRIPTION OF THE INVENTION 
   In one aspect, a method of assembling a rotary machine having a casing extending at least partially around a rotor is provided. The method includes providing a diaphragm patch ring. The method also includes assembling a diaphragm assembly by configuring a diaphragm bore portion to receive the diaphragm patch ring and forming a diaphragm patch member sub-assembly by coupling the diaphragm patch ring to the configured diaphragm bore portion. The method further includes positioning the diaphragm assembly in a gap formed by the casing and the rotor. 
   In another aspect, a diaphragm assembly for a steam turbine is provided. The assembly includes a substantially annular radially inner member configured to extend substantially circumferentially within the steam turbine. The assembly also includes a substantially annular diaphragm patch member sub-assembly configured to extend substantially circumferentially within the steam turbine. The sub-assembly includes a substantially annular diaphragm patch ring and the diaphragm patch member sub-assembly is coupled to the inner member. 
   In a further aspect, a rotary machine is provided. The machine includes at least one rotor and at least one stationary machine casing extending at least partly circumferentially around the rotor such that a clearance gap is defined between the rotor and the casing. The machine also includes at least one diaphragm assembly. The diaphragm assembly is positioned within the clearance gap defined between the rotor and the stationary machine casing. The diaphragm assembly includes a substantially annular radially inner member configured to extend substantially circumferentially within the rotary machine. The assembly also includes a substantially annular diaphragm patch member sub-assembly configured to extend substantially circumferentially within the rotary machine. The sub-assembly includes a substantially annular diaphragm patch ring. The diaphragm patch member sub-assembly is coupled to the inner member. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a schematic illustration of an exemplary opposed flow steam turbine engine; 
       FIG. 2  is a schematic side perspective of a portion of the steam turbine engine in  FIG. 1 ; 
       FIG. 3  is a schematic axial perspective of an exemplary diaphragm assembly prior to modification that may be used with the steam turbine engine in  FIG. 1 ; 
       FIG. 4  is a schematic side perspective of a portion of the diaphragm assembly in  FIG. 3  prior to modification; 
       FIG. 5  is an expanded side perspective of the diaphragm assembly bore portion in  FIG. 4  prior to modification; 
       FIG. 6  is a side perspective of the exemplary bore portion in  FIG. 5  machined to receive a diaphragm patch ring; 
       FIG. 7  is a side perspective of an exemplary diaphragm patch member sub-assembly that has the modified bore portion in  FIG. 6 ; 
       FIG. 8  is a schematic side perspective of a portion of a diaphragm assembly that has received the exemplary diaphragm patch member sub-assembly in  FIG. 7 ; and 
       FIG. 9  is a schematic axial perspective of the exemplary diaphragm assembly after modification that may be used with the steam turbine engine in  FIG. 1 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     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 outer shell, or casing,  106  is divided axially into upper and lower half sections  108  and  110 , respectively. Similarly, an IP outer shell  112  is divided axially into upper and lower half sections  114  and  116 , respectively. A central section  118  positioned between HP section  102  and IP section  104  has a high pressure steam inlet  120  and an intermediate pressure steam inlet  122 . Within casings  106  and  112 , HP section  102  and IP section  104 , respectively, are arranged in a single bearing span supported by journal bearings  126  and  128 . Steam seal units  130  and  132  are located inboard of each journal bearing  126  and  128 , respectively. 
   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  defined in a packing casing  144 . More specifically, channel  142  is a C-shaped channel that extends radially into packing casing  144  and around an outer circumference of packing casing  144 , such that a center opening of channel  142  faces radially outwardly. 
   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 has a corresponding diaphragm 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 buckets and diaphragm assemblies (not shown in  FIG. 1 ). 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 . One such leakage path may be defined extending through packing casing  144  axially along rotor shaft  140 . 
   It should be noted that although  FIG. 1  illustrates an opposed-flow high pressure and intermediate pressure steam turbine combination, as will be appreciated by one of ordinary skill in the art, the present invention is not limited to being used with high pressure and intermediate pressure turbines and can be used with any individual turbine or multiple turbine combinations as well, including, but not limited to low pressure turbines. In addition, the present invention is not limited to being used with opposed flow and double flow turbines, but rather may be used with single flow steam turbines as well. 
     FIG. 2  is a schematic side perspective of a portion of IP section  104  of steam turbine engine  100  (shown in  FIG. 1 ). Section  104  includes upper half casing  114  that is bolted to lower half casing  116  (not shown in  FIG. 2 ) when section  104  is fully assembled. A nozzle carrier top half  150  mates to radially inner surfaces of casing  114  such that carrier  150  acts as a radial inward extension of casing  114 . Such mating facilitates maintaining nozzle carrier  150  in a substantially fixed position with respect to turbine rotor  140 . Nozzle carrier  150  facilitates substantially fixed support for nozzle  138  as well as diaphragm assemblies  152  via substantially annular diaphragm grooves  153 . A nozzle carrier bottom half (not shown in  FIG. 2 ) is coupled to lower half casing  116  and receives nozzle  138  and assemblies  152  in a manner similar to carrier top half  150 . Rotatable turbine blades, or buckets  154  are coupled to rotor  140 . 
   Steam enters section  104  via IP section steam inlet  122  and is transported through section  104  as illustrated by the arrows. Inlet nozzle  138  and diaphragm assemblies  152  facilitate directing steam flow to buckets  154 . Diaphragm assemblies  152  also facilitate mitigation of steam flow losses from the primary steam flow path of nozzle-to-bucket-to-nozzle, etc. via an axial gap  156  formed between a radially innermost portion of diaphragm assemblies  160  and a rotor surface  158 . Diaphragm assemblies  152  are discussed further below. 
     FIG. 3  is a schematic axial perspective of an exemplary diaphragm assembly  152  prior to modification that may be used with steam turbine engine  100  (shown in  FIG. 1 ), and  FIG. 4  is a schematic side perspective of a portion of diaphragm assembly  152  prior to modification. In one embodiment, diaphragm assembly  152  is a last stage diaphragm assembly  152  of turbine engine  100 . Diaphragm assembly  152  has a substantially annular outer member that is inserted into similarly shaped grooves formed within nozzle carrier  150 . In the exemplary embodiment, assembly  152  is formed of two substantially identical portions (not shown in  FIG. 3 ) and forms a unitized assembly  152  when both portions are inserted. Typically, assembly  152  is formed from at least two half-sections that are “rolled” into diaphragm grooves  153  (shown in  FIG. 2 ) and are split at a horizontal centerline formed between the “9 O&#39;clock” and “3 O&#39;clock” positions. This line is illustrated with the horizontal dotted line shown in  FIG. 3 . 
   Assembly  152  also has a plurality of nozzles  166  that facilitate steam flow through engine  100  as discussed above. Assembly  152  further has a substantially annular inner member  160  that includes a radially innermost portion  168 , referred to as a bore portion, or bore. Bore portion  168  forms a substantially annular groove  170  that extends substantially circumferentially within steam turbine engine  100  and is configured to receive a substantially arcuate seal ring segment  172 . Nozzles  166  are spaced circumferentially between members  160  and  164  and each extends substantially radially between inner and outer members  160  and  164 , respectively. Turbine rotor shaft  140  with centerline  162  and rotor surface  158 , and gap  156  formed by segment  172  and rotor surface  158  are illustrated in  FIG. 3  for perspective.  FIG. 4  illustrates a portion of assembly  152  with a dotted line and is labeled “ 5 ” that is expanded in  FIG. 5  and discussed further below. 
     FIG. 5  is an expanded side perspective of diaphragm assembly bore portion  168  in  FIG. 4  prior to modification. Groove  170  is at least partially formed via at least one radially outermost surface  174  and groove radially innermost surface  176 . 
     FIG. 6  is a side perspective of modified bore portion  178  that is bore portion  168  machined to receive a diaphragm patch ring (not shown in  FIG. 6 ). Portion  168  is machined using techniques well known in the art to remove groove  170  (shown in  FIG. 5 ). At least one surface  174  is machined to be substantially coplanar with surface  176  (both shown in  FIG. 5 ) to form at least one substantially annular radially inner mating surface  180 . Additional machining may be used to facilitate receipt of a diaphragm patch ring, for example, machining portion  178  to form a substantially annular axially upstream groove  182  and a substantially annular axially downstream groove  184  such that they form a protrusion, or tongue  186  portion for a “tongue and groove” configuration as discussed further below. Alternatively, inner member  160  that has modified bore portion  178  may be formed by casting. 
     FIG. 7  is a side perspective of a diaphragm patch member sub-assembly  200  that has modified bore portion  178  with substantially annular radially inner mating surface  180 . At least a portion of each of a plurality of open passages that will eventually form dowel passages  202  and bolt passages  204  are machined substantially radially into modified bore portion  178  from surface  180 . Passages  202  and  204  will be fully formed when a machined diaphragm patch ring  206  is coupled to portion  178  as, discussed further below. Modified bore portion  178  also has grooves  182  and  184  forming tongue-like protrusion  186  as discussed above. 
   Diaphragm patch ring  206  may be formed by machining a cast member, a forged member, or a plate (none of which are shown in  FIG. 7 ) to a set of predetermined dimensions. Ring  206  is substantially annular with a substantially annular axially upstream protrusion  208 , at least one substantially annular mating surface  210  and a substantially annular axially downstream protrusion  212 . Protrusions  208  and  212  in cooperation with at least one surface  210  form the groove portion  213  of the tongue and groove configuration discussed further below. Furthermore, protrusions  208  and  212  are sized to account for the upstream pressure in region  214  acting on protrusion  208  being greater than the downstream pressure in region  216  acting on protrusion  212 . This configuration tends to mitigate any potential axial displacement of ring  206  due to the differential pressure acting axially on ring  206 . 
   A substantially annular seal ring groove  218  with a substantially annular radially outermost surface  220  is formed within patch ring  206 . At least a portion of each of a plurality of open passages that will eventually form dowel passages  202  and bolt passages  204  are machined substantially radially into ring  206  extending from surface  210  to surface  220 . Passages  202  and  204  are machined with dimensions and with spacing substantially similar to those for modified bore portion  178 . 
   As discussed above, the method of forming diaphragm assembly  152  with two half sections applies to sub-assembly  200 . Sub-assembly  200  is assembled by positioning a section of ring  206  against a section of modified bore portion  178  such that the mating surfaces  180  and  210  are in contact and passages  202  and  204  formed in bore  178  and ring  206  are in substantially radial alignment such that they may receive the associated fasteners of which bolt  224  is illustrated and dowels are not illustrated. In other words, groove  213  formed in ring  206  is rolled over tongue  186  formed in modified bore portion  178 . The tongue and groove configuration formed by ring  206  and bore  178  serves to mitigate any potential axial displacement of ring  206  due to the aforementioned differential pressure acting axially on ring  206  as described above. 
   In the exemplary embodiment, the predetermined dimensions of tongue  186  and groove  213  are such that a contact friction fit between the two components is effected wherein the upstream portion of tongue  186  and protrusion  208  provide substantially most of the coupling force for coupling ring  206  to bore portion  178 . In operation, as steam is admitted to steam turbine  100  and bore portion  178  and ring  206  expand as heated causing the coupling force between ring  206 , bore portion  178  to increase. In this manner, a low-profile, self-supporting configuration for sub-assembly  200  is provided. When steam turbine  100  is removed from service and ring  206  and bore portion  178  are cooled, sufficient coupling force between ring  206  and bore portion  178  is maintained. 
   At least one bolt  224  is inserted generally radially into at least one bolt passage  204  to fixedly couple ring  206  to bore portion  178 . At least one dowel (not shown in  FIG. 7 ) is inserted generally radially into at least one dowel passage  202  to facilitate axial, radial and circumferential alignment as well as to facilitate mitigating any potential for circumferential displacement due to torsional forces that may develop from, for example, steam forces acting on seal ring segment  172  or steam swirl in the vicinity of nozzles  166  (shown in  FIG. 4 ). Sealing caps  222  are inserted into passages  202  and  204  at surface  220  to mitigate any potential for bolt  224  or dowel release from associated passages  202  and  204 , respectively. Typically, a friction fit for caps  222  is sufficient, however, additional means of securing caps  222  within passages  202  and  204 , such as sealants or tack welding, may be used. 
   In the exemplary embodiment, bolts  224  and the dowels provide a coupling force to cooperate with the aforementioned friction fit force between protrusion  208  and tongue  186  to carry the load associated with sub-assembly  200 . Alternatively, the predetermined dimensions of tongue  186  and groove  213  may be formed such that bolts  224  and the dowels merely provide captivation and alignment between ring  206  and bore portion  178  and the number of bolts  224  and dowels may be reduced or eliminated. 
   Further alternatively, passages  202  and the associated dowels may be eliminated for protrusions  208  and  212  and tongue  186  being keyed, notched or having lipped protrusions added to perform the function of mitigating circumferential displacement. 
   Also illustrated in  FIG. 7  are seal ring segment  172 , modified rotor  226 , rotor surface  228  and gap  230  formed by rotor surface  228  and seal teeth  232 . Rotor  226  has a smaller diameter than rotor  140  (shown in  FIG. 3 ). Gap  230  and teeth  232  are a portion of a labyrinth seal system that mitigates steam flow along surface  228  from high pressure region  214  to low pressure region  216  as illustrated by the arrows. 
     FIG. 8  is a schematic side perspective of a portion of modified diaphragm assembly  250  that has received diaphragm patch member sub-assembly  200 . Assembly  250  has a modified inner member  252  that has modified bore portion  178 . Outer member  164  and nozzle  166  are substantially similar to those components associated with pre-modified diaphragm assembly  152  (shown in  FIG. 4 ). 
     FIG. 9  is a schematic axial perspective of an exemplary diaphragm assembly  250  after modification that may be used with steam turbine engine  100  (shown in  FIG. 1 ). As discussed above, forming diaphragm assembly  152  with two half sections logically applies to assembly  250  as well. Typically, a top half section of assembly  250  is rolled into substantially annular diaphragm groove  153  formed within nozzle carrier  150  (both shown in  FIG. 2 ). Similarly, a bottom half section is inserted into carrier  150 . At least one dowel  256  is inserted generally radially into passage  202  to facilitate axial, radial and circumferential alignment as well as to mitigate any potential for circumferential displacement as discussed above. 
     FIG. 9  also illustrates the exemplary embodiment for the number of and placement of dowel passages  202  and bolt passages  204  as well as the associated bolts  224  (shown in  FIG. 7 ) and dowels  256 . Alternatively, the dimensions of, the number of and the positioning of these components may be determined based on the dimensions of turbine engine  100 . 
   Assembly  250  further has machined bore portion  178  coupled to diaphragm patch ring  206  as discussed above. Seal ring segment  172  is inserted into seal ring groove  218 . Rotor  226  with rotor surface  228  and axial centerline  162  are illustrated for perspective. Gap  230  is formed between surface  28  and seal ring segment  172 . 
   The methods and apparatus for a fabricating a turbine diaphragm assembly described herein facilitates operation of a turbine system. More specifically, the turbine diaphragm assembly as described above facilitates a more robust turbine steam seal configuration. Such steam seal configuration also facilitates efficiency, reliability, and reduced maintenance costs and turbine system outages. 
   Exemplary embodiments of turbine diaphragm assemblies as associated with turbine systems are described above in detail. The methods, apparatus and systems are not limited to the specific embodiments described herein nor to the specific illustrated turbine diaphragm assembly. 
   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.