US20150159512A1

US20150159512A1 - Method and system for use in cooling a joint flange bolt of a rotary machine

Info

Publication number: US20150159512A1
Application number: US14/097,489
Authority: US
Inventors: Sanjeev Kumar Chandriki; Mukil Kundram
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 2013-12-05
Filing date: 2013-12-05
Publication date: 2015-06-11

Abstract

A method of cooling at least one joint flange bolt used with a rotary machine includes extracting a working fluid having a first temperature that is lower than an operating temperature at a first joint flange bolt hole. The method also includes diverting a first portion of the extracted working fluid into a first supply hole that is in flow communication with a first clearance gap defined between the first joint flange bolt hole and the joint flange bolt. The method further includes exhausting the first portion of extracted working fluid through a first exhaust hole in flow communication with the first clearance gap, such that the first portion of extracted working fluid flows around the exterior surface of the joint flange bolt. Additionally, the method includes routing the first portion of the extracted working fluid into a first conduit in flow communication with the first exhaust hole.

Description

BACKGROUND

The field of the disclosure relates generally to cooling a casing of a rotary machine, and more particularly to a method of cooling a casing joint flange bolt of a rotary machine.
At least some known rotary machines, including some known steam turbines, are housed within a casing that is generally shaped like a horizontal tube, formed by an upper section and a lower section. In at least some such known rotary machine casings, the section and lower sections of the casing are coupled together along a pair of horizontal joints that extend axially along each side of the generally tubular casing. The upper and lower sections of the casing may each include a flange that extends along each joint and that includes aligned bolt holes defined at several locations in each upper and lower flange. Bolts may be installed in these joint flange bolt holes to couple the casing sections together. The bolts may need to maintain a fastening torque at or above a required level to ensure that the upper and lower sections of the casing remain properly sealed.
High temperatures existing within at least some known rotary machines, such as near an inlet and an upstream end of some known steam turbines, may lead to a correspondingly increased temperature in the joint flange and the joint flange bolts. The increased temperatures may cause the joint flange bolts to suffer increased “creep relaxation,” that is, a loss of bolt fastening torque over time. To maintain the fastening torque at or above the required level in the presence of increased joint flange bolt temperatures, some known joint flange bolts are formed with a larger diameter, and/or are fabricated from a harder material (such as a nickel-chromium-based superalloy), than would otherwise be necessary. As such, the costs associated with these joint flange bolts may be higher than for other known bolts.
Some known rotary machines have attempted to provide cooling of joint flange bolts. In at least some known rotary machines, vertical pipes have been installed in the insulation covering the horizontal joint flange. The pipes are adjacent to the edge of the joint flange near each bolt hole. The bottom and top of each pipe are open to the ambient air, which flows up through the pipes via natural convection, and this cools convectively the edge of the flange and areas near the bolts. However, because the primary cooling is performed on the joint flange, rather than on the bolts themselves, the benefits of such cooling are limited.
In some other known rotary machines, holes have been bored through the joint flange bolts to provide for the flow of a cooling fluid directly through the bolt. While this method provides cooling directly to each bolt, rather than indirectly through the joint flange, it introduces the manufacturing difficulty of boring holes through hardened bolts. In addition, some joint flange bolts again may need to have a larger diameter, and/or be made of a harder material, than would otherwise be necessary due to the removal of material from the interior of the bolts.

BRIEF DESCRIPTION

In one aspect, a method of cooling at least one joint flange bolt used with a rotary machine is provided. The method includes extracting working fluid having a first temperature and a first pressure from a location of the rotary machine. The first temperature is lower than an operating temperature at a first joint flange bolt hole defined in a casing of the rotary machine. The method also includes diverting a first portion of the extracted working fluid into a first supply hole defined in a lower section of the casing. The first supply hole is in flow communication with a first clearance gap defined between an interior surface of the first joint flange bolt hole and an exterior surface of the joint flange bolt installed in the first joint flange bolt hole. The method further includes exhausting the first portion of extracted working fluid through a first exhaust hole defined in an upper section of the casing. The first exhaust hole is in flow communication with the first clearance gap, such that the first portion of extracted working fluid flows around the exterior surface of the joint flange bolt. Additionally, the method includes routing the first portion of the extracted working fluid into a first conduit in flow communication with the first exhaust hole, such that a first flow path is defined from the working fluid extraction location of the rotary machine, through the first clearance gap and first exhaust hole, to the first conduit.
In another aspect, a system for cooling at least one joint flange bolt of a rotary machine is provided. The system includes an extraction bore defined through a casing of the rotary machine, and the extraction bore is configured to be in flow communication with a working fluid having a first temperature and a first pressure when the rotary machine is in operation. The first temperature is lower than an operating temperature at a first joint flange bolt hole defined in the casing. The system also includes a second conduit in flow communication with the extraction bore and a first supply hole defined in the casing. The first supply hole is in flow communication with the second conduit, and also in flow communication with a first clearance gap defined between an interior surface of the first joint flange bolt hole and an exterior surface of the joint flange bolt when the joint flange bolt is installed in the first joint flange bolt hole. The system further includes a first exhaust hole defined in the casing. The first exhaust hole is in flow communication with the first clearance gap. Additionally, the system includes a first conduit in flow communication with the first exhaust hole, such that a first flow path is defined from the extraction bore, through the second conduit, through the first clearance gap and the first exhaust hole, to the first conduit.
In yet another aspect, a rotary machine is provided. The rotary machine includes a casing having an extraction bore and a first joint flange bolt hole. The extraction bore is configured to be in flow communication with a working fluid having a first temperature and a first pressure when the rotary machine is in operation. The first temperature is lower than an operating temperature at the first joint flange bolt hole. The rotary machine also includes a second conduit in flow communication with the extraction bore and a first supply hole defined in the casing. The first supply hole is in flow communication with the second conduit, and also in flow communication with a first clearance gap defined between an interior surface of the first joint flange bolt hole and an exterior surface of a first joint flange bolt when the first joint flange bolt is installed in said first joint flange bolt hole. The rotary machine further includes a first exhaust hole defined in the casing. The first exhaust hole is in flow communication with the first clearance gap. Additionally, the system includes a first conduit in flow communication with the first exhaust hole, such that a first flow path is defined from the extraction bore, through the second conduit, through the first clearance gap and the first exhaust hole, to the first conduit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of an exemplary steam turbine engine;

FIG. 2 is a simplified perspective view of an exemplary casing that may be used with the exemplary steam turbine engine shown in FIG. 1;

FIG. 3 is a schematic cross-section taken along line 3-3 of the exemplary casing shown in FIG. 2;

FIG. 4 is another simplified perspective view of the exemplary casing shown in FIG. 2;

FIG. 5 is a simplified perspective view of another exemplary casing that may be used with the exemplary steam turbine engine shown in FIG. 1;

FIG. 6 is a schematic cross-section taken along line 6-6 of the exemplary casing shown in FIG. 5; and

FIG. 7 is a flow chart of an exemplary method of cooling a joint flange bolt of a rotary machine, such as the exemplary steam turbine shown in FIG. 1.

DETAILED DESCRIPTION

The exemplary methods and systems described herein overcome at least some of the disadvantages associated with known methods of cooling rotary machine horizontal joint flange bolts. The embodiments described herein provide direct cooling of the joint flange bolts without requiring alteration of the structure of the bolts. More specifically, the horizontal joint flange bolt cooling methods and systems described herein include tapping into a working fluid from a downstream location of the rotary machine and routing it directly through the horizontal joint flange bolt holes farther upstream to cool the bolts disposed therein.
FIG. 1 is a schematic view of an exemplary steam turbine engine 10. While FIG. 1 describes an exemplary steam turbine engine, it should be noted that the joint flange bolt cooling methods and systems described herein are not limited to any one particular type of rotary machine. One of ordinary skill in the art will appreciate that the current cooling methods and systems described herein may be used with any rotary machine, including a gas turbine engine, in any suitable configuration that enables such methods and systems to operate as further described herein.
In the exemplary embodiment, steam turbine engine 10 is a single-flow steam turbine engine. Alternatively, steam turbine engine 10 may be any type of steam turbine, such as, without limitation, a low-pressure turbine, an opposed-flow, high-pressure and intermediate-pressure steam turbine combination, a double-flow steam turbine engine, and the like. Moreover, as discussed above, the present invention is not limited to only being used in steam turbine engines and can be used in other turbine systems, such as gas turbine engines.
In the exemplary embodiment, steam turbine engine 10 includes a plurality of turbine stages 12 that are coupled to a rotatable shaft 14. It should be understood that steam turbine engine 10 may include any number of buckets 38 that enables steam turbine engine 10 to operate as described herein. For example, steam turbine engine 10 may include more or fewer buckets 38 than are illustrated in FIG. 1. A casing 16 surrounds the plurality of turbine stages 12 and is divided horizontally into an upper section 18 and a lower section 20 (shown in FIG. 2). Steam turbine engine 10 includes a high pressure steam inlet 22 and a low pressure steam exhaust 24. Shaft 14 extends through casing 16 along a centerline axis 28. Shaft 14 is supported at opposite end portions 30 of shaft 14 by journal bearings (not shown).
During operation, high-pressure and high-temperature steam 40 is channeled from a steam source, such as a boiler or the like (not shown), through HP steam inlet 22 into an inlet 26. From inlet 26, steam 40 is channeled in a downstream direction 32 through casing 16, where it encounters turbine stages 12. Each turbine stage 12 includes a plurality of turbine blades or buckets 38 coupled to shaft 14. As the steam impacts turbine buckets 38, it induces rotation of shaft 14 about centerline axis 28. Thus, thermal energy of steam 40 is converted to mechanical rotational energy by turbine stages 12. Steam 40 exits casing 16 at low pressure steam exhaust 24. Steam 40 may then be channeled to the boiler (not shown), where it may be reheated, or to other components of the system, for example, a low pressure turbine section or a condenser (not shown).
FIG. 2 is a simplified perspective view of an embodiment of casing 16 that may be used as part of exemplary steam turbine engine 10 shown in FIG. 1. In the exemplary embodiment shown in FIG. 2, upper section 18 of casing 16 includes an upper flange 52, and lower section 20 of casing 16 includes a lower flange 54. Upper flange 52 and lower flange 54 meet to form a horizontal joint 50. It should be understood that another horizontal joint 50 is formed on an opposite side of casing 16 (not shown). A plurality of upper flange bolt holes 56 extend through upper flange 52, and a plurality of lower flange bolt holes 58 extend through lower flange 54. Each upper flange bolt hole 56 is configured to align with a corresponding lower flange bolt hole 58 when upper section 18 is positioned for coupling to lower section 20. Each aligned upper flange bolt hole 56 and lower flange bolt hole 58 creates a joint flange bolt hole 60.
Certain embodiments of steam turbine 10 also include a first conduit 62 and a second conduit 64. In the exemplary embodiment shown in FIG. 2, first conduit 62 is adjacent the upper flange 52 and second conduit 64 is adjacent the lower flange 54. First conduit 62 and second conduit 64 each extend generally parallel to downstream direction 32 and each are of hollow construction. In particular, first conduit 62 and second conduit 64 are configured to provide a supply and exhaust of coolant fluid through the plurality of joint flange bolt holes 60.
More specifically, in certain embodiments, second conduit 64 is in flow communication with a plurality of bolt hole coolant supply conduits 76. In the exemplary embodiment shown in FIG. 2, each bolt hole coolant supply conduit 76 includes an external supply conduit 80, and a corresponding coolant supply hole 84 defined within lower flange 54. External supply conduit 80 may be coupled to lower flange 54 by any suitable method, such as, but not limited to, by welding, and may be of any suitable cross-section, such as, but not limited to, tubular. In some embodiments, a coupling method and shape of each external supply conduit 80 is chosen such that the plurality of external supply conduits 80 serve to couple second conduit 64 to lower flange 54. Alternatively, second conduit 64 may be coupled to upper flange 52 or to an external support structure (not shown). Each external supply conduit 80 is in flow communication with second conduit 64, and each coolant supply hole 84 is in flow communication with a corresponding aligned external supply conduit 80. In turn, each coolant supply hole 84 is in flow communication with a corresponding joint flange bolt hole 60.
Similarly, in certain embodiments, first conduit 62 is in flow communication with a plurality of bolt hole coolant exhaust conduits 74. In the exemplary embodiment shown in FIG. 2, each bolt hole coolant exhaust conduit 74 includes an external exhaust conduit 78, and a corresponding coolant exhaust hole 82 defined within upper flange 52. External exhaust conduit 78 may be coupled to upper flange 52 by any suitable method, such as, but not limited to, by welding, and may be of any suitable cross-section, such as, but not limited to, tubular. In some embodiments, a coupling method and shape of each external exhaust conduit 78 is chosen such that the plurality of external exhaust conduits 78 serve to couple first conduit 62 to upper flange 52. In alternative embodiments, first conduit 62 may be coupled to upper flange 52 or to an external support structure (not shown). Each coolant exhaust hole 82 is in flow communication with a corresponding joint flange bolt hole 60, and each coolant exhaust hole 82 also is in flow communication with a corresponding aligned external exhaust conduit 78. In turn, each external exhaust conduit 78 is in flow communication with first conduit 62.
A cross-section taken along line 3-3 of the exemplary embodiment of casing 16 from FIG. 2 is shown in FIG. 3. In FIG. 3, however, a joint flange bolt 90 is installed in joint flange bolt hole 60. When joint flange bolt 90 is installed, at least a portion of joint flange bolt 90 is received within joint flange bolt hole 60. In the exemplary embodiment shown in FIG. 3, a nut 92 is threaded onto a threaded portion 94 of joint flange bolt 90, and a fastening torque of bolt 90 and nut 92 is applied to facilitate a secure coupling of upper section 18 and lower section 20 of casing 16. In alternative embodiments, joint flange bolt hole may not extend completely through lower flange 54, and a portion of joint flange bolt hole 60 may be threaded to cooperatively receive a threaded portion of bolt 90, such that a fastening torque may be applied to bolt 90 to facilitate a secure coupling of upper section 18 and lower section 20 without the use of a nut 92.
When bolt 90 is installed in joint flange bolt hole 60, a clearance gap 100 is defined between an interior surface 96 of joint flange bolt hole 60 and an exterior surface 98 of joint flange bolt 90. Clearance gap 100 extends circumferentially about bolt 90. In some embodiments, a width 102 of clearance gap 100 is between about 0.18 inches and about 0.25 inches. In other embodiments, width 102 may be less than 0.18 inches or more than 0.25 inches. Clearance gap 100 is in flow communication with coolant supply hole 84 and with coolant exhaust hole 82. After the fastening torque is applied, a tight contact between nut 92 and lower flange 54 facilitates sealing a bottom end 104 of clearance gap 100, and a tight contact between bolt head 91 and upper flange 52 facilitates sealing a top end 106 of clearance gap 100. Additional sealing may be facilitated by any suitable means, such as by a layer of insulation disposed over nut 92 and bolt head 91.
FIG. 4 is another simplified perspective view of the embodiment of casing 16 shown in FIG. 2. In the exemplary embodiment illustrated in FIG. 4, a first end 70 of second conduit 64 is in flow communication with a source 72 of coolant fluid. When steam turbine 10 is in operation, the coolant fluid at source 72 has a first temperature and a first pressure, and the first temperature is lower than an operating temperature at joint flange bolt hole 60. In the embodiment illustrated in FIG. 4, source 72 is an extraction bore 110 defined through a wall of lower section 20 of casing 16 at a downstream location 108 of steam turbine engine 10, where “downstream” is defined as in the downstream direction 32 relative to joint flange bolt hole 60. Extraction bore 110 is in flow communication with an extraction conduit 112, which in turn is in flow communication with first end 70 of second conduit 64. Thus, in certain embodiments, steam 40 (shown in FIG. 1) from downstream location 108 is available as the source 72 of coolant fluid for second conduit 64. In alternative embodiments, source 72 may be working fluid routed through an extraction bore from any location in steam turbine 10 that has a first temperature that is lower than the operating temperature at joint flange bolt hole 60. In still other embodiments, source 72 may be any source of fluid that has a first temperature that is lower than the operating temperature at joint flange bolt hole 60.
With reference to the embodiment shown in FIG. 1 and FIG. 4, a working fluid in a rotary machine, such as steam 40 in steam turbine engine 10, generally decreases in temperature and pressure as it travels downstream and mechanical work is extracted from it through each turbine stage 12. Accordingly, steam 40 extracted from downstream location 108 has a first temperature that is cooler than the operating temperatures encountered by the joint flange bolts at upstream locations in casing 16, particularly at joint flange bolt locations near inlet 26. For example, in some embodiments of steam turbine engine 10, steam 40 may have temperatures greater than approximately 1,150 degrees Fahrenheit at inlet 26, resulting in upstream joint flange bolts encountering temperatures greater than or equal to 1,000 degrees Fahrenheit. Downstream location 108 may be chosen such that steam 40 has a first temperature in a range of about 600 degrees Fahrenheit to about 900 degrees Fahrenheit at extraction bore 110. For example, downstream location 108 may be chosen such that steam 40 has a temperature of about 830 degrees Fahrenheit at extraction bore 110. In other embodiments, downstream location 108, or an alternative source 72 of coolant fluid, may have a first temperature that is less than 600 degrees or greater than 900 degrees Fahrenheit. It should be understood that the exemplary operating conditions listed above do not limit the scope of the invention, and that other embodiments include different operating conditions at inlet 26 and downstream location 108, or alternative source 72.
Steam 40 that has been used for cooling joint flange bolts may be vented or routed to a sink via a second end (not shown) of first conduit 62. The sink has a pressure that is less than the first pressure at source 72. For example, in some embodiments, a second end (not shown) of second conduit 64 may be capped off, and the second end (not shown) of first conduit 62 may be in flow communication with low pressure steam exhaust 24. A lower pressure of steam 40 at low pressure steam exhaust 24, relative to the first pressure of steam at downstream location 108, facilitates a flow of steam 40 from extraction bore 110 through second conduit 64, through clearance gaps 100, through first conduit 62, to low pressure steam exhaust 24, without the need of a forced circulation system such as a pump or fan. However, in alternative embodiments, a forced circulation system may be used.
With reference to FIG. 2, FIG. 3 and FIG. 4, an exemplary flow path for cooling the plurality of joint flange bolts 90 is as follows. A portion of steam 40 at downstream location 108 is extracted through extraction bore 110 and extraction conduit 112 into first end 70 of second conduit 64. A portion of extracted steam 40 is diverted from second conduit 64 into each external supply conduit 80. The portion of extracted steam 40 flows from each external supply conduit 80 into a corresponding supply hole 84. From each supply hole 84, the portion of extracted steam 40 flows into the clearance gap 100 of the corresponding joint flange bolt 90. Steam 40 flows generally upward through each clearance gap 100 and around the exterior surface 98 of the corresponding bolt 90, convectively transferring heat away from bolt 90 and into steam 40. The portion of extracted steam 40 then exits each clearance gap 100 through exhaust hole 82. A sealing effect of bolt head 91 and nut 92 inhibit leakage of steam 40 from the ends of joint flange bolt hole 60. Each portion of extracted steam 40 flows through the corresponding external exhaust conduit 78 into first conduit 62. The recombined extracted steam 40 in first conduit 62 then is routed to a low pressure sink, such as low pressure steam exhaust 24.
FIG. 5 is a simplified perspective view, and FIG. 6 is a cross-section taken along line 6-6 shown in FIG. 5, of an alternative embodiment of first conduit 62 and second conduit 64. In this embodiment, first conduit 62 and second conduit 64 each have a generally half-tubular cross-section. In alternative embodiments, first conduit 62 and second conduit 64 each have any suitable shape. A top edge 118 and a bottom edge 120 of first conduit 62 are sealingly coupled to upper flange 52, and a top edge 114 and a bottom edge 116 of second conduit 64 are sealingly coupled to lower flange 54. The coupling may be done in any suitable fashion, such as, but not limited to, by welding. In this embodiment, each exhaust hole 82 is in flow communication with first conduit 62 without need for intermediate external exhaust conduit 78 (shown in FIG. 2), and each supply hole 84 is in flow communication with second conduit 64 without need for intermediate external supply conduit 80 (shown in FIG. 2). In addition, extraction bore 110 (shown in FIG. 4) is in flow communication with first end 70 of second conduit 64 without need for intermediate extraction conduit 112 (shown in FIG. 4). Apart from these modifications, the coolant flow path in this alternative embodiment is essentially the same as described above for the embodiment shown in FIG. 2 and FIG. 3.
An exemplary method 200 of cooling a joint flange bolt of a rotary machine is illustrated in the flowchart of FIG. 7. Exemplary method 200 includes extracting 202 working fluid, such as steam 40, having a first temperature and a first pressure from a location of the rotary machine, such as downstream location 108, where the first temperature is lower than an operating temperature at joint flange bolt hole 60. It further includes diverting 204 a first portion of the extracted steam 40 into supply hole 84, which is in flow communication with clearance gap 100 defined between interior surface 96 of joint flange bolt hole 60 and exterior surface 98 of joint flange bolt 90 installed in joint flange bolt hole 60. Exemplary method 200 also includes exhausting 206 the first portion of extracted steam 40 through exhaust hole 82, which is in flow communication with clearance gap 100, such that the first portion of extracted steam 40 flows around exterior surface 98 of joint flange bolt 90. Additionally, exemplary method 200 includes routing 208 the first portion of extracted steam 40 into first conduit 62, which is in flow communication with exhaust hole 82, such that a first flow path is defined from the working fluid extraction location of the rotary machine, through clearance gap 100 and exhaust hole 82, to first conduit 62.
Exemplary method 200 also may include routing 210 the exhausted steam 40 to a sink in flow communication with first conduit 62, wherein the sink has a pressure that is lower than the first pressure, such as low pressure steam exhaust 24. It may further include routing 212 the first portion of extracted steam 40 through external exhaust conduit 78 intermediate exhaust hole 82 and first conduit 62. Additionally, exemplary method 200 may include routing 214 extracted steam 40 into second conduit 64 in flow communication with supply hole 84 and routing 216 the first portion of extracted steam 40 through external supply conduit 80 intermediate second conduit 64 and the supply hole 84.
Exemplary embodiments of a method and system for cooling a joint flange bolt of a rotary machine are described above in detail. The embodiments provide advantages in cooling the bolts directly, without the need for boring holes through the bolts and without the need for an external source of coolant fluid or a forced circulation system. The embodiments facilitate a reduction in “creep relaxation” of joint flange bolts, and accordingly facilitate the use of a smaller diameter bolt and/or a bolt of lesser hardness in at least some horizontal joint flange locations.
The methods and systems described herein are not limited to the specific embodiments described herein. For example, components of each system and/or steps of each method may be used and/or practiced independently and separately from other components and/or steps described herein. In addition, each component and/or step may also be used and/or practiced with other assemblies and methods.
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. Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. Moreover, references to “one embodiment” in the above description are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. In accordance with the principles of the invention, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing.

Claims

What is claimed is:

1. A method of cooling at least one joint flange bolt used with a rotary machine, said method comprising:

extracting working fluid having a first temperature and a first pressure from a location of the rotary machine, wherein the first temperature is lower than an operating temperature at a first joint flange bolt hole defined in a casing of the rotary machine;

diverting a first portion of the extracted working fluid into a first supply hole defined in a lower section of the casing, wherein the first supply hole is in flow communication with a first clearance gap defined between an interior surface of the first joint flange bolt hole and an exterior surface of the joint flange bolt installed in the first joint flange bolt hole;

exhausting the first portion of extracted working fluid through a first exhaust hole defined in an upper section of the casing, wherein the first exhaust hole is in flow communication with the first clearance gap, such that the first portion of extracted working fluid flows around the exterior surface of the joint flange bolt; and

routing the first portion of the extracted working fluid into a first conduit in flow communication with the first exhaust hole, such that a first flow path is defined from the working fluid extraction location of the rotary machine, through the first clearance gap and first exhaust hole, to the first conduit.

2. A method in accordance with claim 1, further comprising routing the exhausted working fluid to a sink coupled in flow communication with the first conduit, wherein a pressure of the sink is lower than the first pressure.

3. A method in accordance with claim 2, further comprising routing the exhausted working fluid to a low pressure working fluid exhaust of the rotary machine.

4. A method in accordance with claim 1, further comprising:

diverting a second portion of the extracted working fluid into a second supply hole defined in the lower section of the casing, wherein the second supply hole is in flow communication with a second clearance gap defined between an interior surface of a second joint flange bolt hole and an exterior surface of a second joint flange bolt installed in the second joint flange bolt hole;

exhausting the second portion of extracted working fluid through a second exhaust hole defined in the upper section of the casing, wherein the second exhaust hole is in flow communication with the second clearance gap, such that the first portion of extracted working fluid flows around the exterior surface of the second joint flange bolt; and

routing the second portion of the extracted working fluid into the first conduit, wherein the first conduit is in flow communication with the second exhaust hole, such that a second flow path is defined from the working fluid extraction location of the rotary machine, through the second clearance gap and second exhaust hole, to the first conduit.

5. A method in accordance with claim 1, further comprising routing the first portion of the extracted working fluid through an external exhaust conduit intermediate the first exhaust hole and the first conduit.

6. A method in accordance with claim 1, further comprising routing the extracted working fluid into a second conduit in flow communication with the first supply hole.

7. A method in accordance with claim 6, further comprising routing the first portion of the extracted working fluid through a first external supply conduit intermediate the second conduit and the first supply hole.

8. A system for cooling at least one joint flange bolt of a rotary machine, said system comprising:

an extraction bore defined through a casing of the rotary machine, said extraction bore is configured to be in flow communication with a working fluid having a first temperature and a first pressure when the rotary machine is in operation, wherein the first temperature is lower than an operating temperature at a first joint flange bolt hole defined in the casing;

a second conduit in flow communication with said extraction bore;

a first supply hole defined in the casing, said first supply hole is in flow communication with said second conduit, said first supply hole also is in flow communication with a first clearance gap defined between an interior surface of the first joint flange bolt hole and an exterior surface of the joint flange bolt when the joint flange bolt is installed in the first joint flange bolt hole;

a first exhaust hole defined in the casing, said first exhaust hole is in flow communication with the first clearance gap; and

a first conduit in flow communication with said first exhaust hole, wherein a first flow path is defined from said extraction bore, through said second conduit, through the first clearance gap and said first exhaust hole, to said first conduit.

9. A system in accordance with claim 8, wherein said first conduit also is in flow communication with a sink, wherein a pressure of the sink is lower than the first pressure.

10. A system in accordance with claim 9, wherein the sink comprises a low pressure working fluid exhaust of the rotary machine.

11. A system in accordance with claim 8, further comprising:

a second supply hole defined in the casing, said second supply hole is in flow communication with said second conduit, said second supply hole also is in flow communication with a second clearance gap defined between an interior surface of a second joint flange bolt hole and an exterior surface of a second joint flange bolt when the second joint flange bolt is installed in the second joint flange bolt hole; and

a second exhaust hole defined in the casing, said second exhaust hole is in flow communication with the second clearance gap and said first conduit, wherein a second flow path is defined from said extraction bore, through said second conduit, through the second clearance gap and said second exhaust hole, to said first conduit.

12. A system in accordance with claim 8, further comprising a first external supply conduit disposed intermediate, and in flow communication with, said second conduit and said first supply hole.

13. A system in accordance with claim 8, further comprising a first external exhaust conduit disposed intermediate, and in flow communication with, said first exhaust hole and said first conduit.

14. A rotary machine comprising:

a casing comprising an extraction bore and a first joint flange bolt hole, said extraction bore is configured to be in flow communication with a working fluid having a first temperature and a first pressure when said rotary machine is in operation, wherein the first temperature is lower than an operating temperature at said first joint flange bolt hole;

a second conduit in flow communication with said extraction bore;

a first supply hole defined in said casing, said first supply hole is in flow communication with said second conduit, said first supply hole also is in flow communication with a first clearance gap defined between an interior surface of said first joint flange bolt hole and an exterior surface of a first joint flange bolt when the first joint flange bolt is installed in said first joint flange bolt hole;

a first exhaust hole defined in said casing, said first exhaust hole is in flow communication with the first clearance gap; and

15. A rotary machine in accordance with claim 14, wherein said first conduit also is in flow communication with a sink, wherein a pressure of the sink is lower than the first pressure.

16. A rotary machine in accordance with claim 14, wherein the sink comprises a low pressure working fluid exhaust of said rotary machine.

17. A rotary machine in accordance with claim 14, further comprising:

a second supply hole defined in said casing, said second supply hole is in flow communication with said second conduit, said second supply hole also is in flow communication with a second clearance gap defined between an interior surface of a second joint flange bolt hole and an exterior surface of a second joint flange bolt when the second joint flange bolt is installed in said second joint flange bolt hole; and

a second exhaust hole defined in said casing, said second exhaust hole is in flow communication with the second clearance gap and said first conduit, wherein a second flow path is defined from said extraction bore, through said second conduit, through the second clearance gap and said second exhaust hole, to said first conduit.

18. A rotary machine in accordance with claim 14, further comprising a first external supply conduit disposed intermediate, and in flow communication with, said second conduit and said first supply hole.

19. A rotary machine in accordance with claim 14, further comprising a first external exhaust conduit disposed intermediate, and in flow communication with, said first exhaust hole and said first conduit.

20. A rotary machine in accordance with claim 14, further comprising an extraction conduit intermediate, and in flow communication with, said extraction bore and said second conduit.