Steam turbine and steam valve gear

Abstract

To provide a steam valve device in a shell mount type structure, and a steam turbine which is equipped therewith, and which can use high temperature and high pressure working fluid while increasing the size of a valve bore, for preventing the stay of drain in a chamber of the steam valve device on the lower part side of a steam turbine casing.SOLUTION: In the steam valve device in the shell mount type structure in the embodiment, the upper part side of a steam turbine casing is provided with a first hole for communicating between a first chamber consisting of a first valve element and a first sleeve encircling the same and the downstream side of the first valve element, and the lower part side of the steam turbine casing is provided with a second hole for communicating between a second chamber consisting of a second valve element and a second sleeve encircling the same and the downstream side of the second valve element. Herein, either a drain hole for communicating between the second chamber and a main flow path inside the steam turbine casing or a drain hole for communicating between the second chamber and the outside of the steam turbine casing is provided for discharging drain from the second chamber.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] SUMMARY OF THE DISCLOSURE Embodiments of the present invention relate to steam turbines and steam valve arrangements. [Background technology]

[0002] In recent years, there has been a demand for more efficient and less costly thermal power generation facilities, and this has created a need not only for more efficient and less costly steam turbines, but also for their associated steam valve gear.

[0003] Steam valve gear that adjusts the steam flow rate supplied to the steam turbine casing of a thermal power plant, etc., includes a shell-mounted structure in which the valve gear is directly attached to the top and bottom of the steam turbine casing. For example, this type of valve gear includes a steam valve gear that is configured with a total of four valves by attaching valve casings to the vertically upper and lower sides of the steam turbine casing and incorporating two steam valves in each valve casing.

[0004] Comparing the shell mount type structure with the separate installation type, which is installed at a location away from the steam turbine, the shell mount type structure, which does not have a lead pipe connecting the steam valve device to the steam turbine casing, has the advantage of having fewer parts and lower manufacturing costs. Furthermore, the shell mount type structure has no pressure loss due to the lead pipe, so it is expected to be more efficient.

[0005] However, in recent years, high-temperature, high-pressure steam has come to be used as the working fluid for steam turbines, and there is also a demand for higher output from steam turbines, so it is also necessary to take into consideration the fact that such steam is introduced into the steam valve gear.

[0006] The main steam valve devices installed in thermal power generation equipment include main steam stop valves, steam control valves, reheat steam stop valves, and intercept valves, and among these, the steam valve devices that have the function of regulating steam flow rate are the steam control valves and intercept valves.

[0007] A steam turbine and a steam valve gear according to the related art will be described with reference to Fig. 5 to Fig. 8. Fig. 5 is a diagram showing an example of the structure of a steam turbine and a steam valve gear. The steam valve gear of the steam turbine shown in this figure is formed in a shell mount type structure, and includes a first valve casing 11, a first valve seat 12, a first valve body 13, a second valve casing 21, a second valve seat 22, and a second valve body 23.

[0008] The first valve casing 11 is attached directly to the upper part of a steam turbine casing 30 which forms the casing 1, and defines therein a first main flow passage 17 which communicates a steam outlet connected to the casing 1 with a steam inlet connected to a steam generating means (not shown) such as a boiler. The steam turbine casing 30 is divided into two in the axial direction of the steam turbine, and is made up of an upper casing 31 and a lower casing 32. The upper casing 31 and the lower casing 32 are fastened together via flanges 33 installed at both ends of each casing in the approximately horizontal direction.

[0009] The first valve seat 12 is formed in an annular shape, and is installed in the first main flow passage 17 in the first valve casing 11. The first valve body 13 adjusts the steam flow rate supplied to the casing 1 by moving vertically to seat on or separate from the first valve seat 12 (steam control valve). Two identical first valve bodies 13 are housed in the first valve casing 11 so as to be movable forward and backward relative to the first valve seat 12 in the vertical direction.

[0010] Fig. 6 is a diagram showing a structural example near the first valve casing 11 in Fig. 5. In Fig. 6, a sleeve 41 integrated with a stand 50 is a cylindrical member that surrounds the periphery of the first valve body 13, and the first valve body 13 slides inside the sleeve 41. A first valve rod 43 integrated with the child valve body 15 passes through the inside of the sleeve 41. The first valve rod 43 is appropriately driven in the vertical direction by a drive device (not shown).

[0011] A hole 44 through which the child valve 15 and the valve stem 43 pass is provided inside the first valve body 13, and the hole 44 is exposed to the outside through an opening 45 provided on the surface of the first valve body 13 facing the first valve seat 12 (the lower end surface in FIG. 2). The opening 45 communicates with the upstream side of the first valve body 13 in the first main flow path 17 (i.e., the outside of the sleeve 41) through the hole 44 and a gap (bypass flow path) between the first valve body 13 and the sleeve 41, thereby forming a chamber 46 that connects the first main flow path 17 to the casing 1.

[0012] The child valve element 15 opens and closes a chamber 46 by being seated on or separated from the inside of an opening 45 that serves as the valve seat, and is housed in the first valve body 13 so as to be movable forward and backward relative to the opening 45. Furthermore, protrusions 47, 48 are provided on the outer periphery of the first valve stem 43 and the inner periphery of the first valve body 13, respectively. For example, when the child valve element 15 is seated on the opening 45 and then pulled up by the first valve stem 43, first the chamber 46 opens and communicates with the casing 1. Thereafter, when the first valve stem 43 is further pulled up, the protrusion 47 of the first valve stem 43 engages with the protrusion 48 of the first valve body 13, so that the first valve body 13 is pulled up, and the first flow path 17 communicates with the casing 1.

[0013] By providing the child valve element 15 inside the first valve element 13 in this manner, the child valve element 15 opens before the first valve element 13 opens, reducing the internal pressure of the chamber 46. This allows a significant reduction in the driving force of a drive device (not shown) for opening the first valve element 13, making it easier to increase the valve diameter of the first valve element 13. This makes it easier to apply the present invention to, for example, a high-output turbine.

[0014] A drain pipe 18 is connected to the first valve casing 11. A drain valve 19 is attached to the drain pipe 18. When the turbine is started, the first valve casing 11 is warmed up in order to relieve thermal stress generated in the first valve casing 11. This warm-up operation is performed by opening the drain valve 19 with the first valve body 13 seated on the first valve seat 12 and discharging steam from within the first valve casing 11. As a result, drain generated within the first valve casing 11 is discharged to the outside of the steam turbine casing 30 via the drain pipe 18, thereby preventing drain from flowing into the casing 1 when the steam turbine is started.

[0015] Returning to FIG. 5, the second valve casing 21 is directly attached to the lower part of the steam turbine casing 30 which forms the casing 1, and forms therein a second main flow passage 27 which communicates between a steam outlet connected to the casing 1 and a steam inlet connected to steam generating means such as a boiler (not shown).

[0016] The second valve seat 22 is formed in an annular shape, and is installed in the second main flow passage 27 in the second valve casing 21. The second valve body 23 adjusts the steam flow rate supplied to the casing 1 by moving vertically to seat on or separate from the second valve seat 22 (steam control valve). Two identical sets are housed in the second valve casing 21 so as to be movable forward and backward relative to the second valve seat 22 in the vertical direction.

[0017] Fig. 7 is a diagram showing an example of the structure near the second valve casing 21 in Fig. 5. As shown in this figure, the second valve body 23 is a type of valve that does not have a sub-valve body therein, unlike the first valve body 13. A second valve rod 26 is attached to the lower end of the second valve body 23 so as to penetrate the stand 51. The valve rod 26 is appropriately driven in the vertical direction by a drive device (not shown), thereby moving the second valve body 23 in the vertical direction.

[0018] A drain pipe 28 is connected to the second valve casing 21. A drain valve 29 is attached to the drain pipe 28. As with the first valve casing 11, when the turbine is started up, the drain valve 29 is opened with the second valve body 23 seated on the second valve seat 22, thereby discharging steam from within the second valve casing 21 and warming up the second valve casing 21. Drain generated within the second valve casing 21 is discharged to the outside of the steam turbine casing 30 via the drain pipe 28, so that it is possible to prevent drain from flowing into the casing 1 when the steam turbine is started up.

[0019] Here, a case will be described in which, for example, a structure is adopted in which a child valve element 15 is built into the second valve element 23, similar to the first valve element 13, in order to reduce the driving force and increase the valve diameter of the second valve element 23. FIG. 8 is a diagram showing an example of the structure of the second valve element 13A when a child valve element 15A is built in. The second valve element 13A shown in this figure has a child valve element 15A. Each component of this second valve element 13A corresponds to each component of the first valve element 13 turned upside down, and is given the suffix A to distinguish it from each component of the first valve element 13.

[0020] Gravity acts on the second valve body 13A in the same direction as the valve opening direction (i.e., vertically downward). Therefore, if the pressure difference between the upstream side (pressure in the second valve casing 21) and the downstream side (pressure in the casing 1) of the second valve body 13A is smaller than the weight of the second valve body 13A, when the valve stem 43A is pulled down to separate the child valve body 15A from the opening 45A, the second valve body 13A may unintentionally fall downward following this.

[0021] In this case, the second valve body 13A may move regardless of the control of the valve rod 43A, and the control characteristics of the second valve body 13A may change depending on the pressure difference between the upstream and downstream sides of the second valve body 13A. In other words, it becomes impossible to freely control the opening degree of the second valve body 13A regardless of the pressure, so it is difficult to adopt such a structure from the viewpoint of control.

[0022] As described above, in the steam valve gear installed on the lower side of the steam turbine casing 30, the second valve body 23 does not have a sub-valve body built in, from the viewpoint of freely controlling the opening degree of the second valve body 23 regardless of pressure. Also, due to insufficient driving force of the drive device (also called insufficient valve opening force), it was necessary to select a small valve diameter that can be opened by the steam pressure acting at the start of the steam turbine, and therefore it was not possible to enlarge the valve diameter. Therefore, for example, the shell mount type structure in which the valve gear is directly mounted on the top and bottom of the steam turbine casing has been limited in its application to high-output steam turbines. [Prior art documents] [Patent documents]

[0023] [Patent Document 1] JP 2012-41823 A Summary of the Invention [Problem to be solved by the invention]

[0024] The problem to be solved by the present invention is to provide a steam valve device having a shell-mounted structure and a steam turbine equipped with the same, which is capable of utilizing a high-temperature, high-pressure working fluid while increasing the valve diameter. [Means for solving the problem]

[0025] In order to solve the above problems, the steam valve device of the embodiment having a shell-mounted structure has an upper side provided with a first hole connecting a first chamber consisting of a first valve body and a first sleeve surrounding it with the inside of the steam turbine, and a lower side provided with a second hole connecting a second chamber consisting of a second valve body and a second sleeve surrounding it with the inside of the steam turbine, as well as a drain hole for discharging drain from the second chamber. [Brief description of the drawings]

[0026] [Figure 1]FIG. 2 is a diagram showing a structural example of a steam turbine and a steam valve device in the first embodiment. [Diagram 2] FIG. 2 is a diagram showing a structural example of the vicinity of a first valve of the steam valve device in the first embodiment. [Diagram 3] FIG. 2 is a diagram showing a structural example of the vicinity of a second valve of the steam valve device in the first embodiment. [Figure 4] FIG. 11 is a diagram showing a structural example of the vicinity of a second valve of a steam valve device in a second embodiment. [Diagram 5] FIG. 1 is a diagram showing an example of the structure of a conventional steam turbine and a steam valve device. [Figure 6] FIG. 1 is a diagram showing an example of a structure in the vicinity of a first valve of a conventional steam valve device. [Figure 7] FIG. 1 is a diagram showing an example of a structure in the vicinity of a second valve of a conventional steam valve device. [Figure 8] FIG. 13 is a diagram showing an example of a structure near the second valve when a child valve body 15A is built in in the conventional art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, an embodiment for carrying out the invention will be described.

[0028] (First embodiment) The first embodiment will be described with reference to the drawings. Note that the same parts as those in the conventional embodiment are given the same reference numerals, and the description thereof will be omitted.

[0029] Fig. 1 is a diagram showing an example of the structure of a steam turbine and a steam valve gear in the first embodiment. The steam valve gear of the steam turbine shown in Fig. 1 is formed in a shell mount type structure, and includes a first valve casing 11, a first valve seat 12, a first valve body 113, a second valve casing 21, a second valve seat 22, and a second valve body 123.

[0030] The first valve body 113 moves vertically to seat on or separate from the first valve seat 12 to adjust the steam flow rate supplied to the casing 1, and is housed within the first valve casing 11 which is directly attached to the top of the steam turbine casing 30 so as to be movable vertically toward and away from the first valve seat 12.

[0031] The second valve body 123 moves vertically to seat on or separate from the second valve seat 22 to adjust the steam flow rate supplied to the casing 1, and is housed within the second valve casing 22 which is directly attached to the lower part of the steam turbine casing 30 so as to be movable upward and downward relative to the second valve seat 22.

[0032] Fig. 2 is a diagram showing an example of the structure near the first valve casing 11 in Fig. 1. In Fig. 2, a sleeve 141 integrated with the stand 60 is a cylindrical member that surrounds the periphery of the first valve body 113, and the first valve body 113 slides inside the sleeve 141.

[0033] A first valve body 113 integrated with a valve rod 143 is passed through the inside of the sleeve 141. The first valve rod 143 is appropriately driven in the vertical direction by a drive device (not shown). A hole 114 penetrates the inside of the first valve body 113 in the axial direction. The hole 114 communicates with the upstream side of the first valve body 113 in the first main flow path 17 (i.e., the outside of the sleeve 141) via a gap (bypass flow path) between the first valve body 113 and the sleeve 141, and these form a chamber 146 that connects the first main flow path 17 to the casing 1.

[0034] The internal pressure of the chamber 146 is determined by the balance between the amount of steam flowing into the chamber 146 through the gap (bypass flow path) between the first valve body 113 and the sleeve 141 and the amount of steam flowing out from the chamber 146 to the casing 1 through the hole 114. In other words, the internal pressure of the chamber 146 is affected by the diameter dimension (cross-sectional area) of the hole 114, and the larger the diameter dimension (cross-sectional area) of the hole 114, the more the internal pressure of the chamber 146 can be reduced.

[0035] By providing hole 114 penetrating first valve body 113 in the axial direction in this manner, the internal pressure of chamber 146 is continuously reduced even before first valve body 113 opens. Therefore, the driving force of a drive device (not shown) for opening first valve body 113 can be significantly reduced, making it easy to increase the valve diameter of first valve body 113. In addition, the number of components is significantly reduced compared to a conventional steam valve device having a child valve, simplifying the structure, which leads to easier parts management and improved durability against wear.

[0036] In addition, in order to integrate the first valve rod 143 and the first valve body 113, other methods such as screwing the valve rod 143 into the first valve body 113 may be used. The hole 114 does not have to penetrate the first valve body 113 in the axial direction, and may be provided, for example, in a direction not parallel to the axial direction but obliquely. Also, a structure with multiple holes, for example, with another hole on the opposite side of the center of the valve body, may be used.

[0037] Fig. 3 is a diagram showing an example of the structure near the second valve casing 21 in Fig. 1. In Fig. 3, a sleeve 142 integrated with the stand 61 is a cylindrical member that surrounds the periphery of the second valve body 123, and the second valve body 123 slides inside the sleeve 142. The second valve body 123 integrated with the second valve rod 126 is passed through the inside of the sleeve 142.

[0038] The second valve rod 126 is appropriately driven in the vertical direction by a drive device (not shown). A hole 124 penetrates the inside of the second valve body 123 in the axial direction. The hole 124 communicates with the upstream side of the second valve body 123 in the second main flow path 27 (i.e., the outside of the sleeve 142) through a gap (bypass flow path) between the second valve body 123 and the sleeve 142, and thereby a chamber 147 that connects the second main flow path 27 to the casing 1 is formed.

[0039] The internal pressure of the chamber 147 is determined by the balance between the amount of steam flowing into the chamber 147 through the gap (bypass flow path) between the second valve body 123 and the sleeve 142, and the amount of steam flowing out from the chamber 147 to the casing 1 through the hole 124. In other words, the internal pressure of the chamber 147 is affected by the diameter dimension (cross-sectional area) of the hole 124, and the larger the diameter dimension (cross-sectional area) of the hole 124, the more the internal pressure of the chamber 147 can be reduced.

[0040] By providing the hole 124 penetrating the second valve body 123 in the axial direction in this manner, the internal pressure of the chamber 147 is continuously reduced even before the second valve body 123 opens. Therefore, the driving force of the drive device (not shown) for opening the second valve body 123 can be significantly reduced, making it easier to make the valve diameter of the second valve body 123 significantly larger than that of the conventional second valve body 23.

[0041] In addition, in order to integrate the second valve rod 126 and the second valve body 123, other methods such as screwing the second valve rod 126 into the second valve body 123 may be used. The hole 124 does not have to penetrate the first valve body 123 in the axial direction, and may be provided, for example, in a direction not parallel to the axial direction but obliquely. Also, a structure with multiple holes, for example, with another hole on the opposite side of the center of the valve body, may be used.

[0042] The structure of FIG. 3 described so far is the same as the first valve body 113 attached directly to the upper part of the steam turbine casing 30 shown in FIG.

[0043] Here, since the second valve body 123 slides inside the sleeve 142 toward the casing 1, the opening of the sleeve 142 faces upward, and the residual steam remaining in the chamber 147 during a long-term shutdown becomes drain, and drain from the second main passage 27 and the casing 1 also flows into the chamber 147 and accumulates therein. If drain accumulates in the chamber 147, when the second valve body 123 is opened after warm-up operation at turbine startup, the drain overflows from the chamber 147 and is scattered toward the casing 1 at once. Furthermore, during a long-term shutdown or long-term storage, there is a risk that the accumulated drain will cause rust or corrosion in the second valve body 123 and the sleeve 142 located in the chamber 147.

[0044] In order to prevent accumulation of drainage in this chamber 147, a drain hole 125 that communicates the upstream side of the second valve body 123, i.e., the second main flow path 27, with the chamber 147 is provided in the wall surface of the sleeve 142 corresponding to the lowest part of the chamber 147. This drain hole 125 has a diameter dimension (cross-sectional area) that does not affect the internal pressure of the chamber 147 with respect to the characteristics of the hole 124 of the second valve body 123, and the number of drain holes 125 may be one or more.

[0045] By providing the drain hole 125, before the turbine starts, the drain accumulated in the chamber 147 passes through the drain hole 125 due to the difference in height and flows out to the second main flow path 27 side, and is eventually discharged to the outside of the steam turbine casing 30 via the drain pipe 28 of the second valve casing 21. In this way, the drain in the chamber 147 can be continuously and sufficiently discharged in advance with a simple configuration, so that the second valve body 123 and the sleeve 142 located in the chamber 147 do not rust or corrode. As a result, there is no risk of the second valve body 123 malfunctioning when the second valve body 123 slides inside the sleeve 142.

[0046] According to the first embodiment, cylindrical sleeves 141 and 142 are provided so as to surround the first valve body 113 and the second valve body 123, respectively, and holes are provided inside the first valve body 113 and the second valve body 123, thereby reducing the internal pressure of the chambers 146 and 147 and reducing the driving force for opening the valves, and thus the valve diameter can be increased to increase the output of the steam turbine. In addition, by simplifying the structure and reducing the number of parts, it is possible to simplify parts management and improve durability against wear. Furthermore, drainage is discharged by providing a drain hole 125 on the wall surface of the sleeve 142, and rust and corrosion of the second valve body 123 and the sleeve 142 located in the chamber 147 can be prevented, so there is no risk of the second valve body 123 malfunctioning when the second valve body 123 slides inside the sleeve 142.

[0047] Second Embodiment The second embodiment will be described with reference to Fig. 4. The same components as those in the first embodiment are denoted by the same reference numerals, and the description thereof will be omitted here. The difference between the second embodiment and the first embodiment is the configuration of the drain hole 225.

[0048] Fig. 4 is a diagram showing a structural example near the second valve casing 21 in Fig. 1. In Fig. 3, the drain hole 125 is provided on the outer surface of the sleeve 142, but since steam flows in a complex manner around the sleeve 142 located inside the second main flow passage 27 during operation of the steam turbine, whistling noise such as a beep may be generated from the drain hole 125.

[0049] 4, the second valve body 123 slides inside the sleeve 142 toward the casing 1, so that the opening of the sleeve 142 faces upward, and therefore the residual steam that remains in the chamber 147 during long-term shutdown or long-term storage becomes drain, and drain from the second main flow path 27 and the casing 1 also flows into the chamber 147 and accumulates therein. In order to discharge the drain that has accumulated in this chamber 147, a drain hole 225 that penetrates the inside of the stand 61 is provided so as not to open toward the inside of the second main flow path 27, where the steam flows in a complex manner, and the direction is changed inside the stand 61 so that the drain is discharged toward the outside (outer surface) of the stand.

[0050] The drain hole 225 has a diameter (cross-sectional area) that does not affect the internal pressure of the chamber 147 relative to the characteristics of the hole 124 of the second valve body 123, and the number of the drain holes 225 may be one or more.

[0051] By providing the drain hole 225, before the turbine starts, the drain accumulated in the chamber 147 falls through the drain hole 225 and is discharged to the outside of the stand 61 via the flange 230. Meanwhile, the drain in the second main flow path 27 passes through the drain pipe 28 of the second valve casing 21, joins with the drain from the flange 230 at the elbow 231, and is discharged. Depending on the arrangement of the stand 61, the drain hole 225 and the drain pipe 28 may be independent of each other without joining, and the installation location and number of the drain valve 29 are not limited to the form shown in Figure 4. The drain is eventually discharged to the outside of the steam turbine casing 30.

[0052] In this way, not only is the accumulated drain in the chamber 147 discharged, but the drain hole 225 does not open into the inside of the second main flow passage 27, where steam flows in a complex manner, so that noise such as a whistling sound is not generated.

[0053] According to the second embodiment, a cylindrical sleeve 142 is provided so as to surround the second valve body 123, and a hole is provided in the second valve body 123, thereby reducing the internal pressure of the chamber 147 and reducing the driving force for opening the valve, and therefore the valve diameter can be increased to increase the output of the steam turbine. Furthermore, by providing a drain hole 225 inside the stand 61, drain can be discharged without generating a whistling noise, and rust and corrosion of the second valve body 123 and the sleeve 142 located in the chamber 142 can be prevented, so that there is no risk of the second valve body 123 malfunctioning when it slides inside the sleeve 142.

[0054] According to the two embodiments described above, in a steam valve device that is directly attached to the top of a steam turbine casing of a conventional structure, by providing a sub-valve body, the steam pressure applied to the valve body can be reduced, thereby reducing the driving force. However, in a steam valve device that is directly attached to the bottom of a steam turbine casing, the control of the valve body becomes inaccurate due to the influence of the valve body's own weight, so a structure provided with a sub-valve body is unsuitable for a steam valve device that is directly attached to the bottom of a steam turbine casing.

[0055] In the present embodiment, instead of providing a sub-valve, a cylindrical sleeve is provided surrounding the valve body, and a hole is provided in the valve body, thereby reducing the driving force for opening the valves of both the upper and lower steam valve devices on the steam turbine casing. Since there is no sub-valve, even in the steam valve device directly attached to the lower part of the steam turbine casing, the problem of the valve body's own weight is eliminated, and the valve diameter can be increased in both the upper and lower steam valve devices on the steam turbine casing, enabling the steam turbine to have a higher output.

[0056] In addition, since neither the upper nor lower steam valve devices on the steam turbine casing have a structure having a child valve body, the structure is simplified and the number of parts is reduced, which makes it possible to simplify parts management and improve durability against wear. Furthermore, in the steam valve device directly attached to the lower part of the steam turbine casing, a drain hole communicating with the chamber is provided to discharge drainage from the chamber, thereby preventing rust and corrosion of the valve body and sleeve located in the chamber.

[0057] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0058] 1... casing, 11... first valve casing, 12... first valve seat, 17... first main flow passage, 21: second valve casing; 22: second valve seat; 27: second main flow passage; 30... Steam turbine casing, 60… Stand, 61… Stand, 113: first valve body; 114: hole; 123... second valve body, 124... hole, 125... drain hole, 126... second valve stem 141 ... sleeve, 142 ... sleeve, 143 ... first valve stem, 146 ... chamber, 147 ... chamber, 225 ... drain hole,

Claims

1. A steam turbine comprising: a steam turbine casing; and a shell-mounted steam valve device directly provided on the steam turbine casing, The steam valve device includes: a first valve casing that is directly attached to an upper portion of the steam turbine casing and that forms a first main flow passage that guides steam into an interior of the steam turbine casing; a first valve seat disposed in the first main flow passage; a first valve body accommodated in the first valve casing so as to be movable up and down relative to the first valve seat; a first stand including a first sleeve attached to the first valve casing and surrounding the first valve body; a first chamber defined by the first sleeve and the first valve body; a first bypass flow passage that communicates an upstream side of the first valve body in the first main flow passage with the first chamber; a first hole provided in the first valve body for communicating the first chamber with a downstream side of the first valve body in the first main flow path; a second valve casing that is directly attached to a lower portion of the steam turbine casing and that forms a second main flow passage that guides the steam into an interior of the steam turbine casing; a second valve seat disposed in the second main flow passage; a second valve body accommodated in the second valve casing so as to be movable up and down relative to the second valve seat; a second stand including a second sleeve attached to the second valve casing and surrounding the second valve body; a second chamber defined by the second sleeve and the second valve body; a second bypass flow passage that communicates the second chamber with an upstream side of the second valve body in the second main flow passage; a second hole provided in the second valve body for communicating the second chamber with a downstream side of the second valve body in the second main flow path; a drain hole provided in a wall surface of the second sleeve for discharging drainage accumulated in the second chamber; A steam turbine having a

2. The steam turbine according to claim 1 , wherein the drain hole connects the second chamber and the second main flow passage.

3. 2. The steam turbine according to claim 1, wherein the drain hole is provided penetrating the inside of the second stand and directly connects the second chamber with the outside of the steam turbine casing.

4. A steam turbine comprising: a steam turbine casing; and a shell-mounted steam valve device directly provided on the steam turbine casing, The steam valve device includes: a valve casing that is directly attached to a lower portion of the steam turbine casing and that forms a main flow passage that guides the steam into the inside of the steam turbine casing; A valve seat disposed in the main flow path; a valve body accommodated in the valve casing so as to be movable up and down relative to the valve seat; a stand having a sleeve attached to the valve casing and surrounding the valve body; a chamber defined by the sleeve and the valve body; a bypass flow passage that communicates the upstream side of the valve body in the main flow passage with the chamber; a hole provided in the valve body for communicating the chamber with a downstream side of the valve body in the main flow path; a drain hole provided in a wall surface of the sleeve for discharging drainage accumulated in the chamber; A steam turbine having a

5. The steam turbine according to claim 4 , wherein the drain hole connects the chamber and the main flow passage.

6. 5. The steam turbine according to claim 4, wherein the drain hole is provided penetrating the inside of the stand and directly connects the chamber to the outside of the steam turbine casing.

7. A shell-mounted steam valve device that is directly mounted on a steam turbine casing, comprising: The steam valve device includes: a valve casing that is directly attached to a lower portion of the steam turbine casing and that forms a main flow passage that guides the steam into the inside of the steam turbine casing; A valve seat disposed in the main flow path; a valve body accommodated in the valve casing so as to be movable up and down relative to the valve seat; a stand having a sleeve attached to the valve casing and surrounding the valve body; a chamber defined by a sleeve surrounding the valve body and the valve body; a bypass flow passage that communicates the upstream side of the valve body in the main flow passage with the chamber; a hole provided in the valve body for communicating the chamber with a downstream side of the valve body in the main flow path; a drain hole provided in a wall surface of the sleeve for discharging drainage accumulated in the chamber; A steam valve device having a

8. The steam valve device according to claim 7 , wherein the drain hole connects the chamber and the main flow path.

9. The steam valve device according to claim 9 , wherein the drain hole is provided penetrating the inside of the stand and directly connects the chamber with the outside of the steam turbine casing.

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