Strainer and steam valve including the same

Abstract

To facilitate removal work of a temporary strainer from a strainer body.SOLUTION: A steam strainer includes a strainer body having a plurality of steam passage holes, a temporary strainer having a plurality of temporary steam passage holes, and a plurality of screws for attaching the temporary strainer along a body outer peripheral surface of the strainer body. The temporary strainer further includes a screw portion insertion hole which penetrates the temporary strainer around a temporary hole formation region where the plurality of temporary steam passage holes are formed and through which a male screw portion of each of the plurality of screws can pass and a screw head portion of each of the plurality of screws cannot pass. The strainer main body further includes a screw hole recessed from the main body outer circumferential surface toward the main body inner circumferential surface of the strainer main body around a hole formation region in which the plurality of steam passage holes are formed. The screw hole includes a female screw hole into which the male screw portion passing through the screw portion insertion hole is screwed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a strainer disposed within a valve casing in which a steam flow passage is formed, a steam valve including the strainer, and a method for manufacturing the strainer. [Background technology]

[0002] A steam valve that can adjust the flow rate of steam flowing into a steam turbine is provided with a strainer to remove foreign matter contained in the steam.

[0003] The strainer of Patent Document 1 below includes a strainer body and a temporary strainer. The strainer body is cylindrical so that it can be housed in a valve casing of a steam valve. This strainer body is formed with a plurality of steam inlet holes that penetrate from the outer peripheral surface to the inner peripheral surface of the strainer body. The temporary strainer is a temporary perforated plate screen. When attaching the temporary strainer to the main strainer, first, the temporary strainer is brought into contact with the outer peripheral surface of the strainer body, and the entire peripheral edge of the temporary strainer is welded to the strainer body. Furthermore, the temporary strainer is connected to the strainer body with a plurality of rivets that penetrate the temporary strainer and the strainer body.

[0004] After installation or repair work on a boiler that generates steam to be supplied to a steam turbine or on a main steam line connecting the boiler and the steam turbine, there is a possibility that foreign matter resulting from the work may be mixed into the steam when steam flows from the boiler to the main steam line. For this reason, the strainer described in Patent Document 1 includes a strainer body and a temporary strainer. After steam flows through the main steam line for a predetermined time and the amount of foreign matter in the steam decreases, the temporary strainer is removed from the strainer body, leaving the strainer body inside the valve casing. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Utility Model Application Publication No. 62-074102 Summary of the Invention [Problem to be solved by the invention]

[0006] With the technology described in Patent Document 1, when removing the temporary strainer from the strainer body, it is necessary to remove the welded portion between the strainer body and the temporary strainer and also to cut off multiple rivets. Therefore, with the technology described in Patent Document 1, the work of removing the temporary strainer from the strainer body is cumbersome.

[0007] Therefore, an object of the present disclosure is to provide a strainer that allows the temporary strainer to be easily removed from the strainer body, a steam valve including the strainer, and a method for manufacturing the strainer. [Means for solving the problem]

[0008] In one aspect of the disclosure to achieve the above object, the strainer comprises: A strainer is disposed in a valve casing having a steam flow path. The strainer comprises: a cylindrical strainer body having a main body outer peripheral surface, a main body inner peripheral surface back-to-back with the main body outer peripheral surface, and a plurality of steam passage holes extending from the main body outer peripheral surface to the main body inner peripheral surface; a temporary strainer disposed along the main body outer peripheral surface of the strainer body and having a temporary inner peripheral surface facing the main body outer peripheral surface, a temporary outer peripheral surface back-to-back with the temporary inner peripheral surface, and a plurality of temporary steam passage holes extending from the temporary outer peripheral surface to the temporary inner peripheral surface and having inner diameters smaller than the inner diameters of each of the plurality of steam passage holes; and a plurality of screws for attaching the temporary strainer along the main body outer peripheral surface of the strainer body. A temporary hole formation region in which the plurality of temporary steam passage holes are formed in the temporary strainer overlaps with a hole formation region in which the plurality of steam passage holes are formed in the strainer body. Each of the plurality of screws has a cylindrical male threaded portion having a male thread formed therein, and a screw head provided at the end of the male threaded portion that is closer to the base end than the tip end and the base end in the extending direction of the male threaded portion. The temporary strainer further has a screw portion insertion hole that penetrates from the temporary outer peripheral surface to the temporary inner peripheral surface of the temporary strainer around the temporary hole formation area, and through which the male threaded portion of each of the plurality of screws can pass but the screw head cannot pass. The strainer body further has a screw hole that is recessed from the outer peripheral surface of the strainer body toward the inner peripheral surface of the strainer body around the hole formation area, and that communicates with the screw portion insertion hole of the temporary strainer. The screw hole of the strainer body has a female screw hole into which the male threaded portion that has passed through the screw portion insertion hole is screwed.

[0009] In this embodiment, the temporary strainer can be easily removed from the strainer body by removing multiple screws from the strainer using a screwdriver or other screwdriver tool.

[0010] In one aspect of the disclosure to achieve the above object, a steam valve is provided, The strainer according to the above aspect includes the valve casing, a valve disc reciprocating in the axial direction of an axis within the valve casing to open and close the flow path, and a valve rod extending on the axis in the axial direction and connected to the valve disc. The flow path includes an axial flow path portion extending in the axial direction about the axis, an annular flow path portion formed in an annular shape around an axial inlet-side flow path portion that is a portion of the axial flow path portion in the axial direction and is connected to the axial inlet-side flow path portion, an inlet flow path portion extending from the annular flow path portion in a first radial direction relative to the axis and opening at an outer surface of the valve casing, and an outlet flow path portion extending in either direction from an axial outlet-side flow path portion that is another portion of the axial flow path portion in the axial direction and opening at the outer surface of the valve casing. The valve disc is arranged to be reciprocally movable within the axial inlet-side flow path portion. The strainer is disposed at the boundary between the axial inlet side flow path portion and the annular flow path portion so that the strainer body is cylindrical around the axis.

[0011] In this embodiment, foreign matter contained in the steam that has flowed into the valve casing can be captured by the strainer.

[0012] In one aspect of the disclosure to achieve the above object, a method for manufacturing a strainer includes: A method for manufacturing a strainer to be disposed in a valve casing having a steam flow path includes the following steps: a preparation step for preparing a cylindrical main body material having an outer circumferential surface and an inner circumferential surface and capable of being disposed in the flow path; a temporary material attachable along the outer circumferential surface of the main body material and having a temporary inner circumferential surface facing the outer circumferential surface and a temporary outer circumferential surface back-to-back with the temporary inner circumferential surface; a main body material processing step for processing the main body material to form a strainer body; a temporary material processing step for processing the temporary material to form a temporary strainer; and an assembly step for attaching the temporary strainer to the strainer body using the multiple screws. Each of the multiple screws has a cylindrical male thread portion having a male thread and a screw head provided at the proximal end of the male thread portion, out of a distal end and a proximal end in the extension direction of the male thread portion. The main body material processing process includes a steam passage hole forming process of forming a plurality of steam passage holes that penetrate from the main body outer peripheral surface to the main body inner peripheral surface within a predetermined hole formation region of the main body material, and a screw hole forming process of forming screw holes that are recessed from the main body outer peripheral surface toward the main body inner peripheral surface around the hole formation region of the main body material and into which the male thread portions of each of the plurality of screws can be screwed.The temporary material processing process includes a temporary steam passage hole forming process of forming a plurality of temporary steam passage holes that penetrate from the temporary outer peripheral surface to the temporary inner peripheral surface within a predetermined temporary hole formation region of the temporary material and have inner diameters smaller than the inner diameters of each of the plurality of steam passage holes, and a screw portion insertion hole forming process of forming a screw portion insertion hole that penetrates from the temporary outer peripheral surface to the temporary inner peripheral surface around the temporary hole formation region of the temporary material and through which the male thread portions of each of the plurality of screws can pass but the screw heads cannot pass. In the screw portion insertion hole forming process, the temporary inner surface of the temporary material is brought into contact with the outer main surface of the main material, and when the temporary hole formation area of ​​the temporary material is overlapped with the hole formation area of ​​the main material, the screw portion insertion hole is formed in the temporary material at a position that can communicate with the screw hole of the main material.In the assembly process, the temporary inner peripheral surface is brought into contact with the outer peripheral surface of the main body, the temporary hole formation area is overlapped with the hole formation area, and then the male threaded portion of the screw is inserted into the threaded portion insertion hole of the temporary strainer and then screwed into the screw hole of the strainer main body.

[0013] In the strainer manufactured in this manner, as with the strainer in the first manner described above, the temporary strainer can be easily removed from the strainer body by using a screwdriver or other screwdriver tool to remove multiple screws from the strainer. [Effects of the Invention]

[0014] According to one aspect of the present disclosure, the temporary strainer can be easily removed from the strainer body. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a cross-sectional view of a steam valve in one embodiment according to the present disclosure. [Figure 2] 1 is a cross-sectional view of a strainer taken along an imaginary plane perpendicular to an axis in one embodiment according to the present disclosure. FIG. [Figure 3] FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2. [Figure 4] FIG. 2 is a development view of a strainer body and a temporary strainer developed in a circumferential direction relative to an axis in one embodiment according to the present disclosure. [Figure 5] FIG. 2 is a cross-sectional view of a main portion of a strainer body and a temporary strainer around a screw in one embodiment according to the present disclosure. [Figure 6] 1 is a flowchart illustrating a manufacturing procedure for a strainer in one embodiment according to the present disclosure. [Figure 7] 1 is a cross-sectional view of a main portion of a strainer and a temporary strainer during a countersinking process according to an embodiment of the present disclosure. FIG. [Figure 8] 1 is a cross-sectional view of a main portion of a strainer and a temporary strainer after a countersink machining process according to an embodiment of the present disclosure. FIG. [Figure 9]1 is a cross-sectional view of a main portion of a strainer after a screw hole forming step and a temporary strainer after a threaded portion insertion hole forming step according to an embodiment of the present disclosure. FIG. [Figure 10] FIG. 10 is a cross-sectional view of the main parts of the strainer body and temporary strainer around the screw in the comparative example. [Figure 11] 10 is a development view of a strainer body and a temporary strainer developed in a circumferential direction Dc relative to an axis in a first modified example of an embodiment according to the present disclosure. FIG. [Figure 12] FIG. 10 is a cross-sectional view of a strainer taken along a virtual plane perpendicular to an axis in a second modified example of an embodiment according to the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments and various modifications of a strainer and a steam valve including the strainer according to the present disclosure will be described with reference to the drawings.

[0017] "Embodiment of Steam Valve" An embodiment of a steam valve according to the present disclosure will be described in detail with reference to Figure 1. This steam valve is a valve that can adjust the flow rate of steam flowing into a steam turbine.

[0018] The steam valve comprises a valve casing 10, a valve seat 11, a valve body 12 that can move back and forth within the valve casing 10 in an axial direction Da in which the axis A of the valve casing 10 extends, a valve rod 13 to which the valve body 12 is connected, and a strainer 20.

[0019] The valve casing 10 is formed with a flow path 15 through which steam can flow. This flow path 15 has an axial flow path portion 16, an annular flow path portion 17, an inlet flow path portion 18i, and an outlet flow path portion 18o. The axial flow path portion 16 is a cylindrical flow path portion extending in the axial direction Da with the axis A as its center. The inlet flow path portion 18i is a flow path portion formed in an annular shape with the axis A as its center around the axial inlet-side flow path portion 16i, which is a part of the axial flow path portion 16 in the axial direction Da, and is in communication with the axial inlet-side flow path portion 16i. The inlet flow path portion 18i is a flow path portion extending from the annular flow path portion 17 in a first radial direction Dr1 of the radial directions Dr relative to the axis A and opening at the outer surface of the valve casing 10. The outlet flow path section 18o is a flow path section that extends from the axial outlet side flow path section 16o, which is another part of the axial direction Da in the axial flow path section 16, in a second radial direction Dr2 of the radial direction Dr and opens at the outer surface of the valve casing 10.

[0020] The valve seat 11 is annular and centered on the axis A. The valve seat 11 is disposed at the boundary between the axial inlet-side flow passage portion 16i and the axial outlet-side flow passage portion 16o.

[0021] The valve element 12 is disposed in the axial inlet-side flow passage 16i and is reciprocable in the axial direction Da between a closed state in which the valve element 12 is in contact with the valve seat 11 and an open state in which the valve element 12 is separated from the valve seat 11.

[0022] The valve stem 13 extends in the axial direction Da and is disposed on the axis A. The valve disc 12 is connected to a first end of the valve stem 13. A drive mechanism (not shown) is provided to a second end of the valve stem 13. The valve stem 13 and the valve disc 12 connected to the valve stem 13 reciprocate in the axial direction Da due to the operation of the drive mechanism.

[0023] The strainer 20 is a device for capturing most of the foreign matter contained in the steam that flows into the valve casing 10 from the inlet flow path portion 18i. The strainer 20 is arranged at the boundary between the axial inlet flow path portion 16i and the annular flow path portion 17 so as to be cylindrical around the axis A, with the axis A as its center.

[0024] "Embodiment of strainer" An embodiment of a strainer according to the present disclosure will be described in detail with reference to Figures 2 to 10. This strainer is the strainer 20 disposed within the valve casing 10 described above.

[0025] 2 and 3, the strainer 20 in this embodiment includes a strainer body 21, two temporary strainers 31, and a plurality of screws 41. Note that Fig. 2 is a cross-sectional view of the strainer 20 taken along an imaginary plane perpendicular to the axial direction Da. Also, Fig. 3 is a cross-sectional view taken along line III-III in Fig. 2.

[0026] The strainer body 21 has a cylindrical shape centered on an axis A. This axis A is the axis A of the valve casing 10, but is also the axis A of the strainer 20 in this embodiment. The strainer body 21 has a body outer peripheral surface 24o, a body inner peripheral surface 24i that is back-to-back with the body outer peripheral surface 24o, and a plurality of steam passage holes 25 that penetrate from the body outer peripheral surface 24o to the body inner peripheral surface 24i.

[0027] The two temporary strainers 31 are arranged along the main body outer peripheral surface 24o of the strainer main body 21. Specifically, the first temporary strainer 31a of the two temporary strainers 31 is arranged on the main body outer peripheral surface 24o along a portion on the inlet flow path 18i side of the axis A. That is, the first temporary strainer 31a is arranged over approximately half the circumference of the portion of the strainer main body 21 on the inlet flow path 18i side. Furthermore, the second temporary strainer 31b of the two temporary strainers 31 is arranged on the main body outer peripheral surface 24o along a portion on the opposite side of the axis A from the inlet flow path 18i. That is, the second temporary strainer 31b is arranged over approximately half the circumference of the portion of the strainer main body 21 on the opposite side from the inlet flow path 18i. Each of the two temporary strainers 31 has a temporary inner peripheral surface 34i facing the main body outer peripheral surface 24o, a temporary outer peripheral surface 34o that is back-to-back with the temporary inner peripheral surface 34i, and a plurality of temporary steam passage holes 35 that penetrate from the temporary outer peripheral surface 34o to the temporary inner peripheral surface 34i. The inner diameter of each steam passage hole 25 is, for example, 3.0 to 5.0 mm. The inner diameter of each temporary steam passage hole 35 is, for example, 1.0 to 2.5 mm. Therefore, in this embodiment, the inner diameter of each steam passage hole 25 is smaller than the inner diameter of each of the plurality of steam passage holes 25. The spacing between the plurality of temporary steam passage holes 35 is narrower than the spacing between the plurality of steam passage holes 25.

[0028] As shown in Fig. 4, the plurality of steam passing holes 25 are formed in the two hole formation regions 22 of the strainer body 21. Furthermore, the plurality of temporary steam passing holes 35 are formed in the temporary hole formation regions 32 of each temporary strainer 31. Note that Fig. 4 is a development view of the strainer body 21 and the temporary strainer 31 developed in the circumferential direction Dc with respect to the axis A.

[0029] The first hole formation region 22a, which is one of the two hole formation regions 22 of the strainer body 21, is defined within the region of the strainer body 21 in which the first temporary strainer 31a is disposed. The second hole formation region 22b, which is the other of the two hole formation regions 22, is defined within the region of the strainer body 21 in which the second temporary strainer 31b is disposed. The first hole formation region 22a and the second hole formation region 22b are the same size. The dimension of each hole formation region 22 in the axial direction Da is, for example, approximately 80% of the dimension of the strainer body 21 in the axial direction Da. The dimension of each hole formation region 22 in the circumferential direction Dc is approximately 40% of the outer circumferential dimension of the strainer body 21.

[0030] The dimension in the axial direction Da of the temporary hole formation region 32 of each temporary strainer 31 is, for example, about 85% of the dimension in the axial direction Da of the strainer body 21. Furthermore, the dimension in the circumferential direction Dc of the temporary hole formation region 32 of each temporary strainer 31 is, for example, about 45% of the outer circumferential dimension of the strainer body 21. In other words, the size of the temporary hole formation region 32 of each temporary strainer 31 is slightly larger than the size of each hole formation region 22 of the strainer body 21.

[0031] As shown in FIG. 9 , the screw 41 has a male thread portion 42 and a screw head 43. The male thread portion 42 is cylindrical, centered on the screw axis Ag, and has a male thread formed on its outer periphery. The screw head 43 is provided at the end of the proximal end Dgb of the distal end Dgt and proximal end Dgb in the extension direction Dg of the male thread portion 42. Note that this extension direction Dg is the direction in which the screw axis Ag extends. The screw head 43 has a conical portion 44 whose outer diameter gradually decreases toward the distal end Dgt. In other words, the screw 41 is a flat head screw. If a pan head screw is used as the screw 41, for example, the force F that presses the screw head against the temporary strainer 31 will be uneven due to the cylindrical shape of the temporary strainer 31. That is, the pressing force F in the circumferential direction Dc of the temporary strainer 31 is lower than the pressing force F in the axial direction Da of the temporary strainer 31. On the other hand, it was confirmed by calculation that if a flat head screw is used and a countersunk hole is provided to match the shape of the flat head screw, a nearly uniform force F is generated. Therefore, in this embodiment, flat head screws are used as the screws 41.

[0032] The thickness of each temporary strainer 31, in other words, the distance (thickness) t2 between the temporary outer peripheral surface 34o and the temporary inner peripheral surface 34i of each temporary strainer 31, is shorter than the dimension of the conical portion 44 of the screw 41 in the extension direction Dg, in other words, the distance t3 between the end of the base end side Dgb and the end of the tip end side Dgt of the conical portion 44 of the screw 41. In addition, the thickness of the strainer body 21, in other words, the distance (thickness) t1 between the temporary outer peripheral surface 34o and the temporary inner peripheral surface 34i of the strainer body 21, is longer than the distance t3 between the end of the base end side Dgb and the end of the tip end side Dgt of the conical portion 44 of the screw 41.

[0033] 4, the temporary strainer 31 further has a plurality of screw portion insertion holes 36 that penetrate from the temporary outer peripheral surface 34o to the temporary inner peripheral surface 34i of the temporary strainer 31 around the temporary hole formation region 32, and through which the male screw portions 42 of the screws 41 can pass but the screw heads 43 cannot. The strainer body 21 further has a plurality of screw holes 26 that are recessed from the body outer peripheral surface 24o of the strainer body 21 towards the body inner peripheral surface 24i around the hole formation region 22 and communicate with the screw portion insertion holes 36 of the temporary strainer 31.

[0034] 9, the threaded portion insertion hole 36 of the temporary strainer 31 is a countersunk hole. For this reason, hereinafter, the threaded portion insertion hole 36 may be referred to as a countersunk hole 36. This countersunk hole 36 corresponds to the shape of at least a part of the base end side Dgb of the conical portion 44 of the screw 41, and is a conical hole whose inner diameter gradually decreases from the temporary outer peripheral surface 34o to the temporary inner peripheral surface 34i of the temporary strainer 31 so that at least a part of the base end side Dgb of the conical portion 44 can be accommodated.

[0035] The threaded hole 26 of the strainer body 21 does not penetrate from the outer peripheral surface 24o to the inner peripheral surface 24i of the strainer body 21, but has a hole bottom 26b. This threaded hole 26 has a counterbore hole 26c and a female threaded hole 26f. The counterbore hole 26c corresponds to the shape of the tip side Dgt portion of the conical portion 44 of the screw 41, excluding at least a portion of the base end Dgb, and is a hole whose inner diameter gradually decreases from the outer peripheral surface 24o of the strainer body 21 toward the inner peripheral surface 24i of the strainer body 21 so as to accommodate the tip side Dgt portion of the conical portion 44 of the screw 41, excluding at least a portion of the base end Dgb. The female threaded hole 26f is a hole into which the male threaded portion 42 of the screw 41 can be screwed. This female threaded hole 26f is formed on the tip side Dgt of the counterbore hole 26c.

[0036] Next, a method for manufacturing the strainer 20 described above will be described with reference to the flowchart shown in FIG.

[0037] First, the main body material 23, two temporary materials 33, and a plurality of screws 41 are prepared (preparation step S1). The main body material 23 is the material for the strainer main body 21. Therefore, the main body material 23 has a size that allows it to be placed in the axial inlet-side flow path portion 16i of the valve casing 10 described with reference to FIG. 1. This main body material 23 is cylindrical and has a main body outer peripheral surface 24o and a main body inner peripheral surface 24i. The distance (thickness) between the temporary outer peripheral surface 34o and the main body inner peripheral surface 24i of this main body material 23 is the same as the thickness t1 of the strainer main body 21 described above. The two temporary materials 33 are each the material for the temporary strainer 31. The temporary material 33 is a plate having a temporary outer peripheral surface 34o and a temporary inner peripheral surface 34i. The distance (thickness) between the provisional outer peripheral surface 34o and the provisional inner peripheral surface 34i of this provisional material 33 is the same as the distance (thickness) t2 between the provisional outer peripheral surface 34o and the provisional inner peripheral surface 34i of the provisional strainer 31.

[0038] Next, the temporary material 33 is processed to form the temporary strainer 31 (temporary material processing step S2), and the main body material 23 is processed to form the strainer main body 21 (main body material processing step S5).

[0039] The temporary material processing step S2 includes a temporary steam passage hole forming step S3 and a threaded portion insertion hole forming step S4. In the temporary steam passage hole forming step S3, a plurality of temporary steam passage holes 35 are formed in the temporary hole formation region 32 of each of the two temporary materials 33. In the threaded portion insertion hole forming step S4, a plurality of threaded portion insertion holes 36 are formed around the temporary hole formation region 32. This threaded portion insertion hole forming step S4 includes a counterbore co-machining step S8, which will be described later.

[0040] The main body material processing step S5 includes a steam passage hole forming step S6 and a screw hole forming step S7. In the steam passage hole forming step S6, a plurality of steam passage holes 25 are formed in the two hole formation regions 22 of the main body material 23. In the screw hole forming step S7, a plurality of screw holes 26 are formed around the hole formation regions 22. This screw hole forming step S7 includes a counterbore hole co-machining step S8, a female screw pilot hole machining step S9, and a female screw machining step S10, which will be described later.

[0041] The counterbore hole co-machining step S8 is a part of the threaded portion insertion hole forming step S4 and a part of the screw hole forming step S7. In this counterbore hole co-machining step S8, as shown in FIG. 7 , the temporary inner peripheral surface 34i of the temporary material 33 is brought into contact with the outer peripheral surface 24o of the main body material 23, and the temporary hole formation region 32 of the temporary material 33 is overlapped with the hole formation region 22 of the main body material 23 so that the position where the main body counterbore hole 26c is to be formed in the main body material 23 overlaps the position where the threaded portion insertion hole 36 is to be formed in the temporary material 33. Then, with the main body material 23 and the temporary material 33 in contact as described above, a counterbore hole as the threaded portion insertion hole 36 is machined in the temporary material 33 using a counterbore processing tool T such as a counterbore drill. The counterbore processing tool T has a conical apex. The angle θ of this apex coincides with the angle θ (see FIG. 9) of the conical portion 44 of the screw 41. The angle of the conical portion 44 of the screw 41 is the angle formed by a first generatrix of the conical portion 44 and a second generatrix of the conical portion 44 that is symmetrical to the first generatrix with respect to the screw axis Ag.

[0042] When the counterbore hole co-machining step S8 is completed and the counterbore tool T is withdrawn from the main body material 23 and the temporary material 33, the counterbore hole 36 formed in the temporary material 33 and the main body counterbore hole 26c formed in the main body material 23 appear, as shown in FIG. 8 . The central axis Ag of the main body counterbore hole 26c formed in the main body material 23 is located on the central axis Ag of the counterbore hole 36 formed in the temporary material 33. This central axis Ag coincides with the screw axis Ag described above. The angle of the apex of the main body counterbore hole 26c formed in the main body material 23 is an angle θ1 that is approximately the same as the angle θ of the apex of the counterbore tool T and the angle θ of the conical portion 44 of the screw 41. Meanwhile, the angle of the apex of the counterbore hole 36 formed in the temporary material 33 is an angle θ2 that is smaller than the angle θ1 of the apex of the main body counterbore hole 26c formed in the main body material 23 and the angle θ of the apex of the counterbore tool T. The angle of the apex of the countersunk hole 36 is the angle formed by a first generatrix on the surface of the countersunk hole 36 and a second generatrix on the surface of the countersunk hole 36 that is symmetrical to the first generatrix with respect to the central axis Ag. Furthermore, the inner diameter D2 of the countersunk hole 36 at the position of the provisional inner peripheral surface 34i is smaller than the inner diameter D1 of the main body countersunk hole 26c at the position of the main body outer peripheral surface 24o.

[0043] While the temporary workpiece 33 and the main body material 23 are being machined with the countersinking tool T, the amount of elastic deformation of the temporary workpiece 33 in the radial direction relative to the central axis Ag of the countersinking tool T is greater than the amount of elastic deformation of the main body material 23 in the radial direction relative to the central axis Ag of the countersinking tool T. This is thought to be due to the fact that the thickness t2 of the temporary workpiece 33 is thinner than the thickness t1 of the main body material 23, and further, the radial deformation restraining force of the countersinking tool T on the temporary workpiece 33 is small, etc. In this way, due to the difference between the elastic deformation amount of the temporary material 33 and the elastic deformation amount of the main material 23, when the countersinking tool T is pulled out from the main material 23 and the temporary material 33, as described above, the angle of the top of the countersink hole 36 formed in the temporary material 33 becomes an angle θ2 which is smaller than the angle θ1 of the top of the main countersink hole 26c formed in the main material 23 and the angle θ of the top of the countersinking tool T, and the inner diameter D2 of the countersink hole 36 at the position of the temporary inner surface 34i becomes smaller than the inner diameter D1 of the main countersink hole 26c at the position of the main body outer surface 24o.

[0044] When the counterbore hole machining step S8 is completed, the threaded portion insertion hole forming step S4 and the temporary material machining step S2 are completed, and the temporary strainer 31 is completed.

[0045] In the threaded hole forming step S7 of the main body material processing step S5, once the counterbore hole co-machining step S8 is completed, the aforementioned female thread pilot hole machining step S9 and female thread machining step S10 are carried out. In the female thread pilot hole machining step S9, a female thread pilot hole that connects to the main body counterbore hole 26c formed in the counterbore hole co-machining step S8 is machined in the main body material 23. In the female thread machining step S10, a female thread is formed on the inner surface of the female thread pilot hole. When the female thread machining step S10 is completed, the threaded hole forming step S7 and the main body material processing step S5 are completed, and the strainer main body 21 is completed.

[0046] As described above, once the temporary material processing step S2 and the main body material processing step S5 are completed, the two temporary strainers 31 are attached to the strainer main body 21 using a plurality of screws 41 (assembly step S11). In this assembly step S11, the temporary inner peripheral surfaces 34i of the two temporary strainers 31 are brought into contact with the main body outer peripheral surface 24o of the strainer main body 21. Next, the temporary hole formation region 32 of the first temporary strainer 31a is overlapped on the first hole formation region 22a of the strainer main body 21 so that the central axes Ag of the plurality of screw holes 26 in the strainer main body 21 and the central axes Ag of the plurality of threaded portion insertion holes 36 in the first temporary strainer 31a are aligned. Similarly, the temporary hole formation region 32 of the second temporary strainer 31b is overlapped with the second hole formation region 22b of the strainer body 21 so that the central axes Ag of the multiple screw holes 26 of the strainer body 21 and the central axes Ag of the multiple threaded portion insertion holes 36 of the second temporary strainer 31b are aligned. Then, the male thread portions 42 of the multiple screws 41 are inserted into the multiple threaded portion insertion holes 36 of each temporary strainer 31, and then screwed into the multiple threaded holes 26 of the strainer body 21.

[0047] With this, the strainer 20 is completed.

[0048] 9, after the countersink hole co-machining step S8 is completed and the countersink tool T is withdrawn from the main body material 23 and the temporary material 33, the inner diameter D2 of the countersink hole 36 at the provisional inner circumferential surface 34i is smaller than the inner diameter D1 of the main body countersink hole 26c at the main body outer circumferential surface 24o. Therefore, during the process of threading the screw 41 into the threaded hole 26 of the strainer main body 21, as shown in FIG. 5, the hole end 36e, which is the portion of the countersink hole 36 of the temporary strainer 31 on the provisional inner circumferential surface 34i side, is pressed by the conical portion 44 of the screw 41 and comes into close contact with the surface of the main body countersink hole 26c of the strainer main body 21. Therefore, in this embodiment, the pressing force of the temporary strainer 31 against the strainer main body 21 can be increased.

[0049] 5, in this embodiment, even after the screw 41 is threaded into the threaded hole 26 of the strainer body 21, the maximum inner diameter D3 of the threaded portion insertion hole 36 of the temporary strainer 31 is smaller than the maximum outer diameter D4 of the conical portion 44 of the screw 41. Therefore, in this embodiment, even after the screw 41 is threaded into the threaded hole 26 of the strainer body 21, a portion of the screw head 43 protrudes from the threaded portion insertion hole 36 of the temporary strainer 31 toward the temporary outer peripheral surface 34o of the temporary strainer 31. In this embodiment, the portion of the screw head 43 protrudes toward the temporary outer peripheral surface 34o of the temporary strainer 31 by, for example, 1 mm.

[0050] 10 , even after the screw 41c is screwed into the threaded hole 26 of the strainer body 21, a portion of the screw head 43 does not protrude toward the temporary outer peripheral surface 34o of the temporary strainer 31. In this case, a force F acts from the conical portion 44 of the screw 41c at a middle position in the thickness direction of the temporary strainer 31 on the surface of the threaded portion insertion hole (counterbore hole) 36. However, the force F does not substantially act from the conical portion 44 of the screw 41c at a position on the surface of the threaded portion insertion hole (counterbore hole) 36 at the temporary outer peripheral surface 34o of the temporary strainer 31 on the surface of the threaded portion insertion hole (counterbore hole) 36 in the direction of tightly contacting the temporary strainer 31 with the strainer body 21.

[0051] On the other hand, when a portion of the screw head 43 protrudes from the threaded portion insertion hole 36 of the temporary strainer 31 toward the temporary outer peripheral surface 34o of the temporary strainer 31 as in this embodiment, a force F in a direction that brings the temporary strainer 31 into tight contact with the strainer body 21 acts from the conical portion 44 of the screw 41 not only at a middle position in the thickness direction of the temporary strainer 31 on the surface of the threaded portion insertion hole (counterbore hole) 36, but also at a position on the temporary outer peripheral surface 34o of the temporary strainer 31 on the surface of the threaded portion insertion hole (counterbore hole) 36. Therefore, in this embodiment, the pressing force of the temporary strainer 31 against the strainer body 21 can be increased from this point of view as well.

[0052] 1, the completed strainer 20 is arranged at the boundary between the axial inlet-side flow path portion 16i and the annular flow path portion 17 so as to be cylindrical about the axis A. At this time, as shown in FIG. 2, the completed strainer 20 is arranged in the valve casing 10 so that both ends of the first temporary strainer 31a in the circumferential direction Dc and both ends of the second temporary strainer 31b in the circumferential direction Dc do not face the inlet flow path portion 18i.

[0053] After installation or repair of a boiler that generates steam to be supplied to a steam turbine or a main steam line connecting the boiler and the steam turbine, a large amount of foreign matter is mixed into the steam when the steam flows from the boiler to the main steam line. In this embodiment, the temporary strainer 31 in the strainer 20 captures most of the foreign matter contained in the steam that has flowed into the valve casing 10.

[0054] In this embodiment, as described above, the strainer 20 is arranged in the valve casing 10 so that both ends of the first temporary strainer 31a in the circumferential direction Dc and both ends of the second temporary strainer 31b in the circumferential direction Dc do not face the inlet flow path portion 18i. For this reason, in this embodiment, steam that has traveled straight through the inlet flow path portion 18i in the valve casing 10 does not directly collide with both ends of each temporary strainer 31 in the circumferential direction Dc. Therefore, in this embodiment, separation of each temporary strainer 31 from the strainer body 21 can be suppressed.

[0055] Steam is allowed to flow through the main steam line for a predetermined time, and when the amount of foreign matter in the steam decreases, the strainer 20 is removed from the valve casing 10, and then the temporary strainer 31 is removed from the strainer body 21. In this embodiment, at this time, the temporary strainer 31 can be easily removed from the strainer body 21 by removing the multiple screws 41 from the strainer 20 using a screwdriver or other screwdriver tool.

[0056] Thereafter, the strainer body 21 from which the strainer 20 has been removed is returned to the valve casing 10. This strainer body 21 captures most of the foreign matter contained in the steam that has flowed into the valve casing 10.

[0057] In this embodiment, the threaded hole 26 of the strainer body 21 does not penetrate from the outer peripheral surface 24o to the inner peripheral surface 24i of the strainer body 21, but has a hole bottom 26b. Therefore, when the temporary strainer 31 is removed from the strainer 20 and only the strainer body 21 is placed inside the valve casing 10, foreign matter in the steam located on the outer peripheral side of the strainer body 21 can be prevented from flowing into the inner peripheral side of the strainer 20 body through the threaded hole 26.

[0058] "Modified strainer" Because the thickness of the temporary strainer 31 is thinner than the thickness of the strainer body 21, the rigidity of the temporary strainer 31 is lower than the rigidity of the strainer body 21. For this reason, while the temporary strainer 31 is capturing foreign matter in the steam, a portion of the temporary strainer 31 may repeatedly come into contact with and separate from the strainer body 21 due to the influence of the steam. If a portion of the temporary strainer 31 repeatedly comes into contact with and separates from the strainer body 21 in this way, the temporary strainer 31 may become fatigued and may be damaged.

[0059] In the above embodiment, only both ends of the temporary strainer 31 in the axial direction Da and both ends of the temporary strainer 31 in the circumferential direction Dc are connected to the strainer body 21 by the screws 41. For this reason, while the temporary strainer 31 is capturing foreign matter in the steam, the middle part of the temporary strainer 31 in the axial direction Da may repeatedly come into contact with and separate from the strainer body 21. Therefore, as shown in Fig. 11 , in addition to both ends of the temporary strainer 31 in the axial direction Da and both ends of the temporary strainer 31 in the circumferential direction Dc, the middle part of the temporary strainer 31 in the axial direction Da may also be connected to the strainer body 21 by the screws 41.

[0060] In this case, the hole formation region 22 of the strainer body 21 has a first side hole formation region 22f and a second side hole formation region 22s. The second side hole formation region 22s is aligned with and spaced apart from the first side hole formation region 22f in the axial direction Da in which the cylindrical strainer body 21 extends. Some of the multiple steam passage holes 25 are formed in the first side hole formation region 22f. Another portion of the multiple steam passage holes 25 are formed in the second side hole formation region 22s. The temporary hole formation region 32 of the temporary strainer 31 has a first side temporary hole formation region 32f overlapping with the first side hole formation region 22f and a second side temporary hole formation region 32s overlapping with the second side hole formation region 22s. Some of the multiple temporary steam passage holes 35 are formed in the first side temporary hole formation region 32f. Another portion of the multiple temporary steam passage holes 35 are formed in the second side temporary hole formation region 32s. The temporary strainer 31 has, between the first side temporary hole formation region 32f and the second side temporary hole formation region 32s, an inter-region threaded portion insertion hole 36B that is one of the plurality of threaded portion insertion holes 36. The strainer body 21 has, between the first side hole formation region 22f and the second side hole formation region 22s, an inter-region threaded hole 26B that is one of the plurality of threaded holes 26 and communicates with the inter-region threaded portion insertion hole 36B.

[0061] The strainer 20 in the above embodiment and the modified example includes two temporary strainers 31. However, as shown in Fig. 12, the strainer 20 may include only one temporary strainer 31. In this case, one temporary strainer 31 is disposed around almost the entire circumference of the strainer body 21. Even in this modified example, it is preferable that the strainer 20 including this temporary strainer 31 is disposed inside the valve casing 10 so that both ends of the temporary strainer 31 in the circumferential direction Dc do not face the inlet flow path portion 18i.

[0062] The screw holes 26 in the above embodiment and each of the above modified examples do not penetrate from the outer circumferential surface 24o to the inner circumferential surface 24i of the strainer body 21, and have hole bottoms 26b. However, if the minimum inner diameter of the screw holes 26 is smaller than the minimum inner diameter of the steam passage holes 25 of the strainer body 21, the screw holes 26 may penetrate from the outer circumferential surface 24o to the inner circumferential surface 24i of the strainer body 21.

[0063] The present disclosure is not limited to the embodiments described above, and various additions, modifications, substitutions, partial deletions, etc. are possible within the scope of the conceptual idea and spirit of the present invention as derived from the content defined in the claims and their equivalents.

[0064] "Addendum" The strainer 20 in the above embodiment and modified examples can be understood, for example, as follows. (1) The strainer 20 in the first embodiment is The strainer 20 is disposed within a valve casing 10 in which a steam flow path 15 is formed. The strainer 20 comprises a cylindrical strainer body 21 having a main body outer peripheral surface 24o, a main body inner peripheral surface 24i that is back-to-back with the main body outer peripheral surface 24o, and a plurality of steam passage holes 25 that penetrate from the main body outer peripheral surface 24o to the main body inner peripheral surface 24i, a temporary strainer 31 that is disposed along the main body outer peripheral surface 24o of the strainer body 21 and has a temporary inner peripheral surface 34i that faces the main body outer peripheral surface 24o, a temporary outer peripheral surface 34o that is back-to-back with the temporary inner peripheral surface 34i, and a plurality of temporary steam passage holes 35 that penetrate from the temporary outer peripheral surface 34o to the temporary inner peripheral surface 34i and have inner diameters smaller than the inner diameters of each of the plurality of steam passage holes 25, and a plurality of screws 41 that attach the temporary strainer 31 along the main body outer peripheral surface 24o of the strainer body 21. In the temporary strainer 31, a temporary hole formation region 32 in which the plurality of temporary steam passage holes 35 are formed overlaps with the hole formation region 22 in which the plurality of steam passage holes 25 are formed in the strainer body 21. Each of the plurality of screws 41 has a cylindrical male thread portion 42 in which a male thread is formed, and a screw head 43 provided at the end of the base end side Dgb of the tip end side Dgt and base end side Dgb in the extension direction Dg of the male thread portion 42. The temporary strainer 31 further has a screw portion insertion hole 36 that penetrates from the temporary outer peripheral surface 34o to the temporary inner peripheral surface 34i of the temporary strainer 31 around the temporary hole formation region 32, and through which the male thread portion 42 of each of the plurality of screws 41 can pass but the screw head 43 cannot pass. The strainer body 21 further has a threaded hole 26 recessed from the outer peripheral surface 24o of the strainer body 21 toward the inner peripheral surface 24i of the strainer body 21 around the hole formation region 22 and communicating with the threaded portion insertion hole 36 of the temporary strainer 31. The threaded hole 26 of the strainer body 21 has a female threaded hole 26f into which the male threaded portion 42 passing through the threaded portion insertion hole 36 is screwed.

[0065] In this embodiment, the temporary strainer 31 can be easily removed from the strainer body 21 by removing the plurality of screws 41 from the strainer 20 using a screwdriver or other screwdriver tool.

[0066] (2) The strainer 20 in the second embodiment is In the strainer 20 of the first embodiment, the screw hole 26 does not penetrate from the outer circumferential surface 24o of the strainer body 21 to the inner circumferential surface 24i of the strainer body 21, and has a hole bottom 26b.

[0067] When the temporary strainer 31 is removed from the strainer 20 and only the strainer body 21 is placed inside the valve casing 10, foreign matter in the steam located on the outer periphery of the strainer body 21 can be prevented from flowing into the inner periphery of the strainer body 20 through the screw hole 26.

[0068] (3) The strainer 20 in the third embodiment is In the strainer 20 of the first embodiment or the second embodiment, each of the plurality of screws 41 is a flat head screw having a conical portion 44 whose outer diameter gradually decreases toward the tip side Dgt of the screw head 43. The threaded portion insertion hole 36 of the temporary strainer 31 is a conical countersunk hole whose inner diameter gradually decreases from the temporary outer peripheral surface 34o toward the temporary inner peripheral surface 34i of the temporary strainer 31, corresponding to the shape of the conical portion 44 and allowing at least a portion of the conical portion 44 to be accommodated.

[0069] By using flat head screws to connect the strainer body 21 and the temporary strainer 31, the pressing force between the strainer body 21 and the temporary strainer 31 can be increased.

[0070] (4) The strainer 20 in the fourth embodiment is In the strainer 20 of the first or second embodiment, the plurality of screws 41 are flat head screws having a conical portion 44 whose outer diameter gradually decreases toward the tip side Dgt of the screw head 43. The distance between the provisional outer peripheral surface 34o and the provisional inner peripheral surface 34i of the temporary strainer 31 is shorter than the distance between the end of the base side Dgb and the end of the tip side Dgt of the conical portion 44. The threaded portion insertion hole 36 of the temporary strainer 31 is a conical countersunk hole whose inner diameter gradually decreases from the provisional outer peripheral surface 34o toward the provisional inner peripheral surface 34i of the temporary strainer 31, corresponding to the shape of at least a part of the base side Dgb of the conical portion 44, and capable of accommodating at least a part of the base side Dgb of the conical portion 44. The screw hole 26 of the strainer body 21 corresponds to the shape of the tip side Dgt portion excluding at least a part of the base end side Dgb in the conical portion 44, and has a conical body countersunk hole 26c whose inner diameter gradually decreases from the body outer peripheral surface 24o toward the body inner peripheral surface 24i of the strainer body 21 so as to be able to accommodate the tip side Dgt portion excluding at least a part of the base end side Dgb in the conical portion 44. The female screw hole 26f of the strainer body 21 extends from the end of the body countersunk hole 26c on the side of the body inner peripheral surface 24i to the side of the body inner peripheral surface 24i.

[0071] By using flat head screws to connect the strainer body 21 and the temporary strainer 31, the pressing force between the strainer body 21 and the temporary strainer 31 can be increased.

[0072] (5) The strainer 20 in the fifth aspect is In the strainer 20 of the third or fourth aspect, the maximum inner diameter of the threaded portion insertion hole 36 of the temporary strainer 31 is smaller than the maximum outer diameter of the conical portion 44. A part of the conical portion 44 protrudes from the threaded portion insertion hole 36 of the temporary strainer 31 toward the temporary outer peripheral surface 34o of the temporary strainer 31.

[0073] In this embodiment, the pressing force between the strainer body 21 and the temporary strainer 31 can be increased.

[0074] (6) The strainer 20 in the sixth aspect is In the strainer 20 according to any one of claims 1 to 5 in any one of the first to fifth aspects, the hole formation region 22 of the strainer body 21 has a first side hole formation region 22f and a second side hole formation region 22s. The second side hole formation region 22s is aligned with and spaced apart from the first side hole formation region 22f in the extension direction of the cylindrical strainer body 21. Some of the steam passage holes 25 are formed in the first side hole formation region 22f. Another part of the steam passage holes 25 is formed in the second side hole formation region 22s. The temporary hole formation region 32 of the temporary strainer 31 has a first side temporary hole formation region 32f overlapping with the first side hole formation region 22f and a second side temporary hole formation region 32s overlapping with the second side hole formation region 22s. Some of the temporary steam passage holes 35 are formed in the first side temporary hole formation region 32f. Another portion of the plurality of temporary steam passage holes 35 is formed in the second side temporary hole formation region 32s. The temporary strainer 31 has an inter-region threaded portion insertion hole 36B, which is a portion of the plurality of threaded portion insertion holes 36, between the first side temporary hole formation region 32f and the second side temporary hole formation region 32s. The strainer body 21 has an inter-region threaded hole 26B, which is a portion of the plurality of threaded holes 26 and communicates with the inter-region threaded portion insertion hole 36B, between the first side hole formation region 22f and the second side hole formation region 22s.

[0075] In this embodiment, the pressing force between the strainer body 21 and the portion of the temporary strainer 31 between the first temporary hole formation region 32f and the second temporary hole formation region 32s can be increased.

[0076] The steam valves in the above-described embodiments and modifications can be understood, for example, as follows. (7) In the seventh aspect, the steam valve is The strainer includes a strainer according to any one of the first to sixth embodiments, the valve casing, a valve element that can move back and forth within the valve casing in an axial direction Da along which an axis A extends to open and close the flow path, and a valve rod that extends on the axis A in the axial direction Da and to which the valve element is connected. The flow path 15 includes an axial flow path section 16 centered on the axis A and extending in the axial direction Da, an annular flow path section 17 centered on the axis A around an axial inlet-side flow path section 16i that is a part of the axial flow path section 16 in the axial direction Da and is formed in an annular shape centered on the axis A around the axial inlet-side flow path section 16i and is in communication with the axial inlet-side flow path section 16i, an inlet flow path section 18i that extends from the annular flow path section 17 in a first radial direction Dr1 of radial directions Dr relative to the axis A and opens at the outer surface of the valve casing 10, and an outlet flow path section 18o that extends in either direction from an axial outlet-side flow path section 16o that is another part of the axial flow path section 16 in the axial direction Da and opens at the outer surface of the valve casing 10. The valve element 12 is arranged reciprocally within the axial inlet-side flow path section 16i. The strainer 20 is disposed at the boundary between the axial inlet side flow path portion 16i and the annular flow path portion 17 so that the strainer body 21 is cylindrical around the axis A.

[0077] In this embodiment, foreign matter contained in the steam that has flowed into the valve casing 10 can be captured by the strainer 20.

[0078] (8) In the eighth aspect, the steam valve is In the steam valve of the seventh aspect, an end of the temporary strainer 31 in the circumferential direction Dc with respect to the axis A does not face the inlet flow path portion 18i.

[0079] In this embodiment, steam that has traveled straight through the inlet flow path portion 18i in the valve casing 10 does not directly collide with the end of the temporary strainer 31 in the circumferential direction Dc. Therefore, in this embodiment, separation of the temporary strainer 31 from the strainer body 21 can be suppressed.

[0080] The method of manufacturing the strainer 20 in the above embodiment and modified examples can be understood, for example, as follows. (9) A method for manufacturing the strainer 20 in the ninth aspect includes the steps of: This is a manufacturing method of a strainer 20 to be placed in a valve casing 10 in which a steam flow path 15 is formed. This manufacturing method includes the following steps: a preparation step S1 for preparing a cylindrical main body material 23 having a main body outer peripheral surface 24o and a main body inner peripheral surface 24i and capable of being placed in the flow path 15; a temporary material 33 that can be attached along the main body outer peripheral surface 24o of the main body material 23 and has a temporary inner peripheral surface 34i facing the main body outer peripheral surface 24o and a temporary outer peripheral surface 34o that is back-to-back with the temporary inner peripheral surface 34i; and a plurality of screws 41; a main body material processing step S5 for processing the main body material 23 to form a strainer main body 21; a temporary material processing step S2 for processing the temporary material 33 to form a temporary strainer 31; and an assembly step S11 for attaching the temporary strainer 31 to the strainer main body 21 using the plurality of screws 41. Each of the plurality of screws 41 has a cylindrical male thread portion 42 on which a male thread is formed, and a screw head portion 43 provided at an end of the base end side Dgb of a tip end side Dgt and a base end side Dgb in an extension direction Dg of the male thread portion 42. The body material processing step S5 includes a steam passage hole forming step S6 of forming a plurality of steam passage holes 25 that penetrate from the body outer peripheral surface 24o to the body inner peripheral surface 24i within a predetermined hole formation region 22 of the body material 23, and a screw hole forming step S7 of forming screw holes 26 that are recessed from the body outer peripheral surface 24o toward the body inner peripheral surface 24i around the hole formation region 22 of the body material 23 and into which the male thread portion 42 of each of the plurality of screws 41 can be screwed. The temporary material processing process S2 includes a temporary steam passage hole forming process S3 for forming a plurality of temporary steam passage holes 35 that penetrate from the temporary outer peripheral surface 34o to the temporary inner peripheral surface 34i within a predetermined temporary hole formation area 32 of the temporary material 33 and have an inner diameter smaller than the inner diameter of each of the plurality of steam passage holes 25, and a screw portion insertion hole forming process S4 for forming a screw portion insertion hole 36 that penetrates from the temporary outer peripheral surface 34o to the temporary inner peripheral surface 34i around the temporary hole formation area 32 of the temporary material 33 and through which the male screw portion 42 of each of the plurality of screws 41 can pass but the screw head 43 cannot pass.In the threaded portion insertion hole forming step S4, the temporary inner peripheral surface 34i of the temporary material 33 is brought into contact with the main body outer peripheral surface 24o of the main body material 23, and when the temporary hole formation region 32 of the temporary material 33 is overlapped on the hole formation region 22 of the main body material 23, the threaded portion insertion hole 36 is formed in the temporary material 33 at a position that can communicate with the threaded hole 26 of the main body material 23. In the assembling step S11, after the temporary inner peripheral surface 34i is brought into contact with the main body outer peripheral surface 24o and the temporary hole formation region 32 is overlapped on the hole formation region 22, the male threaded portion 42 of the screw 41 is inserted into the threaded portion insertion hole 36 of the temporary strainer 31 and then screwed into the screw hole 26 of the strainer body 21.

[0081] In the strainer 20 manufactured in this manner, as with the strainer 20 in the first manner described above, the temporary strainer 31 can be easily removed from the strainer body 21 by removing multiple screws 41 from the strainer 20 using a screwdriver or other screwdriver tool.

[0082] (10) A method for manufacturing the strainer 20 in a tenth aspect includes the steps of: In the manufacturing method of the strainer 20 in the ninth aspect, in the screw hole forming step S7, the screw hole 26 is formed so as not to penetrate from the outer circumferential surface 24o of the main body material 23 to the inner circumferential surface 24i of the main body.

[0083] In the strainer 20 manufactured in this manner, as in the strainer 20 in the second manner described above, when the temporary strainer 31 is removed from the strainer 20 and only the strainer body 21 is placed inside the valve casing 10, foreign matter in the steam located on the outer periphery of the strainer body 21 can be prevented from flowing into the inner periphery of the body of the strainer 20 through the screw hole 26.

[0084] (11) A method for manufacturing the strainer 20 in an eleventh aspect includes the steps of: In the manufacturing method of the strainer 20 according to the ninth or tenth aspect, each of the plurality of screws 41 is a flat head screw having a conical portion 44 whose outer diameter gradually decreases toward the tip side Dgt of the screw head 43. The distance between the provisional outer peripheral surface 34o and the provisional inner peripheral surface 34i of the temporary strainer 31 is shorter than the distance between the end of the base side Dgb and the end of the tip side Dgt of the conical portion 44. The screw portion insertion hole 36 is a conical countersunk hole whose inner diameter gradually decreases from the provisional outer peripheral surface 34o toward the provisional inner peripheral surface 34i, corresponding to the shape of at least a part of the base side Dgb of the conical portion 44 and capable of accommodating at least a part of the base side Dgb of the conical portion 44. The screw hole 26 corresponds to the shape of the tip side Dgt portion excluding at least a part of the base end side Dgb of the conical portion 44, and has a conical main body counterbore hole 26c whose inner diameter gradually decreases from the main body outer peripheral surface 24o to the main body inner peripheral surface 24i of the strainer main body 21 so as to be able to accommodate the tip side Dgt portion excluding at least a part of the base end side Dgb of the conical portion 44. When forming the counterbore hole 36 in the threaded portion insertion hole forming step S4 and forming the main body counterbore hole 26c in the threaded hole forming step S7, the temporary inner peripheral surface 34i of the temporary material 33 is brought into contact with the main body outer peripheral surface 24o of the main body material 23, and the temporary hole formation region 32 of the temporary material 33 is overlapped on the hole formation region 22 of the main body material 23, and the counterbore hole 36 and the main body counterbore hole 26c are simultaneously machined.

[0085] In the strainer 20 manufactured in this embodiment, the pressing force between the strainer body 21 and the temporary strainer 31 can be increased, similar to the strainer 20 in the fourth embodiment described above. [Explanation of symbols]

[0086] 10: Valve casing 11: Valve seat 12: Valve body 13: Valve stem 15: Flow path 16: Axial flow passage 16i: Axis inlet side flow path section 16o: Axis outlet side flow path section 17: Annular flow path section 18i: Inlet flow passage 18o: Outlet flow path section 20: Strainer 21: Strainer body 22: Pore formation area 22a: First pore formation area 22b: Second pore forming area 22f: First side hole formation area 22s: Second side hole forming area 23:Main material 24o: Outer surface of main body 24i: Inner surface of main body 25: Steam passage hole 26: screw hole 26B: Inter-area screw holes 26c: Body counterbore 26f: Female screw hole 26b: Hole bottom 31: Temporary strainer 31a: First temporary strainer (or simply temporary strainer) 31b: Second temporary strainer (or simply temporary strainer) 32: Temporary pore formation area 32a: First pseudopore forming region 32b: Second pseudopore forming region 32f: First side pore formation region 32s: Secondary pore forming region 33:Temporary material 34o: Temporary outer surface 34i:Temporary inner peripheral surface 35: Temporary steam passage hole 36: Threaded insertion hole (counterbore hole) 36e: Hole end 36B: Inter-area screw insertion hole 41, 41c: Screws 42: Male thread 43: Screw head 44: Cone part A: Axis line Da: Axial direction Dc: Circumferential direction Dr: Radial direction Dr1: First radial direction Dr2: Second radial direction Ag: Screw axis (or central axis) Dg: Extending direction Dgt: Tip side Dgb:Proximal side F: Force T: Counterbore tool

Claims

1. A strainer disposed in a valve casing in which a steam flow path is formed, a strainer body having a cylindrical shape and including a main body outer peripheral surface, a main body inner peripheral surface that is back-to-back with the main body outer peripheral surface, and a plurality of steam passage holes that penetrate from the main body outer peripheral surface to the main body inner peripheral surface; a temporary strainer arranged along the outer peripheral surface of the strainer body, the temporary strainer having a temporary inner peripheral surface facing the outer peripheral surface of the strainer body, a temporary outer peripheral surface facing back-to-back with the temporary inner peripheral surface, and a plurality of temporary steam passage holes penetrating from the temporary outer peripheral surface to the temporary inner peripheral surface and having inner diameters smaller than the inner diameters of each of the plurality of steam passage holes; a plurality of screws for attaching the temporary strainer along the outer circumferential surface of the strainer body; Equipped with a temporary hole formation region in which the plurality of temporary steam passage holes are formed in the temporary strainer overlaps with a hole formation region in which the plurality of steam passage holes are formed in the strainer body, Each of the plurality of screws has a cylindrical male thread portion on which a male thread is formed, and a screw head portion provided at the end of the base end side of the tip end side and the base end side in the extension direction of the male thread portion, The temporary strainer further has a screw portion insertion hole that penetrates from the temporary outer peripheral surface to the temporary inner peripheral surface of the temporary strainer around the temporary hole formation area, and through which the male screw portions of each of the plurality of screws can pass but the screw heads cannot pass, The strainer body further has a screw hole recessed from the outer peripheral surface of the strainer body toward the inner peripheral surface of the strainer body around the hole formation region and communicating with the screw portion insertion hole of the temporary strainer, The screw hole of the strainer body has a female screw hole into which the male screw portion passing through the thread portion insertion hole is screwed. Strainer.

2. The strainer according to claim 1, The screw hole does not penetrate from the outer peripheral surface of the strainer body to the inner peripheral surface of the strainer body and has a hole bottom. Strainer.

3. The strainer according to claim 1, Each of the plurality of screws is a flat head screw having a conical portion whose outer diameter gradually decreases toward the tip end of the screw head, the threaded portion insertion hole of the temporary strainer corresponds to the shape of the conical portion, and is a conical countersunk hole whose inner diameter gradually decreases from the temporary outer peripheral surface to the temporary inner peripheral surface of the temporary strainer so that at least a part of the conical portion can be accommodated therein; Strainer.

4. The strainer according to claim 1, The plurality of screws are flat head screws having a conical portion whose outer diameter gradually decreases toward the tip end of the screw head, a distance between the provisional outer peripheral surface and the provisional inner peripheral surface of the provisional strainer is shorter than a distance between the base end side end and the tip end side end of the conical portion, the threaded portion insertion hole of the temporary strainer corresponds to the shape of at least a portion of the base end side of the conical portion, and is a conical countersunk hole whose inner diameter gradually decreases from the temporary outer peripheral surface toward the temporary inner peripheral surface of the temporary strainer so that at least a portion of the base end side of the conical portion can be accommodated therein; The screw hole of the strainer body corresponds to the shape of the tip side portion of the conical portion excluding at least a part of the base end side, and has a conical body countersunk hole whose inner diameter gradually decreases from the body outer peripheral surface toward the body inner peripheral surface of the strainer body so that the tip side portion of the conical portion excluding at least a part of the base end side can be accommodated, The female screw hole of the strainer body extends from the end of the body countersunk hole on the side of the inner circumferential surface of the body to the side of the inner circumferential surface of the body. Strainer.

5. The strainer according to claim 3, a maximum inner diameter of the threaded portion insertion hole of the temporary strainer is smaller than a maximum outer diameter of the conical portion, A part of the conical portion protrudes from the threaded portion insertion hole of the temporary strainer toward the temporary outer peripheral surface of the temporary strainer. Strainer.

6. The strainer according to claim 1, The hole formation region of the strainer body has a first side hole formation region and a second side hole formation region, the second side hole forming region is aligned with the first side hole forming region at an interval in the extension direction of the cylindrical strainer body, a part of the plurality of steam passage holes is formed in the first side hole formation region, another part of the plurality of steam passage holes is formed in the second side hole formation region, the temporary hole formation area of ​​the temporary strainer has a first side temporary hole formation area overlapping with the first side hole formation area and a second side temporary hole formation area overlapping with the second side hole formation area, a part of the plurality of temporary steam passage holes is formed in the first side temporary hole formation region; Another part of the plurality of temporary steam passage holes is formed in the second side temporary hole formation region, the temporary strainer has an inter-area threaded portion insertion hole, which is a part of the plurality of threaded portion insertion holes, between the first side temporary hole formation area and the second side temporary hole formation area, The strainer body has an inter-region threaded hole between the first side hole forming region and the second side hole forming region, the inter-region threaded portion insertion hole being a part of the plurality of threaded holes. Strainer.

7. A strainer according to any one of claims 1 to 6; the valve casing; a valve element reciprocating in an axial direction within the valve casing to open and close the flow path; a valve stem extending in the axial direction on the axis and connected to the valve body; Equipped with The flow path is an axial flow path portion extending in the axial direction around the axis; an annular flow path portion that is formed annularly around the axis around an axial inlet side flow path portion that is a part of the axial direction of the axial direction flow path portion and that is in communication with the axial inlet side flow path portion; an inlet flow path portion extending from the annular flow path portion in a first radial direction relative to the axis and opening at an outer surface of the valve casing; an outlet flow path portion extending in any direction from an axial outlet side flow path portion which is another part of the axial flow path portion in the axial direction and opening at an outer surface of the valve casing; and the valve element is arranged reciprocally within the axial inlet side flow path portion, The strainer is disposed at the boundary between the axial inlet side flow path portion and the annular flow path portion so that the strainer body is cylindrical around the axis. Steam valve.

8. 8. The steam valve according to claim 7, a circumferential end of the temporary strainer relative to the axis does not face the inlet flow path portion; Steam valve.

9. A method for manufacturing a strainer to be disposed in a valve casing having a steam flow passage formed therein, comprising: a preparation step of preparing a main body material that is cylindrical, has a main body outer peripheral surface and a main body inner peripheral surface, and can be placed in the flow path; a temporary material that can be attached along the main body outer peripheral surface of the main body material, and has a temporary inner peripheral surface that faces the main body outer peripheral surface and a temporary outer peripheral surface that is back-to-back with the temporary inner peripheral surface; and a plurality of screws; a main body material processing step of processing the main body material to form a strainer main body; a temporary material processing step of processing the temporary material to form a temporary strainer; an assembly process of attaching the temporary strainer to the strainer body using the plurality of screws; Run Each of the plurality of screws has a cylindrical male thread portion on which a male thread is formed, and a screw head portion provided at the end of the base end side of the tip end side and the base end side in the extension direction of the male thread portion, The main body material processing step includes: a steam passage hole forming step of forming a plurality of steam passage holes penetrating from the outer peripheral surface of the main body to the inner peripheral surface of the main body within a predetermined hole formation region of the main body material; a screw hole forming step of forming screw holes recessed from the outer peripheral surface of the main body toward the inner peripheral surface of the main body around the hole forming region of the main body material, into which the male thread portions of each of the plurality of screws can be screwed; Including, The temporary material processing step includes: a temporary steam passage hole forming step of forming a plurality of temporary steam passage holes that penetrate from the temporary outer peripheral surface to the temporary inner peripheral surface within a predetermined temporary hole formation region of the temporary material and have inner diameters smaller than the inner diameters of each of the plurality of steam passage holes; a threaded portion insertion hole forming process for forming threaded portion insertion holes that penetrate from the temporary outer peripheral surface to the temporary inner peripheral surface around the temporary hole formation region of the temporary blank, through which the male threaded portions of each of the plurality of screws can pass but the screw heads cannot pass; Including, In the threaded portion insertion hole forming step, the temporary inner peripheral surface of the temporary material is brought into contact with the main outer peripheral surface of the main material, and when the temporary hole formation region of the temporary material is superimposed on the hole formation region of the main material, the threaded portion insertion hole is formed in the temporary material at a position that can communicate with the screw hole of the main material, In the assembling step, the temporary inner peripheral surface is brought into contact with the outer peripheral surface of the main body, the temporary hole formation area is overlapped with the hole formation area, and then the male thread portion of the screw is inserted into the thread portion insertion hole of the temporary strainer and then screwed into the screw hole of the strainer main body. Strainer manufacturing method.

10. 10. The method for manufacturing a strainer according to claim 9, In the screw hole forming step, the screw holes are formed so as not to penetrate from the outer peripheral surface of the main body to the inner peripheral surface of the main body material. Strainer manufacturing method.

11. The method for manufacturing a strainer according to claim 9 or 10, Each of the plurality of screws is a flat head screw having a conical portion whose outer diameter gradually decreases toward the tip end of the screw head, a distance between the provisional outer peripheral surface and the provisional inner peripheral surface of the provisional strainer is shorter than a distance between the base end side end and the tip end side end of the conical portion, the threaded portion insertion hole is a conical countersunk hole whose inner diameter gradually decreases from the provisional outer peripheral surface toward the provisional inner peripheral surface, the countersunk hole corresponding to the shape of at least a portion of the base end side of the conical portion and capable of accommodating at least a portion of the base end side of the conical portion; The screw hole corresponds to the shape of the tip side portion of the conical portion excluding at least a part of the base end side, and has a conical body counterbore hole whose inner diameter gradually decreases from the body outer peripheral surface of the strainer body toward the body inner peripheral surface so that the tip side portion of the conical portion excluding at least a part of the base end side can be accommodated, When forming the counterbore hole in the threaded portion insertion hole forming step and forming the main body counterbore hole in the screw hole forming step, the temporary inner peripheral surface of the temporary material is brought into contact with the main body outer peripheral surface of the main body material, and the counterbore hole and the main body counterbore hole are machined together in a state where the temporary hole formation area of ​​the temporary material is overlapped on the hole formation area of ​​the main body material. Strainer manufacturing method.

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