STEAM VALVE

Abstract

A steam valve (1) with: a valve housing (2), a valve plate (11) arranged within the valve housing (2), a cylinder (14) arranged on a bottom side of the valve housing (2) and having an upwardly extending piston rod (14b), and a valve stem which vertically penetrates a lower portion of the valve housing (2) and whose one end is coupled to the piston rod (14b) via a coupling (13) and whose other end is coupled to the valve plate (11), characterized in that the steam valve (1) comprises: a cover (40) having a larger diameter than the piston rod (14b) and the coupling (13) and configured to separate the piston rod (14b) and the coupling (13) from each other by being arranged between the piston rod (14b) and the coupling (13), and a tubular skirt (50) depending from a peripheral portion of the cover (40) and surrounding a periphery of a head portion of the piston rod (14b), wherein the cylinder (14) is supported by the valve housing (2) via a yoke (15), a base plate (15b) of the yoke (15), to which the cylinder (14) is attached, has an opening (15d) through which the piston rod (14b) extends, and a tubular skirt rising to surround a periphery of the opening (15d) on an inner side of the skirt (50) is disposed on an upper surface of the bottom plate (15b) of the yoke (15).

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention

[0001] The present invention relates to a steam valve installed in, for example, a steam turbine and used for interrupting steam or adjusting the flow rate, and more particularly to a steam valve having a cylinder for driving a valve disc on the underside of a valve body. 2. Description of the related art

[0002] A steam valve described in JP H11 343811 A is cited as a related art. The steam valve disclosed in this document is configured such that a valve seat is installed facing upward, and a valve disc is raised and lowered relative to the valve seat. In the steam valve according to this document, the upper surface of the valve seat is flush with or higher than an inlet passage for steam in a valve body. Therefore, a device is configured such that a drain flows to the inlet side of the steam and does not readily remain near the valve seat.

[0003] Patent Document 2 discloses that the valve driving device is configured such that the valve stem of a valve body is connected to the piston in an oil cylinder via the oil cylinder spring housing. When the valve is opened, an operating rod held in the oil cylinder spring housing is moved to the valve-opening position by the piston in the oil cylinder against the return force of the operating spring. When the valve is closed, the operating rod is returned to the valve-closing position by the return force of the operating spring. A drain port for draining the water accumulated in the oil cylinder spring housing is provided at the bottom of the oil cylinder spring housing.

[0004] Patent Document 3 discloses that when a piston in a cylinder body moves from a short contraction state to a long extension state, air in a low-pressure chamber flows into the air chamber of a cover through a vent hole. The outflowing air expands the volume of the air chamber, causing the cover to swell. When the piston moves from the long extension state to the short contraction state, the air in the expanded air chamber is sucked into the cylinder body through the vent hole, causing the cover to shrink. State of the art documentPatent document Patent Document 1: JP H11 343811 A Patent Document 2: JP 2005-98319 A Patent Document 3: JP H06-280826 A SUMMARY OF THE INVENTION

[0005] It is difficult to completely prevent steam flowing inside the valve body from escaping from a gap between the valve body and a valve stem to the outside of the valve body. The temperature outside the valve body is lower than the temperature inside the valve body. Therefore, the steam escaping from the valve body condenses into a drain. If a cylinder that drives the valve disc is arranged at the bottom of the valve body, the drain runs along the valve stem and reaches the cylinder, and the cylinder may corrode due to the stagnant drain.

[0006] An object of the present invention is to provide a steam valve that can prevent stagnation of a drain at a cylinder mounted on the bottom of a valve body and thus prevent the occurrence of corrosion of the cylinder.

[0007] To achieve the above-mentioned object according to the present invention, a steam valve is provided according to independent claims 1 and 2. An advantageous modification can be found in dependent claim 3.

[0008] According to the present invention, the stagnation of the drain at the cylinder mounted on the bottom of the valve body can be prevented, and thus the occurrence of corrosion on the cylinder can be prevented. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic diagram of an example of a steam turbine plant in which a steam valve according to an embodiment of the present invention is applied, Fig. 2 is an external view illustrating a general configuration of the steam valve according to an embodiment of the present invention, Fig. 3 is a sectional view showing an internal structure of main parts of the Fig. 2 shows the steam valve, Fig. 4 is an enlarged view showing a configuration of a coupling portion between a valve stem and a cylinder in a Fig. 2 shown steam check valve and is shown, Fig. 5 is a plan view of a cover attached to the Fig. 2 shown steam check valve is provided, Fig. 6 is a sectional view of the cover, the sectional view being taken in an arrow direction along a line VI-VI in Fig. 5 is recorded, Fig. 7 is a plan view of a border attached to the Fig. 2 shown steam check valve is provided, Fig. 8 is a partial view of the border, the partial view being taken in the direction of the arrow along a line VIII-VIII in Fig. 7 is recorded, Fig. 9 is a plan view of a bezel attached to the Fig. 2 shown steam check valve is attached, and Fig. 10 is a partial view of the enclosure, the partial view being taken in an arrow direction along a line XX in Fig. 9 is recorded. DESCRIPTION OF THE PREFERRED EMBODIMENT

[0009] An embodiment of the present invention will be described below with reference to the drawings. - Steam turbine plant -

[0010] Fig. 1 is a schematic diagram of an example of a steam turbine plant in which a steam valve according to an embodiment of the present invention is applied. In the steam turbine plant of the figure, main steam generated in a boiler B is supplied to a first turbine (high-pressure turbine) T1 via a main steam pipe P1 and drives the first turbine T1. The steam that has driven the first turbine T1 is introduced into a reheater R via a return pipe P2 and heated by the reheater R, then supplied to a second turbine (medium-pressure turbine) T2 via a reheater steam pipe P3 and drives the second turbine T2. The rotating shafts of the first turbine T1 and the second turbine T2 are coupled to each other. Typically, a third turbine (low-pressure turbine) is often additionally coaxially coupled to the first turbine T1 and the second turbine T2.Furthermore, the rotating shafts of the first turbine T1 and the second turbine T2 are coupled, for example, to a rotating shaft of a generator (not shown). The generator is driven by the first turbine T1 and the second turbine T2 to generate electrical power.

[0011] The main steam pipe P1 is equipped with a main steam shutoff valve V1. The reheater steam pipe P3 is equipped with a reheater steam shutoff valve V2. The steam supplied from boiler B to the first turbine T1 can be shut off by the main steam shutoff valve V1. The steam supplied from the reheater R to the second turbine T2 can be shut off by the reheater steam shutoff valve V2. - Steam valve -

[0012] Fig. 2 is an external view showing a general configuration of the steam valve according to an embodiment of the present invention. Fig. 3 is a sectional view showing the internal structure of the main parts of the Fig. 2. The steam valve 1 shown in these figures can, for example, be connected to at least one of the main steam shut-off valve V1 and the reheater steam shut-off valve V2 in the example of Fig. 1. The steam valve 1 is a composite valve obtained by combining a steam control valve 20 with a steam shut-off valve 10. As shown in Fig. 3, the steam control valve 20 and the steam shut-off valve 10 are arranged so that they are vertically opposite each other. Fig. 3 shows a valve closure state of the steam control valve 20 and the steam check valve 10. The steam check valve 10 is normally open (fully open). However, during a turbine shutdown, the steam check valve 10 is closed (fully closed) to cut off the supply of steam to the steam turbine. When the steam turbine resumes operation, the steam check valve 10 is reopened. The steam control valve 20 controls the flow rate of steam supplied to the steam turbine according to the opening degree of the steam control valve 20. - Steam control valve -

[0013] The steam control valve 20 includes a valve body 2, a valve seat 3, a valve disc 21, a valve stem 22, an auxiliary valve 23, and a cylinder 24. The valve body 2 is a common valve box for the steam control valve 20 and the steam check valve 10 and is a hollow body with a steam inlet 4 and a steam outlet (not shown). An upper portion of the valve body 2 is open. However, this opening is closed by an upper cover 2a, which is fastened by a plurality of sets of bolts and nuts 5. The valve seat 3 is located within the valve body 2 and is fixed to an inner wall of the valve body 2. The valve seat 3 is also shared by the steam control valve 20 and the steam check valve 10.

[0014] The cylinder 24 is, for example, a hydraulic cylinder. The cylinder 24 is supported outside the valve housing 2 and on the top of the valve housing 2, or in the present example, from the upper surface of the upper cover 2a of the valve housing 2 via a frame-shaped yoke (or lantern) 25. The upper cover 2a and the yoke 25 are fastened together by bolts. Similarly, a cylinder tube of the cylinder 24 and the yoke 25 are also fastened together by bolts. A piston rod of the cylinder 24 extends downward into a space inside the yoke 25. The valve stem 22 is coupled to a distal end of the piston rod of the cylinder 24 via a coupling. The valve stem 22 perpendicularly penetrates the top cover 2a of the valve housing 2. The sub-valve 23 is attached to a lower end of the valve rod 22, which is located inside the valve housing 2. This secondary valve 23 is in engagement with the valve plate 21.

[0015] The valve disc 21 is a tubular member. The valve disc 21 is vertically movable and guided by a guide tube 27 bolted to the lower surface of the upper cover 2a. The valve disc 21 thus reciprocates with respect to the valve seat 3. The valve disc 21 has a partition wall 21a provided at an intermediate portion thereof in an up-down direction, so that a space within the valve disc 21 is vertically separated by the partition wall 21a. However, a central portion of the partition wall 21a is open, and this opening is closed by the sub-valve 23. The sub-valve 23 is clamped with respect to the valve disc 21 by a thrust ring 26 with some clearance.

[0016] When the cylinder 24 retracts, the sub-valve 23 separates from the partition 21a and opens the opening. Subsequently, the valve disc 21 is raised above the sub-valve 23, and the valve disc 21 separates from the valve seat 3, so that the steam control valve 20 is open. Conversely, when the cylinder 24 expands, the valve disc 21 is lowered and sits on the valve seat 3. Subsequently, the sub-valve 23 closes the opening of the partition 21a and presses the valve disc 21 against the valve seat 3, so that the steam control valve 20 is closed.

[0017] When the steam control valve 20 is open, a differential pressure across the valve becomes a resistance to the operation of the valve disc 21. However, since the sub-valve 23, which has a small pressure-receiving area, opens first, the differential pressure across the valve disc 21 is reduced, and the valve disc 21 operates smoothly. The flow rate of steam supplied to the steam turbine is controlled by adjusting the opening degree of the steam control valve 20 (i.e., a clearance between the valve disc 21 and the valve seat 3) by the cylinder 24 in a state where the steam check valve 10 is open. - Steam check valve -

[0018] Fig. 4 is an enlarged view in which a configuration of a coupling portion between the valve stem and the cylinder in the vapor lock valve is extracted and shown. As shown in Fig. 3 and Fig. 4, the steam check valve 10 comprises the valve housing 2 and the valve seat 3 together with the steam control valve 20 as well as a valve plate 11, a valve stem 12 and a cylinder 14.

[0019] The cylinder 14 is a hydraulic cylinder. The cylinder 14 is arranged outside the valve body 2 and at the bottom of the valve body 2 and is supported by a frame-shaped yoke (or lantern) 15 from the bottom of the valve body 2. The yoke 15 is similar in configuration to the yoke 25 of the steam control valve 20 and is a welded structure having a top surface 15a and a bottom surface 15b connected by a plurality of columns (three columns in the present example). The top surface 15a of the yoke 15 and the bottom surface of the valve body 2 are fastened together by bolts. Similarly, the bottom plate 15b of the yoke 15 and a cylinder tube 14a of the cylinder 14 are fastened together by bolts. The top 15a and bottom plates 15b of the yoke 15 have the shape of a circular ring (or donut) and have openings 15c and 15d in their centers.A piston rod 14b of the cylinder 14 extends through the opening 15d of the base plate 15b, to which the cylinder 14 is attached. The valve stem 12 extends through the opening 15c of the top surface 15a, to which the valve housing 2 is attached.

[0020] The piston rod 14b of the cylinder 14 extends upward in a space within the yoke 15. One end (lower end) of the valve stem 12 is coupled to a distal end of the piston rod 14b, that is, an upper end of the piston rod 14b, via a coupling 13. The coupling 13 is divided into two in a circumferential direction (that is, viewed from above or below), and two C-shaped parts surround a stepped portion of the lower end portion of the valve stem 12. The coupling 13 is fixedly connected to the lower end of the valve stem 12 by coupling these two parts together. The piston rod 14b and the valve stem 12 are connected to each other by fastening the coupling 13 thus attached to the valve stem 12 to a head portion of the piston rod 14b with bolts.

[0021] The valve stem 12 is axially slidably inserted into a bushing 16 fixed to a lower portion (bottom plate) of the valve housing 2 and vertically penetrates the lower portion of the valve housing 2. The valve disc 11 is connected to another end (upper end) of the valve stem 12, which is located inside the valve housing 2 ( Fig. 3).

[0022] The valve disc 11 has a lower surface formed as a downwardly projecting curved surface. The valve disc 11 is located within the valve disc 21 of the steam control valve 20 and is higher than the valve seat 3. When the cylinder 14 retracts, the valve disc 11 moves vertically forward and retracts with respect to the valve seat 3. When the valve disc 11 is lowered and the curved surface of the valve disc 11 sits on the valve seat 3, the steam check valve 10 is closed. When the valve disc 11 is raised and separated from the valve seat 3, the steam check valve 10 is open. - Cylinder protection mechanism -

[0023] While the steam valve 1 is open and steam is supplied to the steam turbine, some of the steam flowing through the interior of the valve body 2, for example, from a space between the bushing 16 and the valve stem 12, may leak to the outside of the valve body 2. Since the valve stem 12 is slidable with respect to the bushing 16, it is difficult to completely stop the flow of steam between the bushing 16 and the valve stem 12. A temperature outside the valve body 2 is lower than a temperature inside the valve body 2. Therefore, the steam escaping from the valve body 2 condenses in a drain. This drain flows downward along the valve stem 12. If the drain reaches the cylinder 14 along the valve stem 12 and remains there, the drain may corrode components of the cylinder 14.In the present embodiment, a collar 17 is attached to the valve stem 12 outside the valve housing 2, covering an upper portion of the coupling 13. This provides a structure in which the collar 17 acts like an umbrella, making it difficult for water drops to fall onto the coupling 13, allowing the drain to pass between the collar 17 and the valve stem 12. There is also a possibility that the drain flowing on the upper surface of the collar 17 toward an outer periphery thereof may circulate to the lower surface of the collar 17 and adhere to the surface of the valve stem 12 again.

[0024] According to the presentation in Fig. 4, the steam check valve 10 is provided with a cover 40, a skirt 50, a collar 60, a slot 70, and a drain pan 80 to prevent the drain from flowing over the valve stem 12 to the cylinder 14. These elements each protect the cylinder 14 from the drain. - Cover.

[0025] Fig. 5 is a top view of the cover. Fig. 6 is a sectional view of the cover, the sectional view being taken in an arrow direction along a line VI-VI in Fig. 5. As shown in these figures, the cover 40 is a disc-shaped member and is surrounded by the head portion of the piston rod 14b and the coupling 13 from above and below. In this case, as shown in Fig. 4, the upper surface of the head portion of the piston rod 14b has a circular protrusion portion at its center, and an annular spacer 18 is disposed between a peripheral portion of this protrusion portion and the cover 40. The protrusion portion of the piston rod 14b is inserted inside the annular spacer 18, so that the piston rod 14b and the spacer 18 are arranged relative to each other by a structure commonly referred to as a socket and spigot.

[0026] A central portion of the upper surface of the cover 40 is provided with a circular projection portion 41 ( Fig. 6). This projection portion 41 is inserted into the annular coupling 13, so that the cover 40 and the coupling 13 are arranged with respect to each other by a socket-and-pin structure ( Fig. 4). Similarly, a central portion of the lower surface of the cover 40 is provided with a circular projection portion 42 ( Fig. 6). This projection portion 42 is inserted into the annular spacer 18, so that the cover 40 and the spacer 18 are arranged with respect to each other by a socket-and-pin structure ( Fig. 4). The cover 40 is thus concentrically aligned with the coupling 13 and the piston rod 14b.

[0027] Regarding a fastening structure for the cover 40, a plurality of through holes 43 (six through holes 43 in the present example) penetrating in the up-down direction (thickness direction) to surround the peripheries of the upper and lower protrusion portions 41 and 42 are provided on the cover 40 at equal intervals in a circumferential direction. A plurality of through holes having a similar diameter to the through holes 43 are also provided on the coupling 13 and the spacer 18 to correspond to the through holes 43. A plurality of bolt holes are provided on the upper surface of the piston rod 14b to correspond to the through holes 43.The cover 40 is integrally fixed to the clutch 13, the spacer 18, and the piston rod 14b by aligning the positions of the through holes of the clutch 13, the cover 40, and the spacer 18 with the bolt holes of the piston rod 14b, and inserting and screwing bolts 19 into the respective holes. Incidentally, a peripheral portion in the upper surface of the cover 40 is provided with a plurality of through holes 44 (ten through holes 44 in . Fig. 5) for coupling with the border 50 at equal intervals in the circumferential direction.

[0028] The diameter of the cover 40 is set larger than the diameter of the clutch 13 and the piston rod 14b, as well as the diameter of the opening 15d of the bottom plate 15b of the yoke 15. Furthermore, the cover 40 is a solid structure with no openings except for the above-described through holes 43 and 44, including a central portion thereof. Therefore, the cover 40 separates the clutch 13 and the piston rod 14b from each other by being disposed between the clutch 13 and the piston rod 14b, and the cover 40 protrudes outward in a radial direction and extends in a horizontal direction from peripheral portions of the clutch 13 and the piston rod 14b. - Border -

[0029] Fig. 7 is a top view of the border. Fig. 8 is a partial view of the border, the partial view being taken in the direction of the arrow along a line VIII-VIII in Fig. 7. As shown in these figures, the skirt 50 includes a main body 51 and a flange 52. The main body 51 has a configuration configured by bending a thin plate, thereby forming the thin plate into a tubular shape. The outer diameter (diameter) of the tubular main body 51 is approximately equal to or slightly smaller than the diameter of the cover 40, and is larger than the diameter of the coupling 13 and the piston rod 14b, as well as the diameter of the opening 15d of the bottom plate 15b of the yoke 15. The flange 52 is an annular member. The flange 52 is attached to an upper end of the inner peripheral surface of the tubular main body 51 by welding, for example.The upper surface of the flange 52 is provided with a plurality of threaded holes 53 (in this example, ten threaded holes 53) to correspond to the through holes 44 of the cover 40. The surround 50 is integrally fixed to the cover 40 by abutting the flange 52 against the lower surface of the cover 40, aligning the positions of the threaded holes 53 with the through holes 44, and fastening screws 54 (Fig. Fig. 4).

[0030] In the configuration described above, the main body 51 of the skirt 50 hangs from the peripheral portion of the cover 40 and surrounds the periphery (the entire periphery) of the head portion of the piston rod 14b, as shown in Fig. 4. A lower end of the main body 51 of the skirt 50 is lowered to a height almost corresponding to the upper surface of the bottom plate 15b of the yoke 15 in a state in which the cylinder 14 is retracted, that is, in a state in which the steam check valve 10 is closed ( Fig. 4).

[0031] Incidentally, in the present embodiment, the skirt 50 is divided into two parts in a circumferential direction and, viewed in plan view, is formed by two C-shaped parts. Brackets 55 projecting outward in the radial direction are provided at the respective end portions in the circumferential direction of the respective parts. The skirt 50 is formed in a tubular shape by connecting the brackets 55 at two upper and lower positions by bolts 56. - Border -

[0032] Fig. 9 is a plan view of the enclosure. Fig. 10 is a partial view of the enclosure, the partial view being taken in an arrow direction along a line XX in Fig. 9. As shown in these figures, the casing 60 includes a main body 61 and a flange 62. The main body 61 has a configuration configured by bending a thin plate, thereby forming the thin plate into a tubular shape. The outer diameter (diameter) of the main body 61 and the flange 62 is smaller than the diameter of the cover 40 and the inner diameter (diameter) of the skirt 50. The inner diameter (diameter) of the main body 61 and the flange 62 is larger than the diameter of the spacer 18 and the piston rod 14b. The flange 62 is an annular member. The flange 62 is attached to a lower end of the tubular main body 61 by welding, for example. The flange 62 is provided with a plurality of through holes 63 (ten through holes 63 in the present example) at equal intervals in a circumferential direction.The bezel 60 is fixed to the bottom plate 15b of the yoke 15 by having the flange 62 abut the upper surface of the bottom plate 15b of the yoke 15 so as to surround the opening 15d and by fastening screws 64 (. Fig. 4) which pass through the through holes 63.

[0033] In the configuration described above, the main body 61 of the casing 60 rises from the upper surface of the bottom plate 15b of the yoke 15 and surrounds the periphery (the entire periphery) of the opening 15d. An upper end of the main body 61 of the casing 60 is arranged at a height close to the lower surface of the cover 40, for example, at a height between a lower end of the spacer 18 and the lower surface of the cover 40 in a state in which the cylinder 14 is retracted, that is, in a state in which the steam check valve 10 is closed ( Fig. 4).

[0034] Incidentally, the bezel 60, like the rim 50, is divided into two parts in a circumferential direction and, viewed in plan view, is formed by two C-shaped parts. Brackets 65 projecting outward in the radial direction are provided at the respective end portions in the circumferential direction of the respective parts. The bezel 60 is formed in a tubular shape by connecting the brackets 65 at two upper and lower positions by bolts 66. - Slot -

[0035] As in Fig.As shown in FIG. 4, the slot 70 is formed in a ring shape in the upper surface of the bottom plate 15b of the yoke 15 and surrounds the peripheries (entire peripheries) of the opening 15d and the flange 62 of the bezel 60. The cross-sectional shape of the slot 70 is a U-shape open upward. The slot 70 is recessed with respect to the upper surface of the bottom plate 15b of the yoke 15. A circle described by a center line of the slot 70 corresponds to the diameter of the main body 51 of the bezel 50. The slot 70 is thus perpendicularly opposed to the lower end of the main body 51 of the bezel 50. - Drain pan -

[0036] The drain pan 80 is formed in a ring shape at a lower portion of the yoke 15 so as to surround the circumference (the entire circumference) of the yoke 15. The diameter of an inner circumference of the annular drain pan 80 is larger than a maximum diameter of the cylinder tube 14a. Thus, a gap is provided between the cylinder 14 and the drain pan 80. The drain pan 80 has an annular mounting seat 82 mounted on an inner peripheral portion thereof. The drain pan 80 is fixed to the bottom plate 15b of the yoke 15 by abutting the mounting seat 82 against the lower surface of the bottom plate 15b and fastening the mounting seat 82 with bolts. A drain 81 is formed in the bottom plate 15b of the yoke 15 (in the present example, within a plate thickness range of the bottom plate 15b). This drain 81 connects the slot 70 and the drain pan 80. - Wastewater separation operation -

[0037] During operation of the steam turbine, the interior of the valve body 2 is filled with the steam supplied to the steam turbine. Since the valve stem 12 is a sliding part, it is difficult to achieve a complete seal between the valve stem 12 and the bushing 16, and some steam may flow between the valve stem 12 and the bushing 16 and leak out of the valve body 2. The steam leaking out of the valve body 2 condenses into a drain due to a sharp temperature drop. The drain runs down along the valve stem 12. The drain runs down the valve stem 12, is received by the collar 17, and may pass through the outer circumference or the inner circumference of the collar 17 and over the collar 17. The drain running down the collar 17 and the valve stem 12 reaches the coupling 13 and may pass through the inner or outer circumference of the coupling 13.However, the clutch 13 and the piston rod 14b are separated from each other by the disc-shaped cover 40. Therefore, the drain passing through the clutch 13 is securely received by the cover 40. The drain received by the cover 40 can only escape outward in the radial direction and therefore flows along the upper surface of the cover 40 to the outer peripheral side. Since the skirt 50 hangs from the peripheral portion of the cover 40, the drain guided to the periphery of the cover 40 flows downward along the skirt 50 without reaching the lower surface of the cover 40. Then, the drain is introduced into the slot 70 provided on the bottom plate 15b of the yoke 15 and separated into the drain pan 80 via the drain 81. Even if the drain overflows from the slot 70 or adheres to the inner peripheral side of the slot 70, the casing 60 encloses the entire circumference of the opening 15d of the bottom plate 15b of the yoke 15.Thus, the outflow is dammed at the base plate 15b by the enclosure 60 without passing through the opening 15d into the cylinder 14. - Effects - (1) According to the present embodiment, the cover 40 separates the clutch 13 and the piston rod 14b from each other. Thus, the drain flowing through the clutch 13 does not come into contact with the piston rod 14b. Since the skirt 50 hangs from the cover 40, the drain flowing on the upper surface of the cover 40 cannot reach the lower surface of the cover 40, and the drain can be separated and introduced into the upper surface of the bottom plate 15b of the yoke 15 without coming into contact with the piston rod 14b. Consequently, the drain can be prevented from remaining on the cylinder 14 attached to the bottom of the valve body 2, thereby preventing the occurrence of corrosion on the cylinder. (2) Furthermore, the drain flowing down the skirt 50 and introduced into the upper surface of the bottom plate 15b is received by the slit 70 opposite the skirt 50 and introduced into the drain pan 80 via the drain 81. By holding the drain in the drain pan 80, the drain can be more reliably prevented from remaining on the cylinder 14. In addition, since the drain pan 80 is attached to the bottom plate 15b of the yoke 15 through the annular attachment seat 82, the drain is introduced into the drain pan 80 even when the drain runs around the outer peripheral surface of the bottom plate 15b from the upper surface to the lower surface of the bottom plate 15b. (3) Even if the drain introduced through the cover 40 and the skirt 50 on the upper surface of the bottom plate 15b flows to the inner peripheral surface via the slit 70, the drain is dammed by the skirt 60 and does not flow through the opening 15d of the bottom plate 15b. This also contributes to preventing the drain from reaching the cylinder 14, which in turn leads to rust prevention of the cylinder 14.

[0038] It should be noted that it is not absolutely necessary to install the casing 60, the slot 70, the drain pan 80, and the drain 81 in the steam valve 1 as long as the essential effect (1) described above is obtained. For example, a configuration may be adopted such that the drain is lowered below the steam valve 1 from the bottom plate 15b of the yoke 15 or from the skirt 15, and the drain is collected in a pan installed separately from the steam valve 1. - Modifications -

[0039] In the aforementioned embodiment, the cover 40 and the bezel 50 are joined together as separate parts. However, the cover 40 and the bezel 50 may be formed integrally with each other, that is, as one member. While the bezel 50 and the bezel 60 have a halved structure, the bezel 50 and the bezel 60 may also be formed integrally.

[0040] The skirt 50 may have a configuration capable of vertically extending and retracting, for example, by adopting a telescopic structure or a bellows structure, and a lower end of the skirt 50 may be connected to the bottom plate 15b of the yoke 15 (for example, on the inner peripheral side of the slot 70). In this case, no gap is formed between the skirt 50 and the bottom plate 15b regardless of an extended or retracted state of the cylinder 14, and therefore the skirt 50 can also serve as the collar 60. Of course, if the skirt 50 can also serve as the collar 60, the collar 60 may be omitted.

[0041] In the description, a case where the steam valve 1 is a composite valve in which the steam control valve 20 is added to the steam check valve 10 is set as an example for the application of the invention. However, the present invention is also applicable to a steam check valve without a steam control valve or a steam control valve without a steam check valve. Even in a steam check valve without a steam control valve or a steam control valve without a steam check valve, the cylinder is often installed at the bottom of the valve body due to its relationship with other components of a steam piping system of a steam turbine plant. In this case, a corrosion problem of the cylinder may occur because the drain leaking from the valve body trickles downward. Therefore, the application of the present invention is of great significance. Description of reference symbols 1 steam valve 2 valve housings 11 valve disc 12 valve stem 13 Clutch 14 cylinders 14b Piston rod 15 yokes 15b base plate 15d opening 40 Cover 50 border 60 border 70 slot 80 drain pan 81 Process

Claims

[1] A steam valve (1) with: a valve housing (2), a valve plate (11) arranged within the valve housing (2), a cylinder (14) arranged on an underside of the valve housing (2) and having an upwardly extending piston rod (14b), and a valve stem which penetrates vertically through a lower portion of the valve housing (2) and whose one end is coupled to the piston rod (14b) via a coupling (13) and whose other end is coupled to the valve plate (11), characterized by that the steam valve (1) has: a cover (40) having a larger diameter than the piston rod (14b) and the coupling (13) and configured to separate the piston rod (14b) and the coupling (13) from each other by being arranged between the piston rod (14b) and the coupling (13), and a tubular skirt (50) depending from a peripheral portion of the cover (40) and surrounding a periphery of a head portion of the piston rod (14b), wherein the cylinder (14) is supported by the valve housing (2) via a yoke (15), a base plate (15b) of the yoke (15), to which the cylinder (14) is attached, has an opening (15d) through which the piston rod (14b) extends, and a tubular skirt rising to surround a periphery of the opening (15d) on an inner side of the skirt (50) is disposed on an upper surface of the bottom plate (15b) of the yoke (15). [2] A steam valve (1) with: a valve housing (2), a valve plate (11) arranged within the valve housing (2), a cylinder (14) arranged on an underside of the valve housing (2) and having an upwardly extending piston rod (14b), and a valve stem which penetrates vertically through a lower portion of the valve housing (2) and whose one end is coupled to the piston rod (14b) via a coupling (13) and whose other end is coupled to the valve plate (11), characterized by that the steam valve (1) has: a cover (40) having a larger diameter than the piston rod (14b) and the coupling (13) and configured to separate the piston rod (14b) and the coupling (13) from each other by being arranged between the piston rod (14b) and the coupling (13), and a tubular skirt (50) depending from a peripheral portion of the cover (40) and surrounding a periphery of a head portion of the piston rod (14b), wherein the cylinder (14) is supported by the valve housing (2) via a yoke (15), a base plate (15b) of the yoke (15), to which the cylinder (14) is attached, has an opening (15d) through which the piston rod (14b) extends, an annular slot (70) is formed in an upper surface of the bottom plate (15b) of the yoke (15) so as to surround a periphery of the opening (15d), and the slot (70) is opposite a lower end of the border (50). [3] The steam valve (1) according to claim 2, further comprising: a drain pan (80) arranged at a lower portion of the yoke (15), and a drain (81) configured to interconnect the slot (70) and the drain pan (80).

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