Welded butterfly valve, valve unit for vacuum double piping, and method for manufacturing a welded butterfly valve

Abstract

To provide a welded butterfly valve that can be suitably used for transporting liquefied hydrogen while maintaining ease of maintenance and low costs. [Solution] A welded valve 10 connected to a pipe by welding, comprising a valve body 11 through which a low-temperature fluid passes, a valve element 13 provided inside the valve body 11 and opening and closing the flow path of the low-temperature fluid by the drive of a valve stem 12, and a maintenance cover 14 that can open and close to cover a maintenance hole 11a formed on the upper part of the valve body 11, wherein the valve body 11 has resistance to hydrogen embrittlement and an allowable tensile stress of 100 N / mm at -253°C. 2 It consists of the above-mentioned metallic materials.

Description

Technical Field

[0001] The present invention relates to a welded butterfly valve, a valve unit for a vacuum double pipe, and a method for manufacturing a welded butterfly valve.

Background Art

[0002] In order to transport cryogenic fluids such as liquefied hydrogen, a vacuum double pipe is known in which an inner pipe through which the cryogenic fluid passes is covered with an outer pipe, and a vacuum layer is formed between the inner pipe and the outer pipe. As valves used for vacuum double pipes, welded types and flange types are mainly known due to differences in connection structures. Recently, however, the need for welded types has been increasing in applications such as for ships. Also, as a type of valve, butterfly valves are usually used in consideration of the cryogenic environment.

[0003] Since a welded butterfly valve for a vacuum double pipe is welded so that the pipe cannot be removed, for example, as disclosed in Patent Document 1, it is common to form a maintenance hole for maintenance in the valve box. A valve box having such a maintenance hole is suitable for manufacturing by casting because its shape tends to be complex, but the material used for casting is likely to cause hydrogen embrittlement, so it has been difficult to use the manufactured valve for transporting liquefied hydrogen.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Therefore, an object of the present invention is to provide a welded butterfly valve, a valve unit for a vacuum double pipe, and a method for manufacturing a welded butterfly valve that can be suitably used for transporting liquefied hydrogen while maintaining the workability and cost reduction of maintenance. [Means for solving the problem]

[0006] The object of the present invention is a welded butterfly valve connected to a pipe by welding, comprising: a valve body through which a low-temperature fluid passes; a valve element provided within the valve body and opening and closing the flow path of the low-temperature fluid by the drive of a valve stem; and a maintenance cover that can open and close a maintenance hole formed on the upper part of the valve body, wherein the valve body is resistant to hydrogen embrittlement and has an allowable tensile stress of 100 N / mm at -253°C. 2 This is achieved by a welded butterfly valve made of the above metal material. The valve body is preferably made of SUS304L or SUS316L. This welded butterfly valve is suitable for use in vacuum double-walled piping where a vacuum layer is formed between an inner tube through which a low-temperature fluid flows and an outer tube covering the inner tube.

[0007] Furthermore, the above-mentioned object of the present invention is achieved by a vacuum double-pipe valve unit comprising the above-mentioned welded butterfly valve, a housing covering the welded butterfly valve, and a connecting pipe connected to the downstream and upstream sides of the welded butterfly valve, wherein the housing has a first opening through which the connecting pipe is inserted and a second opening for opening and closing the maintenance cover from the outside, the second opening is covered so as to be openable and closable by an operating cover, the connecting pipe has a first flange portion on its outer circumference, and the inner pipe can be welded to the end that protrudes to the outside through the first opening, and the housing is sealed by welding the first flange portion to the periphery of the first opening, thereby maintaining a vacuum state inside.

[0008] Furthermore, the above-mentioned object of the present invention is achieved by a method for manufacturing the above-described welded butterfly valve, comprising: a first step of cutting a cylindrical material made of metal into a rectangular parallelepiped to form a block body that matches the dimensions of the valve body; and a second step of cutting the block body after the first step to form the valve body. Preferably, the first step includes a step of forming a through hole that will become the flow path of the valve body after the formation of the block body. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a welded butterfly valve, a valve unit for vacuum double piping, and a method for manufacturing a welded butterfly valve that can be suitably used for transporting liquefied hydrogen while maintaining ease of maintenance and low cost. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic cross-sectional view of a valve unit for vacuum double piping equipped with a welded butterfly valve according to one embodiment of the present invention. [Figure 2] Figure 1 is a side view of a valve unit for vacuum double piping. [Figure 3] This is a process diagram illustrating an example of a manufacturing method for the main part of a welded butterfly valve shown in Figure 1. [Figure 4] This is a process diagram illustrating another example of a manufacturing method for the main part of the welded butterfly valve shown in Figure 1. [Figure 5] Figure 1 is an exploded view of a valve unit for vacuum double piping. [Figure 6] Figure 1 is a process diagram illustrating the connection method for the valve unit for vacuum double piping. [Figure 7] This is a side view of a valve unit for vacuum double piping according to another embodiment of the present invention. [Figure 8] This is a side view of a valve unit for vacuum double piping according to yet another embodiment of the present invention. [Modes for carrying out the invention]

[0011] Hereinafter, one embodiment of the present invention will be described with reference to the attached drawings. Figure 1 is a schematic cross-sectional view of a vacuum double-walled piping valve unit equipped with a welded butterfly valve according to one embodiment of the present invention, and Figure 2 is a side view of the vacuum double-walled piping valve unit shown in Figure 1, viewed in the direction of arrow A. The vacuum double-walled piping valve unit (hereinafter simply referred to as "valve unit") 1 shown in Figures 1 and 2 comprises a welded butterfly valve (hereinafter simply referred to as "welded valve") 10, a housing 20 covering the welded valve 10, and connecting pipes 2 and 3 connected to the downstream and upstream sides of the welded valve 10. The application of the welded valve 10 is not particularly limited, but it can be suitably used for ships transporting liquefied hydrogen. However, the application of the welded valve 10 is not limited to the transport of liquefied hydrogen, and it can also be used to open and close the flow paths of other cryogenic fluids such as liquefied ammonia, liquefied helium, liquefied nitrogen, and liquefied oxygen.

[0012] The welded valve 10 is a welded butterfly valve used in a vacuum double piping system described later. It comprises a cylindrical valve body 11 through which a low-temperature fluid passes, a valve element 13 provided inside the valve body 11 and driven by a valve stem 12 to open and close the flow path of the low-temperature fluid, and a maintenance cover 14 that can open and close a rectangular maintenance hole 11a formed on the upper part of the valve body 11. The valve stem 12 is rotatably inserted into a cylindrical protective cylinder 15 that protrudes upward from the valve body 11, which is arranged so that the flow path is horizontal. The maintenance cover 14 is a rectangular flat plate-shaped member and is fastened to the periphery of the maintenance hole 11a by a plurality of fasteners 18 such as bolts arranged along its periphery, thereby covering the maintenance hole 11a in an openable and closable manner.

[0013] The valve body 11, valve stem 12, valve element 13, and maintenance cover 14 are made of a material that has resistance to hydrogen embrittlement and sufficient strength, even in the cryogenic environment of transporting liquefied hydrogen. Specifically, the allowable tensile stress at -253°C, the boiling point of liquefied hydrogen, is 100 N / mm². 2The above metal materials are used. The allowable tensile stress of the material is shown, for example, in the Exemplary Criteria Collection of the Specific Equipment Inspection Rules of the High Pressure Gas Safety Association, Incorporated Administrative Agency (6th Revised Edition). As specific materials for the valve box 11 and the like, SUS304, SUS304L, SUS316, and SUS316L are preferable, and among these, SUS304L or SUS316L can be particularly preferably used. SUS304L includes SUSF304L, and SUS316L includes SUSF316L.

[0014] The communication pipes 2 and 3 are provided so as to horizontally extend from both the left and right sides of the valve box 11 shown in FIG. 1. The base end portions of the communication pipes 2 and 3 are welded to the valve box 11 so as to communicate with the inside of the valve box 11. Ring-shaped first flange portions 2a and 3a are fixed by being welded to the entire circumference at the welded portions W1 and W2, respectively, near the center of the outer peripheral surfaces of the communication pipes 2 and 3. The communication pipes 2 and 3 do not necessarily have to be separate members from the valve box 11, and the valve box 11 and the communication pipes 2 and 3 may be integrally formed by machining or the like.

[0015] The housing 20 is formed in a rectangular parallelepiped shape, and four side plates 23, 24, 25, and 26 are arranged and welded between the top plate 21 and the bottom plate 22. A vacuum evacuation line 27 and a vacuum release line 28 each provided with an on-off valve are connected to the housing 20, and the inside of the housing 20 can be evacuated to a vacuum state using the vacuum evacuation line 27, and the vacuum state of the housing 20 can be released using the vacuum release line 28.

[0016] First openings 23a and 24a through which the communication pipes 2 and 3 are inserted with a gap are formed in the side plates 23 and 24 facing the downstream side and the upstream side of the valve box 11, respectively. The first flange portions 2a and 3a provided on the communication pipes 2 and 3 are in contact with the inner surfaces of the side plates 23 and 24, respectively, and are welded along the opening edges of the first openings 23a and 24a at the welded portions W4 and W5, so that the gaps between the communication pipes 2 and 3 and the first openings 23a and 24 are sealed by the first flange portions 2a and 3a.

[0017] On the outer surfaces of the side plates 23 and 24, there are provided ring-shaped coupling portions 23b and 24b that are used when connecting a cover for connecting a vacuum double pipe, which will be described later. A plurality of screw holes 23c and 24c for attachment are formed in the coupling portions 23b and 24b.

[0018] On the top plate 21, there are formed a second opening 21a for opening and closing the maintenance cover 14 of the welded valve 10 from the outside of the housing 20, and a third opening 21b through which the protective cylinder 15 of the welded valve 10 is inserted with a gap. The second opening 21a is covered in an openable and closable manner by an operation cover 21d via a packing 21c. The operation cover 21d is detachably attached to the top plate 21 by a fastening tool (not shown) such as a bolt. The third opening 21b is covered from the outside of the top plate 21 by a ring-shaped second flange portion 15a that is welded to the protective cylinder 15 in a full circumferential weld at the weld portion W3. The second flange portion 15a is welded along the outer circumference at the weld portion W6 and fixed to the top plate 21.

[0019] The welded valve 10 is manufactured by forging using the above materials. In particular, for the valve box 11, since the shape is likely to become complicated by providing a maintenance hole 11a, it can be manufactured, for example, by the following manufacturing method.

[0020] FIG. 3 is a process diagram for explaining an example of a manufacturing method of the valve box 11. In (a) to (h), the left side is a side view and the right side is a front view. First, a cylindrical material C made of a metal material shown in FIG. 3(a) is prepared. As shown in FIG. 3(b), a through hole H that serves as a flow path of the valve box 11 is formed in the cylindrical material C. The through hole H shown in FIG. 3(b) is formed at a position where the center is shifted downward from the center of the cylindrical material C, but the center of the through hole H may be made to coincide with the center of the cylindrical material C. After that, as shown in FIGS. 3(c) and (d), a first step of cutting the cylindrical material C into a rectangular parallelepiped shape to form a block body B is performed. The block body B is formed in accordance with the dimensions of the valve box 11, and each dimension of the three orthogonal sides of the block body B substantially coincides with the width, length, and height of the valve box 11, respectively.

[0021] Next, as shown in Figures 3(e) and (f), the portions of the valve body 11 corresponding to the valve stem and maintenance hole are formed by machining. Then, as shown in Figure 3(g), a maintenance hole 11a is formed, and further, as shown in Figure 3(h), annular portions 11b and 11c for welding the connecting pipe are formed. Thus, the second step of forming the valve body 11 by machining the block body B is performed.

[0022] When forming a maintenance hole 11a in the valve body 11, the shape of the area surrounding the maintenance hole 11a tends to become complex. However, according to the above-described method for manufacturing the valve body 11, the material is sufficiently lightened by forming the through hole H and block body B, and then the cutting process for forming the maintenance hole is performed, thus improving the workability of the forging process. In particular, this manufacturing method is effective when the valve body 11 is large and heavy when used in ships.

[0023] In the above-described method for manufacturing the valve body 11, in the first step, a through hole H is formed in the cylindrical material C, and then the block body B is formed. However, as shown in Figures 4(a) to (c), in the first step, the block body B may be formed without forming a through hole in the cylindrical material C, and then the through hole H may be formed as shown in Figure 4(e). In the second step, cutting for forming a maintenance hole may be performed as shown in Figure 4(f). By forming the through hole H in the lighter block body B in this way, the through hole H can be easily and accurately provided.

[0024] The valve unit 1 of this embodiment can be easily and inexpensively manufactured by assembling and covering a welded valve 10 to which connecting pipes 2 and 3 are attached with a housing 20. The procedure for assembling the housing 20 is not particularly limited, but can be done, for example, by the following method.

[0025] Specifically, as shown in Figure 5, first, the first flange portions 2a and 3a are welded to the connecting pipes 2 and 3 connected to the valve body 11, and the second flange portion 15a is welded to the protective cylinder 15. The welding of the second flange portion 15a is performed with the protective cylinder 15 already inserted through the third opening 21b of the top plate 21.

[0026] Next, with the welded valve 10 positioned above the bottom plate 22, the top plate 21 is moved in the direction of the arrow until it contacts the second flange portion 15a, and the second flange portion 15a is welded to the top plate 21.

[0027] Then, the side plates 23 and 24 are moved in the direction of the arrows until they come into contact with the first flange portions 2a and 3a, respectively. After inserting the connecting pipes 2 and 3 into the first openings 23a and 24a, the side plates 23 and 24 are welded to the first flange portions 2a and 3a, as well as to the top plate 21 and bottom plate 22.

[0028] Finally, the remaining two side panels 25 and 26 (see Figure 2) are welded to the top panel 21, bottom panel 22, and side panels 23 and 24 to obtain a sealed enclosure 20.

[0029] Next, with reference to Figure 6, a method for connecting the valve unit 1 of this embodiment to a vacuum double-walled piping will be described. As shown in Figure 6, the vacuum double-walled piping 30 has an inner tube 31 through which a low-temperature fluid flows and an outer tube 32 covering the inner tube 31 arranged concentrically, and a vacuum layer 33 is formed between the inner tube 31 and the outer tube 32. The tip of the inner tube 31 protrudes from the tip of the closed outer tube 32 and is exposed to the outside. The outer surface of the outer tube 32 is provided with a ring-shaped coupling portion 32a for connecting a connecting cover 40, which will be described later. The vacuum layer 33 is evacuated by a vacuum pump (not shown) to vacuum-insulate the inner tube 31.

[0030] The tip of the vacuum double-walled pipe 30 can be covered with a rectangular tubular connecting cover 40 that has openings at both ends. The peripheral edges of the openings at both ends of the connecting cover 40 are provided with ring-shaped flange portions 40a and 40b. One flange portion 40a is connected to the coupling portions 23b and 24b of the valve unit 1 by fasteners such as bolts (not shown), and the other flange portion 40b is connected to the coupling portion 32a of the outer pipe 32. This allows the inside of the connecting cover 40 to be sealed, and the inside can be made into a vacuum state by performing vacuum evacuation with a vacuum pump (not shown).

[0031] To connect the valve unit 1 to the vacuum double piping 30, first, as shown in Figure 6(a), the tip of the outer pipe 32 is inserted into the connecting cover 40, and the inner pipe 31 of the valve unit 1 is brought close to one of the connecting pipes 3 as indicated by the arrow, and the ends of the connecting pipe 3 and the inner pipe 31 are welded together. In this way, the connection process of connecting the connecting pipe 3 to the inner pipe 31 is performed.

[0032] Next, as shown in Figure 6(b), the connecting cover 40 is moved toward the valve unit 1 as indicated by the arrow. If the connecting cover 40 is large, it may be moved on a trolley (not shown). After this, the flange portions 40a and 40b at both ends of the connecting cover 40 are connected to the respective joint portions 24b and 32a of the housing 20 and outer pipe 32, thereby sealing the inside of the connecting cover 40 as shown in Figure 6(c). In this way, a covering process is performed in which the parts of the connecting pipe 3 and inner pipe 31 that are exposed to the outside after connection are covered with the connecting cover 40.

[0033] The vacuum double piping 30 can also be connected to the other connecting pipe 4 of the valve unit 1 using the same procedure as described above. After connecting the vacuum double piping 30 to the valve unit 1, as shown in Figure 6(d), the housing 20 and the connecting cover 40, and the connecting cover 40 and the vacuum layer 33 are connected by connection lines 34 and 35, respectively, thereby maintaining a vacuum state inside the housing 20 and the connecting cover 40 together with the vacuum layer 33.

[0034] Although one embodiment of the present invention has been described in detail above, the specific aspects of the present invention are not limited to the above embodiment. For example, in this embodiment, the first flange portions 2a and 3a of the connecting pipes 2 and 3 are welded to the inner surface of the housing 20 to facilitate the assembly of the housing 20, but it is also possible to weld the first flange portions 2a and 3a to the outer surface of the housing 20.

[0035] Furthermore, in this embodiment, the second flange portion 15a of the protective cylinder 15 is welded to the outer surface of the housing 20, but it may also be welded to the inner surface of the housing 20, or even better, the protective cylinder 15 may be welded directly to the opening edge of the third opening 21b without providing the second flange portion 15a.

[0036] Furthermore, although the housing 20 is formed in the shape of a rectangular parallelepiped in this embodiment, the shape of the housing 20 is not particularly limited. For example, as shown in the side view in Figure 7, a housing 20 can be constructed with a lower part that is arc-shaped in side view by welding curved side plates 25 and 26 together at the welding joint W10 without providing a bottom plate. The shape of the joint 24b may be formed to match the opening shape of the connecting cover 40 (see Figure 6), and may be formed in the shape of a rectangular frame, for example, as shown in Figure 8. Note that in Figures 7 and 8, the same reference numerals are used for components that are the same as those in Figure 2, etc. [Explanation of Symbols]

[0037] 1. Valve unit for vacuum double-walled piping 2,3 Communication pipe 2a,3a First flange portion 10. Welded butterfly valve 11 Valve box 11a Maintenance Hole 12 Valve stem 13 Valve body 14. Maintenance cover 15 Protective tube 15a Second flange portion 20 cabinets 21a Second opening 21b Third opening 21d Operating Cover 23a, 24a First opening 23b,24b joint part 30 Vacuum double piping 31 Inner tube 32 Outer tube 32a Joint part 40 Connection cover 40a, 40b Flange section

Claims

1. A welded butterfly valve that is connected to a pipe by welding, The valve comprises a valve body through which a low-temperature fluid passes, a valve element provided within the valve body that opens and closes the flow path of the low-temperature fluid by the drive of a valve stem, and a maintenance cover that can open and close to cover a maintenance hole formed in the upper part of the valve body. The valve body has resistance to hydrogen embrittlement and an allowable tensile stress of 100 N / mm at -253°C. ２ A welded butterfly valve made of the above metal material.

2. The valve body is made of SUS304L or SUS316L, as described in claim 1, a welded butterfly valve.

3. A welded butterfly valve according to claim 1, used in a vacuum double-walled piping system in which a vacuum layer is formed between an inner tube through which a low-temperature fluid flows and an outer tube covering the inner tube.

4. A welded butterfly valve according to claim 3, A housing covering the aforementioned welded butterfly valve, The welded butterfly valve is equipped with connecting pipes connected to the downstream and upstream sides, The housing has a first opening through which the connecting pipe is inserted and a second opening for opening and closing the maintenance cover from the outside, and the second opening is covered by an operating cover so as to be openable and closable. The connecting pipe has a first flange portion on its outer circumference, and the inner pipe can be welded to the end that protrudes to the outside through the first opening, and the housing is sealed by welding the first flange portion to the periphery of the first opening, thereby maintaining a vacuum state inside, in a valve unit for vacuum double piping.

5. A method for manufacturing a welded butterfly valve as described in claim 1, The first step is to cut a cylindrical material made of metal into a rectangular parallelepiped shape to form a block body that matches the dimensions of the valve body, A method for manufacturing a welded butterfly valve, comprising the first step followed by a second step of machining the block body to form the valve casing.

6. The method for manufacturing a welded butterfly valve according to claim 5, further comprising the first step of forming a through hole that will become a flow path for the valve body after the formation of the block body.

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