A gate valve for sodium medium with real-time leakage monitoring function

Abstract

The utility model relates to a sodium medium gate valve with real-time leakage monitoring function, belonging to the valve technical field of fourth generation sodium-cooled fast reactor. It includes that the first seal is formed between the valve body and the valve cover through the extruded metal seal ring, the metal diaphragm assembly and the graphite ring are installed in the valve cover and the valve body connection place from top to bottom in turn, the valve cover guard frame forms the second seal through the extruded metal diaphragm assembly and the graphite ring, the valve rod is wrapped in the bellows and forms the third seal below the packing box, and the packing group is arranged between the valve rod and the packing box and forms the fourth seal. The first sodium leakage monitoring assembly is arranged between the first seal and the second seal, and the second sodium leakage monitoring assembly is arranged between the third seal and the fourth seal, which solves the technical problems that the existing lip seal weld seam is prone to fatigue failure under the cold and hot cycle impact, leading to sodium liquid leakage, and the on-site maintenance is limited, and the sodium-cooled freeze seal is prone to oxide crystallization, leading to the valve rod seizure and jam, and the friction force is large, affecting the driving stability, and improves the operation safety and continuity.

Description

Technical Field

[0001] This invention relates to a gate valve for sodium media with real-time leakage monitoring function, belonging to the field of valve technology for fourth-generation sodium-cooled fast neutron reactors. Background Technology

[0002] In the fourth-generation sodium-cooled fast reactor, sodium-medium gate valves are used for the control of the transport of high-temperature liquid sodium. Due to the characteristics of liquid sodium, such as high temperature, strong chemical reactivity, and the tendency to react violently with water or air to produce sodium fire, extremely high requirements are placed on the valve's sealing reliability, leakage detection capability, and maintainability.

[0003] In existing technologies, the valve body and cover of large-diameter sodium-medium gate valves are typically connected by bolts to a middle flange, with a lip seal welded at the connection point before leaving the factory. This structure has significant shortcomings under actual operating conditions: Firstly, the pipeline system experiences frequent thermal cycling shocks during operation, causing creep deformation of the bolted middle flange connection, which in turn leads to fatigue failure of the lip seal weld. Once the weld fails, high-temperature sodium liquid will leak out, easily causing a sodium fire. Secondly, the number of times the lip seal weld can be cut for on-site maintenance is limited (usually only three cuts are allowed), making welding repair difficult and resulting in poor overall valve maintainability.

[0004] Furthermore, existing sodium-medium gate valves often employ a combination of sodium cryogenic seals and packing-assisted seals for their stem seals. Sodium cryogenic seals create a chamber between the stem and the valve cover, with heat sinks on the outside of the valve cover. When the temperature drops below 93°C, the molten sodium solidifies to form a solid seal. However, in actual operation, oxides present in the circuit (such as sodium oxide) react with elements like Fe and Ni to form a skin and crystallize in the low-temperature region. This crystallization can easily cause the stem to seize, resulting in valve jamming or even complete failure to operate. Simultaneously, the sodium cryogenic seal has high friction, requiring a larger drive unit, which may lead to insufficient valve natural frequency, affecting the stability and safety of the system.

[0005] In summary, existing sodium-medium gate valves have defects such as leakage risk, insufficient operational reliability, and poor maintainability in terms of valve body and cover sealing and valve stem sealing structure, making it difficult to meet the high safety and high reliability requirements of fourth-generation sodium-cooled fast reactors.

[0006] Therefore, there is an urgent need to develop a gate valve for sodium media with real-time leakage monitoring to solve the above-mentioned technical problems. Summary of the Invention

[0007] The purpose of this invention is to address the technical problem of sodium leakage and limited on-site maintenance caused by fatigue failure of existing lip seal welds under thermal cycling shock at the valve body and valve cover connection. It also addresses the technical problem of valve stem sealing being prone to valve stem seizure and jamming due to oxide crystallization caused by sodium freezing, as well as the impact of high friction on drive stability. A brief overview of this invention is provided below to offer a basic understanding of certain aspects of the invention. It should be understood that this overview is not an exhaustive summary of the invention. It is not intended to identify key or essential parts of the invention, nor is it intended to limit the scope of the invention.

[0008] The technical solution of the present invention:

[0009] A gate valve for sodium media with real-time leakage monitoring function includes a valve body, a valve seat, a valve cover, a valve stem, a gate, a retainer, a support, a stuffing box, a valve cover protector, a first seal, a second seal, a third seal, and a fourth seal. A valve cover is installed on the top of the valve body, and a stuffing box is installed on the top of the valve cover via a support. The valve cover protector is fitted onto the outside of the support and installed on the top of the valve cover. The lower part of the valve stem passes through the stuffing box support and the valve cover in sequence, and then extends into the valve body to connect with the gate. The gate is installed inside the valve body via a retainer. A valve seat is installed inside the valve body directly below the gate.

[0010] The valve body and the valve cover form a first seal by extruding a metal sealing ring;

[0011] A metal diaphragm assembly and a graphite ring are sequentially installed from top to bottom at the connection between the valve cover and the valve body. The valve cover guard forms a second seal by compressing the metal diaphragm assembly and the graphite ring.

[0012] The portion of the valve stem located below the stuffing box is encased within the bellows to form a third seal;

[0013] A packing assembly is provided between the valve stem and the stuffing box to form a fourth seal;

[0014] A first sodium leakage monitoring component is provided between the first seal and the second seal to detect whether the first seal is leaking in real time.

[0015] A second sodium leakage monitoring component is installed between the third and fourth seals to monitor whether the bellows is leaking in real time.

[0016] Preferably, a drainage pipe is provided between the first seal and the second seal, so that when the leakage of the first seal is small, the leaked sodium liquid flows to the sodium pool through the drainage pipe.

[0017] Preferably, a packing assembly is filled between the stuffing box and the valve stem, and a packing gland and a packing pressure plate are provided on the top of the packing assembly. The packing pressure plate is fixedly connected to the stuffing box by packing bolts.

[0018] Preferably, the bottom of the bellows is fixedly and sealed to the valve stem, and the top of the bellows is fixedly and sealed to the stuffing box.

[0019] Preferably, a sodium discharge connector is installed at the bottom of the valve body, and a sodium discharge plug is installed on the sodium discharge connector through a transition connector.

[0020] Preferably, the valve cover guard is provided with a valve cover stud on the top, which fastens the valve cover guard to the valve body. A disc spring is provided between the valve cover guard and the metal diaphragm assembly. A lifting bolt is installed on the valve cover guard, and a disc spring assembly is fitted on the lifting bolt and fastened with a nut. The lifting bolt cooperates with the valve cover. When the nut is tightened, the valve cover is lifted by the lifting bolt to generate a compressive force on the metal sealing ring.

[0021] Preferably, the valve stem nut mounting seat is fixedly installed on the top of the valve cover frame by a mounting bracket, and the valve stem nut is installed in the valve stem nut mounting seat by a bearing and a buffer disc spring assembly, with the top of the valve stem engaging with the valve stem nut.

[0022] The present invention has the following beneficial effects:

[0023] 1. The valve body and valve cover of this invention employ a metal sealing ring compression to form a first seal, which, together with a metal diaphragm assembly and a graphite ring, forms a second seal, creating a double-seal protection structure. This effectively overcomes the hidden danger of high-temperature sodium liquid leaking outward from the valve pressure boundary, preventing sodium fire accidents. A sodium leakage monitoring component and a drainage pipe are installed between the first and second seals. This allows for real-time detection of whether the first seal is leaking and outputting a signal, and also enables the drainage of sodium liquid to the sodium pool when the leakage is small, ensuring continued valve operation and improving operational safety and continuity.

[0024] 2. The first and second seals of this invention support online maintenance and testing. The integrity of the seal can be checked by inputting test medium into the valve body cavity and the sealing cavity, and the valve has online testability. On-site disassembly and maintenance are convenient, with no limit on the number of maintenance times. Each time, only the metal sealing ring and graphite ring need to be replaced, which significantly improves the maintainability of the valve.

[0025] 3. In this invention, a bellows is used as the third seal between the valve stem and the valve cover, and a packing assembly is used as the fourth seal, replacing the traditional combination structure of sodium cryogenic seal and packing seal. The bellows seal avoids the valve stem seizing problem caused by oxide crystallization in sodium cryogenic seal, has low friction, allows for more flexible selection of drive device, meets the requirements for natural frequency, and significantly improves the reliability of valve opening and closing action;

[0026] 4. A sodium leakage monitoring component is also provided between the third seal and the fourth seal of the present invention, which can monitor in real time whether the bellows is damaged and leaking, further enhancing the safety monitoring capability of the valve stem sealing part and ensuring that the packing seal can still prevent sodium liquid from leaking when the bellows fails.

[0027] 5. The sodium discharge assembly at the bottom of the valve body of the present invention adopts a three-section structure of sodium discharge connector, transition connector and sodium discharge plug. It is sealed by threaded fastening and double sealing by lip welding. The transition connector and sodium discharge plug are replaceable, supporting multiple maintenance operations, effectively extending the number of times the valve can be maintained, and significantly improving the overall economy and maintenance convenience. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of a gate valve for sodium media with real-time leakage monitoring function.

[0029] Figure 2 yes Figure 1 Enlarged view of point A;

[0030] Figure 3 yes Figure 1 Enlarged view of point B;

[0031] Figure 4 yes Figure 1 Enlarged view of point C;

[0032] Figure 5 yes Figure 1 Enlarged view of point D.

[0033] In the diagram: 1-Valve body, 2-Valve seat, 3-Valve cover, 4-Valve stem, 5-Gate, 6-Retainer, 7-Bracket, 8-Stuffing gland, 9-Valve cover guard, 10-Metal sealing ring, 11-Metal diaphragm assembly, 12-Graphite ring, 13-Bellboard, 14-Stuffing assembly, 15-First sodium leakage monitoring assembly, 16-Drainage pipe, 17-Second sodium leakage monitoring assembly, 18-Stuffing gland, 19-Stuffing pressure plate, 20-Stuffing bolt, 21-Sodium drain connector, 22-Transition connector, 23-Sodium drain plug, 24-Valve cover stud, 25-Disc spring, 26-Pull bolt, 27-Disc spring assembly, 28-Nut, 29-Valve stem nut mounting seat, 30-Mounting bracket, 31-Valve stem nut, 32-Bearing, 33-Buffer disc spring assembly. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0035] The connections mentioned in this invention are divided into fixed connections and detachable connections. Fixed connections (i.e., non-detachable connections) include, but are not limited to, conventional fixed connection methods such as folded connections, riveted connections, adhesive connections, and welded connections. Detachable connections include, but are not limited to, conventional disassembly methods such as threaded connections, snap-fit ​​connections, pin connections, and hinged connections. When a specific connection method is not explicitly defined, it is assumed that at least one existing connection method can always be found to achieve the function, and those skilled in the art can choose according to their needs. For example, a welded connection can be chosen for fixed connections, and a hinged connection can be chosen for detachable connections.

[0036] Example 1: Combination Figures 1-5 This embodiment describes a gate valve for sodium media with real-time leakage monitoring function. This embodiment provides a gate valve for sodium media with real-time leakage monitoring function, which is suitable for the piping system of fourth-generation sodium-cooled fast neutron reactors, and is especially suitable for nuclear power pipelines with a specification of DN80 and above.

[0037] The gate valve for sodium media includes a valve body 1, a valve seat 2, a valve cover 3, a valve stem 4, a gate 5, a retainer 6, a support 7, a stuffing box 8, a valve cover guard 9, and a first seal, a second seal, a third seal, and a fourth seal formed by the cooperation of the above components.

[0038] A valve cover 3 is mounted on the top of the valve body 1, and a stuffing box 8 is fixedly mounted on the top of the valve cover 3 via a bracket 7. A valve cover guard 9 is fitted onto the outside of the bracket 7, and its bottom rests on and is fixed to the top shoulder of the valve cover 3. The lower part of the valve stem 4 passes through the central through hole of the stuffing box 8, the bracket 7, and the valve cover 3 in sequence, and then extends into the inner cavity of the valve body 1, where it is fixedly connected to the gate 5. The gate 5 is positioned and mounted in the internal flow channel of the valve body 1 via a retainer 6, and a valve seat 2 that seals with the gate 5 is mounted on the inner wall of the valve body 1 directly below the gate 5.

[0039] A metal sealing ring 10 is provided at the flange connection between the valve body 1 and the valve cover 3. Several valve cover studs 24 are installed on the top of the valve cover bracket 9. The lower ends of the valve cover studs 24 pass through the valve cover bracket 9 and are threadedly fastened to the valve body 1, thus reliably fixing the valve cover bracket 9 to the valve body 1. Simultaneously, a lifting bolt 26 is also installed on the valve cover bracket 9, with its lower end threadedly connected to the valve cover 3. A disc spring assembly 27 and a nut 28 are sequentially fitted onto the rod segment of the lifting bolt 26 located above the valve cover bracket 9. During assembly, tightening the nut 28 compresses the disc spring assembly 27, generating an upward pulling force on the lifting bolt 26, pulling the valve cover 3 upward. During the upward movement of the valve cover 3, the metal sealing ring 10 is pressed between the lower end face of the valve cover 3, the upper end face of the valve body 1, and the lower end face of the four-ring seal located between them, thus forming an elastic first sealing structure. The four open rings serve to limit and support the metal sealing ring 10 at this point.

[0040] To prevent direct leakage of high-temperature sodium liquid after the first seal fails, a second seal is provided at the connection between the valve cover 3 and the valve body 1. Specifically, a disc spring 25, a metal diaphragm assembly 11, and a graphite ring 12 are installed sequentially from top to bottom between the annular stepped surface of the valve cover 3 and the corresponding inner end face of the valve cover guard 9. The valve cover guard 9 is pressed downward by the preload force of the valve cover stud 24. This pressing force is transmitted to the metal diaphragm assembly 11 through the disc spring 25, causing the metal diaphragm assembly 11 to fit tightly against the graphite ring 12. At the same time, the lower end face of the graphite ring 12 fits tightly against the corresponding sealing surfaces of the valve body 1 and the valve cover 3, thereby forming a reliable second seal. Here, the metal diaphragm assembly 11 and the graphite ring 12 form two independent sealing contact surfaces with the valve body 1 and the valve cover 3, respectively, together constituting the second sealing barrier between the valve body 1 and the valve cover 3.

[0041] Within the annular cavity between the first and second seals, a first sodium leakage monitoring component 15 and a drainage pipe 16 are installed. Specifically, a radially penetrating discharge hole is formed on the four-ring structure installed between the valve body 1 and the valve cover 3, and a sodium-containing cavity communicating with the discharge hole is formed at a corresponding position on the valve body 1. A connecting hole is drilled on the outer side of the sodium-containing cavity, which connects to the interface of the first sodium leakage monitoring component 15 on one hand and to the interface of the drainage pipe 16 on the other. When a small amount of leakage occurs in the first seal, the leaked high-temperature sodium liquid flows into the sodium-containing cavity through the discharge hole of the four-ring structure. If the leakage is small, the sodium liquid can be guided back to the system sodium pool through the drainage pipe 16, ensuring that the valve continues to operate without shutting down. At the same time, after the first sodium leakage monitoring component 15 comes into contact with the sodium liquid, its internal circuit is activated and an electrical signal is output to the control room, realizing a real-time alarm for leakage in the first seal.

[0042] A double-sealing structure consisting of a bellows 13 and a packing assembly 14 is used between the valve stem 4 and the stuffing box 8. The bellows 13 is fitted onto the portion of the valve stem 4 below the stuffing box 8. The lower end of the bellows 13 is fixed to the valve stem 4 by welding to form a sealed connection, and the upper end of the bellows 13 is also fixed to the lower end of the stuffing box 8 by welding to form a sealed connection, thus forming a completely closed third seal. The bellows 13 expands and contracts with the movement of the valve stem 4, completely isolating the high-temperature sodium liquid from the outside environment.

[0043] Inside the stuffing box 8, a packing assembly 14 is filled between the valve stem 4 and the inner wall of the stuffing box 8, forming a fourth seal. A packing gland 18 and a packing pressure plate 19 are located on top of the packing assembly 14. The packing pressure plate 19 is fastened to the top flange of the stuffing box 8 by multiple packing bolts 20. By tightening the packing bolts 20, the packing gland 18 presses the packing assembly 14 downwards, causing the packing assembly 14 to expand radially. Its inner wall then fits tightly against the valve stem 4, forming an auxiliary packing seal.

[0044] A second sodium leakage monitoring component 17 is installed in the cavity between the third and fourth seals. This component is installed at the side wall opening of the stuffing box 8 and communicates with the cavity. When sodium leaks due to fatigue or accidental damage to the bellows 13, sodium enters the cavity and triggers the second sodium leakage monitoring component 17, which outputs an electrical alarm signal to remind maintenance personnel to handle the situation promptly. At this time, the packing assembly 14 of the fourth seal can temporarily prevent further leakage of sodium, buying time for the safe shutdown and maintenance of the valve.

[0045] A sodium drain port is provided at the bottom of the valve body 1 for draining residual sodium liquid in the valve chamber after shutdown. A sodium drain assembly is installed at the sodium drain port, which includes a sodium drain connector 21, a transition connector 22, and a sodium drain plug 23. The sodium drain connector 21 is fixed to the bottom of the valve body 1 by threaded connection and fillet weld. The lower end of the sodium drain connector 21 is fixed to the upper end of the transition connector 22 by threaded connection, and a lip weld is applied to the outer edge of the connection to form a first seal; the lower end of the transition connector 22 is also fixed to the upper end of the sodium drain plug 23 by threaded connection, and a lip weld is applied to the outer edge to form a second seal. With this two-stage threaded and lip weld structure, when multiple maintenance of the sodium drain port is required, only the lip weld at the corresponding position needs to be cut off, and a new transition connector 22 or sodium drain plug 23 needs to be replaced. The single-lip weld sealing surface can be cut and repaired three times online. By replacing the transition joint 22 and the sodium discharge plug 23 in sequence, the total number of repairs for the entire sodium discharge assembly can reach nine times, which greatly improves the maintainability and economy of the valve.

[0046] The drive mechanism of the valve stem 4 is located at the top of the valve. The valve stem nut mounting seat 29 is fixedly connected to the top of the valve cover guard 9 via the mounting bracket 30. A bearing 32 and a buffer disc spring assembly 33 are assembled in the inner cavity of the valve stem nut mounting seat 29. The valve stem nut 31 is rotatably supported on the bearing 32, and its axial direction is elastically buffered by the buffer disc spring assembly 33. A trapezoidal thread section is machined on the top of the valve stem 4, which mates with the internal thread of the valve stem nut 31. When an external drive device rotates the valve stem nut 31, the valve stem 4 rises and falls under the action of the thread, driving the gate 5 to open and close the valve. The buffer disc spring assembly 33 absorbs impact loads during the terminal stroke of the valve opening and closing, reducing mechanical vibration and impact damage to the sealing surface.

[0047] The first and second seals described in this invention possess excellent online testability. During routine maintenance or inspection of the valve, a test medium can be injected into the central cavity of the valve body 1. By observing whether the first sodium leakage monitoring component 15 outputs a signal, the integrity of the first seal can be determined. Similarly, injecting a test medium into the sealing cavity between the first and second seals can verify the integrity of the second seal. If a seal failure is found, only the valve cover bracket 9 and the lifting bolt 26 need to be removed to replace the metal sealing ring 10, graphite ring 12, and metal diaphragm assembly 11. The maintenance process is simple and quick, and the number of maintenance attempts is unlimited, effectively overcoming the limitations of traditional lip seal welding maintenance.

[0048] In summary, the sodium-medium gate valve provided in this embodiment, through the installation of multiple redundant seals, multiple real-time leakage monitoring devices, controllable drainage channels, and a highly maintainable sodium discharge structure, comprehensively improves the safety, reliability, operational continuity, and maintenance economy of valves in the sodium-cooled fast reactor piping system. It can effectively prevent sodium fire accidents and ensure the safe and stable operation of nuclear power plants.

[0049] It should be noted that in the above embodiments, as long as the technical solutions are not contradictory, they can be permuted and combined. Those skilled in the art can exhaust all possibilities based on the mathematical knowledge of permutation and combination. Therefore, the present invention will not describe the technical solutions after permutation and combination one by one, but it should be understood that the technical solutions after permutation and combination have been disclosed by the present invention.

[0050] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A gate valve for sodium media with real-time leakage monitoring function, characterized in that: The valve body (1), valve seat (2), valve cover (3), valve stem (4), gate (5), retainer (6), bracket (7), stuffing box (8), valve cover guard (9), first seal, second seal, third seal and fourth seal are included. The valve cover (3) is installed on the top of the valve body (1). The stuffing box (8) is installed on the top of the valve cover (3) through the bracket (7). The valve cover guard (9) is fitted on the outside of the bracket (7) and installed on the top of the valve cover (3). The lower part of the valve stem (4) passes through the stuffing box (8), bracket (7) and valve cover (3) in sequence, and then enters the valve body (1) to connect with the gate (5). The gate (5) is installed inside the valve body (1) through the retainer (6). The valve seat (2) is installed in the valve body (1) directly below the gate (5). A first seal is formed between the valve body (1) and the valve cover (3) by extruding a metal sealing ring (10); The valve cover (3) and the valve body (1) are connected by a metal diaphragm assembly (11) and a graphite ring (12) installed sequentially from top to bottom. The valve cover guard (9) forms a second seal by pressing the metal diaphragm assembly (11) and the graphite ring (12). The valve stem (4) located below the stuffing box (8) is wrapped and fitted inside the bellows (13) to form a third seal; A packing assembly (14) is provided between the valve stem (4) and the stuffing box (8) to form a fourth seal; A first sodium leakage monitoring component (15) is provided between the first seal and the second seal to detect whether the first seal leaks in real time. A second sodium leakage monitoring component (17) is provided between the third seal and the fourth seal to monitor whether the bellows (13) is leaking in real time.

2. A gate valve for sodium media with real-time leakage monitoring function according to claim 1, characterized in that: A drain pipe (16) is provided between the first seal and the second seal. When the leakage of the first seal is small, the leaked sodium liquid flows to the sodium pool through the drain pipe (16).

3. A gate valve for sodium media with real-time leakage monitoring function according to claim 1, characterized in that: The stuffing box (8) and valve stem (4) are filled with a packing assembly (14). The top of the packing assembly (14) is provided with a packing gland (18) and a packing pressure plate (19). The packing pressure plate (19) is fixedly connected to the stuffing box (8) by a packing bolt (20).

4. A gate valve for sodium media with real-time leakage monitoring function according to claim 1, characterized in that: The bottom of the bellows (13) is fixedly and sealed to the valve stem (4), and the top of the bellows (13) is fixedly and sealed to the stuffing box (8).

5. A gate valve for sodium media with real-time leakage monitoring function according to claim 1, characterized in that: The bottom of the valve body (1) is equipped with a sodium discharge connector (21), and the sodium discharge plug (23) is installed on the sodium discharge connector (21) through a transition connector (22).

6. A gate valve for sodium media with real-time leakage monitoring function according to claim 1, characterized in that: The valve cover guard (9) is provided with a valve cover stud (24) at the top. The valve cover stud (24) fastens the valve cover guard (9) to the valve body (1). A disc spring (25) is provided between the valve cover guard (9) and the metal diaphragm assembly (11). A lifting bolt (26) is installed on the valve cover guard (9). A disc spring assembly (27) is fitted on the lifting bolt (26) and fastened by a nut (28). The lifting bolt (26) cooperates with the valve cover (3). When the nut (28) is tightened, the valve cover (3) is lifted by the lifting bolt (26) to generate a compressive force on the metal sealing ring (10).

7. A gate valve for sodium media with real-time leakage monitoring function according to claim 1, characterized in that: The valve stem nut mounting seat (29) is fixedly installed on the top of the valve cover guard (9) by the mounting bracket (30). The valve stem nut (31) is installed in the valve stem nut mounting seat (29) by the bearing (32) and the buffer disc spring assembly (33). The top of the valve stem (4) is engaged with the valve stem nut (31).

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