Valve seat structure of an ultra-low temperature top-mounted fixed ball valve

Abstract

The application discloses a valve seat structure of an ultra-low temperature top-mounted fixed ball valve, which is installed in a valve body of the ball valve and used for forming sealing cooperation with a ball body arranged in the ball valve when the ball valve is closed; the valve seat structure comprises a valve seat body, an annular pre-tightening part and a spring assembly; a valve seat groove is formed in the valve body; the valve seat body is arranged in the valve seat groove in an axially slidable mode; the annular pre-tightening part is arranged on the outer periphery of the valve seat body; the inner end of the valve seat body is provided with an annular sealing flange extending outward; the spring assembly is arranged in the valve body and used for applying an axial spring force of the annular pre-tightening part to the annular sealing flange; and a pre-tightening force conversion structure is arranged between the annular sealing flange and the annular pre-tightening part, so that when the annular pre-tightening part shrinks due to temperature reduction, an axial force of the valve seat body is generated towards the ball body. The application is not only convenient to disassemble and assemble, but also stable in low-temperature sealing performance, and the reliability and maintenance convenience of the ball valve under the ultra-low temperature working condition are improved.

Description

Technical Field

[0001] This invention relates to the field of valve structure technology, and in particular to a valve seat structure for a cryogenic top-mounted fixed ball valve. Background Technology

[0002] Cryogenic top-entry fixed ball valves are widely used in cryogenic media transportation systems such as liquefied natural gas, cryogenic ethylene, liquid oxygen, and liquid nitrogen. Their core sealing component is the valve seat assembly. Currently, to enable online maintenance, traditional top-entry fixed ball valves in the industry generally design the valve seat with a nut adjusting the spring preload. This structure has the following drawbacks: 1. High manufacturing cost: The threaded regulating valve seat is difficult to process and requires extremely high machining accuracy of the valve body mounting surface. The regulating nut needs to cope with ultra-low temperature conditions and prevent the threads from seizing. It is generally made of copper, which increases production and maintenance costs. 2. Difficult to assemble and disassemble: The structure of adjusting the preload of the nut and spring requires a heavy adjustment torque and high adjustment accuracy. Special tooling is required for installation and disassembly. Repeated disassembly can easily lead to thread damage and seizing, making disassembly and assembly inconvenient. 3. Insufficient reliability of low-temperature sealing: In traditional valve seat spring preload mechanisms, uneven shrinkage of metal parts in low-temperature environments can easily lead to a decrease in preload force and a reduction in the fit of the sealing surface, resulting in leakage at the sealing surface. 4. Poor structural adaptability: The existing valve seat structure cannot achieve rapid radial positioning. The valve seat of large-diameter valves is prone to axial movement due to fluctuations in medium pressure, which affects the sealing stability.

[0003] Therefore, it is necessary to develop a new type of valve seat structure that is easy to assemble and disassemble, has stable low-temperature sealing performance, and is highly adaptable, in order to overcome the shortcomings of existing technologies. Summary of the Invention

[0004] The purpose of this invention is to provide a valve seat structure for a cryogenic top-mounted fixed ball valve. This invention not only facilitates online disassembly and assembly, but also ensures stable low-temperature sealing performance, thereby improving the reliability and ease of maintenance of the ball valve under cryogenic conditions.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a valve seat structure for a cryogenic top-mounted fixed ball valve, installed within the valve body of the ball valve, for forming a sealing fit with a ball located inside the ball valve when the ball valve is closed; comprising a valve seat body, an annular preload member, and a spring assembly; a valve seat groove is provided within the valve body, the valve seat body is axially slidably disposed within the valve seat groove, the annular preload member is disposed on the outer periphery of the valve seat body, the inner end of the valve seat body is provided with an annular sealing flange extending outward, the spring assembly is disposed within the valve body for applying an axial spring force toward the annular sealing flange to the annular preload member, and a preload force conversion structure is provided between the annular sealing flange and the annular preload member, so that when the annular preload member contracts due to temperature reduction, it generates an axial force toward the ball on the valve seat body.

[0006] By adopting the above technical solution, an axial spring force is applied to the annular preload component through the spring assembly, giving the valve seat body a basic preload towards the ball. Simultaneously, the shrinkage of the annular preload component under low-temperature conditions is utilized, and converted into an axial force pushing the valve seat body towards the ball through a preload force conversion structure. This forms a composite preload structure combining spring preload and low-temperature shrinkage compensation, effectively compensating for insufficient sealing preload caused by thermal shrinkage of components and changes in spring preload under low-temperature conditions. This ensures a stable fit between the valve seat body and the ball, improving the stability and reliability of the seal under ultra-low temperature conditions.

[0007] The present invention is further configured such that a first annular conical surface is provided on the side of the annular sealing flange near the annular preload member, and a second annular conical surface adapted to the first annular conical surface is provided on the annular preload member, and the first annular conical surface and the second annular conical surface cooperate to form the preload force conversion structure.

[0008] By adopting the above technical solution, the basic preload is provided by the spring assembly, and the radial contraction of the annular preload component at low temperature is converted into an axial force that pushes the valve seat body toward the ball by the cooperating first and second annular conical surfaces. This achieves automatic compensation of the sealing preload under low temperature conditions, keeps the valve seat and the ball in stable contact, and improves the stability and reliability of the cryogenic seal.

[0009] The present invention is further configured such that the annular pretensioner includes a plurality of arc-shaped connecting blocks arranged sequentially along the circumference, adjacent arc-shaped connecting blocks are hinged together, and two arc-shaped connecting blocks located at the first and last ends of the arrangement direction of the plurality of arc-shaped connecting blocks are detachably connected by bolts, so that the plurality of arc-shaped connecting blocks together enclose and form an annular structure.

[0010] By adopting the above technical solution, the annular pretensioner uses multiple arc-shaped connecting blocks that are sequentially hinged and connected end to end with bolts to form an annular structure, which allows it to be flexibly unfolded and enclosed, making it easy to install and disassemble in a limited space. In addition, there is a certain amount of movement between each arc-shaped connecting block, which helps the annular pretensioner adapt to low-temperature shrinkage deformation and ensures the stable transmission of pretensioning effect.

[0011] The present invention is further configured such that at least two of the multiple arc-shaped connecting blocks have an arc-shaped conical surface on the side facing the annular sealing flange, and each arc-shaped conical surface is arranged circumferentially at intervals or continuously to form the second annular conical surface.

[0012] By adopting the above technical solution, the arc-shaped conical surface can be flexibly set according to the number and size of the arc-shaped connecting blocks, which is convenient for processing and can be adapted to valve seat structures of different specifications.

[0013] The present invention is further configured such that the spring assembly includes a spring support ring and a plurality of preload springs. The spring support ring is sleeved on the outer periphery of the valve seat body and sandwiched between the annular preload member and the inner wall of the valve body. The end face of the spring support ring away from the annular preload member has a plurality of spring grooves arranged in a circumferential array, the number of which is equivalent to the number of preload springs. The preload springs are embedded in the corresponding spring grooves, and the outer ends of the preload springs abut against the inner wall of the valve body.

[0014] By adopting the above technical solution, the elastic force generated by multiple circumferentially distributed pre-tightening springs is evenly transmitted to the annular pre-tightening component through the spring support ring, so that the valve seat body can obtain a balanced and stable axial pre-tightening force.

[0015] The invention is further configured such that the inner circular surface of the valve seat groove is provided with an annular sealing groove, a bidirectional spring energy storage sealing ring is provided in the annular sealing groove, and the outer circular surface of the bidirectional spring energy storage sealing ring is in close contact with the inner circular surface of the annular sealing groove, and the inner circular surface of the bidirectional spring energy storage sealing ring is in close contact with the outer circular surface of the valve seat body. The spring support ring is also provided with a limiting flange that extends into the annular sealing groove to restrict the bidirectional spring energy storage sealing ring in the annular sealing groove.

[0016] By adopting the above technical solution, a reliable seal between the valve seat body and the valve body is achieved through a bidirectional spring energy storage sealing ring, which can adapt to the axial sliding of the valve seat body and low temperature conditions, thereby improving the sealing reliability.

[0017] The invention is further configured such that top blocks for pushing the valve seat body are respectively installed at the upper and lower ends of the ball, and when the top blocks rotate synchronously with the ball, they have a first position of being detached from the valve seat body and a second position of applying a force to the valve seat body in a direction away from the ball.

[0018] By adopting the above technical solution, top blocks that rotate synchronously with the ball are set at both ends of the ball. When the ball rotates to the second position, the valve seat body can be pushed away from the ball, realizing the active retraction of the valve seat body, so that the valve seat body and the ball can be reliably separated, reducing the friction between them, and providing space for the disassembly and assembly of the ball, thereby improving the convenience of valve maintenance.

[0019] The invention is further configured such that an annular mounting groove is provided at each of the upper and lower ends of the sphere, the top block is connected to the corresponding annular mounting groove by screws, and the top block is provided with an arc surface that fits against the inner circular surface of the annular mounting groove.

[0020] By adopting the above technical solution, the top block is accurately positioned through the cooperation between the annular mounting groove and the arc surface of the top block, and the top block is fixed to the ball with screws, so that the top block can rotate stably with the ball and transmit the pushing force, thereby improving the stability and reliability of the valve seat pushing process.

[0021] The invention is further configured such that an annular positioning groove is provided at the inner end of the valve seat body, and a valve seat sealing ring for contacting and sealing with the surface of the ball is embedded in the annular positioning groove. Multiple pressure stabilizing grooves extending axially are provided on the inner circular surface of the annular sealing groove, and an anti-loosening flange extending inward in a circumferential direction is provided on the outer circular surface of the annular positioning groove corresponding to its outer end. The anti-loosening flange forms a limiting cone surface for supporting the outer end of the valve seat sealing ring.

[0022] By adopting the above technical solution, the valve seat seal ring is embedded in the annular positioning groove, which facilitates disassembly and independent replacement, reducing maintenance costs. At the same time, the pressure stabilizing groove helps to balance the pressure inside and outside the valve seat seal ring during disassembly and assembly, making it easier to disassemble. In addition, the limiting cone surface formed by the anti-loosening flange supports and limits the valve seat seal ring, which can suppress the outer deformation caused by the ball acting on the valve seat seal ring, ensuring the structural stability and sealing reliability of the valve seat seal ring.

[0023] The present invention is further configured to include a valve seat ejection fixture, the valve seat ejection fixture including a fixture nut and an adjusting screw, at least one positioning hole is provided on the outer circumferential surface of the valve seat body, a positioning pin for inserting into the positioning hole is fixedly provided on the outer periphery of the fixture nut, the adjusting screw is threadedly engaged with the fixture nut, and the central axis extension direction of the adjusting screw is parallel to the central axis extension direction of the valve seat body, and a pad is sandwiched between the inner end of the adjusting screw and the inner wall of the valve body.

[0024] By adopting the above technical solution, the valve seat ejection fixture is quickly connected to the valve seat body by the positioning pin. By turning the adjusting screw, the reaction force between the screw and the valve body can be used to drive the valve seat body to move axially, so as to achieve smooth ejection of the valve seat body and reduce the difficulty of valve seat disassembly. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 for Figure 1 Enlarged structural diagram of section A in the middle; Figure 3 This is a schematic diagram of the structure of the annular preload of the present invention; Figure 4 This is a schematic diagram of the valve seat body of the present invention; Figure 5 This is a schematic diagram of the separation structure between the annular preload and the valve seat body of the present invention; Figure 6 This is a schematic diagram of the spherical structure with a top block of the present invention; Figure 7 This is a schematic diagram of the installation structure of the valve seat sealing ring of the present invention; Figure 8 This is a schematic diagram of the valve seat ejection tool of the present invention.

[0026] In the diagram: 1. Valve body; 2. Ball; 3. Valve seat body; 4. Annular preload component; 5. Spring assembly; 6. Valve seat groove; 7. Annular sealing flange; 8. First annular conical surface; 9. Second annular conical surface; 10. Arc-shaped connecting block; 11. Arc-shaped conical surface; 12. Spring support ring; 13. Preload spring; 14. Spring groove; 15. Annular sealing groove; 16. Bidirectional spring energy storage sealing ring; 17. Limiting flange; 18. Top block; 19. Annular mounting groove; 20. Arc surface; 21. Annular positioning groove; 22. Valve seat sealing ring; 23. Pressure stabilizing groove; 24. Anti-loosening flange; 25. Limiting conical surface; 26. Valve seat ejection fixture; 27. Fixture nut; 28. Adjusting screw; 29. ​​Positioning hole; 30. Positioning pin; 31. Pad. Detailed Implementation

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example: As attached Figures 1-8The diagram illustrates a valve seat structure for a cryogenic top-mounted fixed ball valve, installed within the valve body 1 of the ball valve. This structure forms a sealing fit with the ball 2 located inside the ball valve when the valve is closed. It includes a valve seat body 3, an annular preload member 4, and a spring assembly 5. The valve body 1 has a valve seat groove 6, and the valve seat body 3 is axially slidable within this groove. The annular preload member 4 is located on the outer periphery of the valve seat body 3. The inner end of the valve seat body 3 has an annular sealing flange 7 extending outwards. The spring assembly 5, located within the valve body 1, applies an axial spring force to the annular preload member 4 towards the annular sealing flange 7. A preload force conversion structure is provided between the annular sealing flange 7 and the annular preload member 4, so that when the annular preload member 4 contracts due to temperature decrease, it generates an axial force on the valve seat body 3 towards the ball 2. The axial spring force applied to the annular preload member 4 by the spring assembly 5 provides a basic preload effect to the valve seat body 3 towards the ball 2. Meanwhile, the shrinkage generated by the annular preload 4 in the low-temperature environment is utilized, and the preload force conversion structure converts it into an axial force that pushes the valve seat body 3 toward the ball 2, thereby forming a composite preload structure that combines spring preload and low-temperature shrinkage compensation. This can effectively compensate for the insufficient sealing preload caused by the thermal shrinkage of parts and the change of spring preload force under low-temperature conditions, so that the valve seat body 3 and the ball 2 can maintain a stable fit, and improve the stability and reliability of the seal under ultra-low temperature conditions.

[0029] As attached Figures 2-5 As shown, the annular sealing flange 7 has a first annular conical surface 8 on the side near the annular preload member 4, and the annular preload member 4 has a second annular conical surface 9 that matches the first annular conical surface 8. The first annular conical surface 8 and the second annular conical surface 9 cooperate to form the preload force conversion structure. The spring assembly 5 provides the basic preload force, and the cooperating first annular conical surface 8 and the second annular conical surface 9 convert the radial contraction of the annular preload member 4 at low temperature into an axial force that pushes the valve seat body 3 toward the ball 2, realizing automatic compensation of the sealing preload force under low temperature conditions, keeping the valve seat and the ball 2 in a stable fit, and improving the stability and reliability of the cryogenic seal.

[0030] As attached Figure 3As shown, the annular pretensioner 4 includes multiple arc-shaped connecting blocks 10 arranged sequentially along the circumference. Adjacent arc-shaped connecting blocks 10 are hinged together by through-pins. Two arc-shaped connecting blocks 10 located at the beginning and end of the arrangement direction of the multiple arc-shaped connecting blocks 10 are detachably connected by bolts, so that the multiple arc-shaped connecting blocks 10 together enclose a ring structure. The annular pretensioner 4 uses multiple arc-shaped connecting blocks 10 that are sequentially hinged and connected end to end by bolts to form a ring structure, which allows it to be flexibly unfolded and enclosed, facilitating installation and disassembly in a limited space. Furthermore, there is a certain amount of movement between each arc-shaped connecting block 10, which helps the annular pretensioner 4 adapt to low-temperature shrinkage deformation and ensures the stable transmission of the pretensioning effect.

[0031] As attached Figure 3 As shown, at least two of the multiple arc-shaped connecting blocks 10 have arc-shaped conical surfaces 11 on one side facing the annular sealing flange 7. These arc-shaped conical surfaces 11 are spaced apart or continuous circumferentially, forming the second annular conical surface 9. In this embodiment, five arc-shaped connecting blocks 10 are used, and each arc-shaped connecting block 10 has an arc-shaped conical surface 11. The arc-shaped conical surfaces 11 can be flexibly arranged according to the number and size of the arc-shaped connecting blocks 10, facilitating processing and adapting to different valve seat structures.

[0032] As attached Figure 2 As shown, the spring assembly 5 includes a spring support ring 12 and multiple preload springs 13. The spring support ring 12 is sleeved on the outer periphery of the valve seat body 3 and sandwiched between the annular preload member 4 and the inner wall of the valve body 1. On the end face of the spring support ring 12 away from the annular preload member 4, multiple spring grooves 14, corresponding in number to the number of preload springs 13, are arranged in a circumferential array. The preload springs 13 are embedded in the corresponding spring grooves 14, and their outer ends abut against the inner wall of the valve body 1. The spring support ring 12 evenly transmits the elastic force generated by the multiple circumferentially distributed preload springs 13 to the annular preload member 4, enabling the valve seat body 3 to obtain a balanced and stable axial preload force.

[0033] As attached Figure 2As shown, the inner circular surface of the valve seat groove 6 is provided with an annular sealing groove 15. A bidirectional spring energy storage sealing ring 16, i.e., a PTFE bidirectional spring energy storage sealing ring, is provided in the annular sealing groove 15. The outer circular surface of the bidirectional spring energy storage sealing ring 16 is in close contact with the inner circular surface of the annular sealing groove 15, and the inner circular surface of the bidirectional spring energy storage sealing ring 16 is in close contact with the outer circular surface of the valve seat body 3. The spring support ring 12 is also provided with a limiting flange 17 that extends into the annular sealing groove 15 to restrict the bidirectional spring energy storage sealing ring 16 in the annular sealing groove 15. The bidirectional spring energy storage sealing ring 16 achieves a reliable seal between the valve seat body 3 and the valve body 1, and can adapt to the axial sliding of the valve seat body 3 and low temperature conditions, thereby improving the sealing reliability.

[0034] As attached Figure 2 and attached Figure 6 As shown, the ball 2 has top blocks 18 installed at its upper and lower ends for pushing the valve seat body 3. When the top blocks 18 rotate synchronously with the ball 2, they have a first position where they are disengaged from the valve seat body 3 and a second position where they apply a force to the valve seat body 3 in a direction away from the ball 2. The top blocks 18, which rotate synchronously with the ball 2 at its upper and lower ends, can push the valve seat body 3 away from the ball 2 when it rotates to the second position, achieving active retraction of the valve seat body 3. This allows for reliable separation of the valve seat body 3 from the ball 2, reduces friction between them, provides space for disassembly and assembly of the ball 2, and improves the convenience of valve maintenance.

[0035] As attached Figure 2 and attached Figure 6 As shown, the ball 2 has an annular mounting groove 19 at both its upper and lower ends. The top block 18 is connected to the corresponding annular mounting groove 19 by two screws, and the top block 18 has an arc surface 20 that fits against the inner circular surface of the annular mounting groove 19. Through the cooperation between the annular mounting groove 19 and the arc surface 20 of the top block 18, the top block 18 is accurately positioned, and the screws are used to fix the top block 18 to the ball 2, so that the top block 18 can rotate stably with the ball 2 and transmit the pushing force, thereby improving the stability and reliability of the valve seat pushing process.

[0036] As attached Figure 7As shown, the valve seat body 3 also has an annular positioning groove 21 at its inner end. A valve seat sealing ring 22 is embedded in the annular positioning groove 21 to form a seal with the surface of the ball 2. Multiple axially extending pressure stabilizing grooves 23 are formed on the inner circular surface of the annular sealing groove 15. An anti-loosening flange 24, extending inwards at the position corresponding to its outer end, is provided on the outer circular surface of the annular positioning groove 21. The anti-loosening flange 24 forms a limiting cone surface 25 to support the outer end of the valve seat sealing ring 22. The valve seat sealing ring 22 is embedded in the annular positioning groove 21, facilitating disassembly and independent replacement, reducing maintenance costs. Simultaneously, the pressure stabilizing groove 23 helps balance the pressure on the inner and outer sides of the valve seat sealing ring 22 during disassembly and assembly, facilitating smooth disassembly. Furthermore, the limiting cone surface 25 formed by the anti-loosening flange 24 supports and limits the valve seat sealing ring 22, suppressing the outer deformation caused by the ball 2 acting on the valve seat sealing ring 22, ensuring the structural stability and sealing reliability of the valve seat sealing ring 22.

[0037] As attached Figure 8 As shown, the device also includes a valve seat ejection fixture 26, which includes a fixture nut 27 and an adjusting screw 28. At least one positioning hole 29 is provided on the outer circumference of the valve seat body 3. A positioning pin 30 for insertion into the positioning hole 29 is welded to the outer periphery of the fixture nut 27. The adjusting screw 28 is threadedly engaged with the fixture nut 27, and the central axis of the adjusting screw 28 extends parallel to the central axis of the valve seat body 3. A pad 31 is sandwiched between the inner end of the adjusting screw 28 and the inner wall of the valve body 1. The valve seat ejection fixture 26 is quickly connected to the valve seat body 3 via the positioning pin 30. Tightening the adjusting screw 28 utilizes the reaction force between it and the valve body 1 to drive the valve seat body 3 axially, achieving smooth ejection of the valve seat body 3 and reducing the difficulty of valve seat disassembly. Furthermore, the pad 31 prevents the adjusting screw 28 from directly acting on the valve body 1, reducing damage to the valve body 1 during disassembly.

[0038] Working principle: 1. The ball valve adopts an upper-mounted cast steel fixed shaft structure. The valve body 1 and valve cover are connected by bolts. The valve seat body 3, annular pre-tightening part 4 and spring assembly 5 are combined to form the valve seat structure. The ball 2 and top block 18 are fixed by screws. 2. When the valve is in normal operation, by locking the annular preload 4, the valve seat body 3 is tightly fitted with the sealing surface of the ball 2 under the elastic preload force of the spring assembly 5, forming an initial seal; 3. Under ultra-low temperature conditions, the shrinkage of the annular pre-tightening component 4 can compensate for the shrinkage deformation of the sealing surface of the valve seat body 3 and the valve body 1, ensuring that the sealing surface always fits the ball 2, thus achieving good sealing under ultra-low temperature conditions. 4. When online maintenance is required, simply loosen the bolt above the annular preload 4. The annular preload 4 will automatically expand under the pressure of the spring preload, releasing the spring compression space. At this time, the spring compression preload is removed. After rotating the ball 2 more than 90°, the top block 18 on the ball 2 pushes the valve seat body 3 on both sides to the bottom of the valve seat groove 6. Since there is no spring force at this time, the valve seat body 3 is held at the bottom position, and the ball 2 is separated from the sealing surface of the valve seat body 3. Rotate the ball 2 again to keep the ball 2 in the fully open position. At this time, the ball 2 has the smallest crotch width, and there is enough space to remove the ball 2. 5. After fully opening ball 2, lift ball 2 out of valve body 1, and then use simple tooling to push out valve seat body 3, completing the online disassembly and assembly.

Claims

1. A valve seat structure for a cryogenic top-mounted fixed ball valve, installed inside the valve body (1) of the ball valve, for forming a sealing fit with a ball (2) disposed inside the ball valve when the ball valve is closed; characterized in that: The valve body (1) includes a valve seat body (3), an annular pre-tightening member (4), and a spring assembly (5). A valve seat groove (6) is provided in the valve body (1). The valve seat body (3) is axially slidably disposed in the valve seat groove (6). The annular pre-tightening member (4) is disposed on the outer periphery of the valve seat body (3). An annular sealing flange (7) extending outward is provided at the inner end of the valve seat body (3). The spring assembly (5) is disposed in the valve body (1) to apply an axial spring force to the annular pre-tightening member (4) in the direction of the annular sealing flange (7). A pre-tightening force conversion structure is provided between the annular sealing flange (7) and the annular pre-tightening member (4), so that when the annular pre-tightening member (4) contracts due to temperature reduction, it generates an axial force on the valve seat body (3) in the direction of the ball (2).

2. The valve seat structure of a cryogenic top-mounted fixed ball valve according to claim 1, characterized in that: The annular sealing flange (7) has a first annular conical surface (8) on the side near the annular preload member (4), and the annular preload member (4) has a second annular conical surface (9) that is adapted to the first annular conical surface (8). The first annular conical surface (8) and the second annular conical surface (9) cooperate to form the preload force conversion structure.

3. The valve seat structure of a cryogenic top-mounted fixed ball valve according to claim 2, characterized in that: The annular pretensioner (4) includes multiple arc-shaped connecting blocks (10) arranged sequentially along the circumference. Adjacent arc-shaped connecting blocks (10) are hinged together. Two arc-shaped connecting blocks (10) located at the beginning and end of the arrangement direction of the multiple arc-shaped connecting blocks (10) are detachably connected by bolts, so that the multiple arc-shaped connecting blocks (10) together enclose and form an annular structure.

4. The valve seat structure of a cryogenic top-mounted fixed ball valve according to claim 3, characterized in that: At least two of the multiple arc-shaped connecting blocks (10) have arc-shaped conical surfaces (11) on the side facing the annular sealing flange (7). Each arc-shaped conical surface (11) is arranged circumferentially at intervals or continuously, and forms the second annular conical surface (9).

5. The valve seat structure of a cryogenic top-mounted fixed ball valve according to claim 2, characterized in that: The spring assembly (5) includes a spring support ring (12) and a plurality of preload springs (13). The spring support ring (12) is sleeved on the outer periphery of the valve seat body (3) and sandwiched between the annular preload member (4) and the inner wall of the valve body (1). On the end face of the spring support ring (12) away from the annular preload member (4), a plurality of spring grooves (14) are distributed in a circular array, with a number equivalent to the number of preload springs (13). The preload springs (13) are embedded in the corresponding spring grooves (14), and the outer end of the preload springs (13) abuts against the inner wall of the valve body (1).

6. The valve seat structure of a cryogenic top-mounted fixed ball valve according to claim 5, characterized in that: The inner circular surface of the valve seat groove (6) is provided with an annular sealing groove (15), and a bidirectional spring energy storage sealing ring (16) is provided in the annular sealing groove (15). The outer circular surface of the bidirectional spring energy storage sealing ring (16) is in close contact with the inner circular surface of the annular sealing groove (15), and the inner circular surface of the bidirectional spring energy storage sealing ring (16) is in close contact with the outer circular surface of the valve seat body (3). The spring support ring (12) is also provided with a limiting flange (17) that extends into the annular sealing groove (15) to restrict the bidirectional spring energy storage sealing ring (16) in the annular sealing groove (15).

7. The valve seat structure of a cryogenic top-mounted fixed ball valve according to claim 1, characterized in that: The ball (2) has a top block (18) installed at its upper and lower ends for pushing the valve seat body (3). When the top block (18) rotates synchronously with the ball (2), it has a first position that is detached from the valve seat body (3) and a second position that applies a force to the valve seat body (3) in a direction away from the ball (2).

8. The valve seat structure of a cryogenic top-mounted fixed ball valve according to claim 7, characterized in that: The sphere (2) has an annular mounting groove (19) at its upper and lower ends respectively. The top block (18) is connected to the corresponding annular mounting groove (19) by screws, and the top block (18) has an arc surface (20) that fits against the inner circular surface of the annular mounting groove (19).

9. The valve seat structure of a cryogenic top-mounted fixed ball valve according to claim 1, characterized in that: The valve seat body (3) is also provided with an annular positioning groove (21) at its inner end. A valve seat sealing ring (22) is embedded in the annular positioning groove (21) for fitting and sealing with the surface of the ball (2). Multiple pressure stabilizing grooves (23) extending axially are provided on the inner circular surface of the annular sealing groove (15). An anti-loosening flange (24) extending inward in a circumferential direction is provided on the outer circular surface of the annular positioning groove (21) corresponding to its outer end. The anti-loosening flange (24) forms a limiting cone surface (25) for supporting the outer end of the valve seat sealing ring (22).

10. The valve seat structure of a cryogenic top-mounted fixed ball valve according to claim 1, characterized in that: It also includes a valve seat ejection fixture (26), which includes a fixture nut (27) and an adjusting screw (28). The outer circumference of the valve seat body (3) is provided with at least one positioning hole (29). The outer periphery of the fixture nut (27) is fixedly provided with a positioning pin (30) for inserting into the positioning hole (29). The adjusting screw (28) is threadedly engaged with the fixture nut (27), and the central axis of the adjusting screw (28) extends parallel to the central axis of the valve seat body (3). A pad (31) is sandwiched between the inner end of the adjusting screw (28) and the inner wall of the valve body (1).

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