A low-temperature top-mounted triple-offset butterfly valve

Abstract

The present invention belongs to the technical field of valve bodies, and relates to a low-temperature top-mounted triple-offset butterfly valve, which includes a valve body. During use, both ends of the valve body are connected to pipelines by butt welding. The valve body is hermetically and limit-connected to a bottom cover, and the upper end of the bottom cover is hermetically and limit-connected to a top cover. A valve seat installation boss is constructed in the inner cavity of the valve body, and a valve seat assembly is limit-installed in the inner hole of the valve seat installation boss. A valve shaft is rotatably arranged on the valve body. The valve shaft extends out from the upper cavity at the top of the valve body and sequentially passes through the bottom cover and the top cover. Dynamic seals are respectively formed between the valve shaft and the inner holes of the top cover and the bottom cover. A valve plate assembly is installed on the valve shaft, and the valve plate assembly cooperates with the valve seat assembly. This valve has the advantages of high online maintenance efficiency, good sealing performance, high dynamic stability, not easy to jam, and long service life. Its excellent comprehensive performance ensures that it can meet the requirements of cutting off or regulating low-temperature media.

Description

Technical Field

[0001] The invention belongs to the technical field of valve bodies and relates to a cryogenic top-mounted triple-eccentric butterfly valve. Background Art

[0002] With the implementation of the national coal-to-gas plan, liquefied natural gas (LNG) has rapidly emerged as a new type of clean and efficient energy. The country plans to increase the proportion of natural gas in the total energy consumption to 80% by 2050, which has greatly increased the demand for valves in low-temperature working conditions such as LNG, and the market scale has increased sharply. However, the design and manufacturing technologies of cryogenic valves are still basically monopolized by foreign countries. With the rapid development of the LNG industry in China, it has become more urgent to design and manufacture cryogenic valves with independent intellectual property rights.

[0003] Cryogenic butterfly valves are widely used in the LNG industry. Their key technologies include: 1. Increasing the low-temperature elasticity of the sealing pair from the aspects of materials and structures to avoid seal failure or movement jamming of components under low-temperature working conditions. 2. Allowing on-line maintenance to ensure that the valve internals can be quickly disassembled from the top of the valve and the valve stem has a function of preventing blowing out. 3. Avoiding sudden changes in the structural shape or local stress concentration that may cause elastoplastic deformation of components. 4. Meeting the requirements of fire prevention and anti-static.

[0004] At present, most cryogenic butterfly valves at home and abroad adopt a side-opening window structure, and on-line maintenance of the valve is achieved through a side inspection window. However, the maintenance space of valves with this structure is limited. When the valve internals are severely damaged or the valve diameter is small, it is difficult to carry out maintenance work, and the maintenance cycle is long, resulting in waste of user costs. Most of the sealing valve seats are integral, which is not conducive to processing and subsequent maintenance work, thus reducing the reliability and maintainability of valve operation. Summary of the Invention

[0005] Aiming at the above problems, the invention provides a cryogenic top-mounted triple-eccentric butterfly valve, which has the advantages of high on-line maintenance efficiency, good sealing performance, high dynamic stability, not easy to jam, long service life, etc. Its excellent comprehensive performance ensures that it can meet the requirements of cutting off or regulating cryogenic (-196 °C) media.

[0006] According to the technical solution of the invention: a cryogenic top-mounted triple-eccentric butterfly valve includes a valve body. When in use, both ends of the valve body are connected to pipelines by butt welding. It is characterized in that the valve body is hermetically and limit-connected to a bottom upper cover, and the upper end of the bottom upper cover is hermetically and limit-connected to a top upper cover;

[0007] A valve seat installation boss is constructed in the inner cavity of the valve body, and a valve seat assembly is limit-installed in the inner hole of the valve seat installation boss;

[0008] The valve shaft is rotatably arranged on the valve body. The valve shaft extends out from the upper cavity at the top of the valve body and successively penetrates through the bottom upper cover and the top upper cover. Dynamic seals are respectively formed between the valve shaft and the inner holes of the top upper cover and the bottom upper cover. A valve plate assembly is installed on the valve shaft, and the valve plate assembly cooperates with the valve seat assembly.

[0009] The valve plate assembly includes a valve plate. The valve shaft and the valve plate are connected by key fitting. A guiding groove extending axially is arranged on the valve shaft. A positioning hole is arranged at the upper end of the groove bottom plate of the guiding groove. A positioning boss of the valve plate is provided with a limiting bolt in a mating manner, and the limiting bolt is in threaded connection with the positioning hole to limit and fix the valve plate and the valve shaft.

[0010] The lower part of the valve shaft extends into the lower shaft hole of the valve body and is arranged in a first bushing. The length of the guiding groove is greater than the length of the first bushing.

[0011] As a further improvement of the present invention, the valve seat assembly includes a split valve seat and a pressing ring sleeved on the circumferential surface of the split valve seat. A plurality of internal threaded holes are evenly distributed on the circumferential surface of the pressing ring. Each internal threaded hole is in threaded connection with a first set screw and a second set screw. A first disc spring is arranged between the first set screw and the second set screw. The outer end of the second set screw abuts against the flange surface of the split valve seat. A first wire retaining ring is arranged in a mating manner in the axial outer end groove of the pressing ring. The radial outer part of the first wire retaining ring is arranged in the groove of the inner hole of the valve seat installation boss.

[0012] As a further improvement of the present invention, a second bushing is arranged in a limiting manner in the inner hole of the top upper cover. The second bushing and the valve shaft and the top upper cover are respectively in sealing cooperation through a balance sealing ring. A packing assembly is arranged above the second bushing, and the packing assembly is axially limited by a packing pressing plate.

[0013] As a further improvement of the present invention, the packing pressing plate is connected to the upper flange surface of the top upper cover through a connecting bolt. The connecting bolt penetrates through the packing pressing plate, and a limiting sleeve is sleeved on the bolt body of the connecting bolt extending to the outside of the packing pressing plate. A disc spring is arranged in the inner cavity of the limiting sleeve. The upper end of the disc spring abuts against the inner cavity top plate of the limiting sleeve, and the lower end of the disc spring presses on the packing pressing plate. The limiting sleeve is limited and fixed on the connecting bolt through a nut.

[0014] As a further improvement of the present invention, the split valve seat and the valve seat installation boss are in sealing cooperation through a first wound gasket.

[0015] As a further improvement of the present invention, the bottom upper cover and the top upper cover are mutually matched through a stepped surface and are circumferentially limited by a first anti-rotation pin; the bottom upper cover and the valve body are mutually matched through a stepped surface and are circumferentially limited by a second anti-rotation pin.

[0016] As a further improvement of the present invention, an isolation drip tray is welded on the outer surface of the top upper cover.

[0017] As a further improvement of the present invention, a third bushing is arranged for inner hole limit of the bottom upper cover, and the upper end of the third bushing is axially positioned by a second wire snap ring.

[0018] As a further improvement of the present invention, a second spiral wound gasket is arranged between the bottom upper cover and the valve body, and a third spiral wound gasket is arranged between the bottom upper cover and the top upper cover.

[0019] As a further improvement of the present invention, a bearing seat is arranged for inner hole limit of the top upper cover, and the valve shaft is supported on the bearing seat through a bearing ring.

[0020] The technical effects of the present invention are as follows: 1. Adopting a positive top-mounted structure, it has good on-line maintainability, good valve sealing performance, small torque required for the actuator, can long-term meet the ANSI VI class sealing grade requirements, and can not only achieve cut-off but also achieve the regulating function.

[0021] 2. The valve adopts a split valve seat, which is easy to process; the structure of fixing the valve seat with a wire snap ring and a set screw is compact, has good reliability, and the valve seat and the sealing ring have good interchangeability.

[0022] 3. The split valve seat and the multi-layer sealing ring realize self-adjusting centering of the sealing pair, enabling the sealing pair to be in close contact, achieving bidirectional tight closing, and the eccentric sealing pair design ensures low friction during the closing process of the valve seat and the valve plate, the valve is not easy to jam, and has good stability under low-temperature working conditions.

[0023] 4. The streamlined valve plate design optimizes the cross-section of the valve plate according to fluid dynamics, which not only enhances the strength of the valve plate, improves the forward and reverse sealing ability of the valve, but also reduces the medium eddy current, lowers the valve pressure loss, and improves the flow capacity of the valve.

[0024] 5. The packing assembly is located in the extended top upper cover, away from the valve cavity, ensuring that the packing temperature is above 0 degrees, and improving the reliability of the packing seal.

[0025] 6. The micro-leakage stuffing box structure design adopts a double-redundancy sealing structure of a live-loaded packing assembly combined with two balance sealing rings, a sealing mechanism design of a graphite packing assembly combined with two balance sealing rings, and a disc washer cooperating with a limit sleeve to achieve live-loaded fastening of the packing assembly, and can effectively prevent fire, achieving micro-leakage sealing at the valve shaft.

[0026] 7. In addition to the flat key connection between the valve shaft and the valve plate, a limit bolt is added for positioning the valve plate. While effectively ensuring the connection strength, it can effectively reduce the wear and jamming risks between the valve shaft and the bottom flange; and after the position of the limit bolt in the guide groove is adjusted, the valve shaft together with the valve plate assembly can be withdrawn from the upper cavity at the top of the valve body, facilitating maintenance. Description of the Drawings

[0027] Figure 1 This is a structural schematic diagram of the present invention.

[0028] Figure 2 This is an axonometric view of the valve body.

[0029] Figure 3 This is a perspective view of the split valve seat.

[0030] Figure 4 This is a sectional view of the split valve seat.

[0031] Figure 5 This is an axonometric view of the valve plate.

[0032] Figure 6 This is a structural schematic diagram of the connection between the valve shaft and the valve plate assembly.

[0033] Figure 7 This is an axonometric sectional view of the installation of the packing gland.

[0034] Figure 8 This is an axonometric view of the part where the valve shaft is connected to the valve plate.

[0035] Explanation of reference numerals: 1 - bottom flange, 2 - first bushing, 3 - valve seat assembly, 3 - 1 - valve seat, 3 - 2 - pressure ring, 3 - 3 - first wire snap ring, 3 - 4 - first set screw, 3 - 5 - first disc spring washer, 3 - 6 - second set screw, 4 - valve body, 4 - 1 - valve seat positioning boss, 4 - 2 - valve body reinforcing rib, 4 - 3 - position identification, 5 - valve plate assembly, 5 - 1 - pressure ring, 5 - 2 - valve plate, 5 - 3 - socket head cap screw, 5 - 4 - second disc spring washer, 5 - 5 - sealing ring, 5 - 6 - fourth spiral wound gasket, 5 - 7 - flat key, 5 - 8 - limit bolt, 5 - 9 - third disc spring washer, 5 - 10 - process boss, 5 - 11 - first keyway, 5 - 12 - positioning boss, 6 - valve shaft, 6 - 1 - second keyway, 6 - 2 - guiding groove, 6 - 3 - positioning hole, 7 - flat key, 8 - first spiral wound gasket, 9 - second spiral wound gasket, 10 - third spiral wound gasket, 11 - first anti - rotation pin, 12 - bearing ring, 13 - bearing housing, 14 - balance sealing ring, 15 - packing gland, 16 - limit sleeve, 17 - disc spring, 18 - packing assembly, 19 - bushing, 20 - isolation drip tray, 21 - top cover, 22 - first stud, 23 - second wire snap ring, 24 - second stud, 25 - bottom top cover, 26 - second anti - rotation pin, 27 - second bushing. Detailed implementation manners

[0036] The following further explains the detailed implementation manners of the present invention with reference to the accompanying drawings.

[0037] As Figures 1 - 8As shown in the figure, the present invention is a low-temperature top-mounted triple-eccentric butterfly valve, including a valve body 4. When in use, both ends of the valve body 4 are connected to the pipeline by butt welding. The valve body 4 is hermetically and limit-connected to the bottom upper cover 25, and the upper end of the bottom upper cover 25 is hermetically and limit-connected to the top upper cover 21.

[0038] As Figure 2 shown in the figure, a valve seat installation boss 4-1 is constructed in the inner cavity of the valve body 4, and the valve seat assembly 3 is limit-installed in the inner hole of the valve seat installation boss 4-1. In order to effectively enhance the strength of the valve body 4, multiple reinforcing ribs 4-2 are provided on the surface of the valve body 4 to improve the stress condition and the distribution of the temperature field of the valve body 4. The cross-sectional structure of the valve plate is designed according to fluid dynamics, which not only enhances the strength of the valve plate but also effectively reduces the pressure loss of the valve. The valve body 4 is also provided with a position mark 4-3, which is convenient for preventing misplacement and positioning during the processing.

[0039] A valve shaft 6 is rotatably arranged on the valve body 4. The valve shaft 6 extends out from the upper cavity at the top of the valve body 4 and sequentially passes through the bottom upper cover 25 and the top upper cover 21. Dynamic seals are respectively formed between the valve shaft 6 and the inner holes of the top upper cover 21 and the bottom upper cover 25. A valve plate assembly 5 is installed on the valve shaft 6, and the valve plate assembly 5 cooperates with the valve seat assembly 3.

[0040] As Figure 5 shown in the figure, the valve plate assembly 5 includes a valve plate 5-2. The valve shaft 6 and the valve plate 5-2 are connected by a flat key 5-7. A guiding groove 6-2 extending along the axial direction is provided on the valve shaft 6. A positioning hole 6-3 is provided at the upper end of the bottom plate of the guiding groove 6-2. A positioning boss 5-12 of the valve plate 5-2 is provided with a limit bolt 5-8 in cooperation. The limit bolt 5-8 is threadedly connected with the positioning hole 6-3 to limit and fix the valve plate 5-2 and the valve shaft 6. As Figure 6 shown in the figure, in specific practice, a fourth winding gasket 5-6 and a sealing ring 5-5 are limit-set on the working surface of the valve plate 5-2. The sealing ring 5-5 is pressed by a retainer ring 5-1. The sealing ring 5-5 serves as a redundant seal supplement for the sealing ring 5-5, and presses one end of the sealing ring to compensate for the sealing force of the sealing ring, which is beneficial to ensuring that the valve can meet the ANSI Ⅵ class sealing grade requirements for a long time. The retainer ring 5-1 is fixed to the valve plate 5-2 by an internal hexagonal screw 5-3, and a second disc washer 5-4 is provided on the internal hexagonal screw 5-3.

[0041] In the present invention, the positioning between the valve plate 5-2 and the valve shaft 6 and the self-centering between the sealing ring 5-5 provided on the valve plate 5-2 and the split valve seat 3-1 are beneficial to the reliability of the seal. The split valve seat 3-1 and the sealing ring 5-5 can be interchanged, which greatly improves the reliability of the product, saves space, has good sealing performance and good maintainability. Two process bosses 5-10 are also provided on the valve plate 5-2.

[0042] As Figure 8As shown, the lower part of the valve shaft 6 extends into the lower shaft hole of the valve body 4 and is arranged in the first bushing 2, and the length of the guiding groove 6-2 is greater than the length of the first bushing 2. As Figure 1 shown, in practice, the lower end of the first bushing 2 is limited and fixed by the bottom flange 1 fixed on the valve body 4. A second keyway 6-1 is arranged on the valve shaft 6, and a flat key 5-7 is arranged in the second keyway 6-1. The flat key 5-7 is matched with the first keyway 5-11 arranged on the valve plate 5-2 to prevent circumferential rotation between them, so as to achieve the effect of transmitting the action torque. At the same time, a limit bolt 5-8 is arranged for positioning to prevent axial end play between the valve plate 5-2 and the valve shaft 6, and the disc washer 5-9 plays a role in preventing the limit bolt 5-8 from loosening. The sealing ring 5-5 adopts a multi-layer type and can ensure a certain elasticity even at low temperatures.

[0043] As Figure 3 , 4 shown, the valve seat assembly 3 includes a split valve seat 3-1 and a pressing ring 3-2 sleeved on the circumferential surface of the split valve seat 3-1. A plurality of internal threaded holes are evenly arranged on the circumferential surface of the pressing ring 3-2. Each internal threaded hole is threadedly connected with a first set screw 3-4 and a second set screw 3-6. A first disc washer 3-5 is arranged between the first set screw 3-4 and the second set screw 3-6. The outer end of the second set screw 3-6 abuts against the flange surface of the split valve seat 3-1. A first wire retaining ring 3-3 is arranged in cooperation with the axial outer end groove of the pressing ring 3-2. The radial outer part of the first wire retaining ring 3-3 is arranged in the groove of the inner hole of the valve seat mounting boss 4-1. That is, a part of the first wire retaining ring 3-3 is installed in the groove of the valve body 4, and a part is installed in the pressing ring 3-2 to achieve the axial positioning effect of the valve seat assembly 3.

[0044] The split valve seat 3-1 and the valve seat mounting boss 4-1 are hermetically matched through a first spiral wound gasket 8. The first spiral wound gasket 8 is arranged in the groove at one end of the split valve seat 3-1. By adjusting the second set screw 3-6 and the first set screw 3-4, the pressing force on the first spiral wound gasket 8 can be adjusted to achieve reliable sealing.

[0045] The valve seat assembly 3 and the valve body 4 adopt a detachable structure and can be maintained during use; during the production process, production can be effectively facilitated. The middle part of the valve body 4 is provided with an upper cavity with a circular or oval structure, which can be used as the installation channel and maintenance channel for the valve seat assembly 3, the valve shaft 6 and the valve plate assembly 5.

[0046] The inner hole of the top cover 21 is provided with a second bushing 19. The second bushing 19 is hermetically fitted with the valve shaft 6 and the top cover 21 respectively through balance sealing rings 14. The two balance sealing rings 14 achieve double redundant sealing to meet the micro-leakage requirement. A packing assembly 18 is arranged above the second bushing 19, and the packing assembly 18 is axially limited by a packing pressing plate 15. In practice, the packing assembly 18 uses graphite packing, which can have a fireproof function.

[0047] As Figure 7 shown, the packing pressing plate 15 is connected to the upper flange surface of the top cover 21 through connecting bolts. The connecting bolts penetrate through the packing pressing plate 15, and a limiting sleeve 16 is sleeved on the bolt body of the connecting bolt extending to the outside of the packing pressing plate 15. A disc spring 17 is arranged in the inner cavity of the limiting sleeve 16. The upper end of the disc spring 17 abuts against the inner cavity top plate of the limiting sleeve 16, and the lower end of the disc spring 17 presses against the packing pressing plate 15. The limiting sleeve 16 is limited and fixed on the connecting bolt through a nut. The pressing and fixing of the packing assembly 18 are realized. The deformation of the disc spring 17 is determined by the limiting sleeve, and the pressing force generated by its deformation continuously acts on the packing assembly. Therefore, the magnitude of the pressing force can be adjusted through the limiting sleeve 16 and can be adjusted according to actual needs to realize the live load of the packing assembly. This structure is flexible and effective.

[0048] The bottom cover 25 and the top cover 21 are mutually matched through a stepped surface and are circumferentially limited by a first anti-rotation pin 11. The top cover 21 and the bottom cover 25 are fixedly connected through a first bolt 22 and corresponding nuts; the bottom cover 25 and the valve body 4 are mutually matched through a stepped surface and are circumferentially limited by a second anti-rotation pin 26. The bottom cover 25 and the valve body 4 are fixedly connected through a second bolt 24 and corresponding nuts.

[0049] An isolation drip tray 20 is welded on the outer surface of the top cover 21.

[0050] The inner hole of the bottom cover 25 is provided with a third bushing 27. The upper end of the third bushing 27 is axially positioned by a second wire retaining ring 23 for fixing the installation of the valve shaft 6 and guiding the valve movement.

[0051] A second spiral wound gasket 9 is arranged between the bottom cover 25 and the valve body 4, and a third spiral wound gasket 10 is arranged between the bottom cover 25 and the top cover 21.

[0052] The inner hole of the top cover 21 is provided with a bearing seat 13, and the valve shaft 6 is supported on the bearing seat 13 through a bearing ring 12.

[0053] The working principle of the present invention is as follows: When the valve is opened, the valve shaft 6 drives the valve plate assembly 5 to rotate counterclockwise and gradually opens to 90° fully open. During this process, as the rotation angle changes, the flow area of the channel formed between the valve plate assembly 5 and the valve body 4 for the medium in the valve cavity changes, and thus the medium flow rate changes accordingly, thereby achieving the function of cutting off or regulating the medium. When the valve is closed, under the action of the actuator, the valve shaft 6 overcomes the medium pressure and the friction between the valve shaft and the packing assembly, drives the valve plate assembly 5 to rotate clockwise until the valve is completely closed, and the valve plate sealing surface is in close contact with the valve seat sealing surface to achieve the sealing effect.

[0054] When on-line maintenance is required, the actuator should be removed first, and then the packing assembly 18, the first stud 22 and the corresponding nuts should be loosened, and relevant components such as the top cover 21 should be removed; then the second stud 24 and the corresponding nuts should be loosened, and the bottom cover 21 and relevant components should be removed; the key step is to partially loosen the limit bolt 5-8, move it out of the positioning hole 6-3, pull out the valve shaft 6 to the bottom to separate it from the valve body 4, and then tighten the limit bolt 5-8, and the valve shaft 6 can be pulled out together with the valve plate assembly 5 from the upper cavity of the valve body. When the valve seat assembly 3 needs to be disassembled, the first set screw 3-4 should be partially loosened first, and the circlip should be taken out, and then the valve seat assembly can be disassembled. The disassembly process is simple and easy to operate. The precautions for reassembly after maintenance are basically the same as the disassembly process, and the installation steps are opposite to the disassembly process.

[0055] The present invention has the advantages of high on-line maintenance efficiency, good sealing performance, high dynamic stability, not easy to jam, long service life, etc. Its excellent comprehensive performance ensures that it can meet the requirements of cutting off or regulating the medium at low temperature (-196°C).

[0056] Obviously, the above embodiments are only examples for clear illustration and not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all the implementation manners here, and the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A low-temperature top-mounted triple-offset butterfly valve, comprising a valve body (4). During use, the two ends of the valve body (4) are connected to the pipeline by butt welding. It is characterized in that: The valve body (4) is hermetically and position - limitedly connected to the bottom upper cover (25), and the upper end of the bottom upper cover (25) is hermetically and position - limitedly connected to the top upper cover (21); The inner cavity of the valve body (4) is configured with a valve seat mounting boss (4 - 1), and the valve seat assembly (3) is position - limitedly installed in the inner hole of the valve seat mounting boss (4 - 1); A valve shaft (6) is rotatably arranged on the valve body (4). The valve shaft (6) extends out from the upper cavity at the top of the valve body (4) and sequentially penetrates through the bottom upper cover (25) and the top upper cover (21). Dynamic seals are respectively formed between the valve shaft (6) and the inner holes of the top upper cover (21) and the bottom upper cover (25). A valve plate assembly (5) is installed on the valve shaft (6), and the valve plate assembly (5) cooperates with the valve seat assembly (3); The valve plate assembly (5) includes a valve plate (5 - 2). The valve shaft (6) and the valve plate (5 - 2) are connected by a flat key (5 - 7). A guiding groove (6 - 2) extending axially is arranged on the valve shaft (6). A positioning hole (6 - 3) is arranged at the upper end of the groove bottom plate of the guiding groove (6 - 2). A positioning boss (5 - 12) of the valve plate (5 - 2) is provided with a limit bolt (5 - 8) in a mating way. The limit bolt (5 - 8) is threadedly connected with the positioning hole (6 - 3) to position - limit and fix the valve plate (5 - 2) and the valve shaft (6); The lower part of the valve shaft (6) extends into a first bushing (2) arranged in the lower shaft hole of the valve body (4), and the length of the guiding groove (6 - 2) is greater than the length of the first bushing (2).

2. The cryogenic top-mounted triple-offset butterfly valve according to claim 1, wherein: The valve seat assembly (3) includes a split valve seat (3 - 1) and a pressure ring (3 - 2) sleeved on the circumferential surface of the split valve seat (3 - 1). A plurality of internal threaded holes are evenly distributed on the circumferential surface of the pressure ring (3 - 2). Each internal threaded hole is threadedly connected with a first set screw (3 - 4) and a second set screw (3 - 6). A first disc spring washer (3 - 5) is arranged between the first set screw (3 - 4) and the second set screw (3 - 6). The outer end of the second set screw (3 - 6) abuts against the flange surface of the split valve seat (3 - 1). A first wire snap ring (3 - 3) is arranged in a mating way in the axial outer end groove of the pressure ring (3 - 2), and the radial outer part of the first wire snap ring (3 - 3) is arranged in the groove of the inner hole of the valve seat mounting boss (4 - 1).

3. The low-temperature type direct top-mounted triple-eccentric butterfly valve according to claim 1, characterized in that: A second bushing (19) is position - limitedly arranged in the inner hole of the top upper cover (21). The second bushing (19) and the valve shaft (6) and the top upper cover (21) are hermetically mated through a balance seal ring (14) respectively. A packing assembly (18) is arranged above the second bushing (19), and the packing assembly (18) is axially position - limited by a packing gland (15).

4. The cryogenic top-mounted triple-offset butterfly valve according to claim 3, characterized in that: The packing pressing plate (15) is connected to the upper flange surface of the top cover (21) through connecting bolts. The connecting bolts penetrate through the packing pressing plate (15), and a limit sleeve (16) is sleeved on the bolt body of the connecting bolt extending to the outside of the packing pressing plate (15). A disc spring (17) is arranged in the inner cavity of the limit sleeve (16). The upper end of the disc spring (17) abuts tightly against the inner cavity top plate of the limit sleeve (16), and the lower end of the disc spring (17) presses tightly against the packing pressing plate (15). The limit sleeve (16) is limited and fixed on the connecting bolt through a nut.

5. The cryogenic top-mounted triple-offset butterfly valve according to claim 2, characterized in that: A first spiral wound gasket (8) is used for sealing and mating between the split valve seat (3-1) and the valve seat mounting boss (4-1).

6. The cryogenic top-mounted triple-offset butterfly valve according to claim 1, wherein: The bottom top cover (25) and the top cover (21) are mutually mated through a stepped surface and circumferentially limited by a first anti-rotation pin (11); the bottom top cover (25) and the valve body (4) are mutually mated through a stepped surface and circumferentially limited by a second anti-rotation pin (26).

7. The cryogenic-type direct top-mounted triple-eccentric butterfly valve according to claim 1, wherein: An isolation drip tray (20) is welded on the outer surface of the top cover (21).

8. The cryogenic top-mounted triple-offset butterfly valve according to claim 1, wherein: A third bushing (27) is arranged in the inner hole of the bottom top cover (25) in a limited manner, and the upper end of the third bushing (27) is axially positioned by a second wire retaining ring (23).

9. The cryogenic top-mounted triple-offset butterfly valve according to claim 1, characterized in that: A second spiral wound gasket (9) is arranged between the bottom top cover (25) and the valve body (4), and a third spiral wound gasket (10) is arranged between the bottom top cover (25) and the top cover (21).

10. The cryogenic top-mounted triple-offset butterfly valve according to claim 1, characterized in that: A bearing seat (13) is arranged in the inner hole of the top cover (21) in a limited manner, and the valve shaft (6) is supported on the bearing seat (13) through a bearing ring (12).

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