Ultra-low temperature ball valve shaft sealing structure and its installation and disassembly methods

Abstract

The present invention is a valve shaft sealing structure of an ultra-low temperature ball valve and its installation method and disassembly method. The valve shaft sealing structure of the ultra-low temperature ball valve includes a packing group and an O-ring sealing assembly which are sequentially arranged in the stuffing box hole from bottom to top. The packing group includes a first nickel wire flexible graphite braided packing part, a flexible graphite pressed packing part and a second nickel wire flexible graphite braided packing part which are sequentially arranged in the stuffing box hole from bottom to top. The top of the O-ring sealing assembly is arranged below the top of the stuffing box hole, and the top of the O-ring sealing assembly can be axially fixed by a packing sleeve. The present invention solves the hidden dangers of leakage of valve shaft packing of traditional ultra-low temperature ball valves and inability to operate due to freezing of the valve shaft. By analyzing the packing sealing mechanism, a sealing structure of a packing group + O-ring seat ring assembly is optimized, which can not only improve the sealing performance of the O-ring, but also make it more convenient to disassemble and assemble the O-ring, thereby ensuring the sealing of the valve shaft of the ultra-low temperature ball valve and the operability of the valve shaft.

Description

Technical Field

[0001] The present invention relates to the technical field of ultra-low temperature ball valves, and in particular to an ultra-low temperature ball valve shaft sealing structure and an installation method and a disassembly method thereof. Background Art

[0002] As an efficient, low-carbon and clean fossil energy, natural gas has begun to replace primary energy sources such as coal and oil in many energy-using fields. It is an important bridge for the transition to a new energy system and a realistic choice for promoting energy transformation. Among them, LNG has gradually become the most active form of natural gas supply due to its advantages of easy transportation, diversified entities, strong flexibility, safety and efficiency. According to incomplete statistics, among the various types of valves used in liquefied natural gas (LNG) receiving stations, the number of ultra-low temperature ball valves accounts for more than 60%, and is widely used.

[0003] The traditional cryogenic ball valve shaft seal usually adopts the structure of Panseal 10 + flexible graphite packing group 11 + O-ring 12 (see Figure 6 ), the surface roughness of the parts in contact with the universal plug should be high, Ra≤0.2μm, and the outer surface of the valve shaft matched with the universal plug can be processed by Hawke energy technology (energy processing technology that uses the composite energy of activation energy and impact energy to process metal parts, and can make the surface of the parts reach mirror finish and realize modification in one processing) to make its roughness meet the requirements, while the roughness of the inner surface of the stuffing box hole matched with the universal plug is difficult to meet the requirements. Therefore, the universal plug does not actually achieve the expected sealing effect. In addition, a spring is added to the universal plug, and the universal plug, the valve shaft and the stuffing box hole are all interference fit. If you are not careful when installing the universal plug, there is a potential risk that the lip of the universal plug will be scratched and the sealing performance will be affected. In addition, the interference fit universal plug also increases the friction torque, which increases the operating torque of the cryogenic ball valve.

[0004] Therefore, the inventor, relying on many years of experience and practice in related industries, proposes a valve shaft sealing structure of an ultra-low temperature ball valve and an installation method and a disassembly method thereof to overcome the defects of the prior art. Summary of the invention

[0005] The purpose of the present invention is to provide a valve shaft sealing structure of an ultra-low temperature ball valve and an installation method and a disassembly method thereof, so as to solve the hidden dangers of valve shaft packing leakage and valve shaft freezing and inoperability of traditional ultra-low temperature ball valves. Through the analysis of the packing sealing mechanism, a sealing structure of a packing group + O-ring seat ring assembly is optimized, which can avoid scratches on the O-ring when installing it and facilitate disassembly during maintenance, thereby improving the sealing performance of the O-ring and making it more convenient to disassemble and install the O-ring, thereby ensuring the sealing of the valve shaft of the ultra-low temperature ball valve and the operability of the valve shaft.

[0006] The objective of the present invention is achieved in this way. A valve shaft sealing structure of an ultra-low temperature ball valve comprises a packing group and an O-ring sealing assembly which are sequentially arranged in a stuffing box hole from bottom to top. The packing group comprises a first nickel wire flexible graphite braided packing portion, a flexible graphite pressed packing portion and a second nickel wire flexible graphite braided packing portion which are sequentially arranged in the stuffing box hole from bottom to top. The top of the O-ring sealing assembly is arranged lower than the top of the stuffing box hole, and the top of the O-ring sealing assembly can be axially fixed by a packing sleeve.

[0007] In a preferred embodiment of the present invention, the O-ring sealing assembly includes an O-ring seat ring, and at least two dynamic sealing O-rings are arranged on the inner wall of the O-ring seat ring, and the dynamic sealing O-rings are used to seal the dynamic seal between the O-ring seat ring and the valve shaft; at least one static sealing O-ring is arranged on the outer wall of the O-ring seat ring, and the static sealing O-ring is used to seal the static seal between the O-ring seat ring and the stuffing box hole.

[0008] In a preferred embodiment of the present invention, an O-ring pressure plate is arranged above the O-ring seat ring, a third concave ring groove is arranged at the top of the O-ring seat ring, and a downwardly extending locking boss is arranged at the bottom end of the O-ring pressure plate, and the locking boss can be locked in the third concave ring groove.

[0009] In a preferred embodiment of the present invention, a plurality of first process holes for disassembly are provided on the top surface of the O-ring pressure plate.

[0010] In a preferred embodiment of the present invention, a dynamic sealing O-ring is disposed in the third concave ring groove, and the dynamic sealing O-ring is used for sealing between the O-ring seat ring, the valve shaft and the O-ring pressure plate.

[0011] In a preferred embodiment of the present invention, a first concave ring groove is provided on the inner wall of the O-ring seat ring, and the dynamic sealing O-ring is provided in the first concave ring groove; a second concave ring groove is provided on the outer wall of the O-ring seat ring, and the static sealing O-ring is provided in the second concave ring groove.

[0012] In a preferred embodiment of the present invention, a plurality of second process holes for disassembly are provided on the top surface of the O-ring seat ring.

[0013] The object of the present invention can also be achieved by providing a method for installing a valve shaft sealing structure of a cryogenic ball valve, which is used for installing the valve shaft sealing structure of the cryogenic ball valve, comprising the following steps:

[0014] Step a, inserting the first nickel wire flexible graphite braided packing part into the bottom of the packing box hole and compacting it;

[0015] Step b, inserting the pressed flexible graphite packing part into the stuffing box hole above the first nickel wire flexible graphite braided packing part and compacting it;

[0016] Step c, inserting the second nickel wire flexible graphite braided packing part into the stuffing box hole above the flexible graphite pressed packing part, and compacting it;

[0017] Step d, installing the O-ring sealing assembly into the stuffing box hole;

[0018] Step e: sequentially install and seal the packing gland and packing plate to complete the installation of the valve shaft sealing structure of the cryogenic ball valve.

[0019] In a preferred embodiment of the present invention, the O-ring sealing assembly includes an O-ring seat ring, and at least one dynamic sealing O-ring is arranged on the inner wall of the O-ring seat ring; at least one static sealing O-ring is arranged on the outer wall of the O-ring seat ring; an O-ring pressure plate is arranged above the O-ring seat ring, a third concave ring groove is arranged at the top of the O-ring seat ring, and a downwardly extending locking boss is arranged at the bottom end of the O-ring pressure plate; in step d, the dynamic sealing O-ring and the static sealing O-ring are installed into the O-ring seat ring, the O-ring seat ring is installed into the stuffing box hole, and the dynamic sealing O-ring is installed in the third concave ring groove.

[0020] The object of the present invention can also be achieved by providing a method for disassembling a valve shaft sealing structure of a cryogenic ball valve, which is used for disassembling the valve shaft sealing structure of the aforementioned cryogenic ball valve, comprising the following steps:

[0021] Step a, remove the packing gland and packing plate;

[0022] Step b, taking the O-ring pressing plate out of the stuffing box hole through the first process hole on the O-ring pressing plate of the O-ring sealing assembly;

[0023] Step c, taking out the O-ring seat ring of the O-ring sealing assembly from the stuffing box hole;

[0024] Step d: sequentially remove the second nickel wire flexible graphite braided packing part, the flexible graphite pressed packing part and the first nickel wire flexible graphite braided packing part to complete the disassembly of the valve shaft sealing structure of the ultra-low temperature ball valve.

[0025] As described above, the ultra-low temperature ball valve shaft sealing structure and the installation method and disassembly method thereof of the present invention have the following beneficial effects:

[0026] The valve shaft sealing structure of the ultra-low temperature ball valve of the present invention optimizes a sealing structure of a packing group + O-ring sealing assembly by analyzing the packing sealing mechanism, adopts nickel wire + flexible graphite braided packing, flexible graphite pressed packing, nickel wire + flexible graphite braided packing and O-ring combined sealing, and the O-ring sealing assembly is located in the packing box hole, which can not only improve the sealing performance of the O-ring, but also make the disassembly and assembly of the O-ring more convenient, thereby improving the sealing performance of the valve shaft and the operability of the valve shaft, and making the sealing safer and more reliable;

[0027] The O-ring seat ring + O-ring pressing plate of the present invention form a combined O-ring sleeve, which eliminates the problem of difficulty in assembly or disassembly of the traditional O-ring sleeve due to too many O-rings sealing the valve shaft;

[0028] In the valve shaft sealing structure of the ultra-low temperature ball valve of the present invention, no sealing member such as a wide-seal interference fit is used, thereby eliminating the uncertainty factor of the wide-seal seal and also reducing the friction torque of the valve shaft sealing assembly, thereby reducing the operating torque of the valve and making the valve operation easier;

[0029] The installation and disassembly method of the valve shaft sealing structure of the ultra-low temperature ball valve of the present invention eliminates the risk of scratching the O-ring during installation of the traditional valve shaft sealing structure, eliminates the potential leakage risk, and ensures the sealing performance of the O-ring. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The following drawings are only intended to illustrate and explain the present invention, and are not intended to limit the scope of the present invention.

[0031] in:

[0032] Figure 1 : is a schematic diagram of the valve shaft sealing structure of the ultra-low temperature ball valve of the present invention.

[0033] Figure 2 : It is a top view of the O-ring seat ring of the present invention.

[0034] Figure 3 :for Figure 2 Middle AA section view.

[0035] Figure 4 : It is a top view of the O-ring pressure plate of the present invention.

[0036] Figure 5 :for Figure 4 Middle BB section view.

[0037] Figure 6 : Schematic diagram of the valve shaft seal of a traditional ultra-low temperature ball valve.

[0038] In the figure:

[0039] 1. The first nickel wire flexible graphite braided packing part;

[0040] 2. Flexible graphite pressed packing part;

[0041] 3. The second nickel wire flexible graphite braided packing part;

[0042] 4. O-ring seat ring; 41. dynamic seal O-ring; 42. static seal O-ring; 43. O-ring pressure plate; 44. third concave ring groove; 45. locking boss; 46. first process hole; 48. second process hole;

[0043] 5. Stuffing box hole;

[0044] 6. Packing plate;

[0045] 7. Packing gland;

[0046] 8. Valve shaft;

[0047] 9. Valve cover;

[0048] 10. Pan plug; 11. Flexible graphite packing group; 12. O-ring. DETAILED DESCRIPTION

[0049] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described with reference to the accompanying drawings.

[0050] The specific embodiments of the present invention described herein are only used to explain the purpose of the present invention and cannot be understood as limiting the present invention in any way. Under the guidance of the present invention, technicians can conceive of any possible variations based on the present invention, which should be considered to belong to the scope of the present invention. It should be noted that when an element is referred to as "arranged on" another element, it can be directly on the other element or there can also be a central element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be a central element at the same time. The terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a mechanical connection or an electrical connection, or it can be the internal communication of two elements, it can be directly connected, or it can be indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances. The terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used herein are only for illustrative purposes and do not represent the only implementation method.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more related listed items.

[0052] like Figures 1 to 5As shown, the present invention provides a valve shaft sealing structure of an ultra-low temperature ball valve (ultra-low temperature ball valves generally work at less than -101°C, and work at -162°C for LNG), which is used for sealing between a valve cover 9 and a valve shaft 8, and includes a packing group and an O-ring sealing assembly sequentially arranged in a packing box hole from bottom to top, the packing group includes a first nickel wire flexible graphite braided packing portion 1 (composed of nickel wire + flexible graphite braided packing), a flexible graphite pressed packing portion 2, and a second nickel wire flexible graphite braided packing portion 3 (composed of nickel wire + flexible graphite braided packing) sequentially arranged in a packing box hole 5 (existing technology, arranged in the valve cover) from bottom to top, the top of the O-ring sealing assembly is arranged below the top of the stuffing box hole, that is, the top of the O-ring sealing assembly is below the pressure boundary line, and the top of the O-ring sealing assembly can be axially fixed by a packing sleeve 7 (existing technology).

[0053] The valve shaft sealing structure of the ultra-low temperature ball valve of the present invention optimizes a sealing structure of a packing group + O-ring sealing assembly by analyzing the packing sealing mechanism, adopts nickel wire + flexible graphite braided packing, flexible graphite pressed packing, nickel wire + flexible graphite braided packing and O-ring combined sealing, and the O-ring sealing assembly is located in the packing box hole, which can not only improve the sealing performance of the O-ring, but also make the disassembly and assembly of the O-ring more convenient, thereby improving the sealing performance of the valve shaft and the operability of the valve shaft, and making the sealing safer and more reliable;

[0054] In the valve shaft sealing structure of the ultra-low temperature ball valve of the present invention, no sealing member such as a wide plug interference fit is used, which reduces the friction torque of the valve shaft sealing assembly, thereby reducing the operating torque of the valve, making the valve operation easier.

[0055] Further, if Figure 1 As shown, the O-ring sealing assembly includes an O-ring seat ring 4, and at least two dynamic sealing O-rings 41 are arranged on the inner wall of the O-ring seat ring 4 (in the present embodiment, one dynamic sealing O-ring 41 is arranged at the middle position of the inner wall of the O-ring seat ring 4, and the other dynamic sealing O-ring 41 is arranged at the top of the inner wall of the O-ring seat ring 4). The dynamic sealing O-ring 41 is used for sealing the dynamic seal between the O-ring seat ring 4 and the valve shaft 8. Because the valve needs to be operated by the rotation of the valve shaft, the valve shaft 8 will rotate relative to the O-ring seat ring 4, so the sealing ring between the two adopts a dynamic sealing O-ring; a static sealing O-ring 42 is arranged on the outer wall of the O-ring seat ring 4, and the static sealing O-ring 42 is used for sealing the static seal between the O-ring seat ring 4 and the stuffing box hole 5. The O-ring seat ring 4 and the stuffing box hole 5 are relatively stationary, and the static sealing O-ring 42 can be used.

[0056] Further, if Figure 1 , Figure 2 , Figure 3 , Figure 4 , Figure 5As shown, an O-ring pressure plate 43 is arranged above the O-ring seat ring 4, a third concave ring groove 44 is arranged at the top of the O-ring seat ring 4, and a downwardly extending locking boss 45 is arranged at the bottom end of the O-ring pressure plate 43, and the locking boss 45 can be locked in the third concave ring groove 44.

[0057] The O-ring seat ring + O-ring pressure plate of the present invention form a combined O-ring sleeve, which eliminates the problem of difficulty in assembly or disassembly of the traditional O-ring sleeve due to too many O-rings sealing the valve shaft (because it is a dynamic seal, at least two O-rings).

[0058] Further, if Figure 4 , Figure 5 As shown, a plurality of first process holes 46 for disassembly are arranged on the top surface of the O-ring pressing plate 43. The first process holes 46 are threaded holes.

[0059] Further, if Figure 1 As shown, a dynamic sealing O-ring 41 is disposed in the third concave annular groove 44, and the dynamic sealing O-ring 41 is used for sealing between the O-ring seat ring 4, the valve shaft 8 and the O-ring pressure plate 43. The dynamic sealing O-ring 41 in the third concave annular groove 44 constitutes one of at least two dynamic seals between the valve shaft 8 and the O-ring seat ring 4.

[0060] Furthermore, a first concave groove is provided on the inner wall of the O-ring seat ring 4, and a dynamic seal O-ring 41 is provided in the first concave groove; a second concave groove is provided on the outer wall of the O-ring seat ring 4, and a static seal O-ring 42 is provided in the second concave groove.

[0061] Further, the number of the flexible graphite pressed packing parts 2 is two.

[0062] Further, if Figure 2 , Figure 3 As shown, the top surface of the O-ring seat ring 4 is provided with a plurality of second process holes 48 for disassembly. The second process holes 48 are threaded holes.

[0063] The present invention also provides a method for installing a valve shaft sealing structure of a cryogenic ball valve, which is used for installing the aforementioned valve shaft sealing structure of a cryogenic ball valve, and comprises the following steps:

[0064] Step a, insert the first nickel wire flexible graphite braided packing part 1 into the bottom of the packing box hole 5 and compact it (using a special tooling operation);

[0065] Step b, insert the flexible graphite pressed packing part 2 into the stuffing box hole 5 above the first nickel wire flexible graphite braided packing part 1 and compact it;

[0066] There can be multiple flexible graphite pressed packing parts 2. After one flexible graphite pressed packing part 2 is installed, it is compacted with a special tooling at the same time, and then the next flexible graphite pressed packing part 2 is installed, and so on until all the flexible graphite pressed packing parts 2 are installed.

[0067] Step c, insert the second nickel wire flexible graphite braided packing part 3 into the packing box hole 5 above the flexible graphite pressed packing part 2, and compact it (using a special tooling operation);

[0068] Step d, installing the O-ring sealing assembly into the stuffing box hole 5;

[0069] Specifically, install the dynamic seal O-ring 41 and the static seal O-ring 42 into the first concave ring groove and the second concave ring groove of the O-ring seat ring 4 respectively, and install the O-ring seat ring 4 into the stuffing box hole 5. Pay attention to the installation direction of the O-ring seat ring 4. The side of the O-ring seat ring 4 with the third concave ring groove faces upward; install the dynamic seal O-ring 41 in the third concave ring groove 44; then install the O-ring pressure plate 43.

[0070] Step e: sequentially install and seal the packing gland 7 and the packing plate 6 (existing technology) to complete the installation of the valve shaft sealing structure of the ultra-low temperature ball valve.

[0071] The packing gland 7 and the packing plate 6 are fixed by tightening bolts and nuts, and the nuts are tightened according to the torque required for packing sealing.

[0072] The present invention also provides a method for disassembling a valve shaft sealing structure of a cryogenic ball valve, which is used for disassembling the valve shaft sealing structure of the cryogenic ball valve, and comprises the following steps:

[0073] Step a, remove the packing gland 7 and the packing plate 6;

[0074] Step b, taking out the O-ring pressing plate 43 from the stuffing box hole 5 through the first process hole 46 on the O-ring pressing plate 43 of the O-ring sealing assembly;

[0075] Specifically, the threaded end of the special tool is screwed into the first process hole 46 on the O-ring pressing plate 43 , and the O-ring pressing plate 43 is taken out from the stuffing box hole 5 using the special tool.

[0076] Step c, taking out the O-ring seat ring of the O-ring sealing assembly from the stuffing box hole;

[0077] Specifically, the threaded end of the special tool is screwed into the second process hole 48 on the O-ring seat ring 4 , and the O-ring seat ring 4 is taken out from the stuffing box hole 5 using the special tool.

[0078] Step d: Use a special crochet hook to sequentially remove the second nickel wire flexible graphite braided packing part 3, the flexible graphite pressed packing part 2 and the first nickel wire flexible graphite braided packing part 1 to complete the disassembly of the valve shaft sealing structure of the ultra-low temperature ball valve.

[0079] The installation and disassembly method of the valve shaft sealing structure of the ultra-low temperature ball valve of the present invention eliminates the risk of scratching the O-ring during installation of the traditional valve shaft sealing structure, eliminates the potential leakage risk, and ensures the sealing performance of the O-ring.

[0080] As described above, the ultra-low temperature ball valve shaft sealing structure and the installation method and disassembly method thereof of the present invention have the following beneficial effects:

[0081] The valve shaft sealing structure of the ultra-low temperature ball valve of the present invention optimizes a sealing structure of a packing group + O-ring sealing assembly by analyzing the packing sealing mechanism, adopts nickel wire + flexible graphite braided packing, flexible graphite pressed packing, nickel wire + flexible graphite braided packing and O-ring combined sealing, and the O-ring sealing assembly is located in the packing box hole, which can not only improve the sealing performance of the O-ring, but also make the disassembly and assembly of the O-ring more convenient, thereby improving the sealing performance of the valve shaft and the operability of the valve shaft, and making the sealing safer and more reliable;

[0082] The O-ring seat ring + O-ring pressing plate of the present invention form a combined O-ring sleeve, which eliminates the problem of difficulty in assembly or disassembly of the traditional O-ring sleeve due to too many O-rings sealing the valve shaft;

[0083] In the valve shaft sealing structure of the ultra-low temperature ball valve of the present invention, no sealing member such as a wide-seal interference fit is used, thereby eliminating the uncertainty factor of the wide-seal seal and also reducing the friction torque of the valve shaft sealing assembly, thereby reducing the operating torque of the valve and making the valve operation easier;

[0084] The installation and disassembly method of the valve shaft sealing structure of the ultra-low temperature ball valve of the present invention eliminates the risk of scratching the O-ring during installation of the traditional valve shaft sealing structure, eliminates the potential leakage risk, and ensures the sealing performance of the O-ring.

[0085] The above description is only an illustrative embodiment of the present invention and is not intended to limit the scope of the present invention. Any equivalent changes and modifications made by any person skilled in the art without departing from the concept and principle of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A valve shaft sealing structure for a cryogenic ball valve, characterized in that: The invention comprises a packing group and an O-ring sealing assembly which are sequentially arranged in a packing box hole from bottom to top, wherein the packing group comprises a first nickel wire flexible graphite braided packing part, a flexible graphite pressed packing part and a second nickel wire flexible graphite braided packing part which are sequentially arranged in the packing box hole from bottom to top, the top of the O-ring sealing assembly is arranged lower than the top of the packing box hole, and the top of the O-ring sealing assembly can be axially fixed by a packing gland; the top of the packing gland is axially fixed by a packing pressure plate; The O-ring sealing assembly comprises an O-ring seat ring, at least two dynamic sealing O-rings are arranged on the inner wall of the O-ring seat ring, one dynamic sealing O-ring is arranged on the top of the inner wall of the O-ring seat ring, and the dynamic sealing O-ring is used to seal the dynamic seal between the O-ring seat ring and the valve shaft; at least one static sealing O-ring is arranged on the outer wall of the O-ring seat ring, and the static sealing O-ring is used to seal the static seal between the O-ring seat ring and the stuffing box hole; the inner wall of the O-ring seat ring is provided with a first concave ring groove, and the dynamic sealing O-ring is arranged in the first concave ring groove; the outer wall of the O-ring seat ring is provided with a second concave ring groove, and the static sealing O-ring is arranged in the second concave ring groove; An O-ring pressing plate is arranged above the O-ring seat ring, a third concave ring groove is arranged at the top of the O-ring seat ring, and a locking protrusion extending downward is arranged at the bottom of the O-ring pressing plate, and the locking protrusion can be locked in the third concave ring groove; A dynamic sealing O-ring is arranged in the third concave ring groove, and the dynamic sealing O-ring is used for sealing between the O-ring seat ring, the valve shaft and the O-ring pressing plate; The top surface of the O-ring pressing plate is provided with a plurality of first process holes for disassembly; The top surface of the O-ring seat ring is provided with a plurality of second process holes for disassembly.

2. A method for installing a valve shaft sealing structure of a cryogenic ball valve, characterized in that: The installation of the valve shaft sealing structure of the ultra-low temperature ball valve according to claim 1 comprises the following steps: Step a, inserting the first nickel wire flexible graphite braided packing part into the bottom of the packing box hole and compacting it; Step b, inserting the pressed flexible graphite packing part into the stuffing box hole above the first nickel wire flexible graphite braided packing part and compacting it; Step c, inserting the second nickel wire flexible graphite braided packing part into the stuffing box hole above the flexible graphite pressed packing part, and compacting it; Step d, installing the O-ring sealing assembly into the stuffing box hole; In step d, the dynamic seal O-ring and the static seal O-ring are installed into the O-ring seat ring, the O-ring seat ring is installed into the stuffing box hole, and the dynamic seal O-ring is installed in the third concave ring groove; then the O-ring pressure plate is installed; Step e: sequentially install and seal the packing gland and packing plate to complete the installation of the valve shaft sealing structure of the cryogenic ball valve.

3. A method for disassembling a valve shaft sealing structure of a cryogenic ball valve, characterized in that: The disassembly of the valve shaft sealing structure of the ultra-low temperature ball valve according to claim 1 comprises the following steps: Step a, remove the packing gland and packing plate; Step b, taking the O-ring pressing plate out of the stuffing box hole through the first process hole on the O-ring pressing plate of the O-ring sealing assembly; Step c, taking out the O-ring seat ring of the O-ring sealing assembly from the stuffing box hole; Step d: sequentially remove the second nickel wire flexible graphite braided packing part, the flexible graphite pressed packing part and the first nickel wire flexible graphite braided packing part to complete the disassembly of the valve shaft sealing structure of the ultra-low temperature ball valve.

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