High sealing performance stop valve for ammonia working condition environment

Abstract

This invention relates to a high-sealing-performance shut-off valve for ammonia gas environments, belonging to the field of shut-off valve technology. It includes a valve body, a valve cover, a main valve disc, a secondary valve disc, and a drive mechanism. The valve body has an inlet, an outlet, and an installation port. A main sealing part and a secondary sealing part are integrally formed within the valve body. The main valve disc and the secondary valve disc are both located inside the valve body. The main valve disc abuts against the main sealing part to form a seal, and the secondary valve disc abuts against the secondary sealing part to form a seal. A pressure relief chamber is formed between the main valve disc and the secondary valve disc. The valve cover is fixedly mounted on the top of the valve body to seal the installation port. The drive mechanism is mounted on the valve body and drives the main valve disc and the secondary valve disc to open or close the pressure relief chamber. This invention can perform segmented pressure reduction of high-pressure liquid media, mitigating the damage to the internal seals of the shut-off valve caused by cavitation.

Description

Technical Field

[0001] This invention relates to the field of gate valve technology, and in particular to a gate valve with high sealing performance for use in ammonia gas environments. Background Technology

[0002] Gate valves are a common type of valve, mainly used to cut off or regulate the flow of fluids. Gate valves mainly consist of a valve body, valve cover, valve disc, valve stem, and valve seat. When a gate valve is working, the valve stem drives the valve disc to move and contact or separate from the valve seat, thereby cutting off the fluid or regulating the flow rate of the fluid through the valve. In the industrial production of ammonia, pressurized liquefaction storage of liquid ammonia is often used. Gate valves are usually used in the pipelines transporting liquid ammonia to cut off the flow and regulate the flow rate of liquid ammonia.

[0003] Currently, Chinese invention patent application CN119412511A, published on February 11, 2025, discloses a gate valve, including a valve body, a valve seat, a valve cover, and a valve stem. The valve body includes a first channel and a second channel that are interconnected. The valve seat is located at the connection between the first and second channels. Both the valve seat and the valve cover are detachably fitted to the valve body. The valve stem is slidably fitted to the valve cover, allowing the valve stem to move closer to or away from the valve seat. When the valve stem moves towards the valve seat, it can shut off the first and second channels. The detachable fit between the components of the gate valve disclosed in this application allows the valve seat to be removed for hard alloy welding, thereby improving the operating temperature and pressure of the gate valve and extending its service life.

[0004] However, when the gate valve is used in pipelines transporting easily vaporized liquids such as liquid ammonia, the internal liquid pressure of the gate valve is relatively high. When the gate valve is opened or closed or the flow is adjusted with a small opening, the pressure drops sharply when the liquid passes through the gate valve seal, which will cause cavitation on the valve disc and valve seat, damaging the sealing surface of the valve disc and valve seat. After long-term operation, the gate valve is prone to leakage. Summary of the Invention

[0005] To mitigate the damage to the internal seals of a gate valve caused by cavitation, this application provides a gate valve with high sealing performance for use in ammonia environments.

[0006] This invention provides a high-sealing-performance shut-off valve for ammonia working environments. The valve includes a valve body, a valve cover, a main valve disc, a secondary valve disc, and a drive mechanism. The valve body has an inlet, an outlet, and an installation port. A main sealing part and a secondary sealing part are integrally formed with the valve body. The main valve disc and the secondary valve disc are both located inside the valve body. The main valve disc abuts against the main sealing part to form a seal, and the secondary valve disc abuts against the secondary sealing part to form a seal. A pressure relief chamber is formed between the main valve disc and the secondary valve disc. The valve cover is fixedly mounted on the top of the valve body to seal the installation port. The drive mechanism is mounted on the valve body and is used to drive the main valve disc and the secondary valve disc to open or close the pressure relief chamber.

[0007] As can be seen from the above, in the initial state, the main valve disc and the auxiliary valve disc block the medium flowing in from the inlet, and the shut-off valve is in the closed state. When the shut-off valve is opened, the main valve disc and the auxiliary valve disc are controlled to move upward by the drive mechanism. The main valve disc and the auxiliary valve disc separate from the main sealing part and the auxiliary sealing part, respectively. The medium flows into the pressure relief chamber through the gap between the auxiliary valve disc and the auxiliary sealing part, and then flows into the outlet through the gap between the main valve disc and the main sealing part. In this process, the medium first undergoes a first pressure drop from the inlet to the pressure relief chamber and is buffered inside the pressure relief chamber. Then it undergoes a second pressure drop from the pressure relief chamber to the outlet. This can keep each pressure drop small, reduce cavitation caused by the large pressure drop of the medium on the main valve disc, the auxiliary valve disc, the main sealing part and the auxiliary sealing part, and ensure the sealing effect of the shut-off valve.

[0008] The technical solutions described above in this application embodiment have at least the following technical effects: by cooperating with the main valve disc and the auxiliary valve disc, the high-pressure liquid medium is depressurized in stages, reducing the damage of cavitation to the internal seal of the shut-off valve.

[0009] In some embodiments, the drive mechanism includes a main valve stem and a secondary valve stem. One end of the main valve stem passes through the valve cover and is fixedly connected to the side of the secondary valve disc away from the main valve disc. One end of the secondary valve stem is fixedly connected to the side of the secondary valve disc near the main valve disc, and the other end is drively connected to one side of the main valve disc.

[0010] In some embodiments, the drive mechanism further includes a pressure relief assembly, which includes a pressure relief cover and a pressure relief valve disc. The pressure relief cover is bolted to the side of the main valve disc near the secondary valve disc. A sliding groove is provided inside the pressure relief cover, and a first pressure relief hole is provided on the side of the pressure relief cover. A second pressure relief hole is provided on the main valve disc. The sliding groove, the first pressure relief hole, and the second pressure relief hole are interconnected. The pressure relief valve disc is slidably disposed inside the sliding groove and blocks the second pressure relief hole. The end of the secondary valve stem away from the secondary valve disc is fixedly connected to the pressure relief valve disc.

[0011] In some embodiments, a first sealing groove is provided on the secondary sealing part, and a first sealing ring and a first soft sealing ring are movably disposed inside the first sealing groove. One side of the first soft sealing ring abuts against the secondary sealing part, and the other side abuts against the first sealing ring. The first sealing ring abuts against the secondary valve disc to form a seal. A second sealing groove is provided on the side of the main valve disc near the secondary valve disc, and a second sealing ring and a second soft sealing ring are movably disposed inside the second sealing groove. One side of the second soft sealing ring abuts against the main valve disc, and the other side abuts against the second sealing ring. The second sealing ring abuts against the pressure relief valve disc to form a seal.

[0012] In some embodiments, a through hole is provided on the side of the pressure relief cover away from the main valve disc, and the slide groove communicates with the pressure relief chamber through the through hole.

[0013] In some embodiments, the drive mechanism further includes a guide assembly, which includes a guide shaft fixedly disposed inside the pressure relief chamber, and the main valve disc is slidably connected to the guide shaft.

[0014] In some embodiments, the guide assembly further includes a mating block, which is fixedly connected to the side of the main valve disc. The mating block has a mating groove and is slidably connected to the guide shaft through the mating groove.

[0015] In some embodiments, a bellows is fitted onto the main valve stem, one end of which is fixedly connected to the side of the valve cover near the secondary valve disc, and the other end is fixedly connected to the outer circumferential surface of the main valve stem.

[0016] In some embodiments, a packing groove is provided on the valve cover, and a sealing packing is provided inside the packing groove. The sealing packing abuts against the outer peripheral surface of the main valve stem. A pressure cap is bolted to the side of the valve cover away from the secondary valve disc. One end of the pressure cap is inserted into the packing groove and abuts against the sealing packing. The main valve stem passes through the pressure cap and is slidably connected to the pressure cap. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 A schematic diagram of the overall structure of a high-sealing-performance shut-off valve for ammonia working conditions provided in this application embodiment; Figure 2 A cross-sectional view of a high-sealing-performance shut-off valve for ammonia working conditions provided in an embodiment of this application; Figure 3 for Figure 2 Enlarged view of section A in the middle; Figure 4 for Figure 2 Enlarged view of section B; Figure 5 This is a schematic diagram showing the connection relationship between the auxiliary valve stem, the pressure relief cover, and the main valve disc.

[0019] The following are the labeling elements in the figure: 1. Valve body; 11. Inlet; 12. Outlet; 13. Mounting port; 14. Main sealing part; 15. Secondary sealing part; 151. First sealing groove; 152. First sealing ring; 153. First soft sealing ring; 16. Pressure relief chamber; 2. Valve cover; 21. Packing groove; 22. Sealing packing; 23. Gland; 3. Main valve disc; 31. Second pressure relief hole; 32. Second sealing groove; 33. Second sealing ring; 34. Second soft sealing ring; 4. Secondary valve disc; 51. Main valve stem; 52. Secondary valve stem; 61. Pressure relief cover; 611. Slide groove; 612. First pressure relief hole; 613. Through hole; 62. Pressure relief valve disc; 71. Guide shaft; 72. Mating block; 721. Mating groove; 8. Bellows. Detailed Implementation

[0020] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application. The terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0022] In the case of existing technologies, when gate valves are used in pipelines transporting easily vaporized liquids such as liquid ammonia, the internal liquid pressure of the gate valve is relatively high. When the gate valve is opened or closed or when the flow rate is adjusted to a small degree, the pressure drops sharply when the liquid passes through the sealing part of the gate valve, which will cause cavitation on the valve disc and valve seat, damaging the sealing surface of the valve disc and valve seat. After long-term operation, the gate valve is prone to leakage.

[0023] Based on this, in order to reduce the damage of cavitation to the internal seal of the shut-off valve, this application provides a shut-off valve with high sealing performance for ammonia working environment.

[0024] Please refer to the following: Figures 1 to 5This application provides a high-sealing-performance shut-off valve for ammonia working conditions. The high-sealing-performance shut-off valve for ammonia working conditions includes a valve body 1, a valve cover 2, a main valve disc 3, a secondary valve disc 4, and a drive mechanism. The valve body 1 has an inlet 11, an outlet 12, and an installation port 13. The valve body 1 is provided with a main sealing part 14 and a secondary sealing part 15, which are integrally formed with the valve body 1. The main valve disc 3 and the secondary valve disc 4 are both located inside the valve body 1. The main valve disc 3 abuts against the main sealing part 14 to form a seal, and the secondary valve disc 4 abuts against the secondary sealing part 15 to form a seal. A pressure relief chamber 16 is formed between the main valve disc 3 and the secondary valve disc 4. The valve cover 2 is fixedly installed on the top of the valve body 1 to block the installation port 13. The drive mechanism is installed on the valve body 1 to drive the main valve disc 3 and the secondary valve disc 4 to move and open or close the pressure relief chamber 16.

[0025] As can be seen from the above, in the initial state, the main valve disc 3 and the auxiliary valve disc 4 block the medium flowing into the inlet 11, and the valve is in the closed state. When the valve is opened, the main valve disc 3 and the auxiliary valve disc 4 are controlled to move upward by the drive mechanism. The main valve disc 3 and the auxiliary valve disc 4 separate from the main sealing part 14 and the auxiliary sealing part 15, respectively. The medium flows into the pressure relief chamber 16 through the gap between the auxiliary valve disc 4 and the auxiliary sealing part 15, and then flows into the outlet 12 through the gap between the main valve disc 3 and the main sealing part 14. In this process, the medium flows from the high-pressure inlet 11 to the pressure relief chamber 16 and experiences the first pressure drop, and then flows from the pressure relief chamber 16 to the outlet 12 and experiences the second pressure drop. This segmented pressure reduction design decomposes the huge pressure difference that the traditional single-stage sealing pair needs to withstand into two smaller pressure differences, so that the pressure drop amplitude in each throttling process is significantly reduced. This effectively suppresses the instantaneous vaporization of media such as liquid ammonia due to sudden pressure drops, preventing cavitation and the impact (i.e., cavitation phenomenon) on the sealing surfaces of the main valve disc 3, auxiliary valve disc 4, main sealing part 14, and auxiliary sealing part 15 when cavitation collapses. This significantly extends the service life of the sealing components and ensures the long-term sealing performance of the valve. Since both the main valve disc 3 and auxiliary valve disc 4 can independently cut off the medium, even if leakage occurs at one of them, the other can still cut off the medium to prevent further leakage, further improving the valve's sealing performance.

[0026] In some embodiments, please refer to the following: Figures 2 to 5In the basic scheme described above in this application, although segmented pressure reduction is achieved through a dual-valve structure, the key to ensuring the functionality of this structure lies in how to achieve the linkage drive of the main valve 3 and the auxiliary valve 4, and ensure their motion synchronization and reliability. To this end, this application further proposes a specific configuration of the drive mechanism. The drive mechanism includes a main valve stem 51 and an auxiliary valve stem 52. One end of the main valve stem 51 passes through the valve cover 2 and is fixedly connected to the side of the auxiliary valve 4 away from the main valve 3. One end of the auxiliary valve stem 52 is fixedly connected to the side of the auxiliary valve 4 near the main valve 3, and the other end is drively connected to the side of the main valve 3.

[0027] With this configuration, when installing the valve, the end of the main valve stem 51 located outside the valve is connected to the external operating mechanism. When the valve needs to be opened, the operating mechanism drives the main valve stem 51 to move upward and moves the secondary valve disc 4 upward. The secondary valve disc 4 then drives the main valve disc 3 to move upward through the secondary valve stem 52, thereby opening the valve. Similarly, the operating mechanism can control the main valve stem 51 to move downward to close the valve.

[0028] Optionally, in some embodiments, reference is made to Figures 2 to 5 In the embodiments described above in this application, the synchronous opening and closing of the valve disc is achieved through the linkage of the main valve stem and the auxiliary valve stem. However, under high-pressure conditions, after the valve is closed, the high-pressure medium accumulated in the pressure relief chamber 16 will exert a very large clamping force on the main valve disc 3. Although this helps to enhance the seal, it also results in a large valve stem thrust required at the moment of valve opening, making operation difficult and placing high demands on the drive components. To solve the problem of "difficulty in opening" the valve under high pressure, this application integrates a pressure relief component into the drive mechanism. Specifically, the pressure relief assembly includes a pressure relief cover 61 and a pressure relief valve disc 62. The pressure relief cover 61 is bolted to the side of the main valve disc 3 near the auxiliary valve disc 4. The pressure relief cover 61 has a sliding groove 611 inside and a first pressure relief hole 612 on the side of the pressure relief cover 61. The main valve disc 3 has a second pressure relief hole 31. The sliding groove 611, the first pressure relief hole 612 and the second pressure relief hole 31 are interconnected. The pressure relief valve disc 62 is slidably disposed inside the sliding groove 611 and blocks the second pressure relief hole 31. The end of the auxiliary valve stem 52 away from the auxiliary valve disc 4 is fixedly connected to the pressure relief valve disc 62.

[0029] With this configuration, when high-pressure media such as liquid ammonia flow inside the valve, after the valve is closed, the main valve disc 3 abuts against the main sealing part 14 to cut off the medium. A large pressure difference will be formed between the pressure relief chamber 16 and the outlet 12. The high-pressure medium inside the pressure relief chamber 16 applies additional pressure to the main valve disc 3, pressing it tightly against the main sealing part 14, which can enhance the sealing performance between the main valve disc 3 and the main sealing part 14. However, when the valve is opened, this pressure will increase the valve stem thrust when the valve is opened, making it difficult to open the valve. When the valve is opened, the main valve stem 51 first drives the auxiliary valve disc 4 to rise a small stroke. The auxiliary valve disc 4 drives the pressure relief valve disc 62 to slide upward in the slide groove 611 through the auxiliary valve stem 52, so that the second pressure relief hole 31 is opened. At this time, the high-pressure medium inside the pressure relief chamber 16 can quickly flow to the lower-pressure outlet 12 side through the pressure relief channel formed by the first pressure relief hole 612, the slide groove 611, and the second pressure relief hole 31, thereby rapidly reducing the pressure inside the pressure relief chamber 16 and significantly reducing the pressure difference with the outlet 12 side. Subsequently, the main valve stem 51 continues to move upward. Since the diameter of the pressure relief valve disc 62 is larger than that of the auxiliary valve stem 52, its top surface will contact the top of the slide groove 611 inside the pressure relief cover 61, thereby driving the entire pressure relief cover 61 and the main valve disc 3 connected to it to move upward together, realizing the opening of the main seal, thus realizing the linkage drive of the main valve disc 3 and the auxiliary valve disc 4. In this process, by first depressurizing and then opening the main valve, the valve stem thrust required in the initial stage of valve opening is greatly reduced, making the valve opening operation under high pressure conditions easier and less strenuous.

[0030] Optionally, in some embodiments, reference is made to Figures 2 to 4 The introduction of pressure relief components has solved the problem of high-pressure opening, but after long-term use, minor wear or machining and assembly errors in various sealing components may affect the absolute reliability of the seal. To compensate for these unavoidable deviations and ensure that all sealing contact surfaces fit tightly, this application has implemented a unique floating seal design for critical sealing parts.

[0031] Specifically, the secondary sealing part 15 is provided with a first sealing groove 151. A first sealing ring 152 and a first soft sealing ring 153 are movably disposed inside the first sealing groove 151. One side of the first soft sealing ring 153 abuts against the secondary sealing part 15, and the other side abuts against the first sealing ring 152. The first sealing ring 152 abuts against the secondary valve disc 4 to form a seal. A second sealing groove 32 is provided on the side of the main valve disc 3 near the secondary valve disc 4. A second sealing ring 33 and a second soft sealing ring 34 are movably disposed inside the second sealing groove 32. One side of the second soft sealing ring 34 abuts against the main valve disc 3, and the other side abuts against the second sealing ring 33. The second sealing ring 33 abuts against the pressure relief valve disc 62 to form a seal.

[0032] With this configuration, when the valve is closed, the main valve stem 51 is driven downward, and the secondary valve disc 4, the pressure relief valve disc 62, and the main valve disc 3 all move downward. The main valve disc 3 will first contact the main sealing part 14 and stop moving. The secondary valve disc 4 and the pressure relief valve disc 62 continue to move downward. The pressure relief valve disc 62 moves downward relative to the slide groove 611 inside the slide groove 611. At the same time, the pressure relief valve disc 62 contacts the second sealing ring 33, and the secondary valve disc 4 contacts the first sealing ring 152. Then, both continue to move downward. The pressure relief valve disc 62 presses against the second sealing ring 33 and compresses the second soft sealing ring 34. The main valve disc... 3. Under the pressure of the medium inside the pressure relief valve disc 62 and the pressure relief chamber 16, the valve disc 4 is pressed against the main sealing part 14. The auxiliary valve disc 4 is pressed against the first sealing ring 152 and the first soft sealing ring 153 is compressed, thus closing the valve. During this process, the positions of the first soft sealing ring 152 and the second soft sealing ring 34 are allowed to fluctuate to a certain extent, which compensates for the errors in the production and installation of various parts of the valve, and ensures that the main valve disc 3, the auxiliary valve disc 4 and the pressure relief valve disc 62 can form a reliable seal.

[0033] Optionally, in some embodiments, please refer to Figure 3 and Figure 5 In the embodiments described above in this application, the slide groove 611 of the pressure relief assembly needs to maintain dynamic pressure balance with the pressure relief chamber 16 to ensure smooth operation of the pressure relief valve disc 62 and enhance sealing using the medium pressure. Therefore, furthermore, a through hole 613 is provided on the side of the pressure relief cover 61 away from the main valve disc 3, and the slide groove 611 communicates with the pressure relief chamber 16 through the through hole 613.

[0034] With this configuration, the through hole 613 keeps the interior of the slide groove 611 connected to the pressure relief chamber 16. When the valve is opened, the pressure relief valve disc 62 moves upward relative to the slide groove 611, discharging the medium inside the slide groove 611 into the pressure relief chamber 16, ensuring that the pressure relief valve disc 62 slides smoothly within the slide groove 611. When the valve is closed, the medium inside the pressure relief chamber 16 can flow into the slide groove 611 through the through hole 613 and apply pressure to the top of the pressure relief valve disc 62, enhancing the sealing performance of the pressure relief valve disc 62.

[0035] Optionally, in some embodiments, please refer to Figures 2 to 5 The drive mechanism also includes a guide assembly, which includes a guide shaft 71. The guide shaft 71 is fixedly installed inside the pressure relief chamber 16, and the main valve disc 3 is slidably connected to the guide shaft 71.

[0036] With this configuration, when the drive mechanism drives the main valve disc 3 to move, the guide shaft 71 can guide the movement of the main valve disc 3, so that the main valve disc 3 always moves along the axial direction of the main valve stem 51, avoiding the main valve disc 3 and the main sealing part 14 not being able to form an effective seal due to the positional deviation of the main valve disc 3.

[0037] Optionally, in some embodiments, please refer to Figure 5 The guide assembly also includes a mating block 72, which is fixedly connected to the side of the main valve disc 3. The mating block 72 has a mating groove 721, and the mating block 72 is slidably connected to the guide shaft 71 through the mating groove 721.

[0038] With this configuration, when the main valve disc 3 moves, the mating block 72 can slide relative to the guide shaft 71. The guide shaft 71 and the mating groove 721 cooperate to guide and limit the mating block 72 and the main valve disc 3. When disassembling the main valve disc 3, the valve stem is removed from the valve body 1, and then the auxiliary valve disc 4, auxiliary valve stem 52 and main valve disc 3 are pulled out from the mounting port 13 through the main valve stem 51. When installing the main valve disc 3, the main valve disc 3 is placed into the pressure relief chamber 16 through the mounting port 13 and each mating block 72 is engaged with the guide shaft 71.

[0039] Optionally, in some embodiments, please refer to Figure 2 As a key component of dynamic sealing, the main valve stem 51's sealing reliability directly affects whether the valve leaks externally. Therefore, a bellows 8 is further fitted onto the main valve stem 51. One end of the bellows 8 is fixedly connected to the side of the valve cover 2 near the secondary valve disc 4, and the other end is fixedly connected to the outer circumferential surface of the main valve stem 51.

[0040] In this configuration, the bellows 8 forms the first dynamic sealing barrier of the main valve stem 51. Its metal bellows structure can elastically expand and contract as the main valve stem 51 moves up and down, always completely isolating the medium inside the valve cavity from the external environment. This packingless sealing method reduces the risk of leakage caused by wear and aging of traditional packing seals, making it suitable for harsh operating conditions such as ammonia.

[0041] Optionally, in some embodiments, please refer to Figure 2 The valve cover 2 has a packing groove 21, and a sealing packing 22 is provided inside the packing groove 21. The sealing packing 22 abuts against the outer peripheral surface of the main valve stem 51. A pressure cap 23 is bolted to the side of the valve cover 2 away from the secondary valve disc 4. One end of the pressure cap 23 is inserted into the packing groove 21 and abuts against the sealing packing 22. The main valve stem 51 passes through the pressure cap 23 and is slidably connected to the pressure cap 23.

[0042] With this configuration, the gland 23 applies greater pressure to the top of the sealing packing 22, causing the sealing packing 22 to come into tight contact with the outer circumferential surface of the main valve stem 51 and the valve body 1 to form a seal, further enhancing the sealing performance at the connection between the main valve stem 51 and the valve cover 2.

[0043] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A high sealing performance stop valve for an ammonia service environment, characterized by: The valve includes a valve body (1), a valve cover (2), a main valve disc (3), a secondary valve disc (4), and a drive mechanism. The valve body (1) has an inlet (11), an outlet (12), and a mounting port (13). The valve body (1) has a main sealing part (14) and a secondary sealing part (15) inside. The main sealing part (14) and the secondary sealing part (15) are integrally formed with the valve body (1). The main valve disc (3) and the secondary valve disc (4) are both located on the valve body (1). Inside, the main valve disc (3) abuts against the main sealing part (14) to form a seal, the secondary valve disc (4) abuts against the secondary sealing part (15) to form a seal, and a pressure relief chamber (16) is formed between the main valve disc (3) and the secondary valve disc (4). The valve cover (2) is fixedly installed on the top of the valve body (1) to block the installation port (13). The drive mechanism is installed on the valve body (1) to drive the main valve disc (3) and the secondary valve disc (4) to move so that the pressure relief chamber (16) opens or closes.

2. The high sealing performance stop valve for ammonia service according to claim 1, characterized in that: The drive mechanism includes a main valve stem (51) and a secondary valve stem (52). One end of the main valve stem (51) passes through the valve cover (2) and is fixedly connected to the side of the secondary valve disc (4) away from the main valve disc (3). One end of the secondary valve stem (52) is fixedly connected to the side of the secondary valve disc (4) close to the main valve disc (3), and the other end is drivenly connected to the side of the main valve disc (3).

3. The high sealing performance stop valve for ammonia service according to claim 2, characterized in that: The drive mechanism also includes a pressure relief assembly, which includes a pressure relief cover (61) and a pressure relief valve (62). The pressure relief cover (61) is bolted to the side of the main valve (3) near the secondary valve (4). The pressure relief cover (61) has a sliding groove (611) inside. The side of the pressure relief cover (61) also has a first pressure relief hole (612). The main valve (3) has a second pressure relief hole (31). The sliding groove (611), the first pressure relief hole (612) and the second pressure relief hole (31) are interconnected. The pressure relief valve (62) is slidably disposed inside the sliding groove (611) and blocks the second pressure relief hole (31). The end of the secondary valve stem (52) away from the secondary valve (4) is fixedly connected to the pressure relief valve (62).

4. The high-sealing-performance shut-off valve for ammonia working conditions according to claim 3, characterized in that: The secondary sealing part (15) is provided with a first sealing groove (151). The first sealing groove (151) is movably provided with a first sealing ring (152) and a first soft sealing ring (153). One side of the first soft sealing ring (153) abuts against the secondary sealing part (15) and the other side abuts against the first sealing ring (152). The first sealing ring (152) abuts against the secondary valve disc (4) to form a seal. The main valve disc (3) is provided with a second sealing groove (32) on the side near the secondary valve disc (4). The second sealing groove (32) is movably provided with a second sealing ring (33) and a second soft sealing ring (34). One side of the second soft sealing ring (34) abuts against the main valve disc (3) and the other side abuts against the second sealing ring (33). The second sealing ring (33) abuts against the pressure relief valve disc (62) to form a seal.

5. A high-sealing-performance shut-off valve for ammonia working conditions according to claim 3, characterized in that: The pressure relief cover (61) has a through hole (613) on the side away from the main valve disc (3), and the slide groove (611) is connected to the pressure relief chamber (16) through the through hole (613).

6. A high-sealing-performance shut-off valve for ammonia working conditions according to claim 2, characterized in that: The drive mechanism also includes a guide assembly, which includes a guide shaft (71) fixedly disposed inside the pressure relief chamber (16), and the main valve disc (3) is slidably connected to the guide shaft (71).

7. A high-sealing-performance shut-off valve for ammonia working conditions according to claim 6, characterized in that: The guide assembly also includes a mating block (72), which is fixedly connected to the side of the main valve disc (3). The mating block (72) has a mating groove (721) and is slidably connected to the guide shaft (71) through the mating groove (721).

8. A high-sealing-performance shut-off valve for ammonia working conditions according to claim 2, characterized in that: A bellows (8) is fitted on the main valve stem (51). One end of the bellows (8) is fixedly connected to the side of the valve cover (2) near the secondary valve disc (4), and the other end is fixedly connected to the outer circumferential surface of the main valve stem (51).

9. A high-sealing-performance shut-off valve for ammonia working conditions according to claim 8, characterized in that: The valve cover (2) is provided with a packing groove (21), and a sealing packing (22) is provided inside the packing groove (21). The sealing packing (22) abuts against the outer circumferential surface of the main valve stem (51). A pressure cap (23) is bolted to the side of the valve cover (2) away from the secondary valve disc (4). One end of the pressure cap (23) is inserted into the packing groove (21) and abuts against the sealing packing (22). The main valve stem (51) passes through the pressure cap (23) and is slidably connected to the pressure cap (23).

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