A device for stem backseal activation seal replacement and method thereof

Abstract

The present application belongs to the technical field of valve seal replacement, and provides a device and method for replacing the seal of a valve stem reverse seal, wherein the device comprises a fixing mechanism, a pressure monitoring mechanism and a reverse seal activation mechanism, the fixing mechanism is used for fixing a target valve, and the pressure monitoring mechanism is sealingly connected with a port at one end of the target valve; the reverse seal activation mechanism comprises a support plate, a first activation assembly and a second activation assembly; the first activation assembly is installed on the support plate; the second activation assembly is located below the first activation assembly, one end of the second activation assembly is connected with the support plate, and the other end of the second activation assembly is connected with the fixing mechanism. The first activation assembly and the second activation assembly are provided, so that the first activation assembly and the second activation assembly can be alternately used when the seal of the target valve is replaced, the valve stem of the target valve is always lifted, and the state of reverse seal activation is maintained.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of valve seal replacement, and particularly relates to a device for replacing seal of valve stem reverse seal and a method thereof. BACKGROUND

[0002] Currently, the most widely used type of gate valve in oilfield wellhead devices (systems) is a flat gate valve, and the valve stem and the valve cover mainly rely on rubber seals for sealing. However, with the continuous advancement of unconventional oil and gas development in oilfields, new technologies such as carbon dioxide capture, utilization and storage (CCUS), carbon dioxide injection, etc. are implemented, and the injected medium or produced medium in the wellhead, such as carbon dioxide and hydrogen sulfide, has certain corrosiveness. Although the rubber seal is selected to a certain extent, the rubber seal between the valve stem and the valve cover of the flat gate valve will also be corroded, aged, and worn under complex working conditions, resulting in seal failure of the gate valve stem and causing leakage of the gate valve.

[0003] The traditional gate valve rubber seal is removed after the gate valve is disassembled, and the operation is performed in a non-pressurized state by disconnecting the connecting device. The rubber seal is removed by extraction tools, which has the following disadvantages: 1. It cannot be operated when the gate valve is connected to the system. 2. It cannot achieve the function of reverse seal excitation during the replacement of the gate valve seal. 3. It cannot achieve pressure monitoring and seal rubber replacement under pressure. SUMMARY

[0004] In order to solve the problems in the background art, the present application provides a device for replacing seal of valve stem reverse seal and a method thereof.

[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] A device for replacing seal of valve stem reverse seal, comprising a fixing mechanism, a pressure monitoring mechanism and a reverse seal excitation mechanism;

[0007] The fixing mechanism is used to fix the target valve, which is the valve whose seal is to be replaced;

[0008] The pressure monitoring mechanism is sealingly connected to the port at one end of the target valve, and is used to monitor the internal pressure of the target valve;

[0009] The reverse seal excitation mechanism comprises a support plate, a first excitation assembly and a second excitation assembly;

[0010] The first excitation assembly is installed on the support plate and is used to lift the valve stem of the target valve so that the valve stem is in a reverse seal excitation state;

[0011] The second excitation assembly is located below the first excitation assembly, one end is connected with the support plate, and the other end is connected with the fixing mechanism; the second excitation assembly is used to fix at the variable diameter of the valve rod after the valve rod is in the reverse sealing excitation state.

[0012] Preferably, the fixing mechanism comprises longitudinal connecting rods, connecting rod nuts, a fixed plate and transverse connecting rods.

[0013] The two longitudinal connecting rods and the two transverse connecting rods are connected end to end through the connecting rod nuts to form a rectangular frame; the two parallel rectangular frames are connected vertically through the fixed plate to form a cubic frame.

[0014] Preferably, the pressure monitoring mechanism comprises a needle pressure valve, a pressure short section, a stop valve and a pressure gauge.

[0015] The needle pressure valve is sealingly connected with the port of one end of the target valve.

[0016] The pressure short section is installed on the surface of the needle pressure valve.

[0017] The stop valve is installed at the end of the pressure short section away from the needle pressure valve.

[0018] The pressure gauge is installed on the surface of the stop valve for monitoring the internal pressure of the target valve.

[0019] Preferably, the first excitation assembly comprises a hand wheel, a pull rod, a pull rod nut, a T-shaped nut and a connecting frame.

[0020] One end of the pull rod is fixedly connected with the hand wheel, and the other end is threadedly connected with the pull rod nut.

[0021] The pull rod nut is fixed on the surface of the support plate.

[0022] The connecting frame is a ring frame structure, the top is clamped on the pull rod, and the bottom is used for clamping the T-shaped nut.

[0023] The T-shaped nut is threadedly connected with the valve rod.

[0024] Preferably, the support plate passes through the inside space of the connecting frame.

[0025] Preferably, the second excitation assembly comprises a support nut, a support rod, a valve rod positioning plate and a positioning nut.

[0026] The valve rod positioning plate is located below the support plate and is parallel to the support plate.

[0027] The support rods are fixed on the support plate through the support nut at one end and are threadedly connected with the positioning nut at the other end.

[0028] The valve stem positioning plate is slidably fitted with the support rod and is located between the support nut and the positioning nut;

[0029] The valve stem positioning plate mates with the valve stem at the diameter change point and locks the valve stem in place after abutting against the positioning nut.

[0030] Preferably, the valve stem positioning plate has a sliding hole and a locking hole on its surface;

[0031] The sliding hole is provided with a plurality of holes, and an opening is provided facing one side of the valve stem positioning plate;

[0032] The locking hole is a countersunk hole with an opening facing the same direction as the sliding hole; the upper part of the countersunk hole is rectangular and the lower part is U-shaped.

[0033] Preferably, at least one of the support nuts abuts against the upper surface of the support plate, and at least one of the support nuts abuts against the lower surface of the support plate;

[0034] The support rod is threadedly connected to all the support nuts, thereby fixing the support plate onto the support rod.

[0035] Preferably, the target valve includes a gate valve.

[0036] A replacement method for the aforementioned valve stem back seal activation seal replacement device includes the following steps:

[0037] The target valve is fixedly installed on the fixing mechanism;

[0038] The air pressure inside the target valve sealing gland is released by a pressure monitoring mechanism, and the air pressure inside the sealing gland is monitored until the air pressure inside the sealing gland meets the requirements.

[0039] The first activation component is connected to the valve stem of the target valve to put the valve stem in a reverse seal activation state;

[0040] The first set of parts for the target valve is proposed;

[0041] The second actuation assembly is fixed at the valve stem's diameter change point, replacing the first actuation assembly to put the valve stem in a reverse sealing state;

[0042] Disassemble the first set of parts of the target valve;

[0043] The first activation component is used to replace the second activation component, so that the valve stem is in the reverse sealing activation state;

[0044] The second set of parts for the target valve is proposed;

[0045] The second activation component is used to replace the first activation component, so that the valve stem is in the reverse sealing activation state;

[0046] Remove the second set of parts from the target valve;

[0047] The first excitation assembly replaces the second excitation assembly, and a new second set of parts is installed;

[0048] The second set of excitation components replaces the first set of excitation components, and the new first set of parts is installed.

[0049] Preferably, the first group of parts includes a valve cap, a valve stem nut, and a bearing; the second group of parts includes a packing gland, packing, and a gasket.

[0050] The beneficial effects of this invention are:

[0051] 1. The present invention provides a first excitation component and a second excitation component, so that when the target valve is changing its seal, the first excitation component and the second excitation component can be used alternately, so that the valve stem of the target valve is always raised and the reverse seal is kept in an excitation state.

[0052] 2. This invention includes a pressure monitoring component, which can monitor the internal pressure of the target valve under pressure, thereby providing data support for subsequent sealant replacement;

[0053] 3. The method of the present invention achieves a reverse sealing state of the valve stem by tightening it from the end of the valve stem through the first excitation component, and achieves a reverse sealing state of the valve stem by locking it at the diameter change of the valve stem through the second excitation component. The two excitation components are used alternately, so that the valve stem is always in a reverse sealing state when the seal of the target valve is replaced.

[0054] 4. The target valve of the present invention is in a system-connected state and has not been disconnected from the system, whereas in the traditional method, the target valve needs to be removed from the system.

[0055] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0056] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0057] Figure 1 A front view of a valve stem back seal activation seal replacement device according to the present invention is shown;

[0058] Figure 2 A side view of a valve stem back seal activation seal replacement device according to the present invention is shown;

[0059] Figure 3 A schematic diagram of the pressure monitoring mechanism of the present invention is shown;

[0060] Figure 4 A schematic diagram of the valve stem positioning plate of the present invention is shown;

[0061] Figure 5 A schematic diagram of the valve stem in reverse sealing state of the present invention is shown;

[0062] Figure 6 A schematic diagram of the target valve of the present invention being fixed by a fixing mechanism before the seal is replaced is shown;

[0063] Figure 7a A schematic diagram of the first excitation component of the present invention lifting the first group of parts is shown;

[0064] Figure 7b A schematic diagram of the second excitation assembly of the present invention replacing the first excitation assembly and disassembling the first group of parts is shown;

[0065] Figure 8a A schematic diagram of the first excitation component of the present invention lifting the second set of parts is shown;

[0066] Figure 8b A schematic diagram of the second excitation assembly of the present invention replacing the first excitation assembly and disassembling the second set of parts is shown;

[0067] Figure 9a This diagram shows the installation of the new second set of parts when the second excitation assembly is in operation;

[0068] Figure 9b This diagram shows the installation of the new second set of parts when the first excitation assembly replaces the second excitation assembly;

[0069] Figure 10 A flowchart of one replacement method of the present invention is shown.

[0070] In the diagram: 1. Longitudinal connecting rod; 2. Connecting rod nut; 3. Fixing plate; 4. Horizontal connecting rod; 5. Needle valve; 6. Pressure sub; 7. Shut-off valve; 8. Pressure gauge; 9. Handwheel; 10. Pull rod; 11. Support plate; 12. Pull rod nut; 13. Support nut; 14. T-nut; 15. Connecting bracket; 16. Support rod; 17. Valve stem positioning plate; 1701. Sliding hole; 1702. Locking hole; 18. Positioning nut; 19. Target valve; 1901. Valve stem; a. First group of parts; b. Second group of parts; c. New second group of parts. Detailed Implementation

[0071] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0072] A device for activating a valve stem back seal to replace a sealing element includes a fixing mechanism, a pressure monitoring mechanism, and a back seal activation mechanism. The fixing mechanism secures a target valve 19, which is the valve whose seal needs replacement. The pressure monitoring mechanism is connected to a port at one end of the target valve 19 in a sealed manner to monitor the internal pressure of the target valve 19.

[0073] In addition, the reverse seal activation mechanism includes a support plate 11, a first activation component, and a second activation component. The first activation component is mounted on the support plate 11 and is used to lift the valve stem 1901 of the target valve 19, so that the valve stem 1901 is in the reverse seal activation state. The second activation component is located below the first activation component, with one end connected to the support plate 11 and the other end connected to the fixing mechanism. The second activation component is used to fix the valve stem 1901 at the diameter change point after the valve stem 1901 is in the reverse seal activation state.

[0074] It should be noted that in the aforementioned target valve 19 (especially the gate valve), the back seal is an important sealing structure, mainly used to protect the valve stem 1901 and isolate the packing gland. Specifically, in conjunction with Figure 5 It can be seen that the valve stem 1901 is protected by the following seal: When the valve is fully open, the medium pressure pushes the valve stem 1901 upward, causing the reverse sealing surface on the valve stem 1901 to fit against the sealing surface of the valve cover (or valve cap), forming an auxiliary seal. The stuffing box is then isolated: At this time, the stuffing box (main seal) no longer bears the medium pressure, facilitating maintenance or replacement of the packing without depressurization.

[0075] It should be further explained that, when the above-mentioned sealing replacement device for valve stem 1901 back seal activation is in use, the first activation component and the second activation component can alternately maintain the target valve 19 in the back seal activation state so as to facilitate the replacement of parts in the target valve 19.

[0076] like Figure 1As shown, the fixing mechanism includes longitudinal connecting rods 1, connecting rod nuts 2, fixing plates 3, and transverse connecting rods 4. Two longitudinal connecting rods 1 and two transverse connecting rods 4 are connected end-to-end by connecting rod nuts 2, forming a rectangular frame; two parallel rectangular frames are perpendicularly connected by fixing plates 3 to their corresponding sides, forming a cubic frame. This frame-type fixing structure can securely clamp the target valve 19, ensuring that the target valve 19 remains stable throughout the entire process of replacing the seal, providing reliable support for the seal replacement operation.

[0077] like Figure 3 As shown, the pressure monitoring mechanism consists of a needle-type pressure valve 5, a pressure sub-section 6, a shut-off valve 7, and a pressure gauge 8. The needle-type pressure valve 5 is tightly fitted to one end of the target valve 19 via a sealing connection structure, ensuring the sealing and reliability of the pressure transmission path. The pressure sub-section 6 is installed on the surface of the needle-type pressure valve 5, with the two connected by threads, providing a mounting base and pressure transmission channel for subsequent components. The shut-off valve 7 is installed at the end of the pressure sub-section 6 furthest from the needle-type pressure valve 5, allowing flexible control of the pressure transmission on / off state. The pressure gauge 8 is installed on the surface of the shut-off valve 7, with the two connected by threads. This pressure gauge 8 can display the internal pressure data of the target valve 19 in real time and intuitively, providing operators with key parameter monitoring support and ensuring the accuracy and safety of pressure data during seal replacement.

[0078] Combination Figure 1 and Figure 2 It is known that the first actuation assembly includes a handwheel 9, a pull rod 10, a pull rod nut 12, a T-nut 14, and a connecting frame 15. One end of the pull rod 10 is fixedly connected to the handwheel 9, and the other end is threadedly connected to the pull rod nut 12. The pull rod nut 12 is welded to the surface of the support plate 11, and a threaded hole is also provided on the surface of the support plate 11 corresponding to the position of the pull rod nut 12, which can be threadedly engaged with the pull rod 10. The connecting frame 15 is a ring frame structure, with the top of the frame structure clamped onto the pull rod 10 and the bottom clamped onto the T-nut 14. The T-nut 14 is threadedly connected to the valve stem 1901.

[0079] In use, turning handwheel 9 will cause lever 10 to rotate synchronously. Figure 2 As can be seen, when the pull rod 10 moves upward axially, the connecting bracket 15, which is engaged with it, will rise synchronously. Because the bottom of the connecting bracket 15 forms a rigid constraint with the T-nut 14, its upward displacement will tighten the T-nut 14, causing the T-nut 14 to move upward axially along the valve stem 1901. As the T-nut 14 continues to move upward, the valve stem 1901 will be gradually lifted until the reverse sealing surface on the valve stem 1901 is completely in contact with the valve cover sealing seat, thereby causing the target valve 19 to enter the reverse sealing activation state.

[0080] Alternatively, the connection between the connecting bracket 15, the pull rod 10, and the T-nut 14 is as follows:

[0081] For example, Figure 2 A stepped structure is provided near the top of the tie rod 10. The connecting bracket 15 can be locked onto this stepped structure. When the tie rod 10 moves upward, the connecting bracket 15 is blocked by the stepped structure and thus moves upward with the tie rod 10. Similarly, the stepped structure of the T-nut 14 abuts against the bottom inner surface of the connecting bracket 15. When the connecting bracket 15 moves upward, the T-nut 14 moves together with the connecting bracket 15.

[0082] Optionally, the support plate 11 is designed to pass through the inner space of the connecting frame 15. This design effectively avoids the risk of motion interference between the connecting frame 15 and the support plate 11 by optimizing the component layout, thus ensuring the smoothness of the movement and the structural reliability of the first excitation component.

[0083] The second actuation assembly consists of a support nut 13, a support rod 16, a valve stem positioning plate 17, and a positioning nut 18. The valve stem positioning plate 17 is positioned parallel to the bottom of the support plate 11. Four support rods 16 are arranged in a rectangular array, with their top ends fastened to the support plate 11 via the support nut 13, and their bottom ends engaging with the positioning nut 18. The valve stem positioning plate 17 is slidably mounted on the support rod 16, and its axial displacement along the support rod 16 is limited between the support nut 13 and the positioning nut 18.

[0084] like Figure 4 As shown, both ends of the valve stem positioning plate 17 are provided with U-shaped sliding holes 1701 along the length direction. Each sliding hole has an opening facing the same side, forming a sliding fit interface with the support rod 16. In addition, the valve stem positioning plate 17 has a countersunk locking hole 1702 in the middle position, the opening direction of which is consistent with the sliding hole 1701. The upper part of the locking hole 1702 is rectangular and the lower part is U-shaped. During installation, first align the side opening of the sliding hole 1701 of the valve stem positioning plate 17 with the horizontally arranged support rod 16, and then slide it into the support rod 16 to form a sliding pair. At the same time, the locking hole 1702 is engaged with the diameter change of the valve stem 1901, which is generally a stepped structure.

[0085] Similarly, the locking groove 1702 can be disassembled and installed from one side of the valve stem 1901. The U-shaped groove can be locked at the diameter change of the valve stem 1901. Then, the valve stem 1901 can be locked by pressing the positioning nut 18 against the valve stem positioning plate 17.

[0086] To secure the valve stem 1901, another optional structure is as follows: a stepped fixing hole is provided in the central area of ​​the valve stem positioning plate 17. The inner diameter of this hole is adapted to the boss at the diameter change point of the valve stem 1901. Circumferential constraint and axial positioning of the valve stem 1901 are achieved through interference fit or key pin connection. This structural design ensures the relative freedom of movement between components and achieves efficient force transmission through precise dimensional chain control, providing structural assurance for the reliable activation of the valve's back-sealing function.

[0087] Alternatively, the connection between the support nut 13 and the support plate 11 can be as follows:

[0088] At least one support nut 13 abuts against the upper surface of the support plate 11, and at least one support nut 13 abuts against the lower surface of the support plate 11. A support rod 16 is threadedly connected to the support nut 13, thereby fixing the support rod 16 to the support plate 11. This embodiment does not limit the number of support nuts 13; for example, in… Figure 2 One of the support nuts 13 abuts against the upper surface of the support plate 11, and the other support nut 13 abuts against the lower surface of the support plate 11. The support rod 16 is threadedly connected to the two support nuts 13.

[0089] like Figure 10 The diagram illustrates a replacement method for a valve stem back seal activation seal replacement device described above, comprising the following steps:

[0090] S1: The target valve 19 is fixedly installed on the fixing mechanism. At this time, the target valve 19 is open and in a reverse sealing state.

[0091] S2: Release the air pressure in the sealing box of the target valve 19 through the pressure monitoring mechanism, and monitor the air pressure in the sealing box until the air pressure in the sealing box meets the requirements (the air pressure is zero and remains stable).

[0092] S3: Connect the first excitation assembly to the valve stem 1901 of the target valve 19, so that the valve stem 1901 is in the reverse sealing excitation state, and then remove the first set of parts a of the target valve 19;

[0093] S4: Fix the second actuation assembly at the diameter change of the valve stem 1901, replace the first actuation assembly to put the valve stem 1901 in a reverse sealing state, and then remove the first set of parts a of the target valve 19;

[0094] S5: Use the first activation component to replace the second activation component, so that the valve stem 1901 is in the reverse sealing activation state, and then remove the second set of parts b of the target valve 19;

[0095] S6: Use the second activation component to replace the first activation component, so that the valve stem 1901 is in the reverse sealing activation state; then remove the second set of parts b of the target valve 19.

[0096] S7: Replace the second excitation component with the first excitation component and install the new second set of parts c. Then replace the first set of excitation components with the second set of excitation components and install the new first set of parts a.

[0097] It should be noted that when the first excitation assembly replaces the second excitation assembly, the valve stem positioning plate 17 needs to be removed from the support rod 16, and the valve stem 1901 needs to be tightened using the T-nut 14. When the second excitation assembly replaces the first excitation assembly, the valve stem positioning plate 17 can be locked at the diameter change point of the valve stem 1901, and then the handwheel 9, pull rod 10, support plate 11, pull rod nut 12, and connecting bracket 15 can be removed. The reason for the replacement of the first and second excitation assemblies is that the first group of parts a or the second group of parts b will be blocked by the first excitation assembly during disassembly, thus requiring replacement from the second excitation assembly. The first excitation assembly mainly lifts the valve stem 1901 from the end, raising the first group of parts a or the second group of parts b to be disassembled above the second excitation assembly.

[0098] like Figure 6 As shown, when the target valve 19 is a gate valve, its lower end is fixed to the fixing mechanism, and the aforementioned needle-type pressure valve 5 is installed at one end of the port. A pressure spool 6, a stop valve 7, and a pressure gauge 8 are also installed. Then, the seals are replaced according to the process in steps S1-S7, specifically as follows: Figures 6-9b As shown.

[0099] Step 1: As Figure 6 As shown, the fixing mechanism consisting of the longitudinal connecting rod 1, the fixing plate 3, and the transverse connecting rod 4 is installed on the end flange of the gate valve by the connecting rod nut 2, which serves to support and fix the valve.

[0100] Step 2: Open the gate valve to make it in the upper seal position, then use the needle pressure valve 5 to connect to one end of the gate valve to release the residual pressure in the sealing box. After observing for a few minutes, if the pressure gauge 8 shows no pressure, it proves that the reverse seal is effective, and proceed to the next step.

[0101] Step 3: As Figure 7a As shown, remove the gate valve switch and valve cover, then install the first actuation mechanism. Use a T-nut 14 to connect the gate valve stem 1901. Then turn the handwheel 9 to pull the T-nut 14 upward to achieve the reverse sealing actuation effect. At the same time, lift the first set of parts a of the gate valve upward. The first set of parts a includes the valve cap, valve stem nut and bearing.

[0102] Step 4: Using the second actuation mechanism, the middle slot of the valve stem positioning plate 17 is locked with the valve stem 1901 at the diameter change point. Since the positioning nut 18 is threadedly connected to the support rod 16, rotating the positioning nut 18 pushes the valve stem positioning plate 17 upward to lock the valve stem 1901 of the gate valve, thus achieving the reverse sealing actuation effect. At this time, the second actuation component replaces the first actuation component to put the valve stem 1901 in the reverse sealing state (the handwheel 9, pull rod 10, support plate 11, and connecting bracket 15 are all disassembled). Then, the valve cap, valve stem nut, and bearing are removed.

[0103] Step 5: As Figure 8a As shown, the first excitation assembly replaces the second excitation assembly by loosening and removing the second set of parts b (reinstalling the handwheel 9, pull rod 10, support plate 11 and connecting bracket 15, etc., while removing the valve stem positioning plate 17). The second set of parts b includes the gate valve's packing gland, packing, and gasket.

[0104] Step 6: As Figure 8b As shown, the second excitation assembly is used to replace the first excitation assembly to put the valve stem 1901 in a reverse sealing state, and the packing gland, packing, and gasket are removed.

[0105] Step 7: As Figure 9a As shown, the first excitation assembly replaces the second excitation assembly when installing a new second set of parts c (such as gate valve packing), and then as follows: Figure 9b As shown, the second set of excitation components replaces the first set of excitation components, and the new second set of parts c is installed. Then, the method of alternating between the first and second excitation components is continued to install the valve cap, valve stem nut, bearing, gate valve switch, and valve cover.

[0106] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for replacing valve stem back seal activation seals, characterized in that, Includes a fixing mechanism, a pressure monitoring mechanism, and a reverse sealing activation mechanism; The fixing mechanism is used to fix the target valve (19), which is the valve whose seal is to be replaced; The pressure monitoring mechanism is sealed to one end of the target valve (19) and is used to monitor the internal pressure of the target valve (19); The inverted sealing excitation mechanism includes a support plate (11), a first excitation component, and a second excitation component; The first excitation assembly is mounted on the support plate (11) and is used to lift the valve stem (1901) of the target valve (19) so that the valve stem (1901) is in the reverse sealing excitation state. The first excitation assembly includes a handwheel (9), a pull rod (10), a pull rod nut (12), a T-nut (14), and a connecting frame (15). One end of the pull rod (10) is fixedly connected to the handwheel (9), and the other end is threadedly connected to the pull rod nut (12). The pull rod nut (12) is fixed to the surface of the support plate (11). The connecting frame (15) is a ring frame structure, with the top of the frame clamped on the pull rod (10) and the bottom of the frame clamped on the T-nut (14). The T-nut (14) is threadedly connected to the valve stem (1901). The second excitation component is located below the first excitation component, with one end connected to the support plate (11) and the other end connected to the fixing mechanism; the second excitation component is used to fix the valve stem (1901) at the diameter change point after the valve stem (1901) is in the reverse sealing excitation state; The second actuation assembly includes a support nut (13), a support rod (16), a valve stem positioning plate (17), and a positioning nut (18); The valve stem positioning plate (17) is located below the support plate (11) and parallel to the support plate (11); One end of several of the support rods (16) is fixed to the support plate (11) by a support nut (13), and the other end is threaded to a positioning nut (18); The valve stem positioning plate (17) is slidably fitted with the support rod (16) and is located between the support nut (13) and the positioning nut (18); The valve stem positioning plate (17) mates with the valve stem (1901) at the diameter change point and clamps the valve stem (1901) after abutting against the positioning nut (18).

2. The valve stem back seal activation sealing element replacement device according to claim 1, characterized in that, The fixing mechanism includes a longitudinal connecting rod (1), a connecting rod nut (2), a fixing plate (3), and a transverse connecting rod (4); Two longitudinal connecting rods (1) and two transverse connecting rods (4) are connected end to end by connecting rod nuts (2) to form a rectangular frame; two parallel rectangular frames are vertically connected to their corresponding sides by fixing plates (3) to form a cubic frame.

3. The device for replacing valve stem back seal activation seal as described in claim 1, characterized in that, The pressure monitoring mechanism includes a needle valve (5), a pressure spool (6), a shut-off valve (7), and a pressure gauge (8); The needle-type pressure valve (5) is sealed to one end of the target valve (19); The pressure stub (6) is mounted on the surface of the needle valve (5); The shut-off valve (7) is installed at the end of the pressure stub (6) away from the needle valve (5); The pressure gauge (8) is installed on the surface of the shut-off valve (7) to monitor the internal pressure of the target valve (19).

4. The device for replacing valve stem back seal activation seal as described in claim 1, characterized in that, The support plate (11) passes through the inner space of the connecting frame (15).

5. The valve stem back seal activation sealing element replacement device according to claim 1, characterized in that, The valve stem positioning plate (17) has a sliding hole (1701) and a locking hole (1702) on its surface; The sliding hole (1701) has several openings and is provided with an opening facing one side of the valve stem positioning plate (17); The locking hole (1702) is a countersunk hole and has an opening facing the same direction as the sliding hole (1701); the upper part of the countersunk hole is rectangular and the lower part is U-shaped.

6. The valve stem back seal activation sealing element replacement device according to claim 1, characterized in that, At least one of the support nuts (13) abuts against the upper surface of the support plate (11), and at least one of the support nuts (13) abuts against the lower surface of the support plate (11); The support rod (16) is threadedly connected to all the support nuts (13), thereby fixing the support plate (11) onto the support rod (16).

7. A valve stem back seal activation and seal replacement device according to any one of claims 1-6, characterized in that, The target valve (19) includes a gate valve.

8. A replacement method for a valve stem back seal activation seal replacement device as described in any one of claims 1-7, characterized in that, Includes the following steps: The target valve (19) is fixedly installed on the fixing mechanism; The air pressure in the sealing box of the target valve (19) is released by the pressure monitoring mechanism, and the air pressure in the sealing box is monitored until the air pressure in the sealing box meets the requirements. The first activation component is connected to the valve stem (1901) of the target valve (19) so that the valve stem (1901) is in the reverse sealing activation state; The first set of parts (a) of the target valve (19) is proposed; The second actuation assembly is fixed at the diameter change point of the valve stem (1901) to replace the first actuation assembly and put the valve stem (1901) in a reverse sealing state. Remove the first set of parts (a) of the target valve (19); The first activation component is used to replace the second activation component, so that the valve stem (1901) is in the reverse sealing activation state; The second set of parts (b) of the target valve (19) is proposed; The second activation component is used to replace the first activation component, so that the valve stem (1901) is in the reverse sealing activation state; Remove the second set of parts (b) of the target valve (19); The first excitation assembly replaces the second excitation assembly, and a new second set of parts (c) is installed. The second set of excitation components replaces the first set of excitation components, and the new first set of parts (a) is installed.

9. A replacement method according to claim 8, characterized in that, The first group of parts (a) includes a valve cap, a valve stem nut, and a bearing; The second group of parts (b) includes: packing gland, packing and gasket.

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