Online repairing method for connection failure of valve rod and valve plate in gate valve

Abstract

The invention provides an online repairing method for connection failure of a valve rod and a valve plate in a gate valve. The online repairing method comprises the steps that the valve rod is moved to drive the valve plate to move to a sealing face in a valve seat; separating the valve cover, the valve rod and the valve seat to expose the valve plate; the valve rod and the valve plate are connected through one of welding, bonding and threaded connection; and the valve deck is installed on the valve seat, and repairing is completed. According to the online repair method for the connection failure of the valve rod and the valve plate in the gate valve, rapid repair can be conducted under the condition that a pipeline system is under pressure, repair modes can be selected according to different conditions, and the repair efficiency and the success rate are greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of gate valves, and in particular to an online repair method for failure of connection between a valve stem and a valve plate in a gate valve. Background Art

[0002] In fluid control systems, gate valves are used as key cutoff and regulating components and are widely used in various pressure and medium pipeline systems. However, during use, gate valves often experience problems with the connection between the valve stem and the valve plate, which affects the sealing and opening and closing functions of the gate valve. In severe cases, it may even cause fluid leakage, posing a major threat to production safety, environmental protection and personnel safety. Summary of the invention

[0003] The present invention is based on the inventor's discovery and understanding of the following facts and problems:

[0004] A gate valve is a valve in which the valve stem drives the valve plate to move up and down along the valve seat sealing surface to achieve the circulation and control of the medium and the regulation of the medium pressure and flow rate. In the relevant technology, a bayonet connection design is often used between the valve plate and the valve stem, such as the T-shaped head of the valve stem matching the T-shaped slot on the valve plate. However, this connection method may cause connection failure when faced with challenges such as insufficient processing accuracy, excessive clearance, long-term wear or corrosion, which is specifically manifested as loosening or even falling off between the T-shaped head and the T-shaped slot, which in turn causes the gate valve to malfunction.

[0005] In addition, in the daily operation of the gate valve, improper operation, such as excessive force, may also cause the valve plate to get stuck or damage the connection between the valve stem and the valve plate, further increasing the risk of connection failure. Once the valve stem and valve plate fall off, the traditional treatment method often requires the gate valve to be removed from the pipeline system for replacement. For some pipeline systems that are at high pressure, difficult to close or in critical positions, not only is the operation complicated and costly, but it may also seriously interfere with or even interrupt the normal operation of the system.

[0006] To this end, an embodiment of the present invention provides an online repair method for failure of connection between a valve stem and a valve plate in a gate valve, which comprises the following steps:

[0007] Move the valve stem to drive the valve plate to move to the sealing surface in the valve seat;

[0008] Separating the valve cover, the valve stem and the valve seat to expose the valve plate;

[0009] Connecting the valve stem and the valve plate by one of welding, bonding and threading;

[0010] The valve cover is installed to the valve seat to complete the repair.

[0011] In summary, the online repair method for the failure of the connection between the valve stem and the valve plate in the gate valve provided by the embodiment of the present invention can not only perform rapid repairs when the pipeline system is under pressure, but also select corresponding repair methods according to different situations, thereby greatly improving the repair efficiency and success rate.

[0012] In some embodiments, the step of moving the valve stem to drive the valve plate to move to the sealing surface in the valve seat includes:

[0013] Turn the hand wheel to make the valve stem push against the valve plate and move to the sealing surface of the valve seat;

[0014] Loosen the connecting bolts between the valve cover and the valve seat, and check and detect the sealing between the valve plate and the valve seat.

[0015] In some embodiments, the step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection includes the steps of:

[0016] Drilling and tapping a threaded hole in a central area of ​​the top of the valve plate;

[0017] Processing a threaded section on the valve stem to match the threaded hole;

[0018] The valve stem and the valve plate are connected by tightening the threaded section and the threaded hole.

[0019] In some embodiments, the step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection includes the steps of:

[0020] After the threaded section of the valve stem is screwed into the threaded hole of the valve plate, the valve stem is subjected to torque detection.

[0021] In some embodiments, the step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection includes the steps of:

[0022] The valve stem and the valve plate are preheated.

[0023] In some embodiments, the step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection includes the steps of:

[0024] Obtaining the type of medium flowing through the gate valve;

[0025] Determine the adhesive according to the medium type;

[0026] Obtain the temperature and humidity of the environment where the valve seat is located and the temperature of the valve seat itself;

[0027] Determine the preset curing time of the adhesive based on the ambient temperature and humidity and the temperature of the valve seat itself;

[0028] Adhesive is applied to the valve stem and the valve seat until the curing time of the adhesive reaches a preset curing time.

[0029] In some embodiments, the step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection includes the steps of:

[0030] Processing the top of the valve plate to form a groove;

[0031] Processing the valve stem to form a clamping column matching the clamping groove;

[0032] The clamping column is clamped into the clamping slot.

[0033] In some embodiments, before the step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection, the method further includes: pre-treating the connection surfaces of the valve stem and the valve plate to remove impurities and an oxide layer.

[0034] In some embodiments, after the step of connecting the valve stem and the valve plate by one of welding, bonding and threading, the method further comprises:

[0035] The valve stem, valve plate and corresponding connection parts are subjected to ultrasonic testing or magnetic particle testing.

[0036] In some embodiments, the step of installing the valve cover to the valve seat includes:

[0037] Clean and inspect the corresponding mounting surfaces of the valve cover and the valve seat, and apply sealing grease. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 It is a flow chart of an online repair method for a failed connection between a valve stem and a valve plate in a gate valve provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0039] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0040] like Figure 1 As shown, an embodiment of the present invention provides an online repair method for failure of connection between a valve stem and a valve plate in a gate valve, which comprises the following steps:

[0041] S10, moving the valve stem to drive the valve plate to move to the sealing surface in the valve seat.

[0042] In this step, it is necessary to ensure that the valve plate fits tightly against the sealing surface inside the valve seat and that the gate valve is in a closed state to avoid a large amount of media overflowing during the repair process and affecting the repair process.

[0043] S20, separating the valve cover, the valve stem and the valve seat to expose the valve plate.

[0044] In this step, tools are used to gradually disassemble the valve cover and valve stem. After the valve cover is removed, the connection between the valve stem and the valve plate is completely exposed to facilitate the subsequent repair process.

[0045] S30, connecting the valve stem and the valve plate by one of welding, bonding and threaded connection.

[0046] That is to say, the connection between the valve stem and the valve plate can be achieved by one of welding, bonding and threaded connection. In this embodiment, when the medium to be circulated by the gate valve is water, wind or steam, welding can be used. However, when the medium to be circulated by the gate valve is oil or gas, bonding or threaded connection can be used to avoid sparks generated by welding affecting production safety.

[0047] S40, installing the valve cover to the valve seat, and completing the repair.

[0048] That is, after the valve stem and valve plate are reconnected and cured, the valve cover needs to be reinstalled on the valve seat. During the installation process, it is necessary to ensure that all fasteners are tightened evenly to avoid the valve cover from tilting and causing a poor seal.

[0049] In summary, the online repair method for the failed connection between the valve stem and the valve plate in the gate valve provided by the embodiment of the present invention can not only perform rapid repairs when the pipeline system is under pressure, but also flexibly select the repair method according to different situations, greatly improving the repair efficiency and success rate. At the same time, the method also effectively reduces maintenance costs and time costs, prolongs the service life of the equipment, and provides a strong guarantee for the continuity and stability of industrial production.

[0050] In some embodiments, the step of moving the valve stem to drive the valve plate to move to the sealing surface in the valve seat includes:

[0051] Turn the hand wheel to make the valve stem push against the valve plate and move to the sealing surface of the valve seat;

[0052] Loosen the connecting bolts between the valve cover and the valve seat, and check and detect the sealing between the valve plate and the valve seat.

[0053] Specifically, when the connection between the valve stem and the valve plate fails, that is, the connection between the valve stem and the valve plate is broken, the valve stem can still be moved by turning the hand wheel, so that the valve stem pushes against the valve plate to move the valve plate to the sealing surface of the valve seat, ensuring that the gap between the valve plate and the sealing surface of the valve seat gradually decreases until the optimal sealing state is achieved.

[0054] Then loosen the connecting bolts between the valve cover and the valve seat, observe whether there is any medium overflowing from the gap between the valve cover and the valve seat, and evaluate the amount of overflow. If only a small amount of stable medium overflow occurs, and this situation does not affect the subsequent repair process and safe operation, then it can be considered that the sealing basically meets the requirements and the next step can be performed. However, if it is found that the medium overflow flow is large or there is a trend of continuous increase, the operation should be stopped immediately and the loosened connecting bolts should be tightened quickly to restore the original sealing state.

[0055] In some embodiments, the step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection includes the steps of:

[0056] Drilling and tapping a threaded hole in a central area of ​​the top of the valve plate;

[0057] Processing a threaded section on the valve stem to match the threaded hole;

[0058] The valve stem and the valve plate are connected by tightening the threaded section and the threaded hole.

[0059] Specifically, the position of the drill hole is measured and marked in the center area of ​​the top of the valve plate to ensure the accuracy of the drill hole position, to ensure that the valve stem is perpendicular to the mounting surface on the valve seat and that the valve stem is centered, to avoid the situation where the valve cover and other components on the valve cover cannot be installed normally after the valve stem is installed.

[0060] In some embodiments, the step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection also includes the step of performing torque detection on the valve stem after the threaded section of the valve stem is screwed into the threaded hole of the valve plate.

[0061] Specifically, after the threaded section of the valve stem is smoothly screwed into the threaded hole of the valve plate, a torque wrench or other torque detection equipment can be used to accurately detect the torque of the valve stem, so as to verify whether the connection between the valve stem and the valve plate has reached the expected tightness. If the test result shows that the torque value is lower than the set value, it means that the connection may not be tight enough, and there is a risk of loosening or reconnection failure. At this time, the valve stem needs to be re-tightened until the specified torque value is reached. On the contrary, if the torque value is too high, although the connection seems to be stable, it may cause unnecessary stress concentration or damage to the valve stem, threaded hole or the entire valve structure. Therefore, it is also necessary to adjust it to ensure that the torque value is within a reasonable range. Through the implementation of this step, not only can the stability and reliability of the connection between the valve stem and the valve plate be effectively improved, but also potential connection problems can be discovered and corrected in a timely manner to avoid unnecessary failures and losses during subsequent use.

[0062] In some embodiments, the step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection includes the step of preheating the valve stem and the valve plate when welding is used. The preheating treatment is to heat the welded parts to a certain temperature range to improve the structure and performance of the welded joint. For metal materials such as valve stems and valve plates, preheating can significantly reduce thermal stress during welding and reduce the temperature difference between the welding area and the surrounding materials, thereby avoiding the generation of welding cracks. At the same time, preheating can also improve the plasticity and toughness of the welding material, making the welded joint more firm and reliable.

[0063] When preheating, it is necessary to determine the appropriate preheating temperature and time based on factors such as the material, thickness, welding method, and ambient temperature of the valve stem and valve plate. Generally speaking, the preheating temperature should be selected so that the temperature of the welding area is slightly higher than the critical transition temperature of the material, but not too high to avoid overheating and burning of the material. The preheating time should be determined based on the thermal conductivity of the material and the preheating temperature to ensure that the welding area achieves a uniform preheating effect.

[0064] In some embodiments, the step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection includes the steps of:

[0065] Obtaining the type of medium flowing through the gate valve;

[0066] Determine the adhesive according to the medium type;

[0067] Obtain the temperature and humidity of the environment where the valve seat is located and the temperature of the valve seat itself;

[0068] Determine the preset curing time of the adhesive based on the ambient temperature and humidity and the temperature of the valve seat itself;

[0069] Adhesive is applied to the valve stem and the valve seat until the curing time of the adhesive reaches a preset curing time.

[0070] Specifically, first of all, it is a critical first step to clearly understand the type of media that the gate valve flows through. Different media may have different effects on adhesives, including accelerated aging, reduced bonding strength, or chemical reactions. Therefore, it is necessary to determine the most suitable adhesive according to the type of media.

[0071] Next, obtain the temperature and humidity data of the environment where the valve seat is located and the temperature of the valve seat itself. The temperature and humidity of the environment not only affect the curing speed of the adhesive, but may also affect its performance after curing. The temperature of the valve seat itself is directly related to the temperature of the bonding interface. Too high a temperature may cause the adhesive to fail prematurely, while too low a temperature may prolong the curing time and even affect the curing quality. Therefore, these data can be monitored and recorded in real time to provide an accurate basis for subsequent bonding operations.

[0072] Based on the above environmental conditions and valve seat temperature data, the preset curing time of the adhesive will be calculated or estimated to ensure that the adhesive can complete the curing process under optimal conditions and achieve the expected bonding strength and durability.

[0073] Finally, after ensuring that all preparations are in place, an appropriate amount of adhesive is evenly applied to the valve stem and valve disc. During the application process, care should be taken to avoid the generation of bubbles and gaps to ensure full contact and uniform coverage of the bonding surface. Subsequently, the valve stem and valve disc are precisely aligned and appropriate pressure is applied to promote uniform distribution and rapid curing of the adhesive. During the entire curing process, the ambient temperature and humidity must be strictly controlled. If necessary, measures such as heating or humidification can be taken to accelerate or optimize the curing process. When the curing time reaches the preset value, the bonding operation is completed, and a strong and reliable connection will be formed between the valve stem and the valve seat.

[0074] In some embodiments, the step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection includes the steps of:

[0075] Processing the top of the valve plate to form a groove;

[0076] Processing the valve stem to form a clamping column matching the first groove;

[0077] The clamping column is clamped into the clamping slot.

[0078] Specifically, first, the top of the valve plate is processed to form a slot. At the same time, the valve stem is processed accordingly to form a post that matches the slot. The shape, size and material of the post must strictly correspond to the slot to ensure that it can be smoothly inserted during the clamping process and achieve the expected locking effect; after the processing of the slot and post is completed, the clamping operation is then performed. The slot can be set as a T-shaped slot, and the post can be set as a T-shaped head.

[0079] In some embodiments, the step of connecting the valve stem and the valve seat by one of welding, bonding and threaded connection further includes: pre-treating the connection surface between the valve stem and the valve plate to remove impurities and an oxide layer.

[0080] Specifically, first, the connection surface can be cleaned with a detergent to remove grease, dust and other visible impurities on the surface. When cleaning, ensure that the detergent covers the entire connection surface and remove impurities by wiping or rinsing. After cleaning, the connection surface usually needs to be deoxidized. For example, physical friction is used to remove the oxide layer or chemical reaction is used to dissolve or peel off the oxide layer. After removing impurities and oxide layers, the connection surface should be thoroughly dried to remove residual solvents or moisture. Then, the connection surface is carefully inspected to ensure that there are no missed impurities or oxidation points.

[0081] In some embodiments, the step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection further includes: performing ultrasonic testing or magnetic particle flaw detection on the valve stem, the valve plate and the corresponding connection parts. That is, after the valve stem and the valve plate are connected, the connection parts can be subjected to ultrasonic testing or magnetic particle flaw detection to ensure the connection strength and reduce the risk of failure of the valve stem and the valve plate to be connected again.

[0082] In some embodiments, the step of installing the valve cover to the valve seat includes: cleaning and inspecting corresponding installation surfaces of the valve cover and the valve seat, and applying sealing grease.

[0083] Specifically, after confirming that the mounting surface is clean and intact, the next key step is to apply sealing grease. Sealing grease is a lubricant specially used to enhance the sealing effect. It can fill the tiny gaps between the mounting surfaces to form a continuous sealing layer, effectively preventing the leakage of the medium. When applying sealing grease, it is necessary to select the appropriate type of sealing grease based on factors such as the material of the valve, the characteristics of the medium, and the working environment, and follow the prescribed application method and thickness requirements. During the application process, ensure that the sealing grease evenly covers the entire mounting surface, especially the edges and corners, which are prone to leakage, to improve the sealing effect.

[0084] During the use of the online repair method for the failure of the connection between the valve stem and the valve plate in the gate valve provided by the embodiment of the present invention, when the connection between the valve stem and the valve plate fails, the handwheel can still be rotated, and the valve plate can be pushed back to the valve seat by the handwheel to ensure the seal between the two sealing surfaces of the valve plate and the valve seat; then, the valve sealing packing gland nut is unscrewed to loosen the sealing packing to achieve the removal of the sealing packing; then, the connecting bolts between the valve cover and the valve seat are loosened in turn but not completely unscrewed to judge the sealing performance of the valve plate.

[0085] Then, continue to turn the handwheel in the closing direction, and the valve stem will not move anymore, thus ensuring that the two sealing surfaces of the valve plate and the valve seat are completely sealed. If the closure is not tight and a small amount of medium leaks out, it will not affect the on-site construction in a short time. You can unscrew all the connecting bolts between the valve cover and the valve seat, remove the upper part of the valve cover and the valve stem, and expose the top of the valve plate in the valve seat.

[0086] Furthermore, gently rotate the valve stem in the part above the valve cover, withdraw the valve stem from the valve stem nut and packing, and at the same time remove the locking nut of the valve stem, remove the handwheel and valve stem, so as to separate the valve stem from the valve cover.

[0087] After that, the valve stem that has been removed is reconnected to the valve plate. The connection between the valve stem and the valve plate can be welding, bonding or threaded connection. For example, when the medium to be circulated in the gate valve is a water line, a wind line or a steam line, the connection between the valve stem and the valve plate can be welded. Even if the valve plate and valve seat are not tightly sealed and there is leakage of the medium, as long as it does not affect the construction, it can be used. When the medium to be circulated in the gate valve is oil or gas, since welding is unsafe, bonding or threaded connection can be used.

[0088] It should be noted that after the valve stem and valve plate are reconnected and installed, the valve stem and valve cover installation plane should be vertical and well aligned. Otherwise, when the valve is opened after the repair, the valve stem will bend and it will be difficult to open and close.

[0089] Finally, after the valve stem is connected, put the valve cover, part of the packing, the gland, and the valve stem nut on the valve stem in turn and screw it in. The sealing gasket can be replaced as needed to prevent leakage after the sealing surface is put into use. After the valve cover is in place, align it with the screw holes of the valve body and tighten the bolts symmetrically. Then add some packing to the stuffing box as needed and tighten the packing gland appropriately. Finally, put the handwheel on the valve stem and tighten the locking nut. The repair work is completed.

[0090] In the description of the present invention, it is necessary to understand that the terms "center", "up", "down", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0091] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0092] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral one; it can be a mechanical connection, an electrical connection, or communication with each other; it can be a direct connection, or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0093] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being "above", "above" or "above" a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being "below", "below" or "below" a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0094] In the present invention, the terms "one embodiment", "some embodiments", etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and the features of different embodiments or examples without contradiction.

[0095] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. An online repair method for failure of connection between valve stem and valve plate in gate valve, characterized in that: The steps include: Move the valve stem to drive the valve plate to move to the sealing surface in the valve seat; Separating the valve cover, the valve stem and the valve seat to expose the valve plate; Connecting the valve stem and the valve plate by one of welding, bonding and threading; The valve cover is installed to the valve seat to complete the repair.

2. The online repair method for failure of connection between valve stem and valve plate in gate valve according to claim 1, characterized in that: The steps of moving the valve stem to drive the valve plate to move to the sealing surface in the valve seat include: Turn the hand wheel to make the valve stem push against the valve plate and move to the sealing surface of the valve seat; Loosen the connecting bolts between the valve cover and the valve seat, and check and detect the sealing between the valve plate and the valve seat.

3. The online repair method for failure of connection between valve stem and valve plate in gate valve according to claim 1, characterized in that: The step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection includes the following steps when threaded connection is used: Drilling and tapping a threaded hole in a central area of ​​the top of the valve plate; Processing a threaded section on the valve stem to match the threaded hole; The valve stem and the valve plate are connected by tightening the threaded section and the threaded hole.

4. The online repair method for failure of connection between valve stem and valve plate in gate valve according to claim 3 is characterized in that: The step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection includes the following steps when threaded connection is used: After the threaded section of the valve stem is screwed into the threaded hole of the valve plate, the valve stem is subjected to torque detection.

5. The online repair method for failure of connection between valve stem and valve plate in gate valve according to claim 1, characterized in that: The step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection includes the following steps: The valve stem and the valve plate are preheated.

6. The online repair method for failure of connection between valve stem and valve plate in gate valve according to claim 1, characterized in that: The step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection includes the following steps when bonding is used: Obtaining the type of medium to be circulated in the gate valve; Determine the adhesive according to the medium type; Obtain the temperature and humidity of the environment where the valve seat is located and the temperature of the valve seat itself; Determine the preset curing time of the adhesive based on the ambient temperature and humidity and the temperature of the valve seat itself; Adhesive is applied to the valve stem and the valve seat until the curing time of the adhesive reaches a preset curing time.

7. The online repair method for failure of connection between valve stem and valve plate in gate valve according to claim 1, characterized in that: The step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection includes the following steps: Processing the top of the valve plate to form a groove; Processing the valve stem to form a clamping column matching the clamping groove; The clamping column is clamped into the clamping slot.

8. The online repair method for failure of connection between valve stem and valve plate in gate valve according to claim 1, characterized in that: Before the step of connecting the valve stem and the valve plate by one of welding, bonding and threaded connection, the method further includes: pre-treating the connection surfaces of the valve stem and the valve plate to remove impurities and an oxide layer.

9. The online repair method for failure of connection between valve stem and valve plate in gate valve according to claim 1, characterized in that: After the step of connecting the valve stem and the valve plate by one of welding, bonding and threading, the method further comprises: The valve stem, valve plate and corresponding connection parts are subjected to ultrasonic testing or magnetic particle testing.

10. The online repair method for failure of connection between valve stem and valve plate in a gate valve according to any one of claims 1 to 9, characterized in that: The step of installing the valve cover to the valve seat comprises: Clean and inspect the corresponding mounting surfaces of the valve cover and the valve seat, and apply sealing grease.

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