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Key inspection areas for control valves in case of failure: 1. The inner wall of the valve body. For control valves used in applications with high pressure differences and corrosive media, the inner wall is frequently subjected to the impact and corrosion caused by these media; therefore, it is essential to carefully check their resistance to pressure and corrosion. 2. Valve seat: During operation of control valves, as the medium seeps in, the internal surface of the threads used to secure the valve seat is prone to corrosion, which can cause the valve seat to become loose; this should be taken into consideration during inspections. For valves operating under high pressure differences, it is also necessary to check whether the sealing surface of the valve seat has been damaged. 3. Valve core: The valve core is the moving component of a control valve during operation, and it is subject to the most severe erosion and corrosion caused by the medium. During maintenance, it is necessary to carefully check whether all parts of the valve core have been corroded or worn out; especially under high pressure differences, wear on the valve core is more severe, and this issue needs to be taken into account due to cavitation effects. The valve core should be replaced when it is severely damaged. It is also necessary to check whether the valve stem exhibits similar issues, or if there is a loose connection with the valve core. 4. Are the \"O\"-ring seals and other gaskets aged or cracked? 5. Attention should be paid to the PTFE filler and seal lubricant to check for aging, as well as to whether the mating surfaces are damaged; they should be replaced if necessary. Methods to increase lifespan 01: Extending lifespan by operating at full opening – Have the control valve operate at its maximum opening from the start, such as 90%. In this way, damages such as cavitation and erosion occur on the head of the valve core. As the valve core is damaged, the flow rate increases, causing the valve to close a little more; this process of continuous damage and gradual closure ensures that the entire valve core is utilized to the fullest extent, until the root of the valve core and the sealing surface are damaged and the valve can no longer be used. At the same time, when operating at a large opening, the throttle gap is larger, reducing erosion; this increases the lifespan by more than 1 to 5 times compared to operating the valve at intermediate or small openings from the start. If a chemical plant adopts this method, the service life of the valves is doubled. 02 Method of reducing S, increasing the operating opening, and extending lifespan: By reducing S, the losses in the system other than the control valve increase, which leads to a lower pressure drop across the valve. To ensure that flow passes through the control valve, its opening must be increased. At the same time, the reduced pressure drop across the valve diminishes erosion and cavitation. Specific methods include: installing an orifice plate behind the valve to create a pressure drop through throttling ； Close the manual valve connected in series on the pipeline until the control valve reaches an optimal operating position. For when the valve is initially selected to operate at a small opening degree, this method is very simple, convenient, and effective. 03 Method of reducing diameter, increasing operating opening, and extending lifespan: The operating opening is increased by reducing the diameter of the valve. The specific methods include: replacing the valve with one of a smaller diameter, such as changing from DN32 to DN25 ； The valve body remains unchanged; only the spool and seat with a smaller seat diameter are replaced. During a major overhaul of a chemical plant, replacing the throttle element dgl0 with dg8 doubled its service life. 04 Method of improving lifespan by shifting the location of damage: Move the areas most severely damaged to less critical positions, in order to protect the sealing surfaces and throttling surfaces of the valve core and seat. 05 Method of increasing lifespan by enlarging the throttling channel: The simplest way to do this is to thicken the valve seat, thereby increasing the diameter of the valve seat hole and creating a longer throttling channel. On the one hand, it can delay the sudden expansion that occurs after throttling in a flow-blocking manner, thereby shifting the location of failure and keeping it away from the sealing surface ； On the other hand, it increases throttling resistance, reduces the degree of pressure recovery, and thereby attenuates cavitation. Some designs feature a stepped or wavy shape for the valve seat hole, in order to increase resistance and reduce cavitation. This method is often used on the high-pressure valves in new installations and when upgrading old valves, and it is also very effective. 06 Method of changing the flow direction to extend lifespan: The flow moves in an outward direction; cavitation and erosion mainly affect the sealing surfaces, causing rapid damage to the root of the valve element as well as the sealing surfaces of the valve seat ； In the flow-blocking type, flow moves in the direction of closure; cavitation and erosion occur after throttling, below the valve seat sealing surface, which protects the sealing surface and the root of the valve element, thereby extending its lifespan. For valves used in a flow-diverting manner, when extending their lifespan is a significant concern, simply changing the flow direction can double or triple their service life. 07 Using special materials to improve durability: To resist cavitation (damage in the form of honeycomb-like spots) and erosion (streamline-shaped grooves), special materials resistant to cavitation and erosion can be used to manufacture throttle components. Such special materials include 6YC-1, A4 steel, Stellite, and cemented carbide. To resist corrosion, materials that are more resistant to corrosion and possess certain mechanical and physical properties can be used instead. This material is divided into two categories: non-metallic materials (such as rubber, PTFE, ceramics, etc.) and metallic materials (such as Monel, Hastelloy, etc.). 08 Methods to Improve Lifespan by Changing Valve Structure: The goal of increasing lifespan is achieved by altering the valve structure or by using valves with a longer service life, such as multi-stage valves, anti-cavitation valves, and corrosion-resistant valves. 09 Reducing the stroke to extend diaphragm life: For two-position control valves, when they are operated very frequently, the diaphragm can quickly break as a result of repeated folding up and down; the point of failure is usually along the circumference of the tray. The simplest and most effective way to increase diaphragm life is to reduce the stroke. The reduced stroke value is 1/4dg. For valves such as the dgl25, the standard stroke is 60 mm, but it can be reduced to 30 mm, a reduction of 50%. In addition, the following factor can also be considered: minimizing the pressure in the membrane chamber while meeting the conditions for opening and closing ； Improve the smoothness at the joint where the pallet meets the diaphragm. Methods to prevent clogging of control valves that often get stuck or blocked: 01 Cleaning method. Weld slag, rust, debris, etc. in the pipelines can cause blockages or sticking at the throttle openings, guide areas, and balance holes on the lower valve cover; this can result in scratches and abrasions on the surface of the valve core and guide surfaces, as well as indentations on the sealing surfaces. This often occurs in newly commissioned systems and in the early stages after major repairs. This is the most common fault. In such cases, it is necessary to remove the component for cleaning in order to get rid of debris; if the sealing surface is damaged, it should also be ground ； At the same time, open the bottom plug to flush out the debris that has fallen from the balance hole into the lower valve cover, and to clean the piping. Before commissioning, open the control valve fully; allow the medium to flow for a while before proceeding to normal operation. 02 External flushing method: When using ordinary valves to regulate media that tend to precipitate and contain solid particles, blockages often occur at the throttling ports and guide areas; in such cases, flushing gas and steam can be supplied at the bottom plug of the lower valve cover. When the valve becomes clogged or stuck, opening the external gas or steam valve allows for flushing to be carried out without moving the control valve, thereby restoring normal operation of the valve. 03 Installation of pipeline filters: For small-diameter control valves, especially those with extremely low flow rates, the throttling gap is very small; therefore, there must not be any debris in the fluid. In the event of such blockage, it is best to install a filter on the pipeline before the valve to ensure smooth flow of the medium. For control valves used with positioners, when the positioner does not function properly, the most common fault is a blocked throttle in its air supply line. Therefore, when the locator is in use, it is necessary to properly manage the air supply; the common approach is to install an air filter and pressure regulator on the air supply pipeline before the locator. 04 Increasing the throttle gap: When solid particles in the medium, or weld slag and rust that have been washed away in the pipes, cause blockages or jams due to their inability to pass through the throttle opening, it is possible to use a throttle element with a larger throttle gap – namely, a valve core or sleeve with window-like or open sections. Since the throttle area is concentrated rather than distributed around the circumference, such problems can be easily resolved. For single or double-seat valves, the plunger-type valve core can be replaced with a valve core having a “V”-shaped port, or it can be changed to a cartridge valve or similar. For example, a chemical plant had a two-seat valve that would get stuck frequently; after it was recommended to replace it with a sleeve valve, the problem was resolved immediately. 05 Medium scouring method: Utilizes the scouring energy of the medium itself to scour away and remove substances that tend to settle or cause blockages, thereby enhancing the valve’s resistance to blockages. Common methods include: converting it to a flow-closed type for use ； Use a streamlined valve body ； Place the throttle orifice at the most severely eroded area; when using this method, it is important to improve the erosion resistance of the material used for the throttle component. 06 Changing from straight-through to corner flow method: The straight-through configuration results in an inverted S-shaped flow pattern; the flow path is complex, with numerous dead zones in the upper and lower chambers, which provide areas for the medium to settle. Angular connection: the medium flows as if through a 90° elbow, offering good scouring performance, a small dead zone, and allowing for easy design in a streamlined shape. Therefore, when a slight blockage occurs with a straight-through control valve, it can be replaced with an angle valve. Solutions to leakage in control valves 01: Adding sealing grease. For valves that do not currently use sealing grease, it is possible to add such grease to improve the sealing performance of the valve stem. 02 Adding packing: To improve the sealing performance of the packing around the valve stem, the method of adding more packing can be employed. Typically, a dual-layer or multi-layer mixed packing structure is used; simply increasing the number of elements, for example from 3 to 5, does not yield significant results. 03 Method of replacing graphite packing: The widely used PTFE packing, with an operating temperature range of –20 to +200°C, experiences a significant decline in its sealing performance when the temperature varies greatly between these limits; it ages rapidly and has a short lifespan. Flexible graphite fillers can overcome these disadvantages and have a long service life. As a result, some factories have replaced all PTFE packing with graphite packing, and even newly purchased control valves have their PTFE packing replaced with graphite packing before use. However, the hysteresis with graphite fillers is large, and some systems exhibit crawling behavior at first; this must be taken into consideration. 04 Change the flow direction and place P2 at the end of the valve stem. When △P is large and P1 is also high, sealing P1 is clearly more difficult than sealing P2. Therefore, the method of changing the flow direction can be adopted, by moving P1 to the valve stem end and P2 to the other end; this is particularly effective for valves with high pressure and large pressure differences. For example, with bellows valves, sealing P2 should usually be taken into consideration. 05 Use the lens gasket sealing method for the sealing of the upper and lower covers, as well as for the sealing between the valve seat and the upper and lower valve bodies. In the case of a flat seal, its sealing performance is poor under high temperature and pressure, leading to leaks; using a lens gasket for sealing can yield satisfactory results. 06 Replacing gaskets: To this day, most gaskets are still made of asbestos sheets; under high temperatures, they have poor sealing properties and a short lifespan, which leads to leaks. In such cases, wound gaskets or \"O\"-rings can be used as alternatives; many factories are now adopting them. 07 Symmetric bolt tightening using the thin washer sealing method: In control valve structures with O-ring sealing, when thick gaskets with significant deformation (such as wound gaskets) are used, uneven compression and uneven stress distribution can easily lead to damage, misalignment, and deformation of the seal, severely affecting its sealing performance. Therefore, when repairing or assembling such valves, the compression bolts must be tightened symmetrically (be careful not to tighten them all at once). It would be better if thick gaskets could be replaced with thin ones, as this makes it easier to reduce the inclination and ensure a good seal. 08 Methods for increasing the width of the sealing surface in order to prevent the flat valve element from jumping during closure and to reduce leakage. In flat-type valve elements (such as those used in two-position valves or sleeve valves), there are no guiding or directing surfaces within the valve seat. As the valve operates, lateral forces act on the valve element, pushing it from the inlet side toward the outlet side. The greater the clearance between the valve element and the valve seat, the more severe this unilateral movement becomes. Additionally, deformation, misalignment, or a small chamfer on the sealing surface of the valve element (usually a 30° chamfer is used for guidance) can cause the chamfered end of the valve element’s sealing surface to come into contact with the valve seat’s sealing surface when the valve is near closure. This results in the valve element jumping during closure, or even failing to close properly, thereby increasing leakage. The simplest and most effective solution is to increase the size of the sealing surface on the valve stem, so that the minimum diameter of the end face of the valve stem is 1–5 mm smaller than the diameter of the valve seat; this provides sufficient guidance to ensure that the valve stem fits into the valve seat and maintains good contact between the sealing surfaces. Solutions to control valve vibration (8 methods) 01 Increasing stiffness: For oscillations and mild vibrations, increasing the stiffness can be used to eliminate or reduce them; methods such as using springs with higher stiffness or switching to piston actuators are feasible. 02 Increasing damping: Increasing damping means increasing the friction against vibrations; for example, the plug of a sleeve valve can be sealed using \"O\"-rings, or graphite packing with high friction can be employed. This can help to eliminate or reduce minor vibrations to some extent. 03 Increasing the guiding dimensions and reducing the clearance: Plug-type valves generally have small guiding dimensions, and the clearance between the various components of such valves is usually large, ranging from 0.4 to 1 mm; this condition facilitates the occurrence of mechanical vibrations. Therefore, when mild mechanical vibrations occur, the vibrations can be reduced by increasing the guiding dimensions and decreasing the fit clearance. 04 Changing the shape of the throttling element to eliminate resonance: Since the so-called source of vibration in control valves lies at the throttling area where flow velocity is high and pressure changes rapidly, altering the shape of the throttling element can change the frequency of this vibration source, making it easier to resolve the issue when resonance is not severe. The specific method is to turn the valve core surface by 0.5–1.0 mm within the vibration opening range. In a factory’s residential area, a self-acting pressure control valve was installed; resonance caused humming noises that disturbed the workers’ rest. After grinding 0.5 mm off the surface of the valve core, the resonant humming ceased. 05 Method of eliminating resonance by replacing the throttle element: methods include changing the flow characteristic, from logarithmic to linear, and from linear to logarithmic ； Change the type of valve core. If the plug type is changed to a “V”-groove valve core, and the double-seat valve plug type is changed to a cartridge type ； Replace the sleeve that opens a window with a sleeve that has holes, etc. In a nitrogen fertilizer plant, a DN25 two-seat valve experienced frequent breakage at the connection between the valve stem and the valve disc. After identifying resonance as the cause, we replaced the linear-characteristic valve disc with a logarithmic one, and the problem was resolved. For another example, a laboratory at an aviation academy was using a DN200 sleeve valve; the plug of this valve rotated violently and could not be used. After changing the sleeve with openings to one with small holes, the rotation stopped immediately. 06 Changing the type of control valve to eliminate resonance: Control valves with different structural designs have inherent frequencies that vary naturally; changing the type of control valve is the most effective way to eliminate resonance at its root. A valve that experiences severe vibration – intense shaking (which can damage the valve in serious cases), strong rotation (to the point where the valve stem may break or twist), and produces loud noise (reaching over 100 decibels) – will see immediate improvement once it is replaced with a valve that has a significantly different structure; the severe resonance disappears miraculously. In the new expansion project of a vinylon factory, a DN200 sleeve valve was selected, and all three of the aforementioned problems occurred: the DN300 pipeline vibrated, the valve plug rotated, the noise level exceeded 100 decibels, and the resonance opening range was 20–70%. Given the large resonance opening, a double-seat valve was used instead, and as a result the resonance disappeared and the valve operated normally. 07 Method of reducing cavitation vibration: For the cavitation vibration caused by the rupture of cavitation bubbles, it is natural to seek ways to reduce cavitation. Ensure that the impact energy generated by the bursting of bubbles does not act on the solid surface, especially the valve core, but is absorbed by the liquid instead. Sleeve valves have this feature, which allows the plug-type valve core to be replaced with a sleeve-type one. All methods to reduce cavitation should be employed, such as increasing throttling resistance, raising the pressure at the constriction, and using staged or series pressure reduction. 08 Avoid vibration caused by external shock waves: External shock waves can cause vibration in valves, and this is something that must be avoided during the normal operation of control valves. If such vibration occurs, appropriate measures should be taken. Solutions to high noise levels in control valves 01: Eliminating resonance noise. Strong noise of over 100 decibels occurs only when the control valve resonates, as energy builds up in that condition. Some exhibit strong vibration with low noise, while others have weak vibration but very high noise levels ； Some have significant vibration and noise. This noise produces a single-toned sound, with a frequency generally ranging from 3000 to 7000 Hz. Obviously, by eliminating resonance, the noise disappears as well. 02 Methods to eliminate cavitation noise: Cavitation is a major source of hydrodynamic noise. During cavitation, the bursting of bubbles creates high-speed shock waves, resulting in intense local turbulence and thus cavitation noise. This noise has a wide frequency range and produces a rattling sound, similar to the noise generated by sand and gravel in the fluid. Eliminating and reducing cavitation is an effective way to eliminate and reduce noise. 03 Using the thick-walled pipeline method: Employing thick-walled pipes is one of the methods for acoustic path treatment. Using thin walls can increase noise by 5 decibels, while using thick-walled pipes can reduce noise by 0 to 20 decibels. The thicker the wall for a given diameter, and the larger the diameter for a given wall thickness, the better the noise reduction effect. For a DN200 pipe, when the wall thicknesses are 6.25, 6.75, 8, 10, 12.5, 15, 18, 20, and 21.5 mm respectively, the noise reduction can be -3.5, -2 (i.e., an increase), 0, 3, 6, 8, 11, 13, and 14.5 decibels respectively. Of course, the thicker the wall, the higher the cost. 04 Using sound-absorbing materials is also a common and highly effective method for handling sound paths. The noise source and the pipelines behind the valve can be wrapped with sound-absorbing materials. It must be noted that since noise can travel over long distances through fluid flow, the effectiveness of noise reduction ends wherever sound-absorbing materials are applied and thick-walled pipes are used. This method is suitable for situations where the noise level is not high and the pipeline length is not long, as it is a relatively costly approach. 05 Series-connected silencer method: This method is suitable for reducing aerodynamic noise; it can effectively eliminate noise within the fluid and suppress the noise level transmitted to the solid boundary layer. For applications with high mass flow rates or a high pressure drop across the valve, this method is the most effective and economical. Using absorptive series silencers can significantly reduce noise. However, from an economic perspective, it is generally limited to attenuating to about 25 decibels. 06 Soundproof box method: Utilize soundproof boxes, houses, and buildings to enclose the noise source, thereby reducing external noise levels to an acceptable level. 07 Series Throttling Method: In cases where the pressure ratio of the control valve is high (△P/P1≥0.8), the series throttling method is employed, which involves distributing the total pressure drop across both the control valve and a fixed throttling element located after the valve. Using diffusers or porous flow restrictors is the most effective method among those for reducing noise. To achieve optimal diffuser efficiency, it is necessary to design the diffuser (its shape and size) based on the installation conditions of each unit, so that the noise level generated by the valve is equal to the noise level generated by the diffuser. 08 Use low-noise valves. These valves work by allowing the fluid to slow down gradually as it passes through the complex flow paths within the valve core and seat (multiple channels and grooves), thereby preventing supersonic speeds from occurring at any point in those flow paths. There are various forms and structures of low-noise valves (some designed for specific systems) available for use. When the noise level is not very high, using a low-noise sleeve valve can reduce noise by 10 to 20 decibels; it is the most cost-effective low-noise valve available. Solutions when the stability of a control valve is poor 01: Changing the direction of the unbalanced force. In stability analysis, it is known that when the unbalanced force acts in the same direction as the valve’s closing direction, that is, when it exerts a force that tends to close the valve, the valve’s stability is poor. When the valve operates under the conditions of such unbalanced forces, the approach adopted is to change the direction of their action; usually, this involves changing the valve from a flow-blocking type to a flow-allowing type, and this generally allows the stability issue of the valve to be resolved easily. 02 Method to avoid operating in the valve’s own unstable zone: Some valves, due to limitations in their structure, exhibit poor stability when operating at certain opening degrees. The two-seat valve has an opening degree of less than 10%; flow occurs at the upper ball while it is blocked at the lower ball, resulting in instability ； Nearwhere the slope of the unbalanced force variation becomes alternating, its stability is poor. For example, in the case of butterfly valves, the alternating point is around 70 degrees ； The two-seat valve is at 80–90% opening. When encountering such valves, operating in the unstable region will inevitably result in poor stability; avoiding operation in that region is sufficient. 03 Replace with a valve that has good stability. A valve with good stability exhibits minimal changes in unbalanced forces and provides excellent guidance. Among the commonly used ball valves, sleeve valves possess this significant feature. When single- and double-seat valves have poor stability, replacing them with a set of cartridge valves will definitely improve stability. 04 Increasing spring stiffness: The ability of the actuator to resist the effects of load changes on its stroke depends on the spring stiffness; the greater the stiffness, the less impact there is on the stroke, and the better the stability of the valve. Increasing the spring stiffness is a common and simple method to improve valve stability; for example, replacing springs with a stiffness range of 20–100 KPa with springs having a higher stiffness of 60–180 KPa. This approach is mainly used for valves equipped with positioners; otherwise, a separate positioner must be installed on the valve. 05 Method of reducing response speed: When the system requires that the response or adjustment speed of the control valve not be too fast, yet the valve’s response and adjustment speed are actually high; for example, when fine tuning of flow rate is needed but the flow regulation capability of the control valve is quite large, or when the system itself is already a fast-response system but the control valve is equipped with a positioner to accelerate its operation, these situations are unfavorable. This will result in overshoot and vibrations, etc. To address this, the response speed should be reduced. One solution is to change the linear characteristic to a logarithmic characteristic ； Those with positioners can be replaced by converters or actuators. Handling other faults of control valves: 01 Change the flow direction to resolve the issue of premature shutdown, and use methods to eliminate surging. Two-position valves are typically used in a flow-blocking mode in order to achieve better shut-off performance. In liquid media, the unbalanced forces resulting from flow closure press the valve core shut, exerting a force that promotes closing; this is also known as suction effect. It accelerates the movement of the valve core, causing slight water hammer and leading to system surging. The solution to the above phenomenon is to change the flow direction to outward flow, and the surge will be eliminated. For problems similar to this, where the promotion of shutdown affects the proper operation of the valve, this approach can also be considered as a solution. 02 Methods to prevent plastic deformation: Plastic deformation causes the surface of one metal to scratch the surface of another metal component, or even cause them to stick together, leading to problems such as valves getting stuck, impaired functionality, damage to the sealing surfaces, increased leakage, and inability to rotate the two parts connected by threads (such as the upper and lower valve bodies in high-pressure valves). Plastic deformation is related to temperature, mating materials, surface roughness, hardness, and load. High temperatures cause the metal to anneal or soften, further exacerbating the tendency toward plastic deformation. Methods to address valve failures caused by plastic deformation include using high-hardness materials in areas prone to scratching, with a hardness difference of 5–10 Rc ； The two parts are made of different materials ； Increase the gap ； Add lubricant ； Repair the damaged surface to improve smoothness and hardness: When the thread won’t turn, it’s necessary to weld it in one go. 01 Adding seal grease method: When factors such as inaccurate calculations or increased production result in a low flow coefficient of the valve, such that the desired flow rate cannot be ensured even when the valve is fully open, it becomes necessary to open a bypass to allow some of the flow to pass through. Typically, the bypass flow is <15–20% of the maximum flow. Here is a method for creating a bypass: since the flow resistance of the flow-closing type is low, its flow coefficient is 10–15% higher than that of the flow-opening type. Therefore, by changing the direction of flow, it is possible to use the flow-closing mode instead of the normal flow-opening mode, allowing the valve to handle a flow rate that is 10–15% higher. This prevents the bypass from being activated, and since it operates at a full opening, stability issues need not be considered. 04 Overcoming fluid disruption: The most typical valve is the double-seat valve, where the fluid enters from the middle; the valve core is perpendicular to the inlet, and the fluid flows around the valve core and exits in two streams, one above and one below. The flow impact on the valve core pushes it toward the outlet side, causing friction that damages the guiding surfaces of the valve core and the bushing, leading to abnormal operation. High flow rates can also cause the valve core to bend or erode, and in severe cases, even break. Solution: Increase the hardness of the material in the guiding area ； Increase the size between the upper and lower balls of the valve core to make it thicker ； Use another valve as a substitute. When a sleeve valve is used, the fluid flows in from around the sleeve, thereby **reducing** the lateral force on the valve plug. 05 Methods to overcome the rotational force generated by fluids and cause the valve core to rotate: For a valve core with a “V”-shaped port, due to the asymmetric flow of the medium, the tangential forces acting on the valve core at the “V”-shaped port are not uniform, resulting in a rotational force that causes it to spin. This is especially true for valves with DN≥100. As a result, it may cause the valve to disconnect from the actuator push rod, and springless actuators may cause the diaphragm to twist. Solutions include rotating the valve core in the opposite direction by an angle to balance the tangential forces acting on it ； Further secure the connection between the valve stem and the push rod; if necessary, add a anti-rotation clamp ； Replace the valve core with a V-shaped opening with a plunger-type valve core ； Adopt or switch to a sleeve-type structure ； If the rotation is caused by resonance, eliminating the resonance will resolve the issue. 06 Adjusting the friction of the butterfly valve disc to overcome opening oscillation: Butterfly valves equipped with soft seals such as \"O\"-rings, sealing rings, and linings are used; when the valve is closed, the deformation of these soft seals ensures that the disc closes properly and covers it completely, thereby achieving an excellent sealing effect. However, when the valve is to be opened, the actuator must exert an increasing force on the valve disc; once this force equals the frictional force exerted by the soft seal on the valve disc, the valve disc begins to move. Once activated, this friction force decreases sharply. To achieve force balance, the valve disc opens violently; when this force, together with the unbalanced torque generated by the medium at that opening degree, balances the opening torque of the actuator, the valve stops at that opening degree. The opening angle resulting from this violent and sudden jump can reach as much as 30–50%, which will cause a series of problems. At the same time, during shutdown, significant changes occur in the soft seals, which can lead to permanent deformation or damage as a result of being compressed or strained by the valve plate, thereby affecting their lifespan. The solution is to adjust the frictional force exerted by the soft seal on the valve disc during startup, which ensures that the required shut-off performance is achieved while also allowing the valve to start operating properly. The specific methods include: adjusting the interference amount ； By using limits or adjusting the pre-tension and output force of the actuator, the difficulties arising from excessive closure of the valve plate when attempting to open it can be reduced.