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58 methods of common valve failure

[作者:中良阀业] [日期:17-12-28] [点击: [Source: Original] [Author: Zhongliang Valve Co.] [Date: 17-12-28] [Views: ]
In industrial automation instruments, the regulating valve is cumbersome, and coupled with its simple structure, it is often not valued by people. However, it is in the process pipeline, the working conditions are complicated, and once problems occur, everyone is busy again. Because of its clumsy, it is difficult to pinpoint the problem, and it is often laborious and unsatisfactory. It also involves system commissioning, system completeness, quality adjustment, and environmental pollution.
I. Methods to improve life (8 methods)
1) The method of extending the life of the wide opening allows the regulating valve to work as far as possible at the maximum opening, such as 90%. In this way, damages such as cavitation and erosion occur on the spool head. As the spool breaks and the flow increases, the corresponding valve will be closed a little. This will continue to break and gradually close, so that the entire spool will be fully utilized until the root and sealing surface of the spool are damaged and cannot be used. At the same time, the large throttle opening has a large throttle gap and reduced erosion, which improves the life of the valve by 1 to 5 times than that of the valve working at the middle and small opening. If a chemical plant adopts this method, the service life of the valve is doubled.
2) Decrease S to increase the operating opening and increase the life method to decrease S, that is, to increase the loss of the system other than the regulating valve , so that the pressure drop distributed to the valve is reduced. At the same time, the pressure drop across the valve is reduced, which also reduces cavitation and erosion. The specific methods are as follows: an orifice plate is arranged behind the valve to throttle the pressure drop; and the manual valve connected in series on the pipeline is closed until the regulating valve obtains a more ideal opening degree. This method is very simple, convenient, and effective when the valve selection works at a large opening.
3) The method of reducing the caliber and increasing the operating opening is to increase the operating opening by reducing the caliber of the valve.
The specific methods are as follows: ① change a valve with a smaller size, such as DN32 to DN25;
② The valve body is not changed. Replace the valve seat with a smaller valve seat diameter. For example, if a throttle plant dgl0 is replaced with dg8 during a major overhaul, the service life is doubled.
4) Transfer the damaged position to improve the life method. Transfer the severely damaged place to the secondary position to protect the sealing surface and throttle surface of the valve core and valve seat.
5) Increasing the throttle channel to increase the life method The simplest way to increase the throttle channel is to thicken the valve seat, so that the valve seat hole grows to form a longer throttle channel. On the one hand, the sudden expansion and delay of the flow-closed throttling can shift the damage position and keep it away from the sealing surface; on the other hand, it increases the throttling resistance, reduces the degree of pressure recovery, and makes the steam Eclipse weakened. Some of the valve seat holes are designed to be stepped and waved to increase resistance and reduce cavitation. This method is often used on high-pressure valves introduced in the device and when old valves are improved, it is also very effective.
6) Change the flow direction to improve the life method. The flow-open type flows in the open direction. Cavitation and erosion mainly act on the sealing surface, causing the valve root and the valve seat sealing surface to be damaged quickly; the flow-close type flows in the closed direction. After cavitation and erosion affect throttling, the valve seat is below the sealing surface, which protects the sealing surface and the root of the valve core and prolongs the service life. Therefore, when the problem of prolonging the life of the valve used as a flow-open type is more prominent, simply changing the flow direction can extend the life by 1 to 2 times.
7) Use special materials to improve the life method to resist cavitation (destroying shapes such as honeycomb dots) and erosion (streamline small grooves). Special materials that are resistant to cavitation and erosion can be used to manufacture throttle parts. This special material includes 6YC-1, A4 steel, Stellite, hard alloy, etc. For corrosion resistance, materials that are more resistant to corrosion and have certain mechanical and physical properties can be used instead. This material is divided into non-metallic materials (such as rubber, PTFE, ceramics, etc.) and metallic materials (such as Monel, Hastelloy, etc.).
8) Change the structure of the valve to improve the life. The method of changing the valve structure or choosing a valve with a longer life is used to achieve the purpose of improving the life, such as the use of multi-stage valves, anti-cavitation valves, corrosion-resistant valves, etc.
Second, the blocking valve (blocking) method that the control valve is often stuck or blocked (6 methods)
1) Welding slag, rust, slag, etc. in the pipeline of the cleaning method cause blockage or jam in the orifice, the guide part, and the lower valve cover balance hole, which will cause strain and scratches on the valve core curved surface and the guide surface, and the sealing surface Indentation and so on. This often happens early in the commissioning of new systems and overhauls. This is the most common failure. In this case, it must be unloaded for cleaning, and remove the slag. If the sealing surface is damaged, it should be ground; at the same time, the bottom plug is opened to flush out the slag that has fallen from the balance hole into the lower valve cover, and the pipeline Rinse. Before putting into operation, let the regulating valve be fully opened, and the medium should flow into the normal operation after a period of time.
2) External flushing method When using a common valve to adjust some media that is easy to settle and contain solid particles, it is often blocked at the throttle and guide. External flushing gas and steam can be connected to the bottom plug of the lower valve cover. When the valve is blocked or stuck, open the external gas or steam valve , and the flushing work can be completed without moving the regulating valve to make the valve operate normally.
3) Install the pipeline filter method for small-caliber regulating valves , especially ultra-small flow regulating valves . The throttle gap is extremely small, and there must be no slag in the medium. In this case, it is best to install a filter on the pipe in front of the valve to ensure the smooth passage of the medium. Regulating valve used with positioner, the positioner does not work normally, and its throttle orifice is the most common failure. Therefore, when working with a positioner, the air source must be handled properly. The usual method is to install an air filter pressure reducing valve on the air source line in front of the positioner.
4) The method of increasing the throttle gap, such as solid particles in the medium or weld slag and rust that have been washed away from the pipeline, ca n’t pass the throttle opening, causing blockage, jamming, and other failures. You can use a throttle with a larger throttle gap. Flow parts—throttles and spools with opening areas such as windows, openings, etc. Because the throttle area is concentrated rather than distributed circumferentially, failures can be easily ruled out. If it is a single or double seat valve, the plunger spool can be changed to a "V" shaped spool, or a sleeve valve. For example, a chemical plant often has a double seat valve stuck. It is recommended to switch to a sleeve valve, and the problem is immediately resolved.
5) The medium scouring method uses the scouring energy of the medium to scour and take away things that are easy to settle and clogging, thereby improving the anti-blocking function of the valve. Common methods are: ① change to flow-closed use; ② use a streamlined valve body; ③ place the orifice in the most severe erosion, using this method to pay attention to improve the erosion resistance of the material of the throttle.
6) The straight-through is changed to the angular method. The straight-through is inverted S flow, the flow path is complicated, and there are many dead zones in the upper and lower volume chambers, which provides a place for the precipitation of the medium. Angular connection, medium flows like 90 ° elbow, good scouring performance, small dead zone, easy to design into streamline. Therefore, when a slight blockage occurs when using a straight-through control valve , it can be used as an angle valve.
Third, the solution to the leakage of the control valve (6 methods)
1) Increase the sealing grease method For valves that do not use sealing grease, consider increasing the sealing grease to improve the valve stem sealing performance.
2) Adding packing method In order to improve the sealing performance of the packing to the valve stem, the method of adding packing can be adopted. Usually double-layer and multi-layer mixed fillers are used. Simply increasing the quantity, such as increasing 3 to 5 tablets, the effect is not obvious.
3) Replace the PTFE filler that is used extensively by the graphite filler method, because its working temperature is in the range of -20 to + 200 ° C. When the temperature is in the upper and lower limits and the change is large, the sealing performance will be significantly reduced, the aging will be fast, and the service life short. Flexible graphite fillers overcome these disadvantages and have a long service life. Therefore, some factories have all changed the PTFE packing to graphite packing, and even the newly purchased control valves have replaced the PTFE packing with graphite packing. However, the use of graphite filler has a large return difference, and some crawling phenomena may occur at the beginning, which must be considered.
4) Change the flow direction and set P2 at the valve stem end. When △ P is larger and P1 is larger, it is obviously more difficult to seal P1 than to seal P2. Therefore, a method of changing the flow direction can be adopted, and P1 is changed to P2 at the valve rod end, which is more effective for valves with high pressure and large pressure difference. Such as bellows valve should usually consider sealing P2.
5) The lens pad sealing method is used to seal the upper and lower covers, and the valve seat is sealed to the upper and lower valve bodies. If it is a plane seal, the sealing performance is poor under high temperature and high pressure, which causes leakage. You can use a lens pad to seal it to obtain a satisfactory effect.
6) Until the replacement of gaskets, most of the gaskets still use asbestos. At high temperatures, the sealing performance is poor, the life is short, and leakage is caused. In this case, you can use wound gaskets, "O" rings, etc., which are now used by many factories.
Fourth, the solution to the valve vibration (8 methods)
1) The method of increasing stiffness can eliminate or weaken the oscillation and slight vibration by increasing the stiffness. For example, it is feasible to use a spring with a large stiffness and use a piston actuator.
2) Increasing the damping method Increasing the damping means increasing the friction against vibration. For example, the valve plug of the sleeve valve can be sealed with an "O" ring, and graphite filler with a large friction force is used to eliminate or reduce the slight vibration. Have a role.
3) Increasing the guide size and reducing the fit clearance method Generally, the size of the shaft plug valve is smaller, and the fit clearance of all valves is generally larger, ranging from 0.4 to 1 mm, which is helpful for generating mechanical vibration. Therefore, when slight mechanical vibration occurs, the vibration can be weakened by increasing the guide size and reducing the fit clearance.
4) Change the shape of the throttle to eliminate the resonance method. The so-called vibration source of the regulating valve occurs at the throttle port with high speed flow and rapid pressure change. Changing the shape of the throttle can change the frequency of the vibration source. Compare when the resonance is not strong. Easy to resolve. The specific method is to turn the surface of the valve core within the range of the vibration opening degree by 0.5 to 1.0 mm. For example, if a self-operated pressure regulating valve is installed near the area belonging to a manufacturer, the whistling due to resonance affects the employees' rest. After we turn off the surface of the valve core 0.5mm, the resonance whistling sound disappears.
5) The methods of replacing the throttle to eliminate resonance include:
① Change the flow characteristics, change the logarithm to linear, and change the logarithm to linear;
② Replace the spool type. Such as changing the plug shape to "V" groove valve core, the double seat valve plug type is changed to the sleeve type; the window sleeve is changed to a small hole sleeve. For example, a nitrogen fertilizer plant with a DN25 double seat valve, the connection between the valve stem and the valve core often breaks, we confirmed the resonance, and changed the linear characteristic valve core to a logarithmic valve core, the problem was solved. Another example is a DN200 sleeve valve used in a laboratory of an academy of aviation. The valve plug is strongly rotated and cannot be put into use. After the window sleeve is changed to a small hole sleeve, the rotation disappears immediately.
6) Change the type of regulator to eliminate resonance.
The natural frequency of the regulating valve of different structural forms is naturally different. Changing the type of the regulating valve is the most effective way to fundamentally eliminate resonance. A valve has very strong resonance in use --- strong vibration (the valve can be damaged in severe cases), strong rotation (even the valve stem is broken and twisted), and it produces a strong noise (up to more than 100 decibels) As long as it is replaced by a valve with a large structural difference, the valve immediately works, and the strong resonance miraculously disappears. For example, if a DN200 sleeve valve is selected for the new expansion project of a Vinylon plant, all three phenomena mentioned above will occur. The pipeline of DN300 will bounce, the valve plug will rotate, the noise will be more than 100 decibels, and the resonance opening will be 20 ~ 70%. The degree is large. After switching to a double seat valve, the resonance disappears and the operation is normal.
7) Cavitation Vibration Reduction Method For cavitation vibration caused by cavitation bubble burst, naturally we should find a way to reduce cavitation. ① The impact energy caused by the bubble burst does not act on the solid surface, especially the valve core, but allows the liquid to absorb it. Sleeve valves have this feature, so the plug can be changed to a sleeve type. ② Take all measures to reduce cavitation, such as increasing throttling resistance, increasing the pressure at the constriction orifice, grading or series decompression.
8) Avoid the vibration of the vibration source. The vibration of the external vibration source causes the valve to vibrate. This is obviously to be avoided when the regulating valve works normally. If such vibration occurs, corresponding measures should be taken.
Seven, the solution to the noise of the regulating valve (3 methods)
1) Elimination of Resonant Noise Method Only when the control valve resonates, can energy be superimposed and produce a strong noise of more than 100 dB. Some manifest as strong vibration, low noise, and some weak vibration, but the noise is very large; some vibration and noise are relatively large. This noise produces a single-tone sound, which typically has a frequency of 3000 to 7000 Hz. Obviously, by eliminating resonance, the noise naturally disappears. For methods and examples, see 4), 5), and 6) in 4.5 above.
2) Cavitation noise elimination method Cavitation is the main source of hydrodynamic noise. During cavitation, the bursting of the bubble produces a high-speed impact, causing strong turbulence locally and generating cavitation noise. This noise has a wide frequency range and produces a rattling sound similar to the sound made by sand and gravel in the fluid. Eliminating and reducing cavitation is an effective way to eliminate and reduce noise.
3) The use of thick-walled pipelines using thick-walled pipes is one of the sound path processing methods. The use of thin walls can increase noise by 5 decibels, and the use of thick-walled pipes can reduce noise by 0 to 20 decibels. The thicker the wall with the same pipe diameter, the larger the pipe diameter with the same wall thickness, the better the noise reduction effect. For example, when the DN200 pipeline has a wall thickness of 6.25, 6.75, 8, 10, 12.5, 15, 18, 20, 21.5mm, the noise can be reduced to -3.5, -2 (that is, increased), 0, 3, 6, and 8, 11, 13, 14.5 dB. Of course, the thicker the wall, the higher the cost.
Eight, the solution to the vibration of the control valve (8 methods)
1) The method of increasing stiffness can eliminate or weaken the oscillation and slight vibration by increasing the stiffness. For example, it is feasible to use a spring with a large stiffness and use a piston actuator.
2) Increasing the damping method Increasing the damping means increasing the friction against vibration. For example, the valve plug of the sleeve valve can be sealed with an "O" ring, and graphite filler with a large friction force is used to eliminate or reduce the slight vibration. Have a role.
3) Increasing the guide size and reducing the fit clearance method Generally, the size of the shaft plug valve is smaller, and the fit clearance of all valves is generally larger, ranging from 0.4 to 1 mm, which is helpful for generating mechanical vibration. Therefore, when slight mechanical vibration occurs, the vibration can be weakened by increasing the guide size and reducing the fit clearance.
4) Change the shape of the throttle to eliminate the resonance method. The so-called vibration source of the regulating valve occurs at the throttle port with high speed flow and rapid pressure change. Changing the shape of the throttle can change the frequency of the vibration source. Compare when the resonance is not strong. Easy to resolve. The specific method is to turn the surface of the valve core within the range of the vibration opening degree by 0.5 to 1.0 mm. For example, if a self-operated pressure regulating valve is installed near the area belonging to a manufacturer, the whistling due to resonance affects the employees' rest. After we turn off the surface of the valve core 0.5mm, the resonance whistling sound disappears.
5) Replacing the throttling element The principle of eliminating resonance is the same as 4) in 4.5, but it is just replacing the throttling element. The methods are: ① change the flow characteristics, change the logarithm to linear, and linearly change the logarithm; ② replace the valve core form. Such as changing the plug shape to "V" groove valve core, the double seat valve plug type is changed to the sleeve type; the window sleeve is changed to a small hole sleeve. For example, a nitrogen fertilizer plant with a DN25 double seat valve, the connection between the valve stem and the valve core often breaks, we confirmed the resonance, and changed the linear characteristic valve core to a logarithmic valve core, the problem was solved. Another example is a DN200 sleeve valve used in a laboratory of an academy of aviation. The valve plug is strongly rotated and cannot be put into use. After the window sleeve is changed to a small hole sleeve, the rotation disappears immediately.
6) Change the type of regulator to eliminate resonance.
The natural frequency of the regulating valve of different structural forms is naturally different. Changing the type of the regulating valve is the most effective way to fundamentally eliminate resonance. A valve has very strong resonance in use --- strong vibration (the valve can be damaged in severe cases), strong rotation (even the valve stem is broken and twisted), and it produces a strong noise (up to more than 100 decibels) As long as it is replaced by a valve with a large structural difference, the valve immediately works, and the strong resonance miraculously disappears. For example, if a DN200 sleeve valve is selected for the new expansion project of a Vinylon plant, all three phenomena mentioned above will occur. The pipeline of DN300 will bounce, the valve plug will rotate, the noise will be more than 100 decibels, and the resonance opening will be 20 ~ 70%. The degree is large. After switching to a double seat valve, the resonance disappears and the operation is normal.
7) Cavitation Vibration Reduction Method For cavitation vibration caused by cavitation bubble burst, naturally we should find a way to reduce cavitation. ① The impact energy caused by the bubble burst does not act on the solid surface, especially the valve core, but allows the liquid to absorb it. Sleeve valves have this feature, so the plug can be changed to a sleeve type. ② Take all measures to reduce cavitation, such as increasing throttling resistance, increasing the pressure at the constriction orifice, grading or series decompression.
8) Avoid the vibration of the vibration source. The vibration of the external vibration source causes the valve to vibrate. This is obviously to be avoided when the regulating valve works normally. If such vibration occurs, corresponding measures should be taken.
Nine, the solution to the noisy control valve (8 methods)
1) Elimination of Resonant Noise Method Only when the control valve resonates, can energy be superimposed and produce a strong noise of more than 100 dB. Some manifest as strong vibration, low noise, and some weak vibration, but the noise is very large; some vibration and noise are relatively large. This noise produces a single-tone sound, which typically has a frequency of 3000 to 7000 Hz. Obviously, by eliminating resonance, the noise naturally disappears. For methods and examples, see 4), 5), and 6) in 4.5 above.
2) Cavitation noise elimination method Cavitation is the main source of hydrodynamic noise. During cavitation, the bursting of the bubble produces a high-speed impact, causing strong turbulence locally and generating cavitation noise. This noise has a wide frequency range and produces a rattling sound similar to the sound made by sand and gravel in the fluid. Eliminating and reducing cavitation is an effective way to eliminate and reduce noise.
3) The use of thick-walled pipelines using thick-walled pipes is one of the sound path processing methods. The use of thin walls can increase noise by 5 decibels, and the use of thick-walled pipes can reduce noise by 0 to 20 decibels. The thicker the wall with the same pipe diameter, the larger the pipe diameter with the same wall thickness, the better the noise reduction effect. For example, when the DN200 pipeline has a wall thickness of 6.25, 6.75, 8, 10, 12.5, 15, 18, 20, 21.5mm, the noise can be reduced to -3.5, -2 (that is, increased), 0, 3, 6, and 8, 11, 13, 14.5 dB. Of course, the thicker the wall, the higher the cost.
4) Use of sound-absorbing material method This is also a more common and most effective sound path processing method. Sound-absorbing materials can be used to surround the noise source and the back of the valve. It must be pointed out that, because noise can travel long distances through fluid flow, wherever sound-absorbing materials are packaged and where thick-walled tubes are used, the effectiveness of noise cancellation ends. This method is suitable for situations where the noise is not very high and the pipeline is not very long, because it is a relatively expensive method.
5) Tandem muffler method This method is suitable for silencing aerodynamic noise. It can effectively eliminate the noise inside the fluid and suppress the noise level transmitted to the solid boundary layer. This method is most effective and economical for places with high mass flow or high pressure drop ratios before and after the valve. The use of absorbing series silencers can significantly reduce noise. However, economic considerations generally limit the attenuation to about 25 dB.
6) The soundproof box method uses soundproof boxes, houses and buildings to isolate noise sources inside, and reduce the noise of the external environment to a range acceptable to people.
7) Series throttle method Where the pressure ratio of the regulating valve is high (△ P / P1≥0.8), the series throttle method is used to distribute the total pressure drop on the regulating valve and the fixed throttle element behind the valve. Such as the use of diffusers, porous restrictors, this is the most effective way to reduce noise. In order to obtain the best diffuser efficiency, the diffuser (solid shape and size) must be designed according to the installation of each piece, so that the noise level produced by the valve is the same as the noise level produced by the diffuser.
8) Low-noise valve is selected. The low-noise valve gradually decelerates according to the tortuous flow path (porous channel, multi-slot channel) of the fluid passing through the valve core and the valve seat, so as to avoid supersonic speed at any point in the flow path. There are many forms and structures of low-noise valves (designed for special systems) for use. When the noise is not very large, the low-noise sleeve valve can be used to reduce the noise by 10-20 dB. This is the most economical low-noise valve.
Ten, the solution when the stability of the control valve is poor (11 methods)
1) Method of changing the direction of the imbalanced force In the stability analysis, it is known that when the imbalanced force acts in the same direction as the valve closing direction, that is, when the valve has a tendency to close, the valve stability is poor. When the valve works under the above-mentioned unbalanced force conditions, the method of changing its action direction is selected. Usually, the flow-closed type is changed to the flow-open type. Generally speaking, the stability of the valve can be easily solved.
2) Avoid the working method of the valve's own unstable area. Some valves are limited by their own structures, and have poor stability when working at certain openings. ① Double-seat valve, the opening degree is within 10%, because the upper ball flow opens and the lower ball flow closes, which brings instability problems; ② the unbalanced force changes in the vicinity of the slope where the change occurs, its stability is poor. Such as butterfly valves, the alternation point is about 70 degrees; double-seat valves are at 80 to 90% opening. When encountering such a valve, working in an unstable area is bound to have poor stability, and avoiding working in an unstable area is sufficient.
3) Replace the valve with good stability. The valve with good stability has less change in unbalanced force and good guidance. Among the commonly used ball valves, sleeve valves have this great feature. When the stability of single and double seat valves is poor, the replacement of sleeve valves will definitely improve the stability.
4) Increasing the spring stiffness method The ability of the actuator to resist the impact of load changes on the stroke depends on the spring stiffness. The greater the stiffness, the smaller the impact on the stroke, and the better the valve stability. Increasing the spring stiffness is a common and simple method to improve the stability of the valve. For example, change the spring in the spring range of 20 ~ 100KPa to a spring with a large stiffness of 60 ~ 180KPa. This method is mainly used with a positioner valve. Otherwise, The valve must be equipped with a positioner.
5) Reduce the response speed method When the system requires the regulating valve to respond or the regulating speed should not be too fast, the response and regulating speed of the valve are relatively fast. For example, if the flow rate needs to be fine-tuned, the flow rate of the regulating valve changes greatly, or The system itself is a fast response system, but the regulating valve has a positioner to speed up the valve's movement, which is not good. This will cause overshoot, vibration, etc. To this end, the response speed should be reduced. The methods are: ① change the linear characteristics to logarithmic characteristics; ② those with positioners can be changed to converters and relays.
6) Symmetrically tighten the bolts and use a thin washer seal method. In the "O" ring sealed control valve structure, when a thick gasket (such as a winding sheet) with large deformation is used, if the compression is asymmetric, the force will be asymmetric. , Easy to make the seal damaged, inclined and deformed, seriously affecting the sealing performance. Therefore, in the repair and assembly of such valves, the compression bolts must be tightened symmetrically (note that they cannot be tightened at one time). It is better if the thick gasket can be changed to a thin gasket, so it is easy to reduce the inclination and ensure the seal.
7) The method of increasing the width of the sealing surface to prevent the flat valve core from bouncing when it is closed and reducing its leakage. Flat valve cores (such as two-position valves, plugs of sleeve valves) have no guiding and guiding surfaces in the valve seat. When the valve is in operation, the valve core is subject to lateral force, from the inflow side to the outflow side. The larger the gap between the valve core, the more serious this one-sided phenomenon, coupled with deformation, misalignment, or the valve core sealing surface falls. The angle is small (usually guided by a 30 ° chamfer), so when the valve is close, the chamfered end surface of the valve core is placed on the valve seat sealing surface, causing the valve core to jump when closed, or even the valve is not closed at all. The amount of leakage has increased significantly. The simplest and most effective solution is to increase the size of the sealing surface of the valve core, so that the minimum diameter of the end surface of the valve core is smaller than the diameter of the valve seat by 1 to 5 mm, which has sufficient guiding effect to ensure that the valve core is guided into the valve seat and maintained. Good sealing surface contact.
8) Change the flow direction, solve the problem of closing the valve and eliminate the surge method. The two-position valve is usually used as a flow-closing type in order to improve the cutting effect. For liquid media, due to the effect of the flow-closed unbalanced force, the valve core is closed by pressure, which has a closing effect, also known as the suction effect, which accelerates the speed of the valve core and generates a slight water hammer, which causes system surge. The solution to the above phenomenon is that as long as the flow direction is changed to flow, the surge can be eliminated. Similar problems that affect the valve's normal operation due to the promotion of closing can also be considered to solve this problem.
9) The most typical valve to overcome the fluid damage method is a double seat valve. The fluid enters from the middle, the valve core is perpendicular to the inlet, and the fluid bypasses the valve core and flows out into two bundles. The fluid impacts the valve core, causing it to lean toward the outlet side, causing friction, damaging the guiding surface of the valve core and the bushing, causing abnormal movement, and high flow may also cause the valve core to bend, erode, or even break in severe cases. Solution: ① Increase the material hardness of the guide part; ② Increase the middle size of the upper and lower balls of the valve core to make it coarse; ③ Use other valves instead. If a sleeve valve is used, fluid flows around the sleeve, and the lateral thrust on the valve plug is greatly reduced.
10) The method of overcoming the rotating force generated by the fluid to rotate the valve core. For the valve core of the "V" port, the tangential force of the valve core acting on the "V" port is inconsistent due to the asymmetry of the medium inflow. Rotating rotational force. Especially for valves with DN≥100. As a result, the valve may be disconnected from the actuator stem, and the springless actuator may cause the diaphragm to distort. The solutions are: ① turn the valve spool in an opposite direction to balance the tangential force acting on the valve spool; ② further lock the connection between the valve stem and the push rod, and if necessary, add an anti-rotation plywood; ③ Replace the “V” -shaped valve core with a plunger-type valve core; ④ Use or change to a sleeve type structure; ⑤ If the rotation is caused by resonance, eliminating the resonance can solve the problem.
11) Adjust the friction of the butterfly valve plate to overcome the opening and closing method. Butterfly valves with soft seals such as "O" rings, seal rings, and linings are used. When the valve is closed, due to the deformation of the soft seal, the valve plate is closed in place and wraps the valve. Plate, can achieve very ideal cutting effect. However, when the valve is to be opened, the force of the actuator to open the valve plate is constantly increasing. When the friction force of the soft seal on the valve plate is equal, the valve plate is started. Once activated, this friction decreases sharply. In order to achieve the balance of force, the valve plate is opened violently. When this force is balanced with the unbalanced torque of the corresponding opening medium and the opening torque of the actuator, the valve stops at this opening. This violent and sudden take-off opening can be as high as 30-50%, which will cause a series of problems. At the same time, due to the large changes in the soft seals when closing, it is easy to cause permanent deformation or being crushed or damaged by the valve plate, which affects the service life. The solution is to adjust the friction of the soft seal on the valve plate start-up, which can not only ensure that the required cut-off requirements are met, but also make the valve start normally. The specific methods are: ① adjust the interference amount; ② reduce the difficulty caused by excessive closing of the valve plate to open by limiting or adjusting the pre-tightening force and output force of the actuator.

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