Key inspection parts of the regulating valve when a fault occurs
1. The inner wall of the valve body. For regulating valves used in high pressure difference and corrosive media, the inner wall of the valve body is often impacted and corroded by the medium. It is necessary to focus on the pressure resistance and corrosion resistance.
2. The valve seat. When the regulating valve is working, the inner surface of the thread used to fix the valve seat is easily corroded due to the infiltration of the medium, which makes the valve seat loose. Attention should be paid during inspection. For valves working under high pressure difference, it is also necessary to check whether the sealing surface of the valve seat is damaged.
3. The valve core. The valve core is the movable part of the regulating valve when it is working. It is most seriously corroded by the medium. During maintenance, it is necessary to carefully check whether all parts of the valve core are corroded and worn, especially in the case of high pressure difference.
The wear of the valve core is more serious (due to cavitation phenomenon), which should be paid attention to. The valve core should be replaced when it is seriously damaged. In addition, it should be noted whether the valve stem has similar phenomena, or the connection with the valve core is loose, etc.
4. Whether the "O" type sealing ring and other sealing gaskets are aging and cracked.
5. Pay attention to whether the polytetrafluoroethylene packing and sealing lubricating grease are aged and whether the mating surface is damaged, and replace them when necessary.
Methods to increase service life
01. Extend service life by working at a large opening
Let the regulating valve work at the maximum opening as much as possible from the beginning, such as 90%. In this way, damage such as cavitation and erosion occurs on the head of the valve core.
As the valve core is damaged, the flow increases, and the corresponding valve is closed a little more. In this way, it is continuously damaged and gradually closed, so that the entire valve core is fully utilized until the root of the valve core and the sealing surface are damaged and cannot be used.
At the same time, the throttling gap is large when working at a large opening, and the erosion is weakened, which increases the service life by 1 to 5 times more than letting the valve work at an intermediate opening and a small opening from the beginning. For example, a chemical plant adopted this method, and the service life of the valve was increased by 2 times.
02. Reduce s, increase working opening and improve service life
Reduce S, that is, increase the loss of the system except the regulating valve, so that the pressure drop allocated to the valve is reduced. In order to ensure that the flow passes through the regulating valve, the regulating valve opening must be increased. At the same time, the pressure drop on the valve is reduced, so that cavitation and erosion are also weakened.
Specific methods are:
Set an orifice plate after the valve to throttle and consume the pressure drop;
Close the manual valve in series on the pipeline until the regulating valve obtains a more ideal working opening.
When the valve is selected large at the beginning and works at a small opening, this method is very simple, convenient and effective.
03. Reduce the diameter and increase the working opening to improve service life
Increase the working opening by reducing the diameter of the valve.
Specific methods are:
Replace a valve with a smaller diameter, such as DN32 to DN25;
The valve body does not change, and the valve core and valve seat with a small valve seat diameter are replaced.
For example, during the overhaul of a chemical plant, the throttling part dgl0 was replaced with dg8, and the service life was increased by 1 times.
04. Transfer the damaged position to increase the service life
Transfer the severely damaged area to a secondary position to protect the sealing surface and throttling surface of the valve core and valve seat.
05
Increase the throttling channel to increase the service life
The simplest way to increase the throttling channel is to thicken the valve seat, increase the valve seat hole, and form a longer throttling channel.
On the one hand, it can delay the sudden expansion after the flow-closing throttling, which plays a role in transferring the damage position and moving it away from the sealing surface; on the other hand, it increases the throttling resistance, reduces the degree of pressure recovery, and weakens cavitation.
Some valve seat holes are designed into step-type and wave-type styles to increase resistance and weaken cavitation. This method is often used on high-pressure valves in the introduction device and when improving old valves, and it is also very effective.
06
Changing the flow direction to increase the lifespan
The flow-open type flows in the open direction, and cavitation and erosion mainly act on the sealing surface, causing the valve core root and the valve core valve seat sealing surface to be quickly damaged; the flow-closed type flows in the closed direction, and cavitation and erosion act after throttling, below the valve seat sealing surface, protecting the sealing surface and the valve core root, and extending the lifespan.
For valves used as flow-open type, when the problem of extending the lifespan is more prominent, only the flow direction needs to be changed to extend the lifespan by 1 to 2 times.
07. Using special materials to increase the lifespan
To resist cavitation (destruction shape such as honeycomb dots) and erosion (streamlined small grooves), special materials resistant to cavitation and erosion can be used to manufacture throttling parts. Such special materials include 6YC-1, A4 steel, Stellite, hard alloy, etc.
To resist corrosion, more corrosion-resistant materials with 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 metal materials (such as monel, Hastelloy, etc.).
08. Changing the valve structure to increase the life method
The purpose of increasing the life is achieved by changing the valve structure or selecting a valve with a longer life, such as selecting a multi-stage valve, an anti-cavitation valve, a corrosion-resistant valve, etc.
09. Reducing the stroke to increase the life of the diaphragm
For two-position control valves, when the action frequency is very frequent, the diaphragm will quickly break during the up and down folding, and the damage position is often on the circumference of the tray.
The simplest and most effective way to increase the life of the diaphragm is to reduce the stroke. The stroke value after reduction is 1/4dg. For example, the standard stroke of the dgl25 valve is 60mm, which can be reduced to 30mm, shortened by 50%.
In addition, the following factors can also be considered:
Minimize the pressure in the diaphragm chamber while meeting the conditions of opening and closing;
Improve the finish of the contact between the tray and the diaphragm.
Methods to prevent the control valve from getting stuck or blocked
01. Cleaning method
Welding slag, rust, slag, etc. in the pipeline cause blockage or jamming in the throttle, guide part, and balance hole of the lower valve cover, causing strain and scratches on the valve core curved surface and guide surface, and indentation on the sealing surface. This often occurs in new systems and in the early stage of commissioning after overhaul. This is the most common fault.
In this case, it must be removed for cleaning to remove the slag. If the sealing surface is damaged, it should be ground; at the same time, the bottom plug should be opened to flush out the slag that falls from the balance hole into the lower valve cover, and the pipeline should be flushed. Before commissioning, let the control valve fully open, and the medium flow for a period of time before entering normal operation.
02. External flushing method
When ordinary valves are used to regulate some media that are easy to precipitate and contain solid particles, they are often blocked at the throttle and guide. Flushing gas and steam can be connected externally at the bottom plug of the lower valve cover.
When the valve is blocked or stuck, open the external gas or steam valve to complete the flushing work without moving the regulating valve, so that the valve can operate normally.
03. Install pipeline filter method
For small-diameter regulating valves, especially ultra-small flow regulating valves, the throttling gap is very small, and there must not be any residue in the medium.
In case of blockage, it is best to install a filter on the pipeline in front of the valve to ensure smooth passage of the medium.
For regulating valves used with positioners, the positioner does not work properly, and the blockage of the gas path throttling port is the most common fault.
Therefore, when working with a positioner, the gas source must be handled properly. The usual method is to install an air filter pressure reducing valve on the gas source pipeline in front of the positioner.
04. Increase the throttling gap method
If the solid particles in the medium or the welding slag and rust washed away in the pipeline cannot pass through the throttling port and cause blockage or jamming, you can use a throttling piece with a large throttling gap - a valve core or sleeve with a window or opening type of throttling area. Because its throttling area is concentrated rather than distributed circumferentially, the fault can be easily eliminated.
If it is a single or double seat valve, the plunger-shaped valve core can be changed to a "V"-shaped valve core, or a sleeve valve.
For example, a double-seat valve in a chemical plant often gets stuck. It is recommended to use a sleeve valve instead, and the problem is solved immediately.
05. Medium flushing method
Use the flushing energy of the medium itself to flush and take away things that are easy to precipitate and clog, thereby improving the anti-blocking function of the valve.
Common methods include:
Change to flow-closed type;
Use a streamlined valve body;
Place the throttling port at the most severe flushing point. When using this method, pay attention to improving the erosion resistance of the throttling material.
06. Change straight-through to angle method
Straight-through is an inverted S flow, with complex flow paths and many dead zones in the upper and lower chambers, providing a place for the medium to precipitate. With angle connection, the medium is like flowing through a 90° elbow, with good flushing performance, small dead zones, and easy to design into a streamlined shape. Therefore, when a straight-through regulating valve is slightly blocked, it can be changed to an angle valve.
Solution to regulating valve leakage
01. Adding sealing grease method
For valves that do not use sealing grease, consider adding sealing grease to improve the sealing performance of the valve stem.
02. Adding packing method
In order to improve the sealing performance of the packing on the valve stem, the method of adding packing can be used. Usually, double-layer or multi-layer mixed packing is used. Simply increasing the number, such as increasing 3 pieces to 5 pieces, does not have a significant effect.
03. Replacement of graphite packing method
The PTFE packing used in large quantities has a working temperature range of -20 to +200℃. When the temperature changes greatly between the upper and lower limits, its sealing performance will be significantly reduced, aging will be fast, and its life will be short.
Flexible graphite packing can overcome these shortcomings and has a long service life. Therefore, some factories have replaced all PTFE packings with graphite packings, and even the newly purchased regulating valves have replaced the PTFE packings with graphite packings before use. However, the hysteresis of using graphite packing is large, and some of them even produce creeping phenomena at the beginning, which must be considered.
04. Change the flow direction and place P2 at the valve stem end
When △P is large and P1 is large, sealing P1 is obviously more difficult than sealing P2. Therefore, the method of changing the flow direction can be adopted to change P1 at the valve stem end to P2 at the valve stem end, which is more effective for valves with high pressure and large pressure difference. For example, bellows valves should usually consider sealing P2.
05. Use lens gasket sealing method
For the sealing of the upper and lower covers, the sealing of the valve seat and the upper and lower valve bodies. If it is a flat seal, the sealing performance is poor under high temperature and high pressure, causing leakage. You can use lens gasket sealing instead, which can get satisfactory results.
06. Replace the sealing gasket
To date, most sealing gaskets still use asbestos sheets. At high temperatures, the sealing performance is poor and the service life is short, causing leakage. In this case, you can use spiral wound gaskets, "O" rings, etc., which are now adopted by many factories.
07. Tighten the bolts symmetrically and use thin gasket sealing method
In the "O" ring sealed regulating valve structure, when using thick gaskets with large deformation (such as spiral wound gaskets), if the compression is asymmetrical and the force is asymmetrical, it is easy to cause the seal to be damaged, tilted and deformed, seriously affecting the sealing performance.
Therefore, in the maintenance and assembly of this type of valve, the clamping bolts must be tightened symmetrically (note that they cannot be tightened at one time). It would be better if the thick gasket can be changed into a thin one, so that it is easy to reduce the inclination and ensure the seal.
08. Methods to increase the width of the sealing surface, stop the flat valve core from jumping when closing and reduce its leakage
Flat valve cores (such as valve plugs of two-position valves and sleeve valves) have no guide and guide curved surface in the valve seat. When the valve is working, the valve core is subjected to lateral force and leans from the inflow side to the outflow side. The larger the valve core matching clearance, the more serious this unilateral phenomenon is. In addition, deformation, eccentricity, or small chamfer of the valve core sealing surface (generally 30° chamfer for guidance), when it is close to closing, the chamfered end face of the valve core sealing surface is placed on the valve seat sealing surface, causing the valve core to jump when closing, or even not close in place, which greatly increases the valve leakage.
The simplest and most effective solution is to increase the size of the valve core sealing surface so that the minimum diameter of the valve core end face is 1 to 5 mm smaller than the valve seat diameter, with sufficient guiding effect to ensure that the valve core is guided into the valve seat and maintain good sealing surface contact.
Solutions to regulating valve vibration (8 methods)
01. Increasing stiffness method
For oscillation and slight vibration, the stiffness can be increased to eliminate or weaken it. For example, it is feasible to use a spring with high stiffness or use a piston actuator.
02. Increasing damping method
Increasing damping means increasing the friction against vibration. For example, the valve plug of the sleeve valve can be sealed with an "O" ring, and a graphite filler with greater friction can be used. This is still effective in eliminating or weakening slight vibration.
03. Increasing the guide size and reducing the fit clearance method
The guide size of the shaft plug valve is generally small, and the fit clearance of all valves is generally large, 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.
04. Change the shape of the throttling piece to eliminate resonance
Because the so-called vibration source of the regulating valve occurs at the throttling port with high-speed flow and rapid pressure changes, changing the shape of the throttling piece can change the vibration source frequency, which is easier to solve when the resonance is not strong.
The specific method is to turn the valve core surface by 0.5 to 1.0 mm within the vibration opening range. For example, a self-powered pressure regulating valve was installed near the family area of a factory. The resonance caused whistling, which affected the rest of the employees. After the valve core surface was turned by 0.5 mm, the resonance whistling sound disappeared.
05. Replace the throttling piece to eliminate resonance
The methods include:
Change the flow characteristics, change the logarithm to the linear, and the linear to the logarithm;
Change the valve core form. For example, change the shaft plug shape to a "V" groove valve core, and change the double-seat valve shaft plug type to a sleeve type;
Change the sleeve with a window to a sleeve with a small hole, etc.
For example, a DN25 double-seat valve in a nitrogen fertilizer plant often broke at the connection between the valve stem and the valve core. After we confirmed it was resonance, we changed the linear characteristic valve core to a logarithmic valve core and the problem was solved. Another example is a DN200 sleeve valve used in a laboratory of an aviation college. The valve plug rotated violently and could not be put into use. After changing the sleeve with a window to a sleeve with a small hole, the rotation disappeared immediately.
06. Replace the type of regulating valve to eliminate resonance
Regulating valves of different structural forms naturally have different natural frequencies. Replacing the type of regulating valve is the most effective way to fundamentally eliminate resonance.
A valve vibrates very strongly during use—strongly (in severe cases, the valve may be damaged), rotates strongly (even the valve stem may be broken or twisted), and produces strong noise (up to more than 100 decibels). As long as it is replaced with a valve with a larger structural difference, it will be effective immediately, and the strong resonance will disappear miraculously.
For example, a DN200 sleeve valve was selected for a new expansion project of a vinylon plant. The above three phenomena all exist. The DN300 pipeline will jump, the valve plug will rotate, the noise will be more than 100 decibels, and the resonance opening will be 20-70%. Considering the large resonance opening, after using a double-seat valve, the resonance disappears and the operation is normal.
07. Method to reduce cavitation vibration
For the cavitation vibration caused by the collapse of cavitation bubbles, it is natural to find a way to reduce cavitation.
The impact energy generated by the bubble burst does not act on the solid surface, especially the valve core, but is absorbed by the liquid. The sleeve valve has this feature, so the shaft plug type valve core can be changed to a sleeve type.
Take all measures to reduce cavitation, such as increasing the throttling resistance, increasing the pressure of the contraction port, and reducing the pressure by stages or in series.
08. Avoiding the vibration source wave impact method
The external vibration source wave impact causes the valve to vibrate, which is obviously what the regulating valve should avoid when it is working normally. If such vibration occurs, corresponding measures should be taken.
Solution to the high noise of the regulating valve
01. Eliminating the resonance noise method
Only when the regulating valve resonates, there is energy superposition and a strong noise of more than 100 decibels. Some show strong vibration and small noise, some have weak vibration and very loud noise; some have both large vibration and noise.
This noise produces a monotonous sound, and its frequency is generally 3000-7000 Hz. Obviously, eliminating resonance will naturally eliminate the noise.
02. Eliminate cavitation noise method
Cavitation is the main source of fluid dynamic noise. During cavitation, the bubble bursts to produce high-speed impact, causing strong turbulence in the local area and generating cavitation noise.
This noise has a wide frequency range and produces a rattling sound, which is 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.
03. Use thick-walled pipeline method
Using thick-walled pipes is one of the sound path processing methods. Using thin walls can increase the noise by 5 decibels, and using thick-walled pipes can reduce the noise by 0 to 20 decibels. The thicker the wall of the same pipe diameter, the larger the pipe diameter of the same wall thickness, the better the noise reduction effect.
For example, for DN200 pipes, when the wall thickness is 6.25, 6.75, 8, 10, 12.5, 15, 18, 20, and 21.5 mm, the noise can be reduced to -3.5, -2 (i.e. increase), 0, 3, 6, 8, 11, 13, and 14.5 decibels respectively. Of course, the thicker the wall, the higher the cost.
04. Use sound-absorbing materials
This is also a common and most effective way to deal with the sound path. Sound-absorbing materials can be used to wrap the noise source and the pipeline after the valve.
It must be pointed out that since noise will be transmitted over long distances through the flow of fluid, the effectiveness of eliminating noise ends where the sound-absorbing materials are wrapped and the thick-walled pipes are used.
This method is suitable for situations where the noise is not very high and the pipeline is not very long, because it is a more expensive method.
05. Series silencer 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 ratio before and after the valve.
The use of absorption-type series silencers can greatly reduce noise. However, from an economic point of view, it is generally limited to attenuation to about 25 decibels.
06. Soundproof box method
Use soundproof boxes, houses and buildings to isolate the noise source inside, so that the noise of the external environment is reduced to an acceptable range for people.
07. Series throttling method
In the case of high pressure ratio of the regulating valve (△P/P1≥0.8), the series throttling method is adopted, that is, the total pressure drop is dispersed on the regulating valve and the fixed throttling element behind the valve. If diffusers and multi-hole flow restrictors are used, this is the most effective way to reduce noise.
In order to obtain the best diffuser efficiency, the diffuser (the shape and size of the entity) must be designed according to the installation conditions of each piece, so that the noise level generated by the valve is the same as the noise level generated by the diffuser.
08. Choose low-noise valves
Low-noise valves are based on the gradual deceleration of the tortuous flow path (multi-holes, multi-grooves) of the fluid through the valve core and the valve seat to avoid supersonic speed at any point in the flow path. There are various forms and structures of low-noise valves (designed for special systems) for selection when used.
When the noise is not very loud, the low-noise sleeve valve can be used to reduce the noise by 10 to 20 decibels. This is the most economical low-noise valve.
Solutions for poor stability of regulating valves
01. Changing the direction of unbalanced force
In stability analysis, it is known that when the unbalanced 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 unbalanced force conditions, the method of changing its direction of action is usually to change the flow-closed type to the flow-open type. Generally speaking, it can easily solve the stability problem of the valve.
02. Avoid working in the unstable area of the valve itself
Some valves are limited by their own structure and have poor stability when working at certain openings.
For double-seat valves, the opening is within 10%, because the upper ball flows open and the lower ball flows closed, which brings instability problems; near the alternating slope of the unbalanced force change, its stability is poor. For example, the alternation point of the butterfly valve is about 70 degrees; the double-seat valve is at 80-90% opening. When encountering such valves, working in the unstable area will inevitably lead to poor stability, so just avoid working in the unstable area.
03. Replace valves with good stability
The unbalanced force of valves with good stability changes less and has good guidance. Among the commonly used ball valves, sleeve valves have this major feature.
When the stability of single-seat and double-seat valves is poor, replacing them with sleeve valves will definitely improve the stability.
04. Increase spring stiffness method
The ability of the actuator to resist the influence of load changes on the stroke depends on the spring stiffness. The greater the stiffness, the smaller the influence on the stroke and the better the valve stability.
Increasing spring stiffness is a common and simple method to improve valve stability, such as changing the spring in the range of 20 to 100KPa to a high-stiffness spring of 60 to 180KPa. This method is mainly used for valves with positioners. Otherwise, the valve used must be equipped with a positioner.
05. Reduce the response speed method
When the system requires the control valve to respond or adjust the speed should not be too fast, the valve response and adjustment speed are fast, such as the flow needs to be fine-tuned, but the flow adjustment of the control valve changes greatly, or the system itself is a fast response system and the control valve has a positioner to speed up the action of the valve, which is unfavorable.
This will produce overshoot, vibration, etc. For this, the response speed should be reduced.
The methods are:
Change the linear characteristic to a logarithmic characteristic;
The positioner can be changed to a converter or relay.
Other troubleshooting of the control valve
01. Change the flow direction, solve the problem of promoting closing, and eliminate the surge method
To improve the cutting effect, the two-position valve is usually used as a flow-closing type. For liquid media, due to the unbalanced force of the flow-closing type, the valve core is pressed closed, which has a promoting closing effect, also known as a suction effect, which speeds up the valve core action speed, produces a slight water hammer, and causes system surge.
The solution to the above phenomenon is to change the flow direction to flow open, and the surge can be eliminated. Similar problems such as the valve not being able to work properly due to the promotion of closing can also be solved by this method.
02. Methods to prevent plastic deformation
Plastic deformation causes one metal surface to scratch the metal surface of another part, or even stick together, causing valve jamming, poor operation, sealing surface dragging, increased leakage, and two threaded parts biting and unable to rotate (such as the upper and lower valve bodies of high-pressure valves).
Plastic deformation is related to temperature, matching materials, surface roughness, hardness and load. High temperature anneals or softens the metal, further aggravating the plastic deformation trend.
Methods to solve valve failures caused by plastic deformation include:
Use high-hardness materials for easily scratched parts, with a hardness difference of 5 to 10 Rc;
Use different materials for the two parts;
Increase the gap;
Add lubricant;
Repair the damaged surface to improve the finish and hardness:
When the thread bites and cannot be rotated, it has to be welded once.
01. Adding sealing grease
When the flow coefficient of the valve is too small due to inaccurate calculation or increased production, and the valve cannot guarantee the flow even when fully opened, the bypass has to be opened to pass part of the flow. Usually the bypass flow is less than 15-20% of the maximum flow.
Here is a way to open the bypass: because the flow resistance of the closed type is small, it is 10-15% larger than the flow coefficient of the open type. Therefore, the flow direction can be changed to change the usual flow open to flow closed, even if the valve passes 10-15% more flow. This can avoid opening the bypass, and because it works at a large opening, the stability problem can be ignored.
04. Overcoming fluid damage method
The most typical valve 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 in two streams, upper and lower.
The fluid impacts the valve core, causing it to lean towards the outlet side, causing friction, damaging the guide surface of the valve core and the bushing, resulting in abnormal operation. High flow may also cause the valve core to bend, erode, and even break in severe cases.
Solution:
Increase the hardness of the guide material;
Increase the size of the middle of the upper and lower balls of the valve core to make it thick;
Use other valves as a substitute. If a sleeve valve is used, the fluid flows in from all sides of the sleeve, and the lateral thrust on the valve plug is greatly reduced.
05. Methods to overcome the rotational force generated by the fluid to rotate the valve core
For the valve core with a "V"-shaped port, due to the asymmetry of the medium inflow, the tangential force of the valve core acting on the "V"-shaped port is inconsistent, generating a rotational force that causes it to rotate. Especially for valves with DN ≥ 100, it is stronger.
As a result, the valve may be disconnected from the actuator push rod, and the springless actuator may cause the diaphragm to twist.
The solutions are:
Rotate the valve core in the opposite direction of rotation to balance the tangential force acting on the valve core;
Further lock the connection between the valve stem and the push rod, and add an anti-rotation clamp if necessary;
Replace the valve core with a "V"-shaped opening with a plunger-shaped valve core;
Use or change to a sleeve-type structure;
If the rotation is caused by resonance, eliminating the resonance can solve the problem.
06. Adjust the friction of the butterfly valve plate to overcome the opening jump method
When the butterfly valve is closed with soft seals such as "O" rings, sealing rings, and linings, the valve plate is closed in place and wrapped around the valve plate due to the deformation of the soft seal, which can achieve a very ideal cutting effect.
However, when the valve is to be opened, the force of the actuator to open the valve plate continues to increase. When it increases to the same friction force as the soft seal on the valve plate, the valve plate starts. Once started, this friction force decreases sharply.
In order to achieve force balance, the valve plate opens violently. When the unbalanced torque of the medium acting on the corresponding opening is balanced with the opening torque of the actuator, the valve stops at this opening. This violent and sudden opening can be as high as 30-50%, which will cause a series of problems.
At the same time, the soft seal will undergo a large change when closing, which may cause permanent deformation or be squeezed or stretched by the valve plate, affecting its life.
The solution is to adjust the friction of the soft seal on the valve plate start, which can not only ensure the required cut-off requirements, but also enable the valve to start more normally.
The specific methods are:
Adjust the interference;
Reduce the difficulty of opening caused by excessive closing of the valve plate by limiting or adjusting the preload and output force of the actuator.