Our goal: to be a high-quality manufacturer of industrial control valves, gaining unanimous recognition from new and old customers
Our mission: To fully utilize the effectiveness of industrial control valves to achieve better results
Cleaning method
Welding slag, rust, slag, etc. in the pipeline cause blockage or jamming in the throttle port, 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 during the initial stages of commissioning of new systems and after major repairs. This is a common fault. In this case, it must be disassembled and cleaned to remove 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 fell into the lower valve cover from the balance hole, and flush the pipeline. Before putting into operation, fully open the regulating valve and allow the medium to flow for a period of time before bringing it into normal operation.
External scouring method
When using ordinary valves to regulate media that are prone to precipitation and contain solid particles, they often block the throttle and guide ports, and can be externally connected with flushing gas and steam at the bottom plug of the lower valve cover. When the valve is blocked or jammed, open the external gas or steam valve to complete the flushing work without moving the regulating valve and ensure the normal operation of the valve.
Pipeline installation
For small diameter control valves, especially ultra small flow control valves, their throttle clearance is extremely small, and there should be no small amount of debris in the medium. In case of blockage, install a filter on the pipe in front of the valve to ensure smooth passage of the medium. A common failure of a regulating valve with a positioner is that the positioner does not work properly and its gas path throttle is blocked. Therefore, when working with a positioner, it is necessary to properly handle the air source. The usual method is to install an air filter pressure reducing valve on the air source pipeline in front of the positioner.
Increase throttle clearance
If solid particles in the medium or welding slag and rust that have been washed away in the pipeline cannot pass through the throttle opening, resulting in clogging, jamming, and other failures, it is possible to replace them with throttling elements with large throttling clearance - valve cores and sleeves with window and opening throttling areas. Due to their concentrated throttling areas rather than circumferential distribution, the failure can be easily eliminated. If it is a single or double seat valve, you can change the plunger shaped valve core to a "V" shaped valve core, or change it to a sleeve valve. For example, in a chemical plant, there is a double seat valve that often gets stuck. It is recommended to use a sleeve valve instead, and the problem is immediately resolved.
Medium scouring method
Utilize the scouring energy of the medium itself to flush and remove things that are prone to sedimentation and clogging, thereby improving the anti clogging function of the valve. Common methods include: ① switching to the flow closed type; ② Adopt streamlined valve body; ③ When using this method, attention should be paid to improving the erosion resistance of the throttle material.
Straight to angular
The straight flow is an inverted S flow, with complex flow paths and many dead zones in the upper and lower chambers, providing a place for medium precipitation. Angular connection, medium like flowing through 90 elbows, good scouring performance, small dead zone, easy to design into a streamlined shape. Therefore, when using a straight-through regulating valve to cause slight blockage, it can be changed to an angle valve for use at ℃.
Increase clearance
"If the gap between the valve core and sleeve is too small, or if different materials are used, sleeve regulating valves used on steam pipelines may be blocked by heat due to different expansion coefficients.". It is possible to appropriately increase the clearance during machining (on the premise of meeting the flow control requirements) to prevent similar situations from occurring.
resolvent
1) Grinding method
Fine grinding can eliminate traces, reduce or eliminate sealing gaps, and improve the smoothness of sealing surfaces to improve sealing performance.
2) Using unbalanced force to increase sealing specific pressure method
The sealing pressure generated by the actuator on the valve core is constant. When the unbalanced force produces a jacking open trend on the valve core, the sealing force of the valve core decreases with the two forces. On the contrary, the sealing force of the valve core increases with the two forces added together, which greatly increases the sealing specific pressure, and the sealing effect can be increased by 5 to 10 times compared to the former. Generally, single seal valves with dg ≥ 20 are the former case, usually of the flow open type, If the sealing effect is considered unsatisfactory, the sealing performance will be multiplied by changing to the flow closed type. In particular, the two-position shut-off regulating valve should generally be used as a flow closed type.
3) Method of improving sealing force of actuator
Improving the sealing force of the actuator to the valve core is also a common method to ensure valve closure, increase sealing specific pressure, and improve sealing performance. Common methods include:
① Moving the working range of the spring;
② Use a small stiffness spring instead;
③ Add accessories, such as a positioner;
④ Increase the air supply pressure;
⑤ Switch to an actuator with greater thrust.
4) Adopt single seal and soft seal method
For regulating valves with dual seals, a single seal can be used instead, which can generally improve the sealing effect by more than 10 times. If the imbalance force is large, corresponding measures should be added. For hard sealed valves, a soft seal can be used instead, which can also improve the sealing effect by more than 10 times.
5) Switch to a valve with good sealing performance
In case of necessity, it is advisable to consider switching to valves with better sealing performance. For example, ordinary butterfly valves can be switched to elliptical butterfly valves, and further switching to shut-off butterfly valves, eccentric rotary valves, ball valves, and specially designed shut-off valves can also be used.
Solution for leakage
1) Method of adding sealing grease
For valves that do not use sealing grease, consider adding sealing grease to improve the sealing performance of the valve stem.
2) Adding filler method
To improve the sealing performance of the packing on the valve stem, the method of adding packing can be adopted. Usually, double or multi-layer mixed fillers are used, and simply increasing the quantity, such as increasing 3 to 5 pieces, does not have a significant effect.
3) Replacement of graphite packing method
A large number of tetrafluoro fillers are used, because their operating temperature is within the range of - 20 to+200. When the temperature is within the upper and lower limits, and changes greatly, their sealing performance significantly decreases, resulting in rapid aging, and short service life. Flexible graphite fillers can overcome these shortcomings and have a long service life. Therefore, some factories have changed all tetrafluoro packing to graphite packing, and even newly purchased control valves have replaced the tetrafluoro packing with graphite packing for use. However, the use of graphite fillers has a large return difference, and some of them also produce creeping phenomenon at the beginning, which must be considered.
4) Change the flow direction and place P2 on the valve rod end
When △ P is large and P1 is large, it is obviously more difficult to seal P1 than to seal P2. Therefore, the method of changing the flow direction can be adopted, changing P1 from P2 at the valve rod end to P2 at the valve rod end, which is more effective for valves with high pressure and large differential pressure. For example, sealing P2 should generally be considered for bellows valves.
5) Using the lens pad sealing method
For the sealing of the upper and lower covers, as well as the sealing of the valve seat and the upper and lower valve bodies, if it is a planar seal, under high temperature and pressure, the sealing performance is poor, causing leakage. Therefore, it can be replaced with a lens gasket seal, which can achieve satisfactory results.
6) Replace sealing gasket
Most sealing gaskets still use asbestos sheets, which can cause leakage due to poor sealing performance and short service life at high temperatures. In this case, spiral wound gaskets, "O" rings, etc., can be used instead, and many factories have adopted them.
Vibration solution
1) Increasing stiffness method
"For oscillations and slight vibrations, it is possible to increase the stiffness to eliminate or weaken them, such as selecting a spring with a large stiffness, and switching to a piston actuator.".
2) Increased damping method
Increasing damping means increasing friction against vibration. For example, the valve plug of a sleeve valve can be sealed with an "O" ring, and graphite packing with high friction can be used. This can still have a certain effect on eliminating or weakening slight vibration.
3) Increase guide size and reduce fit clearance method
Shaft plug valves generally have smaller guide dimensions, and all valves have larger fit clearances, ranging from 0.4 to 1mm, which is helpful for generating mechanical vibration. Therefore, when slight mechanical vibration occurs, vibration can be reduced by increasing the guide dimension and reducing the fit clearance.
4) Changing the shape of the throttle element and eliminating resonance
Because the so-called vibration source of the regulating valve occurs at the throttle port with high-speed flow and sharp pressure changes, changing the shape of the throttle element can change the vibration source frequency, which is relatively easy to solve when the resonance is not strong. The specific method is to turn the valve core curved surface within the vibration opening range by 0.5~1.0mm. For example, a self operated pressure regulating valve was installed near the family area of a factory, and the resonance generated a howl that affected the rest of employees. After we dropped the valve core curved surface 0.5 mm, the resonance howl disappeared.
