1)Cleaning methodWelding slag, rust, slag and so on in the pipeline will cause blockage or jam in the throttle, the guiding part and the balance hole of the lower valve cover, which will cause strain and scratch on the curved surface of the valve core and the guiding surface, and indentation on the sealing surface and so on. This often happens when the new system is put into operation and the initial stage after overhaul. This is the most common fault. In this case, it must be removed for cleaning, and the slag should be removed. If the sealing surface is damaged, it should also be grinded; at the same time, the underplug should be opened to wash away the slag falling from the balance hole into the lower valve cover, and wash the pipeline. Before being put into operation, let the regulating valve be fully open and the medium flow for a period of time before being brought into normal operation.
2)External scour methodWhen the medium which is easy to precipitate and contains solid particles is adjusted by the ordinary valve, it is often blocked at the throttle and the guide, and the scour gas and steam can be external at the bottom plug of the lower valve cover. When the valve is blocked or stuck, open the external gas or vapor valve, and the flushing work can be completed without moving the regulating valve, making the valve run normally.
3)Pipe filter installation methodFor small-caliber regulating valve, especially the ultra-small flow regulating valve, the throttling gap is extremely small, and there should be no little residue in the medium. In case of blocking in this situation, it is better to install a filter on the pipeline in front of the valve to ensure the smooth passage of the medium. As for the regulating valve with the locator, the locator does not work normally, and its gas circuit throttle is blocked, which is the most common fault. Therefore, when working with the locator, the air source must be handled well, and the usual method is to install the air filter pressure reducing valve on the air source pipe line in front of the locator.
4)Method of increasing throttle gapFor example, the solid particles in the medium or the welding slag and rust which are washed out in the pipeline will be blocked and stuck due to failure to pass through the throttle, the throttle with large throttle gap can be used instead-the valve core and sleeve whose throttle area is of open window and open type. Because the throttle area is concentrated rather than distributed in a circle, the fault can be easily eliminated. If it is single or double valve, the plunger-shaped valve core can be changed into "V"-shaped valve core or sleeve valve, etc. For example, a double-seat valve in a chemical plant often gets stuck. It is recommended to switch to the sleeve valve, and the problem will be solved immediately.
5)Medium scour methodUse the scour energy of the medium itself to scour and take away the things which are easy to precipitate and block, so as to improve the anti-blocking function of the valve. The common methods are: ① change to flow-closed type; ② use streamlined valve body; ③ place the throttle at the place where the erosion is the most severe, and pay attention to improve the erosion resistance of the throttle material when adopting this method.
6)Straight to angular methodStraight-through is an inverted S flow with complex flow path and many dead zones in the upper and lower cavity, which provides a place for the precipitation of the medium. Angular connection, the medium is like flowing through 90 elbow, with good scouring performance and small dead zone, which is easy to be designed as flowing line. Therefore, when the straight-through regulating valve is used to cause slight congestion, it can be changed into an angle valve for ℃.
Five Solutions to poor sealing performance:
1)Grinding methodFine Grinding can eliminate traces, reduce or eliminate the sealing clearance, and improve the smoothness of the sealing surface to improve the sealing performance.
2)Using Unbalanced Force to increase the sealing pressure methodThe sealing pressure produced by the actuator to the valve core is fixed, and when the unbalance force causes the push-open trend to the valve core, the sealing force of the valve core is reduced by two forces, otherwise, the pressure-close trend is generated to the valve core, the sealing force of the valve core is the addition of two forces, which greatly increases the sealing pressure, and the sealing effect can be improved by 5 ~ More than 10 times. generally, the single-seal valve with dg ≥ 20 is in the former case, which is usually flow-open type. If the sealing effect is not satisfied, it will be changed to flow-closed type, and the sealing performance will increase exponentially. especially the two-position cutting-off regulating valve, generally should be used according to the flow-closed type.
3)Method of improving the sealing force of actuator
Improving the sealing force of the actuator to the valve core is also a common method to ensure the closing of the valve, increase the sealing pressure and improve the sealing performance. Common methods are:
① Working range of moving spring;
② Use small stiffness spring instead;
③ Add accessories, such as with locator;
④ Increase air source pressure;
⑤ Switch to the actuator with greater thrust.
4)Adopt single seal, soft seal methodThe regulating valve used for double seal can be changed to single seal, which can usually improve the sealing effect by more than 10 times. If the unbalance force is relatively large, corresponding measures should be added, the hard sealed valve can be changed to soft seal, which can improve the sealing effect by more than 10 times.
5)Switch to valve with good sealing performanceIn the case of necessity, we can consider to use the valve with better sealing performance. for example, change ordinary butterfly valve to Oval butterfly valve, and then change to cut-off butterfly valve, eccentric rotation valve, ball valve and specially designed cut-off valve.
Six solutions to the release of regulating valve:
1)Adding seal grease methodFor valves without sealing grease, we can consider adding sealing grease to improve the sealing performance of valve stem.
2)Adding stuffing methodIn order to improve the sealing performance of stuffing to the valve stem, the method of adding stuffing can be adopted. Usually it adopts the form of double-layer and multi-layer mixed stuffing, simply increasing the quantity, such as increasing 3 pieces to 5 pieces, the effect is not obvious.
3)Replacement of graphite stuffing methodThe extensive use of Teflon stuffing, because its working temperature is-20 ~ Within the range of 200, when the temperature changes greatly at the upper and lower limits, its leakproofness decreases obviously, with fast aging and short service life. Flexible graphite stuffing can overcome these shortcomings and has long service life. Therefore, some factories all change the Teflon stuffing into graphite stuffing, and even the newly purchased regulating valve also change the Teflon stuffing into graphite stuffing for use. However, the return of using graphite stuffing is large, and at the beginning, some crawling phenomenon occurs, which must be taken into consideration. ℃
4)Change flow direction, The method of setting P2 at the end of the valve when △p is larger and P1 is larger, 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 rod end of the valve to P2 at the rod end of the valve, which is relatively effective for the valve with high pressure and high differential pressure. for example, Bellows valve should generally consider sealing P2.
5)Adopt transparent cushion sealing methodFor the sealing of upper and lower cover, the sealing of valve seat and upper and lower valve body. if it is a flat seal, under high temperature and high pressure, the tightness is poor, which causes leakage, you can use a lens pad to seal, which can get a satisfactory effect.
6)Replace the sealing gasketUp to now, most of the sealing gaskets still use asbestos board. Under high temperature, the sealing performance is poor and the service life is short, which causes leakage. In this case, the winding gasket, "O" ring and so on can be used instead, which has been adopted by many factories now.
Four solutions to the vibration of regulating valve:
1)Increase stiffness methodFor oscillation and slight vibration, the stiffness can be increased to eliminate or weaken. For example, it is feasible to choose spring with high stiffness and switch to piston actuator.
2)Adding damping methodIncreasing damping means increasing the friction to vibration. For example, the valve plug of sleeve valve can adopt "O" ring seal, and adopt graphite stuffing with larger friction, etc, this has some effects on eliminating or weakening slight vibration.
3)Method of increasing the guiding size and reducing the fit gapGenerally, the guiding size of shaft plug-type valve is small, and the fit clearance of all valves is usually large, with 0.4 ~ Lmm, which is helpful for generating mechanical vibration. Therefore, when slight mechanical vibration occurs, the vibration can be weakened by increasing the guiding size and reducing the fit clearance.
4)Change the shape of throttle and eliminate resonance methodBecause the so-called vibration source of the regulating valve occurs at the throttle with high-speed flow and sharp changes in pressure, changing the shape of the throttle can change the frequency of the vibration source, which is easier to solve when the resonance is not strong. The specific method is to turn the surface of the valve core within the vibration opening range by 0.5 ~ 1.0mm For example, a self-supporting pressure regulating valve is installed near the family area of a factory, and the noise caused by resonance affects the rest of workers. After we drop the valve core curved car by 0.5mm, the noise of resonance will disappear.
