Brief description of the selection technique of the control valve (regulating valve)

First, the choice of control valve (regulation valve)
At present, the control valves commonly used in engineering are mainly: solenoid valves and electric valves. However, they all have defects in use. For example, the solenoid valve is easily blocked by foreign matter, the water resistance is large, and it must be maintained by a long-term person. However, although the electric valve has no water resistance, it has the necessary control circuit, so the influence of waterproof steam erosion Service life is also a major problem that plagues promotion.
Second, how to maximize the impact of scale on the use of valves
Whether it is a solenoid valve or an electric valve, scale will not only cause valve leakage, but also affect the normal operation of the valve in severe cases, so how to eliminate the impact of scale is a common concern in the industry. The scope of the control valve process is too wide, and you can't make it clear here. I hope that the content of this aspect is also personally checked the information. However, due to the poor performance of the control valve due to the difference between the design actuator and the use of the filling material, the regularity can be summarized: 1. The presence of the dead zone during the process will cause the process variable to deviate from the original set point. Therefore, the output of the controller must be increased enough to overcome the dead zone, and only this corrective action will occur. 2, 1 the main factors affecting the dead zone. Friction, migration, valve shaft torsion, dead zone of the amplifier. Various control valves are not sensitive to friction. For example, rotary valves are very sensitive to friction caused by high seat loads, so note this when using them. However, for some seal types, a high seat load is necessary to achieve a shut down rating. In this way, the design of the valve is very poor, and it is easy to cause a large dead zone. The effect on the process deviation is obvious and it is decisive. 2 wear. It is inevitable that the valve will wear out during normal use, but the wear of the lubricating layer is the most powerful. In addition, the load caused by the pressure can also cause the wear of the sealing layer, which is the main factor that causes the friction to increase. The result is a devastating effect on the performance of the control valve. 3. The friction of the packing is the main source of the friction of the control valve. The friction used varies greatly depending on the packing used. 4, the type of actuator also has a fundamental impact on friction, in general, the spring film actuator is better than the piston actuator.
Third, the design problem of the positioner
From the initial thinking of the design, the actuator and locator design must be considered together. How to design a good locator? From his important characteristics, it must be a high gain device. The gain is made up of two parts: static gain and dynamic gain. The way to increase the static gain is to design a preamplifier. For example, the nozzle - the baffle device. So a friend asks how to get the dynamic gain? It is obtained through a power amplifier, which is a slide valve (generally). High-performance positioners with high static and high dynamic gain provide the best overall performance for any given valve assembly with reduced process variation.