Currently, commonly used in engineeringControl valvemainly:The electromagnetic valve和Electric valve.However, they all have defects in use, such as solenoid valves are easy to be blocked by foreign objects, water resistance is large, and long-term dedicated maintenance is required. Although electric valves have no water resistance, they need necessary control circuits, so they are affected by water vapor corrosion. Service life is also the main problem that plagues promotion.
Second, how to overcome the impact of scale on the use of valves to the greatest extent
Whether it is a solenoid valve or an electric valve, scale will not only cause valve leakage, but even affectvalveThe normal work of the industry, so how to eliminate the influence of scale has been a problem of general concern in the industry.
The scope of the control valve process is too wide, and I can't explain it to you one by one here. I hope that the content of this aspect can be checked by myself.However, the poor performance of the control valve due to the difference in the design of the actuator and the use of filling materials can be summarized as follows: 1. The existence of a dead zone in 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, wandering, torsion of valve shaft, dead zone of amplifier.Various control valves are not the same as sensitive to friction. For example, rotary valves are very sensitive to friction caused by high seat load, so pay attention to this when using.But for some seal types, high seat load is necessary to obtain the closing level.In this way, the design of this kind of valve is very poor, and it is easy to cause a large dead zone. The effect of this on the process deviation is obvious and is simply decisive. ②Abrasion.It is inevitable that the valve wears during normal use, but the wear of the lubricating layer is the most severe.In addition, the load caused by pressure will also cause the wear of the sealing layer, which are the main factors leading to the increase of friction.The result is a devastating effect on the performance of the control valve ③, the friction of the filler is the main source of friction of the control valve, and the friction caused by different fillers is very different. ④ Different types of actuators also have a fundamental impact on friction. Generally speaking, spring film actuators are better than piston actuators.
Third, the design problem of the locator
From the initial thinking of design, the design of actuator and positioner must be considered together.How to design a good positioner? Know from its important characteristics, it must be a high gain device.The gain is composed of two parts: static gain and dynamic gain.The way to increase the static gain is to design a preamplifier.For example, nozzle-baffle device.So some friends would like to ask how to obtain the dynamic gain? It is obtained through a power amplifier, which is a spool valve (general).A high-performance positioner with both high static and high dynamic gains can provide the best overall performance in terms of reducing process deviations for any given valve assembly.