common problem:
overcome scale
Regardless of 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. Therefore, how to remove the impact of scale has become a common concern of the industry.
The scope of the solenoid valve process is too wide, but the poor performance of the control valve due to the difference in the design of the actuator and the use of filling materials can still be summarized.
1. The existence of the dead zone in the process will cause the process variable to deviate from the original set point. So the output of the controller must be increased enough to overcome the dead zone, and only this corrective action will take place.
2. ① The main factors affecting the dead zone: friction, wandering, valve shaft torsion, and the dead zone of the amplifier. Various control valves vary in friction, but for some seal types, high seat loads are necessary to obtain shutoff ratings. , This kind of valve is designed to easily cause a large dead zone, which has an obvious and decisive impact on the process deviation.
② wear and tear. It is inevitable that the valve will be worn during normal use, but the wear of the lubricating layer is severe. According to the experiment, the lubricating rotary valve only goes through hundreds of cycles, and the lubricating layer can almost be used by a brush. In addition, the load caused by the pressure will also cause the wear of the sealing layer, which is the main factor leading to the increase of friction. The result? It is devastating to the performance of the control valve!
③Friction of packing is the main source of friction of control valve. Different packings are used, resulting in great difference in friction.
④ Different types of actuators also have a fundamental impact on friction, and spring-diaphragm actuators are better than piston actuators.
