The automatic control valve relies on the pressure and temperature of the medium flowing through the valve as the energy to drive the valve to work automatically, and does not need external power supply and auxiliary instruments. Also known as self operated control valve. The automatic control valve uses the feedback signal (pressure, differential pressure, temperature) of the valve output end to transmit the valve to the actuator, and drives the valve disc to change the valve opening to achieve the purpose of regulation. Pressure, flow and temperature. Self regulating valve is a new type of regulating valve. Compared with the manual control valve, it has the advantage of automatic adjustment, compared with the electric control valve, it has the advantage of no external power. The application practice shows that in the closed water circulation system (such as hot water heating system, air conditioning chilled water system), the correct use of the valve can easily realize the flow distribution of the system and realize the dynamic balance of the system. The system can greatly simplify the debugging work and stabilize the working state of the pump. In the process of daily use, the automatic control valve will appear paper jam and other problems. However, these problems will lead to the performance degradation of the self operated control valve. How to prevent automatic control valve from blocking? There are six ways to solve and avoid the problem: 1. Cleaning method: the welding slag, rust and slag in the pipeline are all in the balance hole of throttle valve, guide part and lower valve cover, causing blockage or blockage, resulting in bending of valve core and guide surface, and strain and scratch on the surface. In this case, the slag must be removed for cleaning. If the sealing surface is damaged, it should be ground. At the same time, the bottom plug should be opened to clean the slag hole falling from the balance into the lower valve cover, and the pipe should be flushed. Before debugging, let the control valve open completely, and the medium will enter the normal operation state after a period of time. 2. External flushing method: when ordinary valves regulate some media that are easy to precipitate and contain solid particles, they are usually blocked at the throttle valve and guide device, and gas and steam can be flushed at the bottom of the lower valve cover. When the control valve is blocked or blocked, open the external gas or steam valve to complete the flushing operation without moving the control valve to make the valve operate normally. 3. Installation of pipeline filtration: for small diameter control valve, especially ultra-small flow control valve, the throttling clearance is very small, even if there is a small amount of slag in the medium, it will be blocked. It is better to install a pipe in front of the valve. Filtration to ensure smooth passage of media. Using the control valve used by the positioner, the positioner can not work normally, and the blockage of the airway throttle valve is the most common fault. 4. Method of increasing throttle clearance: due to the throttle valve, the solid particles or slag and rust in the medium washed out in the pipeline can not be blocked or stuck, and the part with large throttle clearance can be used. Flow element - throttling area is window, open spool and sleeve. Since the throttling area is concentrated rather than circumferentially distributed, the fault can be eliminated easily. If it is a single seat or double seat valve, the plunger valve core can be replaced with a "V" shaped valve core or a sleeve valve. 5. The medium flushing method uses the flushing energy of the medium itself to flush and take away the articles that are easy to precipitate and block, so as to improve the anti blocking function of the valve. The common methods are as follows: 1. Change to flow type; 2. Adopt streamlined valve body; 3. Put the throttle on the most powerful part of flushing. This method should pay attention to improve the corrosion resistance of throttle parts. 6. Straight through is changed to angle method: straight through is inverted s flow, the flow path is complex, and there are many dead zones in the upper and lower chambers, providing a space for precipitation. Mediu meter angle connection, the medium is like flowing through 90 ° C elbow, good scouring performance, small dead zone, easy to design into streamline.