Preventing sticking or clogging of control valves and troubleshooting methods

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　　During use, control valves can sometimes get stuck or clogged due to the properties of the medium flowing through them, preventing them from functioning properly. In such cases, it is necessary to prevent this from happening or to take action to resolve the issue. Several methods are outlined below for reference only. 　　1) Cleaning method 　Slag, rust, and debris in the pipelines can cause blockages or jams at the throttle ports, guide sections, and balance holes of the lower valve cover, leading to scratches and abrasions on the surface of the valve core and guide surfaces, as well as indentations on the sealing surfaces. This often occurs in newly commissioned systems and in the early stages after major repairs. This is the most common fault. In such cases, it is necessary to remove the component for cleaning in order to get rid of debris; if the sealing surface is damaged, it should also be ground ； At the same time, open the bottom plug to flush out the debris that has fallen from the balance hole into the lower valve cover, and to clean the pipelines. Before putting it into operation, open the control valve fully; allow the medium to flow for a while before proceeding with normal operation. 　　2) External flushing method: When using ordinary valves to regulate media that tend to precipitate and contain solid particles, blockages often occur at the throttling ports and guide areas; in such cases, flushing gas and steam can be introduced at the bottom plug of the lower valve cover. When the valve becomes clogged or stuck, opening the external gas or steam valve allows for flushing to be carried out without moving the control valve, thereby restoring normal operation of the valve. 　　3) Pipe filter installation method: For small-diameter control valves, especially those with extremely low flow rates, the throttling gap is very small; therefore, there must not be any debris in the fluid. In the event of such blockage, it is best to install a filter on the pipeline before the valve to ensure smooth flow of the medium. For control valves used with positioners, when the positioner does not function properly, the most common fault is a blockage in the air circuit throttle. Therefore, when a regulator is in use, it is necessary to take proper care of the air supply; a common approach is to install an air filter and pressure reducing valve on the air supply pipeline before the regulator. 4) Increasing the throttling gap: If solid particles in the medium, or welding slag and rust that have been washed into the pipes, cause blockages or jams due to their inability to pass through the throttling opening, it is possible to use throttling elements with larger throttling gaps – valve cores or sleeves with window-like or open-shaped throttling areas. Since the throttling area in these cases is concentrated rather than distributed around the perimeter, such problems can be easily resolved. For single or double-seat valves, the plunger-type valve core can be replaced with a valve core having a “V”-shaped port, or it can be changed to a cartridge valve or similar. For example, a chemical plant had a two-seat valve that would get stuck frequently; after it was recommended to replace it with a sleeve valve, the problem was resolved immediately. 　　5) Medium scouring method: Utilizing the scouring energy of the medium itself to wash away and remove substances that tend to precipitate or cause blockages, thereby enhancing the valve’s resistance to blockages. Common methods include: ① modifying it for use in a flow-closed configuration ； ②Use a streamlined valve body ； ③Place the throttle orifice at the most severely eroded area; when using this method, it is important to enhance the erosion resistance of the material used for the throttle component. 　　6) Change from straight-through to corner flow method: The straight-through configuration results in an inverted S-shaped flow pattern; the flow path is complex, with numerous dead zones in the upper and lower chambers, which provide areas for the deposition of the medium. Angular connection: the medium flows as if through a 90° elbow, offering good scouring performance, a small dead zone, and allowing for easy design in a streamlined shape. Therefore, when a slight blockage occurs with a straight-through control valve, it can be replaced with an angle valve.