How to deal with valve blockage

1. Welding slag, rust, slag, etc. in the cleaning method pipeline cause blockage or jam in the throttle, guide part, and balance hole of the lower bonnet, resulting in strains and scratches on the curved surface of the valve core, the guide surface, and the sealing surface. Indentation, etc. This often occurs with new commissioning systems and in the early stages of commissioning after major repairs. This is the most common failure. In this case, it must be disassembled for cleaning to remove the slag. If the sealing surface is damaged, it should be ground. At the same time, the bottom plug should be opened to flush out the slag falling into the lower valve cover from the balance hole, and the pipeline should be cleaned. Rinse. Before putting into operation, let the regulating valve fully open, and the medium will flow for a period of time before it is brought into normal operation. 2. External flushing method When using ordinary valves to regulate some media that are easy to precipitate and contain solid particles, the throttle or guide is often blocked, and the flushing gas and steam can be externally connected to the bottom plug of the lower valve cover. When the valve is blocked or stuck, open the external gas or steam valve to complete the flushing work without moving the regulating valve, so that the valve can operate normally. 3. Installation of pipeline filter method For small-diameter control valves, especially ultra-small flow control valves, the throttling gap is extremely small, and there can be no slag in the medium. In case of blockage, it is best to install a filter on the pipeline in front of the valve to ensure the smooth passage of the medium. For the regulating valve used with the positioner, the positioner does not work properly, and the blockage of its gas path orifice is the most common fault. Therefore, when working with a positioner, the air source must be handled properly. The usual method is to install an air filter pressure reducing valve on the air source pipeline in front of the positioner. 4. Increase the throttling gap method, such as solid particles in the medium or in the pipeline If the flushed welding slag and rust cannot pass through the throttling port and cause blockage or jamming, etc., a throttling piece with a large throttling gap can be used instead. Because the throttling area is concentrated rather than circumferentially distributed, the fault can be easily eliminated. If it is a single or double seat valve, the plunger-shaped valve core can be changed to a 'V'-shaped valve core, or a sleeve valve, etc. For example, a double-seat valve in a chemical plant is often stuck. After recommending to use a sleeve valve, the problem is solved immediately. 5. The medium flushing method uses the flushing energy of the medium itself to flush and take away the things that are easy to precipitate and block, thereby improving the anti-blocking function of the valve. The common methods are: ① Change to flow-closed type; ② Use streamlined valve body; ③ Place the throttle port at the most severe erosion point, and pay attention to improving the erosion resistance of the throttling material when using this method. 6. The straight-through is changed to the angle method. The straight-through is inverted S flow, the flow path is complicated, and the upper and lower chambers have many dead zones, which provides a place for the sedimentation of the medium. Angular connection, the medium seems to flow through the 90 ℃ elbow, the scouring performance is good, the dead zone is small, and it is easy to be designed into a streamline shape. Therefore, when the straight-through regulating valve is slightly blocked, it can be changed to an angle valve.
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