The welding slag, rust, and debris in the pipeline can cause blockage or jamming at the throttle port, guide position, and under the valve cover balance hole, resulting in scratches and grooves on the valve spool surface and guide surface, as well as indentation on the sealing surface. This is a common fault that often occurs in newly operated systems and during initial operation after overhaul. In this case, it is necessary to disassemble and clean the valve, remove the debris, and grind the damaged sealing surface if necessary. At the same time, open the bottom plug to flush the debris that falls into the lower valve cover from the balance hole, and flush the pipeline. Before operation, open the manual regulating valve fully, let the medium flow for a period of time, and then put it into normal operation.
For some media that are prone to sedimentation and contain solid particles, blockage often occurs at the throttle port and guide position when using a regular valve for adjustment. In this case, external gas and steam flushing can be connected at the bottom plug of the lower valve cover. When the valve is blocked or jammed, open the external gas or steam valve to complete the flushing work without moving the regulating valve, ensuring the normal operation of the valve.
For small-caliber regulating valves, especially ultra-small flow regulating valves, the throttling clearance is extremely small, and there should be no impurities in the medium. In this case, it is best to install a filter on the pipeline in front of the valve to ensure smooth passage of the medium. For regulating valves used with positioners, the most common fault is the blockage of the air passage at the throttle port. Therefore, when using a positioner, the air source must be handled properly. Usually, an air filter pressure reducing valve is installed on the air source pipeline in front of the positioner.
If solid particles in the medium or welding slag and rust in the pipeline cause blockage or jamming at the throttle port, the valve can be changed to a throttling element with a larger throttling clearance, such as a throttling face with a window or opening, because the throttling area is concentrated instead of distributed in a circle, the fault can be easily eliminated. For single-seat or double-seat valves, the plug-type valve spool can be changed to a "V"-shaped or sleeve valve. For example, a double-seat valve in a certain chemical plant often gets stuck. After recommending the use of a sleeve valve, the problem was immediately solved.
Utilize the flushing energy of the medium itself to flush away easily sedimented and easily blocked substances, thereby improving the anti-blockage function of industrial valves. Common methods include: ① changing to closed-loop flow; ② using streamlined valve bodies; ③ placing the throttle port at the most severe flushing point. When using this method, pay attention to improving the erosion resistance of the throttling element material.