Methods for Handling Frequently Jammed or Clogged Control Valves

1. Cleaning Methodd slag, rust, and debris in the pipeline can cause blockage or jamming at throttling ports, guide parts, and balance holes in the lower valve cover. This damages the valve  surface and guide surfaces, causing scratches and indentations on the sealing surface. This often occurs in newly commissioned systems or during the initial operation after major overhauls. It is thecommon fault. In such cases, the valve must be disassembled for cleaning to remove debris. If the sealing surface is damaged, it should be lapped. At thme time, the bottom plug should be opened to flush out debris that has fallen into the lower valve cover from the balance hole, and the pipeline should be flushed. Before commissioning, the cvalve should be fully opened to allow the medium to flow for a period of time before being put into normal operation.

2. External Flushing Method

When regulating media that are prone to ppitation and contain solid particles with ordinary valves, blockage often occurs at throttling ports and guide parts. External flushing gas or steam can be connected at the bottom plug of the lowervalve cover. When the valve becomes blocked or jammed, opening the external gas or steam valve allows flushing to be performed without moving the control valve, restoring normal operation.

3. PipInstallation Method

For small-bore control valves, especially ultra-low flow control valves, the throttling gap is extremely small, and the medium must be free of any debn such cases, it is best to install a filter on the pipeline upstream of the valve to ensure the medium flows smoothly. For control valves used with positioners, abnormal operation of thositioner is most commonly caused by blockage of the air circuit throttling port. Therefore, when using a positioner, the air supply must be properly treated; the common method io install an air filter regulator on the air supply line upstream of the positioner.

4. Increasing Throttling Gap Method

If solid particles in the medium or debris (such eld slag and rust) from the pipeline cause blockage or jamming because they cannot pass through the throttling port, a throttling element with a larger throttling gap can used—such as valve cores or sleeves with window or opening-type throttling areas. Since the throttling area is concentrated rather than distributed around the circumference, faults can be easily eliminated. Forngle-seat or double-seat valves, the plunger-type valve core can be replaced with a "V"-port valve core or converted to a sleeve valve. For example, a double-st valve at a chemical plant frequently jammed; after recommending the conversion to a sleeve valve, the problem was immediately resolved.

5. Medium Flushing Method

Utilize the medium's own flung energy to flush away and carry off substances prone to precipitation and blockage, thereby improving the valve's anti-clogging function. Common methods include: ① Changing to a flowclosed type; ② Using a streamlined valve body; ③ Positioning the throttling port at the most severe flushing point. When using this method, attention must be paid to i the erosion resistance of the throttling element material.

6. Converting Straight-through to Angle-pattern Method

The straight-through valve has an inverted S-flow path with a complex flow channd many dead zones in the upper and lower chambers, providing places for medium precipitation. The angle-pattern connection is like a 90° elbow, offering good flushing performance, smalld zones, and is easy to design as a streamlined shape. Therefore, when a straight-through control valve experiences slight blockage, it can be converted to an angle-pa