How to deal with the frequent jam or blockage of the control valve
1. Cleaning method
The welding slag, rust and slag in the pipeline cause blockage or jamming in the throttle port, guide part and balance hole of the lower valve cover, resulting in tensile and scratch on the surface of valve core and guide surface, and indentation on the sealing surface. This often occurs in the new commissioning system and in the early stage after overhaul. This is the most common fault. In this case, it is necessary to remove the slag and remove the slag. If the sealing surface is damaged, it should also 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 flushed. Before putting into operation, the control valve should be fully opened and the medium should flow for a period of time before normal operation.
2. External flushing method
When the ordinary valve is used to regulate the medium which is easy to precipitate and contains solid particles, it is often blocked at the orifice and the guide, and the flushing gas and steam can be 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 control valve, so that the valve can operate normally.
3. Installation of pipeline filter
For small diameter control valves, especially for ultra-small flow control valves, the throttling clearance is very small, and there is no slag in the medium. In case of blockage, it is better to install a filter on the pipeline in front of the valve to ensure the smooth passage of the medium. The most common fault of the control valve with positioner is that the positioner works abnormally. Therefore, when the positioner works, the air source must be handled well. The usual method is to install the air filter pressure reducing valve on the air source pipeline in front of the positioner
4. Increase throttle clearance
If the solid particles in the medium or the welding slag and rust which are washed out in the pipeline can not pass through the throttling orifice and cause blockage and jamming, the throttling parts with large throttling clearance can be used instead of the valve core and sleeve with large throttling clearance. The fault can be easily eliminated because the throttling area is concentrated rather than distributed in a circle. If it is a single seat or double seat valve, the plunger valve core can be changed into the valve core with "V" shaped port or sleeve valve. For example, a double seat valve is often stuck in a chemical plant. After the sleeve valve is recommended, the problem is solved immediately.
5. Medium erosion method
By using the scouring energy of the medium itself, it can wash and take away the things 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 changing to flow closed type; ② adopting streamline valve body; ③ placing the throttle at the place with the most severe scour; using this method, attention should be paid to improving the erosion resistance of throttle materials.
6. Change the straight through method to the angle method
The direct flow is inverted-s flow, the flow path is complex, and there are many dead zones in the upper and lower chambers, which provides a place for the precipitation of the medium. Angular connection, medium as if flowing through 90 ℃ elbow, good erosion performance, small dead zone, easy to design into flow line. Therefore, the use of straight through regulating valve can be changed into angle valve when slight blockage occurs.