Anti blocking method of control valve

Anti blocking method of control valve

Anti blocking method of control valve

1. Cleaning method

The welding slag, rust and slag in the pipeline cause blockage or jamming in the orifice, guide part and balance hole of the lower bonnet, resulting in strain and scratch on the valve core surface and guide surface, indentation on the sealing surface, etc. This often occurs in the initial stage of new operation system and operation after overhaul. This is a very common fault. In this case, it shall be disassembled for cleaning, and the slag shall be removed. If the sealing surface is damaged, it shall also be ground; At the same time, open the bottom plug to flush the slag falling into the lower valve cover from the balance hole and flush the pipeline. Before putting into operation, fully open the regulating valve and bring the medium into normal operation after flowing for a period of time.

2. External scouring method

When ordinary valves are used to regulate some media that are easy to precipitate and contain solid particles, they are often blocked at the throttle and guide, and scouring gas and steam can be connected outside 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 and make the valve operate normally.

3. Installation of pipeline filter

For small-diameter control valves, especially ultra-small flow regulating valves, the throttling clearance is very small, and there can be no little slag in the medium. In case of blockage, try to install a filter on the pipeline in front of the valve to ensure the smooth passage of the medium. For the regulating valve with positioner, the positioner does not work normally, and the blockage of its gas path throttle is a very common fault. Therefore, when working with the positioner, the air source should be handled properly. The usual method is to install an air filtration pressure reducing valve on the air source pipeline in front of the positioner.

4. Increase throttle clearance method

For example, the solid particles in the medium or the washed out welding slag and rust in the pipeline can not pass through the orifice, resulting in blockage, jamming and other faults. The throttling parts with large throttling clearance can be used - valve cores and sleeves with window and opening throttling area. Because the throttling area is concentrated rather than circular distribution, the fault can be easily eliminated. If it is a single or double seat valve, the plunger valve core can be changed into a valve core with "V" port, or into a sleeve valve, etc. For example, a two seat valve in a chemical plant is often stuck. It is recommended to use sleeve valve, and the problem will be solved immediately.

5. Medium scouring method

Use the scouring energy of the medium itself to scour and take away things that are easy to precipitate and block, so as to improve the anti blocking function of the valve. Common methods are:

① Change to flow closed type;

② Adopt streamlined valve body;

③ Place the orifice at the place where the erosion is severe. When using this method, pay attention to improving the erosion resistance of the throttle material.

6. Straight through method is changed to angular method

The direct flow is inverted s flow, the flow path is complex, and there are many dead zones in the upper and lower cavities, which provides a place for medium precipitation. Angular connection, the medium is like flowing through a 90 ℃ elbow, with good scouring performance and small dead zone, which is easy to be designed into a flow line. Therefore, the use of straight through regulating valve can be changed into angle valve when it is slightly blocked.