In the field of industrial automation process control, the conditioning valve, also known as the control valve, is the final control element that changes the process parameters such as medium flow, pressure, temperature, and wave level by means of dynamic operation by bearing the control signal output by the conditioning control unit. It is generally composed of a drive actuator and a valve. According to the characteristics of the stroke, the conditioning valve can be divided into linear stroke and angular stroke, according to the power used by the actuator, it can be divided into pneumatic conditioning valve, electric conditioning valve, hydraulic conditioning valve three kinds, according to its function and characteristics can be divided into linear characteristics, equal percentage characteristics and parabolic characteristics. The conditioning valve is suitable for air, water, steam, various corrosive media, mud, oil and other media.
1. Cleaning method
The welding slag, rust, slag, etc. in the pipeline are blocked or stuck in the saving port, guide part, and balance hole of the lower valve cover, causing strains and scratches on the valve curved surface and guide surface, and indentation occurs on the sealing surface. This often happens in the early stages of new systems and after major repairs. This is the most common, in this situation, it must be unloaded for cleaning, remove the slag, if the sealing surface is damaged, it should also be ground, and the bottom plug should be turned over together to flush out the slag that fell into the lower valve cover from the balance hole, and the pipeline is flushed, before operation, let the conditioning valve be fully opened, and the medium will be active for a period of time and then return to normal operation.
2. External scouring method
When the valve is used for some media that are easy to be deposited and contain solid particles, it is often blocked at the saving port and guide, and the gas and steam can be flushed at the bottom plug of the lower valve cover. When the valve is blocked or stuck, open the external gas or vapor valve, and the flushing operation can be completed under the condition of the conditioning valve not moving, so that the valve can operate normally
3. Install the pipe strainer method
For small-caliber conditioning valves, especially ultra-small flow conditioning valves, the saving void is very small, there can be no little slag in the medium, blocking in this situation, it is best to install a filter on the pipeline in front of the valve to ensure the smooth passage of the medium, the conditioning valve with the use of the positioner, the positioner operation is not normal, and the blockage of the gas path saving port is the most common problem, therefore, when operating with the positioner, the air source must be dealt with, and the method usually selected is to install the air filter pressure reducing valve on the air source pipeline in front of the positioner
4. Increase the void saving method
For example, the solid particles in the medium or the welding slag and rust that are washed away in the pipeline are blocked and stuck due to the failure to pass the saving port, and the saving parts with large voids can be used instead. If it is a single or double seat valve, the plunger-shaped spool can be changed to a "V" shaped spool, or changed to a sleeve valve. For example, a chemical plant had a double-seat valve that often jammed, and the problem was immediately solved after the introduction to the sleeve valve.
5. Media scouring method
Use the scouring energy of the medium itself to wash and take away things that are easy to deposit and block, and then improve the anti-blocking function of the valve. Common methods are: Changed to a closed type of operation, @选用流线型阀体; @将节省口置于冲刷最厉害处, the selection of this method should pay attention to the erosion resistance of the material to be saved.
6. Straight-through is changed to angular method
The straight through is inverted S activity, the flow path is messy, and there are many dead zones in the upper and lower cavities, which provides a place for the deposition of the medium. Angular connection, the medium is like flowing through 90 elbows, good erosion, small dead zone, easy to plan into a streamlined shape. Therefore, when a straight-through conditioning valve is slightly blocked, it can be changed to an angle valve.
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