Cleaning method, welding slag, rust, slag, etc. in the pipeline cause blockage or jam in the orifice, guide part, balance hole of the lower bonnet, so that the valve core is curved, the guide surface is strained and scratched, and the sealing surface Indentation, etc., which often occur in the new commissioning system and the early stage of commissioning after overhaul, this is the most common failure. In this case, it must be unloaded for cleaning to remove slag, such as damage to the sealing regulating valve surface. It should be ground, and the bottom plug should be opened at the same time to flush out the slag falling into the lower valve cover from the balance hole, and flush the pipeline. Before putting it into operation, let the regulating valve fully open, and the medium will flow for a period of time before bringing it into normal run.
External flushing method, when using ordinary valves to adjust some media that are easy to precipitate and contain solid particles, they are often blocked at the throttle or guide. The pneumatic control valve can be externally flushed with gas and steam at the bottom plug of the lower valve cover. When the valve is blocked Or when it is stuck, open the external gas or steam valve to complete the flushing work without moving the regulating valve and make the valve operate normally.
For small-diameter control valves, especially ultra-small flow control valves, the throttle gap is extremely small, and there should be no slag in the medium. In this case, it is best to install a filter on the pipeline before the valve to ensure The medium passes smoothly, the regulating electric regulating valve used with the positioner, the positioner is not working properly, and the air passage orifice is blocked is the most common fault. Therefore, when working with the positioner, the air source must be handled properly, usually The method is to install an air filter pressure reducing valve on the air supply line before the positioner.
After the control valve is installed, the linkage test must be carried out before the device starts. The linkage test should focus on the following points:.
(1) Before the control valve linkage test, the process pipeline must be purged strictly by the self-operated control valve and qualified. The pipeline that has not been purged is strictly prohibited to install the control valve, because the residue in the pipeline such as welding slag, dust and other hard debris It will damage the valve core and valve seat sealing surface.
(2) Before linkage of the butterfly valve, check that both ends of the valve should not be equipped with pressure test or plugging blind plates.
(3) For regulating valves with handwheel mechanisms, the handwheel mechanism should be in the “release” position, and check whether the air supply pressure of the pressure reducing valve meets the air supply requirements of each regulating valve.