Pneumatic control valve is one of the instruments widely used in petrochemical enterprises. It is of great significance to ensure the normal operation and safe production of the process equipment by operating accurately and normally. Therefore, it is necessary to strengthen the maintenance of pneumatic control valves.
First, the key points to check the location during maintenance
Check the inner wall of the room: In the case of high pressure difference and corrosive medium, the inner wall of the valve and the diaphragm of the diaphragm valve are often impacted and corroded by the medium, and it is necessary to check the pressure resistance and corrosion resistance;
Check the valve seat: due to the infiltration of medium during operation, the inner surface of the thread used to fix the valve seat is susceptible to corrosion and the valve seat is relaxed;
Check the spool: the spool is one of the moving parts of the control valve, the erosion of the medium is more severe, and the parts of the spool should be carefully checked whether the spool is corroded and worn during maintenance, especially under the condition of high pressure difference, the wear of the spool is more severe due to cavitation. Severely damaged spools should be replaced; Check the sealing packing: check whether the packing asbestos rope is dry, if the PTFE packing is selected, pay attention to check whether it is aging and whether its mating surface is damaged;
Check whether the rubber film in the actuator is aged and whether there is cracking.
2. Daily protection of pneumatic control valves
When the control valve is filled with graphite-asbestos, lubricating oil should be added to the packing once in about three months to ensure that the control valve is flexible and easy to use. If it is found that the pressure cap of the packing is very low, the packing should be supplemented, and if the PTFE dry packing is found to be hardened, it should be replaced in time; Attention should be paid to the operation status of the control valve during the tour inspection, and check whether the valve position indicator and the output of the regulator are consistent; For the regulating valve with a positioner, the air source should be checked frequently, and the problem should be dealt with in time; The hygiene of the control valve and the integrity of the components should be kept at all times.
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