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Automatic control valves are important actuating elements in industrial automation process control. By moving the valve stem within the valve body, these valves change the flow area between the valve stem and the valve seat, thereby regulating parameters such as the pressure, flow rate, and temperature of the medium. Classification of control valves: 1. By structure: cage valve, single-seat valve, double-seat valve, ball valve, butterfly valve. 2. By control method: electric control valve, pneumatic control valve, hydraulic control valve. 3. By operating mode: straight-stroke type, angle-stroke type (rotary valve). 4. By valve body shape: straight-through valve, angle valve. The tasks involved in the daily maintenance of control valves are divided into routine inspections and periodic maintenance. The tasks related to routine inspections are as follows. 1. Consult the on-duty process operator about the operating condition of the control valve. 2. Check the power source for the control valve and related accessories (air supply, hydraulic oil, or electrical power). 3. Inspect all static and dynamic sealing points of the control valve for any leaks. 4. Check the connection pipelines and fittings of the control valve for any looseness or corrosion. 5. Check the control valve for any abnormal noises or excessive vibration, and inspect the supply condition. 6. Check whether the actuator of the control valve operates smoothly and whether it responds promptly to changes in the control signal. 7. Listen for any abnormal vibrations or noises from the valve core and valve seat. The contents of regular maintenance are as follows: 1. Regularly clean the exterior of the control valve. 2. Regularly adjust the packing glands and other sealing components of the control valves; replace the sealing components when necessary to maintain the sealing integrity of the static and dynamic sealing points. 3. Regularly apply lubricant to the components that require it. 4. Regularly drain and clean the air source or hydraulic filtration system. 5. Regularly check the condition of the connections at various points as well as any signs of corrosion; replace the connectors when necessary. Regular calibration of control valves: Organizations that have not yet carried out predictive maintenance on their control valves should conduct regular calibration of these valves. Regular calibration is a form of preventive maintenance. Depending on the different production processes, the regular calibration of control valves should have varying calibration intervals. The periodic calibration schedule for each control valve can be determined based on the information provided by the manufacturer. It can usually be carried out simultaneously with major overhauls during the production process. For some control valves used in high-pressure, high-pressure-drop, or highly corrosive environments, the inspection interval should be shortened. The main aspects of the inspection involve testing the static performance of the control valve; if necessary, additional tests can be carried out, such as testing the flow characteristics of the control valve. Regular calibration requires relevant testing equipment and instruments, as well as replacement parts; therefore, it is usually entrusted to the manufacturer to carry out.