Electric control valve maintenance is divided into emergency maintenance, regular maintenance and predictive maintenance. Emergency maintenance is the maintenance when the electric control valve fails and cannot meet the process operation requirements. Regular maintenance usually includes daily maintenance and maintenance that is carried out simultaneously with process shutdown overhaul. Predictive maintenance is based on the analysis results of predictive maintenance, targeted maintenance of the electric control valve components. Emergency maintenance is the maintenance after the electric control valve fails, and the regular maintenance and predictive maintenance are the maintenance before the electric control valve fails.

(1) Daily inspection and maintenance of electric control valves include the following:
1. Eliminate stress. Various stresses caused by improper installation or combination. For example, the high temperature medium generates thermal stress, and the installation is tight. Imbalance of solid force causes stress and so on. The imbalance of stress acts on the electric control valve, deforming the valve stem and guide of the electric control valve, and cannot be correctly aligned with the valve seat, causing leakage and increased deterioration. Therefore, maintenance work to eliminate stress should be carried out in daily maintenance.

2. Remove rust and dirt. Frequently check whether there is rust, welding slag, dirt, etc. in the connecting pipeline of the electric control valve, and remove it in time after discovery. Because these dirt will cause the electric control valve spool and valve seat to wear and affect the normal operation of the electric control valve. Generally, filter devices such as filters can be installed in front of the electric control valve and cleaned regularly.

3. Check the electric control valve support. The electric control valve support makes the parts of the control valve in a position that is not affected by gravity. If the support is improper, the valve stem of the electric control valve cannot be aligned with the valve seat, which increases the deterioration and reduces the sealing performance. Therefore, it should be checked whether the electric control valve support is suitable.

4. Remove the dirt that supplies energy such as air source and hydraulic oil. Air source and hydraulic source are the energy source for the operation of the electric control valve. Impurities contained in the instrument compressed air and hydraulic oil can block the orifice and pipes, causing malfunctions. Therefore, it is very important to check the air source and hydraulic oil regularly, and to drain the filter device regularly.

5. Inspection of gear transmission. The gear transmissions of the hand-wheel mechanism, electric actuator and hydraulic actuator should be checked regularly and lubricants should be added to prevent seizure. Check whether the brake and limit device are flexible and easy to use.

(2) The main contents of daily maintenance of electric control valves and accessories are as follows:
1. Replacement of diaphragm of pneumatic actuator. The diaphragm of the pneumatic film actuator is stretched during operation, so it is easy to fatigue and damage. The rubber diaphragm of the same specification should be used for replacement, and the diaphragm should be evenly stressed during tightening to prevent leakage and crushing of the diaphragm.

2. Grinding. The valve core and the valve seat cause leakage after a certain period of operation, and the internal leakage between the piston and the cylinder body of the cylinder will also cause internal leakage. At this time, grinding should be carried out. Hand-grinding, mechanical grinding, coating treatment and inserting can be carried out. The emery grain size used for grinding should be suitable, and the grinding force should be uniform and suitable. After grinding, it should be polished to meet the required finish and precision requirements, and to meet the centering requirements of the valve core and valve seat. After the final assembly, the electric control valve should be tested for tightness.

3. Replace the stuffing box. . The stuffing box of the same type should be used when replacing the stuffing box. When replacing the stuffing box, you should carefully hook the stuffing out and remove the stuffing correctly to prevent damage to the valve stem. The installation of the new stuffing box should be in accordance with the requirements of the manual. The incision should be misplaced to prevent the thread of the valve stem from scratching the packing. The packing should be evenly pressed against stress and increase friction.

4. Replacement of transmission parts. The electric control valve and the transmission parts in the accessories can be replaced and repaired if part of them is worn out. After replacement and repair, the transmission should be flexible and the transmission gap should be as small as possible.

5. Cleaning of pneumatic amplifier. When the orifice of the pneumatic amplifier is blocked due to the dirt in the compressed air used for the instrument, the orifice should be cleaned, and the appropriate steel wire can be used for dredging and cleaning. When reinstalling, the amplifier diaphragm should be evenly stressed to prevent blockage or leakage. The gain of the amplifier can be adjusted by adjusting the pressing force of the steel ball to prevent resonance.

6. Stuffing box inspection. The wear and compression force of the packing should be checked, and the stuffing box should be replaced regularly to ensure that the packing can seal while reducing the impact of its friction. Lubricating oil should not be added to the stuffing box without oil lubrication.

7. Check for safe operation. For electric control valves and related accessories used in explosive hazardous locations, check their safe operation, such as whether the sealing cover is tightened, the operation of the safety barrier, power supply, etc., to ensure that the electric control valve and related accessories can operate safely.

8. Transport and storage. During transportation and storage, the electric control valve should be fixed with a special bracket to prevent loosening; the relevant accessories installed on the electric control valve, such as valve positioner, handwheel mechanism, etc., should be firm, and the feedback rod connected with the electric control valve should be prevented. Components are damaged by external force; each connection interface should be covered with plastic film to prevent foreign objects from intruding; the connection port of the electric control valve can be sealed with matching flanges and blind plates, or adhesive paper can be used to seal to prevent foreign objects from intruding. A firm wooden box should be installed during transportation, and the impact of harsh transportation environmental conditions such as wind, sand, rain, and dust should be taken. The environmental conditions for transportation and storage shall meet the requirements of the product specification.