Seeking help with problems regarding self-acting control valves

The pressure behind the valve is unstable and changes along with the pressure in front of the valve； Reason for occurrence ； 1. The valve core is stuck by foreign objects ； 2 ； The valve stem and push rod are stuck ； 3 ； Clogged inlet pipe – troubleshooting methods ； 1 ； Disassemble and reassemble to remove foreign objects; 2. Adjust again ； 3. The pressure drop behind the valve does not decrease; it remains above the required value ； Reason for occurrence ； 1 ； 1. The spring stiffness is set too high. 2. The valve diameter is too large. 3. The pressure before the valve is too high, resulting in an excessive pressure reduction ratio. Solutions: 1. Replace the spring. 2. Use a valve with a smaller diameter. 3. If the pressure before the valve to the pressure after the valve is greater than 10:1, two stages of pressure reduction should be applied. If the pressure after the valve does not increase and remains below the desired value, ； Reason for occurrence ； 1 ； 1. The spring stiffness is set too low. 2. The valve diameter is too small. 3. The pressure reduction ratio is too low. Solutions: 1. Replace the spring. 2. Use a valve with a larger diameter. 3. If the pressure before the valve is lower than 1.25 times the pressure after the valve, increase the pressure before the valve. If the pressure before the valve cannot be increased and remains below the required value, the valve will not function properly ； Reason for occurrence ； 1 ； The spring stiffness is set too low. 2. The valve core is stuck by foreign objects ； 3 ； The valve stem and push rod are stuck ； 4 ； The valve core and seat are damaged, resulting in excessive leakage. 5. The valve diameter is too large. Solutions ； 1 ； Replace spring 2, disassemble and reassemble again, readjust, re-grind or replace it, or use a valve with a smaller diameter. The pressure drop before the valve does not decrease; it remains above the desired value. Causes ； 1. The spring stiffness is set too high. 2. The valve diameter is too small. 3. The valve core, valve stem, push rod, etc. are stuck. Solutions: 1. Replace the spring. 2. Use a valve with a larger diameter. 3. Eliminate the cause of sticking and readjust accordingly. Excessive fluctuations in pressure behind or in front of the valve. Causes: 1. The valve diameter is too large. 2. The volume of the actuator’s chamber is too small. Solutions: 1. Choose an appropriate valve diameter. 2. Install a damper in the liquid inlet pipeline