1. If it is a pressure regulating valve, the feedback signal is the outlet pressure of the valve, which is introduced into the actuator through the signal tube.

2. If it is a flow regulating valve, there is an orifice plate (or other resistance device) at the outlet of the valve to take out the differential pressure signal from both ends of the orifice plate and introduce it into the actuator.

3. If the pneumatic control valve is a temperature control valve, there is a temperature sensor (or temperature bulb) at the outlet of the valve to drive the actuator through the thermal expansion and contraction of the medium in the temperature sensor.

Various stresses are caused by improper installation or combination, for example, high-temperature medium generates thermal stress, installation is tight. Imbalance of solid force causes stress, etc. The imbalance of stress acts on the self-operated control valve, making the valve stem of the self-operated control valve, The guide parts of the electric control valve are deformed 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.

Remove rust and dirt, and check the connecting pipes of the self-operated control valve frequently for rust, welding slag, dirt, etc., and remove them in time after discovery, because these dirt will cause wear of the self-operated control valve core and seat. The self-operated control valve that affects the normal operation of the self-operated control valve, usually, a filter screen and other filtering devices can be installed in front of the self-operated control valve and cleaned regularly.

The support of the self-operated control valve keeps the components of the self-operated control valve in a position that is not affected by gravity, etc. Improper support will cause the valve stem of the self-operated control valve to be unable to align with the valve seat, which will increase the deterioration and reduce the sealing performance. Therefore, it is necessary to check whether the self-operated control valve is properly supported.