Control Valve Not Moving but Signal Looks Fine
We have a flow control valve that is causing some trouble. The DCS output is steady at around 55%, and when we checked in the field, the I/P converter is receiving the correct 4–20 mA signal. Instrument air pressure is also healthy. However, the valve hardly moves and the process flow is not responding. There are no active alarms, and the valve was working perfectly during the previous shift. Before we start replacing components, what would be your troubleshooting approach? Could this be an actuator issue, positioner problem, or something else?