What symptom indicates that the check valve on a flow control valve (FCV) is stuck open?

A check valve on a flow control valve (FCV) is designed to allow fluid to flow in only one direction, preventing backflow. When the check valve is stuck open, it no longer serves this purpose effectively. This malfunction leads to an unrestricted flow of fluid in both directions. As a consequence, the actuator connected to the FCV experiences rapid movement since it can receive fluid without the resistance that would typically be present if the valve were functioning correctly.

Fast actuator speed in both directions signifies that fluid is freely flowing through the actuator, which aligns with the symptom of a check valve stuck in the open position. Understanding this symptom is crucial for diagnosing issues within pneumatic systems, as it directly affects the performance and control of the actuators involved.

In contrast, other symptoms such as slow actuator speed, loss of pressure, and unstable flow rate indicate different problems, possibly related to flow restriction, leaks, or fluctuating system pressure rather than an open check valve.