Hi,
For a pressure control valve in the flare line, PID action is set to direct, and when the PV (pressure) is less than SP, the valve is fully closed (MV = 0). When PV (pressure) started to increase to match the SP, the PID controller demanded OUT (MV) be opened and closed.
When the PV < SP, why does the valve open and close when it has to be closed until the PV goes above SP?
Gain: 2
Reset: 150s
Rate: 0s
PID Structure: PI action on error, D action on PV.