How to verify the control valve passing
Valve passing can be verified by the instruments installed downstream of the valve. for eg, if gas is flowing through the pipeline a pressure gauge or pressure transmitter reading more than zero will indicate the valve is passing despite the close command given to the valve. In case of liquid flow transmitter or flow gauge can detect valve passing.
Closed full valve and down steam side open drain valve to confirm but make sure the type of fluid if there is gas so you have handled according to the procedure. Close air of cv or make zero Cv and then observe FT or PT of that loop…