If the control valve is without bottom cap. The actual needs to be changed.
If bottom cap is provided.
a) Disconnect the stem from the actuator stem.
b) Separate the body from the bonnet.
c) Remove the bottom cap and the plug from body.
d) Detach the plug from the stem by removing the pin.
e) Fix the stem at the other end of the plug and fix the pin back.
f) Turn the body upside down. Connect it to the bonnet after inserting the plug and stem.
g) Connect back the stem to the actuator stem.
h) Fix back the bottom cap.
i) Calibrate the valve.