Answer / jigaranadkat

There can be may issues :

1) Very first indication is that your plug and seat are having some foreign particles or uneven surface which is restricting the valve for initial opening.
2) Check the springs of the actuator for any crack as when pressure is increased it lifts the valve.
3) Check for positioner relay.

Answer / smith

which type of positioner you are using?. it depends on the positioner. try to tune it correct manner you will get the output.

Answer / praveen kumar

first decoupled the actuator then ensure and mark on the stem of full opening and closing, then couple the actuator stem and plug on fully 100 % open of marking position. finally to ensure zero passing test.just close the control valve and fil the water on bonnet inlet.same passing tht u feel means place the nut or iron piece something inb/w the coupling.then ensure again on zero passing test.if again feel the passing means pls to do lapping on seating...then take an trail.

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