Answer Posted / goutam chatterjee

first of all we cant say any valve as a control valve with
out positioner... because we know that control valve is a
final control element.. we only say any valve as a control
valve when its acted as percentage operation as per process
requirement. with out positioner this is acted as a simple
on off valve... because percentage opening not possible with
out positioner... & we need to calibration the positioner
because cv alwys maintain the process in aspect of its final
contron ability.... i.e if process need to open the cv 25%
if the positioner not calibrated then it may be open 30 or
10 % for example... thats why we need to calibrate the
positioner.....

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