Positioner is a device put into a valve to ensure that it is at correct position.An open/close operation of control valve also can be done with an I/P converter but the position of the valve can’t be confirmed. calibration of control valve positioner is crucial calibration that should be done by extreme precision . Positioner senses the valve position with with a feedback link which is its input signal .the purpose of control valve is to improve the accuracy of control valve response. Calibration of control valve positioner is what we are going to discuss.
to know more about control valve accessories check the link Control valve accessories
Equipment needed for Calibration of control valve positioner
positioner, control valve,pressure source
Calibration procedure of control valve positioner(heart type)
- Zero adjustments are done at the nozzle
- Span adjustment is done by moving flapper assembly (follower assembly) along the summing beam
- Air supply to the positioner is 20 psi.
- To calibrate move the flapper assembly to midrange of direct side or about no.6
- Increase the input signal to 3 psi
- Adjust the nozzle in or out slowly to make the output gauge output 0 psi
- Increase the input pressure to 15 psi
- If the output saturates too soon (at the output gauge) before giving 15psi move the flapper assembly to smaller number in the summing beam
- If the output saturates too late or above 15 psi move flapper assembly to larger number at the summing beam
- Every time when you move the flapper assembly reset the nozzle to zero also.