Case Study - Control System on Boiler Air Feed


A valued customer recently approached us to help solve an issue with their boiler constantly tripping on air intake.

We discovered the linkage feeding back to the positioner and switchbox were badly worn causing deadband and Hysteresis. The linkage system was quite complex, converting a linear motion to rotary for the positioner, and then coming from that to the switchbox. The switching needed to be very accurate asking the switch to close at 2% of travel. The current system was unable to give that level of accuracy.


We recommended a change to Fisher Fieldvue DVC6200 double acting positioner eliminating the need for complex linkages.

The Fisher fieldvue DVC6200 used a magnet array to feed back stem position to the positioner. No friction, no deadband, no Hysteresis. Used in conjunction with a Fisher 377 trip valve to lock the a actuator in position on air failure.

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