My organization is discussing how to identify transmitters that are used as Control Variables in the field. The issue we have had is a technician will calibrate a transmitter and upset the process. We will have several transmitters that are only for indication mounted next to transmitters that are for control. We have discussed painting the transmitter red and including a stamped tag to identify what the Final Element is in the control loop.

What have you seen that works well as a solution for this problem?

Any ideas are welcome.

Respectfully,

Aaron

 

If your controls are that vulnerable, you need a detailed safety review the entire system. A review that includes maintenance, operation, and misoperation.

 

The pharmaceuticals I dealt with had very stringent calibration schedules The calibration schedules were worked out in production/calibration joint meetings. The technician was issued work orders specifying which devices to calibrate on which date. The dates had to be adhered to because the equipment was scheduled to be out-of-service during calibration. The instrumentation was all tagged and was identified by tag on the work order and subsequent calibration reports.

If the instrumentation isn't tagged, then consider tags that identify the unit as an indicator or not.

For instance, if the process variable were "Level" using the letter L, then I've seen
- LIT used for a Level Indicating Transmitter for a transmitter with local indicator/display, the one used for the PV control variable
- LT used for Level Transmitter, for a transmitter with no local indicator/display, the one used for the PV control variable.
- LI used for a Level transmitter with a local indicator/display, but used only for indication purposes, not control.

And if you need to paint them to get the point across, so be it.