Pressure Transmitter Re-Range Questions

If a smart (digital) pressure transmitter configured with re-range then does it need to be re-trimmed as well?

The pressure transmitter PT-89 on this natural gas separator vessel presently has a calibrated range of 0 to 400 PSIG.

Contents

Operations personnel would like you to re-range this transmitter for 300 to 375 PSIG instead:

Pressure Transmitter Re-Range

Answer the following questions about the task of re-ranging, explaining each of your answers:

1. Does the new, requested range constitute a zero shift, a span shift, or both?

2. If this is a “smart” (digital) transmitter, does it need to be re-trimmed as well as re-ranged?

3. Will the control room indicator PIR-89 need to be re-calibrated, re-ranged, or both?

4. Will the local pressure gauge PG-131 need to be re-calibrated as well?

5. Will the pressure safety valves PSV-11, PSV-12, and/or PSV-13 need to be set for lower “lift” pressures?

6. If the maximum (factory) range of this pressure transmitter is 0 to 750 PSI and the maximum turndown ratio for the required accuracy is 20:1, will it be able to meet the new range? If not, what might you have to do in order to fulﬁll the operations’ request?

7. Why do you suppose operations would like you to re-range this transmitter? In other words, what operational advantage(s) might be gained from doing so? Are there any potential disadvantages of having the new range versus the old?

Share your answers with us through the below comments section.