Emerson Exchange 365

I wanted to pass along this blog post by process control hall of fame member Greg McMillan, Checklist for Best Pressure Measurement Performance over on his ControlGlobal.com Control Talk blog.

In the post, he refers the reader to his book, Essentials of Modern Measurements and Final Elements in the Process Industry for greater detail.

He highlights 22 items in his checklist:

1. Is the transmitter fast enough for application (e.g. damping < 0.2 sec for compressor control)?
2. For gas, is transmitter mounted above process connection to prevent accumulation of liquids?
3. For liquid, is the transmitter below process connection to prevent trapping gases?
4. Do impulse lines have a continuous slope with no bends or smooth long radius bends?
5. Do impulse lines have vent and drain valves?
6. Does a DP have an equalization valve?
7. Does process pressure connection design prevent appreciable velocity head?
8. Do transmitter and impulse lines need freeze protection?
9. If heat tracing is used, are high temperatures prevented that could alter fluid composition in impulse lines or transmitter (e.g. vaporization, reactions, or formation of tars and polymers)?
10. For plugging services, can impulse lines be purged or eliminated?
11. For purged impulse lines is purge flow and purge pressure high enough?
12. For purged impulse lines is purge flow and purge pressure adjustable and indicated?
13. For purged impulse lines is liquid purge needed to eliminate transients from compressibility of gas purge during fast static pressure disturbances and to prevent solids build-up from drying at bubbler tip?
14. Can impulse lines be eliminated by direct mount of transmitter or use of capillary system?
15. Should an extended diaphragm be used to minimize fouling of a direct mounted level DP?
16. Does diaphragm area need to be increased to improve threshold sensitivity?
17. Does diaphragm area need to be decreased to increase speed of response?
18. Is capillary length minimized to increase speed of response?
19. Are the capillary systems at the same temperature (e.g. sun versus shade)?
20. For DP measurement with low static pressure, can DP be computed from dual direct mounted transmitters to eliminate the need for impulse lines?
21. Can a smart transmitter be used to detect plugged impulse lines?
22. Can wireless transmitters be used to provide portability for process troubleshooting?

Are their other points to consider for better performance or any alternative thoughts to Greg's checklist?