Notable contributor to Control magazine and process control specialist, John Rezabek presented on 7 ways the Foundation fieldbus technology improves operator confidence and performance. His abstract:
Using the abundant insights available from digitally integrated field devices, deterministic control-in-the-field, advanced diagnostics, and DeltaV graphics capabilities, operators can quickly assess abnormal situations and take actions that prevent process upsets and shutdowns. With increased confidence in the health of instrumentation and validity of measurements, operators are confident to push constraints and keep the process optimized.
John opened asking if fieldbus is useful to operators and would they even notice if it was taken away. The mission of production is to produce safely, reliability, surpassing quality requirements, with low environmental impact, efficiently, and without unplanned downtime.
Operators want a smooth day without drama and difficult situations. John thought operators would miss 7 things. The first is robustness–not brittle. Does the operator feel comfortable running closer to constraints. Fieldbus devices are supplied with robust power, digital communications means its working or its not, signal status is updated every macrocycle, signal status propagates through loop and mode sheds to manual and holds last value.
John noted that devices and systems report issues in real time, valve position feedback to provide where the valve going and if it is stuck. Also at the physical layer – the wires themselves – can be fitted to detect and report issues in real time.
Stable, optimized tuning from PID loop tuning and running control within the device means the loop operate in a robust manner giving operators confidence. John showed an example using statistical process monitoring in a pressure transmitter to detect when an abnormal condition such as a purge valve not in the right position.
Giving the operators confidence in the robustness of their loops allows them to operate closer to constraints for higher efficiencies.
Operators can review simple diagnostics to gain insights. This helps solve issues process anomalies, such as plugged impulse lines.
Simplified path to extend automation is where the requests an operator makes can be easily accomodated, such as changing a manual valve over to automatc.
John summed up what this confidence operators have in the robustness of their process. Operations has exceptional trust in the “truth” of what their measurement & control system is telling them. While not always happy about pushing constraints, reliable measurement and tight control facilitate their efforts. And, crews have great autonomy and need less support and oversight