Control Talk Blog

Future PV Values are the Future

Control loops have to deal with disturbances and setpoint changes, yet operator displays give a static picture. The simple identification of the loop deadtime and calculation of the process variable (PV) rate of change can be used to provide intelligent trends and future trajectories that not only help the operator...

Checklist for Best PID Performance

There is an incredible offering of PID features and options enabling maximum disturbance rejection and setpoint response but also the coordination of loops and unit operation optimization. While the full aspects of the PID capability are book worthy, this checklist and an excerpt from an ISA Automation Week 2012 paper...

Checklist for Best pH Measurement Performance

The composition measurement with by far the greatest sensitivity and rangeability is pH.  Consider that pH routinely detects changes at 7 pH to the 9th decimal place and for a 0-14 pH scale covers 14 orders of magnitude of hydrogen ion concentration.  New glass and reference designs have dramatically reduced...

Checklist for Best Inline Flowmeter Performance

Nearly all process inputs are flows. The measurement of flow is important for process analysis, metrics, and modeling, reducing variability of process inputs, enabling feedforward and ratio control, and isolating valve nonlinearities by secondary flow loops. Inline flow meters offer the best accuracy and rangeability.

Checklist for Best Temperature Measurement Performance

Temperature is the most important common measurement. Temperature determines product formation rate and yield in reaction and crystallization processes and product composition in separation processes. Temperature is also important for monitoring energy balances and heat transfer coefficients.  The principal considerations are the selection of a TC or RTD and the...

Checklist for Best Pressure Measurement Performance

Pressure and differential pressure (DP) measurements are important for regulating inventory, flow, and product quality and are critical for ensuring safe operation.  Installation errors and the drift of today’s smart pressure and DP transmitters have decreased by an order of magnitude by compensation of temperature, static pressure, and non-ideal sensor effects.

Checklist for Best Radar Level Measurement Performance

Radar offers an incredibly sensitive measurement of surface level that can be nearly maintenance free. The potential for an accurate inventory measurement is dramatic but with this extreme capability comes some extraordinary application considerations. A checklist is offered of implementation details to help achieve the full capability of this measurement.

Checklist for Best Variable Speed Pump Performance

Variable speed pumps can save energy when the flow is reduced. However, the turndown of the pump speed may not achievable if there is overheating at low flows, excessive sensitivity at low rpm, and cycling at high destination pressures.

Checklist for Best Control Valve Performance

The threshold sensitivity and resolution of measurements (smallest incremental change) has improved dramatically to better than 0.05% with new sensor technology and smart compensation of extraneous effects of operating conditions. The response of the air-actuated control valve has improved, but the smallest incremental change in position varies widely depending upon...

What is the key PID feature for Basic and Advanced Control?

The value of a key PID feature is increasingly becoming apparent. I got a preview of the importance when I found the 1980s vintage DCS required a fix for override control that was inherently addressed in the next generation of DCS by this feature.