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Jun
17

Top Ten Limitations – Missing Measurements

The greatest limitation I experienced as a user for process control improvement (PCI) was unmeasured process variables. If we had a high degree of instrumentation, so that only a configuration change was needed we could let our creativity roam free and quickly implement various improvements including new loops and feedforward control. Also, from trend charts of the measurements, we could track down and fix problems, such as valves running out of pressure drop and sticking. We called these PCI opportunities quick hits. Inevitably, most of the 4% savings in “Cost of Goods” (COGs) from PCI came from quick hits. A lot of improvements that required the installation of measurements typically stayed as neat ideas on a list. To buy the measurement with the right range and to install the conduit and cable, get it on the wiring drawings, and keep the measurement in calibration was too big of a hurdle more from a lack of time and resources than money.

With smart wireless instrumentation we have a different scenario. Today’s smart transmitters can have their ranges changed by just a configuration change, have greater turndown, and an installed accuracy that is a factor of ten better than a 1970s benchmark. Drift is now extraordinarily small. Transmitters can go five years without a calibration. If the process connection and Gateway exists, wireless transmitters stocked as generic spares can be installed within hours. The measurements can be moved as knowledge is gained on the application and best location.

I recommend adding process connections during project design to enable the future installation of an annubar, pressure transmitter, thermowell, and electrode (for pH applications). We did this in the 1970s so we could move around spare wide range pressure and temperature gauges. Unfortunately, reading resolution was poor and the only historization was handwritten notes by field operators. Now we can have the same portability with wireless but with an incredible accuracy and visibility.

Try out the flexible measurement concept on an important unit operation. See what smart feedforwards, inferential measurements, online diagnostics, multivariate analysis, models, and metrics you can develop. Be sure to use the measurements to document the process performance before any improvements are made. A major detriment to the recognition of our profession is our lack of showcasing benefits. “Before” and “After” documentation can pave the way to a whole lot of other opportunities and a bright personal future. This leads us to next week’s Top Ten Limitation – Value Analysis.

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