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Nov
18

Deminar Demos – Process Control Lab Website

The process control lab website is finally ready for public use. An ad hoc extracurricular effort by Emerson, Experitec, Monsanto, and Mynah created a fast, free, and easy interface to the process control labs used in the Deminar demos. I personally want to thank Charlie Schliesser (Experitec) and Jack Ahlers (Monsanto) who found a negligible cost solution to make virtual plants available without IT security issues. Previous attempts to use Remote Desktop were blocked by most corporate firewalls and the response was slow at times. TeamViewer provided a simple internet connection but files were difficult to protect and the license was expensive for multiple users. The LogMeIn license fee of $300 is incredibly low and the view is simply operator displays and historian trends. The remaining screen size and resolution limitations imposed by DeltaV Operate will go away with the next version of DeltaV.

The website glamour is rather minimal but will be enhanced as time permits. The essentials in terms of instructions, an overview, and links to the Deminars are in place.

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The intention of the site is provide a method for exploration of process control improvement without having to work in a configuration environment. Jack Ahlers donated his time to create DeltaV Operate Graphic and Detail displays to provide a control room view for a broader audience that would include operations, process design, process technology, maintenance technicians, and students. The following details show the opportunity to change a wide variety of PID options, PID parameters, process dynamics, measurement dynamics, and valve dynamics.

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The control loop labs offer an incredible spectrum of scenarios. The PID options include a smart bang-bang for the fastest possible setpoint response, dynamic reset limit for slow secondary loops and valves, PIDPlus for suppression of oscillations from analyzers, backlash, stick-slip, split range points, and wireless. The PID deadtime entry provides deadtime compensation. An auto tuner and adaptive controller is available via the DeltaV Insight icon on the faceplate. The standard PID faceplate detail provides access to tuning settings, PV filter, integral deadband, and setpoint velocity limits. Signal characterization tables create an extremely flexible method of entering local nonlinearities for the process gain, process deadtime, and valve gain. Second order plus deadtime plus The refresh and sensitivity measurement settings correspond to the default update rate and trigger level, respectively for wireless. The control valve has a velocity limited second order plus deadtime response with backlash (deadband) and 2 methods of setting stick-slip (sensitivity and resolution). A valve signal lead-lag option can be useful to kick through valve deadband, sensitivity, and resolution limits, especially for compressor and turbine control. Load, setpoint, and valve response metrics are tallied for the control loop labs and process metrics are provided for the temperature and pH labs.

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The temperature lab uses a model of a University of Texas unit operations lab reactor. The pH lab uses a model of the Monsanto neutralizer for demineralizer unit regeneration waste water. These models use material, energy, and charge balances to provide a full high fidelity process model, which brings me to a concluding thought. When a person says a model uses first principles, it may simply have a steady state solution for the process gain with a delay block and filter block added to provide dynamics. The temperature and pH models on the process control lab website use ordinary differential equations to provide a full unsteady state first principle model that can show the effect of startups-shutdowns, nonlinearities, and interactions not seen in steady state models.

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The temperature lab is featured on the cover of my latest book, which is the source of the Temperature Insight of the Day on this website.

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