Givens Control Engineering Inc. provides control engineering services to the pulp & paper industry. Our specialties are MD and CD paper machine controls, dryer, headbox and all stock preparation controls. We have also done pulp mill controls.
Our control engineering services consist of:
Control design is usually done at a level of detail that an instrument technician could follow and could even create (with our assistance). For example, it is not sufficient to simply specify that one variable is ratioed to another (this is usually done by a process engineer or equipment manufacturer); the correct mathematics of implementing the ratio with due consideration for noise must be specified.
Control tuning of PID loops is done using the Lambda tuning method which emphasizes control stability through varying process conditions, grade changes, speed changes, flow rate changes, etc.. We normally use our own data acquisition equipment Data Logger CVF2 to take measurements and Analyse-Plus to plot and analyse the data.
We also provide tuning of high level controls (non-PID) such as Smith Predictor, Model Reference, Dahlin, and CD controls on platforms where we know the control algorithm or where sufficient system documentation is available.
We also have our own Modified Smith Predictor controller that can be installed in many DCS or PC-based systems. It has been running for 5 years on many of the most critical controls on 2 paper machines (MD Weight, Moisture, Headbox pH, etc.). It is very well proven with many special features to enhance stability even if the model is imperfect (normal case).
Control & variability audits are done mainly in paper machine and stock preparation areas to determine which controls exhibit high variability and what are the causes. Often a solution can be suggested and implemented at the same time. Again, we normally use our own data acquisition hardware & software to take measurements and analyse them.
Our Lambda tuning training of instrument technicians or engineers emphasizes practical tuning rather than theory. It's done in a mixed class-room / hands-on setting. The hands-on setting means that the tuning methods taught in the class-room are used on a running process (eg. the stock preparation area). Typically, one loop of each type (usually a total of 3 loops) is selected for the entire group to perform bump tests and tune together. Typically, 50 % of the time is spent teaching the methods and 50 % is spent tuning loops and reviewing the results. At the end of the course, the students do not need to "re-learn" the course before applying the methods since they will have already applied them (providing they apply them reasonably soon after attending the course). People learn best by doing.
This training method works well in many mills. But in some mills, instrument technicians work primarily on shifts answering emergency calls and do not tune often enough to retain the tuning technique. In those cases, it is often better to select a few technicians who work on days and whose primary function is control tuning and improvement.
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