Aracruz Uses a Dynamic Simulator for Control System ... - Andritz

More documents

Recommendations

Info

In general, because loop testing did not involve the EPCs, but was essentially a check of the configuration coder’s implementation of the EPC’s control philosophy; the issues were identified only, and listed on the punch lists. They were usually held for the next step of the process, the Joint-FAT. As the work progressed towards a fully functioning Simulator, the Aracruz operators (later our Trainers) began to have an opportunity to take a more detailed look at the control philosophy, interlock strategies and the patterns of implementation, or slight variations in standards or norms adopted by each EPC supplier and his contractors. Joint Factory Acceptance Test In this last step of staging, it was again necessary to have the support of the model developer, the DCS technicians, the Aracruz operators, the DCS coder and, most importantly, the EPC supplier’s start-up engineer and ideally his lead area control specialist. In the Joint-FAT the majority of modeling problems were identified and corrected. In addition, we could address also the “held” questions on our punch lists; items concerning the EPCs control philosophy. In this activity, the EPC supplier was primarily responsible for verifying the faithful execution of the start-up, shutdown and other important emergency procedures. In most cases, we also were able to obtain detailed input from the EPC’s people about the control philosophy employed, process details and validation of the Simulator as ready for training in the EPCs area. Simulator Performance Issues - What do the Punch Lists Tell Us? The punch lists were generated at two steps in staging; after initial system checkout (mostly loop testing) and after the Joint-FAT. They identified mistakes in DCS configuration coding; modeling errors or suggested changes; control strategy errors or suggested changes in philosophy; and miss-specified or poorly communicated items. The lists are the essence of what was accomplished with the Simulator during DCS staging. Figure 7, next column, summarizes overall data for Simulator/DCS staging. The data shown are weighted according to the approximate level of effort that would be required to either correct or address the item. Note that the owner of each item determined the weighting for his items. Before we discuss the data, a brief explanation of what a punch list item actually means is in order. For the DCS coder, errors could be as simple as wrong addresses and screen errors to more serious disconnects, say the logic in group starts. For the model developer, errors would usually be divided into two categories; process conceptual errors (such as an incorrect reaction equation or wrong pump data) and logic errors (a wrong address). EPC items were 90 to 95% operator suggestions for control strategy improvement and 5 to 10% errors in the control strategy. The later might be as simple as the wrong action on a valve to something much more complex. Aracruz items could be such things as DCS or control standards not correctly defined, or missing. As shown in Figure 7, the dominant items relate to control configuration coding, about 70% of all weighted errors. At least 50 to 60% of these errors were caught during loop testing, and most of the remainder surfaced in the Joint – FAT. www.andritz.com 10 of 16
Simulation Company 18% Figure 7 Overall Punch List Data What is the value of catching these errors? Some of the errors are trivial, but others might delay the start-up of the plant or the continuance of operations until they are corrected. Still other errors might not stop the plant, but could lead to a drop in operating efficiency. Both of the last two categories might result in a loss of product quality. On the modeling side, most of the significant issues surfaced during the Joint – FAT. They were primarily issues that deal with the fidelity or truth of the model response. Modeling errors are usually not trapped during loop testing because the focus is on configuration coding. Fidelity issues are also likely to surface later as well, during training, when the focus of the team is even more on process response. A DCS configuration which could start the “virtual mill” was considered highly likely to be a configuration which would start the real mill. The virtual mill (in essence a dynamic process model, an area DCS control configuration and an array of supporting hardware and software) was at this point ready to be applied to operator training. General Statistics of Configuration Check Out Phase EPC Supplier 14% Customer 1% DCS Company 67% www.andritz.com 11 of 16
Page 1 and 2: Aracruz Uses a Dynamic Simulator fo
Page 3 and 4: A simplified view of the overall ar
Page 5 and 6: Worksheet Building - Featuring a Mo
Page 7 and 8: Washing calculations: ( 100 C) C DF
Page 9: DCS/Simulator I/O Mapping On the Si
Page 13 and 14: 4) DCS Staging using the Simulator
Page 15 and 16: OBSERVATIONS AND CONCLUSIONS The Si

Aracruz Uses a Dynamic Simulator for Control System ... - Andritz

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?