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

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.
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