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Chemical processing plants are inherently complex systems. Product typically flows through many stages, with the upstream stages affecting the downstream stages. For example, product rundown is commonly used as the heat medium for the charge. A fault in one system almost always produces a ripple effect, causing other systems to be affected. In such a complex system, correctly diagnosing the root cause of a fault can prove to be time consuming and difficult.

The fundamental method to improve the operator's problem solving ability is through training. Through training, it is hoped that necessary skills and knowledge are imparted to the operator which will make him adept in identifying and correcting problems. A key question arises, which is, "How should they be trained?" Should training be mostly theoretically based or rule based? Researchers have been conducting studies to determine what type of training is most beneficial in fault finding at process control boards.

"Diagnoses of Plant Failures from a Control Panel: A Comparison of Three Training Methods," Ergonomics, 1977, Vol.20, No.4, 347-361, investigated the success rate of accurately recognizing faults practiced during training and, in addition, provided a strategy toward diagnosing unfamiliar faults. Three groups were presented with different training on the plant. The "Theory" group was presented with the conventional description of the "Plant" and its functions. The "Rules" group, in addition, was taught a set of rules to assist them in inferring failures from the panel. The third group, or "No Training" group, was given no training.

Results of the study indicate the effects of different training to the plant. For diagnosing familiar faults (or re-occurring faults), the group equipped with diagnostic rules attained 80% accuracy while the "Theory" and "No training" groups achieved 65% and 49%, respectively. The subjects supplied with diagnostic rules performed more accurately and although their speed was slower, they used this time effectively in applying the rules. In diagnosing unfamiliar plant failures, the "Rules" group was clearly the most skilled. This group achieved 70% accuracy with the new faults.

The results of the experiment suggest that there is little to be gained by teaching 'theory' alone. The operators with the conventional theory and diagnostic rules are more successful and accurate in recognizing familiar and unfamiliar faults.

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This year's Fall meeting for the Center for Operator Performance will be October 24-26 in Corpus Christi. For more information, please contact Lisa Via. Guests are always welcome!


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David Strobhar's book, "Human Factors in Process Plant Operation," is now available in both hardcover and Kindle e-book.

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