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Most major oil and chemical companies have seen the problems associated with operators fighting to save a unit from having to shutdown. Prolonged periods of high alarm actuation rates, constantly changing/shifting conditions, and rapid decisions have resulted in the shutdowns that operators were attempting to prevent. Often the shutdowns come with considerable costs to equipment and the environment. Many companies have taken the approach that rather than fighting the unit, the plants should be “parked,” taken to a safe stable condition until additional personnel are available to reduce the workload. Recent research indicates that this might be a prudent approach.

We all “know” that becoming mentally tired will reduce our ability to perform mental tasks; but how will the reduced ability manifest itself? A study by Dimitri van der Linden, Michael Frese and Sabine Sonnentag gives some insight into what happens when we become mentally fatigued. Dealing with non-routine situations often requires exploration activities to determine the best method for problem resolution.

In this study, exploration strategies were investigated for both experienced and inexperienced subjects (“The Impact of Mental Fatigue on Exploration in a Complex Computer Task: Rigidity and Loss of Systematic Strategies”, Human Factors, V45, No. 3, 2003, p 483-494). With fatigue, exploration strategies became less systematic, more trial-and-error, and more prone to mistakes regardless of experience level. However, the less experienced subjects also showed signs of increased rigidity, continuing to repeat “dead-end” paths or strategies. Knowing that operators dealing with an upset are certainly facing fatigue and therefore likely to become more rigid in their problem solving strategies, parking the unit is probably the safest option.

For further information, visit the links below.

| Alarm & Display System Analysis Overview | Alarm Management | Display Design | Alarm & Display Design Seminar | Beville Shape Calculator -Excel download | Alarm Distribution Estimator -Excel download |


Article Published By
Consortium Reports New Findings on Alarm Rates Automation World
How Many Alarms Can An Operator Handle Chemical Processing
Impact of Alarm Rates and Interface Design on Operator Performance Automation World
Operator Interfaces: Moving from Comfortable to Most Effective Automation World
Operator Performance as a Function of Alarm Rate and Interface Design


This year's Fall meeting for the Center for Operator Performance will be October 7-10 in Houston, TX. For more information, please contact Lisa Via. Guests are always welcome!


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Take our short survey on operator span of control. Click here (new window)

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

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