A theory/practice widely held in refineries is to keep board operator workload low for steady state operation in order to accommodate the typical step increase in workload that occurs with upsets. This may not only be ineffective, but also counter productive. It has long been known that low levels of workload can negatively affect operator performance. Recent research by Mark Young and Neville Stanton indicates that the low workload problem is both different and worse than previously thought. (Young, M. and Stanton, N. “ Malleable Attentional Resources Theory: A new explanation for the effects of mental under load on performance”. Human Factors, Vol. 44, No. 3, Fall 2002, P365-375)
The performance decrement with low workload has typically been associated with a drop-off in vigilance, which typically occurs after 20-30 minutes on the job. Young and Stanton’s research indicates the problem is more severe. An actual shrinking of available mental workload resources (or mental reserve) is seen after only 10 minutes. Current workload theory has workload resources being fixed or constant, but this came from data looking at overload situations. The new research adds to the old theory – yes, available mental workload resources are limited/fixed in the short term, however they can and do shrink.
Increasing automation and process stability has been shown to reduce the workload on board/console operators at most process plants. If staffing or span-of-control changes are not implemented, under-loaded board operators can result. If the new theory is true, should an upset occur, the reduced workload resources make responding to the upset more difficult than if the base workload is higher. Good intentions of keeping the board lightly loaded for upsets could potentially backfire, actually increasing the probability of operator error at a critical time.
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