Accurately Determine Console Operator Workload

Determining the correct console operator workload requires more than simply counting control loops.

By Ian Nimmo and John Moscatelli,User Centered Design Services LLC

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Alertness and fatigue. A console operator at a modern plant is expected to be awake, alert and ready to take decisive action at a moment’s notice. However, we frequently provide working conditions that actively work against this goal. Are light levels kept low? This is often done to combat glare on the DCS screens, which is caused by poorly designed lighting systems, or to reduce the eye strain caused by black DCS-screen backgrounds. Is the ventilation poor, causing extreme changes in temperature? Are the air vents filthy and is the air quality poor? Do schedules allow, or even require, operators to work excessive overtime and consecutive days so that they can’t get adequate rest? All these issues create, at best, an uncomfortable environment and, at worst, one that causes the operators to be drowsy and inattentive.

Don’t expect a simple answer
At the beginning of this article we arrived at that common plant management question: “What’s the right number of operators for our facility?” The simple answer to that question is that there is no simple answer, no effective short-cuts, and no guidelines that can be safely applied.

Reducing staffing levels should be viewed as a long-term, continual process. You can start by identifying areas that can be improved to facilitate staffing reductions. Then implement changes in those areas as resources become available and follow that up with feasible reductions. Almost all plants can achieve a reduction in staffing levels, but attempting to make a significant reduction in personnel without addressing other areas of concern might be difficult and possibly create a dangerous situation.

Ian Nimmo is president and founder of User Centered Design Services, Anthem, Ariz., a firm that specializes in abnormal-situation management, alarm management and other control issues. E-mail him at John Moscatelli is the managing partner of User Centered Design Services. E-mail him at

1. Contra Costa County Ordinance No. 98-48 and amendments from 2000-20 Industrial Safety Ordinance (1998).
2. Brabazon, P. and H. Conlin, “Assessing the safety of staffing arrangements for process operations in the chemical and allied industries,” contract research report for the Health and Safety Executive (2001).
3. Parker, S.K. and H.M. Williams, “Effective teamworking: Reducing the psychosocial risks,” HSE Books, Norwich, England (2001).



Example 1:
An independent refiner wanted to perform a staffing analysis in conjunction with the building of a new, central control room. The operators had inside/outside responsibilities and a small span of control. The refiner planned to create dedicated console operator positions and move these operators into the new control room.

The staffing analysis identified which units should be combined under the control of a single operator, as well as a reasonable target number of operators. Although this refiner had some management-system issues to address, we were able to safely recommend console operator staffing reductions of 30%, with another 12% that could reasonably be achieved after some improvements in the management systems. This was significantly higher than the refiner had anticipated.

Example 2:
Another independent refiner had dedicated console operators working out of a number of shelters located throughout the site. This company also planned to consolidate operations in a new state-of-the-art, centralized control building and wanted to perform a staffing analysis in conjunction with the project. The facility manager had preconceived ideas as to the correct staffing levels. He expected to reduce the number of console operator positions by 50% and thought the study would validate this figure.

The workload model, which includes the equipment, interaction and control system scores, indicated that the proposed consolidations were aggressive, but not beyond workload levels that were being handled successfully at other facilities. However, the management system review showed significant gaps in the areas of training, console operator selection, procedures, communication systems, teamwork and willingness to act.

As a result of the study, the refiner decided to focus efforts on making improvements to the management systems to ensure that the proper support system would be in place to support the new positions.

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