The alarm flood scenarios lasted from 8 to 10 minutes. The average alarm rate across the flood scenarios was 110 per 10 minutes, with a range of 32 to 316 total alarms. The number of unique alarms averaged 30 per 10-minute scenario, with a range of 14 to 42. The number of plant equipment areas ranged from 6 to 11.
In the familiarity training session, operators were shown an "effective" alarm response strategy to help improve situation awareness during alarm flooding situations. This effective strategy, which could be used with the traditional list-based display as well as with the new alternative displays, comprised:
• using the summary view to determine what equipment area required attention;
• selecting just that area for viewing in the alarm list;
• evaluating the pattern of alarms in that area;
• completing the alarm response task in an Access database form;
• returning to the alarm list; and
• acknowledging all alarms (as opposed to acknowledging individual alarms).
Less effective strategies were characterized by:
• not focusing the alarm list by equipment area and acknowledging all alarms in the alarm list while all units were shown; or
• not focusing the alarm list by equipment area and only acknowledging single alarms.
The trial generated three key findings:
1. The effectiveness of a particular display design can be influenced by the alarm response strategy used when interacting with that display. The study results found both effective and ineffective strategies for all three alarm-summary display designs. Most importantly, all three designs provided features that enabled operators to strategically focus the contents of the detailed alarm list view on a specific equipment area of interest to reduce the number of alarms seen. Significant positive correlations were found between the operators' alarm response score, indicating better situation awareness, and their respective effective strategy score. Moreover, the benefit of the effective alarm strategy was greater with the time-based overview visualization technique than with the traditional list-based alarm summary display. This strategy was impactful because it allowed the operators to be aware of more alarm conditions and see patterns in the alarms associated with an equipment area that were not readily perceptible when distributed within the list of all alarms.
2. The effective response to alarm flood conditions may depend upon operator training. Another observation from the study was that — despite the project team purposefully training each operator on the effective strategy of using the summary view to focus what equipment area was in the alarm list — many operators reverted back to the strategy they brought to the study, based on how they interact with the existing DCS alarm summary display (similar to the industry-typical display used in the study). The consequence of this very common behavior was that each of the three display conditions essentially was reduced to a single alarm list, with no summary information being used. The training session didn't include feedback on performance. Hence, some operators thought they actually performed better when they didn't use the effective alarm response strategy. In fact, some had the mistaken perception they were performing better because they were aware of fewer alarms, i.e., they weren't aware of what they weren't responding to. Training that includes feedback on performance has a better chance of establishing the value of using the effective alarm response strategy.
3. With the option to choose display type, the operators prefer the new time-based display to the traditional display. An alarm summary display with the time-based overview was installed in a control room for three months to allow operators to get familiar with the display during a pilot study period. That control room has two console areas, each devoted to a specific processing unit. In one console area, half the operators chose to use the new display over the traditional display during their normal shift duties. In the other, all the operators opted to use the new display. Operators reported they were better able to associate groups of alarms with specific equipment areas and contextualize alarms in time in terms of old and new concerns. After the pilot was completed, the operators requested the prototype display be left in the control room.
In conclusion, the ASM research studies revealed some promising findings on alarm presentation techniques that can enable operators to better manage plant upset situations that result in alarm floods. Past research has revealed significant usability issues with the traditional presentation in list format. The Sasol trial showed that console operator performance improved with all the alarm presentation techniques when an effective alarm response strategy also was used. Specifically, the study demonstrates that operator performance under alarm flood conditions can be upgraded if the operator interface allows the operator to strategically view subsets of the alarms associated with specific equipment areas rather than a list containing all the alarms. The time-based overview visualization coupled with an effective alarm response strategy produced the best alarm awareness. Future research examining the impact of potential enhancements to the new display concepts might provide additional insight on how to resolve this significant challenge in the process industries. Meanwhile, Sasol has chosen to adopt the new visualization developed on the Honeywell Experion platform as the Alarm Tracker display.
PETER T. BULLEMER is Independence, Minn.-based senior partner of Human Centered Solutions. DAL VERNON C. REISING is Canton, Mich.-based senior partner of Human Centered Solutions. MISCHA TOLSMA had been divisional manager, instrumentation and control engineering, for Sasol, Secunda, South Africa, during the time of the trial; he now is senior operations management engineer for Shell Global Solutions, The Hague, Netherlands. JASON C. LABERGE had been leader at Honeywell's Human Factors Center of Excellence, Golden Valley, Minn., when this trial took place; he now is manager of human factors for Alberta Health Services, Calgary, Alberta. E-mail them at firstname.lastname@example.org, email@example.com, Mischa.firstname.lastname@example.org and email@example.com.
1. Bransby, M., "Design of Alarm Systems," p. 207 in "People in Control: Human Factors in Control Room Design," J. Noyes and M. Bransby, eds., Institution of Electrical Engineers, London, U.K. (2001).
2. Brown, W., O'Hara, J. and Higgins, J., "Advanced Alarm Systems: Guidance Development and Technical Basis," (NUREG/C$-6684), U.S. Nuclear Regulatory Commission, Washington, D.C. (2000).
3. Bullemer, P. T., Tolsma, M., Reising, D. C. and Laberge, J. C., "Towards Improving Operator Alarm Flood Responses: Alternative Alarm Presentation Techniques," Proceedings of the ISA Automation Week Conference (Chicago, Ill.), ISA, Research Triangle Park, N.C. (2011).
4. Laberge, J., Bullemer, P., Tolsma, M., and Reising, D., "Addressing Alarm Flood Situations in the Process through Alarm Summary Display Design and Alarm Response Strategy," accepted for publication in Intl. Journal of Industrial Ergonomics.