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WHEN GOOD GUIDELINES GO BAD

NEWSLETTER ARTICLE

As distributed control systems became ever-present in the process industries, alarm management became an industry- wide problem. Many companies were searching for guidance on how to select, prioritize, and display process alarm data. In 1999, the Engineering Equipment and Materials Users Association created a valuable source of data with the publishing of “Alarm Systems: A Guide to Design, Management and Procurement.” The guide was a wonderful source of data and discussion points necessary to create better warning systems for operators. Unfortunately, many companies are now using the guide in ways that (1) are contrary to its stated instructions and (2) could make alarm systems worse.

In many companies, the guide is followed in a prescriptive and unswerving manner. This despite its assertion on Page 10 that, “The guide has been written by users in industry. It is based on what some leading companies are doing, but it is also intended to be challenging and to push standards forward.” The guide’s authors acknowledge that they had taken the first, but not likely the last step in alarm management.

Metrics for the number of alarms in a plant subsystem have become sacrosanct, again in contrast to the guide’s text describing the figures as, “only indicative, but may give some pointer to whether designers are likely to have installed too many or too few alarms on a plant” (Page 103). Likewise, the alarm priority distribution is being set in stone at many locations, defying the instruction accompanying the data in the guide that states, “It is emphasized that the numbers in Figure 24 & Figure 25 [target alarm rates and priority distribution] should be taken as approximate indicators of effective discrimination between priorities rather than exact targets.”

Strict adherence to the guide poses several problems. In some cases, subsequent research, use, and experience indicate that the guidelines can be improved. “Best” practices are precluding better practices. In the worst case, a false sense of security is created whereby some companies feel that their alarm system is infallible because the guidelines have been strictly followed. Users need to be aware of the guidelines intended purpose, always seeking opportunities to improve upon existing practices.

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 |


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