Most process plants strive to enhance their productivity and extend their asset life. One of the easiest and most effective ways to achieve such improvements is to address alarm system problems that undermine operator performance. After all, operators typically have more influence on product quality, raw material usage and energy utilization than any other production variable. Even at the most highly automated plants, yield, rate, quality and resource utilization often vary shift to shift because of operator impact.
Unnecessary alarms, such as ones that just provide information or don't require an action, reduce productivity, add stress, and take time away from managing the process. Transforming the alarm system from a hindrance to a help can significantly enhance operators' effectiveness. So, here, we'll describe how to create a program to optimize the alarm system by following the alarm management lifecycle defined in the ISA-18.2 standard "Management of Alarm Systems for the Process Industries" .
To determine how bad your alarm system is you need alarm rates and other key alarm system performance indicators to compare to industry benchmarks. Control system vendors and alarm management specialists offer excellent alarm analytic tools. However, you can obtain useful insights just by taking a clipboard into your control room and charting what happens in a typical 20-minute period. If your control room is like that of most plants without a formal alarm system management program, you'll probably see results similar to those in Table 1.
ISA-18.2 guidelines for incoming alarm rates state that an average of one alarm every 10 minutes is very likely to be acceptable, while the maximum manageable rate is two alarms per 10 minutes . Our 20-minute sample averaged four alarms per 10-minute interval, which is beyond the maximum manageable rate. The operators acted on only two of eight new alarms and ignored 12 standing alarms, which also indicates the alarm system is performing poorly and causing undue operator interruption. Moreover, the operators acknowledged all eight alarms but only acted on two, meaning they appear to be deciding for each alarm whether it represents an abnormal condition and warrants an action (likely undocumented).
THE IMPORTANCE OF ALARM MANAGEMENT
Poor alarm system performance has significantly contributed to many well-publicized industrial accidents. The consequences of such incidents coupled with new regulations like the U.S. Pipeline and Hazardous Materials Safety Administration's 49 CFR 195.446 (Section e focuses specifically on alarm management) and heightened insurance industry scrutiny provide compelling motivation to create a sustainable alarm system performance improvement program. Such a program can do much more than just avoid costly incidents — it also can add dollars to the bottom line. A properly managed alarm system should deliver positive measurable increases in operational performance regardless of shift.
Key elements for achieving operational benefits are:
• Nuisance alarm elimination. Ensuring that alarms are meaningful and relevant allows operators to focus on the process with minimum interruptions. The 80/20 rule is definitely true for most plants with no alarm management improvement program in place — a small number of fleeting, chattering or otherwise faulty alarm sources contribute to a majority of all alarms.