THE INTRODUCTION OF distributed control systems (DCS) made it possible to create alarms more easily and at a lower cost. Though software alarms are convenient, the ease with which they can be created removed the incentive to limit alarms. As a result, operators today face more alarms than they can effectively monitor.
When there are too many alarms during an upset, they distract the operator from important events, slowing down his or her response to the upset. They also conceal the actual nature of secondary problems, rather than alert the operator to real problems. At worst, alarms go unnoticed, don’t occur at all, or are misunderstood. In the absence of proper alarm management, plants become less safe rather than safer, incidents become worse rather than better, and production losses increase.
Poorly managed alarms are a disaster waiting to happen. At best, they distract the operator from important events and slow down the response to the upset. At worst, the alarms go unnoticed, won’t occur at all, or are misunderstood.
The following is a set of alarm management tools designed to help plant operators improve their alarm management systems. The tools will help operators identify problems, such as unnecessary alarms and alarms set at the wrong value, and ensure their alarm management system is effective throughout the plant’s lifespan.
1. Collect data. Collect alarm history for at least a month, including all alarms for all consoles along with all operator actions. This data will provide both an original benchmark and the basis for alarm analysis;
2. Analyze. Typically, most nuisance alarms result from a surprisingly small number of actual configured alarms. The initial alarm analysis will quickly identify those alarms most in need of reconfiguring. It will also provide insight into the severity of the current problem;
3. Benchmark. Analyze the alarm history to determine whether the current rate of occurrence is within the EEMUA guidelines for standing alarms, alarm occurrences per shift, and for alarm bursts. Analyze alarms area by area, since some operating units or areas are more prone to alarms than others. Using the alarm history, measure the original performance as a benchmark for comparison to show improvement in nuisance alarms over time;
4. Spend one or two days a month on alarm management. As more alarm history is collected, a senior operator and an engineer should spend a day or two a month to find the worst nuisance alarms and reconfigure them in the DCS. Over the longterm this can have a significant effect; and
5. Measure to confirm that improvements are being maintained. The monthly alarm occurrence statistics will show the frequency of alarms and the number of standing alarms decreasing over time. This can be very powerful evidence of an effective alarm management program.
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