The alarm is set at priority level 4, which means “critical,” but it doesn’t stand out because almost all of the alarms at the facility are set at that level. Besides, the operator can’t acknowledge the alarm right away because he’s dealing with several other alarms that went off a few minutes earlier. The operator hasn’t yet realized that the earlier alarms were triggered by a pump that’s turned off, as it’s supposed to be at this state of the treatment process. A few minutes later, before he’s gotten around to checking the alarm set off by the tank, yet another set of alarms goes off. The operator, who knows that almost all of the alarms in the facility prove to be “nuisance alarms” and who’s tired near the end of a busier-than-usual workday, decides to silence all the alarms at once. As a result, he remains unaware that the high water pressure in the tank is being caused by an input valve that was left partially open. Despite all of this alarm activity, a serious problem has gone unaddressed and it will only get worse as time goes on. The scenario you’ve just read is fictional, but situations like it frequently occur in the real world, in all types of industries. Why are situations like these so common? Why is it that alarm systems so often mutate from a useful resource into a distraction that complicates problems more than it helps solve them? It’s usually because changes are made to an alarm system over time without being carefully managed. Organizations tend to set up an excessive amount of alarms and eventually lose sight of their purpose. Eventually, there are so many false or unnecessary alarms that the personnel often ignores them. The irony is that a flood of alarms can make the root problems harder to detect. If a serious problem is overlooked, it can result in losses of time, resources, money or, in the worst cases, life and limb. Slowly but surely, the whole purpose of the alarm system will be defeated unless these types of changes are recognized and corrected.
Inductive Automation (2013) Smarter SCADA Alarming