4.2.3-6 Cleared Alarms That Re-Enter the Abnormal Range

If an alarm has cleared but was not reset and the variable re-enters the abnormal range, then the condition should be presented as a new alarm.

Additional Information:
When an alarm clears, the operator is informed via the ringback feature that the value is now in its normal range. Since the operator might expect the parameter to remain in the normal range, the alarm system should alert the operator when the parameter deviates from the normal range. If the variable again enters the abnormal range, the alarm system should behave as it does for new alarms, by producing visual and auditory signals to alert the operator. For cases in which a variable might move (e.g., oscillate) in and out of the normal range, alarm processing should be used to prevent the frequent reoccurrence of the alarm from becoming distracting to the operator. One technique might be to require the parameter to move further into the normal range before the alarm clears. Another technique might be to require the parameter to remain within the normal range for a particular amount of time before allowing the alarm to clear.