SCADA four alarm priorities that should be implemented

• High priority
Alarms that warn of dangerous conditions that could cause a shutdown of a major activity.

• Medium priority
Alarms that should be acted on as quickly as possible; but will not cause a shutdown.

• Low priority
Alarms that should be dealt with when time permits.

• Event only
Statistical or technical information. No enunciator sounds for these. The limiting of the number of types of alarms is to keep the system straightforward and with easy interpretation of the alarms. Higher priority alarms should be louder; lower pitched and have a higher pulse frequency than the lower priority alarms. Alarms are classified as unacknowledged (and flashing on the screen) until the operator acknowledges them via the keyboard. They then become an accepted alarm. One weakness in many alarm systems is the occurrence of trivial alarms, which irritate and confuse the operator.