Glossary · HMI, SCADA and operations
Alarm flooding
Also known as: Alarm flood
German: Alarmflut
In alarm management, alarm flooding is a condition in which alarms occur at a higher rate than an operator can effectively handle, for example more than about ten alarms in ten minutes per operator, as used as a guideline in ANSI/ISA-18.2.
- HMI and SCADA
- Process industry
In one sentence
Alarm flooding occurs when alarms arrive faster than an operator can handle, hiding the important ones during upsets.
Example
After a power dip, 400 alarms appear within five minutes because every downstream device reports its own fault, and the operator misses the one alarm that points to the root cause.
Explained in context
Context cards connect this term with others to answer one question. Also in British English and German.
How it applies
- Engineering: Floods are reduced by rationalization, suppression by design of consequential alarms (state-based alarming), deadbands, delays and better alarm priorities.
- Operation: Flood periods are when operators most need clear guidance and are most likely to make errors, a classic Human error setting.
- Documentation: Alarm performance reports track flood periods. Operator training material and emergency procedures should cover what to do first in a flood: identify the first-out or root cause alarm, not work through the list.
- Change: Every new alarm added during a project or modification adds to the flood potential; review additions against the alarm philosophy before commissioning.
Alarm flooding vs. nuisance alarms
Nuisance alarms (chattering or standing alarms) occur in normal operation. Flooding happens during upsets. Both erode trust in the alarm system, but they have different causes and remedies.