Industrial Engineer · phase 6 of 16
Alarm
Reported abnormal condition that requires operator or maintenance attention but does not necessarily stop control.
The Explain card
- Plain English
- An alarm is the machine telling a person that something is outside normal. It might stop the process and it might only flash on a screen, depending on how serious it is.
- Example
- Tank level passes 90 percent and a high level alarm appears on the HMI with a horn. At 95 percent a high high alarm stops the fill pump.
- Why it matters
- Alarms exist for people, so an alarm nobody can act on is noise, and a screen full of noise hides the one that matters. Every alarm should have a priority, a cause and something the operator is supposed to do about it.
- Hook
- If nobody has to act, it is a light, never an alarm.
Where it sits in the deck
Phase 6: PLC Operating Modes, Safety, and Diagnostics
Run, program and fault: what a controller does when something goes wrong, and the safety functions that decide how much that costs.
