Topic
Alarms
33 guides across the knowledge base.
Permissives
The conditions that must be true before a device may start: how permissives differ from interlocks and trips, the list a pump or feeder usually needs, coding them so the HMI can say why a start was refused, and the rules for time delays and bypasses.
9 min readUpdated Sep 5, 2026
Alarms in the Controller
Generating alarm conditions in the controller rather than in the graphics: why the PLC should own the alarm state, a standard alarm block with setpoints, deadband, and delays, equipment alarms, and packing alarm bits for SCADA.
9 min readUpdated Sep 5, 2026
Signal Validation
Catching a failed analog input in logic before it runs a pump on a dead transmitter: range checks, module status bits, frozen-value detection, rate checks, and what the program does with a bad value.
8 min readUpdated Sep 5, 2026
The Alarm Philosophy
The document that decides what is allowed to be an alarm: the definition, the criteria, the priorities and their meaning, the performance targets, the handling rules, and who owns it. Under ISA-18.2 it comes first.
9 min readUpdated Sep 5, 2026
Alarm Priority
How to assign alarm priorities that operators trust: a consequence-and-time matrix, three or four levels, the target distribution from ISA-18.2 and EEMUA 191, and the mistakes that make every alarm high.
9 min readUpdated Sep 5, 2026
Alarm Rationalization
The meeting where every alarm earns its place: who attends, what is decided for each alarm, how to document it in a master alarm database, and how to run it at a utility that cannot spare a week.
10 min readUpdated Sep 5, 2026
Alarm Floods
What an alarm flood is, why it happens at exactly the wrong moment, the ISA-18.2 rate targets, and the design measures that keep a power failure or a communication loss from burying the one alarm that matters.
10 min readUpdated Sep 5, 2026
Alarm Notification and Callout
Getting the alarm to the person on call when no one is watching the screen: notification paths, escalation, acknowledgment from the field, which alarms qualify, and the failure modes that leave a station in high level with nobody paged.
10 min readUpdated Sep 5, 2026
Alarm Indication on the HMI
How an alarm looks and sounds on the operator screen: the ISA-101 and ISA-18.2 rules for color, shape, and blink, the alarm banner and summary, acknowledgment behavior, navigation to the alarm, and indication that survives colorblindness and a noisy control room.
10 min readUpdated Sep 5, 2026
Alarm Servers
The part of SCADA that turns a condition into an alarm and manages its life: where detection happens, the alarm state machine, priority, deadband and delays, acknowledgment across clients, the journal, notification, redundancy, timestamps, and flood behavior.
10 min readUpdated Sep 5, 2026
Color in HMI Design
How color is used on a high performance HMI: a gray palette for normal operation so that color means something, alarm colors reserved by priority, equipment state by fill and text rather than red and green, color-blind safe choices, and the palette table.
9 min readUpdated Sep 5, 2026
Situational Awareness
Designing displays so an operator knows what is happening, what it means, and what comes next: the three levels of awareness, the display hierarchy, analog indicators with normal ranges, embedded trends, time-to-limit predictions, and a test for any display.
10 min readUpdated Sep 5, 2026
Alarm Shelving
The operator tool for temporarily silencing a nuisance alarm: what shelving is and is not, the rules a philosophy sets, who may shelve what and for how long, automatic unshelving, the shelved list, the record, and how to implement it on any platform.
8 min readUpdated Sep 5, 2026
Alarm Suppression
Suppressing alarms by design: state-based logic that removes alarms that mean nothing in the current state, parent-child logic that stops a flood at its source, out-of-service suppression for maintenance, the rules that keep it safe, and how to test it.
9 min readUpdated Sep 5, 2026
Alarm Problems
How an alarm system fails: alarms that never raise, raise unheard, stick, chatter, or flood, acknowledgments that do not propagate, and notifications that never arrive, with the causes by layer and the end-to-end test that proves the whole chain.
9 min readUpdated Sep 5, 2026
Rockwell FactoryTalk
Field notes on the Rockwell Automation FactoryTalk family: View Site Edition and Machine Edition, the directory, Linx with direct controller tag access, device-based Alarms and Events, the PI-based Historian, ViewPoint and Optix, redundancy, and site checks.
8 min readUpdated Sep 5, 2026
Digital Signals
Discrete signals between instruments and controllers: dry and wetted contacts, sinking and sourcing transistor outputs, two-wire sensor leakage, NAMUR sensors with wire-break detection, contact ratings at low current, and wiring conventions.
8 min readUpdated Sep 5, 2026
Lift Station High Level
The alarm that stands between a lift station and an overflow: where the high-level float goes, what it must do on its own, how much response time the well provides, and how to diagnose a high level that should not be happening.
11 min readUpdated Sep 5, 2026
Aeration
Aeration in drinking water treatment: stripping carbon dioxide, hydrogen sulfide, radon, and volatile organics, and oxidizing iron and manganese ahead of filtration. The aerator types, what each needs from the control system, the pH shift, and the interlocks.
9 min readUpdated Sep 5, 2026
Chemical Feed
Chemical feed from the control side: the chemicals and where they go, metering pumps and dry feeders, flow pacing with residual trim, the dose arithmetic, day tanks and drawdown tests, loss-of-feed detection, interlocks, and overfeed protection.
11 min readUpdated Sep 5, 2026
Finished Water Storage
Storage inside the plant: the clearwell that provides contact time and high service suction, backwash supply tanks, and how their levels drive production and pumping. The contact time calculation and the minimum level it demands, water age, and alarms.
9 min readUpdated Sep 5, 2026
Lift Station SCADA
Getting a remote station onto the SCADA system and keeping it there: which signals to bring back and which controls to allow, the telemetry path from licensed radio to cellular to fiber, and the maintenance that keeps the link up.
9 min readUpdated Sep 5, 2026
Effluent Disinfection
Disinfecting the effluent and proving it: chlorination with contact time and residual control, dechlorination with sulfite controlled by ORP or a residual analyzer, ultraviolet systems with dose control from flow, and the records the discharge report needs.
9 min readUpdated Sep 5, 2026
Program Change Detection
Knowing when a controller program changed and whether it was supposed to: change counters and signatures the SCADA can alarm on, scheduled compares, audit logs, mode and network monitoring, what each catches, and what to do when one fires.
9 min readUpdated Sep 5, 2026
Firewall Logging and Review
Making the firewall log useful: logging on every rule including sensitive permits, sending logs to a collector off the firewall, what denials and unexpected permits mean, a weekly review a small utility can sustain, and the alerts worth waking someone for.
8 min readUpdated Sep 5, 2026
How to Add an Alarm
From a request to a working alarm: define it against the philosophy, build the condition in the PLC with deadband and delays, configure the SCADA alarm with priority and message, test it end to end, and record it in the master alarm database.
9 min readUpdated Sep 5, 2026
How to Configure Alarms
Configure alarms in the SCADA system from the alarm list: set the source, controller-generated or evaluated in SCADA, the limits and deadband and delay, and the notification; then test each alarm end to end and review the alarm rate after the first weeks.
8 min readUpdated Sep 5, 2026
Alarms Not Annunciating
The condition is real and nothing happened on the screen or the phone: where an alarm can be lost between the controller and the operator, from the alarm bit and the tag quality to the alarm server, the display filter, the shelved and suppressed lists, the audible, and the notifier.
9 min readUpdated Sep 5, 2026
Seal Failure Alarm
The moisture probe in a submersible pump has tripped its relay: a seal that is leaking, or moisture in the cable, the junction box, or the probe circuit, a relay that does not match the pump, or a failed relay. What the alarm should do and what to check.
8 min readUpdated Sep 5, 2026
Calibration Checklist
The checklist for one calibration event, from work order to the sticker on the instrument: notify operations, loop in manual, alarms inhibited, the reference standard, as-found, adjustment, as-left, the loop check, restoration, and the record.
8 min readUpdated Sep 5, 2026
The Lift Station That Overflowed With Everything Working
A composite of overflows that happen at well-built stations: every pump ran, every alarm fired, every device did what it was designed to do, and the handful of changes that break the chain.
9 min readUpdated Sep 5, 2026
Alarms Nobody Answers
A SCADA system that raises eight hundred alarms a day has trained its operators to ignore it. How a small plant gets there, what the standing alarm list is telling you, and a one-day rationalization that gives the alarm system its voice back.
9 min readUpdated Sep 5, 2026
ISA-18.2 Alarm Management
The lifecycle standard for alarm systems, the rate targets that define a workable system, and why alarm rationalization is the step nobody wants to fund.
10 min readUpdated Aug 15, 2026
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