Alarm flood management: stop one hydro blip sending 50 texts

Q: Can Welco skip return-to-normal messages?

Yes. An alert rule can match words like NORMAL or CLEARED and leave those messages out of texts. They still reach email if your system sends them there, so you keep the full record without waking anyone up.

An alarm flood is a burst of alarms from one root cause, like a hydro blip in an ice storm or a failed switch. Good alarm flood management fixes chatter at the source, keeps all-clear messages out of texts and caps the burst. The on-call phone then shows the cause, not a wall of noise.

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Published: October 6, 2026

The problem

A hydro blip at 1:30 a.m.

48 alarm emails in 3 minutes
48 texts on one phone
The real cause is buried

The fix

A few texts that explain it

The transfer alarm comes first
All-clears stay in email
Flood control caps the rest

Most floods start with one event that knocks over many points at once.
Fix chattering points in the control system first. Texts can't fix a noisy sensor.
Send the parent alarm, skip the all-clears, and cap bursts with flood control.
Your alarm system still logs every event, even when the phone gets only a few texts.

Why alarm floods happen

A flood is rarely 50 separate problems. It is one problem seen by 50 points. When power dips, every drive, pump and sensor on that panel reports a fault in the same minute. This is one of the most common problems in our SMS alert guides.

Texts make floods worse than they are on a control screen. An operator at the console sees a list. The on-call phone buzzes 50 times, and the cause sits somewhere in the middle. Bursts of near-identical texts are also one reason carriers block alert texts.

Why floods hurt more at night

During the day, a crew on site sees the cause and starts fixing it. At night, one person reads the burst on a small screen, half awake.

That person has to decide fast whether to drive in. A clear first text makes that call easy. A pile of 50 makes it a guess. The on-call routing basics guide covers who should carry that phone.

The usual causes

Power events: a hydro blip, often from wind or ice on the lines, or a generator transfer trips many devices at once.
Network failures: a dead switch makes every device behind it look down.
Chattering points: a level or pressure sensor near its limit flips in and out of alarm every few seconds.
All-clear messages: each alarm sends a second email when it returns to normal, doubling the count.
Backed-up mail: a mail server comes back online and releases an hour of queued alarms together.

How many alarms count as an alarm flood?

In plant control rooms, a flood starts when one operator gets more than 10 new alarms in 10 minutes. A March 2016 Chemical Engineering article from Emerson sets out the EEMUA 191 version. The flood lasts until a 10-minute window brings fewer than five new alarms. The same article lists these common targets, drawn from EEMUA 191 and ISA-18.2.

Targets were written for console operators. A person reading texts in the dark needs a stricter bar.

New alarms per 10 minutes, on average

Common target for one operator: 1 to 2
What it means for an on-call phone: A quiet night should bring few texts, or none

Most alarms in any 10-minute window

Common target for one operator: 10 or fewer
What it means for an on-call phone: Ten texts in ten minutes is already too many to read half awake

Share of time spent in a flood

Common target for one operator: Under 1%
What it means for an on-call phone: A burst should be a rare event you can name, like a storm

Targets were written for console operators. A person reading texts in the dark needs a stricter bar.

New alarms per 10 minutes, on average	1 to 2	A quiet night should bring few texts, or none
Most alarms in any 10-minute window	10 or fewer	Ten texts in ten minutes is already too many to read half awake
Share of time spent in a flood	Under 1%	A burst should be a rare event you can name, like a storm

Sources: Emerson reprint of Chemical Engineering: Alarm management by the numbers (March 2016) (read October 6, 2026); UK Health and Safety Executive: Better alarm handling, CHIS6 (March 2000) (read October 6, 2026)

Why the alarm count matters

Past a certain rate, people stop reading alarms and start guessing. The UK Health and Safety Executive's alarm handling information sheet (March 2000, read October 6, 2026) gives the clearest case.

In the last 11 minutes before the 1994 explosion at the Texaco Milford Haven refinery, two operators had to deal with 275 alarms. The sheet asks sites to aim for no more than ten alarms in the first ten minutes after a major upset.

One phone in the dark has far less room than a two-person control room. That is why flood management starts at the source and ends with a cap on texts.

Bring alarm floods under control in 6 steps

Start at the source and work toward the phone. The early steps cut the most noise.

Find your worst hour
Look through last month's alarm emails and find the hour with the most messages. Note what started it. That event is your first target.
Calm chattering points at the source
In the PLC or SCADA software, add a small deadband or an on-delay to points that flip in and out of alarm. A few seconds of delay stops most chatter without hiding a real fault.
Alarm on the parent, not every child
Monitoring tools can mark a switch as the parent of the devices behind it. When the switch fails, you get one alarm for the switch instead of one for every device.
Keep all-clears out of texts
Set an alert rule that skips messages with words like NORMAL, CLEARED or RTN. They stay in email for the record and stop doubling your texts.
Turn on alarm flood control
Use alarm flood control to limit how many texts a burst can send. The first alarms get through, and the phone stays readable.
Check for doubled emails
If each alarm arrives twice, look for two forwarding rules or a mailing group that copies it. Welco sends each email to each phone once, but two separate emails are two alerts.

Turn a burst of alarms into a few clear texts

Point your alarms at Welco and switch on flood control.

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Example: the alarm that explains the flood

During a hydro outage at a municipal water plant, the transfer switch alarm arrives first. It tells the on-call person what happened, so the drive and pump faults that follow make sense.

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With all-clears skipped and flood control on, this text and a handful of others reach the phone. The full list stays in the control system.

What alarm rationalization means for text alerts

Alarm rationalization is a line-by-line review of every alarm: does it need to exist, and how urgent is it? The ANSI/ISA-18.2-2016 standard (read October 6, 2026) makes it one stage of managing alarms in process plants.

For texts, a short version works. For each alarm that can text, write down who acts, how fast, and what they do. If nobody can name the action, that alarm shouldn't text anyone.

Text the cause, not every symptom

One event often shows up as several alarms. A pump that trips can also raise low flow and low pressure alarms downstream.

Text the pump trip, and let the flow and pressure alarms stay in the log. The person on call learns the cause from one text and can read the rest at the console.

What happens to alarms that flood control holds back?

They are not texted, and they are not saved to send later. An alert email that arrives after the hourly limit is bounced back, while your alarm system keeps its own full record.

Flood control counts emails, not alarm points. A point that alarms five times sends five emails, and each one can become a text until the limit is reached.

No setting silences one repeating alarm for a fixed time, so the cure for repeats lives in the control system. Welco does stop a single email from texting the same phone twice, through duplicate protection.

Who gets the texts during a flood

Only the phones set for that alarm and that hour. With after-hours routing, a 2 a.m. storm reaches the on-call phone, not the whole team.

How to tell if your alarm flood management is working

Pick one bad night from last month and count what the on-call phone received. Then compare it with a similar night after the changes.

The first text of a burst names the root cause, such as the power loss or the failed switch.
No chattering point sends more than a couple of texts in an hour.
No all-clear messages reach the phone after midnight.
Staff say they read every alarm text again, instead of skimming.

Alarm flood mistakes to avoid

Each of these feels like a quick fix during a bad week. Each one makes the next flood worse.

Raising the text limit instead of fixing the chatter. A bigger cap just lets more noise through.
Texting every child device. Without parent links, one dead switch becomes dozens of texts.
Sending all-clears at night. Good news can wait for the morning email.
Sending the burst to the whole team. Ten people woken by one winter storm is ten times the fatigue.
Switching flood control off after one bounced alarm. Fix the order instead, so the cause texts first.

Alarm flood checklist

Work down this list for each system that sends alarms.

0 of 7 done

The worst alarm hour of the past month is known.
Chattering points have a deadband or delay set.
Network devices have parent links in the monitoring tool.
All-clear and return-to-normal messages skip texts.
Alarm flood control is on.
Each alarm email arrives once, not twice.
A test burst showed only a few texts on the phone.

Frequently asked questions

What counts as an alarm flood?

A burst of alarms faster than one person can read and act on them. Plant benchmarks put the line at more than 10 new alarms in 10 minutes for one operator. For one on-call phone at a small Canadian utility, even fewer is too many. Most floods come from one event, like a hydro outage, that many points report at once.

Will flood control hide a real alarm from me?

It limits how many texts a burst can send, so later alarms in the same burst may not become texts. That's why the source fixes matter: they make sure the alarm that explains the burst arrives first. Every event still sits in your alarm log.

How do I stop a chattering sensor from texting the on-call operator all night?

Fix it in the control system. Add a deadband, so the value must move clearly past the limit, or an on-delay, so it must stay in alarm for a few seconds. Then check the sensor itself, since chatter often means it is failing.

Can Welco skip return-to-normal messages?

Yes. An alert rule can match words like NORMAL or CLEARED and leave those messages out of texts. They still reach email if your system sends them there, so you keep the full record without waking anyone up.

Why does each alarm reach my phone twice?

Usually the alarm system or mail server sends two separate emails, for example through two forwarding rules. Welco sends each email to each phone once, but it treats two emails as two alerts. Remove the extra forwarding rule to fix it.

Do alarm emails bounced by flood control use credits?

No. Credits are used only when an email becomes a text to a phone. An email bounced at the hourly limit never becomes a text, so it costs nothing. The texts that did go out during the burst use credits as normal.

How do I find which alarm points cause the most noise?

Count last month's alarm emails by subject line or tag name. In most systems a handful of points send most of the mail. Fix those first, with a deadband, a delay or a parent link, and the next flood shrinks the most.

Reviewed by Rakesh Patel, Founder, Welco

Keep your next power blip to a few texts

Switch on flood control and skip the all-clears today.

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