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Alarm Management/Alarm Response Analysis
Beville Engineering, Inc., has been conducting
alarm response analyses in the petrochemical industry for over 20 years. As such, we have developed a comprehensive approach and
methodology that has enabled significant improvements in alarm
systems for a variety of clients. The following highlight some of
our results:
- A reduction of alarms per day from 300 to 100
- A decrease in emergency priority alarms from
40 to 13 percent of the alarm total
- A reduction of alarms "in" during normal
operations from an average of 15 to 0
- An 80 percent reduction in the number of
emergency alarm activations
Alarm system management is universally recognized
as essential to ensuring that processing plants are run safely and
efficiently. Alarm system management is are also universally
recognized as being problematic. It is ironic that a system that is
so essential is often the source of so many problems. Stories of
operators missing or misunderstanding alarms and wreaking havoc on a
process are all too familiar. There are tell-tale signs that an
alarm system is poorly configured. Characteristics of poorly
configured alarm systems include:
Alarms that have no operator action,
- Alarm conditions that have multiple alarms,
Alarms that are "in" during normal operations, violation of the
"dark screen" principle,
- Alarm actuation rates in excess of the
operator's information processing capabilities,
- Alarms with improper setpoints or deadband,
causing alarm cycling,
- Excessively high alarm-to-controller ratios,
and
- Alarm priority distribution that has too many
emergency and high priority alarms and too few low priority
alarms.
Although problems with alarm system management may
be easy to identify, identifying the solutions to the problems is
not so simple without a substantial amount of knowledge and
experience. Conceptually, selecting alarms is not difficult:
each alarm should prompt a unique operator action. If there
is no action, there should be no alarm. If multiple alarms all
prompt the same action, there shouldn’t be more than one alarm.
Systematic application of this principle is done
through an alarm response analysis (ARA). All of the pertinent data
for each point to be alarmed is entered into a customized database
form during the ARA. The data that is captured is then used to
determine what points need to be alarmed, deleted or changed. This
method of cataloging each point's data provides documentation for
any changes that are made and works as a control for future alarm
additions. The ARA form becomes part of the management of change for
alarms.
Several rules-of-thumb exist for determining if
the alarm selection process was successful. The total number of
alarms for a system should be a 2.5:1 ratio of alarms to
controllers. For example, a unit with 200 controllers should have
about 500 alarms. These alarms should have a priority distribution
of the following:
Level 1 - 10%
Level 2 - 35%
Level 3 - 55%
For further information, visit the
links below.
Alarm & Display
System Analysis Overview /
Display Design
/ Alarm
& Display Design Seminar /
Alarm Response Analysis
Webcasts /
Shape Calculator /
Alarm
Distribution Estimator (excel - new window)
View all related
Alarm/Display newsletters by
clicking here
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