| Alarm management is the
application of human factors (or ergonomics as the field is referred to outside the U.S.) along with instrumentation engineering and systems thinking to the design of an alarm system to increase its usability. Most often
the major usability problem is that there are too many alarms annunciated in a plant upset, but there can also be other problems
such as ineffective annunciation, unclear alarm messages, etc.
The need for alarm management
Alarm management is usually necessary in a process manufacturing environment that is controlled by an operator using a Distributed Control System, or DCS. Such a system may have hundreds of individual alarms, so there needs to be a way to ensure that they are
presented at a rate that can be assimilated by a human operator, particularly when the plant is upset or in an unusual condition.
Alarms also need to be capable of directing the operator's attention to the most important problem that he or she needs to act
upon, using a priority to indicate degree of importance or rank, for instance. A good
example of this problem is from the old US sitcom MASH. A common scene was Radar O'Reilly slipping in a
requisition for something that Hawkeye wanted in the stack of papers for Colonel Potter to sign. In much the same way, if alarms
were unprioritized, the important ones can be mixed in with lower value nuisance ones.
Some improvement methods
The techniques for achieving rate reduction range from the extremely simple ones of reducing nuisance and low value alarms to
redesigning the alarm system in a holistic way that considers the relationships
among individual alarms. As an example, shutting down a pump will always cause a low flow
alarm on the pump outlet flow, so the low flow alarm may be suppressed if the pump was shut down since it adds no value for the
operator, because he or she already knows it was caused by the pump being shutdown.
Alarm management becomes more and more necessary as the complexity of
manufacturing systems increases. A lot of the need for alarm management also arises because alarms can be configured on DCSs at
nearly zero incremental cost, whereas in the past on physical control
panel systems that consisted of individual pneumatic or electronic analog instruments, each alarm required expenditure and control panel real estate, so more
thought usually went into the need for an alarm. Numerous disasters such as Three Mile Island and the Chernobyl
accident have established a clear need for alarm management.
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