Dynamic Alarming Reality
Chris Wilson - Marketing Manager, TiPS Incorporated
Many people incorrectly interpret "dynamic alarming" as an easy fix for too many alarms. At face value it's a very attractive concept - Just
put a big blanket on top of all that mess and the blanket will be smart enough to let the important stuff through.
That's a really neat concept, but look under the hood and you'll find that the time and labor required to successfully implement dynamic
alarming are higher than you might have expected. You'll also find that some of the engineering required to is exactly the same as you
thought you would avoid.
Dynamic alarming is a valuable technology to use. In fact, it is the only solution for many alarm management issues, such as suppressing
alarms on equipment that is intentionally shutdown. Make sure you fully understand the role, the costs, and the benefits of dynamic alarming
before interpreting it as a blanket solution for an alarm problem.
Many terms are used to promote the dynamic alarming concept: state based alarming, advanced alarming, dynamic suppression, alarm subsumption. It all boils
down to changing the alarms that confront the operator based on interpretations of plant state.
A dynamic alarm is typically triggered by alarm activity, which
results in changes to alarm settings. Because dynamic alarming requires
you to consider and design for multiple plant states for each alarm,
the engineering involved is actually more intense than that required
to design a system without a dynamic component.
In addition, an alarm system will not produce the exact alarm pattern
for every abnormality. Designing, updating, and maintaining the
trigger logic of a dynamic alarm system is similar to implementing
advanced control in that it requires some kind of model. For a dynamic
alarm system to be reliable and for it to successfully reduce risk,
it is critical that not only are the alarm settings right, but also
that they are subjected to rigorous change management procedures.
Changes to the alarm settings will not only affect what the operator
sees, but they very well can disrupt or disable the dynamic logic.
Now you should have more awareness of the the effort involved in designing and maintaining a dynamic system's trigger models, properly evaluating and engineering the alarm settings for each dynamic scenario, and the critical change control processes needed to protect those settings.
The intent is not to portray dynamic alarming as "bad", but to more accurately position it in your mind as an integral part of an alarm management strategy, not a simple solution for a troubled alarm system.
There is an alternative or interim solution known as an operator
advisory system. The main difference between an operator advisory
system and dynamic alarming is that the advisory system is non-intrusive
- it does not interface with or manipulate alarm settings on the
control system. Many dynamic alarm solutions are. They actively
manipulate the configuration in the control system, a sensitive
situation at best.
An advisory system is essentially an alternative operator interface
which they can refer to for a filtered view of alarms as well as
for supplemental advice. Being external to the control system HMI,
an advisory system can combine data and information from any plant
system and provide it to the operator in a way that will provide
guidance and assistance in the course of running the unit. An example
might be a combination of DCS alarms and maintenance or asset status
information.
Because an advisory system does not change alarm settings, it removes
the need to review or do additional configuration design work, and
it also removes the need to create and apply change control procedures.
It also removes the burden of testing and qualifying a system to
interact with the control configuration files.
An operator advisory system allows an interim step, creating a solution
for operator overload that is sensitive to engineer overload.
For more information about operator advisory systems,
see
the OASYS product by UReason.
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