Managing alarms effectively
Alarm worksheets set a good foundation
Alarm worksheets, also known as configuration sheets or pages, are used to configure the setpoints and limits for the tag names, such as a HiLimit of 110 degrees for the “Temperature” tag with a nominal setpoint of 100 degrees. By spending time to set the alarm limits and deviations correctly, fewer nuisance alarms will be generated.
The alarm worksheets also contain message sections that correlate to the alarm, the priority, and the selection field—all to provide the operator with more information on the alarm. For example, for a HiLimit temperature alarm, within the worksheet users can set a message (Too Hot), a priority (0-255), and a “selection” that is a user-defined field such as “Tank2.”
All the items in the alarm worksheets can be set as well as changed. Later on, we’ll see how by including values in the messages, the worksheets enable easy filtering.
The information on the alarm worksheets should appear on the screen as an alarm object. Once imported into the SCADA system, the worksheets should provide functionality to automatically e-mail alarm messages. Furthermore, the SCADA system should provide settings to control exactly when and how these alarm messages are sent. Some common settings are frequency, number of alarms, message format, response times, and escalation procedures.
Typically, the SCADA system default setting shows all active alarms, but these settings can be changed to only show certain alarms. The ability to have the “online alarm object” as the default setting, meaning it doesn’t need to pull information from a database, is vital. This is important when operators only need to view current alarms as opposed to all active alarms over a longer time period
The SCADA system should also provide functionality to allow alarm data to be pulled from a database to get a view over a selected period of time, as this is often useful for troubleshooting by maintenance personnel and others. Characteristically, this functionality permits viewing of all alarms that have been logged. With many SCADA systems, alarms can be logged using a built-in PDF writer that turns alarms into a PDF document. This document can then be saved, e-mailed as an attachment, or printed as a report.
Using filters to manage alarms
Filters are one of the most important features for preventing alarm overload and insufficient prioritization of alarms. Most modern SCADA systems provide easy configuration of features that offer a wide variety of sorting and filtering mechanisms.
One of the biggest alarm management issues is that operators are inundated with low-priority alarms and therefore miss critical high-priority alarms through alarm fatigue and the inability to quickly distinguish an alarm’s urgency. This is where a SCADA system with superior filtering mechanisms becomes highly valuable.
The first step in filtering was discussed in the worksheet section in which information can be prioritized to have only certain alarm limits appear. For example, the screen might display only Priority 10 and above alarms, or only the HiHiLimit alarms.
In addition to setting alarm priorities, plant personnel should consider SCADA systems that offer a filter dialog that includes an expression to let users customize the filter. For example, only HiHiLimit alarms that have the word “Hot” in the message are displayed on the screen in response to certain conditions. This expression can be hard coded, but to increase effectiveness it’s often better to create a string tag that changes values during runtime depending on specific operating conditions.
When an incident occurs, hundreds of related alarm messages can be quickly generated. Usually, only one alarm is the root cause, and the rest are symptoms of the problem. This is where many SCADA systems fail because the operators have no way to distinguish the root cause from the symptoms. But, the ability to build strings based on key criteria can help operators locate the root cause of the problem quickly.
For example, temperature alarms may start appearing with messages saying, “Tank 1 temperature too high” or “Pipe 1 pressure too low.” Operators must now quickly determine the root cause of why the temperature in Tank 1 is too high. The ability to filter all messages with a single word such as “hot,” or with a phrase like “valve closed,” can help them discover why the tank temperature is soaring. Wild card expressions can also be used to sort through words or individual phrases in the messages.
Unfortunately, many operators and even some plant managers have found managing alarms so burdensome they have almost considered them nuisances. This attitude can lead to important alarms being missed or ignored, a dangerous situation. It doesn’t have to be this way, as alarms are a key part in monitoring plant operations and can be managed effectively using off-the-shelf software tools.
One of the keys to effective alarm management is selecting the right SCADA system, one that offers advanced and easily configurable alarm management features. These features should include alarm prioritization to alert operators of conditions that require quick responses. Filtering features are also needed to enable operators to quickly locate root causes.
Implementing these and other features of modern SCADA systems as part of an effective alarm management program will improve response to alarms. This will minimize downtime, increase safety, and keep minor alarms from escalating into major incidents.
Fabio Terezinho is vice president of consulting services and product manager for InduSoft. www.InduSoft.com.