Alarm systems are essential to manage modern industrial plants. Their operation is fundamental for the production, informing operators and supervisors on possible risks.
Alarm management is one of the hottest open discussions in plants automation and maintenance. This is given to some key factors such as risk reduction, people and environment safety, the need to improve alarm systems already present in the plant.
In the past, it was quite uncommon that the operator had to manage more than one hundred alarms. Usually those alarms were configurable via hardware as with light signals which were expensive and not adaptable.
With modern automation, alarm system functionalities are achieved through interfaces that are suitable, smaller in dimension, less expensive and that make use of standard and open software components.
Today, the increased number of alarms and warnings, caused by the increased number of connectivity and available data, has a negative impact on working stress. For this reason, companies and associations have faced the problem focusing on analysis and optimization of alarm systems. The most interesting goals reached are the standards AIS/ISA 18.2 and Eemua-191.
These standards define what an alarm is, emphasizing the response to malfunctions and feedback model. Moreover, they also develop the concept of “Alarm Management Lifecycle” that defines the methodology to classify and realize alarm messages to analyze risks and principles to be adopted in the engineering of control systems.
To be noticed that even international standards, ISA 18.2 and IEC 62682, for alarm system management in process industries, are aligned with Eemua-191. Norms included in EN 50131 should also be taken into consideration, since they describe performances for Intrusion & Hold-Up Alarm Systems (I&HAS) indicating the safety level of the system and of its components.
The 9 steps of Alarm Management
Alarm Management is necessary in a production environment, controlled by operators using a system for control, maintenance and supervision, with hundreds or thousands of single alarms. At the same time, it is crucial to ensure that all the alarms are shown to operators in a suitable time. Alarms should also be able to provide the operator with the necessary means for intervention basing on priority. To guarantee production continuity, safety and quality 24/7, that is able to react to all the alarms, alerts and anomalies, an organization with a precise strategy must be in place. The following nine steps summarize it.
Step 1: Guide Lines
It is important realize a document comprehensives of design phase which includes guidelines, defines standards of the plant and the management methodologies of the alarms based on best practice
Step 2: Comparative evaluation
It is important to analyze the alarm system in order to define its strengths and weaknesses, as well as to find a practical solution to improve performances
Step 3: Documentation and alarm classification
A revision of documents and of the entire alarm database is useful to guarantee that each alarm conforms to the philosophy and principles of a good alarm management.
Step 4: Alarm system performance definition
The so called “Alarm System Performance” should be defined with easily accessible metrics, through spreadsheets or structured data bases. Examples of such metrics are the “number of alarms per operator”, alarm frequency, how many hours the alarms were triggered more than a certain amount of times.
Step 5: Control system design
It is important to design control systems that are capable of configuring several alarms without losing performances and flexibility, as much as to have the possibility of adding and configuring alarms easily and rapidly.
Step 6: KPI
The alarm system should operate in accordance with KPIs and concepts of ergonomics and Human Factors Engineering. Software tools with specific characteristics and functions are needed to ensure that performances of the entire system are in accordance with the desired final results.
Step 7: Safety design
When possible, the alarm system must be designed in accordance with IEC 61508 and the required availability specifications. The alarm system should be independent from the control system and from other secondary alarm systems.
Step 8: Defining priorities
Priorities need to be assigned in order to guarantee that the most critical alarms receive the needed attention by the operator, as soon as possible. Alarms must be presented to the operator in a clear way, depending on their priority and should be distinguished from other alarms, remaining ON and visible as long as the alarm is active.
Step 9. Information for operators
Alarm configuration must allow operators to take correct evaluations and to take action in a reasonable amount of time. Each alarm should provide the operator enough information on alarm conditions, areas involved, requested actions, priorities, when the alarm was triggered and its status.
