Implementing alarm management per the ANSI/ISA-18.2 standard
Summarizing the standard’s 10 stages into four general tasks can simplify implementation and speed up the schedule.
In process industries, alarm systems are used to notify operators and other plant personnel of abnormal process conditions or equipment malfunctions. Alarm systems help operators operate the process safely under both normal and abnormal conditions, and the alarm system needs to be designed correctly to provide the best opportunity for safe and efficient operation.
Before the wide adoption of distributed control systems (DCSs) and other PC-based human machine interfaces (HMIs), visual and audible indications of process plant operations were normally provided by a panel board, with the number of alarms restricted because of space limitations. In addition, alarm points had to be selected with care, because these points were hardwired and expensive to change.
But with a modern automation system, the number of alarms is virtually unlimited, as additions and changes are made simply by reconfiguring software. This ease-of-use provides the opportunity to improve alarm systems, but can also make alarm management more challenging.
In particular, there is a temptation to alarm every possible deviation, even when the deviation doesn’t present a problem requiring immediate attention. In the event of a serious incident, this practice can generate a huge number of alarms simultaneously, commonly referred to as alarm flooding. When this occurs, operators may not be able to ascertain and act on the important alarm(s), causing the incident to escalate in terms of severity.
In the worst case, alarm flooding can cause serious environmental damage, production loss, injury, or even death to plant personnel. Proper management of alarm systems is essential to deal with alarm flooding and other related issues.
Poor alarm management can lead to serious consequences in process plants, as noted in the book “Alarm Management for Process Control” by Douglas H. Rothenberg, and by others in various documents and publications.
For example, poor alarm management caused one incident that resulted in $80 million damage and injured 26 people. Another process plant incident resulted in 15 deaths, 170 injuries, and significant economic losses. To avoid these types of incidents, proper alarm management is essential.
To improve alarm management, the International Society for Automation (ISA) issued standard ANSI/ISA-18.2-2009, “Management of Alarm Systems for Process Industries.” When issuing this standard, ISA considered other existing documents including the Engineering Equipment and Materials Users’ Association (EEMUA) standard 191 “Alarm Systems: A Guide to Design, Management and Procurement.” The International Electrotechnical Commission (IEC) is using ISA-18.2 as the basis for international alarm management standard IEC-62682.
This article gives an overview of ISA18.2, and shows how it can be used to improve new and existing alarm systems in process plants.
Role of alarms
ISA-18.2 defines an alarm as “An audible and/or visible means of indicating to the operator an equipment malfunction, process deviation, or abnormal condition requiring a response.” This means an alarm is more than a message or an event, as it indicates a condition demanding quick operator action.
Ideally, each alarm will provide the operator with related information such as priority, possible root cause, and a recommend response procedure. The operator can then respond to the alarm quickly and effectively. Limiting alarms, prioritizing alarms, and providing alarms with necessary related information can reduce the chance that an operator will delay response to an alarm, or even ignore the alarm.
What is alarm management?
Alarm management is the proper implementation of documentation, design, usage, and maintenance procedures to construct an effective alarm system. ISA18.2 defines the processes and procedures required to create an effective alarm management system. Figure 1 shows the ISA18.2 lifecycle model of alarm management. This model can be applied to a new or an existing alarm system.
As shown in Figure 2, stage activities logically follow one another, and correct completion of all activities will result in a properly designed and effectively operating alarm management system. The lifecycle model also includes stages for ongoing maintenance of the system, essential for sustaining effective operation.
The 10 stages in the lifecycle model can be roughly categorized into four general tasks. To perform these tasks, it’s essential that a process plant create a cross-functional team that includes all relevant plant functional areas including, but not limited to, management, engineering, safety, operations, and maintenance.