All process industries can benefit from a well-managed alarm system in a variety of ways. The key, however, is to ensure that these systems are correctly configured to keep your plant operating at peak performance. This article will discuss alarm systems, their importance, industry standards, and a guideline for the optimal number of alarms needed to be effective. Then you’ll know whether or not your alarms are working to their full potential.
What Is an Alarm System, and Why Do I Need One?
Alarm systems notify operators and managers about abnormal conditions that require a timely response that occur during a manufacturing process. It warns users to take the appropriate action at the appropriate time, in order to avoid an undesirable outcome.
The following are the top advantages that an effective alarm system can provide manufacturers:
- increase plant safety
- improve productivity
- reduce unplanned downtime
- ensure compliance with best practices and regulatory requirements
ISA 18.2: The Standard for Process Industry Alarm Systems
To improve alarm management, the International Society for Automation (ISA) issued standard ANSI/ISA-18.2, “Management of Alarm Systems for the Process Industries.” It establishes a framework for the successful design, implementation, operation, and management of process industry alarm systems.
The Purpose of an Alarm System
The core purpose of any alarm is to drive timely operator reaction to an abnormal process event with a cost of inaction.
The ANSI/ISA 18.2 defines alarm as “an audible and/or visual indication to the operator that an equipment malfunction, process deviation or other abnormal condition requires a response.”
A well-architected alarm system aims to have the optimal number of alarms to keep the process within operation range in a safe manner. By implementing the ISA-18.2 standard, plant managers can develop an alarm system with these alarm management goals:
- Alarms must be presented at a rate at which operators can respond.
- All alarms that are configured must have a consequence if an operator does not respond.
- A process is developed to ensure alarms are properly defined and prioritized.
- The alarm system clearly indicates when it is not functioning.
Optimal Number of Alarms
The ISA-18.2 standard defines a set of Key Performance Indicators (KPIs) that plant managers can use to guide their alarm system design philosophy:
|Accumulated Alarms per Day per Operating Position
|Stale alarms per day (alarms that remain active for extended periods)
|Less than 5 present on any day, with action plans to address
|Percent contribution of top 10 most frequent alarms to overall alarm load
|1% to 5%
The goals of the above KPIs are to provide a benchmark with which to optimize the alarm system to drive operator attention to the right corrective action for the abnormal process.
Unoptimized Alarm Systems
Unoptimized alarm systems can overwhelm operators with numerous chattering alarms.
- A stale alarm is one that has been in the alarm state for a long time. They can distract the operator by clogging the alarm summary screen and can cause the operator to ignore critical or persistent issues.
- A nuisance alarm is one that annunciates excessively or does not return to a normal state after the correct response has been taken. Nuisance alarms can confuse operators, cause alarms to be ignored, and result in an abnormal condition not being detected.
Determine the Validity of the Alarms
To help eliminate inefficient alarms, the ISA-18.2 standard provides some questions that managers and engineers can ask to rationalize each alarm:
- Does the alarm indicate a deviation or processing function that requires operator action?
- What is the importance of the condition?
- What are the consequences of no operator action?
- Does the alarm provide time for the operator to act effectively and in a timely manner to avoid consequences?
- Is the alarm unique, and does it capture the root cause of the malfunction or abnormality?
Each alarm must be justified and reviewed. In addition, alarms should be prioritized based on the intersection of cost of inaction and time to operator response.
The time to operator response needs to be sufficiently long, so the operator can react efficiently to avoid the cost of inaction.
This cost of inaction can cover many internalized or externalized costs, including plant safety, loss of production or product, and environmental concerns. The ISA-18.2 standard recommends no more than three alarm priority levels.
Using ISA-18.2 to Maintain an Effective Alarm Protocol in Manufacturing
The ISA-18.2 standard provides plant managers and process engineers with a foundation to architect an alarm system with an optimal number of alerts by providing benchmark KPI’s, an alarm rationalization framework, and prioritization guidelines. Utilizing this standard can increase operational efficiency by reducing nuisance alarms, stale alarms, and alarm flooding, enabling operators to react to process critical events free from distractions, and using alarms to their full potential.