Beville Engineering, Inc., has been conducting alarm response analyses in the petrochemical industry for over 25 years. As such, we have developed a comprehensive approach and methodology to alarm rationalization that has enabled significant improvements in alarm systems for a variety of clients. The following highlight some of our results:
Alarm system management is universally recognized as essential to ensuring that processing plants are run safely and efficiently. Alarm system management is also universally recognized as being problematic. It is ironic that a system that is so essential is often the source of so many problems. Stories of operators missing or misunderstanding alarms and wreaking havoc on a process are all too familiar. There are tell-tale signs that an alarm system is poorly configured. Characteristics of systems that would benefit from an alarm management study include
Although problems with alarm system management may be easy to identify, identifying the solutions to the problems is not so simple without a substantial amount of knowledge and experience. Conceptually, selecting alarms is not difficult: each alarm should prompt a unique operator action. If there is no action, there should be no alarm. If multiple alarms all prompt the same action, there shouldn’t be more than one alarm.
Systematic application of this principle is done through an alarm response analysis (ARA), or alarm rationalization. All of the pertinent data for each point to be alarmed is entered into a customized database form during the alarm rationalization. The data that is captured is then used to determine what points need to be alarmed, deleted or changed. This method of cataloging each point's data provides documentation for any changes that are made and works as a control for future alarm additions and rationalization. The alarm response analysis form becomes part of the management of change for alarms.
Several rules-of-thumb exist for determining if the alarm management process was successful. The total number of alarms for a system should be a 2.5:1 ratio of alarms to controllers. For example, a unit with 200 controllers should have about 500 alarms. These alarms should have a priority distribution of the following:
Level 1 - 10%
Level 2 - 35%
Level 3 - 55%
RELATED EXTERNAL MEDIA
|Consortium Reports New Findings on Alarm Rates||Automation World|
|How Many Alarms Can An Operator Handle||Chemical Processing|
|Impact of Alarm Rates and Interface Design on Operator Performance||Automation World|
|Operator Interfaces: Moving from Comfortable to Most Effective||Automation World|
|Operator Performance as a Function of Alarm Rate and Interface Design||Mesa.org|
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