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Alarm Management / Alarm Response Analysis

Beville Engineering, Inc., has been conducting alarm response analyses in the petrochemical industry for the past 18 years. As such, we have developed a comprehensive approach and methodology that has enabled significant improvements in alarm systems for a variety of clients. The following highlight some of our results: 

• A reduction of alarms per day from 300 to 100
• A decrease in emergency priority alarms from 40 to 13 percent of the alarm total
• A reduction of alarms "in" during normal operations from an average of 15 to 0
• An 80 percent reduction in the number of emergency alarm activations

Alarm system management is universally recognized as essential to ensuring that processing plants are run safely and efficiently. Alarm system management is are 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 poorly configured alarm systems include:

Alarms that have no operator action,

• Alarm conditions that have multiple alarms,
  Alarms that are "in" during normal operations, violation of the "dark screen" principle,
• Alarm actuation rates in excess of the operator's information processing capabilities,
• Alarms with improper setpoints or deadband, causing alarm cycling,
• Excessively high alarm-to-controller ratios, and
• Alarm priority distribution that has too many emergency and high priority alarms and too few low priority alarms.

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). All of the pertinent data for each point to be alarmed is entered into a customized database form during the ARA. 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. The ARA form becomes part of the management of change for alarms. 

Several rules-of-thumb exist for determining if the alarm selection 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%

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