Understanding operator decision-making is a good first step in improving operator effectiveness. Operator decision-making depends on the person (their level of expertise) and the situation (how familiar). A popular behavioral model from Rasmussen proposes that operator response can be broken into three levels; skill-based behavior, rule-based behavior, and knowledge-based behavior as shown in…
Successful alarm rationalization combines both art and science. From the scientific point of view, rationalization follows a systematic process that applies alarm management principles to determine whether an alarm is justified (needed) and to document its basis (cause, consequence, corrective action, time to respond) and settings (priority, setpoint) in…
The increasing global adoption of alarm management standards (ISA-18.2 and IEC 62682) is bringing the importance of alarm rationalization to the forefront. Rationalization is defined as the “process to review potential alarms using the principles of the alarm philosophy, to select alarms for design, and to document the rationale…
The March / April 2020 issue of Intech contains an excellent article by Nick Sands and Donald Dunn, the co-chairs for the ISA-18 committee.
The article reviews some of the most frequently asked questions on alarm management:
As many of you will know, one of the most common form of nuisance to operators working industrial controls are repeating or chattering alarms. On a typical plant, repeating alarms may account for around 50% of the alarm annunciations. They are a problem because the operator will have to…
One of the more important tasks in the alarm management lifecycle is auditing of the alarm system configuration. Auditing preserves your investment in rationalization, checks for changes that bypassed the MOC process, and helps you to maintain the integrity of the alarm system. Oh, and it also required per…
On July 27, the US Chemical Safety Board (CSB) issued a Factual Update on their investigation into a release of water containing a toxic gas (hydrogen sulfide) and subsequent fatal injuries sustained at the Aghorn Operating Waterflood Station. While it is typically not a good idea to comment on investigations…
Get your priorities (distribution) straight
A very common question is posed during alarm management training. Does the recommended alarm priority distribution of ~5% / ~15% / ~80% for high / medium / low priority alarms apply to the rationalized alarm priority distribution (as configured in the control system) or to the annunciatedalarm priority distribution…
As discussed in Part I, bow tie diagrams provide an easy-to-understand visual representation of risk management information (hazards, potential consequences, barriers, degradation factors and controls). In this article we examine the applicability of bow ties to alarm management.
According to the CCPS book “Bow Ties in Risk Management”,…
Creating an alarm philosophy document is often the entry point into the ISA-18.2/IEC 62682 alarm management lifecycle. Many tasked with developing one are discouraged by its length and the barriers it creates. When it comes to using the philosophy document, a common concern is that if the…
From an operations point of view, one of the significant parts of the ISA-18.2 and IEC 62682 alarm management standards is the endorsement of alarm response procedures. An alarm response procedure, otherwise known as “Alarm Help” or “Alarm Response Manual”, is defined as guidance for response to an alarm (e.g., operator…
US Chemical Safety Board cites lack of Alarm Philosophy, Alarm Rationalization, and State-Based Alarming as Contributing Factors to Blowout in Oklahoma
On January 22, 2018, a blowout and rig fire at the Pryor Trust gas well killed five workers, who were inside the…
Alarm floods are periods of alarm activity during which the alarm rate is greater than the operator can effectively manage (e.g., when the operator receives ≥10 alarms in 10 minutes). During a flood situation awareness is compromised and alarms are likely to be missed. In the eleven minutes prior to the explosion…
Situation: There are three operator consoles (positions) in the same control room. There is one general alarm horn that goes off whenever a new alarm comes in from any one of the three consoles. The horn draws the attention of each of the three operators.
Question: How are the…
The ISA-18.2 and IEC 62682 standards define an alarm as an “audible and/or visible means of indicating to the operator an equipment malfunction, process deviation, or abnormal condition requiring a timely response”. One of the reasons why alarm systems are out of control (alarm overload, nuisance alarms)…