Anatomy of a Catastrophic Incident

An important aspect of understanding the management of abnormal situations is the interrelationships among root causes and interventions by plant systems and plant personnel. Specifically, the figure below illustrates the anatomy of a catastrophic incident.

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(This diagram is based on original concepts created by Ken Emigholz of ExxonMobil, Ian Nimmo of UCDS LLC, and Jamie Errington of NOVA Chemicals.)

The figure depicts the evolution of an abnormal situation from some initial cause producing an operations upset to a catastrophic disaster involving serious destruction and harm to the plant and/or the surrounding community. In the center of the figure, the abnormal event sequence illustrates the progression of an abnormal situation and the interaction with failures and hidden problem conditions in three plant systems. These three independent systems, the process system, the protective applications & shutdown system and the safety containment system are designed to safeguard the plant from catastrophic events. Moreover, the event sequence illustrates the role of plant personnel in intervening to prevent a process upset from escalating to a plant shutdown. In the event of a loss of control situation, the plant personnel must intervene to minimize the impact of a catastrophic incident on the plant and surrounding community.

The operations activities are performed by typical operations crews comprising console operators, lead operators, supervisors and field operators. This would also include coordination among operations crews responsible for different areas within the plant. The technical support activities are performed by typical technical support staff comprising engineers and technicians in the areas of process, instrumentation, mechanical, safety, application development and DCS systems. Although, the role of the individuals varies from situation to situation, the degree to which the technical support staff gets involved depends on the speed at which the problem evolves. Unfortunately, the console operator is usually the only one available to respond because of the speed at which most abnormal situations evolve. The ability to support the console operator in a real-time fashion depends on integration and timely communication through the information and communication systems.

As illustrated in the anatomy of a disaster diagram, there are a number of factors that can contribute to the onset and escalation of an abnormal situation. A key component of managing abnormal situations in initial stages is the intervention activities of the operations team. If time permits, the technical support team can contribute to the intervention activity helping to prevent the continuation or escalation of the situation. In some cases, the technical support team has time because the problem is a slow degradation or the operations team stabilizes the process at some sub-optimal state.