The Role of Interdependent Contexts in Accident Progression

Understanding the level of independence of risk controls in a system is essential when conducting risk assessments (RAs). RAs are often influenced by multiple external and internal contexts. On 25th May 2021, a catastrophic failure occurred at Callide C power station in Queensland. The technical and organizationally focused investigation reports, indicated that the failure resulted from a top-down flow from decisions made at the stakeholder level, including altered operational strategies, asset management practices, and cost cutting. These decisions affected the corporate and organizational levels, ultimately impacting how risk management was conducted, how risk assessments were performed, and how risk data was collected, stored and monitored. Needing to explicitly consider the multiple stakeholder, organizational, and informational contexts highlights the challenge of recognizing and integrating system interdependencies in risk management decision-making. We applied a network analysis and graph theory-based approach to the Callide Unit C4 accident reports, to 1) visualize the accident by segmenting the reports into different events and linking them together to form a directed graph; 2) perform a constrained robustness analysis on this network to identify system vulnerabilities; 3) illustrate the cyclical relationships between system components. Key findings reveal that the board did not have the reach, influence or visibility of downstream process safety or management of change-related events. Furthermore, the technical contexts significantly contributed to the accident, highlighting potential hazards associated with the redundancy design. In this study, we have demonstrated the use of network analyses to better understand how context behaves as an influencing factor affecting interdependence among the components and their controls, and ultimately benefits the hazardous industries.

Keywords: Risk management, Network analysis, Graph theory, Context.