Increase Hazard Discovery and Minimize Errors in your Process Hazard Analyses A Graph Theoretical Approach

摘要

Process Hazard Analysis (PHA) methods and techniques are constantly being developed. Yet, PHAs often fail to recognize discoverable, credible hazard scenarios. Unrecognized hazards were implicated in the BP Texas City disaster, Formosa Plastics explosion, Chevron Richmond Refinery fire and other high profile incidents. Unrecognized scenarios represent a gap in understanding of process hazards and keep us from preventing accidents and disasters. This paper focuses on improving the completeness of the hazard identification. The PHA process is visualized by mapping it in the form of graphs. Ammonia tank hazard and operability study (HAZOP) and Failure Modes and Effects Analysis (FMEA) examples are mapped as graphs to reveal tree structures. These tree graphs or inference maps directly allow us to visualize causal connections and inferences. Chains of cause and effect are mapped as unique pathways that can be represented as both graphs and matrices. For example, one can graphically trace the pathways to hazardous events such as loss of containment. This paper investigates the role of errors, omissions and constraints in reducing the discovery of process hazards. What are the sources of errors and omissions (E/O)? What are the effects of constraints like budget and time? How can PHAs be audited efficiently to identify and correct E/O? A fault tree analysis (FTA) of the generic HAZOP process is performed to trace the sources of the E/O and how they may be minimized. The FTA identifies seventeen distinct sources of E/O. The sources of E/O are mapped to the issues they affect and a quality assurance checklist is derived from the FTA of the HAZOP process. CSB case studies are cited showing the impact of the E/O on hazard discovery in real incidents.