comparison of risk assessment using hazop and etba techniques: case study of a gasoline refinery unit in iran

background and objective: prevention of accidents—a crucial requirement in oil industries—involves hazard recognition, risk assessment, and corrective actions. the purpose of this study was to compare the etba and hazop techniques for risk assessment in a gasoline refinery unit. methods: in this case study, data were collected using process flow diagram, walking–talking through method, piping and instrumentation diagram, and direct observations. worksheets for both techniques were filled on the basis of the risk assessment matrix mil-std-882e. results: the hazop method identified 44 deviations attributable to 118 causes. in addition, 11.37% of the identified hazards were associated with unacceptable risk, and 36.36%, with unfavorable risk. the etba method detected 10 groups of energy (24 subgroups) 33 hazards were detected, 10.62% of which were associated with unacceptable risk. conclusions: hazop proved to be the more powerful technique for the prediction and identification of hazards. however, etba detected certain hazards that were not identifiable using hazop. therefore, a combination of these two methods is desirable for the assessment of hazard risk in process industries.