This study operationalizes the Overton Window concept into a quantitative framework for analyzing catastrophic industrial safety failures. Through a comparative case study of the Beirut port explosion (August 4, 2020) and the Shahid Rajaee port explosion (April 26, 2024), we demonstrate how the normalization of hazardous material storage practices shifts the boundaries of politically and socially acceptable risk. A novel Overton Window Index (OWI) is proposed to measure the temporal drift of risk acceptance in port governance systems. The analysis reveals that both disasters followed a five-stage trajectory: unthinkable risk, radical negligence, acceptable deviance, sensible inaction, and catastrophic normalization. The findings suggest that policy failure in hazardous material governance is not merely technical but deeply embedded in socio-political structures that progressively expand the window of tolerated risk until catastrophic failure becomes inevitable.