Safety Distance Assessment for Vapour Cloud Explosion in the PSA Unit of Abadan Refinery: Comparison of TNT Equivalency, BST, and TNO Multi-Energy Blast Models

Vapour cloud explosion (VCE) modelling plays a critical role in defining safety distances for congested gas-processing units, yet predicted consequences remain highly sensitive to the selected blast model. This study presents a consequence-based safety distance assessment for a hydrogen PSA unit at Abadan Refinery using PHAST ۸.۴, comparing three widely applied approaches: TNT equivalency, Baker–Strehlow–Tang (BST), and TNO Multi-Energy (ME). Representative loss-of-containment scenarios were simulated to estimate flammable cloud formation (tracked at the mixture LFL of ۵.۱ vol%  ۵۱,۰۰۰ ppm) and subsequent VCE overpressure footprints. Safety distances were interpreted according to GS EP SAF ۲۵۳ fire-zone criteria, with ۲۰۰ mbar (۰.۲ bar) adopted as the governing explosion threshold. Results demonstrate pronounced model dependence. For the ۲۰ mm leak case, the ۰.۲ bar radius varied from ۱.۷۲ m (ME) to ۳.۸۴ m (BST), while TNT predictions ranged from ۰.۸۸ to ۱.۸۹ m depending on the assumed yield (۱_x۰۰۱۰_%). Divergence increased at lower overpressure levels relevant to escalation and siting decisions. The findings highlight the limitations of unqualified TNT use and support an envelope-based approach for safety distance definition, in which model assumptions are reported transparently and conservative distances are selected consistent with congestion, confinement, and applicable standards.

کلیدواژه ها:

vapour cloud explosion ، safety distance ، PHAST ۸.۴ ، PSA unit ، TNT equivalency ، BST ، TNO Multi_x۰۰۰۰_Energy ، GS EP SAF ۲۵۳