Failure probability model for LPG spherical tanks under multi-pool fire coupling

Pressurized spherical tanks in chemical industrial parks represent high-risk nodes due to their high-energy contents and susceptibility to catastrophic domino effects. However, the synergistic thermal-mechanical response of these tanks under multiple-pool fire coupling remains insufficiently characterized, posing significant challenges for quantitative risk assessment. In this paper, statistics on typical accidents and probabilistic event tree analysis were utilized to investigate potential domino accident pathways for LPG spherical tanks. The results indicate that leakage is the predominant initiating event, with fire serving as the primary catalyst for escalation, resulting in an average accident chain length of 1.18. To address the lack of failure criteria for thermal radiation coupling, an isosceles triangle layout was established to simulate the thermal response of tanks (1,000–5,000 m 3 ) under both single and coupled fire conditions. The simulations reveal that structural failure is consistently initiated at the gas-liquid interface due to localized thermal softening. While thermal radiation coupling significantly accelerates the failure sequence, larger tanks exhibit higher thermal inertia, which delays internal pressurization and extends the safety window. The failure time criteria and a failure probability model were developed. Validation results confirm a model deviation of less than 6%, demonstrating better predictive accuracy compared to traditional models and providing a robust, conservative baseline for the safety management of LPG spherical tanks.