Numerical Assessment of Thermostructural Instability of Cylindrical Tanks Subjected to Pool Fire

The risk of thermostructural instability of thin-walled tanks in petrochemical storage farms due to adjacent fires is an engineering design concern. Thermal buckling of thin-walled tanks could potentially result in disastrous consequences such as large premature deformation and probable cracking of the shell, leading to flammable liquid leakage or spilling and additional pool fire spreading. Various parameters, such as the pool fire’s diameter, stand-off distance, and exposure to multiple surrounding pool fires, are among the factors that can produce different thermal loads on the target structure that empirical or simplified analytical models often fail to accurately predict. Examining these parameters illuminates their influence on thermal loading on cylindrical tanks and their mechanical behavior. In this study, a combined thermostructural approach is exploited in the form of large eddy simulation (LES) to investigate the pool fire geometrical parameters and nonlinear structural thermal instability analysis of thin-walled tanks with fixed roofs. The results reveal that by increasing the fire stand-off distance, the flux received by the target tank reduces at a rate slightly less than the inverse of distance squared, and the risk of a structure’s instability is tangibly postponed. Analyzing pool fire diameter shows that there is a maximum critical temperature for the empty tanks. Also, it is found that the risk of tanks’ thermostructural instability is a function of multiple pool fires arrangement and their geometry, and there is no simple relationship between the number of pool fires and critical destabilizing temperature.

Fire is one of the major risks that threaten the performance of thin-walled structures such as petrochemical storage in tank farms. Fire would induce heat flux by radiation and convection methods on the tank surfaces and, by irregular temperature distribution, the shell could deform in an unstable critical manner. This study covers the effect of pool fire dimension and its stand-off distance on the structural behavior of thin-walled tanks. The pool fire and the tank are simulated by sophisticated numerical methods. The buckling mode shapes and critical temperatures at which the shell experiences severe and sudden deformation are investigated. Moreover, the effect of fire incidents with multiple pools on storage tanks has been scrutinized. The results would be beneficial for the tank’s design, risk, and uncertainty assessment and also would guide the determination of the optimal position of reservoirs in tank farms.