Objective The aim is to address the insulation layer failure of large liquefied natural gas (LNG) storage tanks due to temperature changes and the settlement of expanded perlite during long-term operation, this study investigates the comprehensive impact on the cryogenic performance and structural safety.

Method By comparing theoretical derivation and numerical simulation, the density distribution changes laws of the perlite insulation layer during the settlement process and its influence mechanism on cold leakage were analyzed. Based on the ABAQUS finite element software, a thermal-mechanical coupling model of the storage tank considering the settlement effect was established, and a sensitivity analysis was conducted to quantify the impact of settlement on the temperature field distribution.

Result Firstly, the settlement of perlite led to an increase in density in the bottom area, forming a local thermal bridge effect. Secondly, the expansion of the upper voids caused by settlement enlarged the distribution range of low-temperature thermal stress, and the maximum thermal stress in the bottom concrete layer of the storage tank increased. Thirdly, the accumulation of boil-off gas (BOG) in the annular space intensified the local temperature change rate, which might induce the risk of concrete cracking.

Conclusion The perlite settlement is the core factor leading to the degradation of the cryogenic performance and structural safety risks of LNG storage tanks. Optimizing the perlite filling process and adding gas diversion devices can improve the impact of BOG; the research results provide theoretical basis and engineering guidance for the design optimization and full life cycle maintenance of ultra-large capacity LNG storage tanks.