Quantitative study on thermal-mechanical failure of overhead steel pipelines under natural gas jet fire

Parallel overhead pipelines are particularly adept at traversing intricate terrains. Nonetheless, the emergence of jet flames due to initial pipeline incidents can precipitate failures in adjacent pipelines, thereby intensifying the overall situation. Therefore, it is essential to examine the thermal-mechanical responses of pipelines exposed to natural gas jet fires. Building on combustion mechanisms, a transient thermal-mechanical coupling model has been developed for full-scale steel pipelines in the context of natural gas jet fires. The thermal-mechanical response characteristics of these pipelines are subsequently analyzed, and the impacts of four distinct variables on pipe wall temperature and normalized stress are quantitatively evaluated. Ultimately, a safety evaluation methodology for pipelines subjected to jet flames is proposed, which integrates critical thermal failure criteria with PSO-LSTM algorithm. The results demonstrate that the proposed thermal-mechanical coupling model effectively simulates the thermal effects of jet fires on pipelines, achieving a model error of less than 10 %. Notably, the flow velocity of crude oil has the most pronounced effect on the thermal failure of the pipeline. The established thermal-mechanical failure criterion, in conjunction with the PSO-LSTM hybrid model (average error of 5.57 %), enables the rapid prediction of critical failure conditions across a wide range of operational scenarios.