Abstract
Gas stations are vital components in gas gathering and transportation systems. Flanges establish a crucial connection between pipelines, as well as between pipelines and gas station equipment. They primarily rely on the pre-tightening force generated by the bolts to achieve metal sealing. The pre-tightening force is transmitted to the gasket to generate sufficient sealing pressure and avoid fluid medium leaks. The main cause of leakage is a contact gap between the flange and the gasket, which can result in the sealing failure of the flange connection system. The sealing performance of the flange system determines the airtightness of the pipeline system. This paper combined theoretical analysis and simulation to examine the sealing performance of flange system connections in gas stations. Different tightening forces and preloading force sequences were used to numerically analyze the sealing performance of the individual flange components. The compression-rebound characteristics of the flange gaskets and the bolt preload sequences were analyzed, yielding the following results: (1) At different pre-tightening forces, the overall flange stress was uniformly distributed, while the bolt stress was concentrated at the inner side of the stud and the contact position between the bolt and the flange. The stress distribution on the gasket was uniform, with a higher outer than inner stress. (2) The compression rebound curve indicated a certain nonlinearity in the flange gasket at different preloads. Furthermore, the preload caused a flexible graphite metal gasket wound. The degree of elastic or plastic deformation in the gasket increased at a higher preload. Although a higher preload increased the sealing capacity in an appropriate range, excessive preloading induced plastic gasket deformation, causing it to lose its original compression resilience and resulting in seal failure. (3) The flange interaction varied at different loading sequences, while different pre-tightening sequences produced elastic interaction. Therefore, the bolts that were tightened first more significantly affected pre-tightening than those tightened later. Changes were evident in the stress distribution of the gasket, which showed improved sealing performance under sequential and cross-loading.
