Failure analysis of the conical gaskets in ultra-high pressure pipeline sealing devices: Experiment and numerical simulation

This study was focused on the conical gaskets in ultra-high pressure pipeline sealing devices. Failure analysis of the conical gaskets was carried out by combining gasket experiments and numerical simulations. Macroscopic dimension inspection, miniature specimen tensile tests, micro-hardness tests, metallographic tests, and scanning electron microscope (SEM) experiments were carried out to study the differences between used gaskets and unused gaskets. Results show that the mechanical properties of the used gaskets degenerate and microstructural changes occur, which is caused by frequent pressure fluctuations in the working environment of high temperature and high pressure. Besides, the stress distribution and deformation of the gasket, as well as the effect of pressure fluctuation on the gasket stress, were analyzed by numerical simulation. Meanwhile, an improved layer-variable parameter numerical model is proposed for the numerical simulation of the used conical gaskets. The model was used to compare the elastic resilience of the gaskets before and after service under different preload, respectively. Results show that the simulated results by the model is closer to the experimental results. The elastic resilience of the used gaskets is significantly less than that of the unused gaskets. Therefore, it can be concluded that the mechanical properties degradation and accumulation of plastic deformation of the gaskets caused the lack of the elastic resilience of the gasket, which may be the direct cause of the seal failure.