Gasket Sealing Characterization for Bolted Flange Joint In Cryogenic Conditions at -180°C

Abstract The industrial challenges of mastering the sealing systems of fluidic equipment involve reducing the risks of emissions during both normal operation (“fugitive emissions”) and/or accidental conditions for safety, environmental, and economic reasons, while also considering durability and energy efficiency. As part of its Sectorial Strategic Project concerning the tightness of fluidic equipment, Cetim has developed a test apparatus to characterize the performance of seals and/or metal-to-metal contact interfaces under cryogenic conditions (LN2) at −180°C with LN2 circulation. A test campaign was carried out on a selection of seals incorporating different sealing materials (graphite, PCTFE and Vespel®) as well as metal-to-metal contact interfaces. The test procedure aims to characterize the mechanical behavior, and the sealing levels based on a representative initial tightening level, but also to evaluate the ability to maintain a good sealing level during loosening. Additionally, a specific campaign was also conducted by introducing surface defects on the sealing face to assess the robustness of the tested solutions. The results show the ability of different sealing interfaces to maintain their sealing performance after mechanical cycles in nominal conditions. The introduction of surface defects shows a variability in terms of sealing performance between the different materials with one material that has the same performance in both nominal conditions and degraded conditions. The test results on metal-to-metal interfaces show the impact of the surface roughness on the sealing performance. As part of this project, a numerical study was also carried out to develop a model of a NPS4 CLASS300 valve, based on finite element analysis. The objective of this numerical study is to verify the reliability of the numerical model regarding the thermomechanical multiphysics phenomena within the valve under cryogenic conditions (LN2). The results of the tests were used to calibrate the numerical model. This presentation details the test apparatus, the test results in different configurations, as well as the developed numerical model of a NPS4 CLASS300 valve.