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Static seals for hydrogen at high pressure


Seals for gaseous hydrogen at high pressure and low temperatures are still a challenge for finite element analysis. In our paper we show the preparation and execution of an FEA analysis of a hydrogen seal, which was designed as a static O-ring seal. The aim was to perform a verification of the reliability of a seal already in service in the temperature range from -40°C to + 85°C and in the pressure range up to a system pressure of 1000 bar by means of a simulation. As a basis for a suitable material model, material investigations were carried out (uniaxial tensile stress-strain measurements as well as DMA measurements). Based on these measurement data, a uniaxial dynamic material model was created using a master curve at a representative temperature for the glass transition. A shift function was used to shift the Prony parameters to the desired temperature. The dynamic part of the material model is coupled with a hyperelastic material model under the special boundary conditions of the implemented viscoelastic material model of ANSYS with Prony parameters (R2019 R3). In the presented material model, the pressure dependent displacement from the glass transition is also considered. An implementation in ANSYS is considered (not realized, yet). The pressure of the medium (hydrogen system pressure) is imposed via a macro for fluid pressure penetration of the seal, so that the real conditions are represented.

The results of the finite element analyses (FEA) are presented and discussed for different stresses for pressure and temperature. Here, the experimental results for leakage from the hydrogen test field are also included. In the simulation, for a given gap dimension, the gap extrusion in the installed condition is investigated and the stress state of the surrounding component presented. After installation of the seal, the relaxation behavior is also shown. The contact pressure is used and evaluated to assess the tightness.

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