I have flanged and flued expansion joint that I am trying to analyze and having difficulty with the thermal analysis. The expansion joint has 6psi internal pressure and a temperature of 900 degrees F, material is 304SS. I initially applied the 6psi in a static analysis to see the stress would be, and they indeed were ~16ksi. I then wanted to add temperature, so I did a separate steady state thermal analysis at 900 degrees. I told my static analysis to rerun using the new thermal analysis results to see what the changes were. The stresses were astronomical (560ksi), so I removed the fixed constraints and told the model to "relief inertia" and "use soft springs" I also took the 6psi off of the model as well, just to see what the thermal stresses were alone. I am still seeing over 560ksi stresses. 304SS still has an allowable stress in ASME at 900 degrees F and this is a replace "like-kind" expansion join. So I know it works, I just not understanding why the thermal analysis is going wrong. Any input would be greatly appreciated.
I also tried attaching a pack and go of the file but it was too big. So I attached the assembly and parts.