Hi i have problems simulating this cylindrical vessel, am having a non positive jacobian error and i could not find the solution to my problem in the forum
Am using the axisymmetric for this simulation, sorry if the solution is obvious 
In axisymmetric models, all faces must lie to the right of the Y axis. That’s most likely why the left part of your geometry has this error.
If you want to simulate a complete vessel, rotate it so that Y axis is the axis of symmetry - that’s what CalculiX expects.
Also, you should refine the mesh significantly.
Thanks so muchhhhh i will try!!