I have a study of a non-code pressure vessel. The external pressure is 10,000 psi. Projected area in the z-axis (right to left) is about 10 in^2, so the resultant force is about 100,000 lbf. Of this, 165 lbf (0.2%) remains unbalanced after all of my boundary conditions are applied, because of limitations in the geometry I can pick on. The symmetry balances the y-axis forces, and the axisymmetric simplification accounts for the x-axis forces, which are otherwise ignored.

To handle the 165 lbf, I’ve turned on inertial relief. It’s my (weak) understanding that this is exactly what inertial relief is for, to balance slightly unbalanced loads in free floating parts by adding a body force. The knowledge base warns that inertial relief will give seemingly good results when improperly used. The results are matching hand-calcs within reason (20%).

I’m wondering specifically whether I’m using inertial relief intelligently, and generally what are the pitfalls that would leads to bogus results.