A: head (cylindrical part) bottom.

Axis X: transverse axis in head plane;

Axis Y: transverse axis in head plane;

angle θ of nozzle insertion is taken from this axis toward axis X;

Axis Z: normal axis to head plane.

All axis can be horizontal and vertical according to the shell options:

Additionally, can flip the element relative to its plane to simulate the head of the pressure vessel.

Point A.

All calculations by the finite element method (FEM) fix bottom end of head.

If cylindrical part is set then its bottom part is fixed.

Inner overpressure.

Outer pressure.

Hydrostatic pressure.

Different temperatures for the head and its cylindrical part.

Thermal strains.