FEA of a pressure-vessel skirt-to-head junction

01 / THE CHALLENGE

Examine the junction that carries the vessel

Graphler Technology Solutions used Finite Element Analysis (FEA) to assess the connection between a pressure vessel’s bottom head and its supporting skirt. The study examined deformation and stress under empty, operating and hydrostatic-test conditions.

The junction brings together the curved pressure boundary and the cylindrical support. Internal pressure, vessel weight and lateral loads act through this region in different combinations. The engineering task was to examine those combinations and evaluate the resulting stresses at defined sections.

The assessment focused on the skirt-to-head assembly. Components outside the local model were represented through their mass contribution. A separate horizontal configuration represented the shop hydrotest condition.

02 / OUR APPROACH

Model the connection and its load cases

The three-dimensional assembly included the skirt, ring, bottom head and cladding. GTS used a solid-element model with linear-elastic material behaviour and bonded joints to examine the response under the specified loads.

Five scenarios, with distinct operating conditions

The load cases combined internal pressure, the relevant vessel weight, and wind or seismic loading. The test cases also distinguished between vertical and horizontal arrangements.

Support constraints were defined for the respective configurations. The analysis treated the material response as linear elastic and the connected weld regions as bonded.

03 / THE ASSESSMENT

Connect the stress field to the evaluation sections

The operating case with seismic loading illustrates the local stress variation around the head-to-skirt region. The equivalent-stress contour identifies areas for closer examination within the assembly.

Evaluate membrane and bending stresses

The project report used the ASME Section VIII, Division 2, Part 5 Design by Analysis methodology for its stress evaluation. Stress Classification Lines (SCLs) were placed at three locations: the skirt-to-head junction, the shell and the skirt.

Stress integration along these lines separated the membrane and bending contributions for the section checks. The report recorded local membrane and combined membrane-plus-bending results by load case, providing a structured basis for comparison with its stated stress limits.

04 / ENGINEERING VALUE

A traceable assessment of the supporting junction

The study brought together deformation results, stress contours and linearised section results for five load cases. It connected each operating or test condition to specific evaluation locations in the vessel assembly.

For the design team, this provided a documented basis for reviewing the junction, shell and skirt under the specified loading. The useful deliverable was the relationship between the geometry, load case and classified stress response.