Eigenbuckling Mode Shape 5
FEA Model Results of Buckled Vessel

Both Instantaneous (Linear and Non-Linear) Buckling were Investigated

We performed a buckling analysis on an elevated temperature stainless steel vessel subjected to a vacuum loading. The vessel was constructed of 304H stainless steel and subjected primarily to vacuum loading at elevated temperatures for the making of styrene. Its dimensions were 5650 mm (222.4 inch) inside diameter with shell coarse thicknesses of 40 mm (1.57 inches) and 64 mm (2.52 inches), and an overall height of 29.722 meters (approximately 97.5 feet). The vessel was to conform to out-of-roundness limits to both client specs and the ASME Code.

Both instantaneous (linear and non-linear) buckling and long term creep buckling were investigated. The analysis was performed using ANSYS finite element software, using linear shell elements (Shell 181) with creep capability.

Creep buckling analyses were completed using incremental analyses in conjunction with isochronous stress-strain data. Time-based creep analyses were also performed. The vessel was also evaluated for buckling using the method described in ASME Code Case N-284-1.

Nonlinear, instantaneous buckling analyses were completed based on the hot tensile stress-strain curve for 304H SS at 1200°F. The analysis was performed for three different loading conditions: vacuum load only, and vacuum load with 2 nozzle load cases. Results of analyses conducted using the Eigenbuckled mode shapes scaled to have 1% and 2% out-of-roundness for the initial vessel geometry.


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Tom O’Donnell, PE
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