INTRODUCTION

Most of the process equipment is subjected to compressive loadings during their operation (e.g. Pressure vessel/ heat exchanger sub. to full vacuum). Sometimes this type of loading results in buckling of the component causing buckle failure of the structure. Hence process equipment needs to be evaluated for any possible buckling failure. This type of failure is mainly observed in long vessels, vessels with a larger diameter, vessels with improperly spaced stiffeners.

Process equipment manufacturer from India & Abroad approached ANALYZER to seek assistance in evaluating the design of their newly developed equipment against buckling failure using simulation techniques & provide the solution in case of any observed failure.

FEA WORKFLOW

• Determining the material properties for different MoCs of equipment, design parameters to be considered in FEA.
• Preparing FEA Model for elastic buckling analysis. Here the element type is of utmost importance as very few elements gives reliable results of bifurcation analysis.
• Solving the FEA model for unit loading in ANSYS APDL Solver. The model is solved for bifurcation analysis (Eigen value Buckling) which extracting different mode shapes of buckling failure along with frequencies of buckling failure.
• Performing the design factor calculations & it should be higher than the minimum design factor as defined for different type of constructions in clause 5.4 of ASME Sec. VIII Div. 2.

CHALLENGES

• Deciding the element type which satisfies bifurcation & gives accurate results,
• Performing Design factor calculations

THE SOLUTION

The structure was analyzed using Finite Element Method for elastic buckling analysis. The loading used for this analysis is unit loading. The structure is solved for bifurcation analysis & design factor calculations were performed.

The results showed that the structure is the calculated design factor for the structure is greater than the min. design factor as defined in clause 5.4 of ASME BPVC Sec. VIII Div. 2. Hence, the structure’s design was predicted to safe against buckle failure during its service life.

BENEFITS

• Behavior of the structure under its actual operating conditions is studied from a different point of view.
• Structural failure can be investigated for its cause to failure.