One of the changes introduced in the latest edition of the ASME VIII Div 2 standard has been the way to assess protection against buckling failure when designing by analysis. Section 5.4 of the standard has been completely rewritten since the validation method proposed in previous editions was not reliable in the case of plastic buckling, that is, once the stress exceeds 0.55Sy, where Sy is the yield strength of the material.
The roadmap proposed by the current edition of the standard, which is mandatory from January 2024, is shown in the following scheme:
The methods for validating protection against buckling collapse are as follows:
- Method A, applicable to linear calculations (see Section 5.4.2 of the standard). This method consists of five steps in which, for each load case, the membrane stress is compared with a critical membrane stress.
If, during the analysis, any of the requirements of this method are not met, it would be necessary to validate protection against buckling using Method B.
The following image shows a practical case of buckling validation of a pressure vessel, focused on the vessel’s shell.
- Method B, considers both material non-linearity (elastoplastic calculation) and geometric non-linearity in the calculation model. If the calculation converges, we can affirm that the analyzed component is stable for the studied load combination.
At CADE, we are at the forefront of the changes implemented in the latest editions of the main design standards and the implications that modifications in validation procedures can have, as is the case with buckling protection, with the goal of offering both manufacturers and suppliers efficient and optimized designs that not only comply with current regulations but also allow for cost reduction and improved performance throughout the equipment’s life cycle.
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