UG-22 of the ASME BPVC Section VIII, Division 1, outlines various additional loadings that must be considered when designing pressure vessels. These include, but are not limited to:
Weight of the vessel and its contents
Wind and seismic forces
Reaction forces from supports and attachments
External pressure (e.g., vacuum conditions)
Thermal effects and stresses from temperature gradients
UG-27, on the other hand, provides the method for calculating the minimum thickness required for cylindrical and spherical shells under internal pressure. The standard calculation for thickness in UG-27 primarily focuses on internal pressure, but additional loadings from UG-22 must be taken into account to ensure that the vessel can withstand all possible stresses.
How UG-22 Loadings Are Incorporated in UG-27:
Combined Stress Analysis: When calculating the required thickness under UG-27, the additional stresses from UG-22 must be superimposed on the stresses calculated from internal pressure. This is often done using a combined stress analysis, where the stresses due to internal pressure are combined with those due to the additional loadings (e.g., axial loads, bending moments, and external pressure).
Modified Allowable Stress: The allowable stress used in the thickness calculation might be adjusted to account for these additional loadings. For example, if there are significant additional loads, the material's allowable stress might be reduced to ensure a conservative design.
Additional Thickness Requirement: In some cases, the presence of these additional loadings might require an increase in the calculated thickness beyond what is determined by internal pressure alone. This ensures that the vessel has sufficient strength to handle the combined effects of internal pressure and other forces.
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