Which factors must be determined when using external pressure charts?

• A. Factor C and D
• B. Factor A and B
• C. Temperature and Pressure
• D. Material and Thickness

Answer: (B)

External pressure buckling charts rely on two geometry/condition descriptors to identify the correct curve you should use. These two factors capture how the shell is supported and its shape, so they map your specific case onto the appropriate portion of the chart. Once you’ve determined these two factors, you can read off the allowable external pressure from the chart and check it against your design.

Temperature or the actual pressure values aren’t the two chart-defining inputs; they’re data you bring to the design, but the chart’s curve is chosen from the two geometry/boundary-condition factors. Likewise, while material properties and wall thickness matter for the overall design, they don’t determine which curve on the external pressure chart applies—that role is fulfilled by the two factors that summarize geometry and end conditions.