The Pressure Vessel Research Committee's Long Range Plan included a Design Division Problem Number IV, "Design Procedures for Tubes under External Pressure" for many years. It had been recognized for some time that the basis for the design rules for tubes as given in the retracted Figure UG-31 of the ASME Boiler and Pressure Vessels Code Section VIII, Division 1 (Ref. l), was inconsistent with modern theory for the collapse of tubes under external pressure. Modern theory recognizes the dependence of elastic modulus, tube thickness to diameter and tube length to diameter ratios, stress level, and geometric out-of-roundness on tube collapse. Figure UG-31 ignores elastic modulus, length to diameter ratio, and out-of-roundness and, therefore, is suspect.

An explanation for these omissions is that the data that provided the basis for Figure UG-31 (see Fig. 1) was developed from a 50-year-old test program on long lap welded steel tubes. Since the test data was limited to long tubes of only one length to diameter ratio and one material, the elastic modulus and other effects could not be discriminated. For want of alternative data, Figure UG-31 had been widely used over the years for the design of seamless tubes of many materials.