ABSTRACT
Determination of the differential collapse pressure rating of pipe without evaluating the effect of the internal pressure is always non conservative. The errors are highest (5 to 10 percent or greater) for thick wall pipe (API yield collapse mode) at high axial load and high internal pressure. The errors are negligible for thin wall tubulars or other applications where the axial load or internal pressure is low. The derivation of the triaxial analysis for thick wall pipe is provided. In addition, the equation is expressed on a single figure allowing the user to quickly determine the impact of ignoring the internal pressure for an application using thick wall tubulars. Adjustments are also provided for other than thick wall pipe to facilitate quick evaluation.
