Chapter 5 - Buckle Propagation in Pipe-in-Pipe Systems

Abstract

Buckle propagation can also affect pipe-in-pipe systems. Propagation pressure PP2 is the lowest pressure at which a buckle will propagate collapsing both the outer and inner pipe. Propagation pressure PPS is the lowest pressure at which a buckle will propagate only in the outer pipe, leaving the inner one intact. Experiments are employed to establish the parametric dependence of the two propagation pressures of pipe-in-pipe systems. The results are used to generate empirical relationships for PP2 and PPS. Modeling includes simple plastic hinge models and 2-D finite element models, which are used to explain the physics of these propagating instabilities. Fully 3-D finite element models such as the ones presented are shown to be the most accurate options for calculating the two propagation pressures. The chapter provides guidance on how the two propagation pressures can be used in the design of pipe-in-pipe pipelines.