Collapse Mechanisms of Pipe-in-pipe Systems under External Pressure during Operation

摘要

This study investigates collapse mechanisms of the inner pipe of a pipein-pipe (PIP) system under external hydrostatic pressure. It is observedthat the geometric and material properties of the outer pipe affect thecollapse pressure of the inner pipe (P_(ci)). A finite element analysis (FEA)is presented and is validated against the experimental results. Using thevalidated FEA, a parametric study is conducted. An empirical expressionis proposed for P_(ci). Then the collapse mechanisms of the inner pipeduring the operation, by incorporating various fractions of the burstpressure in the inner pipe, are studied using the FEA and are comparedto the response of PIP with no internal pressure. It was shown that thecollapse pressure of the inner pipe when the outer pipe caused a localcontact pressure is not significantly affected by the internal pressure.