Design Equation of Buckle Propagation Pressure for Pipe-in-Pipe Systems

Abstract

This paper focuses on the buckle propagation pressure of a pipe-in-pipe system under uniform external pressure. After the validation of the finite element model used in this research, several effects were studied. At first, the effects of the initial imperfection of the inner pipe, including the ovality and eccentricity, were checked out. Second, the influence of the scantling of the inner and outer pipes was tested. It was found that the dominant factor which affects the buckle propagation mode is changeable. Then, the boundary value of the above factor was investigated by varying the ratio of the outer and inner diameters. Finally, after a summary of the calculation results, an empirical formula was proposed to illustrate the relationship between the buckle propagation pressure and the geometrical parameters of the pipe-in-pipe system. Utilizing this formula, the buckle propagation pressure of the pipe-in-pipe system can be estimated rapidly with good accuracy.