Dynamic Stress Analysis of Exposed Pipes Subjected to a Moving In-Line Inspection Tool

Abstract

In-line inspection (ILI) is a non-destructive assessment method commonly used for defect assessment and for pipeline monitoring. Passing an ILI tool through an excavated or exposed section of a pipe during an integrity assessment can excite vibrations. The ILI tool’s weight and speed can exert substantial forces, stresses, and deflections on the pipe section. When the excitation frequency from the ILI tool’s movement is close to the pipe’s natural frequency, the dynamic stress generated within the pipe can become great enough that it creates integrity concerns on the pipeline. This research aims to study the effects of an ILI tool’s passage through exposed and partially supported pipes under a variety of boundary and loading conditions. A finite element model of an exposed pipe section is developed based on the Timoshenko beam theory to predict the pipe’s displacement, strain, stress, and frequency responses under a wide range of excitation frequencies. The model is further validated using a lab-scale experimental setup with a mass that moves at different speeds. A comparison between the simulation and the experimental results shows that the proposed model can effectively predict the pipe’s dynamics.