Pipelines are one of the most reliable, environmentally responsible, and economical means for transporting oil and gas from production wells to processing and consumption sites. However, pipelines are susceptible to degradation over time due to various types of defects, temperature variations, and boundary conditions. In-line inspection (ILI) is a non-destructive assessment method commonly used for defect analysis of pipelines by using an inspection gauge. The passage of an ILI tool through an exposed section of pipe during an integrity assessment can excite vibrations and exert substantial forces, stress and deflections on the pipe due to weight and speed of the tool. When the excitation frequency due to ILI movements is close to the natural frequency of overall structure, the dynamic stress generated within the pipe can be sufficiently large to impose integrity concerns on the line. This research aims to study effects of the ILI tool passage through floating and partially supported pipes under a variety of boundary and loading conditions. Therefore, a combination of analytical and finite element (FE) methods are used to model the pipe, soil boundaries and moving ILI tool. The model is developed based on 1D Timoshenko beam theory with planar degrees of freedom and differential equations of motion will be solved numerically to predict displacement, strain, and stress as well as frequency response of the pipe. A finite element model in ABAQUS is also developed to verify the proposed model. The model is further validated using a lab-scale experimental setup powered by an electric motor to pull a mass inside an exposed pipe. The setup has been designed and fabricated in such a way to cover a wide range of speeds up to 10 m/sec. The comparison of the simulation and experimental results show that the proposed model is capable of predicting pipe dynamics effectively.


Dynamic Stress Analysis of an Exposed Pipe Subjected to Moving Ili Tool

Division / Sponsors: 
Pipeline Systems Division

Paper Proceedings: https://asmedigitalcollection.asme.org/IPC/IPC2020/volume/84447

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