Abstract:
A pipeline is a long pipe used to transport petroleum products, natural gas, etc. After a certain period in service, the debris and residual products get stuck inside, and thus the transport via that pipeline becomes inefficient. For enhancing its performance again, that pipeline must be cleaned properly and inspected to check its operating physical conditions. The mostly used technique is to introduce a tool known as Pipeline Inspection Gadget (PIG), into a pipeline and be pushed throughout by the fluid.
The PIG in consideration is made in a medium density polyurethane foam and has a larger diameter than the inner diameter of the pipeline. The pipeline is formed of pipes and elbows. The driving force is the fluid pressure.
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In order to know the type of motion in study, a mathematical modeling was performed by considering all forces acting on the PIG. After applying the Newton’s second law of motion, a nonlinear second order differential equation was obtained. Furthermore, the PIG being made in foam, it was concluded that this type of analysis is a highly nonlinear transient dynamic analysis.
Among the available commercial software, ANSYS LS-DYNA, a nonlinear dynamic explicit finite element code, was found to be more powerful in computing and simulating such a nonlinear dynamics problem.
For a successful pigging operation analysis, the effect of diametric interference was discussed by increasing the PIG diameter and applying variable pressure. Inflation control was set to adequately seize the region involved in frictional contact. Throughout this work, the fluid flow analysis was not performed.
The research presented in this thesis indicates the potency of the adopted approach to fairly predict the dynamic behavior and stress analysis of a medium density polyurethane foam PIG.
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