Modeling and simulation analysis of bi-directional PIG based on the pseudo-rigid body model

Pipeline inspection gauge (PIG) is essential to ensure the safe transportation of oil and gas pipelines. The sealing disc is an essential part of the bi-directional PIG. In a natural gas transmission pipeline, the sealing disc is in close contact with the inner wall of the pipeline, providing conditions for the fluid to be pressurized and creating a pressure difference for the PIG’s movement. The friction contact between the PIG and the pipe wall directly affects the efficiency of the PIG. Therefore, the mathematical model of the contact behavior between the sealing disc and the pipe wall can provide theoretical guidance for the pigging operation. In this paper, the pseudo-rigid body dynamics model of the sealing disc is established, which can be used to calculate the friction and deformation of sealing disc in pipeline. The finite element model of the PIG operating in straight pipe and girth weld pipe was established and verified. The trend of friction with interference, sealing disc thickness, and friction coefficient was obtained using the pseudo-rigid body model. The theoretical derivation and simulation of the PIG through the girth weld process were carried out. The results showed that the pseudo-rigid body model was in good agreement with the actual dynamic characteristics of PIG. The research results can guide the engineering practice and make the pig move smoothly.