Regular deformation inspection on in-service natural gas pipeline can reduce accidents caused by pipeline failure. In this study, a novel contact-testing geometry inspection gauge was proposed and its multi-jointed soft detection arm was focused study. 3D printing technology and mold casting were used to fabricated newly designed detection arm. A finite element method (FEM) was used to analyze the process of the detection arm passing through the convex defect and optimize its joint number. Then, a series compared experiments were conducted with various convex defects to evaluate the superiority on measuring performance of multi-jointed soft detection arm. The experimental results show that compared to no-jointed detection arm, the multi-jointed detection arm has a more accurate experimental value especially for defects with closer heights (8mm and 10mm) and better relatively stable in repeated experiments. This study provided options for the design of flexible caliper pig on deformation inspection in pipeline.

Pipeline inspection gauge (PIG) is often blockage in the aging pipelines of stacked objects owing to the limitation of its passive control. In this study, a novel sealing disc with multi-jointed pneumatic webbed foot was designed which can achieve partial active control and ensure better seal performance. A finite element method (FEM) was proposed and successfully verified, then the bend performance of the sealing disc with single inflated foot was compared with whole inflated feet using the FEM, and the results show that they have good consistency. Next, the effects of two kinds of materials and five structural parameters on the performance of the sealing disc were studied using the FEM. The results show that the multi-material structure has batter performance on the bending angle and the expansion ratio compared to the same materials. As the air pressure grows, the position parameter of the joint (he) has little effect on the bending angle as well as the expansion ratio, and the bottom disc thickness (hd) has also slightly influence on the expansion ratio. Meanwhile, the thicker the webbed foot thickness (ht), the smaller the slope angle (β) and the thinner (hd), the larger the bending angle; the smaller the slope angle, the thicker the webbed foot thickness, the larger the expansion ratio. The conclusions obtained in this paper are beneficial for the design and optimization of PIG sealing discs for actively controlling. The research results provide theoretical reference for the study of intelligent and efficient pipeline pigging technology.