Theoretical Deliberation on the Precision Quantification of a Flexible Caliper Sensor for Oil and Gas Pipelines

Caliper pipeline inspection gauges (PIGs) are essential devices for ensuring the safe operation of oil and gas pipelines. However, traditional caliper PIGs cannot detect multiple pipe deformations at one time, and the equipment components are complex and cannot be reused. With the continuous improvement of detection performance requirements in practical application fields, there is an urgent need for a detector that can accurately quantify deformation along the pipeline with a simple structure. To this end, a new type of flexible caliper PIG with strain sensors embedded in polyurethane caliper disks was designed, which is less disturbed by the internal environment of the pipeline. In this article, the theoretical model of the flexible gauging disk for the quantification of deformation is first presented. Then, the whole process of the flexible gauging disk through the dent is simulated by a finite element method, and the theoretical analysis is carried out by the dynamic model. Moreover, a flexible caliper sensor motion test bench is established to verify the feasibility and rationality of the proposed flexible detection method. Four experiments are designed to explore the factors affecting the precision of flexible caliper sensors. The experimental results demonstrate that the flexible caliper sensor can effectively detect the deformation defects in the pipe. The thickness, outer diameter, and material hardness of the flexible gauging disk have no significant impact on the detection accuracy, and the detection error increases with increasing running speed. Overall, this research provided a theoretical basis for the development of intelligent and efficient pipeline deformation inspection system.