Study on the detection arm accuracy of a leaf spring caliper for detecting internal convex defects in gas pipelines

The safety of pipelines is an important factor in the natural gas industry. In natural gas fields, some pipelines are less than 200 mm in diameter, and these pipes cannot be inspected in ordinary inspection facilities. This paper describes the development of a leaf spring caliper to solve this issue. The factors that influence the accuracy of the detection arm were studied, a theoretical model of the leaf spring was constructed, and simulations were used to verify the theoretical model. Subsequent experiments were designed to study the influence of the accuracy of the detection arm under different working conditions. The experimental results indicate that the strain is proportional to the vertical displacement at the end of the detection arm under testing conditions. Based on an analysis of the process of a detection arm passing different height defects, a correction algorithm of the length was developed. In addition, a correction algorithm was developed for the height to adjust the speed and compression. The effectiveness of the developed correction formula was experimentally demonstrated.