The Stress concentration is the main reason of damage to ferromagnetic metal pipelines. Through effective detection,the use status of metal pipelines can be predicted and the safety of equipment can be effectively guaranteed. The ferromagnetic effect of the material under stress is analyzed by the energy balance theory of ferromagnetic materials. The 3D simulation model of ferromagnetic materials is built by simulation software based on the metal band theory, and the magnetic effect characteristics of the system under tension stress are calculated. The weak magnetic field detecting sensor based on differential symmetrical structure is designed and manufactured. The stress concentration system of different types of pipelines is detected by the stress detection system based on the weak magnetic sensor. The stress concentration is verified by other stress detection methods. The results show that the weak magnetic sensor can effectively detect the weak magnetic field signal on the pipeline surface, and the weak magnetic field signal shows violent fluctuation characteristics in the stress concentration region. Various detection methods verify the effectiveness of the weak magnetic stress detection. Weak magnetic stress detection technology can effectively detect pipeline stress concentration caused by defects or deformation.

In order to study the reliability of phased array ultrasonic testing for pressure pipe girth welds. In this paper, φ273 mm×13 mm and No. 20th steel pipe are selected and welded by butt ring welding, The weld area is evenly divided into 6 the same length areas and preburied five different defects. Phased array equipment, X⁃ray equipment and diffraction time difference ultrasonic testing equipment were used to detect the weld seam respectively. The relative data of each defect are measured by phased array equipment, and compared with the data of defect length and x⁃axis location obtained by X⁃ray detection, and with the data of defect height measured by Diffraction Time⁃difference Ultrasound Detection. High reliability of PAUT technology for welding Joint inspection of pressure pipeline. For rework and defect recording, PAUT technology is superior to TOFD ultrasonic detection technology and RT technology.