子母型海底管道通常以主管线输送海洋油气，子管线输送化学物质的方式进行管道运输。母管规格（外径）通常为6~12 inch（15.24~28.48 cm），子管规格（外径）通常为2 inch（5.08 cm）。母管环焊缝通常采用全自动超声检测技术（AUT）进行检测，而2 inch子管由于设备工装限制，AUT技术无法应用。若采用射线检测技术（RT），不仅检测效率低，安全风险高，还极大地影响了子母管的铺设效率。针对以上问题，对相控阵超声检测（PAUT）技术进行研究，设计开发了满足2 inch子管环焊缝检测的PAUT工艺，并对制作的35个管径为2 inch，壁厚为6.4 mm海管的人工缺陷焊缝（共105个人工缺陷）进行检测和缺陷高度定量精度评价，以评估该PAUT检测工艺对2 inch子管环焊缝各区域缺陷的检出能力和高度定量精度。

In the bundled pipeline, the main pipeline was applied to transfer the offshore oil & gas, while the piggy pipeline was applied to transfer the chemicals. The O.D of the main pipeline was from 6 to 12 inch normally, and the O.D of the piggy pipeline is 2 inch. For the main pipeline, the priority inspection method was automated ultrasonic testing method (AUT), while for the piggy pipeline, the AUT method cannot be used due to the limitation of AUT scanner. If RT method which was not only of low efficiency, but also of high safety risk, was used, it would slow down the laying efficiency of pipe-laying. In order to solve the problem, the article states the research of the phased array UT technique, and designs a new scheme for the 2 inch piggy pipe, and performs the inspection and data analysis of the 35 defective welds (O.D 2 inch, W.T 6.4 mm) (105 induced defects in total). And then, the probability of detection and height sizing accuracy of the defects in all zones of the 2 inch piggy pipe can be evaluated.