为了填补国内利用外检测方法对埋地钢质管道金属损失缺陷实施可靠检测的技术空白,开展了基于多频电磁的埋地钢质管道金属损失缺陷外检测方法研究。采用理论分析与有限元仿真分析相结合的方法,研究了不同频率交变电流流经管道内、外壁缺陷时电流的分布特征,分析了由内、外壁缺陷导致的管道周围磁场变化,并通过实验对该检测技术的可行性进行了验证。研究表明：1)在埋地钢质管道两端施加含有多个频率的交变电流,当交变电流流经含金属损失缺陷的管段时,交变电流的流动将会发生异常，管道内壁缺陷与外壁缺陷对交变电流流动产生异常的频率存在差异;不同金属损失缺陷深度导致不同频率电流产生的异常程度也存在差异；2)当流经含缺陷管段的交变电流发生变化时,管道周围相应频率的交变磁场也会发生变化,通过检测、分析管道周围不同频率磁场信号变化特征可实现对金属损失缺陷的识别及量化；3)实验结果与仿真分析结果一致,采用多频电磁方法可以实现对埋地钢质管道金属损失缺陷的非开挖检测。研究为开发基于多频电磁技术的埋地钢质管道金属损失缺陷非开挖检测设备提供了基础和参考。

In order to realize the reliable inspection of metal loss defects in buried steel pipelines by using the external inspection method in China, the non-excavation inspection method for metal loss defects in steel pipelines based on multi-frequency electromagnetic is studied. By means of theoretical analysis coupled with finite element simulation, the distribution characteristics of alternating current at different frequencies flowing through the inner and outer wall defects of the pipeline are studied. The changes of the magnetic field around the pipeline caused by the inner and outer wall defects are then analyzed. Finally, an experiment is conducted to verify the feasibility of this inspection technology. The results show that: 1)When the alternating current with multiple frequencies is applied at both ends of the buried steel pipeline, if there is a metal loss defect in the buried pipeline, an abnormal signal occurs in the flow of alternating current. There is a significant difference between the frequency of occurrence of abnormal alternating current flow due to inner and outer wall defects. Similarly, the degree of abnormality of different frequency current flow caused by different depth of metal loss defect is also different. 2)When the alternating current begins to change as it flows through the defective pipe section, the alternating magnetic field of the corresponding frequency around the pipeline will also change. The identification and quantification of metal loss defects can be achieved by inspecting and analyzing the variations in the signals of various frequency electromagnetic field around the pipeline. 3)The experimental results are consistent with the finite element simulation results, therefore demonstrating that the non-excavation inspection technology based on multi-frequency electromagnetic can be used for the inspection of metal loss defects in buried steel pipelines. This research provides a basis and reference for the development of non-excavation detection equipment for metal loss defects of buried steel pipelines based on multi-frequency electromagnetic technology.