Energy Change of Pipeline Signal Spatial Propagation Detected by Magnetic Tomography Method

doi:10.12422/j.issn.1672-6952.2024.02.011

Abstract

Abstract:

Magnetic tomography method has been widely used for nondestructive external inspection of buried and submarine pipelines, which is based on the principle of metal magnetic memory to discern the danger level and location of the stress concentration zone by measuring the anomalies in the spatial magnetic field distribution outside the pipeline. The distribution characteristics and spatial propagation law of pipeline inspection signal detected by magnetic tomography method, the energy distribution and change law of spatial magnetic memory signal in the stress concentration zone of magnetized pipelines are studied in this paper. The magnetic dipole field is used to establish the magnetic field model in the stress concentration zone of the inner wall of the pipeline, and the magnetic energy and energy density of spatial magnetic memory signals under different lift?off values outside the pipeline are finite element calculated based on the magnetic energy theory to derive the distribution law of spatial magnetic field and the correlation of magnetic energy density of magnetic signals under different lift?off value is analyzed. The results show that the spatial magnetic field energy outside the pipe decays with the increase of lift?off value, and the decay is the fastest within the distance of 50 mm from the outer wall of the pipe to the physical force; the correlation of magnetic energy density of different lift?off values shows that the magnetic signal detected by magnetic tomography method outside the pipe is homologous with the signal in the stress concentration zone of the inner wall of the pipe. Theoretically, it explains the effectiveness of magnetic tomography method and also provides evaluation indexes for extracting effective signals from the detection data.

Key words: Magnetic tomography method, Pipeline detection, Metal magnetization, Magnetic energy

摘要：

磁层析成像管道检测方法已经被广泛应用于埋地和海底管道的无损外检测。该方法基于金属磁记忆原理，通过在管道外测量空间磁场分布中的异常情况来判别应力集中区的危险等级和位置。为了研究磁层析成像法管道检测信号在空间中的分布特征和传递规律，对磁化管道的应力集中区空间磁记忆信号的能量分布和变化规律进行了研究。利用磁偶极子场建立管道内壁应力集中区磁场模型，基于磁能理论对管道外不同提离空间磁记忆信号的磁场能量和磁能密度进行有限元计算，得出空间磁场的分布规律，分析了不同提离磁信号磁能密度之间的相关性。结果表明，管道外空气中的磁场能量随着提离值的增加而衰减，在管道外壁至提离值小于50 mm时衰减最快；管道外磁层析成像法检测的磁信号与管道内壁应力集中区信号同源。从理论上解释了磁层析成像管道检测的有效性，为从检测数据中提取有效信号提供了理论依据。

关键词: 磁层析成像, 管道检测, 金属磁化, 磁能

CLC Number:

TE83

Linlin LIU, Lijian YANG, Songwei GAO. Energy Change of Pipeline Signal Spatial Propagation Detected by Magnetic Tomography Method[J]. Journal of Liaoning Petrochemical University, 2024, 44(2): 71-76.

刘琳琳, 杨理践, 高松巍. 磁层析成像管道检测信号空间传递过程的能量变化[J]. 辽宁石油化工大学学报, 2024, 44(2): 71-76.

Figures/Tables 9

Fig.1 Current?carrying loop model

Fig.2 Schematic diagram of the simulation model

Fig.3 Magnetic flux density of the magnetic memory signal at the outer wall of the pipe in the stress concentration area

Fig.4 Plane section view of the distribution of magnetic lines of force of the current?carrying loop at the top of the inner wall of the pipe

Table 1 Magnetic energy at different lift?off values in the air outside the pipe

提离值/mm	0	50	100	150	200
磁场能量/nJ	923.00	410.00	59.90	13.00	3.24

Fig.5 Magnetic field energy and its fitting curve under different lifting values

Fig.6 Magnetic field energy density at different removal values

Fig.7 Correlation coefficient curves of magnetic energy density with different removal values

Fig.8 The relationship between the maximum correlation coefficient of magnetic field energy density and scanning distance

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