三轴漏磁内检测信号分析与应用

Signal Analysis and Application of Tri-axial MFL Sensors for Pipeline In-line Inspection

介绍了三轴漏磁内检测技术的原理。金属损失产生的漏磁场是空间三维矢量场,三轴漏磁内检测器在轴向、径向和周向上分别使用单独的霍尔传感器来记录漏磁信号。分析了三轴漏磁信号的特征:轴向漏磁信号可以估算缺陷宽度,但结果极不可靠,对缺陷长度和缺陷深度的指示精度不高;径向漏磁信号可以清晰界定缺陷长度,结合轴向漏磁信号基本能够确定缺陷深度,但难以准确判定缺陷宽度;周向漏磁信号能够较精确地判定缺陷的宽度和长度,结合轴向和径向漏磁信号,亦可提高缺陷深度的判定精度和准确性。对三轴漏磁内检测技术的研究和现场应用表明:三轴漏磁内检测器能够检出各类常规金属损失缺陷和传统漏磁检测器难以检测出的非常规缺陷,如狭长轴向缺陷、环焊缝缺陷、螺旋焊缝缺陷以及凹陷等。与传统漏磁检测器相比,三轴漏磁内检测器显著提高了金属损失缺陷尺寸的判定精度。

The principle of Tri-axial magnetic flux leakage(MFL)pipeline in-line inspection(ILI)technology is introduced.The leakage field is a three dimensional magnetic vector,and the MFL tool records MFL signal using individual sensors in all three directions:axial,radial,and circumferential.The signal characteristic recorded by Tri-axial sensors is analyzed in detail:according to the axial MFL signal,the estimated defect width is unreliable,and defect length and depth can be defined,but it can not be solely relied upon for high accuracy results.Defect length can be defined crisply from the radial MFL signal,and defect depth also can be determined approximately when combining with the axial MFL signal,but defect width is still difficult to accurately define.Defect width and length can be determined from the circumferential MFL signal with high definition and repeatability,so it increases accuracy in depth estimation when combining with the MFL signals of the axial and radial.Research and field applications show that Tri-axial MFL ILI tool not only can detect various usual metal loss defects,but also can identify unusual defects,such as narrow axial defects,girth weld defects,spiral weld defects,and dents,which are difficult to detect by traditional MFL ILI tool.Comparing with traditional MFL tool.Tri-axial MFL tool can considerably improve the sizing accuracy of defects.