Structural Coupled Electromagnetic Sensing of Defects Diagnostic System

Magnetic flux leakage (MFL) detection methods are widely used to detect pipeline defects. However, it is limited by the detection orientation and magnetization. Besides, bulky excitation systems are incapable of adapting to the complex detection environments. This article proposes a new electromagnetic structured coupling sensing of merging alternating current field measurement and MFL within a multiparameter system for different types of pipeline defects detection. In particular, a novel electromagnetic coupling sensor structure is proposed, which enables simultaneous interaction between the excitation modes of yoke and coil. Magnetic yoke is integrated to magnetizing the axial pipeline to detect the circumferential surface and subsurface defects while the coil excites the circumferential uniform alternating current field and recognizes the axial defect. The novel structured sensing is highly sensitive to the detection of both surface and subsurface defects. Simulation and experiments on defects in several samples have been conducted to validate the reliability and efficiency of the proposed system.

I. Introduction

The integrity assessment of pipelines has commanded significant attention in the oil and gas industry. However, in the service pipeline, structural damage, corrosion, and geometric discontinuity in a harsh environment will affect the transportation performance and safety [1], [2]. Fuel leakage in the pipeline may cause badly damage to the environment, resulting in explosion, fire, and even injuries of pipeline network. In particular, the detection and quantification of different defects exist challenging of nondestructive testing (NDT) in pipeline integrity diagnosis [3]–[5]. Among the NDT methods, magnetic flux leakage (MFL) testing is invariably used for pipeline crack detection. However, the limitations of MFL are insensitivity to crack parallel to the magnetization direction while subsurface defects are difficult to be distinguished due to the ambiguity of signal-to-noise ratio (SNR).