Study of MFL signal identification in pipelines based on non-uniform magnetic charge distribution patterns

Abstract

Magnetic flux leakage (MFL), a pipeline internal detection, is the mainstream technology for international oil and gas pipeline safety maintenance. To address the problem of large errors in the assessment of defects in pipeline inspection by existing theoretical analysis models, this paper introduces the charge density parameter to establish a mathematical model of non-uniform magnetic charge for pipeline leakage detection and calculates the non-uniform distribution pattern of magnetic charge on the defect side wall. The contour plot method is proposed to visually analyze the size of defects. To compare the error between uniform and non-uniform models, and verify the correctness of the theoretical model, experiments were systematically conducted on the X70 pipeline with internal MFL technology. The results show that: the magnetic charge distribution curve is symmetrically shaped at the center of the defect, with a valley at the center and two peaks at the defect edge. As the defect depth and width increase, the magnetic charge density increases sharply near the surface and edge. The peak-to-valley spacing and peak-to-valley values in the contour map of the magnetic flux leakage signal can directly reflect the location and size of defects. The signal characteristic values follow the trend of a first-order decreasing exponential function as the value of the lift-off increases. The first-order derivative of the signal characteristic value tends to decrease and then increase as the mesh size decreases, and the extreme point of the derivative curve is the best mesh size.

An ultrasonic in-line inspection data processing method considering invalid data caused by sensor failure

“…at the sampling time l i from X m×n×l . The isolation forest model iForest i is adopted to predict the validity of data x k in X l , and the predicted value of the validity y k of each data point x k is saved into (5) to calculate the ratio of the sum of the amplitudes of each invalid waveform point |x i | which outliers to the sum of the amplitudes of all points in the waveform X l . If ratio exceeds the threshold T, the waveform X l is invalid; otherwise, the waveform X l is normal…”

“…marginal cost, long transportation distance, large volume per unit time and continuous supply [1][2][3]. However, with the extension of the service time of the pipeline, its metal properties will inevitably deteriorate or even be damaged [4,5], which will cause further corrosion or even leakage of the pipeline [6], bringing substantial economic losses and irreversible impact on the environment [7]. To ensure the pipeline's safe operation, routine inspections should be carried out every 3-5 years, and non-destructive testing should be carried out periodically.…”

A high-precision TMR sensor array system for detecting surface and internal defects in thin sheet of steel

“…Multiple nondestructive testing techniques have been applied to defect detection in thin steel, each with its own advantages and limitations [2]. Ultrasonic testing, magnetic particle testing, eddy current testing, radiographic testing (RT), magnetic flux leakage (MFL), and penetrant testing (PT) are commonly used non-destructive testing techniques [3]. They have been successfully applied but also have their respective limitations.…”

A novel non-contact, magnetic-based stress inspection technology and its application to stress concentration zone diagnosis in pipelines

“…Pipeline transportation is one of the most important methods of transportation for oil and gas products [1,2]. It has the advantages of strong transportation capacity and low operating costs [3].…”