The axial crack testing model for long distance oil-gas pipeline based on magnetic flux leakage internal inspection method

Abstract

Traditional pipeline magnetic flux leakage (MFL) internal technology mainly uses axial excitation method, which could not recognize the narrow crack defects in the axial direction of the pipe. In this paper, by using a linear magnetic dipole model to study the circumferential excitation method, the detection model of axial crack in pipeline is established, and the relationship between MFL signals and the geometry characteristics of axial cracks is calculated. Finally, the detection accuracy and identification method of axial cracks is analyzed. Research results show that: non-uniform magnetic field generated by circumferential excitation can effectively detect the narrow cracks in the axial direction of the pipeline and distinguish the depth and the width characteristics of cracks. However, the background magnetic fields near the magnetic poles have great influence on the detection accuracy, and the smooth interpolation method of the cubic-spline interpolation can be used to reduce the influence effectively. IntroductionPipeline MFL internal inspection technology is the mainstream technology to maintain the safe operation of long-distance oil -gas pipeline [1][2][3][4] . This technology belongs to the monopoly technology in the world, for it is only mastered by a few Highlights 1. The MFL internal inspection technology can maintain the safe operation of pipelines.2. The axial cracks are more hazardous than circumferential cracks for pipelines.3. The circumferential excitation method can improve the confidence of the MFL device. 4. The axial cracks can be identified by circumferential excitation method.5. The MFL internal inspection of defects in arbitrary direction is possible to realize.

Evaluation of Composite Wire Ropes Using Unsaturated Magnetic Excitation and Reconstruction Image with Super-Resolution

“…It can be seen that the UME testing system has smaller size, lighter weight and simpler operation. 1 Detection speed of remanence was the same as UME, and slow testing speed can guarantee compete sampling; 2 Magnetizing time of remanence was 6 s every time, and it mostly needed to be implemented more than three times in the experiment; 3 Core components were transplanted to a remanence assembly.…”

“…Thus, there is leakage of the magnetic field around the defect region [1], where the magnetic distribution is relevant to the width and depth of the defect [2]. Finite element analysis has been applied to research the relationship between defect features and MFL distribution, particularly in pipeline testing [2][3][4]. However, in wire rope detection, there were major defects of broken wires, abrasion, corrosion, and diameter shrinkage; among these, broken wire is the most dangerous defect for security [5].…”

Measurement System of Metal Magnetic Memory Method Signals around Rectangular Defects of a Ferromagnetic Pipe

“…Thus, the pipeline network requires periodic inspections and suitable maintenances that avoid future accidents. Generally, in these inspections conventional NDT techniques are used, such as infrared thermography testing, radiographic testing, visual testing, ultrasonic testing, acoustic emission, liquid penetrant testing and Eddy current testing [3][4][5][6]. Liquid penetrant testing is useful for inspection of surface defects in ferromagnetic samples, although these defects should be contaminants free [7].…”

Application Research of the Non-Destructive Testing Using Optical Fiber Sensor

“…Certainly, they have their own advantages and disadvantages. At present, ultrasonic testing (UT) technology [1] and Magnetic Flux Leakage Testing (MFLT) technology [2] are the most mature and widely used in pipeline and plate inspection. However, there are some shortcomings in ultrasonic testing technology, such as the need for coupling agent and the high requirement for the pipe surface cleanliness.…”