Research on Features of Pipeline Crack Signal Based on Weak Magnetic Method.

Bin Liu,He Zhang,Jian Ren,Luyao He,Ning Luo,Ziqi Liu

doi:10.3390/s20030810

Abstract

Quantitative online detection of microcracks in long-distance oil and gas pipelines is an international problem, and the effective detection method is still lacking. In this paper, a mathematical model of non-uniform distribution of crack magnetic charges is established based on the stress distribution laws of pipeline cracks under internal pressure. The weak magnetic signal characteristics of pipeline cracks with different sizes are analyzed. The internal pressure increasing factor of weak magnetic signals are extracted to analyze the corresponding relationship between crack size and weak magnetic signals. The experimental study of the X70 pipeline is carried out. The results show that the axial component of the weak magnetic signal at the crack has a maximum value near the tip, and a minimum value appears in the middle of the crack. The internal pressure increasing factor is introduced to quantify the weak magnetic signal, the crack is in a safe state (not expanding) when the internal pressure increasing factor is positive, the weak magnetic signal has a linear relationship with the crack size. However, the crack is in a dangerous state when the internal pressure increasing factor is negative, and the pipeline crack will expand as the internal pressure increases.

Highlights

Due to the unreasonable arrangement of pipeline structure or defects in materials, stress concentration will be formed in the long-distance oil and gas pipelines, and stress cracks will often occur in the relevant areas, which will affect the stability of the pipeline operation [1,2,3,4,5]
A non-uniform magnetic charge model is established based on the stress laws of pipeline cracks under internal pressure
The results show that: the axial component of characteristics at the crack are extracted to determine the safety of the crack

Summary

Introduction

Due to the unreasonable arrangement of pipeline structure or defects in materials, stress concentration will be formed in the long-distance oil and gas pipelines, and stress cracks will often occur in the relevant areas, which will affect the stability of the pipeline operation [1,2,3,4,5]. The existing theoretical model calculates the magnetic signal on the premise that the stress concentration near the crack is approximately uniform This method simplifies the calculation process and reduces the amount of calculation, the error is large and it is difficult to accurately describe the weak magnetic signal characteristics of the crack. The systematic experiment is carried out, which lays a foundation for the quantitative detection of microcracks

Numerical Model of Non-Uniform Crack Magnetic Charge

Schematic crack magnetic

Experiment

20 Distance

Findings

Conclusions