Application of Metal Magnetic Memory Method in Long-distance Oil and Gas Pipeline Defects Detection

Pipeline integrity is one of the most important concerns in petrochemical industry. Fast, effective and trenchless online inspection technique is highly desired. Non-contact Metal Magnetic Memory (MMM) Method can satisfy our need by detecting the abnormal magnetic signals in the stress concentration zone and is a new way for long-distance oil and gas pipeline detection. In this paper, the features of MMM detection for buried pipelines were summarized, some sections of pipelines in service were detected using this method, and the detection data were analyzed with differential and wavelet signal processing for noise analysis and useful signal extraction. We also summarized the relationship between the acquired signals and different types of stress concentration zones by means of pattern recognition, and performed qualitative analysis of different defect types. Excavations for verifications were conducted in the possible defects areas located by the data analysis to ensure the overall accuracy rate satisfactory. Some kinds of defects such as metal loss or corrosion were found in such magnetism abnormal areas. The results showed that MMM technique is a reasonable and feasible option for trenchless pipeline defect inspections.