Due to corrosion, cracks or damage, long-distance oil and gas pipelines may leak during use. Oil and gas leakage will not only pollute the surrounding environment of long-distance pipelines, but also may cause safety accidents such as combustion and explosion, resulting in huge economic losses. . Therefore, long-distance oil and gas pipelines need to be regularly tested to ensure the safety and reliability of the pipeline.
The detection methods of long-distance oil and gas pipelines include ultrasonic method, magnetic flux leakage method, and in-pipe television camera method. In the detection of long-distance oil and gas pipelines, the MFL (magnetic flux leakage) method is widely used in the detection of pipeline defects. The MFL method mainly relies on high-precision magnetic flux leakage, advanced signal processing and data storage systems, using ground analysis equipment to distract the detection results to obtain data on various defects and damage state parameters in the pipeline. The basic principle of pipeline magnetic flux leakage detection is: use a permanent magnet and a steel brush to apply a magnetic force to the pipeline, the free end of the steel brush is in contact with the inner wall of the pipeline, and the inner wall of the pipeline is magnetized under the action of an external magnetic field. If the inner wall of the pipeline has no defects, the magnetic field lines are distributed It is very regular; if the inner wall of the pipeline is defective, it will cause the magnetic resistance to change, the magnetic permeability change will cause the magnetic field lines to bend, and part of the magnetic field lines of the original inner wall of the pipeline leak out of the pipe wall to form magnetic flux leakage; after the detection sensor in the pipeline leakage magnetic field detects the leakage magnetic field corresponding induction signals will be generated, and the induction signals will be stored after processing. Finally, the data analysis system will find out the defect location and severity of the oil and gas long-distance pipeline, to guide the pipeline repair construction personnel to excavate and repair the pipeline.
The permanent magnets in the MFL method generally choose samarium cobalt magnets. Samarium cobalt magnets’ magnetic performance as strong as Neodymium magnets, providing strong magnetic field. And they have good high temperature resistance and corrosion resistance, they are suitable for use in complex and changeable outdoor environments.