Research On Internal Inspection Technology Of Pipeline Special Components Based On Magnetic Memory

Metal magnetic memory testing technology is a rising nondestructive testing technology,it has a bright future in pipeline inspection with its advantages of the ability to detect stress concentration,no need of pre-magnetization,light weight and so on.Presently,the application of metal magnetic memory testing technology in pipeline inner inspection is not mature,and the research of internal magnetic signal is mainly focused on the pipeline weld signal.Pipeline special components such as repair patches and branch pipes are common detection objects in the pipeline.In addition,the oil stolen valve is also the key detection object.The accurate identification of these objects' signals,and distinction from defects' signals can not only avoid false detection,but also assist the positioning calibration of the internal detector.In order to solve the above problems,this paper simulates magnetic field distribution of the above situations on the basis of the theory of metal magnetic memory effect and finite element analysis of magnetic field,including pipeline defects,repair patches,comprehensive structures,oil stolen valves and branch pipes.This paper also makes distinctions of magnetic memory signals between different structures,and analyzes the influences of the structure size,the lift off value of inspection,the direction of geomagnetic field on the measured signal,which laid a theoretical foundation for the distinctions of magnetic signals between pipeline defects and special components.This paper also designs a multi-channel detection system based on magnetic memory testing technology,which concludes design of mechanical structure,hardware,multi-channel synchronous data acquisition system,host computer software and so on.The data acquisition system takes FPGA as its core to control the multi-channel synchronous sampling.The experimental data is uploaded to the host computer through USB protocol to realize real-time data processing,imaging and storage.Moreover,in view of the requirements of the actual pipeline detection condition,the improved design of the detection system is proposed.After calibration of magnetic field for internal detection device,complete the pipeline inner inspection experiment with the detector above.The magnetic data of pipeline defects,repair patches,comprehensive structures are analyzed and compared with the results of finite element simulation.The experiment results show that the actual detection effect is relatively clear,and verified that the magnetic memory testing technology can be applied to pipeline detection,and can realize the identification between pipeline defects and repair patches.