Design And Experimental Research Of The Geomagnetic Detection System For The Damage Of The Buried Steel Pipeline

As an important transportation method for oil and gas,buried steel pipelines have become more extensive.After the pipeline is laid and operated,due to the influence of factors such as corrosion,third-party damage and natural disasters,some damage will inevitably occur.Therefore,it is of great significance to conduct non-destructive testing and safety evaluation of pipelines in service.The defect detection of buried steel pipelines without excavation is a long-standing difficulty in the field of pipeline inspection.The geomagnetism-based pipeline defect detection technology is a noncontact detection technology.Through the detection of the magnetic anomaly signal of the pipeline defect in the geomagnetic background,the non-excavation defect detection of the buried pipeline and the identification of the defect damage degree can be realized.At present,systematic and comprehensive research has not been carried out on the technical principles and implementation methods of defect detection methods for buried steel pipelines under the geomagnetic background.Based on the principle of geomagnetic detection,this paper studies magnetic anomaly signal detection instruments and effective extraction to achieve reliable identification of buried steel pipeline damage.The specific content and conclusions are as follows.(1)Based on the theoretical analysis of the magnetic properties of the magnetic medium,this paper discusses the magnetization mechanism of ferromagnetic materials and the relationship between the magnetic field intensity and magnetic induction intensity of ferromagnetic materials and explains the principle of damage diagnosis for buried steel pipelines under the geomagnetic field.And on this basis,it is proposed that the geomagnetic detection technology is a new type of non-destructive testing method based on the natural geomagnetic field,which can directly identify the pipe body of the buried pipeline without excavating the buried pipeline.defect.(2)Aiming at the characteristics of the magnetic anomaly signals of buried steel pipelines under the geomagnetic field,a multi-channel real-time high-speed data acquisition system based on FPGA and ARM and a full tensor array detection probe based on magnetic gradient tensor theory were developed.A new pipeline damage location method and error correction algorithm by real-time acquisition of magnetic probe detection data and the displacement of the magnetic probe relative to the detection starting point are presented,and the software and hardware design scheme of the instrument is described.(3)Aiming at the problem that it is difficult to extract the weak magnetic signal of the non-contact buried steel pipeline defect detection,a method of using the peak of the magnetic gradient tensor modulus to realize the pipeline defect detection is proposed,and the pipeline damage detection experiment plan is designed and the test is set up.Taiwan,based on the actual operating conditions of buried steel pipelines,explore the relationship between lift-off height and defect types and magnetic anomaly signals.The pipeline magnetic field data of the prefabricated defects are collected,and the data processing is completed according to the theory.It is verified that the array probe and the detection instrument can complete the high-precision magnetic gradient tensor measurement and can identify the defects to achieve the purpose of damage detection.(4)In order to accurately identify the signal characteristics of pipeline defects and assess the degree of damage to the pipe body,this article combines pipeline information,on-site inspection records,etc.,and uses a variety of processing methods to conduct data analysis to determine the damage level of the inspected pipeline defect.For damaged pipelines,the damage grade is determined according to the damage grade index F.