Research On Harmonic Magnetic Field Detection Method Of Surface Steel Pipeline Damage Without Uncovering

As a major national lifeline project,pipeline transportation is an important infrastructure and livelihood project for transporting oil,natural gas,water,and various hazardous chemicals and process media,and plays a pivotal role in national economic and social development.In the process of pipeline transportation,in addition to the pipelines coated with anti-corrosion layers,there are also a large number of industrial pipelines,station pipelines,thermal pipelines,process pipelines,and offshore oil pipelines that require a thermal insulation layer(thermal insulation layer or cold insulation layer).It is used in oil refining,petrochemical,energy,aerospace,power station,nuclear energy and other industries.These pipelines need to work under high temperature,high pressure or low temperature conditions for a long time.The detection of pipeline defects,especially the defect detection at welds,is particularly important.If the pipeline damage cannot be detected,warned and repaired in time,it will eventually lead to the rupture of the pipeline,leakage of raw materials,economic losses and even major safety accidents,which will bring huge losses to the life and property of the country and people,and even cause environmental damage.pollution and cause ecological disasters.Therefore,regular and effective inspection of in-service pipelines has become an important way to ensure the normal operation of pipelines.On-site inspection of cladding pipelines still adopts manual inspection,visual inspection and other methods,which have problems such as low inspection efficiency,inconvenient operation,and poor inspection accuracy.There is still a lot of research work to be done in terms of practicality and practicality.To this end,based on electromagnetic theory,starting from improving the penetration of electromagnetic excitation signals and high-precision detection capabilities,by modulating high-frequency electromagnetic signals to low-frequency electromagnetic signals,the strong penetration of low-frequency signals and high-frequency signals are used.Sensitivity detection capability,a focused detection technology of harmonic magnetic field for ground steel pipelines without removing the cladding layer is proposed.Therefore,through mathematical modeling,finite element simulation,experimental verification,engineering test and other methods,the basic theory and key realization technologies of harmonic magnetic field detection for pipe damage without removing the cladding layer are systematically studied.The main research contents include:(1)Based on Maxwell’s electromagnetic field theory,a magnetic focusing detection probe and a harmonic magnetic field detection system are designed.According to the Biot-Saffar law,the magnetic field distribution model of the magnetic focusing detection probe is established.According to the characteristics of the spatial distribution of the magnetic field intensity generated by the detection probe,the optimal position of the sensor in the probe is determined to eliminate the a field signal interference.(2)Using the finite element simulation method,the basic principle of the harmonic magnetic field focusing detection technology is numerically simulated and analyzed by COMSOL Multiphysics multi-physics analysis software.The results show that the harmonic magnetic field focusing detection method can penetrate the coating layer to detect the pipeline,not only can determine the position of the defect in the axial direction of the pipeline,but also determine the distribution of the defect in the circumferential direction of the pipeline.(3)Aiming at the problem of primary field and external interference in the harmonic magnetic field detection signal,the fast Fourier transform and the short-time Fourier transform are used to process the sampled signal,and the effective identification of the defect detection signal is realized.In order to effectively extract the defect detection signal in the harmonic magnetic field,an effective identification method of the pipeline defect detection signal is proposed based on the synthetic aperture radar detection technology.effective extraction.(4)Based on the researched harmonic magnetic field detection technology,engineering experiments and engineering demonstration applications were carried out.The underground pipe galleries in Weihai and Siping were selected respectively,and the thermal pipelines with thermal insulation layers in the pipeline galleries were actually tested.The test results show that the harmonic magnetic field focusing detection technology has a good ability to detect thermal pipelines with cladding layers.,can meet the requirements of engineering inspection.