Research On Application Of Magnetic-Acoustic Trenchless Detection Technology In Thermal Pipeline

With the increase of the age of thermal pipelines in China,the problem of corrosion and leakage of urban thermal pipelines has become more and more frequent in recent years.Corrosion leakage will cause energy loss,maintenance burden of heating enterprises and affect the normal use of heating users.Therefore,in order to avoid the loss caused by pipeline leakage,it is necessary to check the pipeline leakage in advance.However,the techniques for detecting leaks that are common at home and abroad still have shortcomings in the accurate location of pipeline leaks and misjudgments at the leak points.In this paper,the magnetic-acoustic non-excavation detection technology of thermal pipeline is proposed for the physical characteristics of thermal pipeline leakage,and a system for thermal pipeline leakage detection is designed.Firstly,based on geomagnetic theory and sound propagation characteristics,this paper expounded the principle of magneto-acoustic non-excavation detector for thermal pipelines.From the theory of weak magnetic detection and the theory of water leakage acoustic wave detection,the feasibility of the instrument in leak detection application was verified.According to the design scheme of the magnetic-acoustic detection system,the designed detection system includes four aspects: magnetic signal detection unit,acoustic signal detection unit,system detection software and auxiliary detection device.The process flow that can be used in the actual test what is established for the system,and the instrument system operator provides learning guidance in the field test to achieve higher detection efficiency and detection accuracy.Secondly,system used three-axis fluxgate sensor and piezoelectric vibrating sensor as system data acquisition device,combined with micro industrial computer and designed software platform to achieve system control;In the analysis of the system data signal,the feature quantity of the abnormal signal was extracted by the characteristic spectrum analysis of the acoustic signal and the energy analysis of the magnetic gradient anomaly basis function.Then,the leakage of the heating pipeline during the heating period was simulated,the thermal pipeline leakage test scheme was formulated,and the characteristics of the magnetic field signal and the characteristics of the acoustic signal collected by the test are comprehensively analyzed,which had a good experimental effect on the qualitative andpositioning of the pipeline leakage point.The test results showed that there was a100 mm error between the 5 mm through hole positioning and the actual defect position at the 12 o'clock direction of the pipe,and the 8 mm through hole positioning at the 3o'clock direction of the pipe had an error of 150 mm from the actual defect position.Therefore,the test showed that the through hole of 5 mm had a good detection effect.At the same time,the error between magnetic anomaly localization,acoustic signal localization and magnetic-acoustic comprehensive analysis and the accuracy of leak location were compared and analyzed.The position error of the magnetic tube acoustic-non-excavation detection technology in the location of the leak point was obtained.Within 200 mm,it fully meets the actual needs of on-site inspection.Finally,the on-site field inspection and excavation verification further demonstrates the applicability of the magneto-acoustic non-excavation detection technology of the thermal pipeline.The method also has good applicability and has important research significance for urban thermal pipeline leakage detection.