The Design Of Crack Detection System For Ferromagnetic Pipeline

Ferromagnetic pipelines are widely used in many industries,such as petroleum,natural gas,chemical industry,railway infrastructure and electric power industries,but the material is easy to produce cracks due to corrosion and external stresses.In order to prevent the occurrence of serious accidents and reduce the loss of people's lives and property,it is necessary to detect the stress concentration and corrosion thinning areas of the pressure pipelines in advance.At present,other nondestructive detection methods have low efficiency,inconvenient operation,based on the principle of low frequency magnetic flux leakage,two ferromagnetic pipeline crack detection systems are designed,the systems mainly includes the generation of excitation signal,detection probe,signal processing,the skeleton and so on.The main contents are shown as follows:1.Several typical nondestructive testing methods and the existing pipeline crack detection systems based on low frequency electromagnetic are introduced.And the working principle of low frequency electromagnetic inspection technology is expounded.Aiming at the defects of the existing detection system,two new types of crack detection system for ferromagnetic pipe are introduced.2.The application of the low frequency electromagnetic detection technology in the pipeline is simulated theoretically.The 20# steel pipe is used as the research object in the simulation.Using COMSOL software to establish the model of pipeline defect detection,by changing the parameters(the number of turns of the coil,the magnetic core size,the lift off height),simulate the defects of different depth and shape.By observing the variation of the magnetic field around the defect,the optimum parameters are selected,which provides a reliable theoretical basis for the design of the crack detection system of the ferromagnetic pipe.3.Two new types of crack detection system for ferromagnetic pipe are designed.Based on the principle of low frequency magnetic leakage,using 20 Hz frequency's excitation,after amplifying to load to the excitation coil,using differential principle to detect magnetic field strength on both sides,when meeting the defect,the strength of the magnetic field changes,by analyzing the difference signal we can know whether there are defects.4.The random disassembly and installation of the crack detection sensor and a three channel sensor frame for longitudinal and transverse detection are designed,so that the defect detection of the ferromagnetic pipe is more flexible and convenient.5.A test platform is designed by using LABVIEW software to realize the system parameter setting,signal collection,defect recognition and acquisition,etc.,and show whether there are defects through the dot chart.