Research Of Drill Pipe Of Direct Current Excitation Magnetic Flux Leakage Detection Technology

Drill pipe is an indispensable key components in oil drilling rigs.The application of drill pipe defection automatic detection system for improving the efficiency of production and reducing manual labor intensity, drilling accidents and reduce economic losses is of great significance. The goal of the thesis is to achieve drill pipe defection automatic detection system.Research the correlative question with application of magnetic flux leakage. Such as transverse defection detection, lengthwise defection detection and data acquisition method with multi-channel defection signal.And finish to debug system initially.Study abroad in the magnetic flux leakage detection technology on the basis of the current situation and development trend.Analyse the method and system of drill pipe non-destruction test domestic and overseas. According to practicality of defection and demand of detection,confirm the system blue print that it applys magnetic flux leakage only.Research and design transverse defection detection equipment,include magnetization,calculation and distribution of coil magnetic field,the end effect,the blind district. A constant current circuit is designed to ensure the stability of magnetic field.Distinguish of between closed magnetization and unclosed magnetization is discussed.That the initial magnetic curve cann't be seen as a rule to select magnetic intensity is fowarded.Use ANSYS to simulate magnetic field,which be used to compare to theory value.The result proves that it is right that use ANSYS to simulate.Unclosed magnetic curve is be build by simulation data of different specification drill pipe,which be used a rule to select optimum magnetization region.After contrast to variety of signal transmission method,slip ring is be used as transmission medium,which connects defection signal of lenthwise detection equipment to outside. Able to complete the design of the multi-channel signal to the data acquisition system for data collection.Firstly,FPGA recognises the pulse that A/D sends to control multiplexer arrays to combination single signal.Secondly,on upper computer the single data is reverted to original signal according to synchronization signal. A novelty data acquisition method that can solve the problem that the number of input-channel data acquisition card meets the needs of large number of sensors is forwarded.Through field test, the drill pipe magnetic flux leakage detection system can detect drill pipe cracks, holes, corrosion and other defects. The system is operating well.