Research Of The Detection Method On Pipeline Based On Electromagnetic Ultrasonic Phased Array

Oil and gas pipeline as the main carrier of the oil, natural gas and other energy sources, its safe operation ensures the safe transportation and full use of oil, natural gas, but also the protection of people’s lives. Due to the natural gas, oil station pipeline and other outdoor oil gas pipeline long-term exposed in the air, moist air, internal electrolyte material corrosion and transportation of oil and natural gas contains elemental sulfur and other corrosive elements, the pipeline also has certain corrosion, leading to frequent occurrence of pipeline accidents caused by corrosion, cracks or deformation defects such as, for the safe operation of the protection of oil and gas pipeline must be a full range of pipeline and effective inspection to ensure that the energy transmission. Ultrasonic phased array technology has become a new technology in the field of traditional ultrasonic nondestructive testing, by virtue of the advantages of no moving probe, flexible and effective control of ultrasonic beam deflection, focusing, large range scanning and so on.This paper researched the theoretical and experimental of electromagnetic ultrasonic phased array inspection technology, by combining electromagnetic acoustic transducers working principle and ultrasonic phased array inspection technology, the study on the electromagnetic ultrasonic transducer in ferromagnetic materials can change the theory of mechanism and ultrasonic phased array, including the principle of phased array ultrasonic beam deflecting and focusing, the theoretical derivation of the delay rule of ultrasonic phased array focusing and deflection calculation formula. The mathematical model of electromagnetic field, mechanical field and ultrasonic field is derived by mathematical modeling, and the mathematical model of EMAT is established under different energy transfer mechanism and the related formulas are deduced. By the use of acoustic theory- the Helmholtz Kirchhoff integral theorem established a single rectangular array, rectangular array element linear array under different beam steering and focusing sound field space mathematical model, for the array of the EMAT design provides the sound field distribution and design basis. Based on, in linear type winding coil based design with the arc coil EMAT, in the steel were experimental study, results show that linear type winding coil directivity better, ultrasonic energy is relatively concentrated. The experimental platform is built, the pipeline is tested by the electromagnetic ultrasonic array transducer, the echo signal is focused on the specified position, and the amplitude of the echo signal is enhanced.Research shows that: based on the conventional electromagnetic ultrasonic transducer, by comparing the theoretical research and experiment design of double array EMAT transducer electromagnetic ultrasonic array, determine the type and size of the excitation coil, the magnet structure, and in the tube the experimental results show that the ultrasonic phased array based on EMAT array compared to the traditional single element EMAT can effectively improve the conversion efficiency of the transducer, the precise control of time delay, can make the coherent superposition of waves, focusing on the flaws, by contrast the amplitude of echo signal, with the variety of the number of array element and delay time, echo signal amplitude increases to two times of the original, effectively solve the engineering pipeline defect detection accuracy, laid the theoretical foundation for the future of electromagnetic ultrasonic detection in the pipeline.