Study On Source Character Of Acoustic Emission From The Bottom Of Atmospheric Metal Storage Tank

This paper was supported by China Special Equipment Inspection & Research Centre, and it was performed on the base of key project of'Study of Technology and Exploitation of Equipments for Big Storage Oil Tank'belonging to the ministry of science and technology. The research put emphases on Acoustic Emission Testing and Magnetic Flux Leakage Testing and tried to establish the series standard of the two methods above.The traditional testing, on-line testing and opening inspection are generally used for huge atmospheric storage tanks. Acoustic Emission testing is one major method of on-line testing, and its main task is to resolve three key problems of location, qualification and quantification. It means that to confirm the position of flaws, to analyze the reason caused flaws and to establish the standard of quantification for determining the serious degree of flaws.Combining basic experiments and engineering application, major objects were performed and discussed in this paper as follows:(1). Location speed under the different motivating style and the method of conforming location speed. The speeds are 1350m/s, 1150m/s and 1000m/s corresponding to the stone hitting, hammer hitting and lead breaking, and the principle of least LUCY value was conformed.(2). To study the difference between signals responding to different motivating manners as well as between signals come from the same origin, the different managing manners of wavelet transform, frequency analysis, pertinence analysis and characteristic coefficients of wavelet region for signal information were performed. The effort of trying to distinguish the signals motivated by different manners and to confirm the signal origin through the received information was made. It was indicated that the major frequency of signals for three different motivating manners concentrated between 20 and 50 KHz, the difference between wavelet coefficients was small, and the pertinence of the original signal and the returning signals was low.(3).The on-line testing results for No. t13 tank in Zhenhai Storage Company by using AE method was operated. According to the principle of least LUCY value, the location sound speeds for the tank above have been confirmed. On the other hand, pertinence analysis was made for location signal of Lucy values in accordance with changing sound speeds, in order go confirm the kinds of the signals. The results show that the location sound speeds for the tank above has been confirmed as 1.2～1.4m/ms and 3.2m/ms and the degree of the superposition of two Lucy value and sound speed curves correlated directly with the pertinence of the signal.(4).Introducing the Flux leakage examination and the comparison made between Magnetic Flux leakage examination and ultrasonic testing proved that Magnetic Flux leakage examination can be used...