Effect of Pinhole Shape With Divergent Exit on （针孔与发散出口形状的影响）.pdfVIP

EFFECT OF PINHOLE SHAPE WITH DIVERGENT EXIT ON AE CHARACTERISTICS DURING GAS LEAK K. YOSHIDA, Y. AKEMATSU, K. SAKAMAKI and K. HORIKAWA Faculty of Engineering, The University of Tokushima 2-1 Minami-josanjima, Tokushima 770-8506, Japan Abstract AE technology has been applied to gas leak detection and inspection. However, it is difficult to detect and inspect the gas leak consistently because measured AE waveforms are different from leak pressures and shapes of leak parts. In this report effects of the stepwise and straightforward pinholes on AE characteristics during gas leaking were discussed. When the pressure reached to about 0.11 MPa in the case of the stepwise pinholes, AE amplitude tends to go up and down, the peak at about 150 kHz was observed. It was found to be easy to detect gas leak from the stepwise pinholes, as compared with the straightforward pinholes. Key Words: Gas leak; AE waveforms; FFT 1. Introduction The leak detection for piping faces many challenges. Problems mainly consist of the necessity of many processes for the inspection and difficulty to inspect a gas pipe placed under ground. Acoustic emission monitoring as one of the well-established nondestructive technologies may be put to practical use in future for the leak detection technology. However, the method has not been used widely to monitor the gas leak from pipes. Even if there is no defect before operation or some defects are too small to detect during inspection, various defects occur or develop under operation because of temperature, pressure, and environmental condition and become so large that these cannot be neglected. In recent work, it was reported that the characteristic frequency of AE due to gas leak was 10 kHz [1]. However, there are no reports on AE source