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Xie Y.,Research Institute of Beijing Labor Protection science | Wang T.,Research Institute of Beijing Labor Protection science | Lu L.,Research Institute of Beijing Labor Protection science | Bai Y.,Research Institute of Beijing Labor Protection science | And 2 more authors.
Natural Gas Industry | Year: 2015

For discovering pipeline gas leakage in time, determining the leakage locations quickly and accurately and discriminating the influencing range of leakage and diffusion, multiple full-scale leak tests were performed on middle-low pressure buried pipelines by using an experiment system which was designed and built by ourselves. The basic characteristics of convective diffusion of pipeline gas in soils were revealed and spatial distribution and change rules of its concentration fields were presented. It is shown that gas concentration distribution in soils is basically symmetrical on leakage points along horizontal direction, but asymmetrical along vertical direction at the early stage of leakage. This means that the contour of high concentration zones is initially in the shape of ellipse (long axis along the vertical direction) at the early stage of leakage, but presents irregular change as leakage goes on, and an obvious convex occurs right above the leakage point. The convex amplitude of high concentration zones induced by low-pressure leakage is larger and more significant than that induced by medium-pressure leakage. And the convex will gradually disappears with the continuous leakage of pipeline gas. It is approximate power exponent relation between the time period needed by gas concentration to reach the low explosion limit and the distance to leakage points. And with the rise of pipeline pressure and leakage rate, the characteristic curve of explosion limit-leakage time of methane in sols varies from the convex curve to the straight line, with the slope larger and larger. ©, 2015, Natural Gas Industry Journal Agency. All right reserved. Source

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