Study On Stress Wave's Properties Of Long Distance Pipeline

As one of the five major ways of transportation,pipeline transportation plays a much more important role in the economy construction and national defense industry. Keeping pipeline safety is an important work for the pipeline industry and safety management bureau. If the pipeline leakage happened, much money would be lost. More seriously, it maybe causes personal injury. Pipeline defects detection is a main work of safety inspection for long distance pipeline.Traditional detection methods use the detection after the trouble happened so the efficiency is not high. Meanwhile guided wave technique has some goog properties, such as high efficiency of detecting, less time needed and it can be used to inspect the whole wall thickness of pipeline, so it has been widely applied in non-destructive structure testing. This paper aimed at carrying out some basic theoretical research and experimental studies on the guided wave technology for the leakage detection of long distance pipeline. The low carbon seamless steel pipeline,whose inside diameter is 52mm and outside diameter is 60mm,is used to replace the long-distance pipeline in the simulation and experiment of this paper,because that its group velocity dispersion curves is similar with the long-distance pipeline's when the frequency below 20KHz.Firstly, the research statuses of the nondestructive testing technology of guided wave method at home and abroad in pipeline testing are analyzed.Secondly,the basic concepts of guided wave are introduced, and the hollow tube theory of guided waves is deduced, also the dispersion equation of the hollow cylindrical tube waveguide was derived, then the wave dispersion curve was obtained, at last the two kinds of results from hollow tube theory and plate theory are compared. Next, the nature of two most basic longitudinal guided wave mode ,L(0,1) guided wave mode and F(1,1) guided wave mode, in the hollow tube are analyzed,and the propagation characteristics of L(0,1) guided wave mode and F(1,1) guided wave mode in the situation of the integrity pipeline, the single defect pipeline and the double defects pipeline are studied by the method of the numerical simulation, then the extraction method of the two mode guided wave and its test method used in the pipeline defect detection are discussed, the algorithm of deficiency location are given. Combined the experimental modal analysis theory, the defects positioning of the single defect pipeline and the double defects based on F(1,1) guided wave mode come true by the experiment, and the test results affected by the defect size are qualitative studied. At last, the differences of simulation and experiment are compared and discussed, and the propagation characteristics of guided waves in the pipeline are summed up, then the inadequacies of the existing work are analyzed, and the recommendations for further work are given.Research paper shows that the method of guided wave techniques applying to the defect test and location is feasible. The way of guided wave mode excitation and the accurate extraction technology should be studied in the future work.