Research On The Technology Of Complex Pipeline Leakage Detection

As an indispensable transportation instrument, pipeline is playing a more and more important role in today's national economy. Leakage is one of common pipeline accidents, which causes not only a large amount of material losses in the pipeline and environmental pollutions but also casualties. Therefore, accurately detecting and locating of pipeline leakage has become an important problem need to be solved in modern industry.Choosing the leakage detection of complex pipeline as study object, this dissertation focused on studying the composition mechanism of pipeline leakage signals, the development of pipeline leakage detection system, the attenuation coefficient of negative pressure wave and leakage detection of normal bend pipelines, the leakage detection of complex layout pipelines and the evaluation and comparison between complex pipeline leakage detection system and straight pipeline leakage detection system. The main research works of this dissertation are as follows:The first chapter introduced various methods of pipeline leakage detection, elaborated the domestic and foreign development status of the pipeline leakage detection, proposed the existed questions and development tendency, and finally described the research contents of this paper.The numerical calculation on the process of pipeline leakage was discussed in the second chapter. It first proposed the basic equation of transient flow, described the solving process of the finite difference method based on characteristic curves, and illustrated the handling of friction items. Then, a new approach of handling boundary condition at leakage points was proposed and the boundary conditions at the two ends were introduced. Finally, the numerical calculation of pipeline leakage was carried out by a case study. The pressure at the two ends and flow variation were obtained when the leakage occurred, which provided a theoretical basis for distinguishing leakage.The development program of experiment table of pipeline leakage detection system is given in the third chapter; By choosing appropriate experiment hardware, denoising plan of the negative pressure wave signals and the plan of detecting mutation points from negative pressure waves, the experiment table used in this dissertation is built by developing upper computer system interface using the Labview programming.The fourth chapter researched the leakage detection for normal bend pipelines. According to the rule that the energy of negative pressure wave exponentially attenuate through a pipeline, the attenuation coefficient of negative pressure wave was studied, and the influences of different leakage rate, different leakage point, and different pressure at the first node on the attenuation coefficient of negative pressure wave were analyzed. Consequently, an appropriate leakage point was selected as the basis of leakage detection for normal bend pipelines. Finally, the experience conversion formula of equivalent length of leakage detection for 90°bend pipelines was derived.In the fifth chapter, the leakage detection of complex layout pipelines was studied. Due to strong self-adaption and self-learning ability, the BP neural network was selected as research foundation for the leakage detection of complex layout pipelines. By choosing feature vectors which can describe the characteristics of negative pressure wave signals as input of the neural network and choosing the expectations after normalized as output of the neural network, the leakage detection and location of complex layout pipelines was studied based on appropriately determining the number of hidden nodes of the BP neural network.The sixth chapter evaluated the pipeline leakage detection system. It selected reasonable layered evaluation indexes and analyzed the weights of evaluation targets. Then the membership grade of each evaluation target is determined. Finally, the three different pipeline leakage systems introduced in this dissertation were evaluated with Fuzzy comprehensive evaluation in order to attained their advantages and disadvantages in the evaluation of complex pipeline leakage detection.Chapter 7 summarized the whole dissertation and proposed the further study works.