Study On Stress Wave Detection Technology For Gas Pipeline Leakage Based On Optical Fiber Sensor

As one of the five major transport ways，pipeline plays a much more important rolein the economy construction and people’s living. To keep pipeline safety and preventaccident has become an important work for the pipeline industry and safety managementbureau. Once the pipeline leakage happens, it will cause not only a lot of waste ofresources, but also serious environmental pollution, even danger to life safety. Pipelineleakage detection is an important work of safety running for long distance pipeline. Mostof the detection methods at present are indirect methods, and far from meeting therequirements in terms of detection efficiency, speed and positioning accuracy. Meanwhile,as a new detection technique owning the advantages in the above aspects, guided wavetechnique has been more and more recognized and widely applied in the detection ofstructures. In this paper, to achieve rapid and accurate detection of pipeline leakageinformation, the mechanism of acoustic emission and the guided wave techniques inlong-distance gas pipeline leak detection are studied, with the optical fiber sensorcollecting and processing the waveguide.This paper will focus on the following works.Firstly, the research statuses of the nondestructive testing technology of guided wavemethod at home and abroad in pipeline testing are analyzed, and optical fiber sensortechniques in pipeline leak detection are introduced.Secondly, the sound field and stress waves caused by gas pipeline leaking areanalyzed. A pipeline model at diameter of 273mm, thickness of 7mm is simulated. Thesound intensity, stress intensity and axial displacement at different internal pressure andleak aperture are analyzed.Thirdly, the concept of guided wave is introduced, the guided wave theory of thehollow circular pipe is derived, the guided wave dispersion equation of the hollow circularpipe is obtained, and the dispersion curve is given. Then the simulation of the L(0,1) modeguided wave propagation characteristics in the pipeline are studied.Finally, the stress and strain on the optical fiber modulation mechanism is analyzed. A pipeline leakage detection optical fiber sensor based on Mach-Zehnder fiberinterferometer is selected. The method that using PZT to eliminate the phase drift causedby changes in ambient temperature is raised, and the influence of polarized light on thestrength of the interference signal is reduced by the polarization controller. Thus theMach-Zehnder optical fiber interferometer sensor is improved theoretically.