The Technology Of Pipeline Leakage Detection Based On Fiber Optic Acoustic Sensor

Pipeline transportation has many advantages such as safe, trouble-free, short-cut, low loss operation, and has become the main transporting facility for petroleum, natural gas and among others. But the pipeline transportation has also been in face of a serious challenge on safety due to the degradation of the pipeline, the manmade sabotage on the facilities and other reasons. Therefore, the study on the theory and methods of safe detection of the pipeline transportation is of great significance for maintaining the pipeline safety operation and reducing the waste of resources.According to the actual requirement of the pipeline safety detection, the application of the interferometric fiber optic acoustic sensor technology on the real time, inline, nondestructive pipeline detection has been studied, based on the saw-tooth frequency-modulated continuous wave (FMCW) technology. The main works are as following.Acoustic emission detection theory and negative pressure wave theory for the leakage-induced acoustic signal detection of the pipeline were discussed. The characteristic of the acoustic signal and its propagation properties of a leakage pipeline were experimentally studied with piezoelectric ceramic transducers installed on the pipeline, which will provide reference for the next detection works with fiber optic sensors.The saw-tooth FMCW interference theory was deeply discussed with Michelson interferometer. The saw-tooth FMCW interferometric fiber optic acoustic sensing principle was analyzed, and the corresponding digital demodulation method was achieved and simulated with MATLAB program. Two kinds of fiber optic sensor for the leakage-induced acoustic signal detection of the pipeline were designed at last.A kind of frequency division multiplexing (FDM) technology based on the saw-tooth FMCW principle was analyzed and simulated in computer. The signal-crosstalk among the multiplexing channels was calculated and some key parameters for the FDM system were achieved in simulation.The saw-tooth FMCW interferometric fiber optic acoustic sensing system and the corresponding FDM system were set up and demonstrated in experimental laboratory and in the outside field separately. The result of this paper will not only lay a good foundation for the subsequent development of the fiber-optic pipeline safety detection system, but also generalize some other important safety detection facilities in some significant areas.