Study On Key Technique Of Crude Oil Transport Pipeline Leak Detection

The leakage accidents in pipelines transportation not only cause great loss of material, but also pollute the environment; what's more, it may lead to serious casualty. Leakage accidents in pipeline transportation occur frequently in recent years. In order to guarantee the pipelines work safely and minimize the losses caused by leakage accidents, it is necessary to study leakage detecting technology to raise the sensitivity of detection and accuracy of localization. Pipeline leakage detection is a multi-field object, which involved many subjects, such as pipeline hydrodynamics, thermodynamics, sensor technology, subtle signal detection and signal processing. The research on pipeline leakage detection and localization is carried out in this dissertation. The main efforts accomplished can be summed up as the following aspects:1. Two crucial technologies in instantaneous negative pressure wave method are analyzed in this dissertation, then a means is presented which can eliminate the dynamic response time diversity between pressure sensors in the beginning and end of the pipeline, by adopting GPS to unify the system time between data collecting systems in two ends. The velocity change of instantaneous negative pressure wave along the pipeline is analyzed when hot oil is transported. Two searching methods are applied to locate leakage through numerical integral.2. Taking account of the corresponding characteristic of the signal singularity and wavelet transform module maximum in multi-scale changing, the discrete wavelet transform is applied to get the featured inflection point of negative pressure wave. The data extension methods of discrete wavelet transform calculation is studied. Two algorithms of locating the singularity accurately are put forwarded. 3. As for the problems in leakage detection introduced by the transport method adopted in China long crude oil transported pipeline, wavelet thresholding and median filter are used to denoise depending on field experimentations, and the effect is satisfactory. A scheme of leak detection and localization is presented, which is used during pipeline transportion cease.4. "Energy-fault recognition", a fault diagnosis method based on wavelet packets analysis for the transport pipeline supervising system is proposed in this dissertation. Eigenvector target is presented which reflect the characteristic of leakage pressure signal. The signal is wavelet packets decomposed in this method. By analyzing the new sequences reconstructed on every decomposition note, the fault then can be recognized according to the eigenvectors in each frequency band.5. The method of characteristic used to pipeline leak instantaneous change numeric solution and ascertainment of boundary conditions are analyzed in this dissertation. Instantaneous change calculation imitation program is used to analyze the curves which response pressure and flux parameter of pipeline changing with time and distance after leak. It has directing meaning to leak detection and localization.6. A station-independent leak supervising and localization system for crude oil concentrated transport pipeline and distributed master-slave leak real-time supervising system for long distance transport pipeline are designed with virtual instruments technology. The accuracy of the method and the reliability of the system have beenvalidated through long time run of these two systems fixed on the field.