Technique Research Of Leak Detection In Oil Pipelines Based On Induced Response

The pipeline transportation has become one of the five great conveyance means in national economy, which are railway, highway, air parcel and water carriage. The more of the pipe and the longer of pipe life span, construction blemish, corrosion perforation, abrupt nature disaster and sabotage, all the above factors may result in pipeline leakage. The leakage will bring enormous threat on people's life, property and the living environment. To ensure the safety of pipeline and minimize the losses caused by leakage accidents, it is significant to study leakage-detecting technology of higher reliability and veracity. This study employed a wide combination of various existed techniques including hydrodynamics, fluid network theories, computing methods of flow transients, wavelet theories and signal processing technique. Utilizing these tools, the leak-detection technique in pipelines based on induced response is put forward, and the theories and techniques relating with induced response technology are studied. The main research contents are as follows:1. The development of leak detection technology in pipeline is summarized, and the purpose and significance of the thesis are described. Various numerical calculating methods of pipeline hydrodynamics are outlined, and mathematic model and uniform mathematic expression are deduced.2. The induced response method that the portion of the valve is closed rapidly to induce the fluctuation of fluid in pipeline so as to detect the leakage of pipeline in light of induced pressure signal is put forward. The traveling wave method is used in time domain and negative pressure wave is defined. The expression of negative pressure wave reflectance is deduced and simplified, so the information of certain leaking points (leak location and leak size) in pipeline is obtained from this expression.3. According to induced response method, the expression in frequency domain of pressure response at the end of pipeline is derived using impulse response method and convolution theorem. The expression indicates that that transfer function is only related to the characteristics of pipeline system and the Fourier transform of flow variable only depends on the operating characteristics, and the pressure response in frequency domain is linear with the Fourier transform of flow variable. Information of the leak point (leak location) in pipeline is obtained from this expression.4. Using the localizing characteristics of wavelet transform in time and frequency domain, the pressure signal is decomposed and de-noised. Maximum point of the wavelet transform module corresponds to the signal singularity, so the arriving time of negative pressure wave is acquired accurately, and then the leak location is determined.5. The overall constitution and function of oil pipeline leak detection system are studied. The project of applying Matlab Web Serve to resolve the problem of remote monitoring, analysis, diagnosing is put forward. Oil pipeline leak detection system has been developed based on Matlab Web Serve. Such functions as remote data transmitting, data analyzing, leak detecting, result exporting on web are realized in this system.The experiment of analogous pipeline system was carried out, the results showed that induced response method is feasible and accurate.