Advances in leak detection and location based on acoustic wave for gas pipelines

Abstract

With the rapid development of pipeline industry, the leakages of gas pipelines cause great energy waste and environmental pollution, especially security problems. Therefore, it is significant to study leak detection and location methods. At present, many leak detection methods have been developed for gas pipeline leakages, such as methods based on mass/volume balance, negative pressure wave, transient model, distributed optical fiber and acoustic waves, etc. Among them the traditional negative pressure wave method detects leakages based on the change of the absolute pressure in pipeline monitored by the pressure transmitter, while the acoustic method is based on the dynamic pressure monitored by the acoustic sensors. All evaluation indexes are considered as equivalent references, and after comparative analysis it can be known that acoustic method is promising and actual. And nowadays in this field, acoustic method is one of the hot issues. The acoustic method can perform full-scale display of pressure fluctuations caused by the leakages. The fundamental principle of the acoustic leak detection technology for natural gas pipelines is that an acoustic pressure perturbation is generated when leakage occurs. It transmits through gas to both ends of the pipeline and is acquired by the dynamic pressure sensors installed to the pipeline, which will be signal-processed by computer to determine whether leakage occurs or not. The amplitude of dynamic pressure wave is large and it contains a wide frequency range. The leak location technology based on dynamic pressure waves is one of the most potential methods in the future. The generation and attenuation of the dynamic pressure waves are the key points which determine the detection accuracy and the location precision. The leak-acoustics generation mechanism influences the leak-acoustics characteristics and signal recognition. The main reason of leak-acoustics generation for natural gas pipelines is the sonic source fluctuations. The propagation characteristics of leakage acoustic waves in gas pipelines are necessary to study.The accuracy of the velocity and the time difference restricts the application of the acoustic leak detection and location method. Then the location method is proposed which is based on the propagation model and takes no account of the velocity and the time difference. This dissertation consists of the following three parts which contribute to make the research status and future development clear: the fundamentals of the acoustic method, the related researches of recent five years (domestic and overseas) and the outlook of the leak monitoring based on acoustic wave method of gas pipelines, especially the analyses about the researches on acoustic leak detection and location method. The conclusions can be concluded that acoustic leak detection method is an important way to protect pipelines from failure and to decrease the risks which can be executed timely and accurately.