Research On Long-distance Pipeline Distributed Stress Monitoring And Health Diagnosis Method

Long-distance oil-gas pipeline,as the main artery and lifeline of national economic development,plays an important role in modern industry and daily life. How to prevent accident or failure and how to ensure the safety are an important and complicated research subject. From this reality, this paper carries out the research of long distance pipeline on BOTDA distributed stress monitoring technology and discusses real-time stress monitoring technology and life prediction method of long-distance pipeline. This paper mainly carries out the relevant research from the following several aspects:1) It introduced the basic principles of optical fiber sensing technology and distributed optical fiber sensing technology(BOTDR, BOTDA, OTDR and etc.). Combined with the long-distance characteristics of large scale, complex work environment and real-time monitoring requirement, it discussed the feasibility of pipe stress monitoring based on BOTDA. Through the analysis of pipeline accident at home and abroad in recent years, this paper summarized the main failure reasons and the main failure modes of long-distance pipeline. Also, it carries out the necessity research of on-line real-time stress monitoring of long-distance pipeline.2) This paper carries out the health diagnosis method research of the long-distance pipeline failure criterion. Through the analysis of the basic theory of pipe stress, the pipeline failure criterion based on stress is researched. Combining with the theory of fatigue life, the long-distance pipeline health diagnosis and life prediction method are studied. On the one hand, according to failure criterion of stress, the measured stress is compared with the yield stress of pipe material to determine whether the pipeline loses efficacy; on the other hand, in view of the hot spot stress, through continuous acquisition of the site of the stress, the rain flow count method is adopted to deal with stress- time history curve, and then according to the fatigue cumulative damage theory, the fatigue life of the entire pipeline is predicted.3) Taking pipe material with 45# steel, 6m length as experimental object, the distributed stress monitoring experiment research of pipeline is carried out based on BOTDA. And compared the experimental results and theoretical results on ANSYS, it is verified that based on brillouin distributed optical fiber sensing technology of pipeline stress monitoring method is feasible.4) Taking a light bracket pipeline bridge with a 50 m main-span in Sichuan province as an object, the distributed stress monitoring application research of long-distance pipeline is carried out based on BOTDA. It is further validated the distributed stress monitoring technology of long distance pipeline based on BOTDA and the health diagnosis method based on the stress monitoring. Meanwhile, the field application of the construction scheme(especially the method of laying optical fiber) is discussed.