Study On Safety Assessment And Protective Measures For Suspended Sections Of Gas Pipelines Passing Through Waters

In recent years, along with the rapid growth of natural gas demand, the construction of gas pipelines is also increasing year by year. The gas transmission pipelines cross through complicated terrain, especially water areas, because of the long distance. Security circumstances of suspended pipelines are severly concerned by country and society. Compared with buried gas transmission pipelines, the suspended pipeline is in harsh conditions because of water flushing action. Therefore, the safety assessment of suspended section of underwater gas pipeline is needed to ensure safe operation of gas pipeline.Based on the formation mechanism of suspended section of underwater gas pipeline, the mechanical model of suspended pipeline is established. The influence factors of affecting the pipe stress are recognized by mechanical analysis of pipeline.In order to further analysis of suspended pipeline under current, ANSYS Workbench is used to simulate the suspended pipeline stress and deformation under current. Relevant change rules of stress and deformation are obtained. According to the stress and deformation results of simulation calculation, the failure of suspended pipeline failure is judged based on the stress and strain theory of pipeline failure criterion.According to the simulated results, the degree of influence on pipeline stress is analyzed by the single factor method. The sensitivity coefficient of each influence factor is calculated which indicates the affection to stress from the various uncertain factors. The sensitivity coefficient is helpful to determine the allow degree of changes in influence factors and the key factors of suspended pipeline is identified.Based on the pipeline vulnerability theory and the sensitivity analysis of pipeline stress, the safety evaluation index system of suspended section of underwater pipeline is established. The analytic network process (ANP) method and entropy weight method are adopted to determine the subjective weight value of indexes. Vulnerability of pipeline system is categorized through the method of triangle. The security level of suspended pipeline and the type of pipeline vulnerability is identified through the vulnerability assessment score.In order to guarantee the safe operation of pipeline, the protective measures of suspended section are discussed. Different measures are analyzed on stress analysis of pipelines. The results provide theoretical basis for daily maintenance and emergency measures of pipeline.