腐蚀作用下城市埋地燃气管道的失效概率分析

失效概率确定是管道定量风险评价的核心内容。为此,针对城市燃气输配管道特点,通过建立管道失效概率模型,利用可靠性理论得出了腐蚀作用下城市埋地燃气管道失效概率随服役年限的变化情况,并对影响管道失效概率的随机参数进行了分析。结果表明:在管道投入运行初期,腐蚀对管道失效概率的影响较小,其余参数的相对影响随工作压力大小而变化,当工作压力小于2.5 MPa时,竖直荷载是影响城市埋地燃气管道失效概率的最主要因素;随着工作压力的增加,竖直荷载影响失效概率的重要性逐渐下降,材料屈服强度、管道壁厚的重要性逐渐增加,而工作压力的重要性显著增加;当工作压力达到4.0 MPa时,对管道失效概率影响较大的因素为材料屈服强度、工作压力、竖直荷载和管道壁厚等;随着管道服役年限的增加,腐蚀对失效概率的影响增大并逐渐占据主导地位,在管道运行后期,影响管道失效概率的主要参数是腐蚀指数、腐蚀乘子和工作压力。

Analysis of failure probability of urban underground gas pipelines under corrosion effect

Failure probability determination is the core of quantitative risk assessment on pipelines. In this study, a model for failure probability of pipelines was constructed considering the specific features of gas transmission and distribution pipeline networks in urban areas. The model was used to determine the changes of failure probability of urban underground gas pipelines with its service life under corrosion effect by using reliability theory. In addition, random parameters that may affect the failure probability of pipelines were analyzed. The results show that corrosion may present minor impacts on the failure probability of pipelines in early stages of operation, whereas impacts of other parameters may vary in accordance with operation pressures. Under operation pressures below 2.5 MPa, vertical loads are the most important contributor to the failure probability of urban underground gas pipelines. With the increase of operation pressures, the impact of vertical loads on failure probability may decrease gradually, whereas that of yield strength of materials and wall thicknesses of the pipeline may increase steadily. When operation pressure reaches 4.0 MPa, factors that may present significant impacts on the failure probability of pipelines include yield strength of materials, operation pressures, vertical loads and wall thickness of the pipelines. Over the service life of the pipelines, impacts of corrosion on failure probability may increase gradually and eventually play a dominant role. In later operation stages, major factors that may impact the failure probability of pipelines include corrosion index, corrosion multiplier and operation pressure.