Study On Methodology Of Risk Assessment For Natural Gas Pipeline Network

Recently natural gas industry is developing rapidly, and its accidents are threatening the urban safety. Risk management through quantitative assessment has become an important way to improve the safety performance of the natural gas supply system. This paper focuses on the risk of urban natural gas pipelines, and assesses risk by qualitative analysis and quantitative evaluation.In this paper, a qualitative as well as an integrated quantitative risk assessment methods for urban natural gas pipeline network are proposed. The qualitative method is an improvement to the Kent Grading method which is manly used for the long-distance pipeline, and has three primary indexes as inherent risk index, causation index and consequence index. The causation index displays the factors induce the natural gas pipelines accidents, the inherent risk index displays the vulnerability of natural gas pipelines, and the consequence index displays the consequence of natural gas pipelines accidents. The selection of indexes is according to the character of gas pipeline accidents, and the distribution of weights is based on the Reliability Engineering Theory and the Grey Correlation Theory.The integrated quantitative risk analysis method for natural gas pipeline network proposed is composed of the probability assessment of accidents, the analysis of consequences and the evaluation of risk. This new method consists of different accident effect analysis and physics model analysis, including release rate calculation, physics effects calculation, death probability calculation, risk calculation, etc. The models that are possibly needed in urban gas transmission pipelines risk are investigated.It is noteworthy that the consequences analyzed here include those of the outside and inside gas pipelines. The analysis of consequences of the outside pipelines focuses on the individual risk and societal risk caused by different accidents, while that of the inside pipelines concerns about the risk of the economic loss because of the pressure re-distribution.To demonstrate the presented methods, a small sample urban natural gas pipeline network including 95 pipelines and a large sample urban natural gas pipeline network including 5421 pipelines are used for risk assessment. The results show that both of two presented risk assessment methods for natural gas pipeline network can be used in practical application, and the choice of methods depends on the actual basic data of the gas pipelines and the requirement of assessment accuracy.