Risk evaluation for urban gas fuel net-work system based on fuzzy comprehensive evaluation

Urban gas fuel net-work system is a potential hazardous source. People and properties around the system are subject to the risk. In recent years, a great deal of efforts has been dedicated to accidents prevention. Most common accidents such as toxic emissions, fires and explosions must be avoided. The risk analysis technique is used to prevent these undesired events. For the sophistication of urban gas fuel net-work system, the objective difficulties and limitations of the existed assessment methods, it was proposed to combine the two methods of causal diagram and fuzzy comprehensive evaluation to analyze its risk. The factors influencing the safety level of urban gas fuel net-work system failure could be determined by causal diagram, they were urban transmission system, risk prevention measures and safety management which were influenced by their own sub-factors listed in this paper. Considering the uncertainties of these factors, the analytic hierarchy process was used as elicitation method of expert opinion to determine the weight of those factors. Linguistic judgment scale was referred to a numerical scale (Saaty's proposal) and the numerical judgment from experts could be reported in a single matrix of pairwise comparisons. The risk quantification then could be processed by the method of fuzzy comprehensive evaluation,and a scientific and reasonable model of risk analysis was set up. Based on the weight of each factor from the matrix and the fuzzy comprehensive evaluation, we could get the risk level of urban gas fuel net-work system. The new analytical steps were listed by taking an example, the result shows that the risk of the urban gas fuel net-work system in a city is low and the combination method of causal diagram and fussy comprehensive evaluation is of advantage and can be applied in engineering. It may be useful for risk management and pipeline planning.