Journal of Applied Sciences1812-56541812-5662Asian Network for Scientific Information10.3923/jas.2014.955.959YouQiujuFanJianchunZhuWeiBaiYongqiang92014149In order to realize more objective quantitative risk assessment of natural gas pipeline network systems, this study presents a model for risk assessment of natural gas pipelines based on the engineering fuzzy mathematical theory. The model can more accurately calculate the risk value of sections and network of pipeline and quantitatively determine the risk hierarchy. Regarding the risk hierarchy, the clear and consistent risk measurements are taken. The study thoroughly analyzes the possible factors causing pipeline network accidents by using fuzzy mathematical theory. By determining factor set, assessment grade set, factor weight set, factor assessment matrix, fuzzy comprehensive assessment, assessment index treatment and the like, a fuzzy comprehensive assessment system for the safety of urban gas network is established. Finally an application is provided in a real case so that the effectiveness of the assessment model could be verified.]]>Cagno, E., F. Caron, M. Mancini and F. Ruggeri,2000Chen, L.Q., P. Zhang and J.L. Ma,2003Henselwood, F. and G. Phillips,2006Jo, Y.D. and B.J. Ahn,2005Muhlbauer, W.K.,1996Wang, L. and F. Li,2005Wang, X.M.,2006Xiao, C.Y.,2004You, Q. and W. Zhu,2009You, Q., J. Fan and W. Zhu,2011Young, D.J. and A.C. Daniel,2008Yu, S.R.,2005Zhang, Y., F. Li and Y.W. Guan,2006