Fishbone diagram and risk matrix analysis method and its application in safety assessment of natural gas spherical tank

Abstract Gas spherical tank leak can cause a serious fire and explosion accident, resulting in huge economic losses and posing a huge threat to social security. By combining improved fishbone diagram and risk matrix model, we studied a comprehensive risk assessment method. Quantitatively calculate the probability of occurrence: Firstly, we established a fishbone diagram model to analyze the causes of all spherical tank leakage events. Then the experts would rank causes of the incident in language description, next we assigned weights to these experts’ competencies by Entropy–Analytic Hierarchy Process, so we could turn the language description into fuzzy probability value using fuzzy mathematic theory. Finally, we calculated the occurrence probability of the Resultant events by Fault tree model. Quantitatively calculate the probability of consequence: From casualties, economic losses and environmental damage to consider the total loss caused by the leak accident, and combining with the probability of occurrence to calculate the consequences losses quantitatively. After modifying classical risk matrix, we analyzed the spherical tank leak level with considering occurrence probability and sequence severity. At the same time, we proposed specific measures for reason accidents which have greater occurrence probability to eliminate or reduce the risk of consequences.