A comprehensive risk evaluation method for natural gas pipelines by combining a risk matrix with a bow-tie model

Leakage from natural gas pipelines causes severe economic loss and significantly affects social security considering the gas' combustibility and the difficulties in detecting leakage. This study proposes a comprehensive risk evaluation method by combining a risk matrix with a bow-tie model. First, a bow-tie model is built, considering the risk factors that may lead to an accident using a fault tree; the consequences of unwanted events are then described in an event tree. Second, a fuzzy method is used to calculate the failure probabilities. Third, the severity of an accident is evaluated through an index system that includes personal casualties, economic losses and environmental disruptions. Finally, a risk matrix consisting of a probability ranking criterion and a consequence ranking criterion is proposed to reach an integrated quantitative conclusion of a bow-tie model. A case study of an underwater pipeline carrying natural gas has been investigated to validate the utility of the proposed method.