This paper proposes an approach to analyse the reliability of a city gate station. The city gate stations regulate the pressure of natural gas, transmitted by pipelines, to be adapted for distributing by the gas delivery network. In this approach contributory and main components of the station have been distinguished. Failure of the main components results in inconvenience or risk, directly; however, failure of contributory components increases the probability of failure in the main components. Fault Tree analysis is used to calculate the probability of occurrence of susceptible situations, resulted by failure of contributory components. The results are used by event tree analysis to calculate the final risk. The proposed method provides a simple approach that can be used to analyse risk in chemical and petrochemical field.
