Explosion risk analysis on Town Border Stations of natural gas using Failure Mode & Effect Analysis and Fault Tree Analyses methods

Background and aims: Attention to safety of process plants adjacent to residential area, especially in the big cities is extremely important from perspective of safety engineering and risk management. This study was carried out with the aims of identification of hazard points of explosion in Town Border Station (TBS) and qualitative and quantitative analysis of their occurrence causes and estimation of leak probability in this station. Methods: Hazard points of the explosion and qualitative analysis of the failures conducted by means of Failure Mode and Effect Analysis (FMEA) method. Occurrence probability of related accidents was estimated by means of Fault Tree Analysis (FTA) method. To determine of the basic event occurrence probability of FTA, we used the expert opinions and the related data banks. Results: Hazard points of identified explosion in the TBS stations were ten. A total of 67 failures in gas leak of the Sensing that had highest Risk Priority Number (RPN= 24) were identified. Also Earth system of the station had the lowest RPN= 4. The results showed that the leak probability of the sensing was equal to 0.52 per year. Process failure (FP= 0.334) and mechanical failure had the highest and the lowest failure probability of the sensing gas leakage. Conclusion: Prevention and control of the sensing gas leak and the prevention of both of the occurrence process failures and unsafe behavioral had considerable importance in the explosion risk reduction of TBS.