Studying the causes and risk factors of vulnerability with SVA model and Resilience Engineering approach in National Iranian Gas Company about one of city gate stations

Background and purpose: Vulnerability introduces the sensitivity of a system versus internal faults or external threats. A vulnerable system cannot recover itself after shocks and may disable to provide services. I in this study in order to achieve a resilient city gate station (CGS), vulnerability of the system identified via SVA procedure. Moreover, using the resilience engineering approach safety level of a CGS  improved against Industrial crises. Methods: The present sectional descriptive analytical study was conducted in a CGS according to typical design of stations and during this study, sva procedure, forms and tables modified and prepared to evaluate vulnerability. In the next stage 6 phases; 1) Asset attractiveness determination. 2) Assets characterization determination. 3) Evaluate impacts of industrial crises. 4) Evaluate existing countermeasures. 5) Identify vulnerabilities and estimate degree of vulnerability. (Develop a target list of critical functions and assets for evaluate vulnerability.) 6) Identify new countermeasures and reduce risk level until archive acceptable risk, has been conducted Findings: According to the results of this study and score for attractiveness, Assets importance, crises and effectiveness of protection, vulnerability score was determined. Thus, two industrial crises (explosion / fire and gas pressure drop) was more important than other industrial crisis mentioned (regarding adverse effects on the station, the station neighbors and gas consumers). According to this study, the most important assets of CGS station were respectively Heater, valves, inlet and outlet and Turbine meter and the biggest threat were gas pressure drop and explosion / fire in the station .Finally, regarding to  the vulnerability scores, 15 solutions were presented to improve the safety level of CGS stations. Discussion & Conclusions: SVA modeling  to identify vulnerable areas as well as defining strategies for resilience of CGS station in the(1)  pre-crisis period (prediction, prevention and preparedness) 2-during the crisis (resistance, response) 3. After crisis (recovery and reconstruction, acquisition and development experience) distinguished as features of this study. Beside application of design criteria, agility of operators in quick repair and recovery of facilities repair also would be constructive to enhance the resilience of the system.