Determining the safe distance of CGS (city gas station) and TBS (town boarder station) pressure reduction stations using PHAST software

Abstract

Background and Purpose: The demand for petrochemical products is increasing every moment. Most of these materials are flammable and explosive or toxic. In general, improper operation in the cycle of production, consumption or storage of raw materials and petrochemical products causes the leakage of hazardous substances on a large scale, which may lead to accidents with catastrophic consequences. Determining the safe distance and the extent of damage and the radius affected by these accidents play a fundamental role in reducing the rate of the consequences of these accidents, as well as determining the scenarios that cause accidents and the process of their occurrence in advancing the goals, identifying and controlling the risks of these scenarios in process industries are of particular importance, also the main purpose of this thesis is Determining the safe distance of CGS (city gas station) and TBS (town boarder station) pressure reduction stations using PHAST software. Materials and Methods: This study is of an applied and descriptive-analytical type. All information about the types of gas pressure reduction stations in Tabriz city for a period of one year was collected and analyzed from the relevant organizations and offices, including the National Gas Company. Additional information was collected through correspondence, face-to-face interviews with officials of Tabriz City Gas Company. In order to model the result and determine the safe space in the pressure reduction stations, the Total GS EP SAF 253 standard was used, and to implement this standard, the collected data was entered into the PHAST software. This software models incidents such as fire and explosion of tanks and pipes and displays the range of influence graphically. According to this standard, consequence modeling and safe privacy were defined in three areas: Fire Zone, Restricted Area, and Impacted Area. In this division, factors such as radiation level and overpressure are decisive. Also, based on this standard, specific scenarios are defined for all three areas. And after implementing these items in the software, the distances related to the desired safe spaces were determined. The report of these intervals and the analysis of the results were also presented. Result: The results indicate that the distance related to the fire zone in CGS stations based on the maximum pressure of 1000Psi is equal to 81 meters related to the explosion in 5D weather conditions. The distance of the Restricted Area was 529 meters and the distance of the Impacted area was 649 meters. In TBS stations, the distance of 24 meters related to explosion and weather is considered as the safe distance for the fire zone at 250 Psi pressure. This distance was 282 meters for the Restricted Area and 338 meters for the Impacted Area, which is the attention and observance of the mentioned distances especially in the design stage of the stations and the application of the things mentioned in connection with the triple boundaries in The Total GS EP SAF 253 standard can significantly reduce the severity of consequences of possible accidents in gas pressure reduction Total GS EP SAF 253 standard was used, and to implement this standard, the collected data was entered into the PHAST software. This software models incidents such as fire and explosion of tanks and pipes and displays the range of influence graphically. According to this standard, consequence modeling and safe privacy were defined in three areas: Fire Zone, Restricted Area, and Impacted Area. In this division, factors such as radiation level and overpressure are decisive. Also, based on this standard, specific scenarios are defined for all three areas. And after implementing these items in the software, the distances related to the desired safe spaces were determined. The report of these intervals and the analysis of the results were also presented. Result: The results indicate that the distance related to the fire zone in CGS stations based on the maximum pressure of 1000Psi is equal to 81 meters related to the explosion in 5D weather conditions. The distance of the Restricted Area was 529 meters and the distance of the Impacted area was 649 meters. In TBS stations, the distance of 24 meters related to explosion and weather is considered as the safe distance for the fire zone at 250 Psi pressure. This distance was 282 meters for the Restricted Area and 338 meters for the Impacted Area, which is the attention and observance of the mentioned distances especially in the design stage of the stations and the application of the things mentioned in connection with the triple boundaries in The Total GS EP SAF 253 standard can significantly reduce the severity of consequences of possible accidents in gas pressure reduction stations. Conclusion: Based on this study, it was found that in most of the investigated stations, the distances related to the triple boundaries were not observed and this issue can have a direct effect on increasing the severity of possible process accidents. Also, TBS station in Golgasht is more important than other stations due to its special geographical location, which is located in a busy environment, which makes managers and workers in the Gas Company should pay special attention to increasing the safety factor and reducing the severity of consequences of possible accidents in this station. In the two investigated CGS stations, there is a possibility that the consequences of the Fire Zones affect each other due to the fact that two pressure reduction units are active in parallel and adjacent to each other. Restricted areas, which define the boundary of the site with the outside space, are not considered in these stations, and the consequences of accidents related to this boundary go beyond the walling of the station. It was also found that in the Impacted Areas, which represent the privacy outside the site, around all the stations, the buildings and road construction are observed inside this privacy, which is contrary to the definition of the privacy of the Impacted areas.