Risk Assessment of Releasing Flammable Material from Liquefied Petroleum Gas Tanks by Bowtie Method and Vulnerability Zoning by PHAST Software

Abstract

Introduction: The release of storage tanks' contents can lead to consequences such as BLEVE, explosions, fires, etc. Therefore, identifying the causes of content release, determining the scenarios, consequences, and possibility of incidents are required to prevent possible accidents. Moreover, the vulnerability and safety ranges should be determined to minimize the losses.

Methods: In this research, the Bowtie method was used to evaluate the risk caused by the pressurized reservoirs. After identifying the risks of process hazards and determining the main, middle, and base events, the fault tree was mapped. Then, the events probability was calculated. In the next step, the event tree was designed to determine different scenarios of events and identify the consequences of each incident. Later, the probability of consequences was calculated. The Bowtie diagram was designed in the next step. Finally, the vulnerability zone was determined for each of the consequences using the PHAST software.

Results: Considering the Bowtie's analysis, a total of 27 events including 21 base events, six mid events were determined. Furthermore, 15 minimal counts along with their event probabilities and importance were identified. In this regard, nine outcomes and scenarios were determined along with their probabilities. The widest human vulnerability zone was related to cloud and steam explosions.

Conclusion: Leakage from the reservoir and connections, overflow, and PRVs are among the important defects of liquefied petroleum gas reservoirs. Considering the high probability of consequences and in order to prevent from the severity and damages of accidents, systems such as cooling system and fire stop system are required in the unit.