RISK ASSESSMENT OF LIQUEFIED PETROLEUM GAS STORAGE FACILITY

Abstract

Storage tanks are very important for containing small to large volumes of flammable and hazardous chemicals at elevated temperature and pressure in chemical process industries. There are various organizations and engineering societies who published strict engineering guidelines and standards for the construction, material selection, design and safe management of storage tanks and their accessories. Even after following these standards and guidelines in the design, construction and operation, tank accidents do happen. By preventing equipment failure rate, the frequency of risk reduces but its impact is still high. Therefore, scope of risk assessment in the process industries widen to cover hazards related to workers and property in and near the plant. Liquefied Petroleum Gas (LPG) is very common fuel for domestic and industrial purpose. LPG storage tank has severe degree of hazard. A simple risk assessment method was used to find the risk associated with the three LPG storage tanks having 100 tonnes each of a LPG bottling plant. Fault tree analysis was used to identify the hazards and its frequency. Four main events were identified which can lead to fire and explosion: overfilling, overpressure, mal-operation and mechanical failure/damage which can further lead to open vapour cloud explosion and catastrophic failure of the tank. Impact of various accident scenarios (pool fire, fireball and vapour cloud explosion), was calculated in terms of individual risk to the society. It was found out that pool fire contributes less hazards to people but it can cause accident in the nearby equipment or property due to its thermal radiation. The largest contribution to the individual risk is due to vapour cloud explosion. Impact of worst case scenario was calculated and found that risk near 600 m from the LPG storage tank location was acceptable.