This paper contains an analytical examination of risk to human life beyond the boundaries of a hypothetical plant site, labeled the XYZ Plant, which stores and handles liquefied petroleum gas (LPG). The focus is the integration of available risk assessment research and techniques into a structured decision support tool. Procedures presented in this paper can be applied to a wide array of hazardous storage versus off-site risk exposure projects.
Quantitative risk assessment procedures are applied in determining fire and explosion effect zones and fatality probabilities in the area directly north of the XYZ Plant. The risk is assessed assuming that all four 113 562 L LPG tanks are updated with specified high reliability emergency shutdown systems and fire protection systems.
Event tree methodology is used in developing the fire and explosion scenarios which could result from the accidental release of LPG from containment.
Risk assessment tasks include the selection of significant LPG failure modes, calculation of release rates, and consequence modeling of human fatality effect zones. Boiling liquid expanding vapor explosion (BLEVE), flash fire radiant heat exposure, and explosion overpressures from unconfined vapor cloud explosions are modeled. Probability modeling is conducted by structuring event trees and assigning initiating event frequencies and conditional probabilities to the defined loss events.
Results are presented in an individual risk profile which depicts the probability of human death versus distance from the LPG storage tanks. The individual risk profile is suitable for use by the local Planning Commission as one source of information for making informed decisions concerning future development in the area north of the XYZ Plant.