by Jeffrey D. Marx and John B. Cornwell
Abstract
Over the past ten years, there has been a growing focus on risk analysis and risk assessment in the process safety community. Regulations like the EPA's Risk Management Program have brought the word risk to the forefront of our discussions. One problem that is apparent during such discussions is the lack of a common frame of reference for terms such as risk analysis, risk assessment, and quantitative risk analysis (QRA). Even if all parties in a discussion agree that risk is the combination of the consequences and probability of occurrence of unwanted events, they might still disagree on what constitutes a QRA. Unfortunately, risk assessments and qualitative or semi-quantitative risk analyses are often referred to as QRAs, as are studies that include the generation of a risk matrix. A true quantitative risk analysis for a process plant is a complex and extensive study that involves consequence modeling, probability data, vulnerability models/data, local weather and terrain conditions, and possibly local population data. This detailed type of study has many useful applications, but only if done correctly. Without the required tools or data, attempts to perform a QRA generally produce results that have little value. This paper attempts to clarify what a QRA is and what it is not, and to show the types of information that can be generated when (correctly) performing a QRA for a petroleum, petrochemical, or chemical processing facility.