Unambiguous assessment of gas explosion overpressure

As part of an industrial project, an assessment of the risk of an open-air gas explosion (UVCE – unconfined vapor cloud explosion) is carried out to analyze the consequences for people and define the constraints for sizing installations and/or equipment. Different approaches or methods can be used, ranging from "simple", quick-to-use methods (e.g. the Multi-Energy method) to more complex CFD (computational fluid dynamics) approaches.

In practice, the Multi-Energie method has established itself as one of the benchmark methods for modeling gas explosions. It provides a "simple" assessment of the potential consequences of a gas explosion in an unconfined environment. Nevertheless, it requires the maximum overpressure generated by the explosion to be set as input data. To date, there is no practical method for unambiguously defining this overpressure. CFD modeling tools can be used to accurately assess an overpressure profile. However, their implementation is rather cumbersome.

A method called METEOR (method to evaluate overpressure) has been developed to help analysts determine the maximum overpressure generated by an explosion in industrial plants. It is an intermediate method between the use of methods that are "simple" in principle but difficult to implement in practice (GAME, etc.) and CFD.

It is based on CFD explosion calculations, analysis of tests and accidentologies, certain semi-empirical methodologies (GAME, CAM, etc.) and expert opinions.

The aim of the method is to provide a consistent and unambiguous assessment of the explosion overpressure levels to be retained for the application of the Multi-Energy method. It can be used both in regulatory risk analyses (e.g. as part of hazard studies (EDD) required by French regulations) and on engineering projects.

This article presents the principle and the various stages of the METEOR method. First, the context for quantifying the effects of a gas explosion and the limitations of current methods for assessing the maximum overpressure in the explosive cloud are reviewed. The use of the method is then illustrated by an application example based on an accident case and a comparison with the investigation results associated with this case.