Evaluation Protocols for Flammable and Toxic Dispersion Models

The siting of LNG facilities requires several types of hazards to be quantified so the risk to the public and public property in areas surrounding each facility can be properly assessed. In order to quantify the hazards from potential accident scenarios, computational tools must be used. Given the multiplicity of tools available, ranging from empirical models to 3D computational fluid dynamics packages, the agency reviewing the project application may not have the methodologies or protocols necessary to determine the suitability of a given model to a certain scenario, its accuracy and any other setup requirements.

Though the computational models currently approved by PHMSA for vapor dispersion hazard analysis were only evaluated against LNG spills, they are commonly used to determine the hazards associated with pressurized releases, overpressures and elevated heat flux exposures. Therefore, the Pipeline and Hazardous Materials Safety Administration (PHMSA) commissioned Blue Engineering and Consulting and the Gas Technology Institute to develop a set of Model Evaluation Protocols, that will allow the review of modeling tools for several different hazards, including flammable and toxic dispersion, source terms for dispersion models, vapor cloud explosions, and BLEVEs.

This paper discusses the first two MEPs completed as part of this project to evaluate flammable dispersion and toxic dispersion models. The paper will discuss the evaluation methodology, including the information to be submitted by the model proponents and the review process, and the model validation databases compiled for each protocol.