Drag Loads From Vapor Cloud Explosions

Drag loads due to the gas flows generated by vapor cloud explosions (VCEs) can damage piping and vessels, particularly near or in the flammable cloud. There is little guidance available to the piping and vessel designer regarding the magnitude of such drag loads, beyond evaluating drag loads on a case-by-case basis [e.g., using computational fluid dynamics (CFD)]. This paper presents a newly developed set of drag loads vs standoff distance for a range of flame speeds and vapor cloud sizes. Nine flame speeds were evaluated, up to and including supersonic flame speeds. Cloud sizes are characterized using energy scaled standoff distances (i.e., Sachs scaling). The purpose of this work is to provide a database of drag loads that can be used to evaluate the structural response of piping, vessels, equipment, and supporting structures. The database presentation is similar to that used for existing VCE blast load charts, such as those used in the Baker-Strehlow-Tang (BST) and TNO MEM (Multi-Energy Model) methods.