The Baker-Strehlow-Tang vapor cloud explosion (VCE) blast load prediction methodology utilizes flame speed as a measure of explosion severity. In previous publications, guidance has been presented for selecting flame speeds as a function of congestion, confinement, and fuel reactivity. These recommended values were based on empirical data available from the literature.

Baker Engineering and Risk Consultants, Inc. (BakerRisk®) and Daewoo Engineering and Construction Co. Ltd. (Daewoo) performed vented (i.e., partially-confined) vapor cloud explosion (VCE) tests with both propane and lean hydrogen mixtures. BakerRisk’s Deflagration Load Generator (DLG) test rig was used to perform the tests. The DLG test rig was designed primarily to produce centrally-peaked blast waves that are representative of VCEs suitable for blast loading test articles, but has also been used for vented deflagration testing.

Ammonia and hydrogen represent opposite ends of the spectrum with regard to the potential blast loading resulting from an accidental vapor cloud explosion (VCE), although many in industry have expressed doubts as to whether either of these fuels actually pose a VCE hazard. Ammonia is some-times discounted as a VCE hazard due to the perceived difficulty in igniting an ammonia-air mixture and/or because of its low laminar burning velocity. Hydrogen is sometimes discounted as a VCE hazard due to the ease with which a hydrogen-air mixture can be ignited and/or because of its buoy-ancy.

The ignition of a hydrogen-air mixture that has engulfed a typical set of ambient vaporizers (i.e., an array of finned tubes) may result in a deflagration-to-detonation transition (DDT). Simplified curve-based vapor cloud explosion (VCE) blast load prediction methods, such as the Baker-Strehlow-Tang (BST) method, would predict a DDT given that typical ambient vaporizerswould be rated as medium or high congestion and hydrogen is a high reactivity fuel (i.e., high laminar burning velocity).