European and USA design standards for gas explosion venting are quite different in their predictions, with the European standards always giving a higher predicted explosion Pred for the same vent coefficient, Kv. The format of the two predictions are different with the US standards following the approach of Swift expressing the vent area as a ratio to the surface area of the vessel, As/Av and the European standard using the vent coefficient approach. Kv= V2/3/Av. It is shown that these two approaches are directly related as As is proportional to V2/3. The reactivity parameter in the US standards is the laminar burning velocity, UL, and in the European venting standards it is the deflagration parameter, KG = dp/dtmax/V1/3. It is shown that these two reactivity parameters are linearly related. The USA standard is shown to be compatible with spherical flame venting theory and with experimental data other than that of Bartknecht. There is also good agreement with the present results for a 10L vented vessel for which the spherical laminar flame venting theory gives reasonable agreement but predicts the Pred to be higher than measured. This is because of the assumption that at the maximum value of Pred the bulk flame area is equal to As which is not valid. The US standard also has corrections for flame self acceleration, which is a vessel size effect, and for the influence of vessel size on the external explosion, which are not factors addressed in the European standards. The European standard is the equation for the results of Bartknecht for a 10 m3 vessel and the results of higher and lower volumes in Bartknecht’s results are all lower that for 10 m3. The experimental results reviewed, for methane and propane maximum reactivity vented explosions, include data for vessels larger than that on which the European standards are based and they all give significantly lower values of Pred than those of Bartknecht..
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