Gas-Phase Detonations in Pipes: the 8 Possible Different Pressure Scenarios and their Static Equivalent Pressures Determined by the Pipe Wall Deformation Method (part 1)

Explosive gas mixtures which are prone to undergo the transition from deflagrative to detonative explosion can occur in chemical process plants. In this case explosion pressure resistant design is the only viable safety concept. Whereas such a design is straightforward to realize for deflagrative explosions, which can be treated as static loads, there is worldwide not yet any accepted procedure for constructing pipes and vessels to be pressure proof against the dynamic loads brought about by gas-phase detonations. In particular, there is still a huge lack of the fundamental information on the peak height and peak width of the different conceivable detonative pressure scenarios, not to mention of how to evaluate the interaction of these pressure peaks with the walls of the enclosures. In this paper the focus is on detonations in pipes. For the first time ever a systematic classification of the different detonative pressure scenarios is established. To do so, it is proposed to define two different pipe types and to distinguish between 8 different detonative pressure scenarios. In a next step the pipe wall deformation method is proposed which allows to assign to each of the 8 detonative, highly dynamic pressure scenarios an equivalent static pressure which can then be used in the formulae of by the established pressure vessel guidelines, which can only cope with static loads, to determine the desired detonation pressure proof pipe design. Based on the large number of experiments done so far, a proposal is presented which allows to predict in good quantitative approximation all short pipe scenarios on the basis of two long pipe scenarios, which substantially reduces the experimental effort. The expected variation of the static equivalent pressures with variation of initial temperature, initial pressure and the mixture composition is discussed.