Institution of chemical engineers vent duct method applied to the VDI vent sizing technique

Vent ducts are used to direct vented explosions to safe areas where they cannot cause damage to personnel and property. Guidance is available for straight vent ducts and ducts containing bends, but it is important that this guidance is self-consistent and is not applied alongside a vent sizing method for which it has not been designed. The draft harmonised standard for Dust Explosion Venting Systems contains a method for estimating the effect on the reduced explosion pressure of linear vent ducts. Comparisons have been done to show how the results of this method compare to those from other available guidance. The method in the draft standard does not apply to vent ducts containing bends. But the effect of bends can be important if ducts are to be installed in relatively cramped and obstructed facilities. In this report the UK Institution of Chemical Engineers guidance for vent ducts is used to show the degree of some of the differences in reduced explosion pressure that inclusion of a bend in a vent duct can produce. A method for taking these effects into account and linking them to the vent duct guidance in the draft harmonised standard is suggested,