Dust explosion propagation and isolation

Abstract

Industrial processes handling combustible dusts usually comprise numerous pieces of equipment, such as grinders, mixers, dryers, classifiers, dust collectors, and storage hoppers, interconnected by a more or less complex network of pipes and conveying systems.If a combustible dust cloud is accidentally ignited in a process enclosure, large amounts of heat and high pressures are generated in milliseconds. The resulting dust deflagration may, or may not compromise its structural integrity depending if the vessel is adequately protected or not. Nevertheless, the deflagration pressure will push the fireball through any existing openings, including process interconnections. The flame front will stretch and speed up due to increased turbulence, accentuating the severity of the initial event. Ultimately, a more violent secondary deflagration can take place when the flame reaches the next process enclosure, such that existing protection measures may well fail under these aggravated conditions.While the need to protect process enclosures from a dust deflagration (either by venting or suppression) is widely recognized, the isolation of interconnections, on the other hand, generally receives less attention. This can be explained by some persistent myths and misconceptions about dust explosion propagation leading to a false sense of security.This paper unravels three common myths about dust explosion propagation, introduces explosion isolation technology and demonstrates the importance of large-scale testing for the validation of explosion isolation designs.