Lightning And Electrostatic Hazards In Industrial Safety

摘要

Lightning and electrostatic discharge (ESD), are two electrical hazards that are ever present in industrial processes and are of considerable importance in high consequence industries dealing with relatively sensitive materials. Both hazards have been around from the beginning of time, are naturally produced phenomena and can give rise to serious outcomes. Although there are some similarities between the two phenomena, there are also significant differences in scale. Further, lightning is an 'exterior' phenomenon, and protection is all about avoiding its ingress into the industrial facility and preventing its propagation to the hazardous material. Electrostatic charge generation on the other hand is an 'internal' or 'locally' generated process, and protection is based mainly on suppression techniques. Although both phenomena have been around for a long time and a great deal of effort has been expended on the analysis of the phenomenology, it is true to say that we are still at the learning stage. This is particularly true for the lightning hazard, where unexpected events still occur. For this reason, protection strategies are based on best practice deterministic approaches, often supplemented by somewhat less convincing (in assurance terms) statistical risk assessments. Even then, for high consequence industries this approach is supplemented by a conservative multiple lines of defence (LOD) strategy, because of the inherent difficulty of quantifying the risk of a less conservative approach. Experience of lightning also continues to show that previously held beliefs are not necessarily true and that the subject is fraught with misconceptions. This paper reviews, in broad terms, the current (traditional) understanding of the phenomena, and the currently accepted protective measures.