(99a) Lightning Related Ignition Mechanisms and Associated Protection Techniques for Storage Applications

Lightning can pose a myriad of threats to operations involving flammable vapors and liquids that give off flammable vapors.  This paper focuses primarily on storage facilities and associated operations but the principles can be applied to any operation or installation where a flammable environment may exist.  General principles of protection from a lightning threat are provided, along with a discussion of specific threats presented by operations in which flammable vapors may be present.   The evolution of protection considerations is also discussed.  Techniques for protection from direct attachment are provided to address those situations where an external flammable vapor could exist in the vicinity of a storage vessel.  Threats produced by nearby lightning and strikes to associated piping and electrical conduits are also addressed.  The elimination of both external and internal potential differences that could lead to dangerous arcing is discussed.  This paper also provides a discussion of the difference in grounding system impedance versus static grounding techniques as they relate to the dissipation of lightning currents and explains their significance in minimizing the probability of arcing between structural components and systems.  The principles discussed are summarized in the context of the development of a lightning protection plan.