(146a) Protecting Gasoline Storage Tanks from Lightning: Lessons Learned from a Recent Gasoline Storage Tank Explosion and Fire

This paper presents a recent investigation into explosion and ensuring fire that occurred in an unleaded gasoline storage tank during lightning storm. The aboveground storage tank used to store unleaded gasoline had an internal floating roof design, meaning the tank had an internal floating roof that was covered by a geodesic dome. As it typical for volatile substances such as gasoline stored in internal floating roof tanks, fuel vapors will eventually migrate around the internal floating roof through several pathways and flammable vapors were present in the headspace. The tank was equipped with a nitrogen blanketing system that was intended to prevent a flammable atmosphere in the tank headspace by supplying nitrogen and thus preventing air ingress during periods of product discharge and thermal inbreathing. The tank was also equipped with a fixed foam suppression system attached to the geodesic dome for early fire suppression efforts.

In the early evening during a thunderstorm, an explosion occurred within the headspace that blew the geodesic dome roof off the tank and led to an ensuing fire. The explosion damaged the fixed foam suppression system, hence early suppression efforts were delayed on the tank. The paper presents the results of a detailed investigation analysis into the cause of the incident, which includes detailed analysis of the lightning strike. This includes video footage from several cameras showing that ignition of the flammable vapors within the tank headspace occurred within a second of an indirect lightning strike (i.e., lightning that did not directly strike the tank). The study will present lessons learned regarding the failures associated with nitrogen blanketing system and the fixed foam suppression system, and also provide critical recommendations to help prevent future incidents.