NealDavidson
Professionally I am Design Engineer of electrical equipment which is used for lightning protection like Dissipation Array System (DAS®), Spline Ball Ionizer (SBI®), Spline Ball Terminal (SBT®) and more lightning prevention products.
Why Is Fuel Tank Lightning Protection Important? - Lightning Eliminators. A Floating roof tank (FRT) is a type of tank used for the storage of large amounts of petroleum products such as crude oil to allow any trapped gas within the oil to escape, as this stabilizes the crude oil. The FRT has an open top which is equipped with a steel roof which moves up and down according to the level of the stored petroleum product in the tank. The floating roof edge is rounded with a rim seal that has a function of preventing the flammable vapor of the stored product from escaping outside the tank and mixing with air, which helps to prevent fires from occurring. The tank seal is made of flexible insulating materials of different designs. Destructive lightning events do not need to be a direct strike to the tank itself. Shunts were envisioned to permit any lightning-related current to propagate from the floating roof to the tank shell to ground without generating a spark.
Sadly, shunts are extremely unreliable and are not easily inspected except through a maintenance event.