The report said an abnormal flow of electricity occurred as a result of “improperly grounded equipment” in the roof area of the tank, a static discharge or ignition charge in the tank was the “most probable cause of ignition” in the October 15, 2019 incident. The tank’s roof was blown off & landed on a nearby tank, which in turn exploded within minutes of the first explosion. Each tank held 126,000 gallons of ethanol. “The electrical fault ignited an ethanol vapor air mixture in the headspace of tank 20107,” the report says. A component called a Varec device “was not properly grounded”.
As a result of this investigation, the following conclusions were determined:
- The first explosion originated inside tank 20107
- The second explosion was a result of damage from the roof of tank 20107 landing on tank 20109 and exposing tank 20109 to the fire at tank 20107
- The closed vent Pressure Relief Valve (PRV) in the vapor recovery line for tank 20107 had no pallet allowing the Vapor Recovery Unit (VRU) to pull from the tank creating a greater air to ethanol vapor atmosphere in the headspace
- The headspace within tank 20107 had a mixture of air and ethanol vapor
- An electrical fault occurred from an unknown source and manifested itself in the Varec tape as a result of improperly grounded equipment
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