On February 2, 2011, Employees #1 and #2 were working for a petroleum and petroleum product company. Employee #1 was on top of a transport tanker into which the vice-president of the firm was transferring #1 diesel fuel, mixing it with about 1,000 gallons (3,785 liters) of #2 diesel fuel. Employee #2 was on the ground. After “splash filling” the center tank with about 300 gallons (1,136 liters) of #1 diesel fuel, the firm’s vice-president attempted to transfer the remainder of the #1 diesel to the truck’s front tank. He was going to do this task through “switch loading.”
The front tank had previously contained 3,500 gallons (13,248 liters) of unleaded gasoline. Now, it contained only vapors. An explosion occurred, and the resulting fire consumed 1,000 gallons (3,785 liters) of gasoline and 1,300 gallons (4,921 liters) of diesel fuel in the tanker trailer. The older diesel tank truck was severely damaged, but it still contained about 1,000 gallons (3,785 liters) of #1 diesel. Employee #1, on top of the tanker, was killed in the fire. The fire spread to Employee #2, who was on the ground. His clothing caught on fire, but he escaped with only minor burns.
Several causes were believed to have led to the generation, accumulation, and discharge of static electricity in the presence of flammable gasoline vapors, gasoline liquid, and diesel liquid. They included but were not limited to these:
- There was no bonding between the two vehicles.
- There was no potential grounding of the tanker trailer to the three-inch (7.6 cm) gasoline line hooked to the 10,000 gallons storage tank being filled.
- The transfer of 300 gallons of #1 diesel fuel, a known static accumulator, was done by “splash filling”; that is, without the use of a downspout.
- There was an attempt to “switch load ” the diesel fuel into the gasoline tank, which contained vapors with a flash point of -45 degrees Fahrenheit
- There was an accumulation of static electricity on the employee making the transfer. The static electricity built up on his winter clothing and insulated boots, in zero degrees Fahrenheit weather, with low humidity.
- Accordingly, there was a static spark with an estimated two to ten times the energy needed to ignite gasoline.
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