“Switch Loading” and “splash filling” lead to tanker truck explosion killing the VP of the company

On February 2, 2011, Employees #1 and #2 worked for a petroleum and petroleum product company. Employee #1 was on top of a transport tanker into which the firm’s vice-president transferred #1 diesel fuel, mixing it with about 1,000 gallons of #2 diesel fuel.  Employee #2 was on the ground.

After “splash filling” the center tank with about 300 gallons 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 of unleaded gasoline. Now, it contained only vapors.

An explosion occurred, and the resulting fire consumed 1,000 gallons of gasoline and 1,300 gallons of diesel fuel in the tanker trailer. The older diesel tank truck was severely damaged but still contained about 1,000 gallons of #1 diesel. Employee #1 was killed in the fire on top of the tanker. 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:

1. There was no bonding between the two vehicles.
2. There was no potential grounding of the tanker trailer to the three-inch gasoline line hooked to the 10,000-gallon storage tank being filled.
3. 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.
4. There was an attempt to “switch load” the diesel fuel into the gasoline tank, which contained vapors with a flash point of minus 45 degrees Fahrenheit (minus 43 degrees Celsius).
5. 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-degree Fahrenheit weather, with low humidity.
6. Accordingly, there was a static spark with an estimated two to ten times the energy needed to ignite gasoline.

Section 5(a)(1) The employer did not furnish employment and a place of employment which was free from recognized hazards that were causing or were likely to cause death or serious physical harm to employees in that employees were exposed to chemical and fire hazards:

(a) Picabo Livestock bulk fuel tanks, on or about February 2, 2011, employees were transferring #1 diesel from a bulk truck to compartments of a tank trailer using splash-filling methods through the dome of the trailer. No bonding or static lines were used between the two vehicles.

The front compartment of the tank trailer previously contained Class 1 flammable gasoline.

Note: Among other methods, some feasible and acceptable abatement methods to correct these hazards are to refer to

• National Fire Protection Association (NFPA) 385, Standard for Tank Vehicles for Flammable and Combustible Liquids, (2007 Edition), Section 9.2, Loading and Unloading Tank Vehicles, for safe operating procedures for electrical bonding during dome filling or
• American Petroleum Institute (API), Recommended Practice 2003; Protection Against Ignitions Arising Out of Static, Lightning, and Stray Currents, January 2008, Section 4.1.5 Preventive Measures in preventing charge generation, charge accumulation, incendive spark discharge, and avoidance of flammable atmospheres

Source: https://www.osha.gov/ords/imis/establishment.violation_detail?id=315027870&citation_id=01001