In my 45 years in this business, I have seen and heard of many of these types of events. I conduct audits throughout the U.S. and one of the sections is devoted to confirming adequate grounding systems for all product movements. These types of incidents have occurred in all operations involving loading and unloading of barges, ships, trucks, and rail cars.
Normally, tank trucks are configured with:
- 1) a pump to deliver the diesel from a tank
- 2) a meter to measure diesel loaded
- 3) a load arm or hose to connect the pump to bottom load the truck
- 4) a combination grounding / overflow system to properly ground the truck and to prevent overfilling the truck
- 5) electronics to control and account for the loading
The systems can be scaled back to save costs, but most parts, especially the grounding systems, are key safety components. Products like diesel moving through pipes, etc. create static electricity. This static can cause arcing or sparking, which can ignite the product. The scaling back could include top-loading without meters. In addition, the pump and the piping systems should be grounded separately. Lack of or poor grounding can create arcing / sparking, which can ignite certain vapors. The best practice is to set the system up so that if the grounding and overflow systems are not connected, or are malfunctioning, the system won’t operate. If it is inoperable, it should be locked out for repairs.
I would expect the person loading the truck to be trained and certified in the processes. This would include familiarity with grounding, switch loading, overfill, emergency operation, pump operation, etc.
The components of a fire are oxygen, fuel, and an ignition source. Fire prevention relies on eliminating at least one or all three of these components. If any of the three components are missing, there can be no fire. As an example, proper grounding eliminates one source of ignition, static discharge and preventing leaks, spills, overfills, etc. keeps the product properly contained which eliminates the fuel from being present. Another area of focus is a practice called switch loading which should be avoided or not allowed. Switch loading is loading diesel into a trailer last containing gasoline (and still contains gasoline vapors). The gasoline vapors are much more flammable than diesel. Also, top loading (called splash loading) rather than best practice of bottom loading could increase the likelihood of static electricity buildup (and ignition).