Tractor Trailer Fuels
All big rigs use diesel fuel. Diesel fuel is harder to ignite that regular fuel. In fact the flash point of diesel fuel in the tank is about 140 degrees Fahrenheit. Compare this to the flash point of regular gasoline in the tank of -35 degrees Fahrenheit.
Since big rigs typically carry 100 gallons of diesel fuel, if the fuel is ignited, it can be a major catastrophe for the rig, its driver and any passenger vehicles in the area. Most diesel fuel in trucks is heated by recirculation through the fuel pump. However, because of the high flash point of this fuel, a large energy source is generally required to ignite even this warm fuel.
Unlike passenger crashes with gasoline, rupture of the fuel tank will probably not ignite the diesel fuel through sparks or a hot exhaust manifold. Of course, if the big rig is carrying flammable materials a rupture could easily ignite those materials and cause thereby giving the diesel fuel an ignition source. Absent that scenario, research suggests that the most likely ignition source for a diesel fuel fire in a roll over or collision is the battery box.
Crushing or shorting out the batteries in conjunction with a tank rupture may create a large fire. To avoid this potential problem the best solution is to move the batteries. If they are placed behind the cab in front of the fifth wheel, or inside the frame rails so that the frame rails protect them, there is a much better chance that a collision or roll over will cause the batteries to ignite any diesel fuel leaking from a ruptured gas tank.
If the batteries cannot be moved because of potential interference, the next best suggestion is to put a heaby gage steel box over the batteries to protect them. However, if this is done the cage should not be welded to the frame rail. This will ruin the heat treatment and the rail will break. The steel protective battery box should be bolted on.
Most drivers also carry a fire extinguisher in the cab to address potential sources of fuel ignition in an accident. Since many drivers smoke, this is a good idea. However, if the rig rolls over, the lack of crashworthiness of most cabs will cause the cab to crush likely killing or severely injuring the driver. If he was smoking at the time of the accident, his ability to use the fire extinguisher after a crash to extinguish a lit cigarette will be virtually nonexistent.