The trucks used for transferring stored fuel from a storage tank to a vehicle used to be done from an opening built into the top of the storage tank. More trucks are now bottom loading fuel trucks.
The sloshing and turbulence involved with the movement of a heavily volatile liquid like gasoline increased separation which then creates a large amount of evaporating product. Bottom loading fuel trucks eliminate the access to the air pocket that forms at the top of the tank as the load is decreased and the product churns during transport. If the top remains sealed access to the natural evaporation spot is eliminated.
It was discovered that loading gasoline below the fill line reduces product movement, sloshing and creating vapors. Gasoline in most cases is now loaded from the side or bottom of the tank.
Eventually, bottom loading fuel trucks will be filled robotically, increasing speed and efficiency of loading.
Bottom loading fuel trucks offer more benefits than can be achieved with top loader options.
Bottom loading keeps employees grounded and less likely to slip or fall from an elevated height. The OSHA requirements in place for working from elevated heights are different than the ground-based requirements. There are fuel arms designed for bottom loading that have vapor recovery systems integrated on them. Bottom loading also allows for the simultaneous loading of several tank compartments at the same time. Eventually, bottom loading will be done robotically, increasing speed and efficiency of loading.
Bottom loading is another weapon in the arsenal in the war to reduce vaporization of product. The EPA estimates that over 140 million gallons of fuel evaporate in the United States each year. This affects the bottom line of any fuel distribution company.
The cost of converting top loading tanks is expensive, so more fleets are replacing top loading trucks with bottom loaders as truck ages and then comes offline.
There are no current EPA requirements that mandate a tank truck is loaded from the bottom. All fuel trucks including top and bottom loaders are still subject to tank guidelines in Chapter 120 regarding the tank portions of fuel delivery trucks.