Most refined products travel the final leg to market by truck. For example, the gasoline that fuels your car, truck, minivan or SUV probably arrives at your local service station by tanker truck. Most of today's tankers have three or four separate compartments so, at the distribution center, lines from several storage tanks come together at a single loading "rack." This allows the driver to fill each tank compartment with the desired product -- multiple grades of gasoline, diesel fuel -- without moving the truck.
The driver follows a strict safety protocol while loading the truck, one product at a time. A metered pump delivers a preset amount, and then shuts off.
Each tank compartment is likely to contain gasoline vapor left over from its previous contents. To improve air quality, product is loaded from the bottom of the compartment. This pushes the vapor up and out through a pipe at the top of the tank. (There is a sensor at the top of the compartment that protects the truck from being overfilled.) The collected vapor is drawn out and reprocessed to liquid form and added back into the tanks.»next