Tanker trucks haul roughly a quarter of all freight transported across the United States.
With capacities ranging from 5,500 to 11,600 US gallons, these enclosed vessels maintain a crucial supply chain between the nation’s producers and consumers, carrying liquid cargo ranging from gasoline to milk. With much of this cargo consisting of volatile and hazardous materials, it is vital that each truck loading shipment is as safe, secure, and still as possible. Spill containment measures are also required by the EPA.
There are three basic tanker designs — bulkheads, baffles, and smoothbores — which affect how liquid cargo moves while trucks are in motion:
Bulkheads are solid dividers that create separate, smaller storage compartments within the tanker. While this design greatly reduces the amount of back-and-forth movement of the tanker’s liquid cargo, it does little to prevent side-to-side movement of the liquid, which can put the tanker at risk for tipping over.
It is very easy to overload bulkheads on the front or back, so when operators load or unload a tanker with bulkheads, it is important that they distribute the liquid cargo as evenly as possible. Failure to do so can result in an unstable, unsafe load.
Similar to bulkheads, baffles are angled dividers with holes that slow down the front-to-back flow of the tanker’s liquid cargo.
While baffles help to minimize the internal movement of liquids and keep them evenly distributed, side-to-side movement of the liquid can still cause these types of tankers to overturn on curves.
These tankers have one long, smooth interior compartment with no bulkheads or baffles. While the design allows the interior to be sanitized for the hauling of foodstuffs, the lack of bulkheads or baffles also allows liquid cargo in partially filled tankers to slosh around freely, pushing the truck in the same direction it’s traveling.
If a driver shifts or accelerates too quickly, the liquid rushes to the back of the tanker, slowing it down. If the driver breaks too sharply, the cargo will slam into the front of the trailer, creating a potentially hazardous “liquid surge” that can cause the vehicle to skid into an intersection.
Petroleum products make up nearly half of all cargo hauled by tanker trucks. Read more to learn why these vehicles are involved in so few accidents, spillages, and fatalities.