Around 25% of all freight hauled in the US is transported in tanker trucks, and of that, nearly half is petroleum products (gasoline, diesel, and aviation fuel)*.
So, with so much hazardous cargo on the nation’s roads, and the occurrence of cars driving under road tankers not uncommon, why are there so few spillages and fatalities?
The answer can be credited to several factors; driver training, the design of the tankers and safety equipment being fitted to road tankers. Equipment such as highly-engineered manlids/manholes, vapor recovery equipment (valves and vents), foot valves/emergency valves/internal valves, API (American Petroleum Industry) adaptors/tank units, manifolds & dust caps and Electronic Stability Control Systems.
This equipment is engineered for road tankers by several manufacturers including Civacon, Emco Wheaton, Girard Equipment, Alpeco, Betts Industries, Dixon Bayco and Scully to name just a few.
Although each manufacturer offers slightly different equipment to meet different specifications, the common theme running through all tank truck equipment is that it must meet DOT 406 regulations, so when fitted to the road tankers the vehicle meets the regulation.
A DOT 406 road tanker meets the federal requirements for the transport of Gasoline, AvGas, Diesel Fuel and Jet-A. The equipment allows it to have a maximum operating pressure of four psi. It must also meet several other specifications that assist in preventing serious incidents. These include a separate manhole for each compartment, emergency shutoff on the driver’s side front and rollover protection to prevent manholes from opening on rollover.
All the above-mentioned road tanker equipment, if it meets DOT 406, will assist the tankers in meeting these specifications. Over the years, manufacturers have perfected their equipment’s design with updated tank truck equipment being regularly released to the road tanker and hazardous cargo industries.
Manlids and manholes are available in a range of sizes and materials depending on the application. They have integrated pressure release technology that allows only a small amount of spillage should a rollover occur. This ensures pressure does not build up in the tank leading to possible explosions.
Vapor recovery equipment (valves and vents) are designed to channel vapors to the correct location rather than causing a build-up in the road tankers or being vented into the atmosphere.
Foot valves/emergency valves/internal valves have two purposes. They are part of the product transfer mechanism, moving product into the tanker, and they are designed as a ‘weak or break’ point that sits under the road tankers and are engineered to sheer and close off access to the tanker ensuring minimal or no spillage should the tanker roll, or a car drive under.
API adaptors/tank units, manifolds & dust caps are designed to be robust enough to withstand a collision or rollover incident.
Electronic Stability Control (ESC) systems were initially used in automobiles but in recent years have been applied to the road tanker industry. The system can anticipate a potential rollover incident and will safely apply the road tanker’s brakes to avoid the accident.
With regards to the tanker itself, with around 1.22 billion tons of Gasoline, AvGas, Diesel Fuel, Jet-A and chemicals being hauled each year in tanker trucks that can hold 10,000 gallons of product each, tanker design is vital when combatting incidents. When hauled, fuel can expand and contract depending on its ambient temperature. It can also move inside the tank and lead to an ever-changing center of gravity for the vehicle. This potential danger is mitigated by tankers being designed to have a low center of gravity. They also have internal bulkheads which separate products and add strength to the tanks.
Technology and equipment within the road tanker industry is continuously improving with the latest incarnation of ‘safe driving’ being the fully automated vehicles. Many professionals within the hazardous cargo industry are concerned that the elimination of any driver responsibility could lead to increased, rather than decreased incidents. Tests are currently underway but it’s likely that many years of field trials will be required before the road tanker industry, specifically the segment that transports petroleum products, accepts a driverless vehicle.
*National Tank Truck Carriers, Inc. (NTTC)