The Trinity League
Transporters in the hazardous waste industry commonly make use of three main DOT-specific tanker trailers: 406, 407, and 412. Each of these numbers indicates the DOT specifications that tanker trailer was built to which in turn indicates the (generally) compatible classes of chemicals. Let’s start by taking a look at the DOT-406 tanker.
The DOT-406 tanker, also called the “non-(low)pressure bulk liquid cargo tank” if you’re the kind of person who hates parties, is the most basic of the liquid haulers. They can only withstand a wee bit of pressure (4 psi), are made of aluminum, and can only hold the “friendliest” of wastes.
Common Uses: They are commonly used to transport veritably inert materials, such as milk or water, or flammable but unreactive wastes such as those derived from petroleum products
Chemical Incompatibilities: Aluminum 406 tanks are quite fragile when compared with their stainless steel (S.S.) counterparts. Because aluminum is more reactive than S.S. (we’ll explain why later), it is more susceptible to damage and corrosion from a variety of common chemicals. Aluminum tanks cannot hold household corrosives like vinegar (acetic acid/water mixture) or caustics like calcium carbonate solutions (CaCl2, the main ingredient in Tums®). They are also incompatible with a host of other chemicals, including a variety of chlorides, bromides, sulfates, nitrates, bicarbonates, and hydroxides, as well as a handful of common organics
The DOT-407 or “low-pressure bulk liquid cargo tank,” is the Goldilocks of chemical tankers. Composed primarily of stainless steel and able to hold a wide variety of chemicals, the 407 is the workhorse of the hazardous waste transportation industry. Stainless steel, which contains chromium and molybdenum in addition to iron and carbon, is more resistant to chemical damage due to an oxidized, or “passivated” layer on the surface of the tank. They may also possess some sort of interior coating or lining.
Common Uses: Mild acidic and basic compounds, nitric acid, various hydroxides, combustible liquids, organics, and inert wastes
Chemical Incompatibilities: While S.S. 407 tanks are pretty darn tough, they do have a few Achilles heels’. Some of the notable incompatibilities are common chemicals including sulfuric, hydrofluoric, and hydrochloric acids, as well as most, if not all, chlorides.
The DOT-412 “Corrosives Cargo” tanker is the workhorse of the hazardous waste transportation fleet. Some are composed of lined or coated stainless steel, others are composed of fiber-reinforced polymers, but either way, they’re made to move the nasty stuff.
Common Uses: Hydrochloric acid, hydrofluoric acid, and ferric chlorides
Chemical Incompatibilities: This one is up to the manufacturer. Some tankers may be made specifically for certain hazardous wastes, while others may be more generalized. Check with the manufacturer of your particular model if you have doubts about the compatibility of a certain chemical with your tank.
Issues With Incompatabilities
Properly storing wastes in compatible trailers is essential for both the wellbeing of the public as well as the maintaining of your transportation fleet. Sure, sometimes, damage caused by incompatibilities happens quick, fast, and in a hurry. However, the truth is that a vast majority of damage occurs slowly, over long periods, and is only noted during the tanker’s catastrophic failure.
For example, imagine an S.S. DOT-407 tanker that has been used to transport a 20% acetic acid solution for the past 5 years, without its lining and passivation layer having been inspected. While the tanker is able to transport acetic acid at that low of a concentration, it is also susceptible to corrosion over extended periods of use. Over time, the acetic acid etches away at the steel until one day, during a routine transport, one of the welds on the tank fractures under the weight of the cargo, releasing the acetic acid onto the roadway and into the adjacent watershed.
While this may have been a hypothetical, there are countless real-life examples of accidental release originating from incompatibility. Being knowledgeable about the many classes of chemicals and the vessels that can contain them is vital for compliant and incident-free hazardous waste transportation. Make sure to inform yourself about all the requirements, stipulations, and recommendations before loading up your shiny new tanker with a questionable waste stream!
If you have any questions, whether they’re about tank compatibilities or hazardous waste management in general, feel free to contact us online or call us at (562) 906-2633.