This standard contains specifications for a cargo tank with very efficient insulation and relatively low heat leak to the lading. This cargo tank resembles an oversized thermos bottle because the liquid container is supported in an approximately concentric manner within the outer jacket, with insulation contained in the annular space. Thus, the outer jacket is often the primary structural member anchored to the truck bed or the tandem and upper coupler (fifth wheel) assemblies.
This cargo tank specification contains the suggested minimum guidelines for insulated, non-DOT specification cargo tanks intended for transporting nonflammable cryogenic liquids such as argon, helium, nitrogen, and oxygen at pressures less than 25.3 psi (174 kPa) in the highway mode in the United States. These cargo tanks are allowed by paragraph 173.320 of the U.S. Department of Transportation (DOT) Title 49 of the U.S. Code of Federal Regulations (49 CFR).
In Canada, the Transportation of Dangerous Goods Regulations (TDG Regulations) of Transport Canada (TC) apply. These regulations require that cargo tanks be constructed, used, and maintained in accordance with CSA B620, Highway tanks and TC portable tanks for the transportation of dangerous goods and CSA B622, Selection and use of highway tanks, TC portable tanks, and ton containers for the transportation of dangerous goods, Class 2.