1. (a) Outage and filling limits.

   1. (1) Except as otherwise provided in this subchapter, liquids and liquefied gases must be so loaded that the outage is at least five percent for materials poisonous by inhalation, or at least one percent for all other materials, of the total capacity of a cargo tank, portable tank, tank car (including dome capacity), multi-unit tank car tank, or any compartment thereof, at the following reference temperatures—

      1. (i) 46 °C (115 °F) for a noninsulated tank;
      2. (ii) 43 °C (110 °F) for a tank car having a thermal protection system, incorporating a metal jacket that provides an overall thermal conductance at 15.5 °C (60 °F) of no more than 10.22 kilojoules per hour per square meter per degree Celsius (0.5 Btu per hour/per square foot/ per degree F) temperature differential; or
      3. (iii) 41 °C (105 °F) for an insulated tank.
   2. (2) Hazardous materials may not be loaded into the dome of a tank car. If the dome of the tank car does not provide sufficient outage, vacant space must be left in the shell to provide the required outage.

2. (b) Equivalent steel. For the purposes of this section, the reference stainless steel is stainless steel with a guaranteed minimum tensile strength of 51.7 deka newtons per square millimeter (75,000 psi) and a guaranteed elongation of 40 percent or greater. Where the regulations permit steel other than stainless steel to be used in place of a specified stainless steel (for example, as in § 172.102 of this subchapter, special provision B30), the minimum thickness for the steel must be obtained from one of the following formulas, as appropriate:

   Formula for metric units

   e1 = (12.74e0) / (Rm1 A1) 1/3

   Formula for non-metric units

   e1 = (144.2e0) / (Rm1 A1) 1/3

   where: e0 = Required thickness of the reference stainless steel in mm or inches respectively; e1 = Equivalent thickness of the steel used in mm or inches respectively; Rm1 = Specified minimum tensile strength of the steel used in deka-newtons per square millimeter or pounds per square inch respectively; and A1 = Specified minimum percentage elongation of the steel used multiplied by 100 (for example, 20 percent times 100 equals 20). Elongation values used must be determined from a 50 mm or 2 inch test specimen.

3. (c) Air pressure in excess of ambient atmospheric pressure may not be used to load or unload any lading which may create an air-enriched mixture within the flammability range of the lading in the vapor space of the tank.

4. (d) A bulk packaging may not be loaded with a hazardous material that:

   1. (1) Is at a temperature outside of the packaging's design temperature range; or
   2. (2) Except as otherwise provided in this subchapter, exceeds the maximum weight of lading marked on the specification plate.

5. (e) Stacking of IBCs and Large Packagings.

   1. (1) IBCs and Large Packagings not designed and tested to be stacked. No packages or freight (hazardous or otherwise) may be stacked upon an IBC or a Large Packaging that was not designed and tested to be stacked upon.
   2. (2) IBCs and Large Packagings designed and tested to be stacked. The superimposed weight placed upon an IBC or a Large Packaging designed to be stacked may not exceed the maximum permissible stacking test mass marked on the packaging.

6. (f) UN portable tanks.

   1. (1) A UN portable tank manufactured in the United States must conform in all details to the applicable requirements in parts 172, 173, 178 and 180 of this subchapter.

   2. (2) UN portable tanks manufactured outside the United States. A UN portable tank manufactured outside the United States, in accordance with national or international regulations based on the UN Recommendations (IBR, see § 171.7 of this subchapter), which is an authorized packaging under § 173.24 of this subchapter, may be filled, offered and transported in the United States, if the § 172.101 Table of this subchapter authorizes the hazardous material for transportation in the UN portable tank and it conforms to the applicable T codes, and tank provision codes, or other special provisions assigned to the hazardous material in Column (7) of the Table. In addition, the portable tank must—

      1. (i) Conform to applicable provisions in the UN Recommendations (IBR, see § 171.7 of this subchapter) and the requirements of this subpart;
      2. (ii) Be capable of passing the prescribed tests and inspections in part 180 of this subchapter applicable to the UN portable tank specification;
      3. (iii) Be designed and manufactured according to the ASME Code (IBR, see § 171.7 of this subchapter) or a pressure vessel design code approved by the Associate Administrator;
      4. (iv) Be approved by the Associate Administrator when the portable tank is designed and constructed under the provisions of an alternative arrangement (see § 178.274(a)(2) of this subchapter); and
      5. (v) The competent authority of the country of manufacture must provide reciprocal treatment for UN portable tanks manufactured in the United States.

[Amdt. 173-224, 55 FR 52612, Dec. 21, 1990, as amended at 56 FR 66266, Dec. 20, 1991; Amdt. 173-234, 58 FR 51532, Oct. 1, 1993; Amdt. 173-243, 60 FR 40038, Aug. 4, 1995; Amdt. 173-252, 61 FR 28676, June 5, 1996; Amdt. 173-255, 61 FR 50624, Sept. 26, 1996; 66 FR 33426, June 21, 2001; 67 FR 15743, Apr. 3, 2002; 68 FR 75742, Dec. 31, 2003; 74 FR 2255, Jan. 14, 2009; 76 FR 56315, Sept. 13, 2011]