Dynamic impact testing
Pipeline and Hazardous Materials Safety Administration · Mar 21, 2023 · Reference No. 2-0129
Interprets: 49 CFR § 173.320, 49 CFR § 173.320(a), 49 CFR § 178.274(j)(6)
March 21, 2023
Reference No. 22-0129
This letter is in response to your November 30, 2022, email and subsequent telephone conversations with a member of my staff requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to the testing of portable tanks. Specifically, you ask whether there are any “exemptions” from the dynamic longitudinal impact test requirement, specified in § 178.274(j)(6), for portable tanks containing “UN1977, Nitrogen, refrigerated liquid, 2.2” by highway transportation only.
As specified in § 178.274(j)(6), United Nations (UN) portable tanks used for the dedicated transportation of “Helium, refrigerated liquid,” UN1963, and “Hydrogen, refrigerated liquid,” UN1966, that are marked “NOT FOR RAIL TRANSPORT” in letters of a minimum height of 10 cm (4 inches) on at least two sides of the portable tank are excepted from the dynamic longitudinal impact test. However, there are certain scenarios where non-specification portable tanks may be used when transported by highway. For example, § 173.320(a) states that “atmospheric gases and helium, cryogenic liquids, in Dewar flasks, insulated cylinders, insulated portable tanks, insulated cargo tanks, and insulated tank cars, designed and constructed so that the pressure in such packagings will not exceed 25.3 psig under ambient temperature conditions during transportation …” are excepted from the requirements of subchapter C of the HMR, provided all the requirements of § 173.320 are met. Therefore, a highway shipment of “UN1977, Nitrogen, refrigerated liquid, 2.2” may be transported in a non-specification insulated portable tank, provided the portable tank is constructed so that the pressure will not exceed 25.3 psig under ambient temperature conditions during transportation and all other requirements of
§ 173.320 are met.
I hope this information is helpful. Please contact us if we can be of further assistance.
Sincerely,
T. Glenn Foster
Chief, Regulatory Review and Reinvention Branch
Standards and Rulemaking Division
173.320, 173.320(a), 178.274(j)(6),
A letter of interpretation applies the regulations to the facts the requester described. It isn’t a regulation and isn’t legal advice. The agency’s copy.