NeoWave S.A.S. de C.V. — Hazardous Materials Safety Interpretation

Page 11200 New Jersey Avenue, SE Washington, DC 20590 U.S. Department of Transportation Pipeline and Hazardous Materials Safety Administration March 19, 2026 Francisco Davila Registered Inspector NeoWave S.A.S. de C.V. Hacienda Monte Real 107 Hacienda El Campanario Apodaca, Nuevo Leon, Mexico 66643 Reference No. 25-0115 Dear Mr. Davila: This letter is in response to your August 7, 2025 letter requesting clarification of the Hazardous Materials Regulations (HMR; 49 CFR Parts 171-180) applicable to cargo tank modifications. Specifically, you state that you are inquiring about modifying a cargo tank to a different specification than that which it was originally built. You state that some manufacturers, repair facilities, and registered inspectors are under the assumption that a Motor Carrier (MC) 300- series cargo tank can have its name plate modified to reflect a current Department of Transportation (DOT) 400-series specification if that cargo tank meets the requirements outlined in §§ 178.345 through 178.348. You ask a series of questions regarding the modification of MC 300-series cargo tanks. We have paraphrased and answered your questions as follows: Q1. You ask whether § 180.405(b)(2) allows for the recertification of MC 306, MC 307, and MC 312 cargo tanks to their original specification. A1. Yes, § 180.405(b)(2) allows cargo tanks originally manufactured as MC 306, MC 307, and MC 312 cargo tanks to be recertified to their original specification. This serves as an exception to paragraph (b)(1) of that section which states that no cargo tank may be marked or certified after August 31, 1995, to the applicable MC 306, MC 307, MC 312, MC 331, or MC 338 standard for that specification in effect on December 30, 1990. This allows a registered inspector to recertify an MC 306, MC 307, or MC 312 cargo tank after it has been modified. Q2. You ask whether § 180.405(c)(2) allows MC 300-series cargo tanks to have their pressure relief devices (PRDs) and outlets modified to conform to DOT 400-series cargo tank specifications.#

Page 2A2. Yes, MC 300-series cargo tanks may have their PRDs and outlets modified to meet certain DOT 400-series specifications as authorized by § 173.33(d)(3) and § 180.405(c)(2). PHMSA previously amended the HMR in a final rule, HM-183, to discontinue the construction of MC 300-series cargo tanks and authorized the use of DOT 400-series PRDs on the remaining in-service MC 300-series cargo tanks.a Q3. You ask whether it is permissible, if a cargo tank complies with the regulations applicable to a DOT 400-series cargo tank, to change the specification on the nameplate from showing MC 300-series to show DOT 400-series. A3. Yes, the HMR allows for the modification, stretching, or rebarrelling of only those listed MC 300-series cargo tanks to the corresponding DOT 400-series specifications specified in § 180.413(d)(2)(i) through (iii). All the provisions in § 180.413(d)(1) through (d)(4) must be met for modifications, including the installation of a supplemental specification plate, nameplate, or both containing the information that reflects the cargo tank as modified, stretched, or rebarrelled. I hope this information is helpful. Please contact us if we can be of further assistance. Sincerely, Alexander Wolcott Acting Chief, Regulatory Review and Reinvention Branch Standards and Rulemaking Division a 54 FR 24982 (Jun. 12, 1989)#

Page 3NeoWave S.A.S. de C.V. R.F.C.: NEO230628AS6 Hacienda Monte Real 107, Hacienda El Campanario Apodaca, Nuevo León, México, 66643 +52 (813) 593-0901 contacto@neowave.mx August 7, 2025 Larson, R. 25-0115 Standards and Rulemaking Division Pipeline and Hazardous Materials Safety Administration, Attn: PHH-10 U.S. Department of Transportation 1200 New Jersey Avenue, SE East Building, 2nd Floor Washington, DC 20590 phmsa.hm-infocenter@dot.gov Request for Interpretation To whom it may concern, I am writing to inquire about the possibility of modifying a cargo tank to a different specification than the one it was originally manufactured under. Some manufacturers, repair facilities, and registered inspectors operate under the presumption that a cargo tank in the MC 3XX series can have its name plate modified to reflect a current DOT 4XX series, since the cargo tank meets the requirements outlined in §§178.345 through 178.348. According to §180.405, which addresses the qualification of cargo tanks, paragraph (b) states that a cargo tank originally manufactured to, and I quote, “the MC 306, MC 307, or MC 312 specification may be recertified to the original specification provided” it meets the requirements further outlined in that paragraph. Additionally, §180.405(c)(2) states that a cargo tank listed in paragraph (c)(1) of the same section may have its pressure relief devices and outlets modified to conform to a newer specification. So, the following questions arise: 1) If a cargo tank complies with all current regulations applicable to the DOT 4XX series, is it permissible to change the specification on the name plate from an MC 3XX series to a DOT 4XX series? 2) If the answer to the previous question is no, how should the regulations be interpreted to support the conclusion that the cargo tank cannot be reclassified from its original specification? I truly appreciate your attention to this matter. Sincerely, Francisco Davila | Registered Inspector Email: francisco.davila@neowave.mx Mobile: +52 (818) 011-1643 Fax: +1 956 997 9231#