PHMSA adopts ASME Section XII code for transport tank construction and repair

The Pipeline and Hazardous Materials Safety Administration (PHMSA), an agency of the Department of Transportation, has issued a final rule incorporating by reference the 2015 edition of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section XII, and the 2015 edition of the National Board of Boiler and Pressure Vessel Inspectors National Board Inspection Code (NBIC), Parts 2 and 3, including Supplement 6. The rule was published in the Federal Register of 28 September 2026 as FR Doc. 2026-19741, under Docket No. PHMSA-2010-0019 (HM-241) and RIN 2137-AE58. It takes effect on 28 October 2026, with a voluntary compliance date of 28 September 2026, and the incorporation by reference was approved by the Director of the Federal Register as of 28 October 2026.

The action amends the Hazardous Materials Regulations (HMR; 49 CFR parts 171–180) and finalizes efforts begun by PHMSA’s predecessor, the Research and Special Programs Administration, which in 1995 asked the ASME Board on Pressure Technology Codes and Standards to develop standards written specifically for transport tanks. ASME published Section XII in 2004, based on Section VIII, Division 1. The rule was signed by Paul J. Roberti, Administrator of PHMSA, on 24 September 2026.

What the rule authorizes

Section XII becomes an alternative to ASME Section VIII, Division 1 (2017 edition), not a replacement. Manufacturers may build the following specification tanks to Section XII standards or continue using Section VIII, Division 1:

• Cargo tank motor vehicles (CTMVs): MC 331 and 338, and DOT 406, 407 and 412.
• Cryogenic portable tanks: UN T75.
• Ton tanks: DOT 106A and 110AW.

PHMSA amends § 171.7 to list the 2015 edition of Section XII, reference the 2017 editions of Sections II, V, VIII and IX, and list the 2015 edition of the NBIC. It also adds new provisions at § 173.252, § 178.278, § 178.301, § 179.302, § 180.402 and § 180.602, and revises § 107.307 and § 107.503.

Repairs, stamps and inspections

For tanks built to Section XII, all inspections, repairs and alterations must follow the 2015 NBIC and Supplement 6. Repairs must be performed by a DOT-registered facility holding a current National Board certificate of authorization for the “R” stamp. The final rule does not require the “TR” stamp proposed in the 2016 supplemental notice; PHMSA instead adds a reference to the new “T” stamp alongside the existing “U” and “R” stamps, so that a facility manufacturing or repairing a Section XII CTMV submits its “T” stamp authorization to the Federal Motor Carrier Safety Administration.

PHMSA states that use of Section XII is optional and that an operator who finds it disadvantageous may continue with Section VIII, Division 1 and follow the HMR. The agency also notes that Section XII provides a rational design methodology and specific fatigue-analysis standards, and that it permits greater allowable stresses, yielding fuel savings.

Costs, benefits and the record

PHMSA describes the rule as deregulatory, imposing no new costs and producing quantified net cost savings of approximately $8.1 million per year for the regulated community at a seven percent discount rate. The agency estimates that some facilities could pay as little as $250 to purchase the newest ASME code, and it rejects claims of a $3.64 million industry cost increase as unsupported.

The rule addresses three longstanding petitions for rulemaking (P–1459, P–1474 and P–1502) and two National Transportation Safety Board recommendations, H–11–5 and H–11–6, issued after the investigation of a rollover and fire involving a cargo tank semitrailer carrying liquefied petroleum gas. PHMSA received 17 sets of comments on the 2016 supplemental proposal, including submissions from the International Tank Container Organisation, the National Propane Gas Association, the Commercial Vehicle Safety Alliance, NJP Engineering, Silver/Cims LLC, @TCO, Container Technology Inc. and Gardner Cryogenics. PHMSA concluded that the adoption of Section XII and the 2015 NBIC will not have a significant impact on a substantial number of small entities, since the provisions are optional.

The change matters to carriers, tank manufacturers and repair shops because it opens a second, transport-specific construction standard for equipment that moves hazardous materials on public roads, while tightening the credential required for repairs to tanks built under it.

Source: Federal Register, Vol. 91, No. 186, 28 September 2026, Rules and Regulations, p. 61144 (official reference: FR Doc. 2026-19741).