Composite/Novel Media Tube Trailer Specifications (26)

Criticality: High
Progress: Addressed, Not Adequately
Score: 20
DOT Relevance: §178

Description of Key Area

DOT requires that non-liquefied compressed gases be shipped in specification containers. Composite cylinders are not included in DOT cylinder specifications. Therefore, composite cylinders are only allowed in service by obtaining a special permit in accordance with 49 CFR 107 Subpart B.

Discussion of Criticality

Compressed hydrogen gas is currently transported in steel tube trailers, typically at pressures from 16.5 to 27.6 MPa (2400 to 4000 psi). Volume for tubes is a minimum of 454 kg (1000 lb) water capacity. Diameters are typically from 0.23 to 0.56 m (9 to 22 in). The weight efficiency of steel tanks is not high. The weight of hydrogen stored on a trailer with steel tubes is approximately one percent. As pressure increases, this weight efficiency will decrease further. A trailer with steel tubes is limited by gross vehicle weight, not by size of the trailer. As the need for hydrogen grows the need for transporting by tube trailers increases, particularly for distribution within major cities where it is not practical to build hydrogen pipelines.

Trailers with composite tubes would be able to carry about three percent hydrogen by weight, allowing a greater volume of gas to be carried. Composite tanks can also be designed to higher operating pressures without introducing significant manufacturability issues. However, obtaining required special permits to use composite cylinders in transportation may take from six months to several years.

Discussion of Progress

DOT currently has no composite cylinder standards. It is planning to recognize ISO 11119 as part of the cylinder standards adopted by the UN Committee of Experts in its “orange book”. However, ISO 11119 and other industry standards have not, to date, addressed larger cylinders such as would be used in tube trailers. The lack of coverage for large cylinders is not due to specific technical issues, it is more a reflection that no one has asked for this coverage in the past.

Composite cylinder standards have been developed or are in development by various groups, including CGA, CSA in Canada and America, and ASME. Standards developed by these groups include FRP-1, FRP-2, FRP-3, CSA B51, CSA NGV2, and ASME Section X.

ASME's Boiler and Pressure Vessel project team on hydrogen tanks is addressing high pressure gas storage in metal and composite tanks. The work plan includes a proposed new article KD-10 to Section VIII-3, a code case on composite tanks for Section VIII-3, and a revision to code case 2390 on metal lined composite reinforced circumferentially wrapped pressure vessels under Section VIII-3. Transport tanks may also be included in Section XII.

Recommendations

DOT should work with SDOs noted above that have developed, and are developing, standards that apply to composite cylinders that are capable of carrying hydrogen. These standards should be evaluated for ability to address larger cylinders that would carry compressed hydrogen. DOT should work with these SDOs to develop updates that can address the size and pressures needed by the hydrogen distribution industry. DOT should then adopt acceptable standards by reference.