Progress: Not Addressed
DOT Relevance: 178
DOT requires in 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.
Compressed hydrogen gas is currently held in steel, aluminum, or composite cylinders for portable applications, typically at pressures from 16.5 to 41.4 MPa (2400 to 6000 psi). Volume for cylinders is up to 454 kg (1000 lb) of water capacity; larger cylinders are covered under tube specifications. Light weight is one consideration for cylinders, so that they can be carried more easily. Composite cylinders are lighter in weight than metallic cylinders. As pressure increases, this weight advantage of composite tanks will increase further.
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 portable applications may take from six months to several years.
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, there are additional cylinder standards in use in North America that may offer advantages if used for portable cylinder applications.
Composite cylinder standards have been developed or are in development by various groups, including CGA, CSA in Canada and in 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.
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 cylinders that would carry compressed hydrogen in transportable applications. 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.