Hydrogen Fuel Standards Progress at ISO Meeting

The fifth plenary meeting of the International Standards Organization’s (ISO) Technical Committee 197 and parallel meetings of three ISO working groups were held 26-28 June 1996, in Stuttgart, Germany.

A proposal by Daimler-Benz Aerospace Airbus—part of the German delegation—for a new work item on an Airport Hydrogen Fueling Facility was accepted. The use of hydrogen as a fuel for aircraft instead of a hydrocarbon fuel will affect many of the standards currently used in the industry. Target date for use of the international standard is December, 1999.

This work item, introducing standards for the use of hydrogen at airports and on aircraft, is being modeled on existing ones for kerosene fueling facilities. The standards most directly affected are the Federal Airworthiness Standards for Transport Category Airplanes (FAR Part 23/25), Airworthiness Standards for Aircraft Engines (FAR Part 33), and the National Fire Protection Association documents for Aircraft Fuel Servicing (NFPA No. 407) and Aircraft Fuel System Maintenance (NFPA No. 410C).

The U.S. delegation announced its intention to submit formal proposals for three new work items related to the use of gaseous hydrogen: fuel tanks, fueling stations, and connectors. It was agreed to eventually establish three new working groups upon approval of these proposed work items. Project leaders will be confirmed at the same time the proposals are forwarded to the technical committee for voting. The NHA is leading these proposals.

H2 Product Specifications

ISO Working Group 3 reviewed a working draft (WD) of product specifications for hydrogen fuel. The purpose of this standard—which would apply to all modes of transportation and hydrogen fueling applications (ground, water, air, and space)—is to describe the quality characteristics of hydrogen fuel and to assure uniformity in the quality of the hydrogen produced and used.

In the working draft, gaseous hydrogen (GH2), for the purpose of this international standard, is defined as hydrogen that has been produced to gaseous form typically by any number of methods—including petrochemical, thermochemical, solar, electrolytic, or biological processes—and brought to essentially ambient conditions as an equilibrium mixture of ortho-hydrogen and para-hydrogen purified to a minimum of 98 mole percent. GH2 is classified as Type I and can be designated as Grade A, B, or C.

Liquid hydrogen (LH2) is defined as hydrogen that has been liquefied (i.e., brought to a liquid state) either by chilling and compression or other means, such as magneto-caloric effect; it is classified as Type II. Slush hydrogen (Type III) is hydrogen that is a mixture of solid and LH2 at the triple-point temperature.

Applications of Hydrogen Fuel

The following information characterizes a representative application of each type and grade of hydrogen fuel as specified by the WD. It is noted that suppliers commonly transport hydrogen (especially liquid transporters) in a higher purity than some users may require. The “lower” grades of A or B provide less stringent requirements, which may be more suitable for “captive” systems such as vehicle fleets/common fill or on-site hydrogen production/use as in industrial complexes.

Other parameters covered by the proposed standard include quality verification, sampling, test methods, safety, and detection.

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