Hydrogen-Specific Detectors Update
Karen Hall,
National Hydrogen Association
ISO TC 197 Working Group (WG 13:
HYDROGEN DETECTORS) met on June 7 in France to continue work on the development
of an international standard for multi-level hydrogen-specific detectors. The
group has several new members and addressed many of the issues relating to the
need for the standard, scope, and comments from participating countries on the
second working draft. There was not enough time available to complete the review
of comments, so an additional meeting is being planned for autumn in Vancouver.
The
background for the formation of WG13 was described in an article published in
the February 2006 Hydrogen and Fuel
Cell Safety Report.
While IEC 61779 covers detectors for flammable
gases, there are no provisions for measuring range, selectivity and poisoning,
which are considered essential for securing the safety of hydrogen installations.
UL 2075 covers toxic and combustible gas and vapor detectors and sensors intended
to be portable or employed in indoor or outdoor locations in accordance with the
National Electrical Code, NFPA 70.
The ISO WD took as many provisions from
the IEC standard as possible. However, WG13 recognizes that IEC 61779 did not
address some issues that should be addressed for hydrogen-specific detectors.
Due
to hydrogen's wide flammability range, it is desirable to detect lower concentrations
with more accuracy than afforded in IEC 61779. The new ISO WD proposes simpler
test requirements that address the issues of hydrogen measurement and monitoring
only. It is also attempting to simplify any tests where doing so does not compromise
the safety or performance, but merely avoids steps and equipment that are designed
to test detection equipment for gases other than hydrogen.
The Working
Group proposed a revised scope during the ISO TC 197 Plenary on June 8, but this
revision was not approved. Participating countries raised concerns that the scope
remains confusing, and suggested either limiting the scope to hydrogen refueling
stations, expanding it to all stationary applications, or focusing on the suitability
of the standard when hydrogen measurement and monitoring is required, rather than
specifying applications. The one point where there was agreement, however, was
that the standard is not intended to cover on-board vehicle applications, where
alternative methods for ensuring safety are more suitable. The Technical Committee
directed WG 13 to take the comments raised during the TC meeting back to the Working
Group and propose a new scope at a later date.
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