Aircraft Carriage, Hydride Systems (30.1)
Criticality: High
Progress: Not Addressed
Score: 40
DOT Relevance: §175
Description of Key Area
The carriage by aircraft of hydride-based hydrogen storage
systems is considered critical for commercial success by many potential
manufacturers of the hydrogen storage systems and fuel cell appliances and
devices powered by them. This area covers both rechargeable and
non-rechargeable type hydrogen storage systems, micro and portable systems and
stand-alone systems and systems coupled to appliances. This section will
discuss stand-alone systems that are being transported when not coupled to an
appliance; Item 30.2 discusses aircraft carriage of systems coupled to an
appliance.
As has been previously discussed, hydride-based hydrogen storage
systems can be divided into two broad categories, rechargeable systems and
non-rechargeable systems. The rechargeable systems contain a reversible
hydride-forming material and are refilled by applying hydrogen; they will most
likely be identified by UN 3468 or NA 9279 with a 2.1 flammable gas hazard
classification. Non-rechargeable systems will likely contain a mixture of
hazardous materials that are not normally allowed within a single package since
they are capable of reacting together to produce a flammable gas. These systems
will require exceptions to a number of clauses in current regulations and may
require either new hazardous materials table entries or ORM-D exceptions. Each
of these two categories can be further divided into “micro” and “portable”
systems, with the difference being the intended use of the appliance they fuel.
Micro systems are primarily intended for use with low-power fuel cell
appliances for use in consumer electronics, such as cellular phones and laptop
computers. It is considered essential that these systems be able to be carried
and used by travelers in the passenger cabin of aircraft and upper size
limitations will likely be imposed. Portable systems are not intended to be
used in fixed, stationary locations but it is not expected that they need to be
carried or used in the passenger cabin of aircraft.
Hydride-based hydrogen storage systems may be transported onboard
aircraft as either cargo or in passenger baggage, especially with micro systems.
When transported by individuals within baggage, the systems may or may not
include any original overpacking supplied by the manufacturer. For allowance
onboard cargo-only aircraft, modifications to appropriate entries of the
hazardous materials table, §172.101,
will need to be made. Exceptions or packaging instructions may need to be
included in 49 CFR 173. Packaging instructions and container specifications
were discussed in Items 18 and 27 of this report.
For allowance onboard passenger aircraft, in addition to what is
required for cargo-only aircraft, further consideration needs to be given to
the potential hazards and risks. As cargo onboard passenger aircraft, the
hazards are essentially the same as for cargo-only, however with greater
potential risk of loss of life if an accident was to occur. When carried
onboard passenger aircraft by passengers there is even more risk due to lesser
control over packaging. Here it may be appropriate to apply limitations on
individual system size or capacity and limits on amounts that can be carried by
individual passengers. This allowance may require modification to the language
that is required to be posted by commercial airlines, §175.25(a)(1). The language currently forbids carrying onboard
aircraft of hazardous materials with several cited exceptions, such as “certain
smoking materials,” fuel cartridges for use with micro fuel cell systems may
need to be included. Section 175.75 lists quantity limitations aboard aircraft,
the appropriateness of these limitations with respect to hydride-based hydrogen
storage systems need to be reviewed.
Paragraph 175.75(a)(2) allows up to 25 kg (55 lb) net weight of
an allowed hazardous material to be carried aboard an aircraft; for a UN 3468
material, does net weight refer to hydrogen or the hydride material? The weight
of hydrogen may only be a few percent of the total hydride weight, thus 25 kg
(55 lb) of hydrogen could translate into several hundred kilograms of hydride
material. In addition §175.75(b) places no quantity limitation on ORM-D
materials, limitations may be appropriate if non-rechargeable hydride-based
systems are shipped under ORM-D exceptions.
Discussion of Criticality
This item has been assigned a criticality of high. It is expected
that many manufacturers will seek allowance of hydride-based hydrogen storage
systems aboard aircraft. DOT-E 13598 currently allows up to 90.7 kg (200 lb) of
UN 3468 material aboard cargo-only aircraft. Allowance will be sought to allow
micro systems to be carried in carry-on baggage within the passenger cabin of
aircraft.
Consideration must be given to size and quantity limitations to
systems to be allowed within passenger baggage, carry-on and checked, and that
allowed as cargo on passenger and cargo-only aircraft. Packaging instructions
and container specification must include appropriate testing to ensure safety
of the systems allowed aboard aircraft.
While it is considered critical that appropriate packaging
instructions be developed, it is also recommended that the packaging instructions
be designed so as to not prohibit new and innovative designs. This technology
is relatively new and is evolving. New advanced materials and designs are
expected. The packaging instructions should therefore be performance-based and
avoid being too prescriptive, while ensuring a minimum level of safety.
Discussion of Progress
Hydrogen as a compressed gas, UN 1049, is allowed on cargo-only
aircraft with a 150 kg (331 lb) net limit. UN 3468, Hydrogen in a metal hydride storage system has been included in ICAO’s
dangerous goods list and forbidden from carriage on either cargo-only or
passenger aircraft. At the recent ICAO Dangerous Goods Panel meeting in Oct/Nov
of 2005, the panel accepted a proposal from the US
panel member to allow cargo-only carriage, with a 100 kg (220 lb) limit. This
new ruling is to become effective in January of 2007. Carriage aboard passenger
aircraft has not been allowed. US
DOT special permit E 13598 allows up to 90.7 kg (200 lb) of UN 3468/NA 9279
material be carried aboard cargo-only aircraft.
An informal and then a formal proposal were made to the UN SCETDG
by the representative from Japan,
to allow micro fuel cell systems and the fuel cartridges to be carried aboard
aircraft. The original informal proposal requested a new entry in the Dangerous
Goods List (DGL), with a hazard class 9. The formal proposal submitted for
consideration at the July 2005 meeting of the UN SCETDG was revised and instead
requested a new DGL entry with a flammable gas hazard, class 2.1. This proposal
was withdrawn without consideration. It is anticipated that a new proposal will
be submitted requesting modification of UN 3468 to include systems coupled with
fuel cell units as well as the stand-alone systems.
Progress on developing consensus standards that might be used as
a basis for packaging instructions include:
- The
ISO technical committee for hydrogen technologies (TC 197) has a working group
drafting a standard for transportable reversible metal hydride hydrogen storage
systems (ISO 16111). This document is currently in the approval stage as a
committee draft (“CD”) for advancement to the draft international standard
stage (“DIS”). In parallel to the CD approval, the document is being considered
for publication as a technical specification; with possible publication of the
TS much earlier than possible for the International Standard. Once the
international standard is approved, the technical specification will be
withdrawn. This document only considers stand-alone containers.
- IEC
TC 105 has drafted and is currently reviewing a draft publicly available
standard for Micro Fuel Cell Systems (IEC PAS 62282-6-1). This document
includes sections on fuel storage containers and complete integrated fuel cell
appliances with fuel containers. This standard is expected to reference ISO
16111 for metal hydride-based hydrogen storage container design and testing.
- UL
is developing a consensus standard (UL 2265) on micro fuel cell systems. An
effort is being made to keep UL 2265 consistent with IEC 62282-6 and its development
is therefore trailing that of IEC 62282-6.
Recommendations
It is recommended that the OHMS develop a minimum set of design
and test criteria for packaging of hydride-based hydrogen storage systems as
previously recommended in Items 18 and 25 of this report. Consideration should
be given to the impact of onboard aircraft carriage. These criteria should be
provided to potential manufacturers and offerors for use in their design and
testing of the storage systems and would help ensure consistency in application
of rigor in determining the minimum level of safety. Size and quantity
limitations need to be considered for allowance aboard passenger aircraft,
particularly for inclusion in passenger baggage, checked as well as carry-on.
It is preferred that these criteria be performance-based. Ideally they would be
based on the ISO and IEC standards underdevelopment by international expert
committees (ISO 16111 and IEC 62282-6-1).
The language required to be posted by commercial airlines, §175.25(a)(1) needs to be reviewed
for any appropriate changes if hydride-based hydrogen storage systems are
allowed to be carried aboard aircraft by passengers. The quantity limitations
of §175.25(a) and (b) need to
be reviewed for appropriateness and possible revision if hydride-based hydrogen
storage systems are allowed aboard aircraft.
To help ensure that the standards being developed for
hydride-based hydrogen storage systems meet the need of OHMS, it is recommended
that the OHMS assign personnel or contractors to actively participate on the
applicable development committees. These would include ISO TC 197 working group
10, IEC TC 105 working group 8, and UL’s STP 2265.
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