Emergency Response Information: High Pressure Gas, Composite (19.2)
Criticality: High
Progress: Addressed, Not Adequately
Score: 20
DOT Relevance: §172 Subpart G
Description of Key Area
This key area pertains to the availability of appropriate
information resources needed by first responders to potential emergencies
(e.g., accidents) involving hydrogen stored and transported as a compressed gas
in composite cylinders, which may be part of a hydrogen fueling infrastructure.
“Composite cylinders” as used here refers to a broad range of pressure vessel
types that include metallic or polymer shells (liners) that are reinforced by
being hoop- wrapped or full-wrapped with high-strength carbon, fiberglass, or
other fibers, which are generally resin impregnated. DOT special permits currently
allow compressed hydrogen to be transported in certain specific types of composite
packagings, as specified in the special permit language.
The emergency response information must be applicable to tube
trailers and/or any other compressed hydrogen composite cylinder packaging. In
particular, the emergency response information resources must apply to
operations such as the transfer of hydrogen from tube trailers to stationary
pressure vessels at vehicle fueling stations, temporary parking of tube
trailers to provide the hydrogen source at a fueling station, delivery of
hydrogen-filled composite cylinders to fueling stations, and the use of
hydrogen “mobile fuelers” with composite pressure vessels.
Discussion of Criticality
This key area will be critical if hydrogen fueling
infrastructures evolve that utilize hydrogen transported as a compressed gas in
composite cylinders. Examples include hydrogen transported in tube trailers
from central production plants to fueling stations (with the gas transferred to
permanently installed high-pressure vessels at the fueling station, or, as is more
common, parking of the tube trailer at the fueling station to serve as a
temporary gas supply) and “mobile fuelers” (some of which utilize compressed
hydrogen stored in composite cylinders). However, the economic viability of
these infrastructure scenarios appears to be poor at this time, and so they are
unlikely to be part of potential future hydrogen-fueled vehicle
commercialization. The economic problems derive from the fact that, even with
composite cylinders, the total quantity of hydrogen that can be transported in
a tube trailer (or a mobile fueler) is such that the cost per unit mass or
energy of hydrogen delivered to a fueling station would require the dispensed
hydrogen cost to substantially exceed established goals.
As discussed below, emergency response resources applicable to
accidents involving compressed hydrogen in steel pressure vessels (e.g., as
used in tube trailers) are well developed for current applications, which are
generally limited to restricted-access industrial sites and trained personnel.
These same resources are probably appropriate and adequate for supporting
current tests and demonstrations of hydrogen vehicles, which are few in number,
have limited access, and are closely managed by trained personnel. A possible
exception may be associated with current and future use of mobile fueling
stations that store hydrogen in composite vessels. These units involve a
relatively unusual combination of components (e.g., unlike tube trailers, they
are not addressed specifically in the DOT ERG2004) and their application
straddles two jurisdictions (i.e., DOT when they are transported on highways
and OSHA/local AHJs when they are parked and operated as vehicle fueling
stations).
Another issue may derive from the fact that current experience and
emergency response information resources pertain primarily to applications such
as tube trailers equipped with steel pressure vessels, which are designed,
manufactured, tested, and marked consistent with DOT-3A or -33A specifications
in 49 CFR 178.36 and §178.37,
respectively. An accident involving a composite tube trailer in a fire
situation, for example, may include special issues associated with the
flammability or combustion product toxicity of the fiber materials or resins
used in composite pressure vessel construction.
If hydrogen-fueled vehicles commercialize with a fueling
infrastructure that involves tube trailers and/or the use of any other
composite pressure vessels in DOT-jurisdiction applications, then new and
specifically focused emergency response resources will be needed to enable
first responders to deal effectively with potential accidents in environments
such as public-access fueling stations. Moreover, these emergency response
information resources will need to address any special emergency response
requirements associated with the fact that the pressure vessels are of
composite construction rather than steel construction.
Discussion of Progress
Progress toward providing the technical basis to support
development of emergency response information applicable to a potential
hydrogen fuel infrastructure involving compressed hydrogen stored in composite
cylinders is rated as “Addressed, Not Adequately.” This is because, although
resources are currently available to guide emergency response to accidents
involving compressed hydrogen packaging and transportation systems using steel
pressure vessels, these were not developed with the anticipation that they
would apply to public access situations such as fueling stations, and they do
not include any special considerations that may be associated with composite
materials (e.g., the previously mentioned potential flammability or combustion
product issues).
The above-referenced currently available emergency response
information resources include the DOT ERG2004. Compressed hydrogen is assigned
ID Number 1049 and covered by Guide Number 115 (Gasses—Flammable, Including
Refrigerated Liquids). Emergency response guidance pertaining to tube trailers that might transport hydrogen is also
contained in literature produced by industrial gas companies (e.g.,
“Safetygrams”) and other sources.
In 2005, the NASFM and DOT’s RITA established the Hydrogen
Executive Leadership Panel (HELP). HELP’s mission is “…to bring together
emergency responders, government regulators, scientists, consumers and experts
from the automotive and energy industries to facilitate a safe and orderly
transition to hydrogen and other alternative fuel sources.” HELP will focus on
issues involved in training, educating, and mobilizing emergency responders to
work with government, industry, and community groups to facilitate and ensure
hydrogen transport, storage and distribution, and the safety of vehicles and
environs.
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
It is recommended that progress toward hydrogen-fueled vehicle
commercialization should be monitored, and if there are indications that
composite pressure vessels may be used as part of the fueling infrastructure
beyond the pre-commercial demonstration phase (e.g., for tube trailer delivery
of hydrogen to fueling stations), then work to develop appropriate emergency
response information resources should be initiated. These resources should
address any particular requirements associated with compressed hydrogen
delivery and unloading at public-access fueling stations and any special issues
associated with the use of composite rather than steel pressure vessels.
More research is also needed to develop emergency response
resources applicable to mobile hydrogen fueling stations with composite
pressure vessels, especially if the use of such mobile fueling stations
increases.
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