[Federal Register Volume 89, Number 75 (Wednesday, April 17, 2024)]
[Proposed Rules]
[Pages 27502-27561]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 2024-07116]
[[Page 27501]]
Vol. 89
Wednesday,
No. 75
April 17, 2024
Part II
Department of Transportation
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National Highway Traffic Safety Administration
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49 CFR Part 571
Federal Motor Vehicle Safety Standards; Fuel System Integrity of
Hydrogen Vehicles; Compressed Hydrogen Storage System Integrity;
Incorporation by Reference; Proposed Rule
Federal Register / Vol. 89, No. 75 / Wednesday, April 17, 2024 /
Proposed Rules
[[Page 27502]]
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DEPARTMENT OF TRANSPORTATION
National Highway Traffic Safety Administration
49 CFR Part 571
[Docket No. NHTSA-2024-0006]
RIN 2127-AM40
Federal Motor Vehicle Safety Standards; Fuel System Integrity of
Hydrogen Vehicles; Compressed Hydrogen Storage System Integrity;
Incorporation by Reference
AGENCY: National Highway Traffic Safety Administration (NHTSA),
Department of Transportation (DOT).
ACTION: Notice of proposed rulemaking (NPRM).
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SUMMARY: This notice proposes to establish two new Federal Motor
Vehicle Safety Standards (FMVSS) specifying performance requirements
for all motor vehicles that use hydrogen as a fuel source. The proposed
standards are based on Global Technical Regulation (GTR) No. 13. FMVSS
No. 307, ``Fuel system integrity of hydrogen vehicles,'' which would
specify requirements for the integrity of the fuel system in hydrogen
vehicles during normal vehicle operations and after crashes. FMVSS No.
308, ``Compressed hydrogen storage system integrity,'' would specify
requirements for the compressed hydrogen storage system to ensure the
safe storage of hydrogen onboard vehicles. The two proposed standards
would reduce deaths and injuries that could occur as a result of fires
due to hydrogen fuel leakages and/or explosion of the hydrogen storage
system.
DATES: You should submit your comments early enough to be received not
later than June 17, 2024. In compliance with the Paperwork Reduction
Act, NHTSA is also seeking comment on a revision to an existing
information collection. For additional information, see the Paperwork
Reduction Act Section under the Regulatory Notices and Analyses section
below. All comments relating to the information collection requirements
should be submitted to NHTSA and to the Office of Management and Budget
(OMB) at the address listed in the ADDRESSES section on or before June
17, 2024.
Proposed Effective Date: The date 180 days after the date of
publication of the final rule in the Federal Register.
Proposed Compliance Date: The September 1st that is two years
subsequent to the publication of the final rule.
ADDRESSES: You may submit comments to the docket number identified in
the heading of this document by any of the following methods:
Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the online instructions for submitting
comments.
Mail: Docket Management Facility: U.S. Department of
Transportation, 1200 New Jersey Avenue SE, West Building Ground Floor,
Room W12-140, Washington, DC 20590-0001.
Hand Delivery or Courier: 1200 New Jersey Avenue SE, West
Building Ground Floor, Room W12-140, between 9 a.m. and 5 p.m. ET,
Monday through Friday, except Federal holidays.
Fax: 202-493-2251.
Instructions: All submissions must include the agency name and
docket number. Note that all comments received will be posted without
change to http://www.regulations.gov, including any personal
information provided. Please see the Privacy Act discussion below. We
will consider all comments received before the close of business on the
comment closing date indicated above. To the extent possible, we will
also consider comments filed after the closing date.
Docket: For access to the docket to read background documents or
comments received, go to http://www.regulations.gov at any time or to
1200 New Jersey Avenue SE, West Building Ground Floor, Room W12-140,
Washington, DC 20590, between 9 a.m. and 5 p.m., Monday through Friday,
except Federal Holidays. Telephone: 202-366-9826.
Privacy Act: In accordance with 5 U.S.C. 553(c), DOT solicits
comments from the public to better inform its decision-making process.
DOT posts these comments, without edit, including any personal
information the commenter provides, to www.regulations.gov, as
described in the system of records notice (DOT/ALL-14 FDMS), which can
be reviewed at www.transportation.gov/privacy. In order to facilitate
comment tracking and response, we encourage commenters to provide their
name, or the name of their organization; however, submission of names
is completely optional. Whether or not commenters identify themselves,
all timely comments will be fully considered.
Confidential Business Information: If you wish to submit any
information under a claim of confidentiality, you should submit three
copies of your complete submission, including the information you claim
to be confidential business information, to the Chief Counsel, NHTSA,
at the address given under FOR FURTHER INFORMATION CONTACT. In
addition, you should submit two copies, from which you have deleted the
claimed confidential business information, to the Docket at the address
given above. When you send a comment containing information claimed to
be confidential business information, you should include a cover letter
setting forth the information specified in our confidential business
information regulation (49 CFR part 512).
FOR FURTHER INFORMATION CONTACT: For technical issues, Ian MacIntire,
General Engineer Special Vehicles & Systems Division within the
Division of Rulemaking, at (202) 493-0248 or [email protected]. For
legal issues, Paul Connet, Attorney-Advisor, NHTSA Office of Chief
Counsel, at (202) 366-5547 or [email protected].
SUPPLEMENTARY INFORMATION:
Table of Contents
I. Executive Summary
II. Background
A. Hydrogen Fueled Vehicles
1. Hydrogen as a Motor Fuel
2. Hydrogen Vehicle Systems
B. Global Technical Regulation (GTR) No. 13
1. Overview of the GTR Process
2. History of GTR No. 13
III. Why is NHTSA issuing this proposal?
IV. Overview of Proposed Rules
A. FMVSS No. 308, ``Compressed Hydrogen Storage System
Integrity''
1. Compressed Hydrogen Storage System
2. General Requirements for the CHSS
3. Performance Requirements for the CHSS
4. Tests for Baseline Metrics
5. Test for Performance Durability
6. Test for Expected On-Road Performance
7. Test for Service Terminating Performance in Fire
8. Tests for Performance Durability of Closure Devices
9. Labeling Requirements
B. FMVSS No. 307, ``Fuel System Integrity of Hydrogen Vehicles''
1. Fuel System Integrity During Normal Vehicle Operations
2. Post-Crash Fuel System Integrity
C. Lead Time
V. Rulemaking Analysis and Notices
VI. Public Participation
I. Executive Summary
Vehicle manufacturers have continued to seek out renewable and
clean alternative fuel sources to gasoline and diesel. Compressed
hydrogen has emerged as a promising potential alternative because
hydrogen is an abundant element in the atmosphere and does not produce
tailpipe greenhouse gas emissions when used as
[[Page 27503]]
a motor fuel. However, hydrogen must be compressed to high-pressures to
be an efficient motor fuel, and is also highly flammable, similar to
other motor fuels. NHTSA has already set regulations ensuring the safe
containment of other motor vehicle fuels such as gasoline in FMVSS No.
301 and compressed natural gas in FMVSS No. 304, and the fuel integrity
systems of those systems in FMVSS No. 301 and FMVSS No. 303,
respectively. No such standards currently exist in the United States
covering vehicles that operate on hydrogen. Accordingly, this document
proposes two new Federal Motor Vehicle Safety Standards (FMVSSs) to
address safety concerns relating to storage and use of hydrogen in
motor vehicles, and to align the safety regulations of hydrogen
vehicles with vehicles that operate using other fuel sources. This
proposed rule was developed in concert with efforts to harmonize
hydrogen vehicle standards with international partners through the
Global Technical Regulation (GTR) process, and if adopted, would
harmonize the FMVSSs with GTR No. 13, Hydrogen and Fuel Cell Vehicles.
This document proposes the creation of two new safety standards:
FMVSS No. 307, ``Fuel system integrity of hydrogen vehicles,'' and
FMVSS No. 308, ``Compressed hydrogen storage system integrity.'' FMVSS
No. 307 would regulate the integrity of the fuel system in hydrogen
vehicles during normal vehicle operations and after crashes. To this
end, it includes performance requirements for the hydrogen fuel system
to mitigate hazards associated with hydrogen leakage and discharge from
the fuel system, as well as post-crash restrictions on hydrogen
leakage, concentration in enclosed spaces, container displacement, and
fire. FMVSS No. 308 would regulate the compressed hydrogen storage
system (CHSS) itself, and would primarily include performance
requirements that would ensure the CHSS is unlikely to leak or burst
during use, as well as requirements intended to ensure that hydrogen is
safely expelled from the container when it is exposed to a fire. FMVSS
No. 308 also specifies performance requirements for different closure
devices in the CHSS.
NHTSA is proposing that FMVSS Nos. 307 and 308 apply to all motor
vehicle that use compressed hydrogen gas as a fuel source to propel the
vehicle, regardless of the vehicle's gross vehicle weight rating
(GVWR). However, while FMVSS No. 307 fuel system integrity requirements
during normal vehicle operations would apply to both light vehicles
(vehicles with a GVWR of 4,536 kg or less) and to heavy vehicles
(vehicles with a GVWR greater than 4,536 kg), FMVSS No. 307 post-crash
fuel system integrity requirements would only apply to compressed
hydrogen fueled light vehicles and to all compressed hydrogen fueled
school buses regardless of GVWR.
While the proposed safety standards are drafted in accordance with
GTR No. 13, there are differences between some proposed requirements
and test procedures and GTR No. 13. This document highlights these
differences and provides reasons for these differences in relevant
sections of the preamble, and seeks public comment.
II. Background
A. Hydrogen Fueled Vehicles
1. Hydrogen as a Motor Fuel
In the pursuit of sustainable, renewable, and clean transportation,
vehicle manufacturers have continued to expand their pursuits of
hydrogen as an alternative fuel source for automobiles. Unlike their
gasoline or diesel counterparts, hydrogen-powered vehicles (hydrogen
vehicles) do not produce carbon dioxide or other emissions.
Furthermore, in contrast with battery electric vehicles, hydrogen
vehicles do not require extended recharging from an external electrical
source. These advantages, coupled with the relative abundance of
hydrogen, make hydrogen vehicles an intriguing alternative to vehicles
already offered in the market.
Hydrogen vehicles harness the chemical energy within hydrogen using
one of two methodologies. The first technique is similar to
conventional internal combustion engines (ICE) powered by petroleum
products. Hydrogen can be burned in a combustion engine and the energy
released from this process used to move pistons that provide mechanical
power to the vehicle. The second method utilizes a component called a
fuel cell that converts the chemical energy in hydrogen into
electricity. In this energy conversion process, hydrogen stored in the
vehicle reacts with oxygen in the air to produce water and energy, in
the form of electricity, which is then used to power the vehicle's
mechanical operations. Hydrogen fuel cell vehicles (HFCVs), which are
sometimes also referred to as fuel cell electric vehicles (FCEVs), are
capable of continuous electrical generation so long as they have a
steady supply of hydrogen fuel and oxygen.
One complicating factor of using hydrogen as a mobile fuel source
is its relatively low energy density. Compared to gasoline, which has a
mass density of 803 grams per liter at 15 [deg]C, uncompressed hydrogen
is extremely light, with a mass density of just 0.09 grams per liter at
15 [deg]C, which means a vehicle operating on uncompressed hydrogen
will have a significantly shorter range than a comparable gasoline-
powered vehicle. To overcome this, hydrogen is compressed to a very
high pressure of up to 70 megaPascals (MPa) while stored on a hydrogen
vehicle.\1\ Hydrogen compressed to 70 MPa at 15 [deg]C has a volumetric
energy density of 4.8 mega Joules per liter (MJ/L), which is similar in
order of magnitude to gasoline's volumetric energy density of 32 MJ/
L.2 3
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\1\ At atmospheric pressure and ambient temperature, hydrogen is
in a gaseous state. The physical state of hydrogen can be changed
from gas to liquid through compression and cryogenic cooling, so
hydrogen can be stored in both compressed gaseous and liquid forms.
However, hydrogen typically exists in gaseous form at essentially
all normal usage and storage temperatures.
\2\ See Patrick Molloy, ``Run on Less with Hydrogen Fuel
Cells.'' RMI, Oct. 2, 2019, https://rmi.org/run-on-less-with-hydrogen-fuel-cells/.
\3\ See Department of Energy Hydrogen and Fuel Cell Technologies
Office, ``Hydrogen Storage,'' https://www.energy.gov/eere/fuelcells/hydrogen-storage.
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While compressed hydrogen is an excellent fuel source due to its
high energy density, its high storage pressure and wide limits of
flammability (i.e., concentrations at which a mixture of fuel and air
is flammable) raise safety concerns. Specifically, hydrogen is
flammable at concentrations ranging from 4 to 75 percent, by volume.\4\
By contrast, gasoline limits of flammability when mixed with air are
from 1.0 to 7.6 percent, by volume.\5\ The velocity at which a hydrogen
flame spreads at room temperature and atmospheric pressure is
approximately 200 to 300 cm/s, whereas the velocity with which gasoline
flames spread under the same conditions is approximately 40 cm/
s.6 7 These characteristics make hydrogen fuel sources more
volatile than gasoline, and while NHTSA has existing FMVSS for gasoline
vehicle fuel system integrity, no FMVSS yet apply to hydrogen storage
and fuel systems. In particular, the safe use of hydrogen vehicles lies
in preventing explosion of
[[Page 27504]]
the hydrogen container(s) and preventing leaks from the container(s)
and fuel system which could lead to fire. Given the greater
flammability of compressed hydrogen, safety standards applicable to
their fuel system integrity are not only reasonable, but necessary.
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\4\ See Hydrogen Compared with Other Fuels, https://h2tools.org/bestpractices/hydrogen-compared-other-fuels.
\5\ Id.
\6\ See 6 Things to Remember about Hydrogen vs Natural Gas,
https://www.powereng.com/library/6-things-to-remember-about-hydrogen-vs-natural-gas.
\7\ See Combustion fuels: density, ignition temperature and
flame speed, https://thundersaidenergy.com/downloads/combustion-fuels-density-ignition-temperature-and-flame-speed/.
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Despite the promise offered by hydrogen vehicles, they are still a
diminutive fraction of the fleet. For model year 2022, there were two
light hydrogen vehicle models offered for sale in the United States,
whose sales by volume represented approximately 0.03% of the overall
light vehicle fleet. There were no medium-or heavy-duty \8\ hydrogen
vehicles offered for sale in the U.S. during the 2022 model year; \9\
however, manufacturers continue to state their intentions to explore
hydrogen across all fleets.
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\8\ Medium-duty vehicles have a gross vehicle weight rating
(GVWR) greater than 4,536 kg and less than or equal to 11,793 kg.
Heavy-duty vehicles have a GVWR greater than 11,793 kg.
\9\ Toyota has a commercial bus called the Sora that is
currently sold in Japan and Europe.
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2. Hydrogen Vehicle Systems
Hydrogen vehicles--both fuel cell and ICE--share the same basic
structure. Hydrogen enters the vehicle through the fueling receptacle,
is stored in the CHSS, and is released from the CHSS as needed to power
either the combustion engine or fuel cell where the energy stored in
hydrogen is converted into mechanical.\10\ Figure-1 below shows an
example of a hydrogen fuel cell vehicle (HFCV).\11\ A diagram of the
main elements of a vehicle fuel system is shown in Figure-2.\12\
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\10\ The chemical energy stored in the hydrogen fuel is
converted into electric energy by the fuel cell, and the resulting
electric energy is then be converted into mechanical energy by
electric drive motor(s), thereby propelling the vehicle.
\11\ Note that the vehicle depicted is a fuel cell vehicle. For
a hydrogen ICE vehicle, the fuel cell would be replaced with a
combustion engine.
\12\ Figure-2 shows the main elements of a HFCV fuel system. In
the case of a hydrogen ICE vehicle, the fuel cell system would be
replaced by the ICE, and the electric propulsion management system
would be replaced by the vehicle powertrain.
[GRAPHIC] [TIFF OMITTED] TP17AP24.000
Figure-1: Example of a HFCV Design 13
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\13\ For further information on HFCV design, see https://afdc.energy.gov/vehicles/fuel_cell.html, and https://afdc.energy.gov/vehicles/how-do-fuel-cell-electric-cars-work.
[GRAPHIC] [TIFF OMITTED] TP17AP24.001
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Figure-2: A Schematic of a HFCV and Its Major Systems
a. CHSS
During fueling, hydrogen is supplied from the fueling station to
the vehicle through the vehicle's fueling receptacle. The hydrogen then
flows to the CHSS for storage in the hydrogen container(s). The key
functions of the CHSS are to receive compressed hydrogen through a
check valve during fueling, contain the hydrogen until needed, and
release hydrogen through an electrically activated shut-off valve to
the hydrogen delivery system for use in powering the vehicle. The check
valve prevents reverse flow in the vehicle fueling line. The shut-off
valve between the storage container and the vehicle fuel delivery
system controls the fuel flow out of the CHSS and automatically
defaults to the closed fail-safe position when unpowered. In the event
of a fire impinging on the CHSS, the TPRD provides a controlled release
of hydrogen from the CHSS before the high temperature causes a
hazardous burst of the container.
b. Hydrogen Delivery
The hydrogen delivery system transfers hydrogen from the CHSS to
the fuel cell system at the proper pressure and temperature for fuel
cells to operate. This transfer process is accomplished through a
series of flow control valves, pressure regulators, filters, piping,
and heat exchangers.
c. Fuel Cell System
The fuel cell system provides high-voltage electric power to the
drive-train and vehicle batteries and capacitors. The fuel cell stack
is the electricity-generating component of the fuel cell system.
Individual fuel cells are electrically connected in series such that
their combined voltage is between 300 and 600 Volts in direct current
(VDC). Fuel cell stacks operate at high-voltage, which means a voltage
greater than 60 VDC. The high voltage aspect of fuel cells are covered
by FMVSS No. 305, ``Electric-powered vehicles: electrolyte spillage and
electrical shock protection,'' and are not considered in this proposal.
A typical fuel cell system includes a blower to feed air to the
fuel cell system. Most of the hydrogen that is supplied to the fuel
cell system is consumed within the fuel cells, but a tiny excess of
hydrogen is required to ensure that there is no damage to the fuel cell
from a lack of hydrogen, which can cause undesired chemical reactions
that damage and degrade the fuel cell.\14\ The excess hydrogen is
either catalytically removed or vented to the atmosphere in accordance
with the requirements discussed below. A fuel cell system also includes
auxiliary components to remove heat. Most fuel cell systems are cooled
by a mixture of glycol and water. Pumps circulate the coolant between
the fuel cells and a radiator.
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\14\ A lack of hydrogen in a fuel cell, also known as hydrogen
starvation, occurs when hydrogen fuel is exhausted at the fuel cell
anode. This condition can lead to undesired chemical reactions
occurring inside the fuel cell which can quickly degrade the fuel
cell's catalyst and other components.
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d. Electric Propulsion and Power Management System
The electric power generated by the fuel cell system is supplied to
the electric propulsion power management system where it is used to
power the electric drive-train that propels the vehicle. The throttle
position is used by the drive-train controllers to determine the amount
of power to be sent to the drive wheels. Many HFCVs use batteries or
ultra-capacitors to supplement the output of the fuel cells. These
vehicles may also recapture energy during braking through regenerative
braking, which recharges the batteries or ultra-capacitors and thereby
maximizes efficiency.\15\
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\15\ The electric propulsion and power management system is
covered by FMVSS No. 305, ``Electric-powered vehicles: electrolyte
spillage and electrical shock protection,'' and is not considered in
this proposal.
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e. Hydrogen ICE Vehicles
Hydrogen ICE vehicles have an ICE instead of a fuel cell system.
The ICE engine burns hydrogen to generate mechanical energy to propel
the vehicle. These vehicles use a mechanical propulsion system instead
of an electric propulsion system.
B. Global Technical Regulation (GTR) No. 13
The proposed rule initiates the process of adopting Global
Technical Regulation (GTR) No. 13 into the FMVSS. Based on GTR No. 13,
this NPRM proposes requirements for the safe onboard storage and
utilization of hydrogen in vehicles.
1. Overview of the GTR Process
The United States became the first signatory to the 1998 United
Nations/Economic Commission for Europe (UNECE) agreement (1998
Agreement). The 1998 Agreement entered into force in 2000 and is
administered by the World Forum for Harmonization of Vehicle
Regulations working party (WP.29).\16\ The 1998 Agreement established
the development of global technical regulations (GTRs) regarding the
safety, emissions, energy efficiency and theft prevention of wheeled
vehicles, equipment and parts.
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\16\ The World Forum was initially named the Working Party on
the Construction of Vehicles, a subsidiary of the Inland Transport
Committee. It was renamed to the World Forum in 2000.
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The 1998 Agreement contains procedures for establishing GTRs either
through harmonizing existing regulations or developing new regulations.
The GTR process provides NHTSA unique opportunities to enhance vehicle
safety and improve government efficiency. It assists in developing the
best safety practices from around the world, identifying and reducing
unwarranted regulatory requirements, and leveraging scarce government
resources for research and regulation. The process facilitates our
effort to continuously improve and seek high levels of safety,
particularly by helping us develop regulations that reflect a global
consideration of current and anticipated technology and safety
problems.
Contracting Parties who vote in favor of a GTR are obligated by the
1998 Agreement to ``submit the technical Regulation to the process''
used in the country to adopt the requirement into the agency's law or
regulation.\17\ In the U.S., that process usually commences with an
NPRM or Advance NPRM (ANPRM). The 1998 Agreement does not obligate
Contracting Parties to adopt the GTR after initiating this process.\18\
The 1998 Agreement recognizes that governments have the right to
determine whether the global technical regulations established under
the Agreement are suitable for their own particular safety needs. Those
needs vary from country to country due to differences in laws and in
factors such as the traffic environment, vehicle fleet composition,
driver characteristics and seat belt usage rates.
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\17\ Article 7, 1998 Agreement, available at https://unece.org/text-1998-agreement.
\18\ Id.
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2. History of GTR No. 13
NHTSA began collaborating with the international community to
develop a global technical regulation for hydrogen vehicles in the
early 2000s. In 2005, WP.29 agreed to a proposal from Germany, Japan
and the United States of America regarding how best to manage the
development process for a hydrogen vehicle GTR. Pursuant to the
proposal, the United States and Japan were designated co-chairs of an
informal
[[Page 27506]]
working group (IWG) to explore the safety aspects of hydrogen vehicles.
In June 2007, WP.29 adopted an action plan prepared by the co-
sponsors to develop a GTR for compressed gaseous and liquefied hydrogen
fuel vehicles. At the time, no hydrogen vehicles were commercially
available. To allow for the advancement of hydrogen technologies, the
co-sponsors' action plan split the GTR into two phases. Phase 1 would
focus on developing a GTR for hydrogen vehicles based on current best
practices. Phase 2 would commence subsequent to Phase 1, and supplement
it by assessing any technological advancements and explore ways to
harmonize vehicle crash tests to evaluate fuel system integrity.
The IWG evaluated existing research and design standards for the
development of a hydrogen vehicle GTR. To the extent possible, the
group avoided design specific requirements and considered requirements
and specification that were supported by research and technically
justified. The main areas of focus in Phase 1 were: performance
requirements for hydrogen storage systems, high-pressure closures,
pressure relief devices, and fuel lines; specifications on limits on
hydrogen releases during normal vehicle operations and post-crash; and
requirements for electrical isolation and protection against electric
shock during normal vehicle operations and post-crash.
The draft GTR was recommended by the IWG at the December 2012
session, and GTR No. 13 for Hydrogen and Fuel Cell Vehicles was
codified by WP.29 on June 27, 2013, after a 6-year effort, with the
United States voting in favor of the GTR. It specified safety-related
performance requirements and test procedures with the purpose of
minimizing human harm that may occur as a result of fire, burst, or
explosion related to the hydrogen fuel system of vehicles, and/or from
electric shock caused by a fuel cell vehicle's high voltage power train
system.\19\ The regulation consists of system performance requirements
for compressed hydrogen storage systems (CHSS), CHSS closure devices,
and the vehicle fuel delivery system. In Phase 1, the IWG purposefully
did not harmonize crash tests and instead elected to have Contracting
Parties use their own methodologies.
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\19\ The electrical safety requirements in GTR No. 13 Phase 1
were incorporated into FMVSS No. 305. See 82 FR 44945.
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Phase 2 was adopted at the 190th Session of WP.29 on June 21,
2023.\20\ Phase 2 accomplished several goals, including: broadening of
the scope and application of GTR No. 13 to cover heavy-duty/commercial
vehicles; harmonizing, clarifying, and expanding the requirements for
thermal-pressure relief devices' direction in case of controlled
release of hydrogen; strengthening test procedures for containers with
pressures below 70 MPa, including comprehensive fire exposure tests;
and extending the requirements to 25 years to more accurately capture
the expected useful life of vehicles. The U.S. voted in favor of
adopting Phase 2 and is proposing to adopt the changes made to GTR No.
13 by Phase 2 with this proposal.
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\20\ A copy of GTR No. 13 as updated by the Phase 2 amendments
is available at: https://unece.org/sites/default/files/2023-07/ECE-TRANS-180-Add.13-Amend1e.pdf.
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III. Why is NHTSA issuing this proposal?
As a Contracting Party who voted in favor of GTR No. 13, the United
States is obligated under the 1998 Agreement to ``submit the technical
Regulation to the process'' used to adopt the requirement into the
agency's law or regulation as a domestic standard. Today's proposal
satisfies that obligation. In deciding whether to adopt a GTR as an
FMVSS, we follow the procedural and substantive requirements for any
other agency rulemaking, including the Administrative Procedure Act,
the National Traffic and Motor Vehicle Safety Act (Safety Act) (49
U.S.C. Chapter 301), Presidential executive orders, and DOT and NHTSA
policies, procedures, and regulations.\21\ Under 49 U.S.C. 30111(a),
FMVSSs must be practicable, meet the need for motor vehicle safety, and
be stated in objective terms.\22\ Section 30111(b) states that, when
prescribing such standards, NHTSA must, among other things, consider
all relevant, available motor vehicle safety information; consider
whether a standard is reasonable, practicable, and appropriate for the
types of motor vehicles or motor vehicle equipment for which it is
prescribed; and consider the extent to which the standard will further
the statutory purpose of reducing traffic crashes and associated deaths
and injuries.
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\21\ NHTSA's policies in implementing the 1998 Agreement are
published in 49 CFR part 553, appendix C, ``Statement of Policy:
Implementation of the United Nations/Economic Commission for Europe
(UNECE) 1998 Agreement on Global Technical Regulations--Agency
Policy Goals and Public Participation.'' NHTSA's paramount policy
goal under the 1998 Agreement is to ``[c]ontinuously improve safety
and seek high levels of safety, particularly by developing and
adopting new global technical regulations reflecting consideration
of current and anticipated technology and safety problems.''
\22\ ``Motor vehicle safety'' is defined in the Safety Act as
``the performance of a motor vehicle or motor vehicle equipment in a
way that protects the public against unreasonable risk of accidents
occurring because of the design, construction, or performance of a
motor vehicle, and against unreasonable risk of death or injury in
an accident, and includes nonoperational safety of a motor
vehicle.'' 49 U.S.C. 30102(a)(8).
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This proposal marks a substantial step in meeting those procedural
and substantive requirements. The proposal serves as notice of our
intention to adopt the requirements of GTR No. 13 as FMVSS Nos. 307 and
308 and provides an opportunity for the public to comment on the
proposed requirements. In accordance with the APA, we seek comment on
this proposal to help inform our decision-making, and will take all
timely public comments into consideration when deciding whether (and if
so, how) to proceed with a final rule, and the appropriateness of any
potential modifications to the proposed performance standards that are
appropriately within scope of the NPRM.
NHTSA tentatively finds that the proposed standards fulfill a
clear, if not immediately present, need for motor vehicle safety. The
purpose of FMVSS No. 307, ``Fuel system integrity of hydrogen
vehicles,'' and FMVSS No. 308, ``Compressed hydrogen storage system
integrity,'' is to reduce deaths and injuries in hydrogen-powered
vehicles occurring from fires that result from leakage after motor
vehicle crashes. Hydrogen is highly flammable, with an exceptionally
wide limit of flammability in the air and a high burning velocity. If
hydrogen leaks from the fuel system, the risk of fire in or near the
vehicle is substantial and gravely impairs the safety of vehicle
occupants and others within the vicinity of the vehicle.
Although the potential safety risk from hydrogen vehicles has not
necessarily materialized, due to their current scarcity in the on-road
fleet, NHTSA made the same determination about the safety need for fuel
system and container integrity systems when it adopted FMVSS No. 301,
Fuel system integrity, with the initial FMVSSs adopted in 1968,\23\ and
in 1994 when NHTSA adopted FMVSS No. 303, Fuel system integrity of
compressed natural gas vehicles,\24\ and FMVSS No. 304, Compressed
natural gas fuel container
[[Page 27507]]
integrity.\25\ NHTSA faced a similar crossroads when developing FMVSS
Nos. 303 and 304. Compressed Natural Gas (CNG) vehicles represented a
very small portion of the total fleet size when NHTSA finalized the
standards. The agency decided that the safety risk posed by CNG
necessitated immediate action.\26\ Members of the public shared a
similar sentiment with the agency and urged quick action at that time
to coalesce safety practices.\27\ Today's proposal is the logical
extension of NHTSA's existing standards that cover vehicles powered by
other combustible fuel sources, except, for this NPRM, the agency has
been able to draw on and benefit from the work of the international GTR
No. 13 community in developing the proposed standards.
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\23\ See 32 FR 2414 (February 3, 1967).
\24\ See 59 FR 19648 (April 25, 1994).
\25\ See 59 FR 49010 (September 26, 1994).
\26\ 58 FR 5323 (January 23, 1993)
\27\ See 59 FR 19648, 19657.
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We tentatively find the proposed requirements in this NPRM to be
practicable. Both automobile and hydrogen container manufacturers
provided technical expertise to the IWG on test procedures and
determining the boundaries of practicability of requirements during the
development of GTR No. 13. Furthermore, GTR No. 13 incorporates a
number of voluntary industry standards, which are discussed throughout
this preamble, that have been demonstrated as practicable. Given the
industry input informing the GTR and that the GTR incorporates current
technical standards now used in hydrogen vehicle safety designs, NHTSA
believes that the proposed standards are practicable.
The 1998 Agreement provides flexibilities to propose alternative
technical regulations as necessary to ensure compliance with a
jurisdiction's specific legal and safety need requirements. As noted in
the forthcoming sections, NHTSA is proposing several modifications to
the requirements in GTR No. 13 to conform with the Safety Act
requirements for FMVSS, clarify the wording of the regulation, and
improve objectivity.
The agency believes that this proposed rule is timely. While
hydrogen vehicles currently represent less than half a percent of the
total sales of light vehicles and are still in the prototypical stage
for heavier vehicles, there are several trends that may point to
increased growth in the coming years. The slow adoption of hydrogen
vehicles can be attributed to both the expense associated with
developing a new powertrain and the lack of existing fueling
infrastructure.\28\ Recent Federal legislation and spending has renewed
the country's focus on incentivizing clean vehicles. The Inflation
Reduction Act (IRA) allotted billions towards the development of clean
vehicles and the infrastructure to support them. Manufacturers can
claim credits for building or retooling facilities to build hydrogen-
powered vehicles under Qualifying Advanced energy project credit or can
claim credits for each hydrogen vehicle produced pursuant to the
Advanced manufacturing production credit.\29\ Consumers who purchase
hydrogen vehicles can qualify for a $7,500 tax credit, and commercial
enterprises can claim up to $40,000 for hydrogen fuel cell
vehicles.\30\ Additionally, producers of clean hydrogen are also
eligible for tax credits on a per-gallon basis.\31\ This list of
incentives is not exhaustive, and NHTSA recognizes that the collective
efforts at both the Federal and State level to incentive clean energy
in the transportation industry are extensive and underline the
importance of establishing safety standards presently, so that they are
in place as the vehicles arrive in the marketplace.
---------------------------------------------------------------------------
\28\ See, e.g. S. Hardman, E. Shiu, R. Steinberger-Wilckens, and
T. Turrentine., Barriers to the adoption of fuel cell vehicles: A
qualitative investigation into early adopters attitudes, 95
Transportation Research Part A: Policy and Practice 166-82 (2017).
https://www.sciencedirect.com/science/article/abs/pii/
S0965856415302408#:~:text=FCVs%20have%20some%20specific%20challenges,
and%20balance%20of%20plant%20components.
\29\ See 26 U.S.C. 48C and 26 U.S.C. 45X, respectively.
\30\ See 26 U.S.C. 30D and 26 U.S.C. 45W, respectively.
\31\ 26 U.S.C. 45Z.
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Manufacturers continue to announce new forays into hydrogen
vehicles, with some manufacturers citing the IRA as a catalyst for
further development of hydrogen-powered vehicles.\32\ Hyundai and
Toyota, the only two manufacturers with hydrogen vehicles for sale
currently in the United States, have announced plans to introduce more
consumer hydrogen vehicle lines covering additional body styles and
expand their hydrogen vehicle offerings.\33\ Other manufacturers have
announced plans to introduce their own hydrogen vehicle models,\34\ and
new entrants to the automotive market are testing prototypes and
concept vehicles.\35\ Manufacturers have also stated that they are
exploring the viability of hydrogen heavy-duty vehicles.\36\
---------------------------------------------------------------------------
\32\ See, e.g. Elizabeth Sturcken, ``Leading companies are using
IRA tax credits for clean manufacturing and technology. Are you?''
Environmental Defense Fund, June 7, 2023, https://business.edf.org/insights/leading-companies-are-using-ira-tax-credits-for-clean-manufacturing-and-technology-are-you/.
\33\ See Remeredzai J. Kuhadzai, ``Toyota Hilux Hydrogen Fuel
Cell Pickup Prototype Unveiled'' https://cleantechnica.com/2023/01/11/toyota-starts-work-on-the-development-of-prototype-hydrogen-fuel-cell-toyota-hilux-pickup/ (Toyota plans to release the Helix only in
Japan for the upcoming model year) and Toyota, ``PACCAR and Toyota
Expand Hydrogen Fuel Cell Truck Collaboration to Include
Commercialization.'' May 2, 2023, https://pressroom.toyota.com/paccar-and-toyota-expand-hydrogen-fuel-cell-truck-collaboration-to-include-commercialization/; see also Michelle Thompson, ``Hyundai
hires new exec to help lead hydrogen initiatives.'' Repairer Driven
News, June 29, 2023. https://www.repairerdrivennews.com/2023/06/29/hyundai-hires-new-exec-to-help-lead-hydrogen-initiatives/.
\34\ For example, see Ken Silverstein, ``Electric Vehicles or
Hydrogen Fuel Cell Cars? The Inflation Reduction Act Will Fuel
Both.'' Forbes, Aug. 10, 2022, https://www.forbes.com/sites/kensilverstein/2022/08/10/electric-vehicles-or-hydrogen-fuel-cell-cars-the-inflation-reduction-act-will-fuel-both/?sh=2841d7634d01;
see also Joey Capparella, ``Hydrogen-Powered Honda CR-V to Be Built
in the U.S. Starting in 2024.'' Car and Driver, Nov. 30, 2022.
\35\ See, Ezra Dyer, ``Pininfarina Reveals Pura Vision SUV
Concept.'' Car and Driver, Aug. 1, 2023, https://www.caranddriver.com/news/a44690183/pininfarina-pura-vision-suv-concept-revealed/.
\36\ See Rebecca Martineau, ``Fast Flow Future for Heavy-Duty
Hydrogen Trucks: Expanded Capabilities at NREL Demonstrate High-
Flow-Rate Hydrogen Fueling for Heavy-Duty Applications.'' National
Renewable Energy Laboratory, June 8, 2022, https://www.nrel.gov/news/program/2022/fast-flow-future-heavy-duty-hydrogen-trucks.html.
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NHTSA faced a similar crossroads when developing FMVSS Nos. 303 and
304. Compressed Natural Gas (CNG) vehicles represented a very small
portion of the total fleet size when NHTSA finalized the standards. The
agency decided that the safety risk posed by keeping CNG at a high
pressure necessitated an immediate action.\37\ Members of the public
have shared a similar sentiment with the agency and urged quick action
to coalesce safety practices for hydrogen powered vehicles.\38\
---------------------------------------------------------------------------
\37\ 58 FR 5323.
\38\ See 59 FR 19648, 19657.
---------------------------------------------------------------------------
We believe that the proposed standards would provide regulatory
certainty for manufacturers. Given manufacturers' purported interest in
expanding their hydrogen offerings and the IRA incentives reducing the
comparative costs of hydrogen vehicles, adopting safety regulations now
would provide manufacturers clarity on how to design new vehicle lines.
Further, having hydrogen safety standards in place should assist in
alleviating the trepidation consumers have of newer technologies,
whereas a failure to adequately address safety concerns in the earliest
stages of development could have a negative impact on the deployment of
this new technology. Manufacturers have also informed
[[Page 27508]]
NHTSA that they would like to see the agency coordinate and harmonize
hydrogen standards with other nations.\39\ This proposal would
accomplish all of these tasks.
---------------------------------------------------------------------------
\39\ See, e.g. NHTSA-2004-18039-0020 at 17.
---------------------------------------------------------------------------
IV. Overview of Proposed Safety Standards
The safe use of compressed hydrogen in vehicles lies primarily in
preventing explosion of the hydrogen container(s) and preventing fuel
leaks which could lead to fire or explosion. The leakage of hydrogen
from the fuel system during normal vehicle operations and post-crash
can pose safety hazards (fire or explosion) to vehicle occupants and
the surroundings. In order to address the fire and explosion hazards
associated with hydrogen vehicles, NHTSA is proposing to set
performance requirements for the CHSS and the overall fuel system that
are generally consistent with GTR No. 13.
GTR No. 13, Section 5.1, ``Compressed hydrogen storage system,''
specifies performance-based CHSS requirements which address documented
on-road stress factors. These stress factors include those identified
in CNG vehicle containers as well as those that are unique to
containment of high-pressure hydrogen. These requirements were
developed to demonstrate the CHSS's capability to perform critical
functions throughout service, including fueling/defueling events,
parking under extreme vehicle and environmental conditions,
environmental exposures, and performance in fire without explosion.
GTR No. 13, Section 5.2, ``Vehicle fuel system,'' includes
performance requirements to prevent and mitigate hydrogen leak from the
fuel system and to warn vehicle occupants in the event of hydrogen
concentration in the vehicle above flammable limits during normal
vehicle operations and post-crash.
Similar to how NHTSA originally established CNG standards, we are
proposing to implement GTR No. 13 by establishing two new FMVSSs that
would specify minimum performance standards for vehicles that use
compressed hydrogen gas as a motor fuel.\40\ FMVSS No. 308,
``Compressed hydrogen storage system integrity,'' would set out
requirements for CHSS integrity. FMVSS No. 307, ``Fuel system integrity
of hydrogen vehicles,'' would set out in-use and post-crash
requirements for the overall fuel system, including the CHSS, hydrogen
delivery system, and fuel cell.
---------------------------------------------------------------------------
\40\ The standards proposed in this document would not apply to
vehicles that use liquified hydrogen as a motor fuel.
---------------------------------------------------------------------------
NHTSA is proposing that FMVSS Nos. 307 and 308 apply to all
hydrogen-powered vehicles. This is a departure from Phase 1 of GTR No.
13 which only applies to hydrogen powered light vehicles. As discussed
below, the IWG of GTR No. 13 Phase 2 has expanded the applicability of
the standard to hydrogen powered heavy vehicles. With the exception of
crash tests for heavy vehicles, NHTSA finds that the technical
standards in GTR No. 13 are practicable for heavy vehicles and address
the same safety need found in light vehicles.
Note that, consistent with GTR No. 13, NHTSA is proposing that
FMVSS No. 308 be a vehicle-level standard, rather than an equipment
standard.\41\ Some performance requirements and test procedures for the
CHSS in FMVSS No. 308 are specific to the vehicle design and to its
gross vehicle weight rating. NHTSA is aware this is a departure from
FMVSS No. 304 that is an equipment standard which applies to CNG
containers sold as replacement parts for CNG vehicles. At this time,
hydrogen vehicle manufacturers are strictly controlling the CHSS
installed in their vehicles and replacement parts are obtained from the
vehicle manufacturer (similar to electric vehicle batteries). NHTSA
will monitor the deployment of hydrogen vehicles and how consumers are
replacing parts of the fuel system. Since such data is lacking at this
time, NHTSA is proposing FMVSS No. 308 as a vehicle standard,
consistent with GTR No. 13. NHTSA will re-evaluate this decision based
on comments received and on field data on hydrogen vehicle deployment,
repair, and replacement parts. NHTSA seeks comment on whether FMVSS No.
308 should remain a vehicle standard, as well as whether FMVSS Nos. 307
and 308 should be combined into a single standard in the final rule.
---------------------------------------------------------------------------
\41\ This is in contrast to FMVSS No. 304, Compressed natural
gas fuel container integrity, which is an equipment standard.
---------------------------------------------------------------------------
A. FMVSS No. 308, ``Compressed Hydrogen Storage System Integrity''
FMVSS No. 308 would set out requirements for the performance of the
CHSS and its subcomponents during normal use, with a particular focus
on how the CHSS performs in a variety of incidents that a vehicle could
experience during its lifetime operations and how well the component
withstands usage.
NHTSA is proposing that FMVSS No. 308 only be a vehicle standard.
As explained in more detail below, some of the proposed requirements
are conditional on the vehicle type and characteristics. Without the
knowledge of the relevant vehicle, some of the proposed CHSS standards
cannot be tested. For these reasons, NHTSA does not intend that the
proposed standard should extend to cover replacement parts, even though
they would be considered motor vehicle equipment and still subject to
NHTSA's safety defect authority, and replacement parts when installed
may not take the vehicle out of compliance with the proposed new FMVSS
No. 308, per 49 U.S.C. 30122. NHTSA seeks comment on this approach.
1. Compressed Hydrogen Storage System
The CHSS is defined to include all closure surfaces that provide
primary containment of high-pressure hydrogen storage. The CHSS is
defined to include the hydrogen container, check valve, shut-off valve
and thermally-activated pressure relief device (TPRD), which are
discussed in the sections below. Figure-3 illustrates a typical CHSS.
[GRAPHIC] [TIFF OMITTED] TP17AP24.002
Figure-3: Typical CHSS
a. Hydrogen Container
The hydrogen container is the main component of a CHSS. The
hydrogen container stores hydrogen at extremely high pressure. On
current hydrogen vehicles, hydrogen has typically been stored at a
nominal working pressure (NWP) of 35 MPa or 70 MPa, at 15 [deg]C. NWP
means the gauge pressure that characterizes the normal operation of the
system. Typically, the container is designed for a maximum allowable
gas temperature of 85 [deg]C. If the temperature of hydrogen stored at
NWP is increased from 15 [deg]C to 85 [deg]C, then the pressure inside
the container will rise to the maximum allowable pressure of 25
[[Page 27509]]
percent above NWP.\42\ A container may consist of a single chamber or
multiple permanently interconnected chambers. This allows designers
flexibility in the overall shape of the CHSS.
---------------------------------------------------------------------------
\42\ This is based on data published in the NIST Chemistry
WebBook, Standard Reference Database Number 69, Thermophysical
Properties of Fluid Systems (isochoric properties for hydrogen),
available at https://webbook.nist.gov/chemistry/fluid/.
---------------------------------------------------------------------------
Most containers used in hydrogen vehicles consist of two layers.
The inner liner prevents gas leakage/permeation and is usually made of
metal or thermoplastic polymer. The outer layer provides structural
integrity and is usually made of metal or thermoset resin-impregnated
fiber-reinforced composite. For instance, Type 3 containers consist of
a metal liner reinforced with resin impregnated continuous filament,
and Type 4 containers consists of a non-metallic liner with resin-
impregnated continuous filament.\43\
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\43\ The American National Standard for Compressed Natural Gas
Fuel Vehicle Containers (2007) classifies containers into Types 1
through 4 as follows:
Type 1--Metal.
Type 2--Resin impregnated continuous filament with metal liner
with a minimum burst pressure of 125 percent of service pressure.
This container is hoop-wrapped.
Type 3--Resin impregnated continuous filament with metal liner.
This container is full-wrapped.
Type 4--Resin impregnated continuous filament with a non-
metallic liner.
---------------------------------------------------------------------------
GTR No. 13 defines a container as ``the pressure-bearing component
on the vehicle that stores the primary volume of hydrogen fuel in a
single chamber or in multiple permanently interconnected chambers.''
NHTSA is proposing a similar definition with the following
modifications:
Replace ``the vehicle'' with ``a compressed hydrogen
storage system'' to clarify that the container is a subcomponent of the
CHSS, and therefore a container cannot exist on its own without the
other components of the CHSS.
Remove the word ``primary'' because this introduces
ambiguity regarding secondary or tertiary volumes of hydrogen.
Add the word ``continuous'' to clarify that a container
does not have any valves or other obstructions that may separate its
different chambers.
Thus, NHTSA's proposed definition for ``container'' would be
``pressure-bearing component of a compressed hydrogen storage system
that stores a continuous volume of hydrogen fuel in a single chamber or
in multiple permanently interconnected chambers.'' These changes are
intended to clarify the definition and provide greater regulatory
certainty as to what is considered part of the container. The changes
do not alter the substantive requirements. NHTSA seeks comment on the
proposed definition for the container.
b. Closure Devices
GTR No. 13 refers to closure devices as ``primary'' closure
devices. This creates ambiguity about potential secondary or tertiary
closure devices. As a result, NHTSA will refer simply to ``closure
devices.'' NHTSA therefore proposes to define the term ``closure
devices'' as ``the check valve(s), shut-off valve(s) and thermally
activated pressure relief device(s) that control the flow of hydrogen
into and/or out of a CHSS,'' so it will be clear what components are
covered under the standard. NHTSA seeks comment on removal of the word
``primary'' and on the proposed definition for ``closure devices.''
(1) TPRD
In the event of a fire, the TPRD provides a controlled release of
hydrogen from the container before the high temperature from the fire
weakens the container and causes a hazardous burst. TPRDs are designed
to vent the entire hydrogen content of the container rapidly. These
devices are designed to not be reset or reused once they have been
activated.
(2) Check Valve
During fueling, hydrogen enters the CHSS through a check valve. The
check valve prevents back-flow of hydrogen into the fueling line or out
of the fueling receptacle.
(3) Shut-Off Valve
A shut-off valve prevents the outflow of stored hydrogen from the
container when the vehicle is not operating or when a fault is detected
that requires isolation of the CHSS. In GTR No. 13, the shut-off valve
is defined as ``a valve between the container and the vehicle fuel
system that must default to the `closed' position when not connected to
a power source.'' NHTSA proposes adding the words ``electrically
activated'' to the definition, so that a shut-off valve would be ``an
electrically activated valve between the container and the vehicle fuel
system that must default to the `closed' position when not connected to
a power source.'' NHTSA seeks comment on the proposed definition of
shut-off valve.
(4) Container Attachments
The CHSS may include container attachments, which are non-pressure
bearing parts attached to the container that provide additional support
and/or protection to the container. Container attachments may only be
removed with the use of tools for the purpose of maintenance and/or
inspection. Container attachments include devices such as bump stops to
mitigate impacts or shielding to mitigate surface damage to the
container.
In the GTR No. 13 test procedures, container attachments are
included in some tests. Importantly, in some cases, the container
attachments provide protection to the container that improves test
performance. Including container attachments for testing is discussed
in the sections below where applicable and where the container
attachments may affect test performance.
NHTSA proposes defining container attachments as ``non-pressure
bearing parts attached to the container that provide additional support
and/or protection to the container and that may be removed only with
the use of tools for the specific purpose of maintenance and/or
inspection.'' NHTSA seeks comment on the proposed definition of
container attachments. In this definition, the word ``temporarily'' has
been removed from the GTR definition because anything that can be
removed temporarily can also be removed permanently. For clarity, NHTSA
has also shifted the order of some words relative to the definition in
GTR No. 13.
2. General Requirements for the CHSS
NHTSA is proposing that the CHSS be required to include the
functionality of a TPRD, shut-off valve, and check valve. These
functions are required for the reasons stated above. However, NHTSA is
aware of CNG vehicles that do not include check valves as part of their
CNG storage system. In such CNG vehicles, the check valves are
installed upstream between the fueling port and the CNG container, with
additional valves to contain high pressure gas. NHTSA seeks comment on
whether the check valves should be required as part of the CHSS.
The CHSS would be required to have an NWP of 70 MPa or less. This
is because working pressures above 70 MPa are currently considered
impractical and may pose a safety risk given current known
technologies. The energy density of hydrogen does not increase
significantly when pressurized above 70 MPa, so there is no significant
improvement in hydrogen storage efficiency at pressures above 70 MPa.
Pressures above 70 MPa, however, may present a greater safety hazard.
As a result, NHTSA proposes that all CHSS
[[Page 27510]]
must have an NWP less than or equal to 70 MPa. NHTSA seeks comment on
this requirement, and specifically asks commenters to identify any
technologies that can safely store hydrogen at pressures above 70 MPa.
GTR No. 13 provided contracting parties with the discretion to
require that the closure devices be mounted directly on or within each
container. The relevant safety concern is that the high-pressure lines
required to connect remotely-located closure devices with the container
could be susceptible to damage or leak. However, the definition of a
container is sufficiently broad that it includes such lines as part of
the container. These lines will be considered part of the permanently
interconnected chambers storing the continuous volume of hydrogen.
Thus, any lines connecting to closure devices are themselves part of
the container and will be included in the extensive container
performance testing discussed below. If a container (which includes any
lines connecting to closure devices) can successfully complete the
performance testing in FMVSS No. 308, then the risk of failure of the
lines has been addressed. Therefore, NHTSA tentatively concludes that
it is not necessary to specify that closure devices be mounted directly
on or within each container. NHTSA is also concerned that such a
specification would be design restrictive. NHTSA is aware of CNG fuel
systems where the closure devices are neither on nor within each
container, and there have been no reported safety issues with such
systems. Therefore, NHTSA is not proposing to include a requirement for
closure devices to be on or within each container, and would instead
leave the location of closure devices to manufacturer discretion. NHTSA
seeks comment on requiring closure devices to be mounted directly on or
within each container.
3. Performance Requirements for the CHSS
The CHSS would be required to meet specific performance
requirements when subjected to the performance tests listed below. The
performance tests and the respective performance requirements are
discussed in detail in subsequent sections:
Tests for baseline metrics
Test for performance durability
Test for expected on-road performance
Test for service terminating performance in fire
Tests for performance durability of closure devices
Several of these tests utilize a manufacturer-supplied value known
as BPO. A container's BPO is a design parameter
specified by the manufacturer to establish the expected initial burst
pressure of the container. It is NHTSA's understanding that
BPO, associated with median or midpoint burst pressure for a
batch of containers, can vary between batches of containers. Therefore,
in order to facilitate compliance testing, NHTSA is proposing that
manufacturers specify the BPO associated with each container
on the required container label (discussed below). NHTSA seeks comment
on this labeling requirement, noting that it is not required by GTR No.
13.
4. Tests for Baseline Metrics
The container must be able to withstand high pressurization, as
well as pressure cycling, which is a repeated pressurization and
depressurization. Both of these stress factors occur during the service
life of the vehicle as its fuel system is repeatedly depleted and
refilled. Consistent with GTR No. 13, the proposed tests for baseline
metrics would include two tests for the container: the baseline initial
burst pressure test to evaluate resistance to burst at high pressure,
and the baseline initial pressure cycle test to ensure the container is
designed to leak before burst \44\ and to evaluate its ability to
withstand pressure cycling without burst and without leakage within its
service life.
---------------------------------------------------------------------------
\44\ Leak before burst design of high pressure containers is a
common safety feature to ensure a leak will develop before a
catastrophic burst will occur. A leak is a less severe failure mode
compared to a catastrophic burst of the high pressure container.
---------------------------------------------------------------------------
During the initial burst pressure test, the container must
demonstrate that as the pressure is increased inside the container, the
point of failure is above a minimum pressure level, discussed below. In
other words, the container must demonstrate a minimum burst pressure.
Burst pressure is defined as the highest pressure reached inside a
container during a burst test which results in structural failure of
the container and resultant fluid loss through the container, not
including gaskets or seals. Burst pressure is determined by the
baseline initial burst pressure test discussed below.
During the baseline initial pressure cycle test, the container must
withstand pressure cycling that simulates repeated fueling and
defueling by increasing the pressure inside the container to a high
pressure level, then depressurizing it to low pressure, and repeating
that process for a set number of cycles. The container must neither
leak nor burst during an initial set of pressure cycles, and must not
burst during a set number of pressure cycles beyond the initial set.
These requirements are evaluated by the baseline pressure cycle life
test discussed below.
The physical forces on the load-bearing components of a container
are the same regardless of whether the pressure is being applied with
hydraulic fluid, hydrogen gas, or any other medium. Therefore, for
practicability and safety purposes both tests would be conducted using
hydraulic fluid to exert pressure inside the container.\45\ Hydraulic
fluids, such as water or water with additives, are advantageous for
these tests because they reduce the explosion risk associated with
pneumatic pressurization. The explosion risk from pneumatic
pressurization is high because compression of gas stores pressure-
volume energy (PV energy), whereas during hydraulic pressurization with
an incompressible fluid, PV energy is negligible. In addition, the
incompressible nature of hydraulic fluids means that pressure cycles
can be accomplished much faster than pneumatic pressurization cycles.
This is important given the high number of cycles required for the
baseline pressure cycle test. The use of hydrogen gas pneumatic
pressure cycling does introduce stress factors beyond basic
pressurization/depressurization, as discussed later, and these are
addressed separately in the test for expected on-road performance.
Given that hydraulic pressure cycling provides these benefits without
compromising the safety or stringency of the proposed standards,
hydraulic pressure cycling is used for these tests.
---------------------------------------------------------------------------
\45\ This is consistent with GTR No. 13.
---------------------------------------------------------------------------
a. Baseline Initial Burst Pressure
The baseline initial burst pressure test verifies that the initial
burst pressure of a container is both above a minimum specified
pressure level and is within 10 percent of the manufacturer specified
BPO. The requirement that the container tested must have a
burst pressure within 10 percent of BPO is based
on the need to control variability in container production. If a
manufacturing process produces containers with highly variable initial
burst pressures, there is a possibility of a container with a
dangerously low burst pressure. NHTSA seeks comment on the safety need
for specifying a limit on burst pressure variability in a batch and
whether the 10 percent limit is appropriate; if commenters believe
another limit is
[[Page 27511]]
appropriate, they are asked to provide supporting data.
The minimum burst pressure, BPmin, in GTR No. 13 Phase 1
was set at 225 percent of NWP for carbon fiber composite containers,
and 350 percent NWP for glass fiber composite containers. The value for
carbon fiber composite containers was chosen to be a conservative
starting point based on experience from CNG vehicles. GTR No. 13 Phase
1 made clear that the burst pressure requirement would be reviewed in
Phase 2. The IWG of GTR No. 13 Phase 2 did review data on variability
in initial burst pressure and end-of-life burst pressure (i.e., burst
pressure after the test for performance durability, discussed in a
later section), and determined that variation in burst pressure is
actually low and that a minimum initial burst pressure of 200 percent
NWP was appropriate for carbon fiber composite containers.\46\ The GTR
No. 13 Phase 2 IWG assessment also noted that manufacturers generally
design containers to have burst pressures well above the required
minimum burst pressure, to ensure that a container can meet the
performance requirements of the test for performance durability. These
findings suggest it is possible to lower the minimum burst pressure
requirement to 200 percent of NWP without reducing safety, because
manufacturers will generally be outperforming this requirement anyway.
---------------------------------------------------------------------------
\46\ A study was conducted by the Japanese Automobile Research
Institute which evaluated the variability of containers' initial
burst pressure, as well as the variability in end-of-life burst
pressure. The study concluded that variability among the containers
was low, and therefore a minimum initial burst pressure of 200
percent NWP was acceptable and most consistent with the end-of-life
burst pressure requirement.
See GTR No. 13 Phase 2 file GTR13-3-03: https://wiki.unece.org/download/attachments/58525915/GTR13-3-03%20Initial%20burst%20pressure%20requirement%20_3rd%20GTR13%20IWG_June2018.pdf?api=v2.
---------------------------------------------------------------------------
Furthermore, a 200 percent minimum initial burst pressure can be
supported when coupled with the following requirements from the
proposed test for performance durability (which are discussed in the
following section): \47\
---------------------------------------------------------------------------
\47\ The tests conducted by the Japanese Automobile Research
Institute showed that containers with burst pressure which met the
BPO 10 percent requirement and subjected to
the durability sequential tests, were able to withstand the end-of-
life 180 percent NWP for four minutes and have an end-of-life burst
pressure within -20 percent of BPO, even if the minimum
initial burst pressure is reduced to 200 percent NWP.
---------------------------------------------------------------------------
The container must withstand 180 percent NWP for 4 minutes
at the end of the test for performance durability.
The minimum burst pressure after the completion of the
test for performance durability cannot be lower than 80 percent of
BPO.
In light of the variability in the minimum burst pressure and the
need to meet the above two requirements at the end of the test for
performance durability, NHTSA expects that manufacturers will
ultimately design the container with an initial burst pressure well
above 200 percent NWP.
Accordingly, NHTSA believes that proposing BPmin to 200
percent NWP, as set forth in GTR No. 13 Phase 2, meets the need for
safety. Proposing the BPmin to 200 percent NWP facilitates
hydrogen vehicle development without unnecessary overdesign of
components. NHTSA seeks comment on the proposed BPmin of 200
percent NWP instead of the 225 percent NWP specified in GTR No. 13
Phase 1.
In the case of containers having glass-fiber as a primary
constituent, consistent with GTR No. 13 Phase 2, NHTSA is proposing a
higher BPmin of 350 percent of NWP because these containers
are highly susceptible to stress rupture as compared to carbon fiber
containers. Stress rupture is a failure mode that relates to the
intrinsic failure probability of the individual fibers that overwrap
the container for support. This failure mode can occur when the fibers
are held under stress for long periods of time (such as in a
continuously pressurized container).\48\ The higher BPmin of
350 percent of NWP provides protection from the risk of stress rupture
in containers having glass-fiber composite as a primary constituent.
NHTSA seeks comment on this proposed requirement and how NHTSA can
determine if a container has glass-fiber as a primary constituent.
NHTSA seeks comment on appropriate criteria to determine the primary
constituent in this context.
---------------------------------------------------------------------------
\48\ SAE Paper 2009-01-0012. Rationale for Performance-based
Validation Testing of Compressed Hydrogen Storage by Christine S.
Sloane, available at https://www.sae.org/publications/technical-papers/content/2009-01-0012/.
---------------------------------------------------------------------------
In the case of containers constructed of both glass and carbon
fibers, NHTSA proposes to apply the requirements according to the
primary constituent of the container as specified by the manufacturer.
NHTSA proposes that the manufacturer shall specify upon request, in
writing, and within five business days, the primary constituent of the
container. NHTSA proposes that the burst pressure of the container, for
which the manufacturer fails to specify upon request, in writing, and
within five business days, the primary constituent of the container,
must not be less than 350 percent of NWP. NHTSA seeks comment on this
proposed requirement.
The test for performance durability, described below, includes a
1000 hour high-temperature (85 [deg]C) static pressure test, which is
designed to evaluate the container's resistance to stress rupture, in
combination with other lifetime stress factors. Given that the high-
temperature static pressure test is focused directly on evaluating
stress rupture risk, and the test for performance durability represents
an overall worst-case lifetime of stress factors, regardless of fiber
type, NHTSA seeks comment on whether the baseline initial burst
pressure test even needs to be included in the standard's requirements.
GTR No. 13 specifies that the baseline initial burst pressure test
(as well as the initial pressure cycle test described below) be
conducted at ambient temperatures between 5 [deg]C and 35 [deg]C. The
IWG of GTR No. 13 determined that container burst strength is not
affected by using this range of ambient temperature between 5 [deg]C
and 35 [deg]C.\49\ This temperature range reduces test costs (thus
improving the practicability of the proposed requirements) by enabling
outdoor testing without special temperature controls. Extreme
temperatures are addressed in later tests.
---------------------------------------------------------------------------
\49\ See GTR No. 13, Part I, paragraph 81(d)(v).
---------------------------------------------------------------------------
GTR No. 13 requires that the rate of pressurization be less than or
equal to 1.4 MPa/s for pressures higher than 150 percent of the nominal
working pressure. If the pressurization rate exceeds 0.35 MPa/s at
pressures higher than 150 percent NWP, GTR No. 13 also requires that
either the container is placed in series between the pressure source
and the pressure measurement device, or that the time at the pressure
above a target burst pressure exceeds 5 seconds. These requirements are
designed to ensure that a pressure sensor will measure the pressure
inside the container accurately. The pressurization rate limit ensures
the pressure sensor will have enough time to read the pressure level as
it rises. Placing the container in series between the pressure source
and the pressure sensor ensures that the container will experience the
pressure before the sensor, so there is no chance that the pressure
sensor could read a pressure level that is not being experienced by the
container. However, NHTSA is concerned that the second option that the
time at the pressure above the target burst pressure exceeds 5 seconds
is unclear and difficult to enforce. For example, it is not clear what
pressure
[[Page 27512]]
the ``target burst pressure'' is referring to since the pressure may be
increasing continuously. Therefore, this option is not being proposed
as an alternative and the container will simply be placed in series
between the pressure source and the pressure measurement device. NHTSA
seeks comment on this decision.
b. Service Life and Number of Cycles for the Baseline Initial Pressure
Cycle Test for Containers on Light and Heavy Vehicles
As discussed above, hydrogen is highly flammable, and therefore,
hydrogen containers must not leak during their service life. While
hydrogen leakage is a serious safety concern, leaking hydrogen will
likely dissipate quickly into the atmosphere given its density, and may
or may not ignite/explode, whereas, a hydrogen container burst involves
an explosion by definition and is therefore a far worse, catastrophic
failure mode that must be prevented under all circumstances regardless
of service life. As a result, hydrogen containers are designed to leak
before bursting beyond their service lives. This ``leak before burst''
safety feature is also followed for other high-pressure vehicle fuel
containers such as vehicle CNG fuel containers. Systems are typically
designed such that the occurrence of leakage should result in vehicle
shut down and subsequent repair or removal of the container from
service, thereby preventing a burst of the container from occurring.
The baseline pressure cycle test requirement is designed to provide
an initial check for resistance to leak or burst due to pressure
cycling during service, and a check that the container does in fact
leak before burst after the container service life has been exceeded.
Accordingly, the baseline initial pressure cycle test requires the
container to (i) not leak or burst for a specified number of pressure
cycles that are meant to represent maximum container service life, and
(ii) leak before burst for a specified number of pressure cycles beyond
the maximum service life. In the case of (i), the IWG of GTR No. 13
Phase 1 gave contracting parties the option of selecting either 5,500,
7,500, or 11,000 cycles as the expected maximum service life
containers. In the case of (ii), the GTR explains that a greater number
of pressure cycles (22,000) that far exceeds service life of containers
is used to ensure that a container should leak before bursting during
the expected service life.
GTR No. 13 provides several examples of the maximum number of
empty-to-full fueling cycles for vehicles under extreme service. These
examples are described below and summarized in Table-1.
Sierra Research Report No. SR2004-09-04 for the California
Air Resource Board (2004) reported on vehicle lifetime distance
traveled by scrapped California vehicles, which all showed lifetime
distances traveled below 350,000 miles. Based on these figures and 200-
300 miles driven per full fueling, the maximum number of lifetime
empty-to-full fuelings can be estimated as 1,200-1,800.
Transport Canada reported that required emissions testing
in British Columbia, Canada, in 2009 showed the five most extreme usage
vehicles had odometer readings in the 500,000-600,000 miles range.
Using the reported model year for each of these vehicles, this
corresponds to less than 300 full fuelings per year, or less than one
full fueling per day. Based on these figures and 200-300 miles driven
per full fueling, the maximum number of empty-to-full fuelings can be
estimated as 1,650-3,100.
The New York City (NYC) taxicab fact book reports extreme
usage of 200 miles in a shift and a maximum service life of five
years.\50\ Less than 10 percent of vehicles remain in service as long
as five years. The average mileage per year is 72,000 for vehicles
operating two shifts per day and seven days per week. There is no
record of any vehicle remaining in high usage through-out the full 5-
year service life. However, if a vehicle were projected to have fueled
as often as 1.5-2 times per day and to have remained in service for the
maximum 5-year NYC taxi service life, the maximum number of fuelings
during the taxi service life would be 2,750-3,600.
---------------------------------------------------------------------------
\50\ New York City taxicab fact book, Schaller Consulting
(2006), http://www.schallerconsult.com/taxi/taxifb.pdf.
---------------------------------------------------------------------------
Transport Canada reported a survey of taxis operating in
Toronto and Ottawa that showed common high usage of 20 hours per day,
seven days per week with daily driving distances of 335-450 miles.
Vehicle odometer readings were not reported. In the extreme worst-case,
it might be projected that if a vehicle could remain at this high level
of usage for seven years (the maximum reported taxi service life); then
a maximum extreme driving distance of 870,000-1,200,000 miles is
projected. Based on 200-300 miles driven per full fueling, the
projected full-usage 15-year number of full fuelings could be 2,900-
6,000.
Table 1--Expected Vehicle Usage Data Summary
--------------------------------------------------------------------------------------------------------------------------------------------------------
Number of lifetime empty-to-full
Data source Lifetime traveling distance (miles) Distance per full-fueling (mile) filling
--------------------------------------------------------------------------------------------------------------------------------------------------------
Sierra Research Report No. SR2004- 350,000.............................. 200-300.............................. 1,200-1,800.
09-04: California vehicles.
Transport Canada: Vehicle fleet 500,000-600,000...................... 200-300.............................. 1,650-3,100.
&Taxi.
The New York City (NYC) taxicab 360,000 (5 year life)................ N/A (Fueling frequency 1.5-2 times/ 2750-3600 (5 year life).
fact book: Taxi usage. day).
Transport Canada: Taxi usage....... 870,000-1,200,000.................... 200-300.............................. 2,900-6,000.
--------------------------------------------------------------------------------------------------------------------------------------------------------
Based on these examples, the IWG of GTR No. 13 Phase 1 set the
minimum number of pressure cycles before leak at 5,500. The maximum
number of cycles before leak was set at 11,000 cycles, which
corresponds to a vehicle that remains in service with two full fuelings
per day for 15 years (expected lifetime vehicle mileage of 2.2-3.3
million miles). The last example above shows it is possible for a high
usage taxi to experience 6,000 fueling cycles during seven years of
service. Taxi service is representative of the most demanding
circumstances a light vehicle will experience, so this example is
considered worst-case. Furthermore, such a vehicle could be
subsequently resold and experience further fuelings beyond 6,000. As a
result, the IWG of GTR No. 13 Phase 2 concluded that the
[[Page 27513]]
choice of 5,500 cycles is not sufficient for containers on light
vehicles. However, NHTSA concludes that the maximum choice of 11,000
cycles is too extreme for light vehicles. A vehicle traveling 2.2-3.3
million miles is unrealistic even for the most extreme service life for
light vehicles. Accordingly, NHTSA proposes 7,500 as the number of
cycles in the baseline initial pressure cycle test for which the
container does not leak or burst. NHTSA believes that 7,500 pressure
cycles is a reasonable representation of the maximum service life of a
container, and notes that is greater than that presented in Table 1 for
the Transport Canada taxi usage data.
As discussed above, the worst-case scenario is a container failure
by burst. To ensure the container leaks before burst beyond the maximum
service life, the container is pressure cycled beyond the 7,500 cycles
(representing maximum service life) until leak occurs without burst or
up to a maximum of 22,000 hydraulic pressure cycles. For vehicles with
nominal on-road driving range of 300 miles per full-fueling, 22,000
hydraulic pressure cycles correspond to over 6 million miles, which is
beyond extreme on-road vehicle lifetime range.
The analysis summarized above considered light vehicles with a
service life of 15 years. When conducting their analysis, the IWG of
GTR No. 13 Phase 1 had limited information available on lifetime
vehicle mileage and fuelings. In addition, hydrogen vehicles were a new
technology and there was very little field experience available to draw
upon. As a result, the IWG of GTR No. 13 Phase 1 was conservative in
setting the number of cycles for the baseline initial cycle test. In
the analysis provided above, short periods of extreme service were
extrapolated to a full 15-year service life. This is not a realistic
assumption because vehicles generally cannot last in extreme service
for a full 15 years.
To address this issue, the IWG of GTR No. 13 Phase 2 reviewed new
data on the number of vehicle miles traveled. The analysis was also
expanded to include heavy vehicles in addition to light
vehicles.51 52 The data shows that the number of cycles
presented in GTR No. 13 for light vehicles correspond more
appropriately to a 25-year service life.
---------------------------------------------------------------------------
\51\ See GTR No. 13 Phase 2 file GTR13-11-12b: The number of
cycles, https://wiki.unece.org/download/attachments/123666576/GTR13-9-07%20TF1%20OICA%20GTR13%20Baseline%20Initial%20Cycles.pdf?api=v2.
\52\ See GTR No. 13 Phase 2 file GTR13-9-07: Extension of the
service life of the container to 25 years, https://wiki.unece.org/download/attachments/140706658/GTR13-11-12b%20TF1%20%20210927%20Estimation%20of%20VMT%20TF1-JAMA.pdf?api=v2.
---------------------------------------------------------------------------
For heavy vehicles, the new data on the number of vehicle miles
traveled that was collected in Phase 2 indicates a higher number of
cycles are required for a 25-year service life than that for light
vehicles. This is consistent with the fact that heavy vehicles
typically travel farther and remain in service longer than light
vehicles. Consequently, for heavy vehicle containers, the IWG of GTR
No. 13 Phase 2 set the number of pressure cycles representing maximum
container service life at 11,000. In accordance with GTR No. 13 Phase
2, NHTSA proposes to require heavy vehicle containers to neither leak
nor burst for 11,000 hydraulic pressure cycles, and also to leak
without burst (or neither leak nor burst) beyond the 11,000 hydraulic
pressure cycles up to a maximum of 22,000 pressure cycles. The proposed
service life, number of hydraulic pressure cycles representing the
maximum service life for which the container is required not to leak
nor burst, and the number of pressure cycles beyond that representing
maximum service life of the container for which the container is
required to leak without burst or not leak nor burst at all is
summarized in Table-2 for light and heavy vehicles.
Table 2--Proposed Service Life and Number of Cycles in the Baseline Hydraulic Pressure Cycle Test for Light and
Heavy Vehicles
----------------------------------------------------------------------------------------------------------------
Number of cycles
representing maximum Number of cycles for
Vehicle type Service life service life for which which the container
(years) the container does not leaks without burst, or
leak nor burst does not leak nor burst
----------------------------------------------------------------------------------------------------------------
Light......................................... 25 7,500 7,501-22,000
Heavy......................................... 25 11,000 11,001-22,000
----------------------------------------------------------------------------------------------------------------
NHTSA seeks comment on the proposed number of cycles in Table-2.
NHTSA seeks any additional data available related to vehicle life,
lifetime miles travelled, and number of lifetime fuel cycles.
c. Details of the Baseline Initial Cycle Test for Containers on Light
and Heavy Vehicles
The low pressure during each cycle has been set at between 1 MPa to
2 MPa. This is selected to make the test easy to conduct. NHTSA seeks
comment whether this low-pressure range is sufficiently wide for test
lab efficiency. The high pressure of 125 percent NWP is selected
because this is the peak pressure that typically occurs during fueling.
Furthermore, this is the high pressure used in the ANSI NGV 2-2007,
Compressed Natural Gas Vehicle Fuel Containers, ambient cycling
test.\53\
---------------------------------------------------------------------------
\53\ ANSI NGV 2-2007, Compressed Natural Gas Vehicle Fuel
Containers, 16.3 Ambient Cycling Test. https://webstore.ansi.org/standards/csa/ansingv22007.
---------------------------------------------------------------------------
GTR No. 13 requires three new containers to be tested during the
baseline initial pressure cycle test. However, NHTSA does not believe
three new containers need to be tested under the U.S. self-
certification system where NHTSA buys and tests vehicles and equipment
at the point of sale. Therefore, NHTSA has instead decided to base the
value on the results of testing any one container for the baseline
initial pressure cycle test. NHTSA seeks comment on this decision.
---------------------------------------------------------------------------
\54\ Id.
---------------------------------------------------------------------------
GTR No. 13's maximum hydraulic pressure cycle rate of 10 cycles/
minute is based on the requirement in ANSI NGV 2-2007 for the ambient
cycling test.\54\ This pressure cycling rate is selected to allow for
efficient compliance testing. Actual fueling cycles for hydrogen
vehicles occur more slowly. For these reasons, the container
manufacturer may specify a hydraulic pressure cycle profile that will
prevent premature failure of the container due to test conditions
outside of the container design envelope. Changing the hydraulic
cycling profile does not
[[Page 27514]]
change the stringency of the test or the safety of the container.
However, the cycling profile can be important because testing NHTSA
conducted resulted in a container failure attributed to a rapid
defueling profile that was not representative of defueling rates during
normal use.55 56 NHTSA seeks comment on cycling profiles and
whether the pressure cycling profile will significantly affect the test
result. NHTSA seeks comment on more specifics of what manufacturers
should be allowed to specify regarding an appropriate pressure cycling
profile for testing their system.
---------------------------------------------------------------------------
\55\ DOT HS_812_988. Hydrogen Container Performance Testing,
https://rosap.ntl.bts.gov/view/dot/62645.
\56\ Details are provided in the technical document ``Quantum
GTR Pressure Cycle Discussion.pdf'' submitted to the docket of this
NPRM.
---------------------------------------------------------------------------
A burst may be preceded by an instantaneous moment of leakage,
especially if observed in slow motion. Therefore, NHTSA proposes a
minimum time of 3 minutes to sustain a visible leak before the test can
end successfully due to ``leak before burst.'' NHTSA seeks comment on
this additional requirement.
5. Test for Performance Durability
The container must withstand stress factors beyond basic
pressurization and pressure cycling without leakage or burst. The
container must demonstrate its durability by not leaking or bursting
during a service life of pressure cycling that includes the application
of external stress factors. The container must also withstand 180
percent NWP for four minutes \57\ after the application of all the
external stress factors and have a burst pressure that is at least 80
percent of its BPO at the end of a service life that
includes external stress factors. This requirement is evaluated by the
test for performance durability. The test for performance durability
uses the same service life described above for the tests for baseline
metrics, along with external stress factors applied to the container.
---------------------------------------------------------------------------
\57\ The 180 percent NWP hold for 4 minutes is a simulation of a
fueling station pressure regulation failure that results in over
pressurization of the container. This test is conducted after all
other external stresses have been applied to the container to
simulate over-pressurization near the end-of-life of the container.
---------------------------------------------------------------------------
A container is expected to encounter six types of external stress
factors:
1. Impact (drop during installation and/or road wear)
2. Static high pressure from long-term parking
3. Over-pressurization from fueling and fueling station malfunction
4. Environmental exposures (chemicals and temperature/humidity)
5. Vehicle fire
6. Vehicle crash
The test for performance durability addresses the first four of
these external stresses. Fire is addressed in a separate section for
fire. Crash performance is addressed through crash testing in FMVSS No.
307. The test for performance durability is closely consistent with the
industry standard SAE J2579_201806, Standard for Fuel Systems in Fuel
Cell and Other Hydrogen Vehicles.\58\
---------------------------------------------------------------------------
\58\ SAE J2579_201806. Standard for Fuel Systems in Fuel Cell
and Other Hydrogen Vehicles. https://www.sae.org/standards/content/j2579_201806/
---------------------------------------------------------------------------
Other than fire and vehicle crash, testing of the stresses
compounded in a series is required.\59\ This is because a container may
experience all of these stresses during its service life, and the
safety need for a hydrogen system remains an issue for the vehicle's
entire service life. For example, a container that was dropped during
installation could thereafter be exposed to road wear, long term
parking, fueling stresses, and environmental exposures. Accordingly,
the proposed test for performance durability arranges these external
stresses in a sequential application representing a severe in-service
permutation of the stresses. The test sequence is as follows:
---------------------------------------------------------------------------
\59\ This is in contrast to industry standards, wherein
performance is evaluated after the application of a single stress
factor in order to identify which stress factors cause failure.
Proof pressure test
Drop test
Surface damage test
Chemical exposure test and ambient-temperature pressure
cycling test
High temperature static pressure test
Extreme temperature pressure cycling test
Residual pressure test
Residual strength burst test
The test for performance durability is illustrated in Figure-4.
[[Page 27515]]
[GRAPHIC] [TIFF OMITTED] TP17AP24.003
Figure-4: Illustration of the Test for Performance Durability
For similar reasons as those explained above for the baseline
tests, the cycling pressure force on containers is applied
hydraulically with non-corrosive fluid such as water or a mixture of
anti-freeze and water to prevent freezing. This allows for improved
test lab safety and faster pressurization and depressurization rates
which decreases the cost to conduct the tests.
a. Proof Pressure Test
The proof pressure test is typically done by the manufacturer
before sale of the container. The proof pressure test is performed to
confirm that the container will not leak nor burst due to a simple
over-pressurization event to 150 percent NWP. The test pressure of 150
percent NWP is selected because fueling stations are expected to
provide over-pressure protection of 150 percent NWP. A proof pressure
test is a stress factor that can in some cases result in micro-cracks
appearing in the container. Micro-cracks may weaken a tank's wall
strength, causing the potential for leaks or a burst during the proof
pressure test or the subsequent performance durability testing.
Therefore, it is important that all containers experience proof
pressure.
GTR No. 13 states that a container that has undergone a proof
pressure test in manufacture is exempt from this test. However, NHTSA
may not know whether a container has undergone the proof pressure test.
As a result, NHTSA proposes that all containers will be subjected to
the proof pressure test as part of the test for performance durability.
In the event that a proof pressure test is conducted during manufacture
and as part of the tests for performance durability, the container
would experience two proof pressure tests. However, it is not expected
that a second application will result in significantly more stress to
the container than a single proof pressure test. NHTSA seeks comment on
conducting the proof pressure test on all containers.
b. Drop Test
The drop test is conducted to simulate dropping the container
during handling or installation. Consistent with GTR No. 13, the
unpressurized container may be dropped in any one of several
orientations such as horizontal, vertical, or at a 45[deg] angle. In
the case of a non-cylindrical or asymmetric container, the horizontal
and vertical axes may not be clear. In such cases, the container will
be oriented using its center of gravity and the center of any of its
shut-off valve interface locations. The two points will be aligned
horizontally (i.e., perpendicular to gravity), vertically (i.e.,
parallel to gravity) or at a 45[deg] angle relative to vertical. The
center of gravity of an asymmetric container may not be easily
identifiable, so NHTSA seeks comment on the appropriateness of using
the center of gravity as a reference point for this compliance test and
how to properly determine the center of gravity for a highly asymmetric
container.
The surface onto which the container is dropped must be a smooth,
horizontal, uniform, dry, concrete pad or other flooring type with
equivalent hardness. The drop height of 1.8 meters is selected to
represent a drop from a forklift during installation. The four possible
drop orientations are illustrated in Figure-5 below.
[[Page 27516]]
[GRAPHIC] [TIFF OMITTED] TP17AP24.004
Figure-5: The Four Possible Drop Orientations
GTR No. 13 specifies a potential energy of at least 488 J during
the vertical drops, along with a maximum drop height of 1.8 m, and a
minimum drop height of 0.1 m. It is possible that a drop involving a
very lightweight container could not simultaneously satisfy both the
488 J minimum energy and the 1.8 m maximum height. The IWG of GTR No.
13 Phase 2 resolved this conflict by specifying the vertical drop test
potential energy of at least 488 J, with an overriding limitation that
the drop height not exceed 1.8 m in any case. In the case of a
lightweight container that would require a drop height over 1.8 m to
reach 488 J of drop energy, the container should be dropped from 1.8 m,
regardless of the potential energy. Similarly, a very heavy container
could reach a potential energy \60\ of 488 J while being less than 0.1
m above the drop surface. In this case, the container should be dropped
from the 0.1 m minimum drop height.
---------------------------------------------------------------------------
\60\ Potential energy is calculated as the product of container
mass, gravitational acceleration, and the height from the center of
gravity of the container to the surface onto which the container is
dropped.
---------------------------------------------------------------------------
For the angled drop, the container is dropped from any angle
between 40[deg] and 50[deg] from the vertical orientation with the
center of any shut-off valve interface location downward. However, if
the lowest point of the container is closer to the ground than 0.6 m,
the drop angle is changed such that the lowest point of the container
is 0.6 m above the ground and the center of gravity is 1.8 m above the
surface onto which it is dropped. This may result in a drop angle
greater than 50[deg] from the vertical orientation.
The drop test is conducted with an unpressurized container because
the risk of dropping is primarily aftermarket during vehicle repair
where a new storage system, or an older system removed during vehicle
service, is dropped from a forklift during handling. Additionally, drop
testing conducted by NHTSA under various conditions indicated that an
unpressurized container is more susceptible to damage in the drop test
than a pressurized container.\61\
---------------------------------------------------------------------------
\61\ DOT HS_812_988. Hydrogen Container Performance Testing,
https://rosap.ntl.bts.gov/view/dot/62645.
---------------------------------------------------------------------------
The drop test is a test in which container attachments may improve
performance by protecting the container when it impacts the ground.
Consistent with GTR No. 13, the drop test is conducted on the container
with any associated container attachments. NHTSA seeks comment on
including container attachments for the drop test.
It is possible that the container could experience damage from the
drop test that prevents continuing with the remainder of the tests for
performance durability. To address this possibility, NHTSA proposes
that if any damage to the container following the drop test prevents
further testing of the container, the container is considered to have
failed the tests for performance durability and no further testing is
conducted.
c. Surface Damage Test
The surface damage test applies cuts and impacts to the surface of
the container. The cuts on the surface simulate abrasions that can
occur due to container mounting hardware or straps. The impacts
simulate on-road impacts, such as flying gravel. The surface damage
test consists of two linear cuts and five pendulum impacts.
The linear cuts are created with a saw. The first cut is 0.75
millimeters to 1.25 millimeters deep and 200 to 205 millimeters long.
The second cut is 1.25 millimeters to 1.75 millimeters deep and 25
millimeters to 28 millimeters long. The second cut is only applied if
the container is to be affixed to the vehicle by compressing its
composite surface.
GTR No. 13 allowed all-metal containers to be exempt from the
linear cuts because (1) metal is scratch resistant compared to non-
metal, and (2) metal containers can be so thin that the cuts would
fully penetrate the container. NHTSA's proposal includes this
exemption, but NHTSA seeks comment on whether another objective and
practicable procedure exists for evaluating surface abrasions that
could apply to all containers, such as, for example, the application of
a defined cutting force to the container surface.
The impacts are created with a pendulum impactor consisting of a
pyramid with equilateral faces and square base, and with the summit and
edges being rounded to a radius of 3 mm. The impact of the pendulum
occurs with a nominal impact energy of 30 J. Prior to the impacts, the
container is preconditioned at -40 [deg]C to simulate a worst-case
temperature environment. The temperature of -40 [deg]C was selected
based on industry standards.\62\ We note that weather records show
temperatures
[[Page 27517]]
of -40 [deg]C can occur in northern locations of the United States.\63\
---------------------------------------------------------------------------
\62\ SAE J2579_201806. Standard for Fuel Systems in Fuel Cell
and Other Hydrogen Vehicles.
\63\ Canadian Climate Normals, https://climate.weather.gc.ca/climate_normals/index_e.html.
---------------------------------------------------------------------------
The surface damage test is a test in which container attachments
may improve performance by shielding the container from the impacts.
For containers with container attachments, GTR No. 13 specifies that if
the container surface is accessible, then the test is conducted on the
container surface. However, NHTSA is concerned that determining whether
the container surface is accessible is subjective, because
``accessible'' is not defined in the GTR and could have many potential
meanings. Therefore, NHTSA is not proposing a specification involving
the accessibility of the container surface. Instead, NHTSA proposes
that if the container attachments can be removed using a process
specified by the manufacturer, they will be removed and not included
for the surface damage test nor for the remaining portions of the test
for performance durability. Testing the container without its container
attachments is representative of a situation in which installation
personnel remove the container attachments and fail to re-install them
before the container enters service. Container attachments that cannot
be removed are included for the test. NHTSA seeks comment on including
container attachments for the surface damage test.
In accordance with GTR No. 13, NHTSA proposes specifying the
pendulum impacts ``on the side opposite from the saw cuts.'' For
containers with multiple permanently interconnected chambers, GTR No.
13 specifies applying the pendulum impacts to a different chamber to
that where the saw cuts were made. However, the agency is not proposing
this distinction for pendulum impact location for containers with
multiple permanently interconnected chambers because NHTSA is concerned
that it may be less stringent (and thus, potentially less protective of
safety) than when impacts are to the same chamber where the cuts were
applied. NHTSA seeks comment on whether applying the impacts to the
opposite side of the same chamber that received the saw cuts may be
more stringent than applying the impacts to a separate chamber, and
whether including the specification as written in GTR No. 13 would
reduce stringency for containers with multiple permanently
interconnected chambers relative to containers with a single chamber.
d. Chemical Exposure and Ambient Pressure Cycling Test
Consistent with GTR No. 13, the chemical exposure test exposes the
container to a range of chemicals that might be encountered in on-road
service:
Sulfuric acid at 19 percent in water to simulate battery
acid.
Sodium hydroxide at 25 percent in water to simulate lye.
Methanol at 5 percent in gasoline to simulate fueling
station fluids.
Ammonium nitrate at 28 percent in water to simulate
fertilizer.
Methanol at 50 percent in water to simulate windshield-
washer fluid.
A pad of glass wool saturated with one of the chemicals listed
above is applied to each of the pendulum impact locations from the
surface damage test. This is done to simulate each chemical exposure in
an area where on-road damage has degraded the container's protective
coating. The chemicals are applied with glass wool fibers to keep them
in place and reduce evaporation.
After the chemical exposures are in place, pressure cycling
commences. The test for performance durability uses the same number of
cycles as required by the baseline initial cycle test before leakage.
This is a total of 7,500 cycles for light vehicles or 11,000 cycles for
heavy vehicles. Of the total cycles, 60 percent are conducted with the
chemical exposures in place, and at ambient temperature (5 [deg]C to 35
[deg]C). All but the final 10 of these chemical exposure cycles are
conducted from low pressure of 2 MPa to high pressure of 125 percent
NWP, as in the baseline initial pressure cycle test. These cycles
simulate extended vehicle use after impact damage and exposure to
chemicals.
The final 10 chemical exposure cycles are conducted to a high
pressure of 150 percent NWP to simulate fueling station over-
pressurization. After completing chemical exposure cycles, the chemical
exposure pads are removed, and the exposed areas are washed with water
to remove excess chemicals.
The chemical exposure test is a test in which container attachments
may improve performance by shielding the container from the chemical
exposures. Container attachments will be included in the chemical
exposure test unless they were removed prior to the surface damage
test. NHTSA seeks comment on including container attachments for the
chemical exposure test.
e. High Temperature Static Pressure Test
Consistent with GTR No. 13, the high temperature static pressure
test involves holding the container for 1000 hours at 85 [deg]C and 125
percent NWP. This test simulates an extended exposure to high static
pressure and temperature, which is a condition that could occur in the
case of a vehicle parked for an extended period of time. The primary
risk associated with prolonged parking at high pressure and temperature
is stress rupture. However, the stress rupture condition cannot be
directly replicated because the relevant time period is years to
decades. Alternatively, experimental data on the tensile stress failure
of strands representative of those used in container composite wrapping
showed that: 64 65
---------------------------------------------------------------------------
\64\ SAE Paper 2009-01-0012. Rationale for Performance-based
Validation Testing of Compressed Hydrogen Storage by Christine S.
Sloane.
\65\ Christine S. Sloane, Hydrogen Storage technology--Materials
and Applications, edited by Lennie Klebanoff, Section III-12 with
Figure 12.6 Glass fiber composite strands.
---------------------------------------------------------------------------
For the glass fiber composite strands, the probability of
failure for 25 years under tensile stress of 100 percent NWP is
equivalent to 1000 hours under a tensile stress of 125 percent NWP.
The time to failure increased when the load was reduced.
Carbon fiber composite strands showed greater resistance
to stress rupture than glass fiber composite strands in that a small
reduction in the applied load resulted in a greater increase in time to
failure for the carbon fiber composite strands than for the glass fiber
composite strands.
For carbon fiber composite strands, the probability of
failure for 25 years under tensile stress of 100 percent NWP is
approximately equivalent to 500 hours under tensile stress of 125
percent NWP.
An elevated temperature of 85 [deg]C is applied to account for
heat-accelerated deterioration. The temperature of 85 [deg]C represents
an extreme under-hood temperature for a dark/black-colored vehicle
parked outside on asphalt in direct sunlight in 50 [deg]C ambient
conditions.\66\ Including the extreme temperature condition of 85
[deg]C in the high temperature static pressure test ensures that the
container can sustain exposure to 85 [deg]C for 1000 hours under
tensile stress of 125 NWP without experiencing stress rupture.
---------------------------------------------------------------------------
\66\ SAE J2579_201806. Standard for Fuel Systems in Fuel Cell
and Other Hydrogen Vehicles.
---------------------------------------------------------------------------
f. Extreme Temperature Pressure Cycling Test
Consistent with GTR No. 13, the extreme temperature pressure
cycling test involves pressure cycling at extreme temperatures and
simulates operation
[[Page 27518]]
(fueling and defueling) in extreme temperature conditions. As mentioned
above, the test for performance durability uses the same number of
cycles as required by the baseline initial cycle test before leakage.
This is a total of 7,500 cycles for light vehicles or 11,000 cycles for
heavy vehicles. The extreme temperature pressure cycling test consists
of 40 percent of these total cycles, of which half (20 percent of the
total) are conducted at -40 [deg]C and the other half are conducted at
85 [deg]C. The cold temperature -40 [deg]C is selected to simulate a
worst-case extreme cold environment as explained above for the surface
damage test, and the hot temperature of 85 [deg]C is selected for the
same reasons discussed above for the high temperature static pressure
test. During the cold pressure cycling, the maximum cycling pressure is
only 80 percent NWP. This is because fueling pressures do not reach 100
percent NWP when fueling in extreme cold because as temperature
decreases, pressure also decreases. During the hot pressure cycling,
the maximum cycling pressure is 125 percent NWP for the reasons
discussed above for the baseline initial pressure cycle test.
During the extreme temperature pressure cycling test, the relative
humidity is maintained above 80 percent to represent high humidity that
may foreseeably be encountered in the U.S. Humidity is known to degrade
some materials due to the presence of moisture in humid air. Therefore,
it is important to include the stress factor of humidity in the test
for performance durability.
g. Residual Pressure Test
Consistent with GTR No. 3, the residual pressure test requires
pressurizing the container to 180 percent NWP and holding this pressure
for 4 minutes. The 180 percent NWP hold for 4 minutes is a simulation
of a fueling station pressure regulation failure that results in over-
pressurization of the container. This test is conducted after all other
external stresses have been applied to the container to simulate over-
pressurization near the end of life of the container.67 68
---------------------------------------------------------------------------
\67\ SAE J2579_201806. Standard for Fuel Systems in Fuel Cell
and Other Hydrogen Vehicles. Appendix H.
\68\ Christine S. Sloane, Hydrogen Storage technology--Materials
and Applications, edited by Lennie Klebanoff, Section III-12 with
Figure 12.6 Glass fiber composite strands.
---------------------------------------------------------------------------
h. Residual Strength Burst Test
Consistent with GTR No. 13, the residual strength burst test
involves subjecting the end-of-life container to a burst test identical
to the baseline initial burst pressure test. The burst pressure at the
end of the durability test is required to be at least 80 percent of the
BPO specified on the container label. This effectively
controls the burst pressure degradation rate throughout an extreme
service life. Controlling degradation rate is important because, for
example, a container starting with a very high BPO, say 400
percent NWP, but then declining to 180 percent NWP indicates a high
degradation rate. NHTSA is concerned that if such a container were to
be kept in service beyond its intended service life, the high
degradation rate could continue and lead to a high risk of burst.
Therefore, the residual burst strength must be at least 80 percent of
BPO. This concept is similar to the requirements for seat
belt webbing in FMVSS No. 209 where both minimum breaking strength
after abrasion (S4.2d) as well as maximum degradation rate after
exposure to light and micro-organisms (S4.2e and S4.2f) are controlled.
6. Test for Expected On-Road Performance
For ensuring safe operations, the CHSS must contain hydrogen
without leakage or burst. The expected on-road performance test ensures
the CHSS is able to effectively contain hydrogen without leakage or
burst. Consistent with GTR No. 13, the test for expected on-road
performance uses on-road operating conditions including fueling and
defueling the container at different ambient conditions with hydrogen
gas at low and high temperatures. The test also includes a static high-
pressure hold during which the CHSS is evaluated for hydrogen leakage
and/or permeation of hydrogen from the CHSS. The container of the CHSS
must withstand 180% NWP hold for 4 minutes and have a burst pressure
that is at least 80 percent of its BPO at the end of the
test for expected on-road performance. The test for expected on-road
performance is closely consistent with the industry standard SAE
J2579_201806.\69\
---------------------------------------------------------------------------
\69\ SAE J2579_201806. Standard for Fuel Systems in Fuel Cell
and Other Hydrogen Vehicles.
---------------------------------------------------------------------------
While the test for performance durability evaluates the durability
of the container when exposed to external stress factors combined with
hydraulic pressure cycling, the test for expected on-road performance
does not evaluate durability and instead focuses on pneumatic hydrogen
fueling exposure, along with extreme temperature conditions. When
fueling, hydrogen gas increases its temperature due to the Joule
Thomson effect.\70\ As a result, pneumatic testing with hydrogen gas
creates rapid temperature swings within the CHSS that do not occur
during hydraulic cycling. Pneumatic testing also can result in hydrogen
diffusion into materials, which can have deleterious chemical effects
such as hydrogen embrittlement.\71\ Due to these unique stress factors,
a pneumatic test using hydrogen gas is an effective method for
evaluating the susceptibility of the CHSS to hydrogen permeation and
leakage.
---------------------------------------------------------------------------
\70\ For more information, see https://www.britannica.com/science/Joule-Thomson-effect.
\71\ For more information, see https://www.sciencedirect.com/
topics/engineering/hydrogen-
embrittlement#:~:text=3.7%20Hydrogen%20Embrittlement-
,Hydrogen%20embrittlement%20(HE)%20refers%20to%20mechanical%20damage%
20of%20a%20metal,when%20hydrogen%20atoms%20are%20generated.
---------------------------------------------------------------------------
Again, consistent with GTR No. 13, the test for expected on-road
performance starts with a proof pressure test pressurizing the
container with hydrogen to 150 percent NWP. This is followed by a total
of 500 pressure cycles at various environmental conditions. The 500
cycles are broken up into stages for low temperature cycling, high
temperature cycling, and ambient temperature cycling. Table-3 shows the
number of cycles during each stage, along with other applicable
conditions. After the first 250 cycles, the CHSS is held at high
pressure and temperature for up to 500 hours while it is evaluated for
leakage and/or permeation. After the completion of all 500 cycles, the
CHSS is again held at high pressure and temperature for 500 hours and
evaluated for leakage and/or permeation.
Following this second leakage/permeation evaluation, the container
is pressurized with hydraulic fluid to 180% NWP and held for 4 minutes.
The container then undergoes a residual strength burst test in a
similar manner as that described for the test for performance
durability. Similar to the test for performance durability, the
container's residual burst pressure must be at least 80 percent of
BPO. A visual schematic of the test is shown in Figure-6
below.
[[Page 27519]]
Table 3--Summary of the Test for Expected On-Road Performance
--------------------------------------------------------------------------------------------------------------------------------------------------------
Number of
Stage of test cycles Ambient conditions Fuel delivery temperature Pressurization medium
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pneumatic proof pressure test to 150% not appliable 5.0 [deg]C to 35.0 -40.0 [deg]C to -33.0 [deg]C.......... Hydrogen gas.
NWP. [deg]C.
Low temperature cycling.............. 5 -30.0 [deg]C to -25.0 15.0 [deg]C to 25.0 [deg]C............ Hydrogen gas.
[deg]C.
Low temperature cycling.............. 20 -30.0 [deg]C to -25.0 -40.0 [deg]C to -33.0 [deg]C.......... Hydrogen gas.
[deg]C.
High temperature cycling............. 25 50.0 [deg]C to 55.0 -40.0 [deg]C to -33.0 [deg]C.......... Hydrogen gas.
[deg]C.
80% to 100% relative
humidity.
Ambient temperature cycling.......... 200 5.0 [deg]C to 35.0 -40.0 [deg]C to -33.0 [deg]C.......... Hydrogen gas.
[deg]C.
Static pressure for up to 500 hours not appliable 55.0 [deg]C to 60.0 not appliable......................... Hydrogen gas.
with leak/permeation evaluation. [deg]C.
High temperature cycling............. 25 50.0 [deg]C to 55.0 -40.0 [deg]C to -33.0 [deg]C.......... Hydrogen gas.
[deg]C, 80% to 100%
relative humidity.
Low temperature cycling.............. 25 -30.0 [deg]C to -25.0 -40.0 [deg]C to -33.0 [deg]C.......... Hydrogen gas.
[deg]C.
Ambient temperature cycling.......... 200 5.0 [deg]C to 35.0 -40.0 [deg]C to -33.0 [deg]C.......... Hydrogen gas.
[deg]C.
Static pressure for up to 500 hours not appliable 55.0 [deg]C to 60.0 not appliable......................... Hydrogen gas.
with leak/permeation evaluation. [deg]C.
Residual pressure test............... not applicable not applicable......... not applicable........................ Hydraulic fluid.
Burst test........................... not applicable not applicable......... not applicable........................ Hydraulic fluid.
--------------------------------------------------------------------------------------------------------------------------------------------------------
[GRAPHIC] [TIFF OMITTED] TP17AP24.005
Figure-6: Illustration of the Test for Expected On-Road Performance
a. Proof Pressure Test
The proof pressure test is conducted in the same manner and for the
same reasons discussed above for the test for performance durability.
However, in this test, the container is pressurized to 150 percent NWP
using hydrogen gas which has been pre-cooled to -40.0 [deg]C to -33.0
[deg]C. This is the temperature range to which hydrogen fueling
stations typically pre-cool hydrogen to offset the hydrogen's
temperature increase during fueling.
[[Page 27520]]
b. Ambient and Extreme Temperature Gas Pressure Cycling Test
The expected lifetime fueling exposure consists of 500 fuel cycles
from 2 MPa to 125 percent NWP (empty-to-full) under a variety of
ambient fueling temperatures. The number 500 is obtained through a
calculation of expected vehicle lifetime driving range divided by
driving range per full-fueling. This calculation and the data source is
summarized in Table-4.
Table 4--Maximum Number of Full Fueling/Defueling Cycles
------------------------------------------------------------------------
Expected vehicle Expected vehicle Expected worst-
lifetime driving driving range case number of
range per full-fueling full-fueling
------------------------------------------------------------------------
Data source......... Sierra Research 2006-2007 market ..............
Report No. SR data of high
2004-09-04, volume
September 22, passenger
2004. vehicle
manufacturers
in Europe,
Japan, North
America.
Calculation......... 250,000 km 483 km (300 500
(155,000 miles). miles).
------------------------------------------------------------------------
Some vehicles may exceed 500 fuel cycles if partial fueling occurs
in the vehicle lifetime. However, the stress of full fueling exceeds
the stress of partial fueling because of the higher pressure and
temperature change during full-fueling. NHTSA believes that, as a
result, 500 full-fueling cycles should provide robust demonstration of
leak-free fueling capability.
The industry standard SAE J2601_202005 Fueling protocols for light
duty gaseous hydrogen surface vehicles establishes industry-wide
fueling protocols for the fueling of hydrogen into passenger vehicles.
The guidelines include: \72\
---------------------------------------------------------------------------
\72\ SAE J2601_202005. Fueling Protocols for Light Duty Gaseous
Hydrogen Surface Vehicles. https://www.sae.org/standards/content/j2601_202005/.
1. The maximum pressure within the vehicle fuel system is 125 percent
NWP
2. Gas temperature within the vehicle fuel system is less than or equal
to 85 [deg]C
3. Fuel flow rate at dispenser nozzle is less than or equal to 60 g/s
4. The dispenser is capable of dispensing fuel at temperatures between
-40 [deg]C and -33 [deg]C
These guidelines are applied at hydrogen fueling stations when
fueling hydrogen vehicles. During the ambient and extreme temperature
gas pressure cycling test, the rate of pressurization must be greater
than or equal to the ramp rate specified by a table of ramp rates based
on SAE J2601_202005, according to the CHSS volume, the ambient
conditions, and the fuel delivery temperature. If the required ambient
temperature is not available in the table, the closest ramp rate value
or a linearly interpolated value is used. This ensures that the fueling
cycles are similar to those that would occur during on-road service.
Table-5 shows the ramp rates based on SAEJ2601_202005, for different
CHSS volume, the ambient conditions, and the fuel delivery temperature.
GTR No. 13 specifies that the pressure ramp rate shall be decreased if
the measured internal temperature in the container exceeds 85 [deg]C.
Table 5--Pressure Ramp Rates for the Test for Expected On-Road Performance
--------------------------------------------------------------------------------------------------------------------------------------------------------
CHSS pressurization rate (MPa/min)
---------------------------------------------------------------------------------------------------
50.0 [deg]C to 55.0 5.0 [deg]C to 35.0 -30.0 [deg]C to -25.0 -30.0 [deg]C to -25.0
CHSS volume (L) [deg]C ambient [deg]C ambient [deg]C ambient [deg]C ambient
conditions -33.0 [deg]C conditions -33.0 [deg]C conditions -33.0 [deg]C conditions 15.0 [deg]C
to -40.0 [deg]C fuel to -40.0 [deg]C fuel to -40.0 [deg]C fuel to 25.0 [deg]C fuel
delivery temperature delivery temperature delivery temperature delivery temperature
--------------------------------------------------------------------------------------------------------------------------------------------------------
50.................................................. 7.6 19.9 28.5 13.1
100................................................. 7.6 19.9 28.5 7.7
174................................................. 7.6 19.9 19.9 5.2
250................................................. 7.6 19.9 19.9 4.1
300................................................. 7.6 16.5 16.5 3.6
400................................................. 7.6 12.4 12.4 2.9
500................................................. 7.6 9.9 9.9 2.3
600................................................. 7.6 8.3 8.3 2.1
700................................................. 7.1 7.1 7.1 1.9
1000................................................ 5.0 5.0 5.0 1.4
1500................................................ 3.3 3.3 3.3 1.0
2000................................................ 2.5 2.5 2.5 0.7
2500................................................ 2.0 2.0 2.0 0.5
--------------------------------------------------------------------------------------------------------------------------------------------------------
Extreme environmental temperatures around the world are summarized
in Table-6. To ensure safety in extremely hot conditions, some fueling
pressure cycles are conducted at 50 [deg]C. To ensure safety in
extremely cold conditions, consistent with GTR No. 13 Phase 2
amendments, some fueling pressure cycles are conducted at -25 [deg]C.
The temperature -25 [deg]C is used instead of -40 [deg]C because
testing at -40 [deg]C is impractical during the test for expected on-
road performance. Specifically, a test apparatus must operate at well
below -40 [deg]C in order to maintain the temperature surrounding the
CHSS at -40 [deg]C. In addition, at -40 [deg]C, test laboratories
encounter difficulties such as freezing valves and failing o-ring
seals. This can significantly increase test cost. Furthermore, testing
conducted by
[[Page 27521]]
NHTSA found that, for the test for expected on-road performance,
testing at -25 [deg]C yields the same results as testing at -40
[deg]C.\73\ This change does not compromise the safety intent of the
test because in-tank gas temperatures will reach -40 [deg]C due to gas
expansion during depressurization. In addition, pressure cycling under
the extreme cold condition of -40 [deg]C is tested separately during
the test for performance durability. Therefore, -25 [deg]C is proposed
as the extreme cold temperature for the test for expected on-road
performance, which is consistent with the Phase 2 amendment to GTR No.
13. In summary, NHTSA is proposing 50 [deg]C for the high temperature
pressure cycles and -25 [deg]C for the cold temperature pressure
cycles.
---------------------------------------------------------------------------
\73\ DOT HS_811_832. Cumulative Fuel System Life Cycle and
Durability Testing of Hydrogen Containers, https://www.nhtsa.gov/sites/nhtsa.gov/files/811832.pdf.
Table 6--Extreme Environmental Temperatures Around the World
----------------------------------------------------------------------------------------------------------------
Extremes of
Frequency of sustained ambient
Temperature Areas that occurs exposure to this environmental
temperature (year) temperature used
for this test
----------------------------------------------------------------------------------------------------------------
Around 50 [deg]C...................... desert areas of lower 5 percent................ 50 [deg]C
latitude countries.
Less or equal to -40 [deg]C........... countries north of the 5 percent................ -40 [deg]C
45th parallel.
Less than -30 [deg]C.................. countries north of the 5 percent of vehicle life ..................
45th parallel.
----------------------------------------------------------------------------------------------------------------
Data source: Environment Canada 1971-2000.
As described above, hydrogen fueling stations typically pre-cool
hydrogen to between -40 [deg]C and -33 [deg]C. However, a fueling
station failure could result in the fueling station delivering hydrogen
at ambient temperature. This would lead to very high temperatures
inside the CHSS after a full fueling. To account for this risk, the
first 5 cycles in the ambient and extreme temperature gas pressure
cycling test are conducted with hydrogen fuel at between 15 [deg]C and
25 [deg]C, as opposed to the pre-cooled hydrogen between -40 [deg]C and
-33 [deg]C which is used for the remaining 495 cycles.
All pressure cycles are performed to 100 percent state-of-charge
(SOC). SOC is defined by the ratio of hydrogen density at a given
temperature and pressure to hydrogen density at NWP and 15 [deg]C.\74\
Specifying 100 percent SOC ensures an equivalent quantity of hydrogen
in the CHSS regardless of the resulting temperature and pressure. For
example, 100 percent NWP at 15 [deg]C corresponds to 80 percent NWP at
-40 [deg]C. In either case, however, the CHSS is at 100 percent SOC
(fully fueled).
---------------------------------------------------------------------------
\74\ Since the hydrogen gas density varies nonlinearly with
temperature and pressure, a table is provided in the regulatory text
for hydrogen density at different pressures and temperatures.
---------------------------------------------------------------------------
The first 10 cycles (cold cycles) are performed with the CHSS
stabilized with the external air temperature surrounding the CHSS at -
25 [deg]C at the beginning of the cycle. This ensures there is no
residual heat present from the previous fueling cycle and maximizes the
severity of the cold external temperature. However, the process to
equilibrate a storage system is time-consuming. As a result, the next
15 cycles are performed with an external air temperature surrounding
the CHSS of -25 [deg]C, but without CHSS equilibration to the external
temperature.
The next 25 cycles are performed with an external temperature of 50
[deg]C. For the first 5 of these cycles, the CHSS is stabilized with
the external air temperature surrounding the CHSS at the at the
beginning of the cycle. At this point, the external temperature to the
system is at its hottest, and the CHSS pressure is at its minimum. The
fueling process will then progressively heat the contents of the CHSS
until full (100 percent SOC). At this point, the CHSS reaches its
hottest possible interior temperature. In addition, these 25 cycles are
performed with the relative humidity over 80 percent surrounding the
CHSS. This adds the stress of excessive humidity which is common in
extreme hot climates. Specifically, the high humidity keeps a thin film
of water on surfaces where dissimilar metals may be in contact, such as
valve to tank interfaces or valve body to valve connection interfaces.
This water film adds the necessary conduction path to effect galvanic
corrosion. Galvanic corrosion can cause pitting and other forms of
metal loss which can degrade the strength of materials and impact
sealing surfaces. Therefore, it is important to include the stress
factor of humidity in the test for expected on-road performance
The next 200 cycles are performed with ambient external temperature
of (5 [deg]C to 35 [deg]C). This represents a normal ambient
temperature. After these 200 cycles (at a total cycle count of 250),
the extreme temperature static gas pressure leak/permeation test is
performed. This test is discussed in the next section. However, after
the completion of the permeation test, pressure cycling continues for
an additional 250 cycles.
The first 25 of these additional cycles (cycle count 251-275) are
performed with the extreme hot external temperature of 50 [deg]C. The
next 25 cycles (cycle count 276-300) are performed with the extreme
cold temperature -25 [deg]C. In this series, the order of extreme hot
and cold cycles is switched. This accounts for compounding stress from
transitioning from hot cycling to cold cycling, as opposed to the
previous series, which transitioned from cold to hot. The final 200
cycles (cycle count 301-500) are performed with ambient external
temperature of 5 [deg]C to 35 [deg]C. After the completion of cycling,
the extreme temperature static gas pressure leak/permeation test is
performed for a second time.
GTR No. 13 states that if system controls that are active in
vehicle service prevent the pressure from dropping below a specified
pressure, the test cycles during the ambient and extreme temperature
gas pressure cycling test must not go below that specified pressure. In
addition, GTR No. 13 states that if devices and/or controls are used in
the intended vehicle application to prevent an extreme internal
temperature, the test may be conducted with these devices and/or
controls in place. However, NHTSA's approach to testing involves the
agency independently purchasing (on the open market) and then testing
vehicles. With this approach, NHTSA has no way of determining what
system controls and/or devices are active in the vehicle,
[[Page 27522]]
because this information is typically proprietary and is not publicly
available. As a result, all cycles would be performed with an initial
pressure of between 1 MPa and 2 MPa and extreme internal temperatures
will not be prevented during cycling. Furthermore, and importantly for
safety, this is a condition that could occur in the event the system
controls and/or devices fail in service.
c. Extreme Temperature Static Gas Pressure Leak/Permeation Test
Leak and permeation are risk factors for fire hazards, particularly
when parking in confined spaces such as garages. The extreme
temperature static gas pressure leak/permeation test is designed to
simulate extended parking in a confined space under an elevated
temperature. In these conditions, hydrogen can leak or permeate from
the CHSS and slowly accumulate in the surrounding air. During the
extreme temperature static gas pressure leak/permeation test, the
pressurized CHSS at 100% SOC is held at 55 [deg]C for a period of up to
500 hours. Any hydrogen leakage and/or permeation from the CHSS cannot
exceed the limit of 46 milliliter/hour (mL/h) per liter of CHSS water
capacity. This limit is discussed below. The test may end before 500
hours if three consecutive hydrogen permeation rates separated by at
least 12 hours are within 10 percent of the prior rate because this
indicates a permeation steady state has been reached. NHTSA seeks
comment on how to accurately measure or otherwise determine the
permeation rate from the CHSS.
The leak/permeation limit is characterized by the many possible
combinations of vehicles and garages, and the associated test
conditions. The leak/permeation limit is defined to restrict the
hydrogen concentration from reaching 25 percent lower flammability
limit (LFL) by volume. The LFL of hydrogen is lowest concentration of
hydrogen in which a hydrogen gas mixture is flammable. National and
international standard bodies (such as National Fire Protection
Association [NFPA] and IEC) recognize 4 percent hydrogen by volume in
air as the LFL.\75\ The conservative 25 percent LFL limit accounts for
concentration non-homogeneities and is equivalent to 1 percent hydrogen
concentration in air.76 77
---------------------------------------------------------------------------
\75\ See Gases--Explosion and Flammability Concentration Limits.
https://www.engineeringtoolbox.com/explosive-concentration-limits-d_423.html.
\76\ Data for hydrogen dispersion behavior, garage and vehicle
scenarios, including garage sizes, air exchange rates and
temperatures, and the calculation methodology are found in the
following reference prepared as part of the European Network of
Excellence HySafe: P. Adams, A. Bengaouer, B. Cariteau, V. Molkov,
A.G. Venetsanos, ``Allowable hydrogen permeation rate from road
vehicles,'' https://h2tools.org/sites/default/files/2019-08/paper_-_part_1.pdf.
\77\ NFPA 30A-2015, Code for Motor Fuel Dispensing Facilities
and Repair Garages, 7.4.7.1, https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=30A.
---------------------------------------------------------------------------
Worst case ventilation in structures where hydrogen vehicles can be
parked is expected to be at or below 0.18 air changes per hour, but the
exact design value is highly dependent on the type and location of
structures in which the vehicles are parked. In the case of light
passenger vehicles, an extremely low air exchange rate (of 0.03
volumetric air changes per hour) has been measured in ``tight'' wood
frame structures (with plastic vapor barriers, weather-stripping on the
doors, and no vents) that are sheltered from wind and are very hot (55
[deg]C) with little daily temperature swings that can cause density-
driven infiltration. The resulting discharge limit for a light vehicle
that tightly fits into a garage of 30.4 cubic meters (m\3\) with 0.03
volumetric air exchange per hour is 150 mL/minute (at 115 percent NWP
for full fill at 55 [deg]C), corresponding to no more than 1 percent
hydrogen concentration in air.
In order to determine the leak/permeation limit for the expected
on-road performance test, consistent with GTR No. 13, the vehicle-level
150 mL/min leak/permeation limit is expressed in terms of allowable
leak/permeation for each container in the storage system at 55 [deg]C
and 115 percent NWP. This corresponds to 46 mL/hour(h)/Liter(L)-water-
capacity for each container in the storage system.\78\ The use of this
limit is applicable to light vehicles that are smaller or larger than
the base described above. If, for example, the total water capacity of
the light vehicle storage system is 330 L (or less) and the garage size
is 50 m\3\, then the 46 mL/h/L-water-capacity requirement results in a
steady-state hydrogen concentration of no more than 1 percent. This can
be shown by calculating the allowable discharge from the light vehicle
based on the requirement of 46 mL/h/L per container volume capacity
(that is, 46 mL/h/L x 330L/(60 min/h) = 253 mL/min) which is similar to
the allowable discharge based on the garage size of 50 m\3\ with an air
exchange rate of 0.03 volumetric air exchanges per hour (that is, 150
mL/min x 50 m\3\/30.4 m\3\ = 247 mL/min). Since both results are
essentially the same, the hydrogen concentration in the garage is not
expected to exceed 1 percent for light vehicles with storage systems of
330L (or less) in 50 m\3\ garages.
---------------------------------------------------------------------------
\78\ Data for hydrogen dispersion behavior, garage and vehicle
scenarios, including garage sizes, air exchange rates and
temperatures, and the calculation methodology are found in the
following reference prepared as part of the European Network of
Excellence HySafe: P. Adams, A. Bengaouer, B. Cariteau, V. Molkov,
A.G. Venetsanos, ``Allowable hydrogen permeation rate from road
vehicles,'' https://h2tools.org/sites/default/files/2019-08/paper_-_part_1.pdf.
---------------------------------------------------------------------------
Since the discharge limit has been found to be reasonably scalable
depending on the vehicle size, the discharge limit for alternative
vehicle sizes in tight-fitting garages with 0.03 volumetric air
exchanges per hour can be determined from the 150 mL/minute discharge
limit computed above using a scaling factor R computed as:
R = (Vwidth+1) (Vheight+0.5)
(Vlength+1)/30.4
where:
Vlength, Vwidth, and Vheight are
the dimensions of the vehicle in meters,
Similarly, the use of 46 mL/h/L-water-capacity requirement for
storage system containers is also scalable to larger medium-duty and
heavy-duty vehicles. Figure-7 shows the required volumetric air
exchange rate that would result in less than 25 percent LFL of hydrogen
by volume in garages of various sized vehicles equipped with CHSS that
have no more than a 46 mL/L/H permeation rate. Examples of current or
currently-planned hydrogen vehicles shown in Figure-7 indicate that the
required ventilation rate for garages of large vehicles (buses and
tractor-trailers) is lower than that of small vehicles (passenger
cars). Light hydrogen vehicles which can possibly be parked in tight
garages (with as low as 0.03 volumetric air changes per hour) are
required to have permeation/leak rate less than of 46 mL/hour(h)/
Liter(L)-water-capacity for each container in the vehicle's CHSS.\79\
Even though medium-duty and heavy-duty vehicles are not expected to be
parked in such ``tight'' garages as is the case with light vehicles, in
order to better meet the safety need, we conservatively assume an
equivalent rate of 0.03 volumetric air exchanges for garages of these
vehicles.
---------------------------------------------------------------------------
\79\ This leak/permeation limit for each container ensures that
the hydrogen concentration is lower than 25 percent of the lower
flammability limit (LFL) by volume and the hydrogen concentration in
air is less than 1 percent.
---------------------------------------------------------------------------
[[Page 27523]]
While it is foreseeable that medium-duty and heavy-duty vehicles may be
parked in more open (naturally-ventilated) or mechanically-ventilated
spaces, the 46 mL/h/L-water-capacity requirement for storage system
containers provides a safety margin in the event of mechanical
ventilation failures.
[GRAPHIC] [TIFF OMITTED] TP17AP24.006
Figure-7: Required Volumetric Air Exchange Rate (Ventilation Rate) of
Enclosed Space Surrounding a Hydrogen Vehicle That Results in Less Than
25 Percent Lower Flammability Limit of Hydrogen by Volume
In addition to the required leak/permeation limit discussed above,
GTR No. 13 also includes a localized leak requirement. This requirement
is based on the SAE technical paper 2008-01-0726, Flame Quenching
Limits of Hydrogen Leaks.\80\ This paper states that the lowest
possible flammable flow for hydrogen is about 0.005 milligrams per
second (mg/s) (3.6 normal millilitres per minute (NmL/min)).\81\ As a
result, if a hydrogen permeation rate over 0.005 mg/s is detected, a
localized leak test ensures that the hydrogen is not all emanating from
the same localized area of the container. This leak test is conducted
as a bubble test. In a bubble test, a surfactant solution is applied
across the CHSS and the tester observes for the formation of bubbles in
the solution resulting from any leaks. If bubbles are detected, the
test lab estimates the leak rate based on the average size of the
bubbles and the number of bubbles generated per unit of time.
---------------------------------------------------------------------------
\80\ SAE Technical report 2008-01-0726. Flame Quenching Limits
of Hydrogen Leaks. Figure 3 to Figure 9. https://www.sae.org/publications/technical-papers/content/2008-01-0726/.
\81\ A normal milliliter, also known as a standard cubic
centimeter, represents the volume a gas would occupy at standard
temperature (0 [deg]C) and standard pressure (1 atmosphere).
---------------------------------------------------------------------------
However, NHTSA is concerned that this requirement would not meet
the Safety Act requirement for FMVSSs to be objective, due to the
subjective estimation of bubble sizes. Therefore, the localized leak
requirement has not been included in FMVSS No. 308. Furthermore, NHTSA
believes that the primary safety risk of accumulating hydrogen is
already addressed by the overall permeation limit of 46 mL/h/L-water-
capacity. NHTSA seeks comment on not including the localize leak
requirement during the extreme temperature static gas pressure leak/
permeation test. If commenters believe it should be included, NHTSA
requests that they explain (1) how they believe it could be made more
objective and (2) how specifically it would add to the standard's
ability to meet the safety need.
d. Residual Pressure Test & Residual Strength Burst Test
The residual pressure test and residual strength burst test are
conducted in the same manner and for the same reasons discussed above
for the test for performance durability.
7. Test for Service Terminating Performance in Fire
Vehicle fire presents a severe risk to the safe containment of
hydrogen. Fire can rapidly degrade the container while simultaneously
increasing the pressure inside the container. To avoid the possibility
of burst, CHSS should be designed to vent their pressurized contents
when exposed to fire. Under the proposed standard, the CHSS must vent
its pressurized hydrogen during the test for service terminating
performance in fire, discussed below, which simulates a vehicle fire.
The CHSS must expel its contents (high pressure hydrogen gas) in a
controlled manner through its TPRD(s) without the occurrence of burst.
A comprehensive examination of CNG container in-service failures
between 2000 and 2008 showed that the majority of fire incidents
occurred on storage systems that did not utilize properly designed
TPRDs.\82\ The in-service failures resulted when TPRDs did not respond
to protect the container due to the lack of adequate heat exposure on
the TPRDs, while a small ``localized'' fire degraded the container wall
elsewhere, eventually causing the container to burst. Prior to GTR. No.
13, localized fire exposure had not been addressed in regulations or
industry standards. The test for service terminating performance in
fire
[[Page 27524]]
addresses both localized and engulfing fires with two respective test
stages.
---------------------------------------------------------------------------
\82\ SAE Technical Paper 2011-01-0251. Establishing Localized
Fire Test Methods and Progressing Safety Standards for FCVs and
Hydrogen Vehicles. https://www.sae.org/publications/technical-papers/content/2011-01-0251/.
---------------------------------------------------------------------------
The test for service terminating performance in fire evaluates the
CHSS. It is possible that vehicle manufacturers may add additional fire
protection features as part of overall vehicle design, and GTR No. 13
includes the option of conducting CHSS fire testing with vehicle
shields, panels, wraps, structural elements, and other features as
specified by the manufacturer. However, adding vehicle-level protection
features is not practical for testing. Furthermore, NHTSA believes that
it is important for safety that the CHSS itself can withstand fire and
safely vent in the event its shielding is compromised--for example, if
a crash damages the shielding, and the shielding was an integral part
of the CHSS's ability to withstand fire, then the CHSS should be able
to vent properly before it explodes. As a result, vehicle-level
protection measures are not evaluated by the test for service
terminating performance in fire. However, if a CHSS includes container
attachments, these attachments are included in the fire test. NHTSA
seeks comment on excluding vehicle-specific shielding and on including
container attachments as part of the fire test, particularly in the
case of container attachments which can be removed using a process
specified by the manufacturer.
The fire test temperature targets set forth in GTR No. 13 are based
on vehicle fire experiments conducted by the Japanese Automobile
Research Institute (JARI).\83\ Some key findings from these vehicle-
level fire experiments are as follows:
---------------------------------------------------------------------------
\83\ Id.
---------------------------------------------------------------------------
About 30 to 50 percent of the JARI vehicle fires resulted
in a ``localized'' fire. In these cases, the data indicated the
container could have been locally degraded before TPRDs would have
activated.
Thermal gravimetric analysis (TGA) indicated that
composite container materials begin to degrade rapidly at 300 [deg]C.
While the vehicle fires often lasted 30-60 minutes, the
period of localized fire container degradation lasted less than 10
minutes.
Peak temperatures on the test containers' surfaces reached
700 [deg]C during the localized fire stages.
The rise in peak temperature near the end of the localized
fire period often indicated the transition to an engulfing fire.
Peak temperatures on the test containers' surfaces reached
1000 [deg]C during the engulfing fire stage.
Based upon these experiments, temperature limits were defined in
GTR No. 13 to characterize the thermal exposure during the localized
and engulfing fire stages:
The minimum container surface temperature during the
localized fire stage for the side of the container facing the fire was
set to 450 [deg]C to create a challenging but realistic thermal
condition.
The maximum container surface temperature during the
localized fire stage for the side of the container facing the fire and
for the sides of the container was set to 700 [deg]C.
The minimum container surface temperature during the
engulfing fire stage on the side of the container facing the fire was
set to 600 [deg]C, because this was the lowest value observed for this
side of the container during the engulfing fire stage.
A maximum temperature limit on the bottom of the container
during the engulfing stage was not necessary as the temperature is
naturally limited.
The updates to the fire test by the IWG of GTR No. 13 Phase 2
focused on improving the repeatability and reproducibility across test
laboratories. Two significant improvements to the fire test are (1) the
use of a pre-test checkout procedure and (2) basic burner
specifications. The pre-test checkout requires conducting a preliminary
fire exposure on a standardized steel container to verify that
specified fire temperatures can be achieved for the localized and
engulfing fire segments of the test prior to conducting the fire test
on a CHSS. During this pre-test checkout, the fuel flow is adjusted to
achieve fire temperatures within the limits given in Table-7 as
measured on the surface of the pre-test steel container. The use of a
pre-test steel container instead of an actual CHSS improves the
accuracy and repeatability of the test because it avoids possible
container material degradation that could affect the temperature
measurements.
Table 7--Pre-Test Checkout Temperature Requirements
----------------------------------------------------------------------------------------------------------------
Temperature range on
Fire stage bottom of pre-test Temperature range on sides Temperature range on top of
container of pre-test container pre-test container
----------------------------------------------------------------------------------------------------------------
Localized.................. 450 [deg]C to 700 less than 750 [deg]C........ less than 300 [deg]C.
[deg]C.
Engulfing.................. Average temperatures of Not applicable.............. Average temperatures of the
the pre-test container pre-test container surface
surface measured at measured at the three top
the three bottom locations must be at least
locations must be 100 [deg]C, and when
greater than 600 greater than 750 [deg]C,
[deg]C. must also be less than the
average temperatures of the
pre-test container surface
measured at the three
bottom locations.
----------------------------------------------------------------------------------------------------------------
In addition to temperature requirements, GTR No. 13 also specifies
required heat release rates per unit area (HRR/A) during the localized
and engulfing fire stages. The HRR/A is calculated using the lower
heating value (LHV) of the fuel, which is measured in megajoules of
energy released per kilogram of fuel consumed. To obtain HRR/A, the
fuel flow rate is multiplied by LHV and then divided by the burner
area. GTR No. 13 specifies a standardized calculation for burner area.
NHTSA has considered the specification for HRR/A and determined that it
could result in over-specification of the test parameters, potentially
making it very difficult to conduct the test. In addition, NHTSA
believes that the detailed temperature specifications for the pre-test
container during the pre-test checkout are sufficient to ensure
repeatability and reproducibility of the test.\84\ Therefore, NHTSA is
not proposing specifications for HRR/A. NHTSA seeks comment on this
decision.
---------------------------------------------------------------------------
\84\ Testing conducted to support enhancement of the fire test
specifications in GTR No. 13 Phase 2 indicated that the container
surface temperature specifications in the pre-test container fire
test along with the burner temperatures provided the needed
repeatability and reproducibility of the test.
---------------------------------------------------------------------------
[[Page 27525]]
The dimensions of the pre-test steel container for the pre-test
checkout are similar to those of the containers from the JARI vehicle
fire tests. The standard pre-test steel container is fabricated from
12-inch Schedule 40 NPS pipe along with end caps. The diameter of this
---------------------------------------------------------------------------
pipe is 12 inches (304 mm), while the length is:
at least 800 mm
not greater than 1.65 m
greater than or equal to the length of the CHSS to be tested,
unless the CHSS is greater than 1.65 m
The pre-test steel container is instrumented with thermocouples in
the same manner as the containers in the JARI vehicle fire tests and
mounted above the burner in the same manner as the CHSS to be fire
tested. Thermocouples are located along the cylindrical section of the
pre-test container at the bottom surface exposed to the burner flame,
mid-height along the left and right side of the cylindrical surface,
and top surface opposite the direct exposure to the burner flame.
Example thermocouple locations are shown below in Figure-8.
[GRAPHIC] [TIFF OMITTED] TP17AP24.007
Figure-8: Thermocouple Locations for the Pre-Test Checkout
The positioning of the pre-test container relative to the localized
and engulfing zones of the burner in the pre-test checkout must be
consistent with the positioning of the CHSS over the burner that is to
be tested.
The three thermocouples along the bottom (labeled TBL25, TBC25,
TBR25 in Figure-8) are considered burner monitor thermocouples. These
thermocouples are positioned 25 mm below the pre-test container. Since
these thermocouples are intended to monitor the burner, an alternative
would be to position these thermocouples relative to the burner itself.
NHTSA seeks comment on whether it is preferable to position the burner
monitor thermocouples relative to the pre-test container or relative to
the burner.
The pre-test checkout is performed at least once before the
commissioning of a new test site. Additionally, if the burner and test
setup is modified to accommodate a test of different CHSS
configurations than originally defined or serviced, then repeat of the
pre-test checkout is needed prior to performing CHSS fire tests. NHTSA
seeks comment on the frequency of conducting this pre-test checkout for
ensuring repeatability of the fire test on CHSS.
After the pre-test checkout is satisfactorily completed, the steel
pre-test container is removed and the CHSS to be fire tested is mounted
for testing. The CHSS fire test is then conducted with fuel flow
settings identical to the pre-test checkout. The profile of the CHSS
fire test is shown in Figure-9. During the CHSS fire test, the only
thermocouples used are the burner monitor thermocouples, which are
positioned 25 mm below the bottom of the CHSS. Temperatures on the
surface of the CHSS will vary naturally based on interactions with the
flames, and these temperatures are not controlled during the CHSS fire
test. The burner monitor thermocouples are used only to ensure the
burner is producing a fire closely matching the pre-test checkout.
The localized fire continues for a total of 10 minutes and then the
test transitions to the engulfing stage which continues until the test
is complete (test completion is discussed below). The minimum value for
the burner monitor temperature during the localized fire stage
(TminLOC) is calculated by subtracting 50 [deg]C from the
minimum of the 60-second rolling average of the burner monitor
temperature in the localized fire zone of the pre-test checkout. The
minimum value for the burner monitor temperature during the engulfing
fire stage (TminENG) is calculated by subtracting 50 [deg]C
from the minimum of the 60-second rolling average of the average burner
monitor temperature in the engulfing fire zone of the pre-test
checkout.
[[Page 27526]]
[GRAPHIC] [TIFF OMITTED] TP17AP24.008
Figure-9: Temperature Profile of the Fire Test
NHTSA has conducted CHSS fire testing to verify the feasibility of
the test for service termination performance in fire as currently
proposed. Overall, the testing was completed successfully,
demonstrating the feasibility of the proposed test for service
terminating performance in fire. The results of this testing are
summarized in the test report GTR No. 13 Fire and Closures Tests.\85\
---------------------------------------------------------------------------
\85\ See the report titled ``GTR No. 13 Fire and Closures
Tests'' submitted to the docket of this NPRM. This report will also
be submitted to the National Transportation Library. https://rosap.ntl.bts.gov/.
---------------------------------------------------------------------------
In some cases during testing, however, temperatures measured at the
burner monitor thermocouples did not satisfy the required
TminENG. NHTSA's testing indicated that the airflow during
the pre-test may be different from that of the CHSS if the pre-test
container length is substantially different from that of the CHSS to be
tested. The difference in air flow between the two tests could cause
differences in fire input to the CHSS compared to the pre-test
container. Therefore, NHTSA recommends that for CHSS of length between
600 mm and 1650 mm, the difference in the length of the pre-test
container and the CHSS be no more than 200 mm. NHTSA seeks comment on
whether this recommendation should be a specification for the pre-test
container.
In addition, NHTSA seeks comment on the requirement for
TminENG. In particular, NHTSA seeks comment on allowing for
a wider variation than 50 [deg]C below the pre-test temperatures. A
variation of 50 [deg]C is small in the context of fire temperatures,
and such a small variation limit may make the test more difficult for
test labs to conduct. Furthermore, as currently specified,
TminLOC and TminENG would be time-dependent
variables because they are based on a time-dependent rolling average.
Having TminLOC and TminENG being time-dependent
is complex and would make the testing difficult to monitor. NHTSA seeks
comment on a simpler calculation for TminLOC and
TminENG that will result in constant values for
TminLOC and TminENG. NHTSA proposes that
TminLOC be calculated by subtracting 50 [deg]C from the
minimum value of the 60-second rolling average of the burner monitor
temperature in the localized fire zone of the pre-test checkout.
Similarly, NHTSA proposes that TminENG be calculated by
subtracting 50 [deg]C from minimum value of the 60-second rolling
average of the average of the three burner monitor temperatures during
the engulfing fire stage of the pre-test checkout. NHTSA seeks comment
on whether these revised calculations for TminLOC and
TminENG should be required.
GTR No. 13 specifies additional pre-test checkout procedures
intended for irregularly shaped CHSS which are expected to impede air
flow through the burner. These procedures involve constructing a pre-
test plate having similar dimensions to the CHSS to be tested. A second
pre-test checkout is conducted using the pre-test plate and using the
burner monitor thermocouples. If the burner monitor thermocouple
temperatures do not satisfy both TminLOC and
TminENG, then the pre-test plate is raised by 50 mm, and a
third pre-test checkout is conducted. GTR No. 13 specifies that this
process is repeated until burner monitor thermocouple temperatures
satisfy TminLOC and TminENG. NHTSA has considered
this additional pre-test process and determined that it is unnecessary.
The goal of the pre-test checkout is a repeatable and reproducible fire
exposure among different testing facilities. NHTSA has determined there
is no need for design-specific modification to the fire test procedure.
Furthermore, the additional pre-test procedures add considerable
complexity to the test procedure, and as a result could undermine the
repeatability and reproducibility of the fire test. Therefore, NHTSA is
not proposing these additional pre-test procedures. NHTSA seeks comment
on this decision. If commenters believe that the additional pre-test
procedures are necessary, NHTSA requests that they explain (1) how they
would improve the safety outcome of the standard, and (2) how they
would improve the
[[Page 27527]]
repeatability and reproducibility of the fire test.
Liquefied petroleum gas, also known as liquified propane gas or
simply LPG, is the selected fuel for the test burner because it is
globally available and easily controllable to maintain the required
thermal conditions. The use of LPG was deemed adequate by the IWG to
reproduce the thermal conditions on the steel container that occurred
during the JARI vehicle fire tests without concerns of carbon formation
that can occur with other liquid fuels. The relatively low hydrogen to
carbon (H/C) ratio of LPG at approximately 2.67 allows the flame to
display flame radiation characteristics (from carbon combustion
products) more similar to petroleum fires (with a H/C of roughly 2.1)
than natural gas, for example, which has an H/C ratio of approximately
4.0. Also, The LPG flame is more uniform and is easier to control than
natural gas and gasoline flames. For this reason, LPG fuel is the
choice for most testing purposes to improve the repeatability and
reproducibility of the test.
To further improve test reproducibility, a burner configuration is
defined in S6.2.5.1 with localized and engulfing fire zones. The burner
configuration specifications are listed in Table-8 below.
Table-8--Burner Specifications
------------------------------------------------------------------------
Item Description
------------------------------------------------------------------------
Nozzle Type............................ Liquefied petroleum gas fuel
nozzle with air pre-mix.
LPG Orifice in Nozzle..... 1 mm 0.1 mm inner
diameter.
Air Ports in Nozzle....... Four holes, 6.4 mm
0.6 mm inner diameter.
Fuel/Air Mixing Tube in 10 mm 1 mm inner
Nozzle. diameter.
Number of Rails........................ Six.
Center-to-center Spacing of Rails...... 105 mm 5 mm.
Center-to-center Nozzle Spacing Along 50 mm 5 mm.
the Rails.
------------------------------------------------------------------------
These specifications allow the fire test to be performed without a
burner development program. NHTSA believes that use of a standardized
burner configuration is a practical way of conducting fire testing and
should reduce variability in test results through commonality in
hardware. Flexibility is provided to adjust the length of the engulfing
fire zone to match the CHSS length, up to a maximum of 1.65 m. This
allows test laboratories to reduce burner fuel consumption when testing
small containers. The width of the burner, however, is fixed at 500 mm
for all fire tests, regardless of the width or diameter of the CHSS
container to be tested, so that each CHSS is evaluated with the same
fire condition regardless of size. The length of the localized fire
zone is also fixed to 250 mm for all fire tests. An example of a
typical burner is shown in Figure-10 and Figure-11 below. NHTSA seeks
comment on a specification for the burner rail tubing shape and size,
which can affect the spacing between the nozzle tips.
GTR No. 13 specifies that the CHSS is rotated relative to the
localized burner to minimize the ability for TPRDs to sense the fire
and respond. GTR No. 13 specifies establishing a worst-case based on
the specific CHSS design. However, NHTSA is concerned that establishing
a worst-case based on a specific design may be subjective. NHTSA
instead proposes that the CHSS is positioned for the localized fire by
orienting the CHSS relative to the localized burner such that the
distance from the center of the localized fire exposure to the TPRD(s)
and TPRD sense point(s) is at or near maximum. This provides a
challenging condition where the TPRD(s) may not sense the localized
fire. The engulfing fire zone includes the localized fire zone and
extends along the complete length of the container, in one direction,
towards the nearest TPRD or TPRD sense point, up to a maximum burner
length of 1.65 m. Some examples of possible burner orientations are
shown in Figure-12 and Figure-13. NHTSA seeks comment on the proposed
orientation of the CHSS relative to the localized burner.
BILLING CODE 4910-59-P
[GRAPHIC] [TIFF OMITTED] TP17AP24.009
Figure-10: Example Burner Top View
[[Page 27528]]
[GRAPHIC] [TIFF OMITTED] TP17AP24.010
Figure-11: Example Burner Side View
[GRAPHIC] [TIFF OMITTED] TP17AP24.011
Figure-12: Example Burner Orientations With Single TPRD
[[Page 27529]]
[GRAPHIC] [TIFF OMITTED] TP17AP24.012
Figure-13: Example Burner Orientations With Two TPRDs
BILLING CODE 4910-59-C
When testing is conducted outdoors, wind shielding is required to
prevent wind from interfering with the flame temperatures. In order to
ensure that wind shields do not obstruct the drafting of air to burner,
which could cause variations in test results, the wind shields need to
be at least 0.5 m away from the CHSS being tested. Finally, for
consistency, the wind shielding used for the pre-test checkout must be
the same as that for the CHSS fire test. NHTSA seeks comment on whether
specifications for wind shielding should be provided in the regulatory
text of the standard, and if so, what the specifications should be. As
an additional approach to addressing wind interference with flame
temperatures, NHTSA is considering for the final rule to limit average
wind velocity during testing to 2.24 meters/second, as in FMVSS No.
304.\86\ NHTSA seeks comment on limiting wind speed during testing.
---------------------------------------------------------------------------
\86\ FMVSS No. 304, ``Compressed natural gas fuel container
integrity,'' https://www.ecfr.gov/current/title-49/subtitle-B/chapter-V/part-571/subpart-B/section-571.304.
---------------------------------------------------------------------------
In order to minimize hazard, jet flames occurring anywhere other
than a TPRD outlet, such as the container walls or joints, cannot
exceed 0.5 meters in length. NHTSA seeks comment on how to accurately
measure jet flames.
Consistent with GTR No. 13, if venting occurs though the TPRD(s),
the venting is required to be continuous so the vent lines do not
experience periodic flow blockages which could interfere with proper
venting. The fire test is completed successfully after the CHSS vents
its contents and the CHSS pressure falls to less than 1 MPa. If the
CHSS has not vented below 1 MPa within 60 minutes for vehicles with a
GVWR of 4,536 kg (10,000 pounds) or less, or 120 minutes for vehicles
with a GVWR over 4,536 kg (10,000 pounds), the CHSS is considered to
have failed the test.
The value of 1 MPa is selected such that the risk of stress rupture
after venting is minimal. The time limits are selected to represent
long-lasting fires such as battery fires or vehicle fires occurring
inside of building structures. The time limit for heavy vehicles is
longer because heavy vehicles are larger in size and often carry cargo
or refuse. Both of these factors tend to prolong fire duration.
8. Tests for Performance Durability of Closure Devices
Like the CHSS, closure devices (like the TPRD, check valve and
shut-off valve) must be durable and maintain their expected operational
capabilities during their lifetime of service. Closure devices must
demonstrate their operability and durability in service by completing a
series of performance tests as discussed below. Closure device
operability and durability is essential for the integrity of the CHSS
because these devices isolate the high-pressure hydrogen from the
remainder of the fuel system and the environment. While the closure
devices are challenged in the CHSS performance tests above, additional
specific tests may further enhance safety. In addition, specific
component testing enables equivalent components to be safely exchanged
in a CHSS.
The tests for performance durability of closure devices in GTR No.
13 are closely consistent with the industry standards CSA/ANSI HPRD 1-
2021, Thermally activated pressure relief devices for compressed
hydrogen vehicle fuel containers, and CSA/ANSI HGV 3.1-2022, Fuel
System Components for Compressed Hydrogen Gas Powered
Vehicles.87 88 The tests for performance durability of
closure devices carry a significant test burden. To evaluate a single
TPRD design, 13 TPRD units are required for a total of 29 individual
tests (some units undergo multiple tests in a sequence). Similarly, to
evaluate a single shut-off valve or check valve, 8 units are required
for a total of 17 individual tests. While NHTSA is proposing these
requirements to be consistent with GTR No. 13, NHTSA seeks comment on
whether testing of this extent is necessary to meet the need for
safety, or whether it is still possible to meet the need for safety
with a less-burdensome test approach or with a subset of the test for
performance durability of closure devices. If commenters believe
another approach or subset of tests is appropriate and meets the need
for safety, NHTSA requests that commenters provide specific detail on
[[Page 27530]]
(1) the alternate approach or subset of tests and (2) how it meets the
need for safety adequately.''
---------------------------------------------------------------------------
\87\ See. https://webstore.ansi.org/standards/csa/csaansihprd2021.
\88\ See. https://webstore.ansi.org/standards/csa/csaansihgv2015r2019.
---------------------------------------------------------------------------
Furthermore, FMVSS represent minimum performance requirements for
safety. FMVSS does not address issues such as component reliability or
best practices. These considerations are left to industry standards.
NHTSA seeks comment on whether a reduced subset of the tests for
performance durability of closure devices could ensure safety with a
lower overall test burden. In such a subset, only those tests directly
linked to critical safety risks would be included.
The tests for performance durability of closure devices are
conducted on finished components representative of normal production.
To enable outdoor testing without special temperature controls that
would increase testing costs, NHTSA proposes that testing be conducted
at an ambient temperature of 5 [deg]C to 35 [deg]C, unless otherwise
specified. In addition, GTR No. 13 specifies that all tests be
performed using either:
Hydrogen gas compliant with SAE J2719_202003, Hydrogen
Fuel Quality for Fuel Cell Vehicles, or
Hydrogen gas with a hydrogen purity of at least 99.97
percent, less than or equal to 5 parts per million of water, and less
or equal to 1 part per million particulate, or
A non-reactive gas instead of hydrogen.
The standard J2719_202003 specifies maximum concentrations of
individual contaminants such as methane and oxygen. Limiting these
individual contaminants are critical for fuel cell operation, however,
they are unlikely to affect the results of the tests for performance
durability of closure devices.
As a result, FMVSS No. 308 will only require hydrogen with a purity
of at least 99.97 percent, less than or equal to 5 parts per million of
water, and less or equal to 1 part per million particulate. NHTSA seeks
comment on any other impurities that could affect the results of the
tests for performance durability of closure devices.
Using a non-reactive gas for testing would have the benefit of
reducing the test lab safety risk related to handling pressurized
hydrogen. However, it is not clear if replacing hydrogen with a non-
reactive gas reduces stringency and therefore may not adequately
address the safety need. As a result, this option has not been proposed
in FMVSS No. 308. NHTSA seeks comment on whether testing with a non-
reactive gas instead of hydrogen reduces test stringency. If commenters
believe (and can explain) that it does not reduce test stringency,
NHTSA requests that they identify a suitable non-reactive gas to
replace hydrogen, such as helium or nitrogen, and explain why it is
suitable.
a. TPRD
Failure of a TPRD to properly vent in the event of a fire could
lead to burst. Accordingly, TPRDs must demonstrate operability and
durability in service by successfully completing the applicable tests
for performance durability of closure devices. This is a series of TPRD
performance tests with requirements discussed below.
GTR No. 13 does not consider the possibility of the TPRD activating
during the pressure cycling test, temperature cycling test, salt
corrosion test, vehicle environment test, stress corrosion cracking
test, drop and vibration test, or leak test. The temperatures applied
during these tests are not characteristic of fire and therefore should
not cause the TPRD to activate. TPRD activation in the absence of
temperatures characteristic of a fire indicates that the TPRD is not
functioning as intended and presents a safety risk due to the hazards
associated with TPRD discharge. As a result, NHTSA is proposing that if
the TPRD activates at any point during the pressure cycling test,
temperature cycling test, salt corrosion test, vehicle environment
test, stress corrosion cracking test, drop and vibration test, or leak
test, that TPRD will be considered to have failed the test. NHTSA seeks
comment on this proposed requirement.
(1) Pressure Cycling Test
Similar to the CHSS test for expected on-road performance, the
pressure cycling test would evaluate a TPRD's ability to withstand
repeated pressurization and depressurization. One TPRD unit undergoes
15,000 internal pressure cycles with hydrogen gas. While the proposed
15,000 pressure cycles for the TPRD is consistent with GTR No. 13,
NHTSA notes that this number of cycles is higher than the maximum
11,000 pressure cycles applied to containers. NHTSA seeks comment on
the need for 15,000 pressure cycles for TPRDs. The testing is performed
under the conditions shown in Table-9 with a maximum cycling rate of 10
cycles per minute.
Table 9--Test Conditions
------------------------------------------------------------------------
Temperature
Pressure Number of cycles ([deg]C)
------------------------------------------------------------------------
2 MPa to 150% NWP................. First 10............ 85
2 MPa to 125% NWP................. Next 2,240.......... 85
2 MPa to 125% NWP................. Next 10,000......... 20
2 MPa to 80% NWP.................. Final 2,750......... -40
------------------------------------------------------------------------
The pressure cycling test is designed to replicate fueling events
during service. This is important because over time, repeated fueling
events can produce fatigue failures. NHTSA seeks comment on the number
of TPRD pressure cycles. The first 10 cycles use 150 percent NWP to
replicate over-pressurization events at fueling stations. The remaining
cycles are conducted to 125 percent NWP for the reasons discussed above
for the baseline pressure cycle test.
The test temperature of 85 [deg]C for the first 2,250 cycles and
the test temperature of -40 [deg]C for the final 2,750 cycles are
selected to replicate the extreme hot and cold environments described
above for the test for performance durability. After the completion of
pressure cycling, the TPRD units are subjected to the Leak Test,
Benchtop Activation Test, and Flow Rate Test. These three tests,
discussed below, verify the essential functions of the TPRD.
(2) Accelerated Life Test
A TPRD needs to activate at its intended activation temperature,
but also must not activate prematurely due to a long-duration exposure
to elevated temperature that is below its activation temperature.
Holding the TPRD at an elevated temperature TL could lead to creep
failure of the materials within the TPRD and result in a false
activation. The purpose of the accelerated life test is to evaluate the
TPRD's ability to activate at intended activation
[[Page 27531]]
temperature, while demonstrating resistance to creep failure at
elevated temperatures that are below its activation temperature.
During the test, the TPRD units are pressurized with hydrogen at
125 percent NWP and placed in a temperature-controlled environment. One
unit is tested at the manufacturer's specified activation temperature,
Tf, and one unit is tested at the accelerated life temperature, TL,
given by the expression: \89\
---------------------------------------------------------------------------
\89\ Details are provided in the technical document ``New
equation for calculating accelerated life test temperature.pdf''
submitted to the docket of this NPRM.
[GRAPHIC] [TIFF OMITTED] TP17AP24.013
where [beta] = 273.15 if T is in Celsius and [beta] = 459.67 if T is in
Fahrenheit, T85 = 85 [deg]C (185 [deg]F), and Tf is the
manufacturer's specified activation temperature. The unit tested at Tf
must activate in less than 10 hours and the unit tested at TL must not
activate in less than 500 hours. The required 500 hours without
activation demonstrates the unit's resistance to creep.
(3) Temperature Cycling Test
Similar to the container and CHSS, the TPRD must be able to
withstand extreme temperatures while in service. A study found that
pressure release devices at extreme cold temperature as low as -40
[deg]C could cause a TPRD gas release failure.\90\ The temperature
cycling test evaluates a TPRD's ability to withstand extreme
temperature conditions that may lead to gas release failures when
combined with pressure cycling. The TPRD is first exposed to 15 thermal
cycles by alternating between hot (85 [deg]C) and cold (-40 [deg]C)
temperature baths. This is to simulate rapid swings in environmental
temperature, which can stress the TPRD through thermal expansion and
contraction. The TPRD is then pressure cycled in the cold bath for 100
cycles at 80 percent NWP to simulate fueling and defueling in an
extreme cold environment. After these stresses have been applied, the
TPRD is subjected to the low-temperature condition Leak Test, Benchtop
Activation Test, and Flow Rate Test. These three tests, discussed
below, verify the essential functions of the TPRD. Only the low-
temperature condition leak test is conducted after the temperature
cycling test because leaks are most likely to occur at low
temperatures.
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\90\ Livio Gambone et al., Performance testing of pressure
relief devices for NGV cylinders, June 1997.
---------------------------------------------------------------------------
(4) Salt Corrosion Resistance Test
The purpose of the salt corrosion resistance test is to verify that
the TPRD can withstand an extreme external salt corrosion environment.
The test occurs in a chamber designed to coat the TPRD with atomized
droplets of salt solution. This creates a highly corrosive environment.
The chamber cycles through wet and dry stages to maximise corrosion
affects. The parameters for this test, such as the chamber design, the
salts and water used, the salt concentrations, temperatures, humidity
levels and cycle times are all based on HGV 3.1-2022 and HPRD 1-
2021.91 92 93 After the salt corrosion exposure, the TPRD
units are subjected to the Leak Test, Benchtop Activation Test, and
Flow Rate Test. These tests, discussed below, verify the essential
functions of the TPRD. NHTSA seeks comment on the clarity and
objectivity of the salt corrosion resistance test procedure. If
commenters have suggestions on how to change the salt corrosion
resistance test procedure, NHTSA asks that they please explain how
their suggested changes improve the clarity and objectivity, and how
they continue to meet the need for safety represented by this test.
---------------------------------------------------------------------------
\91\ CSA/ANSI HGV 3.1-2022 Fuel System Components For Compressed
Hydrogen Gas Powered Vehicles.
\92\ CSA/ANSI HPRD 1-2021 Thermally activated pressure relief
devices for compressed hydrogen vehicle fuel containers.
\93\ HGV 3.1, HPRD 1, GTR No. 13, and the proposed FMVSS No. 308
reference the standards ASTM D1193-06(2018), Standard Specification
for Reagent Water and ISO 6270-2:2017 Determination of resistance to
humidity. ASTM D1193-06(2018) provides specification for the water
to be used during salt corrosion resistance testing. https://www.astm.org/d1193-06r18.html.
ISO 6270-2:2017 provides specifications for the cyclic corrosion
chamber to be used. https://www.iso.org/standard/64858.html.
These two standards would be incorporated by reference into the
proposed FMVSS No. 308. A summary of these two standards is provided
in Section V. Regulatory Analyses and Notices of this notice.
---------------------------------------------------------------------------
(5) Vehicle Environment Test
The purpose of the vehicle environment test is to demonstrate that
the TPRD can withstand exposure to chemicals that might be encountered
during on-road service. Prior to testing, the inlet and outlet ports
are capped because the test is not intended to expose the interior of
the TPRD. The TPRD is then exposed to the following fluids for 24 hours
each at 20 [deg]C:
Sulfuric acid at 19 percent in water to simulate battery
acid.
Ethanol at 10 percent in gasoline to simulate fueling
station fluids.
Methanol at 50 percent in water to simulate windshield-
washer fluid.
The TPRD is exposed to all of fluids separately in a sequence. The
fluids are replenished as needed for complete exposure throughout the
duration of the test. After exposure to each chemical fluid, the unit
is wiped off and rinsed with water to end any reactions that may be
occurring.
GTR No. 13 does not specify the method of exposure to these
chemical solutions. The method described in HPRD 1-2021 is to immerse
the test unit in each fluid.\94\ The duration of 24 hours is based on
industry practices. NHTSA seeks comment on the exposure method.
---------------------------------------------------------------------------
\94\ CSA/ANSI HPRD 1-2021, Thermally activated pressure relief
devices for compressed hydrogen vehicle fuel containers.
---------------------------------------------------------------------------
After the conclusion of the exposures, the TPRD unit is subjected
to the Leak Test, Benchtop Activation Test, and Flow Rate Test. These
tests, discussed below, verify the essential functions of the TPRD. In
addition to these subsequent tests, the TPRD must not show signs of
cracking, softening, or swelling. GTR No. 13 further specifies that
``cosmetic changes such as pitting or staining are not considered
failures.'' NHTSA seeks comment on including this specification, and
notes that pitting can be an aggressive form of corrosion which can
ultimately lead to component failure due to cracking at the pitting
site.
(6) Stress Corrosion Cracking Test
The purpose of the stress corrosion cracking test is to ensure that
the TPRD can resist stress corrosion cracking. Stress corrosion
cracking is the growth of crack formation in a corrosive environment.
It can lead to unexpected and sudden failure of normally ductile metal
alloys subjected to a tensile stress, especially at elevated
temperature. In particular, TPRDs containing copper-based alloys can be
susceptible to stress corrosion cracking in the presence of aqueous
ammonia. This is a significant risk because ammonia can be found in the
natural and vehicle environment.
The TPRD test unit is degreased to remove any protective grease
that may be present. The unit is then exposed for ten days to a moist
ammonia-air mixture maintained in a glass chamber. Under GTR No. 13,
the moist ammonia-air mixture is achieved using an ammonia-water
mixture with specific gravity of 0.94. Specific gravity is affected by
temperature and, therefore, is an inconvenient metric for concentration
specification because concentrations will need to be adjusted for
different temperatures. NHTSA seeks comment on a more direct metric for
ammonia
[[Page 27532]]
concentration specification, such as 20 weight percent ammonium
hydroxide in water.
The chamber is maintained at atmospheric pressure and 35 [deg]C.
This simulates a slightly elevated temperature. In GTR No. 13, the only
requirement to pass the stress corrosion cracking test is that the
components must not exhibit cracking or delaminating due to this test.
NHTSA seeks comment on this performance requirement and whether there
are alternative requirements for this test beyond basic visual
inspection, such as subjecting the TPRD to the leak test.
(7) Drop and Vibration Test
The purpose of the drop and vibration test is to evaluate the
TPRD's ability to withstand drop and vibration. Dropping a TPRD could
occur during installation, and vibration is likely to occur during on-
road service. A TPRD may be dropped in any one of six different
orientations covering the opposing directions of three orthogonal axes:
vertical, lateral and longitudinal. After the drop, the TPRD unit is
examined for damage that would prevent its installation in a test
fixture for vibration according to the manufacturer's instructions. If
damage is present that would prevent installation, the TPRD is
discarded, and it is not considered a test failure. Damage that would
prevent its installation is acceptable because the TPRD could never
enter service with this type of damage.
A TPRD that is not discarded after the drop test proceeds to the
vibration test. In addition, one new undamaged TPRD that was not
dropped is also subjected to the vibration test. The units are vibrated
for 30 minutes along each of the three orthogonal axes (vertical,
lateral, and longitudinal). The units are vibrated at a resonant
frequency which is determined by using an acceleration of 1.5 g and
sweeping through a sinusoidal frequency range of 10 to 500 Hz with a
sweep time of 10 minutes. According to GTR No. 13, the resonance
frequency is identified by a ``pronounced'' increase in vibration
amplitude. However, if the resonance frequency is not found, the test
is conducted at 40 Hz. Specifying a pronounced increase in vibration
amplitude could be partially subjective. NHTSA seeks comment on a more
objective criteria for establishing resonance, such as a frequency
where the amplitude of the response of the test article is at least
twice the input energy as measured by response accelerometers.
Furthermore, the acceleration level was not defined in GTR No. 13 for
the resonant dwells. NHTSA seeks comment on an appropriate acceleration
level for the resonant dwells.
After vibration, the TPRD units are subjected to the Leak Test,
Benchtop Activation Test, and Flow Rate Test. These tests, discussed
below, verify the essential functions of the TPRD.
(8) Leak Test
The leak test evaluates the TPRD's basic ability to contain
hydrogen at ambient and extreme temperature conditions. In particular,
the leak test is used after other tests to verify the TPRD's integrity
after undergoing the stresses from previous tests. Each TPRD under test
is conditioned for one hour by immersion in a temperature-controlled
liquid at ambient temperature, high temperature, and low temperature.
These test temperatures and corresponding test pressures are as
follows:
Ambient temperature: 5 [deg]C to 35 [deg]C, test at 2 MPa and
125 percent NWP
High temperature: 85 [deg]C, test at 2 MPa and 125 percent NWP
Low temperature: -40 [deg]C, test at 2 MPa and 100 percent NWP
The above temperatures are selected for the same reasons discussed
above for the test for performance durability. At the ambient and high
temperature tests, the TPRD is evaluated for leaks at 2 MPa and 125
percent NWP. The test pressure of 125 percent NWP represents the peak
pressure that typically occurs during fueling. For the low temperature
test, however, the maximum pressure is reduced to 100 percent NWP
because maximum fueling pressure is lower in extremely cold
environments. NHTSA seeks comment on the need to perform the leak test
at 2 MPa in addition to the higher pressures.
After the required pre-conditioning period, the evaluation for leak
involves observing the pressurized valve for hydrogen bubbles while
immersed in the temperature-controlled fluid. If hydrogen bubbles are
observed, the leak rate is measured by any method available to the test
lab. The total leak rate must be less than 10 NmL/h, which represents
an extremely low leak rate. NHTSA seeks comment on the leak rate
requirement of 10 NmL/hour. This leak rate of 10 NmL/hour is much lower
than the minimum hydrogen flow rate of 3.6 NmL/min necessary for
initiating a flame.\95\ NHTSA seeks comment on objective methods for
measuring the leak rate.
---------------------------------------------------------------------------
\95\ SAE Technical report 2008-01-0726. Flame Quenching Limits
of Hydrogen Leaks. The paper finds that the lowest possible
flammable flow is about 0.005 mg/s (3.6 NmL/min).
---------------------------------------------------------------------------
(9) Benchtop Activation Test
The purpose of the benchtop activation test is to demonstrate that
the TPRD will activate as intended when exposed to high temperature. As
with the leak test, the benchtop activation test is applied after other
tests to ensure the TPRD retains its basic functions after other
stresses have been applied.
The test setup consists of either an oven or a chimney which is
capable of controlling air temperature and flow to achieve 600 [deg]C
in the air surrounding the test sample. This provides a sufficiently
high air temperature to activate TPRDs. TPRD units are pressurized to
25 percent NWP or 2 MPa, whichever is less. This provides sufficient
pressure for activation.
Three new TRPD units are tested to establish a baseline activation
time, which is the average of the activation time of the three new
TPRDs. TPRD units used in the pressure cycling test, accelerated life
test, temperature cycling test, salt corrosion resistance test, vehicle
environment test, and drop and vibration test are also tested in the
benchtop activation test and these TPRDs must activate within 2 minutes
of the average activation time established from the tests with the new
units.
GTR No. 13 does not provide any information on how to proceed in
the event that a TPRD does not activate at all during the benchtop
activation test. A TPRD that does not activate when inserted into the
oven or chimney is not functioning as intended and therefore presents a
safety risk. As a result, NHTSA is proposing that if a TPRD does not
activate within 120 minutes from the time of insertion into the oven or
chimney, the TPRD is considered to have failed the test. The time limit
of 120 minutes is selected based on the maximum possible duration of
the CHSS fire test. NHTSA seeks comment on this requirement.
(10) Flow Rate Test
After benchtop activation, the flow rate test evaluates the TPRD
for flow capacity to ensure that the flow rate of a TPRD exposed to the
various environmental conditions during prior testing is similar to
that of a new TPRD. This test can be performed with hydrogen, air, or
any other inert gas because the test simply evaluates flow rate through
the TPRD. Flow rate through the TPRD is measured with the inlet
pressurized to 2 MPa and the outlet unpressurized. This pressure
difference generates flow through the
[[Page 27533]]
TPRD. The lowest measured flow rate must be no less than 90 percent of
a baseline flow rate established as the measured flow rate of a new
TPRD. This ensures low variation in flow rates and that all TPRDs
tested are free from blockages.
The number of significant figures used in the measurement of flow
rate can impact the test result. For example, a test flow rate of 1.7
flow units compared against a baseline flow rate of 2.0 flow units does
not meet the requirement. However, in this case, if flow rate were
measured using only one significant figure, the two flow rates would be
identical (2 flow units). As a result, NHTSA proposes requiring that
the flow rate be measured in units of kilograms per minute with a
precision of at least 2 significant digits. NHTSA seeks comment on this
proposed requirement.
(11) Atmospheric Exposure Test
GTR No. 13 includes an atmospheric exposure test to ensure that
non-metallic components which are exposed to the atmosphere and provide
a fuel-containing seal have sufficient resistance to oxygen. This is
because oxygen can degrade non-metallic components. The oxygen exposure
of 96 hours at 70 [deg]C at 2 MPa, is based on industry
standards.96, 97 The requirement to pass this test is that
the component not crack nor show visible evidence of deterioration.
---------------------------------------------------------------------------
\96\ ASTM D572-04(2019) Standard Test Method for Rubber--
Deterioration by Heat and Oxygen. https://www.astm.org/d0572-04r19.html.
\97\ ISO 188:2011 Rubber, vulcanized or thermoplastic--
Accelerated ageing and heat resistance tests. https://www.iso.org/standard/57738.html.
---------------------------------------------------------------------------
However, NHTSA is concerned that this test is not objectively
enforceable because the requirement involves a subjective determination
of evidence of deterioration. Furthermore, the test would require NHTSA
to determine which components are non-metallic, exposed to the
atmosphere, and provide a fuel-containing seal. As a result, this test
has not been included in FMVSS No. 308. NHTSA seeks comment on not
including the atmospheric exposure test.
b. Check Valves and Shut-Off Valves
Failure of a check valve or shut-off valve to properly contain
pressure within the CHSS can lead to a severe hydrogen leak.
Accordingly, check valves and shut-off valves must demonstrate their
operability and durability in service by completing the applicable
tests for performance durability of closure devices. This is a series
of performance tests applicable to check valves and shut-off valves
with requirements described below.
(1) Hydrostatic Strength Test
Since the check valve and the shut-off valve ensure containment of
high pressure hydrogen, the hydrostatic strength test is conducted to
ensure the valves are able to withstand extreme pressure of up to 250
percent NWP. Additionally, the test also ensures that the burst
pressure of the valves exposed to various environmental conditions
during prior testing is not degraded beyond 80 percent of a new
unexposed valve's burst pressure.
One new unit is tested to establish a baseline failure pressure,
which must be at least 250 percent NWP, and other units are tested as
specified in other sections, after being subjected to other tests. All
outlet openings are plugged, and valve seats or internal blocks are
placed in the open position. This allows the test pressure to be
distributed throughout the valve. The strength test is performed at 20
[deg]C with a hydrostatic pressure of 250 percent NWP applied at the
inlet. This high pressure simulates an extreme over-pressurization and
is held for three minutes.
From 250 percent NWP, the hydrostatic pressure is increased at a
rate of less than or equal to 1.4 MPa/second to avoid failure due to
rapid pressurization. The pressure continues to increase until the
component fails. The failure pressure of previously tested units should
be no less than 80 percent of the failure pressure of the baseline unit
unless the hydrostatic pressure exceeds 400 percent NWP.
In the event of a leak, it may become impossible for the test
laboratory to increase pressure on the valve. This occurs when any
increase in applied pressure is offset by leakage flow, thereby
negating the pressure increase. If this occurs, it is not possible to
complete testing. To address this issue, NHTSA is proposing that valves
shall not leak during the hydrostatic strength test, and that a leak
would constitute a test failure. NHTSA seeks comment on the requirement
that valves not leak during the hydrostatic strength test.
(2) Leak Test
The leak test evaluates the valve's basic ability to contain
hydrogen at ambient and extreme temperature conditions. In particular,
the leak test is used after other tests to verify the valve's integrity
after undergoing the stresses from previous tests. Each valve under
test is conditioned for one hour by immersion in a temperature-
controlled liquid at ambient temperature, high temperature, and low
temperature. These test temperatures and corresponding test pressures
are as follows:
Ambient temperature: 5 [deg]C to 35 [deg]C, test at 2 MPa and
125 percent NWP
High temperature: 85 [deg]C, test at 2 MPa and 125 percent NWP
Low temperature: -40 [deg]C, test at 2 MPa and 100 percent NWP
These temperatures and pressures are selected for the same reasons
described above for the TPRD leak test. After the required pre-
conditioning period, the evaluation for leak involves observing the
pressurized valve for hydrogen bubbles while immersed in the
temperature-controlled fluid. If hydrogen bubbles are observed, the
leak rate is measured by any method available to the test lab. Similar
to the TPRD leak test, the total leak rate must be less than 10 NmL/h.
For the same reasons discussed above for the TPRD leak test, NHTSA
seeks comment on the leak rate requirement of 10 NmL/h and seeks
comment on objective methods for measuring the leak rate.
(3) Extreme Temperature Pressure Cycling Test
Similar to the extreme temperatures applied to containers and CHSS,
the shut-off valve and the check valve must be able to withstand
extreme temperatures while in service. The extreme temperature pressure
cycling test simulates extreme temperature conditions that may lead to
gas release failures when combined with pressure cycling.
Check valves and shut-off valves may also be subject to ``chatter''
which is an excess of vibration that causes the valves to open and
close quickly and repeatedly. This causes a clicking and rattling noise
that is referred to as chatter. Valves can develop chatter when they
are not able to handle the pressure applied or are improperly sized.
Chatter of a valve can cause excessive wear of the valve mechanism that
can cause failure of the valve over time. Therefore, this test
evaluates the check valve and shut-off valve for chatter after the
extreme temperature pressure cycling.
The total number of operational cycles is 15,000 for the check
valve, consistent with the 15,000 cycles used for the TPRD above. The
total number of operational cycles is 50,000 for the shut-off valve.
The higher 50,000 cycles for the shut-off valve reflects the multiple
pressure pulses the shut-off valve experiences as it opens and closes
repeatedly during service. In contrast, the check valve only
experiences a
[[Page 27534]]
pressure pulse during fueling. NHTSA seeks comment on the number of
pressure cycles for check valves and shut-off valves.
Pressure cycling is conducted at different environmental
temperatures and pressures:
Ambient: Between 5.0 [deg]C and 35.0 [deg]C, 100 percent NWP
High: 85 [deg]C, 125 percent NWP
Low: -40 [deg]C, 80 percent NWP
For a check valve, the pressure is applied in six incremental
pulses to the valve inlet with the outlet closed. The pressure is then
vented from the inlet, with outlet side pressure reduced to below 60
percent NWP prior to the next cycle. This simulates the fueling
process. The valve is held at the corresponding temperature for the
duration of the cycling at each condition.
For a shut-off valve, the pressure is applied through the inlet
port. The shut-off valve is then energized to open the valve and the
pressure is reduced to any pressure less than 50 percent of the
specified pressure range. The shut-off valve is then de-energized to
close the valve prior to the next cycle. This simulates operation of
the shut-off valve during service. The valve is held at the
corresponding temperature for the duration of the cycling at each
condition.
After cycling, each valve is subjected to 24 hours of ``chatter
flow'' to simulate the chatter condition described above. Chatter flow
means the application of a flow rate of gas through the valve that
results in chatter as described above. NHTSA is concerned, however,
that the application of chatter flow could be partially subjective.
NHTSA seeks comment on the following aspects of the chatter flow test:
Appropriate methodology or a procedure for inducing
chatter flow.
Appropriate instrumentation and criteria to measure and
quantify chatter flow such as a decibel meter and minimum sound
pressure level.
How to proceed in cases where no chatter occurs.
The specific safety risks that are addressed by the
chatter flow test.
The possibility of not including the chatter flow test.
In the case of shut-off valves, GTR No. 13 specifies the chatter
flow test is required only in the case of a shut-off valve which
functions as a check valve during fueling and that the flow rate used
to induce chatter should be within the normal operating conditions of
the valve. However, NHTSA has no way of determining whether a shut-off
valve is functioning as a check valve during fueling or the normal
operating conditions of the valve. As a result, NHTSA is proposing that
the chatter flow test will apply to all shut-off valves and will not
specify flow rate limitations for the chatter flow test. NHTSA seeks
comment on this decision.
After the completion of the chatter flow test, the valve must
comply with the leak test and the hydrostatic strength test to verify
it retains its basic ability to contain hydrogen and resist burst due
to over-pressurization.
(4) Salt Corrosion Resistance Test
The salt corrosion resistance test is conducted in the same manner
and for the same reasons discussed above for TPRDs. At the completion
of the salt corrosion resistance test, the tested valve must comply
with the ambient temperature leak test and the hydrostatic strength
test to verify it retains its basic ability to contain hydrogen and
resist burst due to over-pressurization.
(5) Vehicle Environment Test
The vehicle environment test is conducted in the same manner and
for the same reasons discussed above for TPRDs. At the completion of
the vehicle environment test, the tested valve shall comply with the
leak test and the hydrostatic strength test to verify it retains its
basic ability to contain hydrogen and resist burst due to over-
pressurization. In addition to these subsequent tests, the valve shall
not show signs of cracking, softening, or swelling.
(6) Atmospheric Exposure Test
GTR No. 13 includes an atmospheric exposure test for check valves
and shut-off valves identical to the atmospheric exposure test for
TPRDs. However, this test has not been included for check valves and
shut-off valves for the same reasons it was not included for TPRDs.
NHTSA seeks comment on not including the atmospheric exposure test for
check valves and shut-off valves.
(7) Electrical Tests
The electrical tests apply to the shut-off valve only. The
electrical tests evaluate the shut-off valve for:
Leakage, unintentional valve opening, fire, and/or melting
after exposure to an abnormal voltage.
Failure of the electrical insulation between the power
conductor and casing when the valve is exposed to a high voltage.
The exposure to abnormal voltage is conducted by applying twice the
valve's rated voltage or 60 V, whichever is less to the valve for at
least one minute. After the test, the valve is subject to the leak test
and leak requirements. The test for electrical insulation is conducted
by applying 1000 V between the power conductor and the component casing
for at least two seconds, consistent with the industry standards NGV
3.1-2012 and HGV 3.1-2022.98 99 The isolation resistance
between the valve and the casing must be 240 k[Omega] or more. This
represents a high level of resistance to prevent the valve casing from
being energized in the event the power conductor short circuits within
the valve.\100\
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\98\ NGV 3.1-2012. Fuel system components for compressed natural
gas powered vehicles. https://webstore.ansi.org/standards/csa/ansingv2012csa12.
\99\ HGV 3.1-2022. Fuel system components for compressed
hydrogen gas powered vehicles.
\100\ Id.
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Some valves may have requirements specified by their manufacturers
for peak and hold pulse width modulation duty cycle. NHTSA seeks
comment on whether and how to adjust the proposed test procedure to
account for a manufacturer's specified peak and hold pulse width
modulation duty cycle requirements.
(8) Vibration Test
The vibration test evaluates a valve's resistance to vibration. The
valve is pressurized to 100 percent NWP and exposed to vibration for 30
minutes along each of the three orthogonal axes (vertical, lateral, and
longitudinal). After the test, the valve is inspected for visual
exterior damage and required to comply with the ambient temperature
leak test. Vibration is conducted along the three orthogonal axes to
cover different possible mounting positions within a vehicle.\101\
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\101\ Id.
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The vibration frequencies used for the test are determined by
frequency sweeps along each axis in the range of 10 Hz to 500 Hz. The
most severe resonant frequency in each axis is selected for the test.
Resonant frequencies are determined as those frequencies of the
vibration table that result in considerably different acceleration
measurements from an accelerometer mounted to the acceleration table
and that mounted on the component under test. If a most severe resonant
frequency is determined, the component undergoes vibration at that
frequency for 30-minutes. If no resonant frequency is found, then 40 Hz
is selected for that axis. The vibration acceleration is 1.5 g, which
represents vibration acceleration within a typical vehicle.
This test is conducted with the valve pressurized to 100 percent
NWP to
[[Page 27535]]
simulate vibrations occurring while the valve is in service. After
vibration, the valve shall comply with the leak test and the
hydrostatic strength test to verify it retains its basic ability to
contain hydrogen and resist burst due to over-pressurization.
GTR No. 13 also contains a requirement that ``each sample shall not
show visible exterior damage that indicates that the performance of the
part is compromised.'' Showing signs of damage is a subjective measure
and lacks the objectivity needed per the Motor Vehicle Safety Act.
Therefore, this language has been removed.
(9) Stress Corrosion Cracking Test
The stress corrosion cracking test is conducted in the same manner
and for the same reasons discussed above for TPRDs.
9. Labeling Requirements
Labels on a container are important for informing the consumer that
the container is intended for hydrogen fuel, information on the nominal
working pressure of the container, and information on when the
container should be removed from service. The information on the
container labels would also facilitate the agency's enforcement efforts
by providing a ready means of identifying the container and its
manufacturer, and by providing the information needed for conducting
compliance tests. NHTSA tentatively concludes that the container
label(s) include the following information:
Manufacturer, serial number, date of manufacture
The statement ``Compressed Hydrogen Only.''
The container's NWP in MPa and pounds per square inch (psi).
Date when the system should be removed from service
BPO in MPa and psi.
B. FMVSS No. 307, ``Fuel System Integrity of Hydrogen Vehicles''
FMVSS No. 307 would set requirements for the vehicle fuel system to
mitigate hazards associated with hydrogen leakage and discharge from
the fuel system, as well as requirements to ensure hydrogen leakage,
hydrogen concentration in enclosed spaces of the vehicle, and hydrogen
container displacement are within safe limits post-crash. A hydrogen
fuel system includes the fueling receptacle, CHSS, fuel cell system or
internal combustion engine, exhaust systems, and the fuel lines that
connect these systems. Table-10 lists the requirements for the hydrogen
fuel system to be incorporated in FMVSS No. 307, which includes
separate sections for normal vehicle operations and post-crash
requirements. The fuel system integrity requirements for normal vehicle
operations would apply to all hydrogen-fueled vehicles, while the post-
crash fuel system integrity requirements only apply to light vehicles.
NHTSA seeks comment on the application of FMVSS No. 307 to all
vehicles, including heavy vehicles (vehicles with a GVWR greater than
4,536 kg (10,000 pounds).\102\
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\102\ The proposed FMVSS No. 307 would apply, in general, to all
hydrogen vehicles regardless of GVWR. However, not all vehicles
would be subject to crash testing under FMVSS No. 307. As described
below, passenger cars, multipurpose passenger vehicles, trucks and
buses with a GVWR of less than or equal to 4,536 kg would be subject
to barrier crash testing. School buses with a GVWR greater than
4,536 kg would also be subject a barrier crash test. Heavy vehicles
other than school buses with a GVWR greater than 4,536 kg would not
be subject to crash testing under the proposed standard.
Table 10--Performance Test Requirements for Hydrogen Vehicle Fuel System
Integrity
------------------------------------------------------------------------
-------------------------------------------------------------------------
Performance test requirements for hydrogen vehicle fuel system
Fuel system integrity requirements for light and heavy vehicles during
normal vehicle operations.
Fueling receptacle requirements.
Over-pressure protection for the low-pressure system.
Hydrogen discharge systems.
Protection against flammable conditions.
Fuel system leakage requirements.
Tell-tale warning to driver.
Post-crash fuel system integrity requirements for light vehicles.
Fuel leakage limit.
Concentration limit in enclosed spaces.
Container displacement.
------------------------------------------------------------------------
1. Fuel System Integrity During Normal Vehicle Operations
The first half of the proposed FMVSS No. 307 would adopt GTR No.
13's protections during the normal operation of the vehicle. The
proposed requirements in this section apply to all hydrogen fuel
vehicles regardless of GVWR.
a. Fueling Receptacles
This proposal includes five performance requirements for the
hydrogen fueling receptacle. These requirements ensure safe use and
proper function of the receptacle. If hydrogen is not properly
contained by the fueling receptacle, hydrogen may escape into the
surrounding environment where it may accumulate and become ignited,
leading to an explosion or fire.
The first requirement for the fueling receptacle is to prevent
reverse flow to the atmosphere. This requirement is intended to prevent
hydrogen leakage out of the fueling receptacle.
The second requirement is for a label with the statement,
``Compressed Hydrogen Only'' as well as the statement ``Service
pressure __ MPa (__ psig).'' Including this information on a label near
the fueling receptacle is intended to prevent incorrect fueling.
Incorrect fueling with a fuel other than hydrogen or with a hydrogen
pressure greater than the vehicle NWP could damage the fuel system. The
label must also contain the statement, ``See instructions on fuel
container(s) for inspection and service life.''
The third requirement is for positive locking that prevents the
disconnection of the fueling hose during fueling. This requirement is
intended to prevent the fueling nozzle from being prematurely removed
during fueling, which could result in hydrogen leakage.
The fourth requirement is for protection against ingress of dirt
and water to protect the fueling receptacle from contamination that
could lead to degradation of the fuel system over time. A degraded fuel
system is a safety risk because it could lead to a failure to contain
hydrogen.
The fifth requirement is to prevent the receptacle from being
mounted in a location that would be highly
[[Page 27536]]
susceptible to crash deformations in order to prevent degradation in
the event of a crash. The receptacle is also prevented from being
mounted in the enclosed or semi-enclosed spaces of the vehicle because
these areas can accumulate hydrogen.\103\
---------------------------------------------------------------------------
\103\ Enclosed or semi-enclosed spaces means the volumes within
the vehicle, external to the hydrogen fuel system (fueling
receptacle, CHSS, fuel cell system or internal combustion engine,
fuel lines, and exhaust systems) such as the passenger compartment,
luggage compartment, and space under the hood.
---------------------------------------------------------------------------
The assessment for all five receptacle requirements is by visual
inspection. NHTSA seeks comment on these proposed requirements for the
fueling receptacle and on the objectivity of assessment by visual
inspection.
b. Over-Pressure Protection for Low-Pressure Systems
Hydrogen is stored on hydrogen vehicles at high pressures. However,
fuel cells and hydrogen combustion engines require lower pressures to
operate, and higher pressures have the potential to damage their
internal mechanisms. As a result, downstream fuel lines are designed
for much lower pressures than the CHSS. Pressure regulators are used
between the CHSS and the downstream lines to lower the pressure
delivered downstream.
NHTSA is proposing to adopt GTR No. 13's requirement of over-
pressure protection for low-pressure systems. Accordingly, the agency
proposes requiring countermeasures to prevent failure of downstream
components in the event a pressure regulator fails to properly reduce
the fuel pressure from the much higher pressure in the CHSS. The
activation pressure of the overpressure protection device would be
lower than or equal to the maximum allowable working pressure for the
appropriate section of the hydrogen system as determined by the
manufacturer. NHTSA seeks comment on the requirement for an
overpressure protection device in the fuel system and how to test the
performance of such a device.
c. Hydrogen Discharge Systems
TPRDs are designed to discharge the hydrogen stored in the CHSS to
mitigate the risk of a rupture when the temperature surrounding the
CHSS reaches a dangerous temperature. However, venting a flammable fuel
source during an emergency can create its own potential hazard if
handled improperly. For those reasons, we believe there is a safety
need to propose standards for the hydrogen discharge system.
The first proposed requirement is that the TPRD vent line be
protected from ingress of dirt or water to prevent contamination that
could degrade or compromise the TPRD or the TPRD discharge stream. This
requirement protects the TPRD from degradation due to the ingress of
dirt and water. A degraded TPRD that fails to activate during a fire
could lead to a container burst. Alternatively, if the vent line itself
became clogged by dirt and water, it could fail to properly vent the
hydrogen in the event of a TPRD activation.
Next, we are proposing several requirements from GTR No. 13 related
to the TPRD vent discharge direction. The primary purpose of these
requirements is to prevent additional safety hazards due to hydrogen
discharge from the TPRD that could compromise other vehicle components
and/or inhibit the ability of passengers to safely exit the vehicle.
Accordingly, we propose that the TPRD discharge must not be directed
towards nor impinge upon:
1. Any enclosed or semi-enclosed spaces where hydrogen could
unintentionally accumulate, such as the trunk, passenger compartment,
or engine compartment.
2. The vehicle wheel housing.
3. Hydrogen gas containers--if the hydrogen being released from the
TPRD becomes ignited, this would pose a burst risk.
4. Rechargeable electrical energy storage system (REESS) because if
the TPRD discharge became ignited, this could engulf the REESS and
start a battery fire.
5. Any emergency exit(s) or service door(s), because this would
create a hazard to persons exiting the vehicle.
In addition to these requirements from GTR No. 13, we believe an
additional requirement is necessary to protect potential occupants
attempting to exit the vehicle or first responders approaching the
vehicle. We are proposing that hydrogen vented through the TPRD(s) be
directed upwards within 20[deg] of vertical relative to the level
surface or downwards within 45[deg] of vertical relative to the level
surface. This requirement would prevent the TPRD discharge from being
directed horizontally, which would create a hazard to persons exiting
the vehicle and/or to first responders approaching the vehicle. NHTSA
seeks comment on this additional requirement for TPRD discharge
direction, and on the proposed discharge angles.
NHTSA is proposing that the discharge direction from TPRDs and
other pressure relief devices is evaluated through visual inspection.
We seek comment on whether there is a more appropriate test.
d. Vehicle Exhaust System
NHTSA is proposing to adopt GTR No. 13's vehicle exhaust system
requirements. Similar to the previous requirements, elevated
concentrations of hydrogen in the exhaust increases the risk of a fire.
The GTR requires that the hydrogen concentration never exceed eight
percent, and not exceed four percent for any three second moving
average value of the hydrogen concentration.
At an ambient temperature of 20 [deg]C, 4 percent by volume of
hydrogen in air can ignite and propagate in the direction opposite
gravity. However, the propagation is extremely weak and not sustained.
At approximately eight percent hydrogen, ignition of hydrogen/air
mixture can propagate in any direction regardless of ignition source
location. Furthermore, tests demonstrated that as the hydrogen
concentration approaches eight percent, exhaust becomes intermittently
flammable, igniting in the presence of an ignition source, but
extinguishing when the ignition source is removed.\104\ As a result,
fire occurring at eight percent hydrogen concentration is small and
fairly easy to extinguish. Therefore, limiting the hydrogen content of
any instantaneous peak to eight percent limits the hazard to near the
exhaust discharge point even if an ignition source is present.
---------------------------------------------------------------------------
\104\ SAE Technical Report 2007-01-437. Development of Safety
Criteria for Potentially Flammable Discharges from Hydrogen Fuel
Cell Vehicles, Local Discharge Flammability--Flowing Exhaust.
https://www.sae.org/publications/technical-papers/content/2007-01-0437/.
---------------------------------------------------------------------------
NHTSA is proposing adopting the test requirement outlined in GTR
No. 13. The test procedure would be conducted after the vehicle has
been set to the ``on'' or ``run'' position for at least five minutes
prior to testing. A hydrogen measuring device is placed in the center
line of the exhaust within 100 mm from the external discharge point.
The fuel system would undergo a shutdown, start-up, and idle operation
to stimulate normal operating conditions. The measurement device used
should have a response time of less than 0.3 seconds to ensure an
accurate three second moving average calculation. Response times higher
than 0.3 seconds could result in inaccurate data collection because the
sensor may not have time to register the true concentration levels
before recording each data point.
The time period of three seconds for the rolling average ensures
that the
[[Page 27537]]
space around the vehicle remains non-hazardous in the case of an idling
vehicle in a closed garage. This is conservatively determined by
assuming that a standard size vehicle purges the equivalent of a 250 kW
(340 HP) fuel cell system. The power system output of a Toyota Mirai is
182 HP. The time is then calculated for a nominal space occupied by a
standard passenger vehicle (4.6 meters x 2.6 meters x 2.6 meters) to
build up to 25 percent of the LFL, or one percent by volume in air. The
time limit for this rolling-average situation is determined to be three
seconds.\105\
---------------------------------------------------------------------------
\105\ SAE 2578_201408. Recommended Practice for General Fuel
Cell Vehicle Safety. Appendix C3. https://www.sae.org/standards/content/j2578_201408/.
---------------------------------------------------------------------------
e. Fuel System Leakage
GTR No. 13 includes fuel system leakage requirements specifying no
leakage from the fuel lines. A flammable or explosive condition can
arise if hydrogen leaks from the fuel lines. However, the safety risk
of a leak applies to the entire fuel system, not only to the fuel
lines. As a result, NHTSA is proposing that the fuel system leakage
requirement for no leakage apply to the entire hydrogen fuel system
downstream of the shut-off valve, which includes the fuel lines and the
fuel cell system. NHTSA is further proposing to define fuel lines to
include all piping, tubing, joints, and any components such as flow
controllers, valves, heat exchangers, and pressure regulators. From a
safety standpoint, there is no difference between a leak coming from
fuel line piping, and a leak coming from a valve, pressure regulator,
or the fuel cell system itself. While NHTSA is proposing a strict no
leakage standard, we are seeking comment on whether there is a safe
level of hydrogen that may leak, and if so, what would be an objective
leakage limit and how to accurately quantify hydrogen leakage from the
fuel system.
NHTSA is proposing to test this requirement using either a gas leak
detector or leak detecting liquid (bubble test).\106\ NHTSA seeks
comment if one of these tests is preferrable. NHTSA is also proposing
that the test would be conducted with the fuel system at NWP after
having been in the ``on'' or ``run'' position for at least five
minutes. We believe these conditions produce an elevated likelihood of
leakage. We seek comment on whether alternative conditions would better
simulate realistic scenarios when downstream lines are more likely to
leak.
---------------------------------------------------------------------------
\106\ As discussed above, a bubble leak test is not an objective
method for quantifying a leakage rate during the extreme temperature
static gas pressure leak/permeation test. However, NHTSA is
proposing a strict no leakage requirement for the test for fuel line
leakage. This requirement does not require that the leak be
quantified, and therefore, a bubble test may be used to evaluate
this requirement. Any observed bubble would indicate leakage and
constitute a failure of the test for fuel line leakage.
---------------------------------------------------------------------------
f. Protection Against Flammable Conditions
The final component of GTR No. 13's safety measures for the fuel
system during normal use is ensuring that the enclosed and semi-
enclosed spaces of the vehicle do not accumulate potentially dangerous
concentrations of hydrogen.
The agency proposes requiring a visual warning within 10 seconds in
the event that the hydrogen concentration in an enclosed or semi-
enclosed space exceeds 3.0 percent (75 percent of the LFL). This
concentration limit for the warning is selected because while 3.0
percent hydrogen is below the LFL, and is therefore inflammable,
accumulation of hydrogen to 3.0 percent indicates the presence of a
leak and the potential for continued hydrogen accumulation beyond the
LFL. Additionally, in accordance with GTR No. 13, we propose requiring
the shut-off valve to close within 10 seconds if at any point the
concentration in an enclosed or semi-enclosed space exceeds 4.0 percent
(the LFL). Closure of the shut-off valve isolates the CHSS and ensures
hydrogen cannot accumulate beyond the LFL. The details of the warning
itself are discussed below in the following section.
GTR No. 13 provides two options for evaluating this requirement.
The first option is to use a remote-controlled release of hydrogen to
simulate a leak, along with laboratory-installed hydrogen concentration
detectors in the enclosed or semi-enclosed spaces. The laboratory-
installed hydrogen concentration detectors are used to verify that the
required warning and shut-off valve closure occur at the appropriate
hydrogen concentrations in the enclosed or semi-enclosed spaces. GTR
No. 13 allows for the remote-controlled release of hydrogen to be drawn
from the vehicle's own CHSS. Therefore, by using this option, it is
possible for a vehicle to meet the requirements without a built-in
hydrogen concentration detector. This is accomplished by the vehicle
monitoring hydrogen outflow from its CHSS. The vehicle can then trigger
the required warning and shut-off valve closure if significant hydrogen
outflow from the CHSS is detected that is not accounted for by fuel
cell hydrogen consumption.
The second option for evaluating the requirement is to use an
induction hose and a cover to apply hydrogen test gas directly to the
vehicle's built-in hydrogen concentration detector(s) within the
enclosed or semi-enclosed spaces. Test gas with a hydrogen
concentration of 3.0 to 4.0 percent is used to verify the warning, and
test gas with a hydrogen concentration of 4.0 to 6.0 percent is used to
verify the closure of the shut-off valve. The warning and shut-off
valve closure must occur within 10 seconds of applying the respective
test gas to the detector. The warning is verified by visual inspection,
and the shut-off valve closure can be verified by monitoring the
electric power to the shut-off valve or by the sound of the shut-off
valve activation.
This second option indirectly requires the presence of at least one
hydrogen concentration detector in the enclosed or semi-enclosed spaces
that can detect the hydrogen test gas and trigger the warning and shut-
off valve closure at appropriate hydrogen concentration levels. NHTSA
is proposing this second option as the only test method in FMVSS No.
307, which would thereby require each vehicle to have at least one
built-in hydrogen concentration detector. NHTSA seeks comment on
requiring built-in hydrogen concentration detectors and seeks comment
on the reliability of the required warning and shut-off valve closure
for vehicles that do not have built-in hydrogen concentration
detectors.
In addition to the above requirement regarding a warning and shut-
off valve closure, GTR No. 13 includes a requirement that any failure
downstream of the main hydrogen shut off valve shall not result in any
level of hydrogen concentration in the passenger compartment. This
requirement is evaluated by applying a remote-controlled release of
hydrogen simulating a leak in the fuel system, along with laboratory-
installed hydrogen concertation detectors in the passenger compartment.
After remote release of hydrogen, GTR No. 13 requires that the hydrogen
concentration in the passenger compartment not exceed 1.0 percent. The
number, location, and flow capacity of the release points for the
remote-controlled release of hydrogen are defined by the vehicle
manufacturer.
A concentration of 1.0 percent hydrogen is inflammable at only 25
percent of the LFL for hydrogen. NHTSA has determined there is no need
to apply such a stringent concentration limit in the passenger
compartment. NHTSA is instead proposing that the
[[Page 27538]]
remote-controlled release of hydrogen shall not result in a hydrogen
concentration exceeding 3.0 percent in the enclosed or semi-enclosed
spaces of the vehicle (including the passenger compartment). NHTSA
believes that this is a more balanced requirement that ensures there is
no accumulation of hydrogen too near the LFL in any enclosed or semi-
enclosed spaces of the vehicle. NHTSA seeks comment on this requirement
and on specific test procedures for initiating a remote-controlled
release of hydrogen in a vehicle.
To evaluate this requirement, NHTSA proposes that a hydrogen
concentration detector be installed in any enclosed or semi-enclosed
space where hydrogen may accumulate from the simulated hydrogen
release. After the remote-controlled release of hydrogen, the hydrogen
concentration would be measured continuously using the laboratory-
installed hydrogen concertation detector. The test would be completed
five minutes after initiating the simulated leak or when the hydrogen
concentration does not change for three minutes, whichever is longer.
Five minutes is selected as the minimum time for monitoring the
hydrogen concentration because five minutes is generally considered a
sufficient time frame for vehicle occupants to evacuate in the event of
an emergency.
The test procedures in this section are intended to work together
to ensure safety. Primary protection is provided by ensuring that
hydrogen cannot accumulate as a result of a leak beyond a 3.0 percent
concentration in the enclosed or semi-enclosed spaces. This ensures
that there is no potential for ignition to occur due to hydrogen
leakage. The requirement for the visual warning and shut-off valve
closure serves as a secondary measure in preventing a flammable
condition from occurring in the event of a failure resulting in an
accumulation of hydrogen.
The proposed test procedures in this section would be conducted
without the influence of any wind. NHTSA seeks comment on providing
more specific wind protection requirements and seeks comment on
limiting the maximum wind velocity during testing to 2.24 meters/second
as in FMVSS No. 304.\107\
---------------------------------------------------------------------------
\107\ FMVSS No. 304, ``Compressed natural gas fuel container
integrity.'' https://www.ecfr.gov/current/title-49/subtitle-B/chapter-V/part-571/subpart-B/section-571.304.
---------------------------------------------------------------------------
g. Warning for Elevated Hydrogen Concentration
While the aim of the GTR and this proposal is to set safety
requirements that prevent hydrogen from leaking and causing hazardous
conditions, if hydrogen manages to accumulate to the LFL of 4.0
percent, there is a risk of a fire or explosion occurring. As discussed
above, NHTSA is proposing requiring a telltale \108\ warning when
hydrogen concentration exceeds 3.0 percent in the enclosed or semi-
enclosed spaces of the vehicle. Given the serious threat posed by
elevated hydrogen levels in the passenger compartment, NHTSA is
proposing the visual warning be red in color and remain illuminated
while the vehicle is in operation with hydrogen concentration levels
exceeding 3.0 percent in enclosed or semi-enclosed spaces of the
vehicle. The visual warning must be in clear view of the driver. For a
vehicle with automated driving systems and without manually-operated
driving controls, the visual warning must be in clear view of all the
front seat occupants. NHTSA seeks comment on whether the warning should
be in clear view of all occupants, including occupants in rear seating
positions, in vehicles with automated driving systems. NHTSA also seeks
comment on whether an auditory warning be required when hydrogen
concentration exceeds 3.0 percent in the enclosed or semi-enclosed
spaces of the vehicle.
---------------------------------------------------------------------------
\108\ A telltale is an optical signal that, when illuminated,
indicates the actuation of a device, a correct or improper
functioning or condition, or a failure to function.
---------------------------------------------------------------------------
NHTSA is also proposing that a telltale be activated if the
hydrogen warning system malfunctions, such as in the case of a circuit
disconnection, short circuit, sensor fault, or other system failure.
NHTSA proposes that when the telltale activates for these circumstances
that it illuminates as yellow to distinguish a malfunction of the
warning system from that of excess hydrogen concentration.
2. Post-Crash Fuel System Integrity
The second half of proposed FMVSS No. 307 are post-crash
requirements for the fuel system. After a vehicle crash, there is a
high risk of hydrogen escaping from the CHSS and other parts of the
vehicle fuel system due to structural damage. The primary safety
strategy applied in GTR No. 13 is to ensure the proper containment of
hydrogen in the container and the fuel system after a crash has
occurred.
In accordance with GTR No. 13, NHTSA is proposing that the post-
crash requirements only apply to passenger cars, multipurpose passenger
vehicles, trucks and buses with a GVWR less than or equal to 4,536 kg
(10,000 pounds) and to all school buses, that use hydrogen fuel for
propulsion power. NHTSA is not proposing that these post-crash
requirements apply to all heavy vehicles with a GVWR greater than 4,536
kg (10,000 pounds). We are tentatively making this decision because
there is not a comparable crash test for heavy vehicles to conduct the
tests necessary for compliance assessment. NHTSA seeks comment on
whether heavy vehicles should be subject to these proposed post-crash
requirements and if so, what crash tests should NHTSA conduct on
heavier vehicles.
During Phase I of GTR No. 13, the IWG decided not to attempt
creating a uniform crash test and instead provided the option to
Contracting Parties to determine the appropriate test based on their
existing standards. NHTSA is proposing to use the crash tests
equivalent to those applied to conventionally fueled vehicles in
accordance with FMVSS No. 301. For light vehicles with a GVWR under
4,536 kg, these crash tests include an 80 kilometers per hour (km/h)
(~50 miles per hour (mph)) impact of a rigid barrier into the rear of
the vehicle, a 48 km/h (~30 mph) frontal crash test into a rigid
barrier, and a 53 km/h (~33 mph) impact of a moving deformable barrier
into the side of the vehicle. For school buses with a GVWR greater than
or equal to 4,536 kg, the crash test is a moving contoured barrier
impact at 48 km/h. NHTSA has determined that it is appropriate to apply
equivalent crash tests to hydrogen vehicles as those for conventionally
fueled vehicles. NHTSA seeks comment on whether there are alternative
crash tests that should be used for the forthcoming proposed
regulations.
NHTSA is proposing that there be no fire during the test, and that
vehicles meet three additional post-crash requirements described by GTR
No. 13. These three requirements echo the same safety goals of the
first half of FMVSS No. 307. They are designed to prevent CHSS bursts,
the creation of additional hazards caused by hydrogen leakage, and to
protect occupants.
The first proposed requirement is based on FMVSS No. 301. FMVSS No.
301 S5.5 and S5.6 specifies that the total amount of allowable energy
loss for gasoline fuel from impact through the 60-minute interval after
motion has ceased is 72,590 kiloJoules (KJ). This total amount of
allowable energy loss
[[Page 27539]]
when applied to hydrogen and its energy density, equates to 606 grams
of hydrogen loss. From the total allowable hydrogen mass leakage of 606
g, the total allowable volumetric leakage, with a reference temperature
of 15 [deg]C, during 60-minute interval after impact can be calculated
as follows:
[GRAPHIC] [TIFF OMITTED] TP17AP24.014
where 2.0159 gram/mole is the molar weight of a hydrogen molecule and
22.41 liter/mole is the molar volume of hydrogen at standard
conditions, and the factor 288/273 adjusts the calculation for a
temperature of 15 [deg]C. Therefore, the allowable volumetric flow rate
of hydrogen after impact through the 60-minute interval after impact
has ceased is: 7107 NL/60 minutes = 118 NL/minute.\109\
---------------------------------------------------------------------------
\109\ For additional information, see the associated technical
document ``Post-crash hydrogen leakage limit for FMVSS No. 307.pdf''
in the docket of this NPRM. Reference: SAE 2578_201408. Recommended
Practice for General Fuel Cell Vehicle Safety. Appendix A.1.1.
---------------------------------------------------------------------------
The volumetric flow of hydrogen gas leakage from the CHSS must not
exceed an average of 118 normal liters per minute (NL/min) from the
time of vehicle impact through a time interval [Delta]t of at least 60-
minutes after impact. This leakage limit of 118 NL/min is equivalent to
a total allowable mass leakage of 606 grams of hydrogen gas in 60
minutes.
The volumetric leak rate of hydrogen post-crash is determined as a
function of the pressure in the container before and after the crash
test. The interval [Delta]t is at least 60 minutes after impact to
provide time for any leaks to reduce the CHSS pressure by an accurately
measurable amount. For a pressure drop to be measured accurately by a
sensor, the drop should be at least 5 percent of the pressure sensor's
full range. However, for a CHSS larger than about 400 liters, 60
minutes may be insufficient for a leak exceeding the leakage limit to
result in 5 percent of full range pressure drop. This is due to the
non-linear relationship between the density and pressure of hydrogen
and helium gas. Therefore, the variables of CHSS volume, sensor range,
and CHSS NWP need to be considered when determining the time interval
[Delta]t. GTR No. 13 provides an equation to increase [Delta]t as
necessary to ensure an accurate pressure drop measurement as described
in the following:
The time interval after impact, [Delta]t, shall be the greater of:
(1) 60 minutes; or
(2) [Delta]t = VCHSS x NWP/1000 x ((-0.027 x NWP + 4) x
Rs-0.21)-1.7 x Rs, where Rs =
Ps/NWP, Ps is the pressure range of the pressure
sensor (MPa), NWP is the Nominal Working Pressure (MPa), and
VCHSS is the volume of the CHSS (L).
Helium may be used in place of hydrogen during crash-testing, as a
safer alternative to hydrogen, with the corresponding calculation
modifications discussed below. Due to the differing physical properties
of hydrogen and helium gas, the allowable leakage limit for helium is
75 percent of the 118 NL/min allowed for hydrogen. This corresponds to
a helium leakage limit of 88.5 NL/min.
The second requirement ensures hydrogen does not accumulate in the
enclosed or semi-enclosed spaces which could present a post-crash
hazard. This hydrogen concentration limit is set to four percent by
volume (for helium, this corresponds to a concentration of three
percent by volume). This requirement is satisfied if the CHSS shut-off
valve(s) are confirmed to be closed within five seconds of the crash
and there is no hydrogen leakage from the CHSS. If the shut-off valve
has closed and the leakage from the CHSS is no more than 118 NL/min, it
is not likely for hydrogen to accumulate in enclosed or semi-enclosed
spaces.
For the purpose of measuring the hydrogen concentration, GTR No. 13
specifies that data from the sensors shall be collected at least every
five seconds and continue for a period of 60 minutes. GTR No. 13 also
discusses filtering of the data to provide smoothing of the data, but
is unclear about the exact data filtration method to be used. NHTSA
proposes using a three data point rolling average for filtering the
data steam. Since a data point will collected at least every five
seconds, this rolling average will be, at most, a 15-second rolling
average. NHTSA seeks comment on this proposed data filtration method.
The third requirement in GTR No. 13 that NHTSA is proposing is
requiring that the container(s) remains attached to the vehicle by at
least one component anchorage, bracket, or any structure that transfers
loads from the device to the vehicle structure. This ensures that a
container is not separated from the vehicle during a crash. Most
containers rely at least partially on the vehicle for protection and
shielding. As a result, the container cannot be allowed to separate
from the vehicle during a crash. This requirement is evaluated by
visual inspection of the container attachment points.
NHTSA will evaluate the presence of vehicle fire by visual
inspection for the duration of the test, which includes the time needed
to determine fuel leakage from the CHSS.
GTR No. 13 specifies that each contracting party maintain its
existing national crash tests (frontal, side, rear and rollover) for
post-crash evaluation. However, the crash tests specified in FMVSS No.
301 and post-crash requirements are only intended for light vehicles.
In GTR No. 13 Phase 1, the scope of the regulation was confined to
light vehicles under 4,536 kg (10,000 pounds). Since the scope of GTR
No. 13 was expanded under Phase 2 to cover heavy vehicles, the IWG
considered different alternative options to replace full vehicle crash
tests for heavy vehicles. However, none of these alternative options
for heavy vehicles were implemented into GTR No. 13 Phase 2.
Under Phase 2, the European Union proposed sled tests to replace
full-scale crash testing for light and heavy vehicles. The sled test
proposal involved applying several acceleration pulses to CHSS mounted
on a sled with attachment structures similar to those on a
corresponding hydrogen vehicle. The acceleration pulses of three
separate sled tests simulate a peak of 10 g acceleration in the forward
and rearward direction of travel, and 8 g in the direction
perpendicular to the direction of travel.
NHTSA questioned the safety need for this sled test during the IWG
discussions on the European Union proposal. The proposed sled test's
only performance requirement is for the CHSS to remain attached to the
vehicle by at least one anchorage point. In the U.S., there is no
corresponding sled test for CNG heavy vehicles, and NHTSA is not aware
of any safety issues related to anchorage failures in CNG heavy
vehicles. Therefore, NHTSA questions the safety relevance of a sled
test for hydrogen-fueled heavy vehicles. NHTSA seeks comment on the
safety need for a heavy vehicle sled test.
GTR No. 13 Phase 2 also considered the possibility of an impact
test for heavy vehicles in place of a full-scale vehicle crash test.
The potential impact
[[Page 27540]]
test would be conducted on the CHSS along with relevant vehicle-
specific shielding, panels and/or structural supports on the vehicle.
It would thereby simulate a vehicle-level crash test without destroying
an entire vehicle. Since the manufacturer is most familiar with the
protective design features of their vehicle, the manufacturer would
specify which shields, panels, and protective structures to include in
the impact test. After the impact, the CHSS would be required to meet
the same leakage limit described above for light vehicles. The
concentration limit in enclosed spaces and the container displacement
requirement would not apply because the impact test would not involve a
full vehicle. NHTSA seeks input and comment with supporting data on
implementing a possible alternative heavy vehicle impact test for the
CHSS.
NHTSA seeks comment on the possibility of including a moving
contoured barrier impact test on heavy vehicles (other than school
buses) in accordance with S6.5 of FMVSS No. 301. This test would allow
for a moving contoured barrier to impact the CHSS along with shields,
panels, and protective structures specified by the manufacturer at any
angle. Such an impact test would evaluate the ability of side-saddle
mounted CHSS to withstand light vehicle impacts and meet the allowable
leakage limits.
C. Lead-Time
NHTSA is proposing that the rule take effect the September 1st the
year after the final rule is published. As discussed above, NHTSA
believes that the requirements in the proposal are closely aligned to
current industry practice and manufacturers will not require an
extended lead-time. NHTSA seeks comment on whether any of the
requirements necessitate additional lead-time.
V. Rulmaking Analyses and Notices
Executive Order 12866, Executive Order 13563, and DOT Regulatory
Policies and Procedures
We have considered the potential impact of this proposed rule under
Executive Order 12866, Executive Order 13563, and DOT Order 2100.6A.
This NPRM is nonsignificant under E.O. 12866 and was not reviewed by
the Office of Management and Budget. It is also not considered ``of
special note to the Department'' under DOT Order 2100.6A, Rulemaking
and Guidance Procedures.
Today, there are only two publicly available vehicle models that
may be affected by the proposed rule, which collectively equal less
than 5,000 vehicles sold per model year. Most manufacturers and vehicle
lines currently in production would be unaffected by this proposal. Of
those vehicles that would be covered by today's proposed standards, we
expect the compliance cost to be minimal. As discussed earlier, the few
manufacturers that already offer hydrogen vehicles in the marketplace
already take safety precautions to attempt to emulate the safety of
conventional and battery electric vehicles, and adhere to the industry
guidelines that informed the creation of GTR No. 13. As today's
proposed rule is intended to coalesce industry practice and future
designs through harmonized regulations, we also do not expect that the
proposal would pose a significant cost to those manufacturers, nor for
those manufacturers that may be planning to enter the market.
Given NHTSA is proposing these standards during the early
development of hydrogen vehicles, there is no baseline to compare
today's proposal against. While we anticipate the regulations, if
adopted, would promote safer hydrogen vehicles, we cannot quantify this
benefit with any degree of certainty, especially given we cannot
forecast what the industry would look like in the absence of our
proposed standard. Furthermore, most of the safety benefits that would
accrue to this rule, would only be realized when hydrogen vehicles
become more prevalent and the net present value of these costs and
benefits would be minimal.
We seek comment on all of these assumptions and ask commenters, if
they do disagree with this assessment, to identify which portions of
the proposal may accrue costs and identify a methodology for
quantifying the potential costs and benefits of this proposal.
Regulatory Flexibility Act
Pursuant to the Regulatory Flexibility Act (5 U.S.C. 601 et seq.,
as amended by the Small Business Regulatory Enforcement Fairness Act
(SBREFA) of 1996), whenever an agency is required to publish a notice
of proposed rulemaking or final rule, it must prepare and make
available for public comment a regulatory flexibility analysis that
describes the effect of the rule on small entities (i.e., small
businesses, small organizations, and small governmental jurisdictions).
The Small Business Administration's regulations at 13 CFR part 121
define a small business, in part, as a business entity ``which operates
primarily within the United States.'' (13 CFR 121.105(a)(1)). No
regulatory flexibility analysis is required if the head of an agency
certifies the proposed or final rule will not have a significant
economic impact on a substantial number of small entities. SBREFA
amended the Regulatory Flexibility Act to require Federal agencies to
provide a statement of the factual basis for certifying that a proposed
or final rule will not have a significant economic impact on a
substantial number of small entities.
I certify that the proposed standards would not have a significant
impact on a substantial number of small entities. This proposed action
would create FMVSS Nos. 307 and 308 to establish minimum safety
requirements for the CHSS and fuel system integrity of hydrogen
vehicles. FMVSS Nos. 307 and 308 are vehicle standards. We anticipate
any burdens of the standard will fall onto manufacturers of hydrogen
vehicles. NHTSA is unaware of any small entities that are planning to
manufacture hydrogen vehicles. Furthermore, NHTSA is proposing to adopt
standards similar to those already in place across industry. Thus, we
anticipate the impacts of this NPRM on all manufacturers to be minimal
regardless of manufacturer size.
Executive Order 13132
NHTSA has examined this proposed rule pursuant to Executive Order
13132 (64 FR 43255, August 10, 1999) and concluded that no additional
consultation with States, local governments or their representatives is
mandated beyond the rulemaking process. The Agency has concluded that
this action would not have ``federalism implications'' because it would
not have ``substantial direct effects on States, on the relationship
between the national government and the States, or on the distribution
of power and responsibilities among the various levels of government,''
as specified in section 1 of the Executive order. This proposed rule
would apply to motor vehicle manufacturers. Further, no State has
adopted requirements regulating the CHSS or fuel integrity of hydrogen
powered vehicles. Thus, Executive Order 13132 is not implicated and
consultation with State and local officials is not required.
NHTSA rules can preempt in two ways. First, the National Traffic
and Motor Vehicle Safety Act contains an express preemption provision:
When a motor vehicle safety standard is in effect under this chapter, a
State or a political subdivision of a State may prescribe or continue
in effect a standard applicable
[[Page 27541]]
to the same aspect of performance of a motor vehicle or motor vehicle
equipment only if the standard is identical to the standard prescribed
under this chapter. 49 U.S.C. 30103(b)(1). It is this statutory command
by Congress that preempts any non-identical State legislative and
administrative law addressing the same aspect of performance.
The express preemption provision described above is subject to a
savings clause under which compliance with a motor vehicle safety
standard prescribed under this chapter does not exempt a person from
liability at common law. 49 U.S.C. 30103(e). Pursuant to this
provision, State common law tort causes of action against motor vehicle
manufacturers that might otherwise be preempted by the express
preemption provision are generally preserved.
However, the Supreme Court has recognized the possibility, in some
instances, of implied preemption of such State common law tort causes
of action by virtue of NHTSA's rules, even if not expressly preempted.
This second way that NHTSA rules can preempt is dependent upon there
being an actual conflict between an FMVSS and the higher standard that
would effectively be imposed on motor vehicle manufacturers if someone
obtained a State common law tort judgment against the manufacturer,
notwithstanding the manufacturer's compliance with the NHTSA standard.
Because most NHTSA standards established by an FMVSS are minimum
standards, a State common law tort cause of action that seeks to impose
a higher standard on motor vehicle manufacturers will generally not be
preempted. However, if and when such a conflict does exist--for
example, when the standard at issue is both a minimum and a maximum
standard--the State common law tort cause of action is impliedly
preempted. See Geier v. American Honda Motor Co., 529 U.S. 861 (2000).
Pursuant to Executive Order 13132 and 12988, NHTSA has considered
whether this proposed rule could or should preempt State common law
causes of action. The agency's ability to announce its conclusion
regarding the preemptive effect of one of its rules reduces the
likelihood that preemption will be an issue in any subsequent tort
litigation. To this end, the agency has examined the nature (i.e., the
language and structure of the regulatory text) and objectives of this
proposed rule and finds that this rule, like many NHTSA rules, would
prescribe only a minimum safety standard. As such, NHTSA does not
intend this NPRM to preempt State tort law that would effectively
impose a higher standard on motor vehicle manufacturers rule.
Establishment of a higher standard by means of State tort law will not
conflict with the minimum standard adopted here. Without any conflict,
there could not be any implied preemption of a State common law tort
cause of action.
Executive Order 12988 (Civil Justice Reform)
When promulgating a regulation, Executive Order 12988 specifically
requires that the agency must make every reasonable effort to ensure
that the regulation, as appropriate: (1) Specifies in clear language
the preemptive effect; (2) specifies in clear language the effect on
existing Federal law or regulation, including all provisions repealed,
circumscribed, displaced, impaired, or modified; (3) provides a clear
legal standard for affected conduct rather than a general standard,
while promoting simplification and burden reduction; (4) specifies in
clear language the retroactive effect; (5) specifies whether
administrative proceedings are to be required before parties may file
suit in court; (6) explicitly or implicitly defines key terms; and (7)
addresses other important issues affecting clarity and general
draftsmanship of regulations.
Pursuant to this Order, NHTSA notes as follows. The preemptive
effect of this proposed rule is discussed above in connection with E.O.
13132. NHTSA notes further that there is no requirement that
individuals submit a petition for reconsideration or pursue other
administrative proceeding before they may file suit in court.
Executive Order 13609 (Promoting International Regulatory Cooperation)
Executive Order 13609, ``Promoting International Regulatory
Cooperation,'' promotes international regulatory cooperation to meet
shared challenges involving health, safety, labor, security,
environmental, and other issues and to reduce, eliminate, or prevent
unnecessary differences in regulatory requirements.
Today's proposed rule adopts the technical requirements of GTR
No.13, a technical standard for hydrogen vehicles adopted by the United
Nations Economic Commission for Europe (UNECE) World Forum for
Harmonization of Vehicle Regulations (WP.29). As a Contracting Party
who voted in favor of GTR No. 13, NHTSA is obligated to initiate
rulemaking to incorporate safety requirements and options specified in
GTR. While today's proposal does contain some differences from GTR No.
13 to reflect U.S. law, they are consistent with the regulatory process
envisioned and encourage from the outset of GTR No. 13. NHTSA will
continue to participate with the international community on GTR No. 13,
and evaluate further amendments on their merits as they are adopted by
WP.29.
NHTSA has analyzed this proposed rule under the policies and agency
responsibilities of Executive Order 13609, and has determined this
proposal would have no effect on international regulatory cooperation.
National Environmental Policy Act
NHTSA has analyzed this NPRM for the purposes of the National
Environmental Policy Act. The agency has determined that implementation
of this action would not have an adverse impact on the quality of the
human environment. As described earlier, the proposal would coalesce
industry practice into uniformed regulations and harmonize with
international standards. NHTSA expects the changes to existing vehicles
would be minimal, and mitigating the hazards associated with hydrogen
leakage and discharge from the fuel system, as well as instituting
post-crash restrictions on hydrogen leakage, concentration in enclosed
spaces, container displacement, and fire, would result in a public
health and safety benefit.
For these reasons, the agency has determined that implementation of
this action would not have any adverse impact on the quality of the
human environment.
Paperwork Reduction Act
Under the procedures established by the Paperwork Reduction Act of
1995 (PRA) (44 U.S.C. 3501, et seq.), Federal agencies must obtain
approval from the OMB for each collection of information they conduct,
sponsor, or require through regulations. A person is not required to
respond to a collection of information by a Federal agency unless the
collection displays a valid OMB control number. The Information
Collection Request (ICR) for a revision of a previously approved
collection described below will be forwarded to OMB for review and
comment. In compliance with these requirements, NHTSA asks for public
comments on the following proposed collection of information for which
the agency is seeking approval from OMB. In this NPRM, we are proposing
a revision to an existing OMB approved collection, OMB Clearance No.
2127-0512, Consolidated Labeling Requirements for Motor Vehicles
(except the VIN). We are soliciting public comment for the
[[Page 27542]]
proposed addition of labeling requirements for FMVSS Nos. 307 and 308.
Title: Consolidated Labeling Requirements for Motor Vehicles
(except the VIN).
OMB Control Number: OMB Control No. 2127-0512.
Type of Request: Revision of a previously approved collection.
Type of Review Requested: Regular.
Requested Expiration Date of Approval: 3 years from the date of
approval.
Summary of the Collection of Information: FMVSS No. 307 specifies
requirements for the integrity of motor vehicle fuel systems using
compressed hydrogen as a fuel source. Each hydrogen vehicle must have a
permanent label which lists the fuel type, service pressure, and a
statement directing vehicle users/operators to instructions for
inspection and service life of the fuel container. FMVSS No. 308
specifies requirements for the integrity of compressed hydrogen storage
systems (CHSS). Each hydrogen container must have a permanent label
containing manufacturer contact information, the container serial
number, manufacturing date, date of removal from service, and
applicable BPO burst pressure. If the proposed requirements
are made final, we will submit a request for OMB clearance of the
proposed collection of information and seek clearance prior to the
effective date of the final rule.
Description of the likely respondents: Vehicle manufacturers.
Estimated Number of Respondents: 20.
Estimated Total Annual Burden Hours: $8,468.
It is estimated that vehicle manufacturers will provide labels on
10 different hydrogen vehicle models. Since manufacturers have provided
CNG vehicles with similar required labels for many years, it is
estimated that manufacturers will have a generalized label template
which only requires minor adjustments for hydrogen and then population
with the required information. There is an annual 1.0 hour burden for
manufacturers to have a Mechanical Drafter put the correct information
into a label template to create a model specific label. The annual
burden for this label creation is 10 hours (10 CNG vehicle model labels
* 1 hour per model label) and $404 (10 CNG vehicle model labels * 1
hour per model label * $28.37 labor rate per hour / 70.3% of labor rate
as total wage compensation). Manufacturers will also bear a cost burden
of $1,884 (2,850 hydrogen vehicles * $0.73 per label) for the required
labels to be attached to the CNG vehicles. The combined total annual
burden to vehicle manufacturers from the requirements to have the
specified label text on hydrogen vehicles is 10 hours and $2,288. These
hour and cost burdens represent a new addition to this information
collection request.
It is estimated that vehicle manufacturers will provide labels on
10 different hydrogen container models. Since manufacturers have
provided CNG containers with similar labels for many years, it is
estimated that manufacturers will have a generalized label template
which only requires only minor adjustments for hydrogen and then
population with their current contact information, the container serial
number, manufacturing date, date of removal from service, and
applicable BPO burst pressure. There is an annual 1.0 hour
burden for manufacturers to have a Mechanical Drafter put the correct
information into a label template to create a model specific label. The
annual burden for this label creation is 10 hours (10 hydrogen
container model labels * 1.0 hours per model label) and $404 (10
hydrogen container models labels * 1.0 hours per model label * $28.37
labor rate per hour / 70.3% of labor rate as total wage compensation).
Manufacturers will also bear a cost burden of $5,776 (7,910 hydrogen
containers * $0.730 per label) for the required labels to be attached
to the hydrogen containers. The combined total annual burden to vehicle
manufacturers from the requirements to have the specified label text on
hydrogen containers is 10 hours and $6,180. These hour and cost burdens
represent a new addition to this information collection request.
Public Comments Invited: You are asked to comment on any aspects of
this information collection, including (a) whether the proposed
collection of information is necessary for the proper performance of
the functions of the Department, including whether the information will
have practical utility; (b) the accuracy of the Department's estimate
of the burden of the proposed information collection; (c) ways to
enhance the quality, utility and clarity of the information to be
collected; and (d) ways to minimize the burden of the collection of
information on respondents, including the use of automated collection
techniques or other forms of information technology.
Please submit any comments, identified by the docket number in the
heading of this document, by the methods described in the ADDRESSES
section of this document to NHTSA and OMB. Although comments may be
submitted during the entire comment period, comments received within 30
days of publication are most useful.
National Technology Transfer and Advancement Act
Under the National Technology Transfer and Advancement Act of 1995
(NTTAA) (Pub. L. 104) Section 12(d) of the National Technology Transfer
and Advancement Act (NTTAA) requires NHTSA to evaluate and use existing
voluntary consensus standards in its regulatory activities unless doing
so would be inconsistent with applicable law (e.g., the statutory
provisions regarding NHTSA's vehicle safety authority) or otherwise
impractical. Voluntary consensus standards are technical standards
developed or adopted by voluntary consensus standards bodies. Technical
standards are defined by the NTTAA as ``performance-based or design-
specific technical specification and related management systems
practices.'' They pertain to ``products and processes, such as size,
strength, or technical performance of a product, process or material.''
Examples of organizations generally regarded as voluntary consensus
standards bodies include ASTM International, the Society of Automotive
Engineers (SAE), and the American National Standards Institute (ANSI).
If NHTSA does not use available and potentially applicable voluntary
consensus standards, we are required by the Act to provide Congress,
through OMB, an explanation of the reasons for not using such
standards.
Today's proposed standards are consistent with voluntary standards
cited above such as SAEJ2578_201408, SAEJ2579_201806, HPRD-1 2021, and
HGV 3.1 2022.
We are proposing to incorporate by reference ISO 6270-2:2017,
Determination of resistance to humidity, Second Edition, November 2017
into Sec. 571.308. ISO 6270-2:2017 specifies methods for assessing the
resistance of materials to humidity by focusing on how materials behave
when exposed to high humidity. The standard provides detailed
procedures for conducting tests in controlled environments where
humidity is the primary variable. These environments simulate
conditions that materials might encounter during their lifecycle,
thereby offering insights into potential degradation processes such as
corrosion, mold growth, or other forms of moisture-induced damage. The
standard sets out guidelines for preparing test specimens, the
conditions
[[Page 27543]]
under which the tests should be conducted, and the criteria for
evaluating the results, including specifying the temperature, humidity
levels, and duration of exposure necessary to evaluate a material's
resistance to humidity. ISO 6270-2:2017 is available on the ISO web
page for purchase and a copy is available for review at NHTSA's
headquarters in Washington, DC through the means identified in
ADDRESSES.\110\
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\110\ See, https://www.iso.org/standard/64858.html.
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We are proposing to incorporate by reference ASTM D1193-06,
Standard Specification for Reagent Water, approved March 22, 2018 into
Sec. 571.308. ASTM D1193-06 is a standard that outlines specifications
for reagent water quality across various scientific and analytical
applications. This standard defines the requirements for the purity of
water used in laboratories, ensuring that experiments and tests are not
compromised by water impurities that could affect the results. It
categorizes water into different types (I, II, III, and IV), each with
specific purity levels suitable for particular applications, ranging
from high-precision analytical work to general laboratory procedures.
The standard details methods for testing and validating the quality of
water, including the acceptable limits for contaminants like organic
and inorganic compounds, as well as microbial content. It also provides
guidelines for the storage and handling of reagent water to maintain
its purity. ASTM D1193-06 is available on the ASTM's online reading
room and a copy is available for review at NHTSA's headquarters in
Washington, DC through the means identified in ADDRESSES.\111\
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\111\ See, https://www.astm.org/d1193-06r18.html.
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This proposal to adopt GTR No. 13 is consistent with the goals of
the NTTAA. This NPRM proposes to adopt a global consensus standard. The
GTR was developed by a global regulatory body and is designed to
increase global harmonization of differing vehicle standards. The GTR
leverages the expertise of governments in developing safety
requirements for hydrogen fueled vehicles. NHTSA's consideration of GTR
No. 13 accords with the principles of NTTAA as NHTSA's consideration of
an established, proven regulation has reduced the need for NHTSA to
expend significant agency resources on the same safety need addressed
by GTR No. 13.
Unfunded Mandates Reform Act
Section 202 of the Unfunded Mandates Reform Act of 1995 (UMRA)
requires Federal agencies to prepare a written assessment of the costs,
benefits, and other effects of proposed or final rules that include a
Federal mandate likely to result in the expenditure by State, local, or
Tribal governments, in the aggregate, or by the private sector, of more
than $100 million annually (adjusted for inflation with base year of
1995). Adjusting this amount by the implicit gross domestic product
price deflator for the year 2020 results in $158 million (113.625/
71.868 = 1.581). Before promulgating a rule for which a written
statement is needed, section 205 of the UMRA generally requires the
agency to identify and consider a reasonable number of regulatory
alternatives and adopt the least costly, most cost-effective, or least
burdensome alternative that achieves the objectives of the rule. The
provisions of section 205 do not apply when they are inconsistent with
applicable law. Moreover, section 205 allows the agency to adopt an
alternative other than the least costly, most cost-effective, or least
burdensome alternative if the agency publishes with the final rule an
explanation of why that alternative was not adopted.
This NPRM would not result in expenditures by State, local, or
Tribal governments, in the aggregate, or by the private sector in
excess of $158 million (in 2020 dollars) annually. As a result, the
requirements of Section 202 of the Act do not apply.
Executive Order 13045 (Protection of Children From Environmental Health
and Safety Risks)
Executive Order 13045, ``Protection of Children from Environmental
Health and Safety Risks,'' (62 FR 19885, April 23, 1997) applies to any
proposed or final rule that: (1) Is determined to be ``economically
significant,'' as defined in E.O. 12866, and (2) concerns an
environmental health or safety risk that NHTSA has reason to believe
may have a disproportionate effect on children. If a rule meets both
criteria, the agency must evaluate the environmental health or safety
effects of the rule on children and explain why the rule is preferable
to other potentially effective and reasonably feasible alternatives
considered by the agency.
This rulemaking is not subject to the Executive order because it is
not economically significant as defined in E.O. 12866.
Executive Order 13211
Executive Order 13211 (66 FR 28355, May 18, 2001) applies to any
rulemaking that: (1) is determined to be economically significant as
defined under E.O. 12866, and is likely to have a significantly adverse
effect on the supply of, distribution of, or use of energy; or (2) that
is designated by the Administrator of the Office of Information and
Regulatory Affairs as a significant energy action. This rulemaking is
not subject to E.O. 13211 as this rule is not economically significant
and should not have an adverse effect on the supply of, distribution
of, or use of energy as explained in our discussion of Executive Orders
12866 and 13563.
Plain Language
Executive Order 12866 requires each agency to write all rules in
plain language. Application of the principles of plain language
includes consideration of the following questions:
Have we organized the material to suit the public's needs?
Are the requirements in the rule clearly stated?
Does the rule contain technical language or jargon that
isn't clear?
Would a different format (grouping and order of sections,
use of headings, paragraphing) make the rule easier to understand?
Would more (but shorter) sections be better?
Could we improve clarity by adding tables, lists, or
diagrams?
What else could we do to make the rule easier to
understand?
If you have any responses to these questions, please include them
in your comments on this proposal.
Regulation Identifier Number (RIN)
The Department of Transportation assigns a regulation identifier
number (RIN) to each regulatory action listed in the Unified Agenda of
Federal Regulations. The Regulatory Information Service Center
publishes the Unified Agenda in April and October of each year. You may
use the RIN contained in the heading at the beginning of this document
to find this action in the Unified Agenda.
VI. Public Participation
How do I prepare and submit comments?
To ensure that your comments are correctly filed in the Docket,
please include the Docket Number in your comments.
Your comments must be written and in English. Your comments must
not be more than 15 pages long. NHTSA established this limit to
encourage you to write your primary comments in a concise fashion.
However, you may attach necessary additional documents
[[Page 27544]]
to your comments, and there is no limit on the length of the
attachments.
If you are submitting comments electronically as a PDF (Adobe)
file, NHTSA asks that the documents be submitted using the Optical
Character Recognition (OCR) process, thus allowing NHTSA to search and
copy certain portions of your submissions.
Please note that pursuant to the Data Quality Act, in order for
substantive data to be relied on and used by NHTSA, it must meet the
information quality standards set forth in the OMB and DOT Data Quality
Act guidelines. Accordingly, NHTSA encourages you to consult the
guidelines in preparing your comments. DOT's guidelines may be accessed
at https://www.transportation.gov/regulations/dot-information-dissemination-quality-guidelines.
Tips for Preparing Your Comments
When submitting comments, please remember to:
Identify the rulemaking by docket number and other identifying
information (subject heading, Federal Register date and page number).
Explain why you agree or disagree, suggest alternatives, and
substitute language for your requested changes.
Describe any assumptions you make and provide any technical
information and/or data that you used.
If you estimate potential costs or burdens, explain how you arrived
at your estimate in sufficient detail to allow for it to be reproduced.
Provide specific examples to illustrate your concerns and suggest
alternatives.
Explain your views as clearly as possible, avoiding the use of
profanity or personal threats.
To ensure that your comments are considered by the agency, make
sure to submit them by the comment period deadline identified in the
DATES section above.
For additional guidance on submitting effective comments, see
https://www.regulations.gov/docs/Tips_For_Submitting_Effective_Comments.pdf.
How can I be sure my comments were received?
If you wish Docket Management to notify you upon its receipt of
your comments, enclose a self-addressed, stamped postcard in the
envelope containing your comments. Upon receiving your comments, Docket
Management will return the postcard by mail.
How do I submit confidential business information?
If you wish to submit any information under a claim of
confidentiality, you should submit three copies of your complete
submission, including the information you claim to be confidential
business information, to the Chief Counsel, NHTSA, at the address given
above under FOR FURTHER INFORMATION CONTACT. In addition, you should
submit a copy from which you have deleted the claimed confidential
business information to the docket. When you send a comment containing
information claimed to be confidential business information, you should
include a cover letter setting forth the information specified in our
confidential business information regulation. (49 CFR part 512.)
Will the Agency consider late comments?
NHTSA will consider all comments that the docket receives before
the close of business on the comment closing date indicated above under
DATES. To the extent possible, NHTSA will also consider comments that
the docket receives after that date. If the docket receives a comment
too late for the agency to consider it in developing a final rule,
NHTSA will consider that comment as an informal suggestion for future
rulemaking action.
How can I read the comments submitted by other people?
You may read the comments received by the docket at the address
given above under ADDRESSES. You may also see the comments on the
internet (http://regulations.gov).
Please note that even after the comment closing date, NHTSA will
continue to file relevant information in the docket as it becomes
available. Further, some people may submit late comments. Accordingly,
the agency recommends that you periodically check the docket for new
material.
Anyone is able to search the electronic form of all comments
received into any of our dockets by the name of the individual
submitting the comment (or signing the comment, if submitted on behalf
of an association, business, labor union, etc.). You may review DOT's
complete Privacy Act Statement in the Federal Register published on
April 11, 2000 (Volume 65, Number 70; Pages 19477-78).
List of Subjects in 49 CFR Part 571
Imports, Incorporation by reference, Motor vehicle safety,
Reporting and recordkeeping requirements, Tires.
In consideration of the foregoing, NHTSA proposes to amend 49 CFR
part 571 as set forth below.
PART 571--FEDERAL MOTOR VEHICLE SAFETY STANDARDS
0
1. The authority citation for part 571 continues to read as follows:
Authority: 49 U.S.C. 322, 30111, 30115, 30117 and 30166;
delegation of authority at 49 CFR 1.95.
0
2. Section 571.5 is amended by:
0
a. In paragraph (d), redesignating paragraphs (19) through (39) as
paragraphs (20) through (40) and adding paragraph (19); and
0
b. In paragraph (i), redesignating paragraphs (1) through (4) as
paragraphs (2) through (5) and adding paragraph (1).
The additions read as follows:
Sec. 571.5 Matter incorporated by reference.
* * * * *
(d) * * *
(19) ASTM D1193-06 (Reapproved 2018), Standard Specification for
Reagent Water, approved March 22, 2018; into Sec. 571.308.
* * * * *
(i) * * *
(1) ISO 6270-2:2017, Determination of resistance to humidity,
Second Edition, November 2017; into Sec. 571.308.
* * * * *
0
3. Section 571.307 is added to read as follows:
Sec. 571.307 Standard No. 307; Fuel system integrity of hydrogen
vehicles.
S1. Scope. This standard specifies requirements for the integrity
of motor vehicle hydrogen fuel systems.
S2. Purpose. The purpose of this standard is to reduce deaths and
injuries occurring from fires that result from hydrogen fuel leakage
during vehicle operation and after motor vehicle crashes.
S3. Application. This standard applies to each motor vehicle that
uses compressed hydrogen gas as a fuel source to propel the vehicle.
S4. Definitions.
Check valve means a valve that prevents reverse flow.
Closure devices mean the check valve(s), shut-off valve(s) and
thermally activated pressure relief device(s) that control the flow of
hydrogen into and/or out of a CHSS.
Container means a pressure-bearing component of a compressed
hydrogen storage system that stores a continuous volume of hydrogen
fuel in a single chamber or in multiple permanently interconnected
chambers.
Container attachments means non-pressure bearing parts attached to
the container that provide additional support or protection to the
container
[[Page 27545]]
and that may be removed only with the use of tools for the specific
purpose of maintenance or inspection.
Compressed hydrogen storage system (CHSS) means a system that
stores compressed hydrogen fuel for a hydrogen-fueled vehicle, composed
of a container, container attachments (if any), and all closure devices
required to isolate the stored hydrogen from the remainder of the fuel
system and the environment.
Enclosed or semi-enclosed spaces means the volumes external to the
hydrogen fuel system such as the passenger compartment, luggage
compartment, and space under the hood.
Fuel cell system means a system containing the fuel cell stack(s),
air processing system, fuel flow control system, exhaust system,
thermal management system and water management system.
Fueling receptacle means the equipment to which a fueling station
nozzle attaches to the vehicle and through which fuel is transferred to
the vehicle.
Fuel lines means all piping, tubing, joints, and any components
such as flow controllers, valves, heat exchangers, and pressure
regulators.
Hydrogen concentration means the percentage of the hydrogen
molecules within the mixture of hydrogen and air (equivalent to the
partial volume of hydrogen gas).
Hydrogen fuel system mean the fueling receptacle, CHSS, fuel cell
system or internal combustion engine, fuel lines, and exhaust systems.
Luggage compartment means the space in the vehicle for luggage,
cargo, and/or goods accommodation, bounded by a roof, hood, floor, side
walls being separated from the passenger compartment by the front
bulkhead or the rear bulkhead.
Maximum allowable working pressure (MAWP) means the highest gauge
pressure to which a component or system is permitted to operate under
normal operating conditions.
Nominal working pressure (NWP) means the settled pressure of
compressed gas in a container or CHSS fully fueled to 100 percent state
of charge and at a uniform temperature of 15 [deg]C.
Normal milliliter means a quantity of gas that occupies one
milliliter of volume when its temperature is 0 [deg]C and its pressure
is 1 atmosphere.
Passenger compartment means the space for occupant accommodation
that is bounded by the roof, floor, side walls, doors, outside glazing,
front bulkhead, and rear bulkhead or rear gate.
Pressure relief device (PRD) means a device that, when activated
under specified performance conditions, is used to release hydrogen
from a pressurized system and thereby prevent failure of the system.
Rechargeable electrical energy storage system (REESS) means the
rechargeable energy storage system that provides electric energy for
electrical propulsion.
Service door means a door that allows for the entry and exit of
vehicle occupants under normal operating conditions.
Shut-off valve means an automatically activated valve between the
container and the remainder of the hydrogen fuel system that must
default to the ``closed'' position when not connected to a power
source.
State of charge (SOC) means the density ratio of hydrogen in the
CHSS between the actual CHSS condition and that at NWP with the CHSS
equilibrated to 15 [deg]C, as expressed as a percentage using the
formula:
[GRAPHIC] [TIFF OMITTED] TP17AP24.015
where [rho] is the density of hydrogen (g/L) at pressure (P) in
MegaPascals (MPa) and temperature (T) in Celsius ([deg]C) as listed
in the table below or linearly interpolated therein.
Table 1 to Sec. 571.307
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pressure (Mpa)
Temperature ([deg]C) -------------------------------------------------------------------------------------------------------
1 10 20 30 35 40 50 60 65 70 75 80 87.5
--------------------------------------------------------------------------------------------------------------------------------------------------------
-40............................................. 1.0 9.7 18.1 25.4 28.6 31.7 37.2 42.1 44.3 46.4 48.4 50.3 53.0
-30............................................. 1.0 9.4 17.5 24.5 27.7 30.6 36.0 40.8 43.0 45.1 47.1 49.0 51.7
-20............................................. 1.0 9.0 16.8 23.7 26.8 29.7 35.0 39.7 41.9 43.9 45.9 47.8 50.4
-10............................................. 0.9 8.7 16.2 22.9 25.9 28.7 33.9 38.6 40.7 42.8 44.7 46.6 49.2
0............................................... 0.9 8.4 15.7 22.2 25.1 27.9 33.0 37.6 39.7 41.7 43.6 45.5 48.1
10.............................................. 0.9 8.1 15.2 21.5 24.4 27.1 32.1 36.6 38.7 40.7 42.6 44.4 47.0
15.............................................. 0.8 7.9 14.9 21.2 24.0 26.7 31.7 36.1 38.2 40.2 42.1 43.9 46.5
20.............................................. 0.8 7.8 14.7 20.8 23.7 26.3 31.2 35.7 37.7 39.7 41.6 43.4 46.0
30.............................................. 0.8 7.6 14.3 20.3 23.0 25.6 30.4 34.8 36.8 38.8 40.6 42.4 45.0
40.............................................. 0.8 7.3 13.9 19.7 22.4 24.9 29.7 34.0 36.0 37.9 39.7 41.5 44.0
50.............................................. 0.7 7.1 13.5 19.2 21.8 24.3 28.9 33.2 35.2 37.1 38.9 40.6 43.1
60.............................................. 0.7 6.9 13.1 18.7 21.2 23.7 28.3 32.4 34.4 36.3 38.1 39.8 42.3
70.............................................. 0.7 6.7 12.7 18.2 20.7 23.1 27.6 31.7 33.6 35.5 37.3 39.0 41.4
80.............................................. 0.7 6.5 12.4 17.7 20.2 22.6 27.0 31.0 32.9 34.7 36.5 38.2 40.6
85.............................................. 0.7 6.4 12.2 17.5 20.0 22.3 26.7 30.7 32.6 34.4 36.1 37.8 40.2
--------------------------------------------------------------------------------------------------------------------------------------------------------
Thermally-activated pressure relief device (TPRD) means a non-
reclosing PRD that is activated by temperature to open and release
hydrogen gas.
S5. Hydrogen fuel system.
S5.1. Fuel system integrity during normal vehicle operations.
S5.1.1. Fueling receptacle requirements.
(a) A compressed hydrogen fueling receptacle shall prevent reverse
flow to the atmosphere.
(b) A label shall be affixed close to the fueling receptacle
showing the following information:
(1) The statement, ``Compressed hydrogen gas only.''
(2) The statement, ``Service pressure __ MPa (__ psig).''
(3) The statement, ``See instructions on fuel container(s) for
inspection and service life.''
(c) The fueling receptacle shall ensure positive locking of the
fueling nozzle.
(d) The fueling receptacle shall be protected from the ingress of
dirt and water.
(e) The fueling receptacle shall not be mounted to or within the
impact energy-absorbing elements of the vehicle and shall not be
installed in enclosed or semi-enclosed spaces.
S5.1.2. Over-pressure protection for the low-pressure system. An
overpressure protection device is required downstream of a pressure
regulator to protect the low-pressure
[[Page 27546]]
portions of the hydrogen fuel system from overpressure. The activation
pressure of the overpressure protection device shall be less than or
equal to the MAWP for the respective downstream section of the hydrogen
fuel system.
S5.1.3. Hydrogen discharge systems.
S5.1.3.1. Pressure relief systems.
(a) If present, the outlet of the vent line for hydrogen gas
discharge from the TPRD(s) of the CHSS shall be protected from ingress
of dirt and water.
(b) With the vehicle on a level surface, the hydrogen gas discharge
from the TPRD(s) of the CHSS shall be directed upwards within 20[deg]
of vertical relative to the level surface or downwards within 45[deg]
of vertical relative to the level surface.
(c) The hydrogen gas discharge from TPRD(s) of the CHSS shall not
impinge upon:
(1) Enclosed or semi-enclosed spaces;
(2) Any vehicle wheel housing;
(3) Container(s);
(4) REESS(s);
(5) Any emergency exit(s) as identified in FMVSS No. 217; nor
(6) Any service door(s).
S5.1.3.2. Vehicle exhaust system. When tested in accordance with
S6.5, the hydrogen concentration at the vehicle exhaust system's point
of discharge shall not:
(a) Exceed an average of 4.0 percent by volume during any moving
three-second time interval, and
(b) Exceed 8.0 percent by volume at any time.
S5.1.4 Protection against flammable conditions.
(a) When tested in accordance with S6.4.1, a warning in accordance
with S5.1.6 shall be provided within 10 seconds of the application of
the first test gas. When tested in accordance with S6.4.1, the main
shut-off valve shall close within 10 seconds of the application of the
second test gas.
(b) When tested in accordance with S6.4.2, the hydrogen
concentration in the enclosed or semi-enclosed spaces shall be less
than 3.0 percent.
S5.1.5 Fuel system leakage. When tested in accordance with S6.6,
the hydrogen fuel system downstream of the shut-off valve(s) shall not
leak.
S5.1.6 Tell-tale warning. The warning shall be given to the driver,
or to all front seat occupants for vehicles without a driver's
designated seating position, by a visual signal or display text with
the following properties:
(a) Visible to the driver while seated in the driver's designated
seating position or visible to all front seat occupants of vehicles
without a driver's designated seating position;
(b) Yellow in color if the warning system malfunctions;
(c) Red in color if hydrogen concentration in enclosed or semi-
enclosed spaces exceeds 3.0 percent by volume;
(d) When illuminated, shall be visible to the driver (or to all
front seat occupants in vehicles without a driver's designated seating
position) under both daylight and night-time driving conditions; and
(e) Remains illuminated when hydrogen concentration in any of the
vehicle's enclosed or semi-enclosed spaces exceeds 3.0 percent by
volume or when the warning system malfunctions, and the ignition
locking system is in the ``On'' (``Run'') position or the propulsion
system is activated.
S5.2. Post-crash fuel system integrity. Each vehicle with a gross
vehicle weight rating (GVWR) of 4,536 kg or less to which this standard
applies must meet the requirements in S5.2.1 through S5.2.4 when tested
according to S6 under the conditions of S7. Each school bus with a GVWR
greater than 4,536 kg to which this standard applies must meet the
requirements in S5.2.1 through S5.2.4 when tested according to S6 under
the conditions of S7.
S5.2.1. Fuel leakage limit. If hydrogen gas is used for testing,
the volumetric flow of hydrogen gas leakage shall not exceed an average
of 118 normal liters per minute for the time interval, [Delta]t, as
determined in accordance with S6.2.1. If helium is used for testing,
the volumetric flow of helium leakage shall not exceed an average of
88.5 normal litres per minute for the time interval, [Delta]t, as
determined in accordance with S6.2.2.
S5.2.2. Concentration limit in enclosed spaces. One of the
requirements in (a), (b) or (c).
(a) Hydrogen gas leakage shall not result in a hydrogen
concentration in the air greater than 4.0 percent by volume in enclosed
or semi-enclosed spaces for 60 minutes after impact when tested in
accordance with S6.3.
(b) Helium gas leakage shall not result in a helium concentration
in the air greater than 3.0 percent by volume in enclosed or semi-
enclosed spaces for 60 minutes after impact when tested in accordance
with S6.3.
(c) The shut-off valve of the CHSS shall close within 5 seconds of
the crash.
S5.2.3. Container displacement. The container(s) shall remain
attached to the vehicle by at least one component anchorage, bracket,
or any structure that transfers loads from the container to the vehicle
structure.
S5.2.4. Fire. There shall be no fire in or around the vehicle for
the duration of the test.
S6. Test Requirements.
S6.1. Vehicle Crash Tests. A test vehicle with a GVWR less than or
equal to 4,536 kg, under the conditions of S7, is subject to any one
single barrier crash test of S6.1.1, S6.1.2, and S6.1.3. A school bus
with a GVWR greater than 4,536 kg, under the conditions of S7, is
subject to the contoured barrier crash test of S6.1.4. A vehicle
subject to S6 need not undergo further testing.
S6.1.1. Frontal barrier crash. The test vehicle, with test dummies
in accordance with S6.1 of 571.301 of this chapter, traveling
longitudinally forward at any speed up to and including 48.0 km/h,
impacts a fixed collision barrier that is perpendicular to the line of
travel of the vehicle, or at an angle up to 30 degrees in either
direction from the perpendicular to the line of travel of the vehicle.
S6.1.2. Rear moving barrier impact. The test vehicle, with test
dummies in accordance with S6.1 of 571.301 of this chapter, is impacted
from the rear by a barrier that conforms to S7.3(b) of 571.301 of this
chapter and that is moving at any speed up to and including 80.0 km/h.
S6.1.3. Side moving deformable barrier impact. The test vehicle,
with the appropriate 49 CFR part 572 test dummies specified in 571.214
at positions required for testing by S7.1.1, S7.2.1, or S7.2.2 of
Standard 214, is impacted laterally on either side by a moving
deformable barrier moving at any speed between 52.0 km/h and 54.0 km/h.
S6.1.4. Moving contoured barrier crash. The test vehicle is
impacted at any point and at any angle by the moving contoured barrier
assembly, specified in S7.5 and S7.6 in 571.301 of this chapter,
traveling longitudinally forward at any speed up to and including 48.0
km/h.
S6.2. Post-crash CHSS leak test.
S6.2.1. Post-crash leak test for CHSS filled with compressed
hydrogen.
(a) The hydrogen gas pressure, P0 (MPa), and
temperature, T0 ([deg]C), shall be measured immediately
before the impact. The hydrogen gas pressure Pf (MPa) and
temperature, Tf ([deg]C) shall also be measured immediately
after a time interval [Delta]t (in minutes) after impact. The time
interval, [Delta]t, starting from the time of impact, shall be the
greater of:
(1) 60 minutes; or
(2) [Delta]t = VCHSS x NWP/1000 x ((-0.027 x NWP + 4) x
Rs - 0.21) - 1.7 x Rs
where Rs = Ps/ NWP, Ps is the
pressure range of the pressure sensor (MPa), NWP is the Nominal
Working Pressure (MPa), and VCHSS is the volume of the
CHSS (L).
[[Page 27547]]
(b) The initial mass of hydrogen M0 (g) in the CHSS
shall be calculated from the following equations:
P0' = P0 x 288 / (273 + T0)
[rho]0' = -0.0027 x (P0')\2\ + 0.75 x
P0' + 1.07
M0 = [rho]0' x VCHSS
(c) The final mass of hydrogen in the CHSS, Mf (in
grams), at the end of the time interval, [Delta]t, shall be calculated
from the following equations:
Pf' = Pf x 288/(273 + Tf)
[rho]f' = -0.0027 x (Pf')\2\ + 0.75 x
Pf' + 1.07
Mf = [rho]f' x VCHSS
where Pf is the measured final pressure (MPa) at the end
of the time interval, and Tf ([deg]C) is the measured
final temperature.
(d) The average hydrogen flow rate over the time interval shall be
calculated from the following equation:
VH2 = (Mf - M0)/[Delta]t x 22.41/2.016
x (Ptarget/P0)
where VH2 is the average volumetric flow rate (normal
millilitres per min) over the time interval.
S6.2.2 Post-crash leak test for CHSS filled with compressed helium.
(a) The helium pressure, P0 (MPa), and temperature,
T0 ([deg]C), shall be measured immediately before the impact
and again immediately after a time interval starting from the time of
impact. The time interval, [Delta]t (min), shall be the greater of:
(1) 60 minutes; or
(2) [Delta]t = VCHSS x NWP/1000 x ((-0.028 x NWP + 5.5)
x Rs - 0.3) - 2.6 x Rs
where Rs = Ps/NWP, Ps is the
pressure range of the pressure sensor (MPa), NWP is the Nominal
Working Pressure (MPa), and VCHSS is the volume of the
CHSS (L).
(b) The initial mass of helium M0 (g) in the CHSS shall
be calculated from the following equations:
P0' = P0 x 288 / (273 + T0)
[rho]0' = -0.0043 x (P0')\2\ + 1.53 x
P0' + 1.49
M0 = [rho]0' x VCHSS
(c) The final mass of helium Mf (g) in the CHSS at the
end of the time interval, [Delta]t (min), shall be calculated from the
following equations:
Pf' = Pf x 288/(273 + Tf)
[rho]f' = -0.0043 x (Pf')\2\ + 1.53 x
Pf' + 1.49
Mf = [rho]f' x VCHSS
where Pf is the measured final pressure (MPa) at the end
of the time interval, and Tf ([deg]C) is the measured
final temperature.
(d) The average helium flow rate over the time interval shall be
calculated from the following equation:
VHe = (Mf - M0)/[Delta]t x 22.41/4.003
x (Ptarget/P0)
where VHe is the average volumetric flow rate (normal
millilitres per min) of helium over the time interval.
S6.3. Post-crash concentration test for enclosed spaces.
(a) Sensors shall measure either the accumulation of hydrogen or
helium gas, as appropriate, or the reduction in oxygen.
(b) Sensors shall have an accuracy of at least 5 percent at 4.0
percent hydrogen or 3.0 percent helium by volume in air, and a full-
scale measurement capability of at least 25 percent above these
criteria. The sensor shall be capable of a 90 percent response to a
full-scale change in concentration within 10 seconds.
(c) Prior to the crash impact, the sensors shall be located in the
passenger and luggage compartments of the vehicle as follows:
(1) At any interior point at any distance between 240 mm and 260 mm
of the headliner above the driver's seat or near the top center of the
passenger compartment.
(2) At any interior point at any distance between 240 mm and 260 mm
of the floor in front of the rear (or rear most) seat in the passenger
compartment.
(3) At any interior point at any distance between 90 mm and 110 mm
below the top of luggage compartment(s).
(d) The sensors shall be securely mounted on the vehicle structure
or seats and protected from debris, air bag exhaust gas and
projectiles.
(e) The vehicle shall be located either indoors or in an area
outdoors protected from direct and indirect wind.
(f) Post-crash data collection in enclosed spaces shall commence
from the time of impact. Data from the sensors shall be collected at
least every 5 seconds and continue for a period of 60 minutes after the
impact.
(g) The data shall be compiled into a three-data-point rolling
average prior to evaluating the applicable concentration limit in
accordance with S5.2.2(a) or S5.2.2(b).
S6.4. Test procedure for protection against flammable conditions.
S6.4.1. Test for hydrogen gas leakage detectors.
(a) The vehicle shall be set to the ``on'' or ``run'' position for
at least 5 minutes prior to testing, and left operating for the test
duration. If the vehicle is not a fuel cell vehicle, it shall be warmed
up and kept idling. If the test vehicle has a system to stop idling
automatically, measures shall be taken to prevent the engine from
stopping.
(b) Two mixtures of air and hydrogen gas shall be used in the test:
The first test gas has any hydrogen concentration between 3.0 and 4.0
percent by volume in air to verify function of the warning, and the
second test gas has any hydrogen concentration between 4.0 and 6.0
percent by volume in air to verify function of the shut-down.
(c) The test shall be conducted without any influence of wind.
(d) A vehicle hydrogen leakage detector located in the enclosed or
semi-enclosed spaces is enclosed with a cover and a test gas induction
hose is attached to the hydrogen gas leakage detector.
(e) The hydrogen gas leakage detector is exposed to continuous flow
of the first test gas specified in (b) until the warning turns on.
(f) Then the hydrogen gas leakage detector is then exposed to
continuous flow of the second test gas specified in (b) until the main
shut-off valve closes to isolate the CHSS. The test is completed when
the shut-off valve closes.
S6.4.2. Test for integrity of enclosed spaces and detection
systems.
(a) The test shall be conducted without influence of wind.
(b) Prior to the test, the vehicle is prepared to simulate remotely
controllable hydrogen releases from the fuel system or from an external
fuel supply. The number, location, and flow capacity of the release
points downstream of the shut-off valve are defined by the vehicle
manufacturer.
(c) A hydrogen concentration detector shall be installed in any
enclosed or semi-enclosed volume where hydrogen may accumulate from the
simulated hydrogen release.
(d) Vehicle doors, windows and other covers are closed.
(e) The vehicle shall be set to the ``on'' or ``run'' position for
at least 5 minutes prior to testing, and left operating for the test
duration. If the vehicle is not a fuel cell vehicle, it shall be warmed
up and kept idling. If the test vehicle has a system to stop idling
automatically, measures shall be taken to prevent the engine from
stopping.
(f) A leak shall be simulated using the remote controllable
function.
(g) The hydrogen concentration is measured continuously until the
end of the test.
(h) The test is completed 5 minutes after initiating the simulated
leak or when the hydrogen concentration does not change for 3 minutes,
whichever is longer.
S6.5. Test for the vehicle exhaust system.
(a) The vehicle shall be set to the ``on'' or ``run'' position for
at least 5 minutes prior to testing.
(b) The measuring section of the measuring device shall be placed
along the centerline of the exhaust gas flow within 100 mm of where the
exhaust is released to the atmosphere.
[[Page 27548]]
(c) The exhaust hydrogen concentration shall be continuously
measured during the following steps:
(1) The fuel cell system shall be shut down.
(2) The fuel cell system shall be immediately restarted.
(3) After one minute, the vehicle shall be set to the ``off''
position and measurement continues until the until the vehicle shut-
down is complete shut-down procedure is completed.
(d) The measurement device shall have a resolution time of less
than 300 milliseconds;
(e) Have a measurement response time (t0 -
t90) of less than 2 seconds, where t0 is the
moment of hydrogen concentration switching, and t90 is the
time when 90 percent of the final indication is reached and have a
resolution time of less than 300 milliseconds (sampling rate of greater
than 3.33 Hz).
S6.6. Test for fuel system leakage. The vehicle CHSS shall be
filled with hydrogen to any pressure between 90 percent NWP and 100
percent NWP for the duration of the test for fuel system leakage.
(a) The vehicle shall be set to the ``on'' or ``run'' position for
at least 5 minutes prior to testing, and left operating for the test
duration. If the vehicle is not a fuel cell vehicle, it shall be warmed
up and kept idling. If the test vehicle has a system to stop idling
automatically, measures shall be taken to prevent the engine from
stopping.
(b) Hydrogen leakage shall be evaluated at accessible sections of
the hydrogen fuel system downstream of the shut-off valve(s), using a
gas leak detector or a leak detecting liquid as follows:
(1) When a gas leak detector is used, detection shall be performed
by operating the leak detector for at least 10 seconds at locations as
close to fuel lines as possible.
(2) When a leak detecting liquid is used, hydrogen gas leak
detection shall be performed immediately after applying the liquid.
S7. Test Conditions. The requirements of S5.2 shall be met under
the following conditions. Where a range of conditions is specified, the
vehicle must be capable of meeting the requirements at all points
within the range.
(a) Prior to conducting the crash test, instrumentation is
installed in the CHSS to perform the required pressure and temperature
measurements if the vehicle does not already have instrumentation with
the required accuracy.
(b) The CHSS is then purged, if necessary, following manufacturer
directions before filling the CHSS with compressed hydrogen or helium
gas.
(c) The target fill pressure Ptarget shall be calculated
from the following equation:
Ptarget = NWP x (273 + To)/288
where NWP is in MPa, To is the ambient temperature in
[deg]C to which the CHSS is expected to settle, and
Ptarget is the target fill pressure in MPa after the
temperature settles.
(d) The container(s) shall be filled to any pressure between 95.0
percent and 100.0 percent of the calculated target fill pressure.
(e) After fueling, the vehicle shall be maintained at rest for any
duration between 2.0 and 3.0 hours before conducting a crash test in
accordance with S6.1.
(f) The CHSS shut-off valve(s) and any other shut-off valves
located in the fuel system downstream hydrogen gas piping shall be in
normal driving condition immediately prior to the impact.
(g) The parking brake is disengaged and the transmission is in
neutral prior to the crash test.
(h) Tires are inflated to manufacturer's specifications.
(i) The vehicle, including test devices and instrumentation, is
loaded as follows:
(1) A passenger car, with its fuel system filled as specified in
S7(d), is loaded to its unloaded vehicle weight plus its rated cargo
and luggage capacity weight, secured in the luggage area, plus the
necessary test dummies as specified in S6, restrained only by means
that are installed in the vehicle for protection at its seating
position.
(2) A multipurpose passenger vehicle, truck, or bus with a GVWR of
10,000 pounds or less, whose fuel system is filled as specified in
S7(d), is loaded to its unloaded vehicle weight, plus the necessary
test dummies as specified in S6, plus 136.1 kg, or its rated cargo and
luggage capacity weight, whichever is less, secured to the vehicle and
distributed so that the weight on each axle as measured at the tire-
ground interface is in proportion to its gross axle weight rating
(GAWR). Each dummy shall be restrained only by means that are installed
in the vehicle for protection at its seating position.
(3) A school bus with a GVWR greater than 10,000 pounds, whose fuel
system is filled as specified in S7(d), is loaded to its unloaded
vehicle weight, plus 54.4 kg of unsecured weight at each designated
seating position.
0
5. Section 571.308 is added to read as follows:
Sec. 571.308 Standard No. 308; Compressed hydrogen storage system
integrity.
S1. Scope. This standard specifies requirements for compressed
hydrogen storage systems used in motor vehicles.
S2. Purpose. The purpose of this standard is to reduce deaths and
injuries occurring from fires that result from hydrogen leakage during
vehicle operation and to reduce deaths and injuries occurring from
explosions resulting from the burst of pressurized hydrogen containers.
S3. Application. This standard applies to each motor vehicle that
uses compressed hydrogen gas as a fuel source.
S4. Definitions.
BPO means the manufacturer-supplied median burst pressure for a
batch of new containers.
Burst means to break apart or to break open.
Burst pressure means the highest pressure achieved for a container
tested in accordance with S6.2.2.1.
Check valve means a valve that prevents reverse flow.
Closure devices mean the check valve(s), shut-off valve(s) and
thermally activated pressure relief device(s) that control the flow of
hydrogen into and/or out of a CHSS.
Container means a pressure-bearing component of a compressed
hydrogen storage system that stores a continuous volume of hydrogen
fuel in a single chamber or in multiple permanently interconnected
chambers.
Container attachments means non-pressure bearing parts attached to
the container that provide additional support and/or protection to the
container and that may be removed only with the use of tools for the
specific purpose of maintenance and/or inspection.
Compressed hydrogen storage system (CHSS) means a system that
stores compressed hydrogen fuel for a hydrogen-fueled vehicle, composed
of a container, container attachments (if any), and all closure devices
required to isolate the stored hydrogen from the remainder of the fuel
system and the environment.
Nominal working pressure (NWP) means the settled pressure of
compressed gas in a container or CHSS fully fueled to 100 percent state
of charge and at a uniform temperature of 15 [deg]C.
Normal milliliter means a quantity of gas that occupies one
milliliter of volume when its temperature is 0 [deg]C and its pressure
is 1 atmosphere.
Pressure relief device (PRD) means a device that, when activated
under specified performance conditions, is
[[Page 27549]]
used to release hydrogen from a pressurized system and thereby prevent
failure of the system.
Service life (of a container) means the time frame during which
service (usage) is authorized by the manufacturer.
Shut-off valve means an electrically activated valve between the
container and the remainder of the vehicle fuel system that must
default to the ``closed'' position when unpowered.
State of charge (SOC) means the density ratio of hydrogen in the
CHSS between the actual CHSS condition and that at NWP with the CHSS
equilibrated to 15 [deg]C, as expressed as a percentage using the
formula:
[GRAPHIC] [TIFF OMITTED] TP17AP24.016
where [rho] is the density of hydrogen (g/L) at pressure (P) in
MegaPascals (MPa) and temperature (T) in Celsius ([deg]C) as listed
in the table below or linearly interpolated therein.
Table 2 to Sec. 571.307
--------------------------------------------------------------------------------------------------------------------------------------------------------
Pressure (MPa)
Temperature ([deg]C) --------------------------------------------------------------------------------------------------------------------
1 10 20 30 35 40 50 60 65 70 75 80 87.5
--------------------------------------------------------------------------------------------------------------------------------------------------------
-40................................ 1.0 9.7 18.1 25.4 28.6 31.7 37.2 42.1 44.3 46.4 48.4 50.3 53.0
-30................................ 1.0 9.4 17.5 24.5 27.7 30.6 36.0 40.8 43.0 45.1 47.1 49.0 51.7
-20................................ 1.0 9.0 16.8 23.7 26.8 29.7 35.0 39.7 41.9 43.9 45.9 47.8 50.4
-10................................ 0.9 8.7 16.2 22.9 25.9 28.7 33.9 38.6 40.7 42.8 44.7 46.6 49.2
0.................................. 0.9 8.4 15.7 22.2 25.1 27.9 33.0 37.6 39.7 41.7 43.6 45.5 48.1
10................................. 0.9 8.1 15.2 21.5 24.4 27.1 32.1 36.6 38.7 40.7 42.6 44.4 47.0
15................................. 0.8 7.9 14.9 21.2 24.0 26.7 31.7 36.1 38.2 40.2 42.1 43.9 46.5
20................................. 0.8 7.8 14.7 20.8 23.7 26.3 31.2 35.7 37.7 39.7 41.6 43.4 46.0
30................................. 0.8 7.6 14.3 20.3 23.0 25.6 30.4 34.8 36.8 38.8 40.6 42.4 45.0
40................................. 0.8 7.3 13.9 19.7 22.4 24.9 29.7 34.0 36.0 37.9 39.7 41.5 44.0
50................................. 0.7 7.1 13.5 19.2 21.8 24.3 28.9 33.2 35.2 37.1 38.9 40.6 43.1
60................................. 0.7 6.9 13.1 18.7 21.2 23.7 28.3 32.4 34.4 36.3 38.1 39.8 42.3
70................................. 0.7 6.7 12.7 18.2 20.7 23.1 27.6 31.7 33.6 35.5 37.3 39.0 41.4
80................................. 0.7 6.5 12.4 17.7 20.2 22.6 27.0 31.0 32.9 34.7 36.5 38.2 40.6
85................................. 0.7 6.4 12.2 17.5 20.0 22.3 26.7 30.7 32.6 34.4 36.1 37.8 40.2
--------------------------------------------------------------------------------------------------------------------------------------------------------
Thermally-activated pressure relief device (TPRD) means a non-
reclosing PRD that is activated by temperature to open and release
hydrogen gas.
TPRD sense point means instrumentation that detects elevated
temperature for the purpose of activating a TPRD.
S5. Requirements.
S5.1. Requirements for the CHSS. Each vehicle CHSS shall include
the following functions: shut-off valve, check valve, and TPRD. Each
vehicle CHSS shall have a NWP of 70 MPa or less. Each vehicle
container, closure device, and CHSS, shall meet the applicable
performance test requirements listed in the table below.
Table 3 to S5.1
------------------------------------------------------------------------
Requirement section Test article
------------------------------------------------------------------------
S5.1.1. Tests for baseline metrics......... Container.
S5.1.2. Test for performance durability.... Container.
S5.1.3. Test for expected on-road CHSS.
performance.
S5.1.4. Test for service terminating CHSS.
performance in fire.
S5.1.5. Tests for performance durability of Closure devices.
closure devices.
------------------------------------------------------------------------
S5.1.1. Tests for baseline metrics.
S5.1.1.1 Baseline initial burst pressure. The manufacturer shall
immediately specify upon request, in writing, and within five business
days: the primary constituent of the container. When a new container
with its container attachments (if any) is tested in accordance with
S6.2.2.1, all of the following requirements shall be met:
(a) The burst pressure of the container shall not be less than 2
times NWP.
(b) The burst pressure of the container having glass-fiber
composite as a primary constituent shall not be less than 3.5 times
NWP.
(c) The bust pressure of the container for which the manufacturer
fails to specify upon request, in writing, and within five business
days, the primary constituent of the container, shall not be less than
3.5 times NWP.
(d) The burst pressure of the container shall be within 10 percent
of the BPO listed on the container label.
S5.1.1.2. Baseline initial pressure cycle test. When a new
container with its container attachments (if any) is hydraulically
pressure cycled in accordance with S6.2.2.2 to any pressure between
125.0 percent NWP and 130.0 percent NWP,
(a) containers for vehicles with a GVWR of 10,000 pounds or less
(1) shall not leak nor burst for at least 7,500 cycles, and
(2) thereafter shall not burst for an additional 14,500 cycles. If
the required pressure cannot be achieved due to leakage or if a visible
leak occurs for more than 3 minutes while conducting the test as
specified in S5.1.1.2(a)(2), the test is stopped and not considered a
failure.
(b) containers for vehicles with a GVWR of over 10,000 pounds
(1) shall not leak nor burst for at least 11,000 cycles, and
(2) thereafter shall not burst for an additional 11,000 cycles. If
the required pressure cannot be achieved due to leakage or if a visible
leak occurs for more than 3 minutes while conducting the test as
specified in S5.1.1.2(b)(2), the test is stopped and not considered a
failure.
S5.1.2. Test for performance durability. A new container shall not
leak nor burst when subjected to the sequence of tests in S5.1.2.1 to
S5.1.2.7. Immediately following S5.1.2.7, and without depressurizing
the container, the container is subjected to a burst test in accordance
with S6.2.2.1(c) and S6.2.2.1(d). The burst pressure of the container
at the end of the sequence of
[[Page 27550]]
tests in this section shall not be less than 0.8 times the
BPO listed on the container label. The sequence of tests and
the burst pressure test are illustrated in Figure 1.
S5.1.2.1. Proof pressure test. The container with its container
attachments (if any) is hydraulically pressurized in accordance with
S6.2.3.1 to any pressure between 1.500 times NWP and 1.550 times NWP
and held for any duration between 30.0 to 35.0 seconds.
S5.1.2.2. Drop test. The container with its container attachments
(if any) is dropped once in accordance with S6.2.3.2 in any one of the
four orientations specified in that section. Any container with damage
from the drop test that prevents further testing of the container in
accordance with S6.2.3.4 shall be considered to have failed to meet the
test for performance durability requirements.
S5.1.2.3. Surface damage test. The container, except if an all-
metal container, is subjected to the surface damage test in accordance
with the S6.2.3.3. Container attachments designed to be removed shall
be removed and container attachments that are not designed to be
removed shall remain in place. Container attachments that are removed,
shall not be reinstalled for the remainder of S5.1.2; container
attachments that are not removed, shall remain in place for the
remainder of S5.1.2.
S5.1.2.4. Chemical exposure and ambient-temperature pressure
cycling test. The container is exposed to chemicals in accordance with
S6.2.3.4 and then hydraulically pressure cycled in accordance with
S6.2.3.4 for 60 percent of the number of cycles as specified in
S5.1.1.2(a)(1) or S5.1.1.2(b)(1) as applicable. For all but the last 10
of these cycles, the cycling pressure shall be any pressure between
125.0 percent NWP and 130.0 percent NWP. For the last 10 cycles, the
pressure shall be any pressure between 150.0 percent NWP and 155.0
percent NWP.
S5.1.2.5. High temperature static pressure test. The container is
pressurized to any pressure between (or equal to) 125 percent NWP and
130 percent NWP and held at that pressure no less than 1,000 and no
more than 1,050 hours in accordance with S6.2.3.5 and with the
temperature surrounding the container at any temperature between 85.0
[deg]C and 90.0 [deg]C.
S5.1.2.6. Extreme temperature pressure cycling test. The container
is pressure cycled in accordance with S6.2.3.6 for 40 percent of the
number of cycles specified in S5.1.1.2(a)(1) or S5.1.1.2(b)(1) as
applicable. The pressure for the first half of these cycles equals any
pressure between 80.0 percent NWP and 85.0 percent NWP with the
temperature surrounding the container equal to any temperature between
-45.0 [deg]C and -40.0 [deg]C. The pressure for the next half of these
cycles equals any pressure between 125.0 percent NWP and 130.0 percent
NWP and the temperature surrounding the container equal to any
temperature between 85.0 [deg]C and 90.0 [deg]C and the relative
humidity surrounding the container not less than 80 percent.
S5.1.2.7. Residual pressure test. The container is hydraulically
pressurized in accordance with S6.2.3.1 to a pressure between 180.0
percent NWP and 185.0 percent NWP and held for any duration between 240
to 245 seconds.
S5.1.3. Test for expected on-road performance. When subjected to
the sequence of tests in S5.1.3.1 to S5.1.3.2, the CHSS shall meet the
permeation and leak requirements specified in S5.1.3.3 and shall not
burst. Thereafter, the container of the CHSS shall not burst when
subjected to a residual pressure test in accordance with S5.1.3.4.
Immediately following S5.1.3.4, and without depressurizing the
container, the container of the CHSS is subjected to a burst test in
accordance with S6.2.2.1(c) and S6.2.2.1(d). The burst pressure of the
container at the end of the sequence of tests in this section shall not
be less than 0.8 times the BPO listed on the container
label.
S5.1.3.1. Proof pressure test. The container of the CHSS is
pressurized with hydrogen gas to any pressure between 1.500 times NWP
and 1.550 times NWP and held for any duration between 30 to 35 seconds
in accordance with the S6.2.3.1 test procedure. The ambient temperature
surrounding the container shall be at any temperature between 5.0
[deg]C to 35.0 [deg]C. The fuel delivery temperature used for
pressurizing the container with hydrogen shall be at any temperature
between -40.0 [deg]C to -33.0 [deg]C.
S5.1.3.2. Ambient and extreme temperature gas pressure cycling
test. The CHSS is pressure cycled using hydrogen gas for 500 cycles
under any temperature and pressure condition for the number of cycles
as specified in the Table to S5.1.3.2, and in accordance with the
S6.2.4.1 test procedure. A static gas pressure leak/permeation test
performed in accordance with S5.1.3.3 is conducted after the first 250
pressure cycles and after the remaining 250 pressure cycles.
Table 4 to S5.1.3.2
--------------------------------------------------------------------------------------------------------------------------------------------------------
Initial system Fuel delivery Cycle initial and
Number of cycles Ambient conditions equilibration temperature final pressure Cycle peak pressure
--------------------------------------------------------------------------------------------------------------------------------------------------------
5.................................. -30.0 [deg]C to -25.0 -30.0 [deg]C to -25.0 15.0 [deg]C to 25.0 1.0 MPa to 2.0 MPa... 100.0% SOC to 105.0%
[deg]C. [deg]C. [deg]C. SOC.
5.................................. -30.0 [deg]C to -25.0 -30.0 [deg]C to -25.0 -40.0 [deg]C to -33.0 1.0 MPa to 2.0 MPa... 100.0% SOC to 105.0%
[deg]C. [deg]C. [deg]C. SOC.
15................................. -30.0 [deg]C to -25.0 not appliable......... -40.0 [deg]C to -33.0 1.0 MPa to 2.0 MPa... 100.0% SOC to 105.0%
[deg]C. [deg]C. SOC.
5.................................. 50.0 [deg]C to 55.0 50 [deg]C to 55 [deg]C -40.0 [deg]C to -33.0 1.0 MPa to 2.0 MPa... 100.0% SOC to 105.0%
[deg]C 80% to 100% 80% to 100% relative [deg]C. SOC.
relative humidity. humidity.
20................................. 50.0 [deg]C to 55.0 not appliable......... -40.0 [deg]C to -33.0 1.0 MPa to 2.0 MPa... 100.0% SOC to 105.0%
[deg]C, 80% to 100% [deg]C. SOC.
relative humidity.
200................................ 5.0 [deg]C to 35.0 not appliable......... -40.0 [deg]C to -33.0 1.0 MPa to 2.0 MPa... 100.0% SOC to 105.0%
[deg]C. [deg]C. SOC.
Extreme temperature static gas 55.0 [deg]C to 60.0 55.0 [deg]C to 60.0 not appliable........ not appliable........ 100.0% SOC to 105.0%
pressure leak/permeation test [deg]C. [deg]C. SOC.
S5.1.3.3.
[[Page 27551]]
25................................. 50.0 [deg]C to 55.0 not appliable......... -40.0 [deg]C to -33.0 1.0 MPa to 2.0 MPa... 100.0% SOC to 105.0%
[deg]C,. [deg]C. SOC.
80% to 100% relative
humidity.
25................................. -30.0 [deg]C to -25.0 not appliable......... -40.0 [deg]C to -33.0 1.0 MPa to 2.0 MPa... 100.0% SOC to 105.0%
[deg]C. [deg]C. SOC.
200................................ 5.0 [deg]C to 35.0 not appliable......... -40.0 [deg]C to -33.0 1.0 MPa to 2.0 MPa... 100.0% SOC to 105.0%
[deg]C. [deg]C. SOC.
Extreme temperature static gas 55.0 [deg]C to 60.0 55.0 [deg]C to 60.0 not appliable........ not appliable........ 100.0% SOC to 105.0%
pressure leak/permeation test [deg]C. [deg]C. SOC.
S5.1.3.3.
--------------------------------------------------------------------------------------------------------------------------------------------------------
S5.1.3.3. Extreme temperature static gas pressure leak/permeation
test. When tested in accordance with S6.2.4.2 after each group of 250
pneumatic pressure cycles in S5.1.3.2, the CHSS shall not discharge
hydrogen more than 46 millilitres per hour (mL/h) for each litre of
CHSS water capacity.
S5.1.3.4. Residual pressure test. The container of the CHSS is
hydraulically pressurized in accordance with S6.2.3.1 to any pressure
between 1.800 times NWP and 1.850 times NWP and held at that pressure
for any duration between 240 to 245 seconds.
S5.1.4. Test for service terminating performance in fire. When the
CHSS is exposed to the two-stage localized or engulfing fire test in
accordance with S6.2.5, the container shall not burst. The pressure
inside the CHSS shall fall to 1 MPa or less within the test time limit
specified in S6.2.5.3(o). Any leakage or venting, other than that
through TPRD outlet(s), shall not result in jet flames greater than 0.5
m in length. If venting occurs though the TPRD, the venting shall be
continuous.
S5.1.5. Tests for performance durability of closure devices. All
tests are performed at ambient temperature of 5 [deg]C to 35 [deg]C
unless otherwise specified.
S5.1.5.1. TPRD requirements. The TPRD shall not activate at any
point during the test procedures specified in S6.2.6.1.1, S6.2.6.1.3,
S6.2.6.1.4, S6.2.6.1.5, S6.2.6.1.6, S6.2.6.1.7, and S6.2.6.1.8.
(a) A TPRD subjected to pressure cycling in accordance with
S6.2.6.1.1, shall be sequentially tested in accordance with S6.2.6.1.8,
S6.2.6.1.9, and S6.2.6.1.10;
(1) When tested in accordance with S6.2.6.1.8, the TPRD shall not
exhibit leakage greater than 10 normal milliliters per minute (NmL/
hour).
(2) When tested in accordance with S6.2.6.1.9, the TPRD shall
activate within no more than 2 minutes of the average activation time
of three new TPRDs tested in accordance with S6.2.6.1.9;
(3) When tested in accordance with S6.2.6.1.10, the TPRD shall have
a flow rate of at least 90 percent of the highest baseline flow rate
established in accordance with S6.2.6.1.10;
(b)(1) A TPRD shall activate in less than ten hours when tested at
the manufacturer's specified activation temperature in accordance with
S6.2.6.1.2.
(2) When tested at the accelerated life temperature in accordance
with S6.2.6.1.2, a TPRD shall not activate in less than 500 hours and
shall not exhibit leakage greater than 10 NmL/hour when tested in
accordance with S6.2.6.1.8;
(c) A TPRD subjected to temperature cycling testing in accordance
with S6.2.6.1.3 shall be sequentially tested in accordance with
S6.2.6.1.8(a)(3), S6.2.6.1.9, and S6.2.6.1.10;
(1) When tested in accordance with S6.2.6.1.8(a)(3), the TPRD shall
not exhibit leakage greater than 10 NmL/hour;
(2) When tested in accordance with S6.2.6.1.9, the TPRD shall
activate within no more than 2 minutes of the average activation time
of three new TPRDs tested in accordance with S6.2.6.1.9;
(3) When tested in accordance with S6.2.6.1.10, the TPRD shall have
a flow rate of at least 90 percent of the highest baseline flow rate
established in accordance with S6.2.6.1.10;
(d) A TPRDs subjected to salt corrosion resistance testing in
accordance with S6.2.6.1.4 shall be sequentially tested in accordance
with S6.2.6.1.8, S6.2.6.1.9, and S6.2.6.1.10;
(1) When tested in accordance with S6.2.6.1.8, the TPRD shall not
exhibit leakage greater than 10 NmL/hour;
(2) When tested in accordance with S6.2.6.1.9, the TPRD shall
activate within no more than 2 minutes of the average activation time
of three new TPRDs tested in accordance with S6.2.6.1.9;
(3) When tested in accordance with S6.2.6.1.10, the TPRD shall have
a flow rate of at least 90 percent of the highest baseline flow rate
established in accordance with S6.2.6.1.10;
(e) A TPRD subjected to vehicle environment testing in accordance
with S6.2.6.1.5 shall not show signs of cracking, softening, or
swelling, and thereafter shall be sequentially tested in accordance
with S6.2.6.1.8, S6.2.6.1.9, and S6.2.6.1.10.
(1) When tested in accordance with S6.2.6.1.8, the TPRD shall not
exhibit leakage greater than 10 NmL/hour.
(2) When tested in accordance with S6.2.6.1.9, the TPRD shall
activate within no more than 2 minutes of the average activation time
of three new TPRDs tested in accordance with S6.2.6.1.9,
(3) When tested in accordance with S6.2.6.1.10, the TPRD shall have
a flow rate of at least 90 percent of the highest baseline flow rate
established in accordance with S6.2.6.1.10;
(f) A TPRD subjected to stress corrosion cracking testing in
accordance with S6.2.6.1.6 shall not exhibit visible cracking or
delaminating;
(g) A TPRD shall be subjected to drop and vibration testing in
accordance with S6.2.6.1.7. If the TPRD progresses beyond S6.2.6.1.7(c)
to complete testing under S6.2.6.1.7(d), it shall then be sequentially
tested in accordance with S6.2.6.1.8, S6.2.6.1.9, and S6.2.6.1.10.
(1) When tested in accordance with S6.2.6.1.8, the TPRD shall not
exhibit leakage greater than 10 NmL/hour.
(2) When tested in accordance with S6.2.6.1.9, the TPRD shall
activate within no more than 2 minutes of the average activation time
of three new TPRDs tested in accordance with S6.2.6.1.9,
(3) When tested in accordance with S6.2.6.1.10, the TPRD shall have
a flow rate of at least 90 percent of the highest baseline flow rate
established in accordance with S6.2.6.1.10;
[[Page 27552]]
(h) One new TPRD subjected to leak testing in accordance with
S6.2.6.1.8 shall not exhibit leakage greater than 10 NmL/hour;
(i) Three new TPRDs are subjected to a bench top activation test in
accordance with S6.2.6.1.9. The maximum difference in the activation
time between any two of the three TPRDs shall be 2 minutes or less.
S5.1.5.2. Check valve and shut-off valve requirements. This section
applies to both check valves and shut-off valves.
(a) A valve subjected to hydrostatic strength testing in accordance
with S6.2.6.2.1 shall not leak nor burst at less than 250 percent NWP;
(b) A valve subjected to leak testing in accordance with S6.2.6.2.2
shall not exhibit leakage greater than 10 NmL/hour;
(c)(1) A check valve shall meet the requirements when tested
sequentially as follows:
(i) The check valve shall reseat and prevent reverse flow after
each cycle when subjected to 13,500 pressure cycles in accordance with
S6.2.6.2.3 to any pressure between 100.0 and 105.0 percent NWP and at
any temperature between 5.0 [deg]C and 35.0 [deg]C;
(ii) The same check valve shall reseat and prevent reverse flow
after each cycle when subjected to 750 pressure cycles in accordance
with S6.2.6.2.3 to any pressure between 125.0 and 130.0 percent NWP and
at any temperature between 85.0 [deg]C and 90.0 [deg]C;
(iii) The same check valve shall reseat and prevent reverse flow
after each cycle when subjected to 750 pressure cycles in accordance
with S6.2.6.2.3 to any pressure between 80.0 and 85.0 percent NWP and
at any temperature between -45.0 [deg]C and -40.0 [deg]C;
(iv) The same check valve shall be subjected to chatter flow
testing in accordance with S6.2.6.2.4;
(v) When tested in accordance with S6.2.6.2.2, the same check valve
shall not exhibit leakage greater than 10 NmL/hour;
(vi) When tested in accordance S6.2.6.2.1, the same check valve
shall not leak nor burst at less than 250 percent NWP nor burst at less
than 80 percent of the burst pressure of the new unit tested in
accordance with S5.1.5.2(a) unless the burst pressure of the valve
exceeds 400 percent NWP.
(2) A shut-off valve shall meet the requirements when tested
sequentially as follows:
(i) The shut-off valve shall be subjected to 45,000 pressure cycles
in accordance with S6.2.6.2.3 to any pressure between 100.0 and 105.0
percent NWP and at any temperature between 5.0 [deg]C and 35.0 [deg]C;
(ii) The same shut-off valve shall be subjected to 2,500 pressure
cycles in accordance with S6.2.6.2.3 to any pressure between 125.0 and
130.0 percent NWP and at any temperature between 85.0 [deg]C and 90.0
[deg]C;
(iii) The same shut-off valve subjected to 2,500 pressure cycles in
accordance with S6.2.6.2.3 to any pressure between 80.0 and 85.0
percent NWP and at any temperature between -45.0 [deg]C and -40.0
[deg]C;
(iv) The same shut-off valve shall be subjected to chatter flow
testing in accordance with S6.2.6.2.4;
(v) When tested in accordance with S6.2.6.2.2, the same shut-off
valve shall not exhibit leakage greater than 10 NmL/hour;
(vi) When tested in accordance S6.2.6.2.1, the same shut-off valve
shall not leak nor burst at less than 250 percent NWP nor burst at less
than 80 percent of the burst pressure of the new unit tested in
accordance with S5.1.5.2(a) unless the burst pressure of the valve
exceeds 400 percent NWP.
(d) A valve subjected to salt corrosion resistance testing in
accordance with S6.2.6.1.4 shall be tested sequentially in accordance
with S6.2.6.2.2 followed by S6.2.6.2.1.
(1) When tested in accordance with S6.2.6.2.2, the valve shall not
exhibit leakage greater than 10 NmL/hour;
(2) When tested in accordance S6.2.6.2.1, the valve shall not leak
nor burst at less than 250 percent NWP nor burst at less than 80
percent of the burst pressure of the new unit tested in accordance with
S5.1.5.2(a) unless the burst pressure of the valve exceeds 400 percent
NWP;
(e) A valve subjected to vehicle environment testing in accordance
with S6.2.6.1.5 shall not show signs of cracking, softening, or
swelling and shall be tested sequentially in accordance with S6.2.6.2.2
followed by S6.2.6.2.1. Cosmetic changes such as pitting or staining
are not considered failures.
(1) When tested in accordance with S6.2.6.2.2, the valve shall not
exhibit leakage greater than 10 NmL/hour;
(2) When tested in accordance S6.2.6.2.1, the valve shall not leak
nor burst at less than 250 percent NWP nor burst at less than 80
percent of the burst pressure of the new unit tested in accordance with
S5.1.5.2(a) unless the burst pressure of the valve exceeds 400 percent
NWP;
(f) A shut-off valve shall have a minimum resistance of 240
k[Omega] between the power conductor and the valve casing, and shall
not exhibit open valve, smoke, fire, melting, or leakage greater than
10 NmL/hour when subjected to electrical testing in accordance with
S6.2.6.2.5 followed by leak testing in accordance with 6.2.6.2.2;
(g) A valve subjected to vibration testing in accordance with
S6.2.6.2.6 shall be tested sequentially in accordance with S6.2.6.2.2
followed by S6.2.6.2.1.
(1) When tested in accordance with S6.2.6.2.2, the valve shall not
exhibit leakage greater than 10 NmL/hour;
(2) When tested in accordance S6.2.6.2.1, the valve shall not leak
nor burst at less than 250 percent NWP nor burst at less than 80
percent of the burst pressure of the new unit tested in accordance with
S5.1.5.2(a) unless the burst pressure of the valve exceeds 400 percent
NWP;
(h) A valve shall not exhibit visible cracking or delaminating when
subjected to stress corrosion cracking testing in accordance with
S6.2.6.1.6;
S5.1.6. Labeling. Each vehicle container shall be permanently
labeled with the information specified in paragraphs (a) through (f) of
this section. Any label affixed to the container in compliance with
this section shall remain in place and be legible for the
manufacturer's recommended service life of the container. The
information shall be in English and in letters and numbers that are at
least 6.35 millimeters (\1/4 \inch) high.
(a) The statement: ``If there is a question about the proper use,
installation, or maintenance of this compressed hydrogen storage
system, contact ___,'' inserting the vehicle manufacturer's name,
address, and telephone number. The name provided shall be consistent
with the manufacturer's filing in accordance with 49 CFR part 566.
(b) The container serial number.
(c) The statement: ``Manufactured in ___,'' inserting the month and
year of manufacture of the container.
(d) The statement ``Nominal Working Pressure ___ MPa (___psig)''
Inserting the nominal working pressure which shall be no greater than
70 MPa.
(e) The statement ``Compressed Hydrogen Gas Only.''
(f) The statement: ``Do Not Use After ___'' inserting the month and
year that mark the end of the manufacturer's recommended service life
for the container.
(g) The statement: ``This container should be visually inspected
for damage and deterioration after a motor vehicle accident or fire,
and either (i) at least every 12 months when installed on a vehicle
with a GVWR greater than 4,536 kg, or (ii) at least every 36 months or
36,000 miles, whichever comes first,
[[Page 27553]]
when installed on a vehicle with a GVWR less than or equal to 4,536
kg.''
(h) The statement: ``The burst pressure BPO applicable
to this container is ___'' inserting the manufacturer's specified value
of BPO in MPa.
S6. Test procedures
S6.1. [Reserved]
S6.2. Test procedures for compressed hydrogen storage.
S6.2.1. Unless otherwise specified, data sampling for pressure
cycling under S6.2 shall be at least 1 Hz.
S6.2.2. Test procedures for baseline performance metrics.
S6.2.2.1. Burst test.
(a) The container is filled with a hydraulic fluid.
(b) The container, the surrounding environment, and the hydraulic
fluid are at any temperature between 5.0 [deg]C and 35.0 [deg]C.
(c) The rate of pressurization shall be less than or equal to 1.4
MPa per second for pressures higher than 1.50 times NWP. If the rate
exceeds 0.35 MPa per second at pressures higher than 1.50 times NWP,
then the container is placed in series between the pressure source and
the pressure measurement device.
(d) The container is hydraulically pressurized until burst and the
burst pressure of the container is recorded.
S6.2.2.2. Pressure cycling test.
(a) The container is filled with a hydraulic fluid.
(b) The container surface, or the surface of the container
attachments if present, the environment surrounding the container, and
the hydraulic fluid are at any temperature between 5.0 [deg]C and 35.0
[deg]C at the start of testing and maintained at the specified
temperature for the duration of the testing.
(c) The container is pressure cycled at any pressure between 1.0
MPa and 2.0 MPa up to the pressure specified in the respective section
of S5. The cycling rate shall be any rate between or equal to 5 and 10
cycles per minute.
(d) The temperature of the hydraulic fluid entering the container
is maintained and monitored at any temperature between 5.0 [deg]C and
35.0 [deg]C.
(e) The container manufacturer may specify a hydraulic pressure
cycle profile within the specifications of S6.2.2.2(c). Manufacturers
shall submit this profile to NHTSA upon request, in writing, and within
five business days, otherwise NHTSA shall determine the profile. At
NHTSA's option, NHTSA shall cycle the container within 10 percent of
the manufacturer's specified cycling profile.
S6.2.3. Performance durability test.
S6.2.3.1. Proof pressure test. The container is pressurized
smoothly and continually with hydraulic fluid or hydrogen gas as
specified until the pressure level is reached and held for the
specified time.
S6.2.3.2. Drop impact test. The container is drop tested without
internal pressurization or attached valves. The surface onto which the
container is dropped shall be a smooth, horizontal, uniform, dry,
concrete pad or other flooring type with equivalent hardness. No
attempt shall be made to prevent the container from bouncing or falling
over during a drop test, except for the vertical drop test, during
which the test article shall be prevented from falling over. The
container shall be dropped in any one of the following four
orientations described below and illustrated in Figure 2.
(a) From a position within 5[deg] of horizontal with the lowest
point of the container at any height between 1.800 meters and 1.820
meters above the surface onto which it is dropped. In the case of a
non-axisymmetric container, the largest projection area of the
container shall be oriented downward and aligned horizontally;
(b) From a position within 5[deg] of vertical with the center of
any shut-off valve interface location upward and with any potential
energy of between 488 Joules and 538 Joules. If a drop energy of
between 488 Joules and 538 Joules would result in the height of the
lower end being more than 1.820 meters above the surface onto which it
is dropped, the container shall be dropped from any height with the
lower end between 1.800 meters and 1.820 meters above the surface onto
which it is dropped. If a drop energy of between 488 Joules and 538
Joules would result in the height of the lower end being less than
0.100 meters above the surface onto which it is dropped, the container
shall be dropped from any height with the lower end between 0.100
meters and 0.120 meters above the surface onto which it is dropped. In
the case of a non-axisymmetric container, the center of any shut-off
valve interface location and the container's center of gravity shall be
aligned vertically, with the center of that shut-off valve interface
location upward;
(c) From a position within 5[deg] of vertical with the center of
any shut-off valve interface location downward with any potential
energy of between 488 Joules and 538 Joules. If a potential energy of
between 488 Joules and 538 Joules would result in the height of the
lower end being more than 1.820 meters above the surface onto which it
is dropped, the container shall be dropped from any height with the
lower end between 1.800 meters and 1.820 meters above the surface onto
which it is dropped. If a drop energy of between 488 Joules and 538
Joules would result in the height of the lower end being less than
0.100 meters above the surface onto which it is dropped, the container
shall be dropped from any height with the lower end between 0.100
meters and 0.120 meters above the surface onto which it is dropped. In
the case of a non-axisymmetric container, the center of any shut-off
valve interface location and the container's center of gravity shall be
aligned vertically, with the center of that shut-off valve interface
location downward;
(d) From any angle between 40[deg] and 50[deg] from the vertical
orientation with the center of any shut-off valve interface location
downward, and with the container center of gravity between 1.800 meters
and 1.820 meters above the surface onto which it is dropped. However,
if the lowest point of the container is closer to the ground than 0.60
meters, the drop angle shall be changed so that the lowest point of the
container is between 0.60 meters and 0.62 meters above the ground and
the center of gravity is between 1.800 meters and 1.820 meters above
the surface onto which it is dropped. In the case of a non-axisymmetric
container, the line passing through the center of any shut-off valve
interface location and the container's center of gravity shall be at
any angle between 40[deg] and 50[deg] from the vertical orientation. If
this results in more than one possible container orientation, the drop
shall be conducted from the orientation that results in the lowest
positioning of the center of the shut-off valve interface location.
S6.2.3.3. Surface damage test. The surface damage test consists of
surface cut generation and pendulum impacts as described below.
(a) Surface cut generation: Two longitudinal saw cuts are made at
any location on the same side of the outer surface of the unpressurized
container, as shown in Figure 3, or on the container attachments if
present. The first cut is 0.75 millimeters to 1.25 millimeters deep and
200 millimeters to 205 millimeters long; The second cut, which is only
required for containers affixed to the vehicle by compressing its
composite surface, is 1.25 millimeters to 1.75 millimeters deep and 25
millimeters to 28 millimeters long.
(b) Pendulum impacts: Mark the outer surface of the container, or
the container attachments if present, on the side opposite from the saw
cuts, with five separate, non-overlapping circles each having any
linear diameter between 100.0 millimeters and 105.0 millimeters, as
shown in Figure 3. Within 30
[[Page 27554]]
minutes following preconditioning for any duration from 12 hours to 24
hours in an environmental chamber at any temperature between -45.0
[deg]C and -40.0 [deg]C, impact the center of each of the five areas
with a pendulum having a pyramid with equilateral faces and square
base, and the tip and edges being rounded to a radius of between 2.0
millimeters and 4.0 millimeters. The center of impact of the pendulum
shall coincide with the center of gravity of the pyramid. The energy of
the pendulum at the moment of impact with each of the five marked areas
on the container is any energy between 30.0 Joules and 35.0 Joules. The
container is secured in place during pendulum impacts and is not
pressurized above 1 MPa.
S6.2.3.4. Chemical exposure and ambient temperature pressure
cycling test.
(a) Each of the 5 areas preconditioned by pendulum impact in
S6.2.3.3(b) is exposed to any one of five solutions:
(1) 19 to 21 percent by volume sulfuric acid in water;
(2) 25 to 27 percent by weight sodium hydroxide in water;
(3) 5 to 7 percent by volume methanol in gasoline;
(4) 28 to 30 percent by weight ammonium nitrate in water; and
(5) 50 to 52 percent by volume methyl alcohol in water.
(b) The container is oriented with the fluid exposure areas on top.
A pad of glass wool approximately 0.5 centimeters thick and 100
millimeters in diameter is placed on each of the five preconditioned
areas. A sufficient amount of the test fluid is applied to the glass
wool to ensure that the pad is wetted across its surface and through
its thickness for the duration of the test. A plastic covering shall be
applied over the glass wool to prevent evaporation.
(c) The exposure of the container with the glass wool is maintained
for at least 48 hours and no more than 60 hours with the container
hydraulically pressurized to any pressure between 125.0 percent NWP and
130.0 percent NWP. During exposure, the temperature surrounding the
container is maintained at any temperature between 5.0 [deg]C and 35.0
[deg]C.
(d) Hydraulic pressure cycling is performed in accordance with
S6.2.2.2 at any pressure within the specified ranges according to
S5.1.2.4 for the specified number of cycles. The glass wool pads are
removed and the container surface is rinsed with water after the cycles
are complete.
S6.2.3.5. Static pressure test. The container is hydraulically
pressurized to the specified pressure in a temperature-controlled
chamber. The temperature of the chamber and the container surface, or
the surface of the container attachments if present, are held at the
specified temperature for the specified duration.
S6.2.3.6. Extreme temperature pressure cycling test.
(a) The container is filled with hydraulic fluid for each test;
(b) At the start of each test, the container surface, or the
surface of the container attachments if present, the hydraulic fluid,
and the environment surrounding the container are at any temperature
and relative humidity (if applicable) within the ranges specified in
S5.1.2.6 and maintained for the duration of the testing.
(c) The container is pressure cycled from any pressure between 1.0
MPa and 2.0 MPa up to the specified pressure at a rate not exceeding 10
cycles per minute for the specified number of cycles;
(d) The temperature of the hydraulic fluid entering the container
shall be measured as close as possible to the container inlet.
S6.2.4. Test procedures for expected on-road performance.
S6.2.4.1. Ambient and extreme temperature gas pressure cycling
test.
(a) In accordance with the Table to S5.1.3.2, the specified ambient
conditions of temperature and relative humidity, if applicable, are
maintained within the test environment throughout each pressure cycle.
When required in accordance with the Table to S5.1.3.2, the CHSS
temperature shall be in the specified initial system equilibration
temperature range between pressure cycles.
(b) The CHSS is pressure cycled from any pressure between 1.0 MPa
and 2.0 MPa up to any pressure within the specified peak pressure range
in accordance with the Table to S5.1.3.2. The temperature of the
hydrogen fuel dispensed to the container is controlled to within the
specified temperature range within 30 seconds of fueling initiation.
The specified number of pressure cycles are conducted.
(c) The ramp rate for pressurization shall be greater than or equal
to the ramp rate given in the Table to S6.2.4.1(c) according to the
CHSS volume, the ambient conditions, and the fuel delivery temperature.
If the required ambient temperature is not available in the table, the
closest ramp rate value or a linearly interpolated value shall be used.
The pressure ramp rate shall be decreased if the gas temperature in the
container exceeds 85 [deg]C.
Table 5 to S6.2.4.1(c)
--------------------------------------------------------------------------------------------------------------------------------------------------------
CHSS pressurization rate (MPa/min)
---------------------------------------------------------------------------------------------------
50.0 [deg]C to 55.0 5.0 [deg]C to 35.0 -30.0 [deg]C to -25.0 -30.0 [deg]C to -25.0
CHSS volume (L) [deg]C ambient [deg]C ambient [deg]C ambient [deg]C ambient
conditions -33.0 [deg]C conditions -33.0 [deg]C conditions -33.0 [deg]C conditions 15.0 [deg]C
to -40.0 [deg]C fuel to -40.0 [deg]C fuel to -40.0 [deg]C fuel to 25.0 [deg]C fuel
delivery temperature delivery temperature delivery temperature delivery temperature
--------------------------------------------------------------------------------------------------------------------------------------------------------
50.................................................. 7.6 19.9 28.5 13.1
100................................................. 7.6 19.9 28.5 7.7
174................................................. 7.6 19.9 19.9 5.2
250................................................. 7.6 19.9 19.9 4.1
300................................................. 7.6 16.5 16.5 3.6
400................................................. 7.6 12.4 12.4 2.9
500................................................. 7.6 9.9 9.9 2.3
600................................................. 7.6 8.3 8.3 2.1
700................................................. 7.1 7.1 7.1 1.9
1,000............................................... 5.0 5.0 5.0 1.4
1,500............................................... 3.3 3.3 3.3 1.0
2,000............................................... 2.5 2.5 2.5 0.7
2,500............................................... 2.0 2.0 2.0 0.5
--------------------------------------------------------------------------------------------------------------------------------------------------------
[[Page 27555]]
(d) The de-fueling rate shall be any rate greater than or equal to
the intended vehicle's maximum fuel-demand rate. Out of the 500
pressure cycles, any 50 pressure cycles are performed using a de-
fueling rate greater than or equal to the maintenance de-fueling rate.
S6.2.4.2. Gas permeation test.
(a) A CHSS is filled with hydrogen gas to any SOC between 100.0
percent and 105.0 percent and placed in a sealed container. The CHSS is
held for any duration between 12 hours and 24 hours at any temperature
between 55.0 [deg]C and 60.0 [deg]C prior to the start of the test.
(b) The permeation from the CHSS shall be determined hourly
throughout the test.
(c) The test shall continue for 500 hours or until the permeation
rate reaches a steady state. Steady state is achieved when at least 3
consecutive leak rates separated by any duration between 12 hours and
48 hours are within 10 percent of the previous rate.
S6.2.5. Test procedures for service terminating performance in
fire. The fire test consists of two stages: a localized fire stage
followed by an engulfing fire stage. The burner configuration for the
fire test is specified in S6.2.5.1. The overall test configuration of
the fire test is verified using a pre-test checkout in accordance with
S6.2.5.2 prior to the fire test of the CHSS. The fire test of the CHSS
is conducted in accordance with S6.2.5.3.
S6.2.5.1. Burner Configuration.
(a) The fuel for the burner shall be liquefied petroleum gas (LPG).
(b) The width of the burner shall be between 450 millimeters and
550 millimeters.
(c) The length of the burner used for the localized fire stage
shall be between 200 millimeters and 300 millimeters.
(d) The length of the burner used for the engulfing fire stage
shall be in accordance with S6.2.5.3(m).
(e) The burner nozzle configuration and installation shall be in
accordance with the Table below. The nozzles shall be installed
uniformly on six rails.
Table 6 to S6.2.5.1
------------------------------------------------------------------------
Item Description
------------------------------------------------------------------------
Nozzle type............................ Liquefied petroleum gas fuel
nozzle with air pre-mix.
LPG orifice in nozzle.................. 0.9 to 1.1 millimeter inner
diameter.
Air ports in nozzle.................... Four (4) holes, 5.8 to 7.0
millimeter inner diameter.
Fuel/Air mixing tube in nozzle......... 9 to 11 millimeter inner
diameter.
Number of rails........................ 6.
Center-to-center spacing of rails...... 100 to 110 millimeter.
Center-to-center nozzle spacing along 45 to 55 millimeter.
the rails.
------------------------------------------------------------------------
S6.2.5.2. Pre-test Checkout.
(a) The pre-test checkout procedure in this section shall be
performed to verify the fire test configuration for the CHSS tested in
accordance with S6.2.5.3.
(b) A pre-test container is a 12-inch Schedule 40 Nominal Pipe Size
steel pipe with end caps. The cylindrical length of the pre-test
container shall be equal to or longer than overall length of the CHSS
to be tested in S6.2.5.3, but no shorter than 0.80 m and no longer than
1.65 m.
(c) The pre-test container shall be mounted over the burner:
(1) At any height between 95 millimeters and 105 millimeters above
the burner;
(2) Such that the nozzles from the two center rails are pointing
toward the bottom center of the pre-test container; and
(3) Such that its position relative to the localized and engulfing
zones of the burner are consistent with the positioning of the CHSS
over the burner in S6.2.5.3.
(d) For outdoor test sites, wind shielding shall be used. The
separation between the pre-test container and the walls of the wind
shields shall be at least 0.5 meters.
(e) Temperatures during the pre-test check-out shall be measured at
least once per second using 3.2 millimeter diameter or less K-type
sheath thermocouples.
(f) The thermocouples shall be located in sets to measure
temperatures along the cylindrical section of the pre-test container.
These thermocouples are secured by straps or other mechanical
attachments within 5 millimeters from the pre-test container surface.
One set of thermocouples consists of:
(1) One thermocouple located at the bottom surface exposed to the
burner flame,
(2) One thermocouple located mid-height along the left side of the
cylindrical surface,
(3) One thermocouple located mid-height along the right side of the
cylindrical surface, and
(4) One thermocouple located at the top surface opposite to the
burner flame.
(g) One set of thermocouples shall be centrally located at the
localized fire zone of the CHSS to be tested as determined in S6.2.5.3.
Two additional sets of thermocouples shall be spread out over the
remaining length of the engulfing fire zone of the CHSS to be tested
that is not part of the localized fire zone of the CHSS to be tested.
(h) Burner monitor thermocouples shall be located between 20
millimeters and 30 millimeters below the bottom surface of the pre-test
container in the same three horizontal locations described in
S6.2.5.2(g). These thermocouples shall be mechanically supported to
prevent movement.
(i) With the localized burner ignited, the LPG flow rate to the
burner shall be set such that the 60-second rolling averages of
individual temperature readings in the localized fire zone shall be in
accordance with the localized stage row in the table below.
(j) With the entire burner ignited, the LPG flow rate to the burner
shall be set such that the 60-second rolling averages of individual
temperature readings shall be in accordance with the engulfing stage
row in the table below.
[[Page 27556]]
Table 7 to S6.2.5.2
----------------------------------------------------------------------------------------------------------------
Temperature range on
Fire stage bottom of pre-test Temperature range on sides Temperature range on top of
container of pre-test container pre-test container
----------------------------------------------------------------------------------------------------------------
Localized.................. 450 [deg]C to 700 less than 750 [deg]C........ less than 300 [deg]C.
[deg]C.
Engulfing.................. Average temperatures of Not applicable.............. Average temperatures of the
the pre-test container pre-test container surface
surface measured at measured at the three top
the three bottom locations shall be at least
locations shall be 100 [deg]C, and when
greater than 600 greater than 750 [deg]C,
[deg]C. shall also be less than the
average temperatures of the
pre-test container surface
measured at the three
bottom locations.
----------------------------------------------------------------------------------------------------------------
S6.2.5.3. CHSS Fire Test.
(a) The CHSS to be fire tested shall include TPRD vent lines.
(b) The CHSS to be fire tested shall be mounted at any height
between 95 millimeters and 105 millimeters above the burner.
(c) CHSS shall be positioned for the localized fire test by
orienting the CHSS such that the distance from the center of the
localized fire exposure to the TPRD(s) and TPRD sense point(s) is at or
near maximum.
(d) When the container is longer than the localized burner, the
localized burner shall not extend beyond either end of the container in
the CHSS.
(e) The CHSS shall be filled with compressed hydrogen gas to any
SOC between 100.0 percent and 105.0 percent.
(f) For outdoor test sites, the same wind shielding shall be used
as was used for S6.2.5.2. The separation between the CHSS and the walls
of the wind shields shall be at least 0.5 meters.
(g) Burner monitor temperatures shall be measured below the bottom
surface of the CHSS in the same positions as specified in S6.2.5.2(h).
(h) The allowable limits for the burner monitor temperatures during
the CHSS fire test shall be established based on the results of the
pre-test checkout as follows:
(1) The minimum value for the burner monitor temperature during the
localized fire stage (TminLOC) shall be calculated by
subtracting 50 [deg]C from the 60-second rolling average of the burner
monitor temperature in the localized fire zone of the pre-test
checkout. If the resultant TminLOC exceeds 600 [deg]C,
TminLOC shall be 600 [deg]C.
(2) The minimum value for the burner monitor temperature during the
engulfing fire stage (TminENG) shall be calculated by
subtracting 50 [deg]C from the 60-second rolling average of the average
of the three burner monitor temperatures during the engulfing fire
stage of the pre-test checkout. If the resultant TminENG
exceeds 800 [deg]C, TminENG shall be 800 [deg]C.
(i) The localized fire stage is initiated by starting the fuel flow
to the localized burner and igniting the burner.
(j) The 10-second rolling average of the burner monitor temperature
in the localized fire zone shall be at least 300 [deg]C within 1 minute
of ignition and for the next 2 minutes.
(k) Within 3 minutes of the igniting the burner, using the same LPG
flow rate as S6.2.5.2(i), the 60-second rolling average of the
localized zone burner monitor temperature shall be greater than
TminLOC as determined in S6.2.5.3(h)(1).
(l) After 10 minutes from igniting the burner, the engulfing fire
stage is initiated.
(m) The engulfing fire zone includes the localized fire zone and
extends in one direction towards the nearest TPRD or TPRD sense point
along the complete length of the container up to a maximum burner
length of 1.65 m.
(n) Within 2 minutes of the initiation of the engulfing fire stage,
using the same LPG flow rate as S6.2.5.2(j), the 60-second rolling
average of the engulfing burner monitor temperature shall be equal or
greater than TminENG as determined in S6.2.5.3(h)(2).
(o) The fire testing continues until the pressure inside the CHSS
is less than or equal to 1.0 MPa or until:
(1) A total test time of 60 minutes for CHSS on vehicles with a
GVWR of 10,000 pounds or less or;
(2) A total test time of 120 minutes for CHSS on vehicles with a
GVWR over 10,000 pounds.
S6.2.6. Test procedures for performance durability of closure
devices.
S6.2.6.1. TPRD performance tests. Unless otherwise specified,
testing is performed with hydrogen gas with a purity of at least 99.97
percent, less than or equal to 5 parts per million of water, and less
or equal to 1 part per million particulate. All tests are performed at
any temperature between 5.0 [deg]C and 35.0 [deg]C unless otherwise
specified.
S6.2.6.1.1. Pressure cycling test. A TPRD undergoes 15,000 internal
pressure cycles at a rate not exceeding 10 cycles per minute. The table
below summarizes the pressure cycles. Any condition within the ranges
specified in the table may be selected for testing.
(a) The first 10 pressure cycles shall be from any low pressure of
between 1.0 MPa and 2.0 MPa to any high pressure between 150.0 percent
NWP and 155.0 percent NWP. These cycles are conducted at any sample
temperature between 85.0 [deg]C to 90.0 [deg]C.
(b) The next 2,240 pressure cycles shall be from any low pressure
between 1.0 MPa and 2.0 MPa to any high pressure of between 125.0
percent NWP and 130.0 percent NWP. These cycles are conducted at any
sample temperature between 85.0 [deg]C to 90.0 [deg]C.
(c) The next 10,000 pressure cycles shall be from any low pressure
of between 1.0 MPa and 2.0 MPa to any high pressure between 125.0
percent NWP and 130.0 percent NWP. These cycles are conducted at a
sample temperature between 5.0 [deg]C to 35.0 [deg]C.
(d) The final 2,750 pressure cycles shall be from any low pressure
between 1.0 MPa and 2.0 MPa to any high pressure between 80.0 percent
NWP and 85.0 percent NWP. These cycles are conducted at any sample
temperature between -45.0 [deg]C to -40.0 [deg]C.
Table 8 to S6.2.6.1.1
----------------------------------------------------------------------------------------------------------------
Sample temperature for
Number of cycles Low pressure High pressure cycles
----------------------------------------------------------------------------------------------------------------
First 10........................... 1.0 MPa to 2.0 MPa.... 150.0% NWP to 155.0% NWP... 85.0 [deg]C to 90.0
[deg]C.
[[Page 27557]]
Next 2,240......................... 1.0 MPa to 2.0 MPa.... 125.0% NWP to 130.0% NWP... 85.0 [deg]C to 90.0
[deg]C.
Next 10,000........................ 1.0 MPa to 2.0 MPa.... 125.0% NWP to 130.0% NWP... 5.0 [deg]C to 35.0
[deg]C.
Final 2,750........................ 1.0 MPa to 2.0 MPa.... 80.0% NWP to 85.0% NWP..... -45.0 [deg]C to -40.0
[deg]C.
----------------------------------------------------------------------------------------------------------------
S6.2.6.1.2. Accelerated life test.
(a) Two TPRDs undergo testing; one at the manufacturer's specified
activation temperature, and one at an accelerated life temperature, TL,
given in [deg]C by the expression:
[GRAPHIC] [TIFF OMITTED] TP17AP24.017
Where b = 273.15 [deg]C, TME is 85 [deg]C, and Tf is the
manufacturer's specified activation temperature in [deg]C.
(b) The TPRDs are placed in an oven or liquid bath maintained
within 5.0 [deg]C of the specified temperature per S6.2.6.1.2(a). The
TPRD inlets are pressurized with hydrogen to any pressure between 125.0
percent NWP and 130.0 percent NWP and time until activation is
measured.
S6.2.6.1.3. Temperature cycling test.
(a) An unpressurized TPRD is placed in a cold liquid bath
maintained at any temperature between -45.0 [deg]C and -40.0 [deg]C.
The TPRD shall remain in the cold bath for any duration not less than 2
hours and not more than 24 hours. The TPRD is removed from the cold
bath and transferred, within five minutes of removal, to a hot liquid
bath maintained at any temperature between 85.0 [deg]C and 90.0 [deg]C.
The TPRD shall remain in the hot bath for any duration not less than 2
hours and not more than 24 hours. The TPRD is removed from the hot bath
and, within five minutes of removal, transferred back into the cold
bath maintained at any temperature between -45.0 [deg]C and -40.0
[deg]C;
(b) Step (a) is repeated until 15 thermal cycles have been
achieved.
(c) The TPRD remains in the cold liquid bath for any duration not
less than 2 and not more than 24 additional hours, then the internal
pressure of the TPRD is cycled with hydrogen gas from any pressure
between 1.0 MPa and 2.0 MPa to any pressure between 80.0 percent NWP
and 85.0 percent NWP for 100 cycles. During cycling, the TPRD remains
in the cold bath and the cold bath is maintained at any temperature
between -45.0 [deg]C and -40.0 [deg]C.
S6.2.6.1.4. Salt corrosion resistance test.
(a) Each closure device is exposed to a combination of cyclic
conditions of salt solution, temperatures, and humidity. One test cycle
is equal to any duration not less than 22 and not more than 26 hours,
and is in accordance with the table below.
Table 9 to S6.2.6.1.4
----------------------------------------------------------------------------------------------------------------
Accelerated cyclic corrosion conditions (1 cycle = 22 hours to 26 hours)
-----------------------------------------------------------------------------------------------------------------
Cycle condition Temperature Relative humidity Cycle duration
----------------------------------------------------------------------------------------------------------------
Ambient stage..................... 22.0 [deg]C to 28.0 35 percent to 55 percent.. 470 minutes to 490
[deg]C. minutes.
----------------------------------------------------------------------------------------------------------------
Transition 55 min to 60 min
----------------------------------------------------------------------------------------------------------------
Humid stage....................... 47.0 [deg]C to 51.0 95 percent to 100 percent. 410 minutes to 430
[deg]C. minutes.
----------------------------------------------------------------------------------------------------------------
Transition 170 minutes to 190 minutes
----------------------------------------------------------------------------------------------------------------
Dry stage......................... 55.0 [deg]C to 65.0 less than 30 percent...... 290 minutes to 310
[deg]C. minutes.
----------------------------------------------------------------------------------------------------------------
(b) The apparatus used for this test shall consist of a fog/
environmental chamber as defined in ISO 6270-2:2017 (incorporated by
reference, see Sec. 571.5), with a suitable water supply conforming to
Type IV requirements in ASTM D1193-06(R2018) (incorporated by
reference, see Sec. 571.5). The chamber shall include a supply of
compressed air and one or more nozzles for fog generation. The nozzle
or nozzles used for the generation of the fog shall be directed or
baffled to minimize any direct impingement on the closure devices.
(c) During ``wet-bottom'' generated humidity cycles, water droplets
shall be visible on the samples.
(d) Steam generated humidity may be used provided the source of
water used in generating the steam is free of corrosion inhibitors and
visible water droplets are formed on the samples to achieve proper
wetness.
(e) The drying stage shall occur in the following environmental
conditions: any temperature not less than 60 [deg]C and not greater
than 65 [deg]C and relative humidity no more than 30 percent with air
circulation.
(f) The impingement force from the salt solution application shall
not remove corrosion and/or damage the coatings of the closure devices.
(g) The complex salt solution in percent by mass shall be as
specified below:
(1) Sodium Chloride: not less than 0.08 and not more than 0.10
percent.
(2) Calcium Chloride: not less than 0.095 and not more than 0.105
percent
(3) Sodium Bicarbonate: not less than 0.07 and not more than 0.08
percent
(4) Sodium Chloride must be reagent grade or food grade. Calcium
Chloride must be reagent grade. Sodium Bicarbonate must be reagent
grade. For the purposes of S6.2.6.1.4, water must meet ASTM D1193-
06(R2018) Type IV requirements (incorporated by reference, see Sec.
571.5).
(5) Either calcium chloride or sodium bicarbonate material must be
dissolved separately in water and added to the solution of the other
materials.
(h) The closure devices shall be installed in accordance with the
[[Page 27558]]
manufacturer's recommended procedure and exposed to the 100 daily
corrosion cycles, with each corrosion cycle in accordance with the
table above.
(i) For each salt mist application, the solution shall be sprayed
as an atomized mist, using the spray apparatus to mist the components
until all areas are thoroughly wet and dripping. Suitable application
techniques include using a plastic bottle, or a siphon spray powered by
oil-free regulated air to spray the test samples. The quantity of spray
applied should be sufficient to visibly rinse away salt accumulation
left from previous sprays. Four salt mist applications shall be applied
during the ambient stage. The first salt mist application occurs at the
beginning of the ambient stage. Each subsequent salt mist application
should be applied not less than 90 and not more than 95 minutes after
the previous application.
(j) The time from ambient to the wet condition shall be any
duration not less than 60 and not more than 65 minutes and the
transition time between wet and dry conditions shall be any duration
not less than 180 and not more than 190 minutes.
S6.2.6.1.5. Vehicle environment test.
(a) The inlet and outlet connections of the closure device are
connected or capped in accordance with the manufacturer's installation
instructions. All external surfaces of the closure device are exposed
to each of the following fluids for any duration between 24 hours and
26 hours. The temperature during exposure shall be any temperature
between 5.0 [deg]C and 35.0 [deg]C. A separate test is performed with
each of the fluids sequentially on a single closure device.
(1) Sulfuric acid: not less than 19 and not more than 21 percent by
volume in water;
(2) Ethanol/gasoline: not less than 10 and not more than 12 percent
by volume ethanol and not less than 88 and not more than 90 percent by
volume gasoline; and
(3) Windshield washer fluid: not less than 50 and not more than 52
percent by volume methanol in water.
(b) The fluids are replenished as needed to ensure complete
exposure for the duration of the test.
(c) After exposure to each fluid, the closure device is wiped off
and rinsed with water.
S6.2.6.1.6. Stress corrosion cracking test.
(a) All components exposed to the atmosphere shall be degreased.
For check valves and shut-off valves, the closure device shall be
disassembled, all components degreased, and then reassembled.
(b) The closure device is continuously exposed to a moist ammonia
air mixture maintained in a glass chamber having a glass cover. The
exposure lasts any duration not less than 240 hours and not more than
242 hours. The aqueous ammonia shall have any specific gravity not less
than 0.940 and not more than 0.941. Aqueous ammonia shall be located at
the bottom of the glass chamber below the sample at any volume not less
than 20 mL and not more than 22 mL of aqueous ammonia per liter of
chamber volume. The bottom of the sample is positioned any distance not
less than 30 and not more than 40 millimeters above the aqueous ammonia
and supported in an inert tray.
(c) The moist ammonia-air mixture is maintained at atmospheric
pressure and any temperature not less than 35 [deg]C and not more than
40 [deg]C.
S6.2.6.1.7. Drop and vibration test.
(a) The TPRD is aligned vertically to any one of the six
orientations covering the opposing directions of three orthogonal axes:
vertical, lateral and longitudinal.
(b) A TPRD is dropped in free fall from any height between 2.00
meters and 2.02 meters onto a smooth concrete surface. The TPRD is
allowed to bounce on the concrete surface after the initial impact.
(c) Any sample with damage from the drop that results in the TPRD
not being able to be tested in accordance with S6.2.6.1.7(d) shall not
proceed to S6.2.6.1.7(d) and shall not be considered a failure of this
test.
(d) Each TPRD dropped in S6.2.6.1.7(a) that did not have damage
that results in the TPRD not being able to be tested is mounted in a
test fixture in accordance with manufacturer's installation
instructions and vibrated for any duration between 30.0 minutes and
35.0 minutes along each of the three orthogonal axes (vertical, lateral
and longitudinal) at the most severe resonant frequency for each axis.
(1) The most severe resonant frequency for each axis is determined
using any acceleration between 1.50 g and 1.60 g and sweeping through a
sinusoidal frequency range from 10 Hz to 500 Hz with any sweep time
between 10.0 minutes and 20.0 minutes. The most severe resonant
frequency is identified by a pronounced increase in vibration
amplitude.
(2) If the resonance frequency is not found, the test shall be
conducted at any frequency between 35 Hz and 45 Hz.
S6.2.6.1.8. Leak test. Unless otherwise specified, the TPRD shall
be thermally conditioned to the ambient temperature condition, then
checked for leakage, then conditioned to the high temperature
condition, then checked for leakage, then conditioned to low
temperature, then checked for leakage.
(a) The TPRD shall be thermally conditioned at test temperatures in
each of the test conditions and held for any duration between 1.0 hour
and 24.0 hours. The TPRD is pressurized with hydrogen at the inlet. The
required test conditions are:
(1) Ambient temperature: condition the TPRD at any temperature
between 5.0 [deg]C and 35.0 [deg]C; test in accordance with
S6.2.6.1.8(b) at any pressure between 1.5 MPa and 2.5 MPa and then at
any pressure between 125.0 percent NWP and 130.0 percent NWP.
(2) High temperature: condition the TPRD at any temperature between
85.0 [deg]C and 90.0 [deg]C; test in accordance with S6.2.6.1.8(b) at
any pressure between 1.5 MPa and 2.5 MPa and then at any pressure
between 125.0 percent NWP and 130.0 percent NWP.
(3) Low temperature: condition the TPRD at any temperature between
-45.0 [deg]C and -40.0 [deg]C; test in accordance with S6.2.6.1.8(b) at
any pressure between 1.5 MPa and 2.5 MPa and then at any pressure
between 100.0 percent NWP and 105.0 percent NWP.
(b) Following conditioning at each of the specified test
temperature ranges, the TPRD is observed for leakage while immersed in
a temperature-controlled liquid at the same specified temperature range
for any duration between 1.0 minutes and 2.0 minutes at each of the
pressures ranges listed above. If no bubbles are observed for the
specified time period, it is not considered a failure. If bubbles are
detected, the leak rate is measured.
S6.2.6.1.9. Bench top activation test.
(a) The test apparatus consists of either a forced air oven or
chimney with air flow. The TPRD is not exposed directly to flame. The
TPRD is mounted in the test apparatus according to the manufacturer's
installation instructions.
(b) The temperature of the oven or chimney is at any temperature
between 600.0 [deg]C and 605.0 [deg]C for any duration between 2
minutes and 62 minutes prior to inserting the TPRD.
(c) Prior to inserting the TPRD, pressurize the TPRD to any
pressure between 1.5 MPa and 2.5 MPa.
(d) The pressurized TPRD is inserted into the oven or chimney, the
temperature within the oven or chimney is maintained at any temperature
between 600.0 [deg]C and 605.0 [deg]C, and the time for the TPRD to
activate is recorded. If the TPRD does not activate within 120 minutes
from the time of insertion into the oven or chimney, the TPRD shall be
considered to have failed the test.
[[Page 27559]]
S6.2.6.1.10. Flow rate test.
(a) At least one new TPRD is tested to establish a baseline flow
rate.
(b) After activation in accordance with S6.2.6.1.9, and without
cleaning, removal of parts, or reconditioning, the TPRD is subjected to
flow testing using hydrogen, air or an inert gas;
(c) Flow rate testing is conducted with any inlet pressure between
1.5 MPa and 2.5 MPa. The outlet is at atmospheric pressure.
(d) Flow rate is measured in units of kilograms per minute with a
precision of at least 2 significant digits.
S6.2.6.2. Check valve and shut-off valve performance tests. Unless
otherwise specified, testing shall be performed with hydrogen gas with
a purity of at least 99.97 percent, less than or equal to 5 parts per
million of water, and less or equal to 1 part per million particulate.
All tests are performed at any temperature between 5.0 [deg]C and 35.0
[deg]C unless otherwise specified.
S6.2.6.2.1. Hydrostatic strength test.
(a) The outlet opening is plugged and valve seats or internal
blocks are made to assume the open position.
(b) Any hydrostatic pressure between 250.0 percent NWP and 255.0
percent NWP is applied using water to the valve inlet for any duration
between 180.0 seconds and 185.0 seconds. The unit is examined to ensure
that burst has not occurred.
(c) The hydrostatic pressure is then increased at a rate of less
than or equal to 1.4 MPa/sec until component failure. The hydrostatic
pressure at failure is recorded.
S6.2.6.2.2. Leak test.
Each unit shall be thermally conditioned to the ambient temperature
condition, then checked for leakage, then conditioned to the high
temperature condition, then checked for leakage, then conditioned to
low temperature, then checked for leakage.
(a) Each unit shall be pressurized to any pressure between 2.0 MPa
and 3.0 MPa and held for any duration between 1.0 hours and 24.0 hours
in the specified temperature range before testing. The outlet opening
is plugged. The test conditions are:
(1) Ambient temperature: condition the unit at any temperature
between 5.0 [deg]C and 35.0 [deg]C; test at any pressure between 1.5
MPa and 2.5 MPa and at any pressure between 125.0 percent NWP and 130.0
percent NWP.
(2) High temperature: condition the unit at any temperature between
85.0 [deg]C and 90.0 [deg]C; test at any pressure between 1.5 MPa and
2.5 MPa and any pressure between 125.0 percent NWP and 130.0 percent
NWP.
(3) Low temperature: condition the unit at any temperature between
-45.0 [deg]C and -40.0 [deg]C; test at any pressure between 1.5 MPa and
2.5 MPa and any pressure between 100.0 percent NWP and 105.0 percent
NWP.
(b) While within the specified temperature and pressure range, the
unit is observed for leakage while immersed in a temperature-controlled
liquid held within the same specified temperature range as the test
condition for any duration between 1.0 minutes and 2.0 minutes at each
of the test pressures. If no bubbles are observed for the specified
time period, the sample passes the leak test. If bubbles are detected,
the leak rate is measured.
S6.2.6.2.3. Extreme temperature pressure cycling test.
(a) The valve unit is connected to a test fixture.
(b) For a check valve, the pressure is applied in six incremental
pulses to the check valve inlet with the outlet closed. The pressure is
then vented from the check valve inlet. The pressure is lowered on the
check valve outlet side to any pressure between 55.0 percent NWP and
60.0 percent NWP prior to the next cycle;
(c) For a shut-off valve, the specified pressure is applied through
the inlet port. The shut-off valve is then energized to open the valve
and the pressure is reduced to any pressure less than 50 percent of the
specified pressure range. The shut-off valve shall then be de-energized
to close the valve prior to the next cycle.
S6.2.6.2.4. Chatter flow test. The valve is subjected to between
24.0 hours and 26.0 hours of chatter flow at a flow rate that causes
the most valve flutter.
S6.2.6.2.5. Electrical Tests. This section applies to shut-off
valves only.
(a) The solenoid valve is connected to a variable DC voltage
source, and the solenoid valve is operated as follows:
(1) Held for any duration between 60.0 and 65.0 minutes at any
voltage between 0.50 V and 1.5 times the rated voltage.
(2) The voltage is increased to any voltage between 0.5 V to two
times the rated voltage, or between 60.0 V and 60.5 V, whichever is
less, and held for any duration between 60.0 seconds and 70.0 seconds.
(b) Any voltage between 1,000.0 V DC and 1,010.0 V DC is applied
between the power conductor and the component casing for any duration
between 2.0 seconds to 4.0 seconds.
S6.2.6.2.6. Vibration test.
(a) The valve is pressurized with hydrogen to any pressure between
100.0 percent NWP and 105.0 percent NWP, sealed at both ends, and
vibrated for any duration between 30.0 and 35.0 minutes along each of
the three orthogonal axes (vertical, lateral and longitudinal) at the
most severe resonant frequencies.
(b) The most severe resonant frequencies are determined using any
acceleration between 1.50 g and 1.60 g and sweeping through a
sinusoidal frequency range from 10 Hz to 500 Hz with any sweep time
between 10.0 minutes and 20.0 minutes. The resonance frequency is
identified by a pronounced increase in vibration amplitude.
(c) If the resonance frequency is not found, the test shall be
conducted at any frequency between 35 Hz and 45 Hz.
BILLING CODE 4910-59-P
[[Page 27560]]
[GRAPHIC] [TIFF OMITTED] TP17AP24.018
Figure 1. Performance Durability Test; (for Illustration Purposes Only)
[GRAPHIC] [TIFF OMITTED] TP17AP24.019
Figure 2. The Four Drop Orientations; (for Illustration Purposes Only)
[[Page 27561]]
[GRAPHIC] [TIFF OMITTED] TP17AP24.020
Figure 3. Locations of Surface Damage for S6.2.3.3(a) and Pendulum
Impacts for S6.2.3.3(b); (for Illustration Purposes Only)
Authority: 49 U.S.C. 322, 30111, 30115, 30117, 30122 and 30166;
delegation of authority at 49 CFR 1.95 and 501.5.
Sophie Shulman,
Deputy Administrator.
[FR Doc. 2024-07116 Filed 4-16-24; 8:45 am]
BILLING CODE 4910-59-C