[Federal Register Volume 63, Number 232 (Thursday, December 3, 1998)]
[Rules and Regulations]
[Pages 66762-66766]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 98-31773]


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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. NHTSA-98-4807]
RIN 2127-AF51


Federal Motor Vehicle Safety Standards; Compressed Natural Gas 
Fuel Containers

AGENCY: National Highway Traffic Safety Administration (NHTSA), 
Department of Transportation (DOT).

ACTION: Final rule.

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SUMMARY: This final rule deletes the material and manufacturing process 
requirements in the standard on compressed natural gas fuel container 
integrity. The agency believes that this amendment will facilitate 
technological innovation, without adversely affecting safety.

DATES: This final rule is effective January 4, 1999. Petitions for 
Reconsideration must be received by January 19, 1999.

ADDRESSES: Petitions should refer to the docket number of this rule and 
be submitted to: Administrator, National Highway Traffic Safety 
Administration, 400 7th Street, SW, Washington, DC 20590.

FOR FURTHER INFORMATION CONTACT: For non-legal issues: Mr. Charles 
Hott, NPS-12, Office of Crashworthiness Standards, National Highway 
Traffic Safety Administration, 400 Seventh Street, S.W., Washington, 
D.C. 20590 (Telephone 202-366-0247) (FAX 202-366-4329).
    For legal issues: Ms. Nicole H. Fradette, NCC-20, Rulemaking 
Division, Office of Chief Counsel, National Highway Traffic Safety 
Administration, 400 Seventh Street, SW., Washington, D.C. 20590 
(Telephone 202-366-2992) (FAX 202-366-3820).

SUPPLEMENTARY INFORMATION:

I. Background

    Federal Motor Vehicle Safety Standard No. 304, Compressed natural 
gas fuel container integrity, serves to reduce the risk of deaths and 
injuries occurring from fires resulting from fuel leakage during and 
after motor vehicle crashes. The Standard was patterned after the 
American National Standards Institute's (ANSI's) voluntary industry 
standard known as ANSI/NGV2 and developed by the Natural Gas Vehicle 
Coalition (NGVC). Standard No. 304 specifies detailed material and 
manufacturing process requirements for different types of CNG 
containers, including those made with aluminum alloys. The Standard 
also specifies burst, bonfire, and pressure cycling tests for the 
purpose of ensuring the durability, initial strength, and venting of 
CNG containers.

     The burst test evaluates a container's initial strength 
and resistance to degradation over time by specifying, for each type of 
container, a unique safety factor for determining the internal 
hydrostatic pressure that the container must withstand during the burst 
test. This requirement helps to ensure that a container's design and 
selected material are sufficiently strong over the life of the 
container.
     The bonfire test evaluates a container's pressure relief 
characteristics when pressure builds up in a container, primarily due 
to an increase in temperature.
     Finally, the pressure cycling test evaluates a container's 
durability by requiring a container to withstand without leakage, 
18,000 cycles of pressurization and depressurization. This requirement 
helps to ensure that a CNG container is capable of sustaining the 
cycling loads imposed on the container during refueling over its entire 
service life.

In addition, the Standard specifies labeling requirements for CNG fuel 
containers.
    Standard No. 304 specifies certain material and manufacturing 
characteristics for aluminum containers using alloy 6010 and alloy 
6061, based on the specifications set forth in ANSI/NGV2. The material 
characteristics specify the percentage of various elements, including 
magnesium, silicon, copper, and manganese. On November 24, 1995, NHTSA 
issued a final rule amending the labeling and the bonfire test 
requirements in Standard No. 304, Compressed Natural Gas fuel container 
integrity. In the final rule, the agency decided to defer consideration 
of two

[[Page 66763]]

rulemaking petitions to add additional aluminum alloys to Standard No. 
304, until the new version of the ANSI/NGV industry standard was 
issued. Northwest Aluminum Association requested that the standard be 
amended to add 6069 aluminum alloy, and Luxfer requested the addition 
of 7032 aluminum alloy. In explaining its decision to defer 
consideration of the petitions, the agency noted that the new ANSI/NGV2 
industry standard may not specify CNG fuel container material and may 
be more performance-oriented than the current version, thereby allowing 
manufacturers more flexibility to improve container design with respect 
to cost and performance. The agency also noted that adopting some of 
the new provisions of the revised voluntary industry standard may 
eliminate the need to amend the standard to allow the use of two new 
aluminum alloys in CNG containers.

II. Summary of NPRM

    In a May 30, 1997 notice of proposed rulemaking (NPRM), NHTSA 
proposed amending Standard No. 304 to eliminate the Standard's detailed 
material and manufacturing process requirements. The agency explained 
it had tentatively determined that CNG fuel container manufacturers 
should be allowed to use materials other than those materials currently 
listed in the standard. NHTSA explained that such an amendment would 
provide manufacturers with the flexibility to design lighter weight, 
higher capacity fuel containers using the latest innovations, without 
having to petition the agency to amend the standard each time a new 
material or manufacturing process is developed.
    The agency also noted that the proposal to remove the material and 
manufacturing requirements was consistent with the proposed revision to 
ANSI/NGV, which removed many of the design restrictions that were in 
the 1992 version of NGV2 on which Standard No. 304 was initially 
modeled. In October 1996, the ANSI committee working on the revised 
standard completed its revisions and sent the revised document to its 
members for review. The proposed revision of ANSI/NGV2 removed many of 
the detailed material and manufacturing restrictions, but retained the 
impurity limits for certain materials. NHTSA explained that it 
understood that although the industry had not reached a consensus with 
respect to certain environment testing procedures, the industry had 
tentatively agreed to eliminate the material and manufacturing 
requirements.
    NHTSA also stated it believed that eliminating the material and 
manufacturing process requirements would have no detrimental affect on 
safety. The agency explained that Standard No. 304's performance 
requirements, including those requirements that evaluate initial 
strength and resistance to degradation over time, would still apply to 
CNG containers. Thus, CNG container manufacturers would have to comply 
with the standard's pressure cycling, burst, and bonfire tests. NHTSA 
further explained that such containers would be subject to recall if 
they failed for any reason, including the degradation of material.
    NHTSA proposed deleting the following sections from the standard:

     Section S5.2 Material designations. This section 
specifies the material requirements for the various types of CNG 
fuel containers.
     Section S5.3 Manufacturing processes for composite 
containers. This section specifies the manufacturing process for 
each type of composite CNG fuel container.
     Section S5.4 Wall thickness and Section S5.5 Composite 
Reinforcement for Type 2, Type 3, and Type 4 containers. These 
sections contain the design criteria for specifying the wall 
thicknesses and stresses for each type of CNG fuel container. These 
sections also specify procedures for designing CNG fuel container 
walls along with the theoretical formula for calculating maximum 
wall stress.
     Section S5.6 Thermal Treatment, and S5.7 Yield 
Strength. These sections contain detailed manufacturing process 
requirements for chrome-moly and carbon-boron steels, including 
specifying the temper temperatures for each steel.

    In June 1998, ANSI published the new ANSI/NGV2 industry standard. 
The new standard is similar to the proposed standard in that much of 
the design restrictive language has been removed. ANSI/NGV2 now 
specifies that the material composition for steels should be known and 
defined by at least the contents of certain elements such as carbon, 
manganese, aluminum and the other alloying elements that are added to 
enhance the material properties. For aluminum, ANSI/NGV2 simply states 
that it should be in line with the Aluminum Association's practice and 
the 6xxx series with yield strengths above 250 MPa should not be used. 
It also specifies impurity limits for steels and aluminums.

III. Summary of Comments

    Eight comments were submitted in response to the NPRM from the 
following companies/organizations: Chrysler Corporation (Chrysler), 
General Motors (GM), Gas Technology Canada (GTC), the Natural Gas 
Vehicle Coalition (NGVC), Lincoln Composites (Lincoln), Pressed Steel 
Tank Co. (PST), Structural Composites Industries (SCI), and New York 
City Transit (NY Transit).
    Chrysler, GM, and GTC supported the proposed rule. Chrysler and GM 
stated that deleting the material and manufacturing process 
requirements would facilitate technological innovation without reducing 
safety. GTC stated that CNG containers sold in Canada that are 
manufactured from at least four material types that are not offered for 
sale in the United States have performed well in service. GTC 
cautioned, however, that additional performance tests might be needed 
to prevent in-service failures. Chrysler also commented that S7.2.2 of 
Standard No. 304 refers to S5.5.1, which is proposed for deletion, and 
suggested that S7.2.2 be revised accordingly.
    NGVC and Lincoln also supported NHTSA's efforts to facilitate 
technological innovation, but were concerned that deletion of the 
material performance requirements without including the additional 
tests from the draft revision of ANSI/NGV2 industry standard, could 
lead to a serious safety problem. The latest draft standard, while 
deleting many of the specific material design requirements, includes 
the following three enhanced material performance test requirements:

    1. Sulfide stress cracking resistance of high strength steels 
using the methods of NACE Standard TM0177-90;
    2. Sustained load cracking for aluminum alloys in accordance 
with Annex D of ISO/DIS 7866; and
    3. Intercrystalline corrosion and stress corrosion tests for 
aluminum alloys in accordance with Annex A of ISO/DIS 7866.

NGVC stated that these tests are needed to ensure the integrity of the 
materials that were previously excluded by the standard while Lincoln 
argued that these requirements were needed to reduce the risk of in-
service leakage or rupture and inadequate shear strength of resins over 
the life of the CNG container. NGVC argued that NHTSA should retain 
Standard No. 304's current requirements until the industry's revision 
of ANSI/NGV2 is complete. Lincoln argued that NHTSA should simply amend 
Standard No. 304 to include the materials requested by Northwest 
Aluminum Association and Luxfer, aluminum alloys 6069 and 7032 
respectively, rather than delete the material and manufacturing 
requirements.
    PST supported removing the thermal treatment, wall thickness, and 
manufacturing process requirements from the standard, but argued that 
the standard should continue to limit materials to specific alloys and 
reinforcing fibers. PST argued that most

[[Page 66764]]

CNG container failures occurred because the CNG manufacturer used 
materials with insufficient toughness, damage tolerance, long term 
stability and environmental resistance. PST argued that a single safety 
factor cannot protect against such material deficiencies. PST further 
claimed that high-strength aluminum alloys were originally excluded 
from Standard No. 304 because of their susceptibility to sustained load 
cracking (SLC) and stress corrosion cracking (SCC). PST noted that the 
draft ISO/DIS 7866 standard, which is included in the proposed revision 
to NGV2, includes material tests intended to exclude SLC and SCC 
susceptible materials. PST argued that NHTSA should evaluate the SLC, 
SCC and accelerated stress rupture tests, and amend the standard to 
include these tests, as well as a resistance to impact requirement. 
Finally, PST asserted that the agency must address the potential 
failure modes of organic reinforcing fibers, stainless steels, copper 
alloys and other materials, if the agency is going to permit the use of 
these materials. PST stated that the time and the cost involved with 
developing adequate performance tests for all of these materials was 
high and any resulting economic benefits questionable.
    SCI opposed the proposed rule and argued that Standard No. 304's 
current performance tests are insufficient to prevent time related 
failures resulting from corrosion, stress rupture, viscoelastic 
yielding, and aging. SCI stated that the small sample size and short 
time period involved with testing made it too difficult and complex to 
test for such time related failures. SCI also argued that the history 
of CNG fuel containers demonstrated that the standard's current test 
requirements were insufficient to prevent catastrophic failures, such 
as battery fluid field failures occurring from in-service abuse or 
impact damage from roadway debris.
    While New York City Transit stated that it did not oppose the 
proposed changes, it did express concern that Standard No. 304 is 
insufficient to prevent CNG container failures. NYCT's concern is based 
on the fact that nearly six percent of one model of CNG fuel containers 
produced by a particular manufacturer has experienced failures after 
only a few years in service. NYCT stated that 31 of its CNG transit 
buses were equipped with these containers and that it was unable to 
retrofit the containers because the manufacturer is out of business.

IV. Agency Decision

    The agency is deleting the material and manufacturing process 
requirements from Standard No. 304 and amending S7.2.1 and S7.2.2 of 
the standard to eliminate any reference to those requirements. NHTSA 
believes that the deletion of these requirements will facilitate 
technological innovation without having an adverse affect on safety.
    For the following reasons, the agency is not replacing the deleted 
requirements with other requirements, as suggested by some commenters. 
First, the agency has concluded that Standard No. 304's current testing 
requirements--pressure cycling, burst, and bonfire--are sufficient to 
ensure an appropriate level of safety for CNG fuel containers. The 
tests indirectly ensure that the containers are manufactured using 
appropriate materials and wall thicknesses. The agency believes, 
therefore, that the Standard's design and material requirement are 
unnecessary and restrict the ability of manufacturers to use the latest 
technology in manufacturing CNG fuel containers.
    Second, NHTSA has no evidence indicating the existence of a safety 
problem that would be addressed by including additional tests, such as 
those contained in the proposed NGV2 revision, in the 
Standard.1 NHTSA knows of six CNG fuel container ruptures 
that have occurred since 1993. According to a safety bulletin published 
by the Gas Research Institute in October 1996, all six ruptures could 
have been prevented if appropriate precautions had been taken. 
Mishandling, misuse, and improper placement and maintenance of the CNG 
fuel containers caused the failures. In four of the cases, the CNG fuel 
container did not have a shield surrounding it to protect it from 
impact damage. A vehicle design change would address this problem. In 
the other two cases, the CNG fuel containers ruptured after prolonged 
exposure to acidic fluids. In those two cases, the shielding 
surrounding the CNG fuel containers lacked adequate drainage. 
Consequently, acidic fluids accumulated in the area beneath the 
containers and damaged the CNG fuel containers. NHTSA believes that the 
proper placement and shielding of the CNG fuel containers along with a 
periodic inspection of the container, as directed by the CNG fuel 
containers label, could have prevented these failures. None of the 
additional testing provisions in the new ANSI/NGV2 industry standard 
would have prevented these cylinder failures. The agency, therefore, 
does not believe that inclusion of the additional tests is necessary.
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    \1\ The agency notes that while several of the commenters stated 
that NHTSA should amend Standard No. 304 to require additional tests 
to prevent in-service failures of CNG containers, none provided 
evidence indicating the existence of a safety problem with in-
service failures that was not addressed by the Standard's current 
tests and would be addressed by the inclusion of additional tests.
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    Finally, NHTSA agrees with the comments of SCI that testing for 
such time related failures as corrosion, stress rupture, viscoelastic 
yielding, and aging may be impracticable due to the small sample size 
and short time period involved with testing. Thus, even if there were a 
safety problem that could not be addressed by the standard's current 
testing requirements, NHTSA believes it would be inappropriate to 
require these particular tests given the current uncertainty concerning 
their effectiveness.
    The agency does not believe that manufacturers will fail to 
exercise care in selecting appropriate materials to manufacture CNG 
containers. NHTSA does, however, stress that any CNG fuel containers 
that might be found in the future to have an unanticipated safety 
related failure would be subject to recall. NHTSA, therefore, will 
continue to monitor the performance of CNG fuel containers closely and 
should a safety problem arise, NHTSA will take the appropriate 
regulatory or enforcement action.
    While NHTSA understands NYCT's concern that one particular model of 
CNG containers leaked an excessive amount of gas after only a few years 
in service, NHTSA notes that a defective manufacturing process, unique 
to the particular manufacturer, rather than a defective design, was the 
cause of these failures. No other CNG containers experienced such 
failures.2 Neither the Standard as currently drafted nor as 
revised by this notice would have prevented the failure of this 
particular model of CNG fuel container.
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    \2\ The agency notes that the manufacturer of these six 
containers went out of business and that other transit fleets who 
had purchased the faulty containers retrofitted their buses with new 
CNG containers.
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V. Effective Date

    The statute under which the agency conducts its vehicle safety 
rulemaking requires that each order (i.e., final rule) take effect no 
sooner than 180 days from the date the order is issued unless good 
cause is shown that an earlier effective date is in the public 
interest. In the NPRM, NHTSA tentatively concluded that there was good 
cause not to provide the 180 day lead time since the proposed amendment 
would delete certain requirements and have no mandatory effect on 
manufacturers.

[[Page 66765]]

NHTSA, therefore, proposed a 30 day effective date and sought comment 
on whether that date was appropriate or whether more lead time was 
necessary. No comments were submitted opposing the proposed effective 
date. NHTSA has, therefore, determined that there is good cause for an 
effective date 30 days after publication of the final rule.

VI. Rulemaking Analyses and Notices

Executive Order 12866 and DOT Regulatory Policies and Procedures

    This final rule was reviewed under E.O. 12866. NHTSA has analyzed 
this rule and determined that it is not ``significant'' within the 
meaning of the Department of Transportation's regulatory policies and 
procedures. This final rule allows manufacturers to use materials other 
than those materials currently listed in Standard No. 304. This 
rulemaking action will provide manufacturers with the flexibility to 
design lighter weight, higher capacity fuel containers. The performance 
requirements in Standard No. 304 are met by CNG fuel container 
manufacturers, who produce and test containers in accordance with ANSI/
NGV2. A full regulatory evaluation is not required because the rule 
will not significantly affect costs or benefits.

Regulatory Flexibility Act

    NHTSA has considered the effects of this rulemaking action under 
the Regulatory Flexibility Act (5 U.S.C. 601 et seq.). I hereby certify 
that the final rule would not have a significant economic impact on a 
substantial number of small entities.
    The following is NHTSA's statement providing the factual basis for 
the certification (5 U.S.C. 605(b)). The final rule primarily affects 
manufacturers of CNG containers. The Small Business Administration's 
size standards (13 CFR Part 121) are organized according to Standard 
Industrial Classification Codes (SIC). SIC Code 3714 ``Motor Vehicle 
Parts and Accessories'' has a small business size standard of 750 
employees or fewer.
    The agency believes that this final rule will not have a 
significant economic impact on a substantial number of small businesses 
because the manufacturers of CNG containers currently manufacture 
according to the ANSI/NGV2 industry standard, and this rulemaking is 
consistent with those requirements. NHTSA has stated that this final 
rule deletes certain requirements and does not require any CNG 
container design changes. The changes will not affect the cost of new 
CNG containers.

Paperwork Reduction Act

    NHTSA has analyzed this rule under the Paperwork Reduction Act of 
1995 (Pub. L. 104-13) and determined that it will not impose any 
information collection requirements as that term is defined by the 
Office of Management and Budget (OMB) in 5 CFR part 1320.

National Environmental Policy Act

    Finally, the agency has considered the environmental implications 
of this final rule in accordance with the National Environmental Policy 
Act of 1969 and determined that it will not significantly affect the 
human environment.

The Unfunded Mandates Reform Act

    The Unfunded Mandates Reform Act of 1995 (Pub. L. 104-4) requires 
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. Annual expenditures from this final rule will 
not exceed the $100 million threshold.

Executive Order 12612 (Federalism)

    The agency has analyzed this rule in accordance with the principles 
and criteria set forth in Executive Order 12612. NHTSA has determined 
that this rule will not have sufficient federalism implications to 
warrant the preparation of a Federalism Assessment.

Civil Justice Reform

    This rule has no retroactive effect. NHTSA is not aware of any 
state law that would be preempted by this rule. This rule does not 
repeal any existing Federal law or regulation. It modifies existing law 
only to the extent that it deletes the material and manufacturing 
process requirements in Standard No. 304, Compressed natural gas fuel 
container integrity. This rule does not require submission of a 
petition for reconsideration or the initiation of other administrative 
proceedings before a party may file suit in court.

List of Subjects in 49 CFR Part 571

    Motor vehicle safety, Reporting and recordkeeping requirements, 
Tires.
    In consideration of the foregoing, the agency is amending part 571 
of title 49 of the Code of Federal Regulations as follows:

PART 571--FEDERAL MOTOR VEHICLE SAFETY STANDARDS

    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 1.50

    2. Section 571.304 is amended by removing S5.2 through S5.7.3 and 
by revising S7.2, S7.2.1, and S7.2.2 to read as follows:


Sec. 571.304  Standard No. 304; Compressed natural gas fuel container 
integrity.

* * * * *
    S7.2  Hydrostatic burst test.
    S7.2.1  Each Type 1 CNG fuel container shall not leak when 
subjected to burst pressure and tested in accordance with S8.2. Burst 
pressure shall not be less than 2.25 times the service pressure for 
non-welded containers and shall not be less than 3.5 times the service 
pressure for welded containers.
    S7.2.2  Each Type 2, Type 3, or Type 4 CNG fuel container shall not 
leak when subjected to burst pressure and tested in accordance with 
S8.2. Burst pressure shall not be less than the value specified in 
Table 1 times the service pressure, as follows:

                         Table 1.--Stress Ratios
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                Material                   Type 2     Type 3     Type 4
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E-Glass.................................      2.65       3.5        3.5
S-Glass.................................      2.65       3.5        3.5
Aramid..................................      2.25       3.0        3.0
Carbon..................................      2.25       2.25       2.25
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[[Page 66766]]

    Issued on: November 23, 1998.
Ricardo Martinez,
Administrator.
[FR Doc. 98-31773 Filed 12-2-98; 8:45 am]
BILLING CODE 4910-59-U