|
|---|
|
Federal Motor Vehicle Safety Standards; Fuel System Integrity of Compressed Natural Gas Vehicles Publication: Federal Register Agency: National Highway Traffic Safety Administration Byline: Ricardo Martinez Date: 10 January 1995 Subject: American Government  • Safety
Topic: Federal Motor Vehicle Safety Standards |
[Federal Register Volume 60, Number 6 (Tuesday, January 10, 1995)]
[Rules and Regulations]
[Pages 2539-2543]
From the Federal Register Online via the Government Publishing Office [www.gpo.gov]
[FR Doc No: 95-464]
=======================================================================
-----------------------------------------------------------------------
DEPARTMENT OF TRANSPORTATION
National Highway Traffic Safety Administration
49 CFR Part 571
[Docket No. 93-02; Notice 07]
RIN 2127-AF42
Federal Motor Vehicle Safety Standards; Fuel System Integrity of
Compressed Natural Gas Vehicles
AGENCY: National Highway Traffic Safety Administration (NHTSA),
Department of Transportation (DOT).
ACTION: Final rule; response to petitions for reconsideration.
-----------------------------------------------------------------------
SUMMARY: On April 25, 1994, NHTSA published a new Federal motor vehicle
safety standard, Standard No. 303, Fuel System Integrity of Compressed
Natural Gas Vehicles. The standard limits the amount of allowable CNG
leakage after a crash test by limiting the post-crash pressure drop of
the fuel system. Ford Motor Company, Chrysler Corporation, and the
American Automobile Manufacturers Association, submitted petitions for
reconsideration of the final rule. The issues raised in the petitions
include the allowable pressure drop limit, submitted by Ford and
Chrysler, and other pre-crash test conditions and procedures, submitted
by AAMA. NHTSA is denying the petitions of Ford and Chrysler concerning
pressure drop limit, and denying in part and granting in part the
requests by AAMA.
DATES: Effective Date: The amendments made in this rule are effective
September 1, 1995.
Petitions for Reconsideration: Any petition for reconsideration of
this rule must be received by NHTSA no later than February 9, 1995.
ADDRESSES: Petitions for reconsideration should refer to the docket and
notice number of this notice and be submitted to: Administrator,
National Highway Traffic Safety Administration, 400 Seventh Street, SW,
Washington, DC 20590.
[[Page 2540]] FOR FURTHER INFORMATION CONTACT:
Mr. Gary R. Woodford, NRM-01.01, Special Projects Staff, Office of
Rulemaking, National Highway Traffic Safety Administration, 400 Seventh
Street, SW, Washington, DC 20590 (202-366-4931).
SUPPLEMENTARY INFORMATION: On April 25, 1994, NHTSA published a new
Federal motor vehicle safety standard (FMVSS) for the fuel system
integrity of compressed natural gas (CNG) vehicles (59 FR 19648). The
new standard, FMVSS No. 303, Fuel System Integrity of Compressed
Natural Gas Vehicles, limits the amount of allowable CNG leakage after
a crash test. This is done by placing a limit on the post-crash
pressure drop of the fuel system. Vehicles with a gross vehicle weight
rating (GVWR) of 10,000 pounds or less are subject to front, rear, and
side impact crash tests. Schoolbuses with a GVWR greater than 10,000
pounds are subject to moving contoured barrier crash at any point and
angle on the vehicle. The purpose of the new standard, which becomes
effective September 1, 1995, is to reduce deaths and injuries caused by
fires resulting from fuel leakage during and after crashes involving
CNG vehicles.
Ford Motor Company (Ford), Chrysler Corporation (Chrysler), and the
American Automobile Manufacturers Association (AAMA) submitted
petitions for reconsideration of the final rule. The issues raised in
the petitions include the post-crash pressure drop limit of the fuel
system, and procedures and test conditions prior to crash testing. A
discussion of each issue and the agency's response follows.
Pressure Drop Limit
The final rule, as specified in S5.2(a), sets the allowable
pressure drop in the CNG fuel system one hour after any crash test as
follows:
(1) 1062 kPa (154 psi), or
(2) 895 (T/VFS), whichever is higher.
T is the average temperature of the test gas in degrees Kelvin,
stabilized to ambient temperature before testing. Average temperature T
is determined by measuring ambient temperature at the start of the
test, and then every 15 minutes until the test time of 60 minutes is
completed. The sum of the five ambient temperatures is then divided by
five to yield average temperature T. S7.1.7 of the final rule specifies
that ambient temperature is not to vary more than 5.6 deg.C (10
deg.F) during the course of the test. VFS is the internal volume
of the high pressure portion of the vehicle fuel system.
The other allowable pressure drop, 1062 kPa (154 psi), represents
the smallest pressure drop measurable using existing pressure drop
measurement technology is test gas temperature varies no more than 5.6
deg.C (10 deg.F). The agency established this level based on comments
from AAMA and others in response to the agency's January 21, 1993
notice of proposed rulemaking (NPRM) (58 FR 5323). In its comments on
that notice, AAMA stated that using a state-of-the-art capacitance type
pressure transducer could still result in pressure drop measurement
error of 106.1 kPa (15.4 psi) if test gas
temperature varied no more than 5.6 deg.C (10
deg.F). This is due to the cumulative errors attributable to pressure
transducer accuracy, thermal zero shift, thermal coefficient
sensitivity, and analogue-digital conversion. These factors, coupled
with the accepted engineering practice that measurement error should
not exceed ten percent of the value being measured, led to the
conclusion that pressure drops less than 1062 kPa (154 psi) should not
be measured.
The above pressure drop established in the final rule represents
the maximum allowable CNG leakage, 895 (T/VFS), within the limits
of current pressure drop measurement technology, 1062 kPa (154 psi).
Both Ford and Chrysler petitioned the agency for reconsideration of
the above pressure drop limits in S5.2(a). Ford stated that it believes
the agency erred by disregarding certain information provided by AAMA
in its response to the January 1993 NPRM (58 FR 5323). Specifically,
AAMA stated that ``* * * a 10 deg.F change in the temperature of the
test gas would result in a 60 psi change in the pressure of the test
gas.'' Noting that the final rule allows the ambient temperature to
vary as much as 5.6 deg.C (10 deg.F) during the test, Ford stated
that a 10 deg.F drop in temperature could result in a 60 psi pressure
drop even with zero leakage. Thus, according to Ford, the pressure drop
limits in the final rule are, in effect, reduced by 60 psi when the
ambient temperature drops 10 deg.F and increased by 60 psi when the
ambient temperature increases 10 deg.F during the test. Ford asserted
that the pressure drop limits are, therefore, not reasonable,
practicable, or stated in objective terms as required by statute,
because they present arbitrary limits that vary depending on whether
ambient temperature decreases or increases. Ford further stated that an
appropriate corrective action would be to amend S5.2(a) so that it
states, ``For all vehicles, the pressure drop in the high pressure
portion of the fuel system, excluding pressure changes due to changes
in the temperature of the test gas, expressed in * * *.'' Ford's
recommended language is underlined. Thus, Ford's alternative would
eliminate that component of any pressure drop which is due to test gas
temperature change.
Chrysler, in its petition, provided an almost identical rationale
to that of Ford, stating that the pressure drop limits specified in the
final rule do not accurately measure fuel leakage when the internal
temperature of the gas causes change to the pressure within the fuel
system. However, Chrysler's suggested corrective action differs from
that of Ford. Chrysler requested that the agency amend the pressure
drop limits in the final rule to incorporate the 60 psi adjustment
needed to compensate for the possible change in gas temperature. Under
Chrysler's request, the amended pressure drop limits in S5.2(a) would
be:
(1) 1476 kPa (214 psi), or
(2) 895 (T/VFS) + 414 kPa (60 psi), whichever is higher.
Chrysler stated that ``[t]his would provide the needed compensation
without the added difficulty of measuring gas temperature within the
high pressure fuel system, which is difficult, impracticable, and risks
compromising the fuel system integrity.''
After reviewing Ford's and Chrysler's petitions for reconsideration
about permissible pressure drop, NHTSA has determined that the
requested modifications to S5.2(a) would be inappropriate. NHTSA
continues to believe that the pressure drop limits and test procedure
established in the final rule are the most appropriate and feasible,
and that they provide a relatively simple and accurate method to
determine CNG fuel leakage. The agency believes that under real world
test conditions, any variation in test gas temperature will not
significantly affect test results.
NHTSA notes that because CNG is a gas, and not a liquid, measuring
a safe level of allowable leakage after a crash test is much more
complex than measuring similar levels for liquid fuels. This is because
of the relationship between the temperature and pressure of a gas. The
two are directly proportional. A change in either, pressure or
temperature, directly affects the other.
In arriving at the allowable pressure drop limit and test procedure
established in the final rule, NHTSA addressed the issue of temperature
and pressure, along with other related issues [[Page 2541]] raised by
commenters on the January 1993 NPRM. These included whether to measure
test gas temperature during the 60-minute period following barrier
impact, whether to specify an ambient test temperature, the accuracy of
available pressure drop measurement technology, and the time period
over which pressure drop is measured. These, along with commenters'
concerns, presented complex, and, in some cases, competing issues to
resolve. There were a variety of possible solutions, some more feasible
than others, to the problem of measuring CNG fuel system leakage.
Contrary to the assertion made by Ford in its petition, the agency
considered the information provided by AAMA about the effect of
temperature on pressure. That information is specifically referenced in
the preamble to the final rule (59 FR 19652). In addition, the agency
noted in the preamble that several commenters, including AAMA, stated
that temperature variations should be compensated for when conducting
the crash test. However, neither AAMA nor other commenters suggested
any method to correct for this. After reviewing the components, NHTSA
decided not to specify an ambient test temperature, but to limit the
amount of ambient temperature variation during the 60-minute test
period to 5.6 deg.C (10 deg.F). A temperature variation exceeding
this amount will invalidate the test results. The agency noted that,
``Without such control, a large change in temperature could
artificially affect the test results.'' NHTSA continues to believe that
this test condition will sufficiently minimize changes in test gas
temperature, as well as pressure drop measurement accuracy.
NHTSA appreciates the concerns expressed by Ford and Chrysler in
their petitions. However, as noted above, under real world test
conditions, any variation in test gas temperature will not
significantly affect test results. The agency believes there are three
leakage scenarios that could potentially occur during the 60-minute
test period following barrier impact: No leak, a large leak, and a
small or marginal leak condition. In the case of no leak, Ford and
Chrysler stated in their petitions that a 5.6 deg.C (10 deg.F) drop
in ambient temperature could result in a 60 psi pressure drop even
though there is no leakage. However, since the allowable pressure drop
established in the final rule is at least 1062 kPa (154 psi), a 60 psi
pressure drop will not affect compliance test results since it is well
below the amount allowed in the final rule. Similarly, in the case of a
large leak, any change in test gas temperature should not influence
compliance test results, since all or most of the gas will leak out
during the 60-minute test period, thereby making a non-compliance
obvious. Based on supplemental information which the agency obtained by
telephone from Ford and Blue Bird Body Company on the NPRM, the agency
believes these two conditions, no leak or a large leak, will account
for most of the leakage scenarios after real world CNG vehicle crash
tests. However, in the event there is a slow leak, NHTSA believes that
here, too, test gas temperature will remain relatively constant during
testing, due to thermal contact between the test gas and fuel container
walls. Any change in test gas temperature will tend to be offset by the
temperature or thermal energy of the surrounding container walls, which
along with the test gas have been stabilized to ambient temperature
prior to testing.
NHTSA rejects Ford's recommendation that the final rule exclude
pressure changes due to test gas temperature changes, because it would
require that test gas temperature be measured. NHTSA believes that this
would unnecessarily result in a more costly and complex test procedure.
Further, it could make the fuel system more vulnerable to leakage in a
crash, since an additional fuel system measurement fitting may be
required. In its petition for reconsideration, Chrysler referred to
this as ``* * * the added difficulty of measuring gas temperature
within the high pressure fuel system, which is difficult,
impracticable, and risks compromising the fuel system integrity.'' In
addition, supplemental information which the agency obtained by
telephone from Ford indicates that measuring gas temperature in a CNG
fuel system is not always accurate.
NHTSA also rejects Chrysler's recommendation that an additional 60
psi be added to the allowable pressure drop in the final rule. In the
case of an allowable pressure drop of 1062 kPa (154 psi), adopting
Chrysler's request would have raised this level by approximately 40
percent. The agency believes that that addition could make the
allowable pressure drop levels unsafe, since it would allow more fuel
leakage. This would be clearly inconsistent with the agency's goal of
establishing a minimum leakage requirement that is as close to a no
leakage requirement as possible while still being readily measurable.
For the above reasons, NHTSA denies the requests of Ford and
Chrysler regarding pressure drop.
Fill Condition
As part of the test conditions prior to CNG vehicle crash testing,
S7.1.1 of Standard No. 304 specifies that, ``Each fuel storage
container is filled to 100 percent of service pressure with nitrogen,
N2.'' S4 states that, ``Service pressure means the internal
pressure of a CNG fuel container when filled to design capacity with
CNG at 20 deg. Celsius (68 deg. Fahrenheit).''
In its petition, AAMA stated that since the final rule places no
absolute limits on the ambient temperatures at which testing may be
performed, but merely requires that ambient temperature not change more
than 10 deg.F during the course of the test, fuel storage containers
will not always be filled at and stabilized to a temperature of 20 deg.
Celsius (68 deg. Fahrenheit). According to the petitioner, the fill
pressure to be used for ambient temperatures other than 20 deg. Celsius
(68 deg. Fahrenheit) is unclear and therefore not reasonable,
practicable, or stated in objective terms. AAMA further stated that an
appropriate corrective action would be to amend S7.1.1 of the Standard
to state that, ``Each fuel storage container is filled with nitrogen,
N2, to 100 percent of service pressure adjusted for ambient
temperature.'' AAMA's suggested language is italicized.
After reviewing AAMA's petition for reconsideration about fill
pressure, NHTSA has determined that that organization's requested
modification to S7.1.1 would be inappropriate.
The agency's purpose in specifying that CNG containers be filled to
100 percent of service pressure in S7.1.1 is to provide a reference
point for the fill condition from which crash tests are performed,
e.g., 20,684 kPa (3000 psi) at 20 deg.C (68 deg.F). NHTSA recognizes
that since the final rule does not specify an ambient temperature at
which crash testing is performed, fuel containers will not always be
filled and stabilized to 20 deg.C (68 deg.F). This will result in CNG
container pressures which are different than if testing were performed
at 20 deg.C (68 deg.F), because of the relationship between gas
temperature and pressure. Thus, manufacturers may fill and stabilize
the CNG containers prior to testing to a pressure that is adjusted for
ambient temperature. The final rule does not prohibit this. However,
that pressure, which is adjusted for ambient temperature, must be such
that if ambient temperature were 20 deg.C (68 deg.F), pressure in the
CNG containers would be equal to service pressure. Since the final rule
does not prohibit this adjustment for ambient temperature prior to
testing, NHTSA sees no need to [[Page 2542]] adopt the revised language
suggested by AAMA. Therefore, AAMA's petition concerning fill condition
is denied.
Pressurizing the High Pressure Side
S7.1.2 of the final rule states that, ``Any shutoff valve at the
fuel container is in the open position.'' AAMA states in its petition
that some CNG fuel systems include additional manual shutoff valves in
the high pressure side of the fuel system, and that these valves must
also be open so that pressure is distributed to the entire high
pressure side of the fuel system. If these valves are closed, the
vehicle test conditions would not simulate, to the extent practicable,
conditions present in a real world crash. These observations led that
organization to conclude that the final rule is not reasonable or
practicable. In addition, AAMA stated that this aspect of the final
rule does not meet the need for motor vehicle safety. This is because
manual valves located downstream from the pressure measurement point,
if closed, would seal off part of the high pressure side of the fuel
system. Thus, pressure measurement upstream of the closed valve would
not detect a leak in the sealed off, high pressure portion of the fuel
system.
AAMA stated that an appropriate corrective action would be to amend
S7.1.2 to state that ``* * * normal operating pressures. All manual
shutoff valves are to be left in the open position.'' AAMA's suggested
language is underlined.
After reviewing AAMA's recommendation about shutoff valves, NHTSA
has decided to amend S7.1.2 to state ``All manual shutoff valves are to
be in the open position.''
The agency believes that this change is consistent with the goal in
S7.1.2 which is to have the vehicle test conditions be representative
of real world crash test conditions and to meet the need for motor
vehicle safety. The agency was not aware that there may be manual
shutoff valves within the high pressure portion of the fuel system
other than those located at the fuel containers. In addition, the
phrase in S7.1.2 stating ``Any shutoff valve * * *'' was meant to refer
to manual shutoff valves. Based on the above consideration, NHTSA has
decided to adopt AAMA's request concerning pressurizing the high
pressure side.
Pressure Measurement Location
AAMA stated that the final rule does not specify how fuel system
pressure is to be accessed for measurement. In its response to the
January 1993 NPRM, AAMA stated that it
* * * is concerned about adding pressure transducers to points
in the fuel line solely for purposes of conducting the test. Doing
so creates a point of potential leakage where a fitting joint does
not exist in a non-test vehicle.
AAMA stated that if a NHTSA contractor were to test for compliance by
creating such a pressure measurement point, AAMA member companies
likely would object, pointing out that the fuel system on the vehicle
has been disrupted and therefore would not be representative of the
vehicle as manufactured. AAMA stated that it is not reasonable,
practicable, or appropriate to have a final rule that is silent on
where the pressure is to be measured, thereby leaving its selection to
the discretion of a NHTSA test contractor.
AAMA stated that an appropriate corrective action would be to add a
new S7.1.8, which states, ``The pressure drop measurement specified in
S7.2 (sic) is to be made using a location recommended by the vehicle
manufacturer.'' AAMA's proposed language is underlined. (Note: NHTSA
has verified with AAMA that it intended to reference S5.2 rather than
S7.2 in this statement.)
NHTSA agrees with AAMA's assessment. Based on additional comments
obtained from AAMA in response to the January 1993 NPRM, the agency
understands that vehicle manufacturers will be providing a tap point on
the vehicle's fuel system where pressure measurement is to be obtained.
It would be consistent with the intent of Standard 304 if that pressure
measurement of the fuel system were made at the location specified by
the vehicle manufacturer. Accordingly, AAMA's petition concerning
pressure measurement location is granted.
Miscellaneous Correction
NHTSA is also making a word correction to one of the definitions in
S4, which AAMA pointed out in its petition. The definition for CNG fuel
container currently reads CNG full container. Therefore, the word full
is changed to fuel.
Rulemaking Analyses
A. Executive Order 12866 and DOT Regulatory Policies and Procedures
NHTSA has considered the impact of this rulemaking action under
Executive Order 12866 and the Department of Transportation's regulatory
policies and procedures. This rulemaking document was reviewed under
E.O. 12866, ``Regulatory Planning and Review.'' This action has been
determined to be ``non-significant'' under the Department of
Transportation's regulatory policies and procedures.
B. Regulatory Flexibility Act
NHTSA has also considered the effects of this rulemaking action
under the Regulatory Flexibility Act. Based upon the agency's
evaluation, I certify that this rule will not have a significant
economic impact on a substantial number of small entities. Information
available to the agency indicates that currently there are very few
businesses manufacturing passenger cars or light trucks for CNG use.
The agency further believes that as the market expands for CNG
vehicles, original vehicle manufacturers will begin to produce CNG
vehicles because they will be able to do so at less expense than final
stage manufacturers and alterers. Few, if any, original vehicle
manufacturers which manufacture CNG vehicles are small businesses.
C. Executive Order 12612 (Federalism)
NHTSA has analyzed this rulemaking action in accordance with the
principles and criteria contained in Executive Order 12612. NHTSA has
determined that the rule will not have sufficient Federalism
implications to warrant the preparation of a Federalism Assessment.
D. National Environmental Policy Act
In accordance with the National Environmental Policy Act of 1969,
NHTSA has considered the environmental impacts of this rule. The agency
has determined that this rule will have no adverse impact on the
quality of the human environment. On the contrary, because NHTSA
anticipates that ensuring the safety of CNG vehicles will encourage
their use, NHTSA believes that the rule will have positive
environmental impacts since CNG vehicles are expected to have near-zero
evaporative emissions and the potential to produce very low exhaust
emissions as well.
E. Civil Justice Reform
This final rule does not have any retroactive effect. Under 49
U.S.C. 30103, whenever a Federal motor vehicle safety standard is in
effect, a State may not adopt or maintain a safety standard applicable
to the same aspect of performance which is not identical to the Federal
standard, except to the extent that the State requirement imposes a
higher level of performance and applies only to vehicles procured for
the State's use. 49 U.S.C. 30161 sets forth a procedure for judicial
review of final rules establishing, amending or revoking Federal motor
vehicle safety standards. That section does not require
[[Page 2543]] submission of a petition for reconsideration or other
administrative proceedings before parties may file suit in court.
List of Subjects in 49 CFR Part 571
Imports, Motor vehicle safety, Motor vehicles.
In consideration of the foregoing, 49 CFR part 571 is amended as
follows:
PART 571--[AMENDED]
1. The authority citation for part 571 continues to read as
follows:
Authority: 49 U.S.C. 322, 30111, 30115, 30117, and 30166;
delegations of authority at 49 CFR 1.50.
2. Section 571.303 is amended by revising the definition of CNG
fuel container in S4, revising S7.1.2, and adding S7.1.8 to read as
follows:
Sec. 571.303 Standard No. 303; Fuel system integrity of compressed
natural gas vehicles.
* * * * *
S4. Definitions.
* * * * *
CNG fuel container means a container designed to store CNG as motor
fuel onboard a motor vehicle.
* * * * *
S7.1.2 After each fuel storage container is filled as specified in
S7.1.1, the fuel system other than each fuel storage container is
filled with nitrogen, N2, to normal operating pressures. All
manual shutoff valves are to be in the open position.
* * * * *
S7.1.8 The pressure drop measurement specified in S5.2 is to be
made using a location on the high pressure side of the fuel system in
accordance with the vehicle manufacturer's recommendation.
* * * * *
Issued on: January 4, 1994.
Ricardo Martinez,
Administrator.
[FR Doc. 95-464 Filed 1-9-95; 8:45 am]
BILLING CODE 4910-50-M