Federal Motor Vehicle Safety Standards; Fuel System Integrity of Compressed Natural Gas Vehicles; Compressed Natural Gas Fuel Container Integrity

DEPARTMENT OF TRANSPORTATION

49 CFR Part 571

[Docket No. 93-02; Notice 06]

RIN 2127-AF14

Federal Motor Vehicle Safety Standards; Fuel System Integrity of

Compressed Natural Gas Vehicles; Compressed Natural Gas Fuel Container

Integrity

AGENCY: National Highway Traffic Safety Administration (NHTSA),

Department of Transportation (DOT).

ACTION: Supplemental notice of proposed rulemaking (SNPRM).

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SUMMARY: This notice proposes to amend Standard No. 303, Fuel System

Integrity of Compressed Natural Gas Vehicles, and Standard No. 304,

Compressed Natural Gas Fuel Containers. With respect to Standard No.

303, the notice proposes additional labeling requirements for

compressed natural gas (CNG) vehicles. With respect to Standard No.

304, the notice proposes to specify additional performance requirements

that would ensure a CNG fuel container's integrity. The proposes tests

include environmental cycling tests, an impact test, a gunfire test, a

flaw tolerance test, a pendulum impact test, and a drop test. Along

with the vehicle labeling requirements, the notice proposes additional

labeling requirements for CNG containers. These tests and performance

requirements, which are based on the Natural Gas Vehicle Coalition's

voluntary standard, NGV2, are intended to ensure the structural

integrity of CNG containers.

DATES: Comments on this notice must be received by the agency no later

than February 17, 1995.

ADDRESSES: Comments on this notice should refer to the above docket and

notice number and be submitted to: Docket Section, National Highway

Traffic Safety Administration, Room 5109, 400 Seventh Street SW.,

Washington, D.C. 20590. Telephone: (202) 366-5267. Docket hours are

9:30 a.m. to 4:00 p.m., Monday through Friday.

FOR FURTHER INFORMATION CONTACT:

Mr. Gary R. Woodford, NRM-01.01, Special Projects Staff, National

Highway Traffic Safety Administration, 400 Seventh Street SW.,

Washington, D.C. 20590 (202-366-4931).

SUPPLEMENTARY INFORMATION:

Outline

I. Background

A. General Information

B. Previous Agency Rulemakings

II. Agency Supplemental Proposal

A. General

B. Environmental Cycling Test

C. Road Salt Environmental Test

D. Charpy Impact Test

E. Gunfire Test

F. Damage Tolerance Tests

1. General Considerations

2. Flaw Tolerance Test

3. Pendulum Impact Test

4. Drop Test

G. Bonfire Test Fuel

H. Labeling Requirements

1. CNG Containers

a. Labeling Information

b. Label Location

2. Vehicle Labeling

I. Other Safety Issues

J. Leadtime

K. Benefits

L. Costs

III. Rulemaking Analyses and Notices

I. Background

A. General Information

Natural gas is a vapor that is lighter than air at standard

temperature and pressure.\1\ When used as a motor fuel, natural gas is

typically stored on-board a vehicle in cylindrical containers at a

pressure of approximately 20,684 kPa pressure (3,000 psi). Natural gas

is kept in this compressed state to increase the amount that can be

stored on-board the vehicle. This in turn serves to increase the

vehicle's driving range. Since natural gas is a flammable fuel and is

stored under high pressure, natural gas containers pose a potential

risk to motor vehicle safety.

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\1\Standard temperature is 0 deg. Celsius or 32 deg. Fahrenheit

and standard pressure is 101.4 kiloPascals (kPa) or 14.7 pounds per

square inch (psi).

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Vehicles powered by CNG have not been numerous to date, although

they are increasing. The number of CNG vehicles in the United States

has more than doubled from 10,300 in 1990 to 23,800 at the end of 1992.

The number of CNG vehicles is projected to again double to an estimated

50,800 vehicles in 1994. As discussed in detail in a final rule

published on April 22, 1994, establishing Standard No. 303, Fuel System

Integrity of Compressed Natural Gas Vehicles, recent Federal

legislation, as well as the need to meet environmental and energy

security goals, will lead to increased production and use of these

vehicles. (59 FR 19648)

B. Previous Agency Rulemakings

On October 12, 1990, NHTSA published an advance notice of proposed

rulemaking (ANPRM) to explore whether the agency should issue Federal

motor vehicle safety standards (FMVSSs) applicable to CNG fuel

containers and the fuel systems of motor vehicles using CNG or

liquefied petroleum gas (LPG) as a motor fuel. (55 FR 41561). The ANPRM

sought comment about the crash integrity of vehicle fuel systems, the

integrity of fuel storage containers, and pressure relief for such

containers.

On January 21, 1993, NHTSA published a notice of proposed

rulemaking (NPRM) in which the agency proposed to establish a new FMVSS

specifying performance requirements for vehicles fueled by CNG. (58 FR

5323). The proposal was based on comments received in response to the

ANPRM and other available information.The NPRM was divided into two

segments: (1) vehicle requirements that focused on the integrity of the

entire fuel system, and (2) equipment requirements that focused on the

fuel containers alone. In that notice, the agency proposed specific

requirements applicable to the initial strength, durability, and

pressure relief characteristics of CNG containers. In addition, the

agency sought comments about the effects of corrosion and cold

temperature extremes on CNG containers, and their rupture without

fragmentation.

NHTSA received a large number of comments to the docket addressing

the January 1993 proposal. The commenters included manufacturers of CNG

containers, vehicle manufacturers, trade associations, other CNG-

oriented businesses, research organizations, State and local

governments, the United States Department of Energy, and energy

companies. In addition, NHTSA met with the Compressed Gas Association

(CGA) and the Natural Gas Vehicle Coalition (NGVC) and had telephone

conversations meetings with some of the commenters. A record of each of

these contacts may be reviewed in the public docket.

The commenters generally believed that a Federal safety standard

regulating the integrity of CNG fuel systems and fuel containers is

necessary and appropriate. In fact, some commenters, including the CGA,

the NGVC, and CNG container manufacturers stated that NHTSA should

issue a Federal standard as soon as possible to facilitate the safe and

expeditious introduction of CNG fueled vehicles. With respect to the

equipment requirements, the commenters generally believe that Federal

requirements about the CNG fuel container integrity are needed and

should be implemented as quickly as possible.

In addition to comments addressing the proposed requirements for

durability, strength, and pressure relief, some commenters favored the

promulgation of requirements about corrosion resistance, high and low

temperature extremes, damage tolerance, and rupture characteristics of

CNG containers.

As noted above, NHTSA recently established Standard No. 303. It

specifies vehicle performance requirements for the fuel system of

vehicles fueled by CNG. The Standard enhances the fuel system integrity

of CNG vehicles by subjecting the vehicles to crash testing and placing

a limit on the post-crash pressure drop in the fuel system. The

Standard specifies frontal, rear, and lateral barrier crash tests for

light vehicles and a moving contoured barrier crash test for school

buses with a GVWR over 10,000 pounds.

NHTSA has also issued a final rule that establishes a new Federal

motor vehicle safety standard, Standard No. 304, Compressed Natural Gas

Fuel Containers, that specifies tests and performance requirements

applicable to a CNG fuel container's durability, strength, and pressure

relief. A pressure cycling test evaluates a container's durability by

requiring a container to withstand without any 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 refuelings over its service life. A

burst test evaluates a container's initial strength and resistance to

degradation over time. This requirement helps to ensure that a

container's design and material are appropriately strong over the

container's life. A bonfire test evaluates a container's pressure

relief characteristics when pressure builds in a container, primarily

due to temperature rise. In addition, the final rule specifies labeling

requirements for CNG fuel containers. These requirements are based on

specifications in NGV2, a voluntary industry standard addressing CNG

fuel containers which was adopted by the American National Standards

Institute (ANSI)\2\.

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\2\NGV2 was developed by an industry working group that included

container manufacturers, CNG users, and utilities.

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NGV2 specifies four types of container designs. A Type 1 container

is a metallic noncomposite container. A Type 2 container is a metallic

liner over which an overwrap such as carbon fiber or fiberglass is

applied in a hoop wrapped pattern over the liner's cylinder wall. A

Type 3 container is a metallic liner over which an overwrap such as

carbon fiber or fiberglass is applied in a full wrapped pattern over

the entire liner, including the domes. A Type 4 container is a non-

metallic liner over which an overwrap such as carbon fiber or

fiberglass is applied in a full wrapped pattern over the entire liner,

including the domes.

II. Agency Supplemental Proposal

A. General

Based on comments to the January 1993 NPRM and other available

information, NHTSA has decided to issue this supplemental notice of

proposed rulemaking (SNPRM), to propose additional performance

requirements and tests to ensure a CNG container's structural

integrity. Among the proposed tests are environmental cycling tests, a

low temperature impact test, a gunfire test, a flaw tolerance test, a

pendulum impact test, and a drop test. One environmental cycling test

would evaluate a container's resistance to internal corrosion and high

humidity as well as the effects of high and low temperatures on a

container. A second environmental test would evaluate a container's

resistance to road salt and other acidic chemicals. The impact test,

known as the Charpy test, would evaluate a metal container's brittle

fracture characteristics under low temperatures. The gunfire test would

evaluate container fragmentation. Three tests, the flaw tolerance test,

the pendulum impact test, and the drop test, would evaluate a

container's resistance to external damage. Specifically, the flaw

tolerance test would evaluate a container's exterior resistance to

abrasion; the pendulum impact test would evaluate a container's ability

to withstand a sharp external blow; and the drop test would evaluate a

container's ability to withstand a blunt external blow. This notice

also proposes labeling requirements applicable to CNG vehicles and

labeling requirements for CNG containers in addition to those required

by the CNG container final rule.

Each of the proposed performance requirements and test procedures

are modeled after provisions in NGV2 or are similar to those

requirements. The agency tentatively concludes that modeling the

Federal standard after NGV2 would be the best way to regulate how a CNG

container reacts to such conditions as corrosive substances,

temperature extremes, external damage, and rupture. In some instances,

the agency departed from NGV2's performance requirements and test

criteria to be consistent with 49 U.S.C. 30111 (formerly section 103 of

the National Traffic and Motor Vehicle Safety Act, 15 U.S.C.

Sec. 1392). That statute commands the agency to issue ``motor vehicle

safety standards'' that are practicable, meet the need for motor

vehicle safety, and are stated in objective terms. One example of such

a departure can be found in the environmental cycling performance

requirement for internal corrosion. Instead of stating that there shall

be no ``evidence of distortion, deterioration, or failure,'' the

proposal states that the container ``shall not leak or be distorted.''

Another example can be found in the gunfire test conditions. Instead of

stating that ``(t)he distance from firing location to test container is

not to exceed 46 meters,'' the proposal states that ``(t)he distance

from firing location to test container is 46 meters.'' The most

significant differences between the proposal and NGV2 are discussed

below.

B. Environmental Cycling Test

Section 1-18(d)(2) of NGV2 includes an environmental cycling test

to prevent the unreasonable corrosion of a CNG container's internal

surface. In addition, this test evaluates the effect that high humidity

as well as high and low temperatures have on the CNG containers.\3\

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\3\The Charpy impact test also evaluates low temperature

performance for metal containers and liners because some metals are

susceptible to brittle fracture at low temperatures.

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In the ANPRM and NPRM, NHTSA noted that the level of impurities in

CNG (i.e., gas quality) could influence the fuel container's integrity.

Specifically, certain compounds in CNG could lead to stress corrosion

cracking, corrosion, fatigue or other internal harm to the container's

integrity. Such harm could cause the CNG containers to fail. The agency

initially decided not to propose a performance test to address a CNG

container's ability to withstand corrosion, since the agency was not

aware of any readily available performance test that would address the

failure modes at issue. Nevertheless, in the NPRM, NHTSA requested

comments about the need for a requirement addressing corrosion and, if

so, what tests and performance levels are most appropriate. In

particular, the agency requested comment about the practicability of

using the NGV2's environmental cycling test. In the NPRM, the agency

specifically asked whether, instead of adopting the first sentence of

the test verbatim, the agency should say ``One representative container

free of any protective coating shall be cycle tested as follows, and

shall not leak * * *''

Commenters on the NPRM stated that there are two principal ways to

regulate containers to prevent unreasonable internal corrosion: (1)

Regulating the gas quality or (2) regulating container performance.

NGVC, Pressed Steel Tank Co., EDO, the National Fire Protection

Association, the American Automobile Manufacturers Association (AAMA),

Tecogen, and Ontario recommended that the agency adopt gas quality

requirements for CNG such as those set forth in a Society of Automotive

Engineers (SAE's) Recommended Practice SAE J1616, ``Fuel Composition

for Natural Gas Vehicles,'' February 1994. That recommended practice

addresses internal corrosion by limiting the amount of water and other

impurities in CNG.

After reviewing the comments and other available information. NHTSA

has decided to propose a corrosion resistance requirement for CNG

containers. The agency notes that under 49 U.S.C. 30101 et seq.

(formerly the Safety Act, 15 U.S.C. 1381 et seq.), NHTSA is authorized

to regulate the manufacture of motor vehicles and motor vehicle

equipment. However, it has no authority to regulate fuel quality since

fuel is not considered to be motor vehicle equipment. Therefore, NHTSA

cannot issue standards regulating the quality of CNG. Nevertheless, the

agency encourages the industry to improve gas quality for CNG vehicles

through voluntary standards such as SA J1616.

NHTSA has decided to propose a performance requirement to ensure

that a CNG container resists corrosion. Such a requirement would

prevent catastrophic failures of CNG containers due to internal

corrosion. This is particularly important since the agency only has

statutory authority to issue safety standards that regulate the

condition and performance of vehicles prior to their first consumer

purchase. The agency does not have any authority to require periodic

inspection of containers for corrosion. NHTSA is proposing to adopt an

environmental cycling performance requirement and test procedure

patterned after the ones in NGV2. The proposed performance requirement

is set forth in S7.5, and the proposed test conditions and procedures,

in S8.5.

NGV2 states that a ``container free of any protective coating shall

be cycle tested, without showing evidence of distortion, deterioration

or failure * * *'' The agency believes that while the term ``without

distortion'' appears to be objective, the terms ``without deterioration

or failure'' are too ambiguous and broad to permit their incorporation

in a Federal Motor Vehicle Safety Standard. Therefore, the agency has

decided not to include the terms ``deterioration'' and ``failure'' in

its proposal. Instead, the agency is proposing that its pass/fail

criteria for the environmental cycling test depart from NGV2 and state

that, when cycle tested, the CNG container ``shall not leak or

permanently change in external configuration or dimensions.'' NHTSA has

added the prohibition against leakage, since the absence of leakage can

be objectively determined. Further, the prohibition is consistent with

the environmental cycling test's safety goal and with the pressure

cycling test and hydrostatic burst test that the agency adopted when it

issued Standard No. 304.

Under today's proposal, the phrase ``shall not . . . permanently

change in external configuration or dimensions'' throughout the test is

intended to serve the same purpose as the NGV2 ``no distortion''

criterion. Thus, if there were a slight bulge in one location or if

there were a change in the container's volume by even one tenth of one

percent, the container would be considered to be distorted. A pass/fail

gauge could be adjusted to fit the container before the test, and then

used again after the test to verify that a container's dimensions had

not changed. NHTSA requests comments about this ``zero distortion''

requirement, and whether some amount of distortion should be allowed.

If so, how should the permissible amount of distortion be quantified

and measured? The agency also invites comments on how the no distortion

criterion might otherwise be objectively expressed. In addition, the

agency requests comments on whether there are other terms, such as

fiber delamination, which should be incorporated and how they could be

objectively defined.

As an alternative, NHTSA is considering a no leakage criterion as

the sole pass/failure performance requirement. However, under this

alternative, the agency would increase the two sets of 5,000 cycles to

9,000 cycles each. Thus, the standard would specify a total of 18,000

cycles instead of the 10,000 cycles currently specified in NGV2. The

agency tentatively concludes that the additional cycles would be

necessary since this alternative proposal would otherwise be less

stringent than NGV2 which contains additional criteria to disqualify

substandard containers, i.e., distortion, deterioration, and failure.

The agency further notes that 18,000 cycles is consistent with the

ambient pressure cycling in NGV2 and in FMVSS No. 304. That cycling

represents severe service, i.e., four refuelings per day, 300 days per

year for 15 years. The agency requests comments on this alternative,

and on other approaches that might be more appropriate. In addition,

the agency requests that commenters suggesting other approaches include

measurable pass/fail performance criteria and a proposed test

procedure.

Section S8.5 sets forth the procedures and conditions for the

environmental cycling test. As with the proposed performance

requirements, these provisions are modeled after NGV2. The agency has

tentatively adopted modified versions of certain provisions in order to

be consistent with the criteria that are within the agency's authority.

NGV2 further specifies that during the environmental cycling test

the container is pressurized ``using natural gas or methane.'' This is

part of the test's preconditioning phase in which a corrosive material

is introduced inside the container to determine its corrosion

resistance. The agency is proposing that only automotive grade natural

gas be used in the environmental cycling test. The agency believes that

specifying only one test gas would make the test more repeatable for

enforcement purposes. Further, although the major constituent of

natural gas is methane, natural gas does contain other minor

constituents which could make the test performed with natural gas more

severe than if only pure methane were used. Therefore, the use of

natural gas would represent a more severe scenario that is closer to

real world use. NHTSA requests comment on the appropriateness of using

only natural gas in the environmental cycling test, rather than

specifying both fuels.

NHTSA has decided to propose language addressing the use of

protective coatings that it believes is consistent with NGV2.

Specifically, S8.5.2 states that ``A CNG fuel container free of any

protective coating'' is cycle tested in a specified manner. The agency

believes that the phrase ``free of any protective coating'' refers to

temporary coatings such as oil and grease, so as not to inhibit action

from the corrosive materials during subsequent testing. The agency

further believes that it would be inappropriate for the agency to

preclude permanent coatings such as paint or other materials, since

this would discourage manufacturers from applying permanent coatings

that increase corrosion resistance. The agency requests comments on how

best to describe this concept. An alternative to the proposal to

specify ``free of any protective coating,'' would be to specify ``The

container shall be in the as manufactured condition.''

NHTSA is also proposing relative humidity conditions during the

environmental cycling test. Specifically, under the proposal, S8.5.2.2

would specify ``Condition the container for 48 hours at zero pressure,

60 deg. C (140 deg. F) and 95 percent relative humidity. To obtain the

specified temperature and relative humidity, spray with a fine spray or

mist of water at 60 deg. C (140 deg. F) in a chamber held at 60 deg. C

(140 deg. F).'' NHTSA requests comments on how the phrase ``fine spray

or mist of water'' could be made more objective, since different rates

of spray might influence the humidity level. As an alternative, the

agency is considering a rate of spray consistent with ANSI standard

Z26.1-1977, which is referenced in FMVSS NO. 205, Glazing Materials.

That provision specifies that ``The fine spray of water shall be under

a pressure of 172 to 207 kPa (25 to 30 psi) at the nozzle and in

sufficient volume to wet the container immediately upon impact.''

Another alternative would be to specify a relative humidity level of 95

percent. This would allow manufacturers and test facilities the

flexibility to determine how that level is achieved. The agency

requests comments on how best to specify relative humidity in the

environmental cycling test.

In comments to the NPRM, Norris and NGV Systems supported an

alternative corrosion test issued by the National Association of

Corrosion Engineers (NACE), NACE Standard TM0177-90. The NACE voluntary

standard includes several test methods for determining the sulfide

stress cracking resistance of steels. Sulfide stress cracking corrosion

can result from the presence of too much hydrogen sulfide in natural

gas. NHTSA requests comments on the appropriateness of using the NACE

test either in conjunction with or in lieu of NGV2's environmental

cycling test.

The NACE test provides a laboratory method but does not specify

acceptable results. If the agency were to incorporate the NACE test in

an FMVSS, it would be necessary to specify performance requirements.

The agency believes that this could be done by making the performance

requirements consistent with the ones already contained in the draft

International Standards Organization (ISO) standard for CNG containers

(Section A13). If the agency decides to adopt the NACE test, the NACE

Standard Tensile Test method would be used and subsized tensile

specimens (gauge diameter 2.54 mm) would be machined from the wall of a

finished container, placed under constant tensile load, and immersed in

the NACE test solution. Tests would be conducted to demonstrate that

the threshold stress exceeds 20 percent of the specified minimum yield

strength of the steel, where threshold stress is the maximum stress at

or below which no specimen fails the test for a period of 720 hours.

NHTSA requests comments on the need for the NACE test and various

aspects of the test, including the appropriateness of setting threshold

stress at 20 percent above the yield strength and the number of tests

which should be conducted to demonstrate this.

C. Road Salt Environmental Test

NHTSA has decided to propose a road salt environmental test for CNG

fuel containers to address the potential for container degradation due

to road salt and other acidic chemicals. The proposed test is in

addition to the environmental cycling test already discussed.

NHTSA has decided to propose this requirement after learning of two

CNG fiberglass fuel container failures which occurred in early 1994.

NHTSA is concerned about the exposure of container exterior surfaces to

acidic fluids, which may lead to stress corrosion cracking and

container failure. Depending on the environmental conditions present,

road salt or salt spray while driving in wet conditions, can be acidic

in nature. Therefore, the agency proposes this road salt environmental

test to address these potential safety problems.

The number of test cycles and the pass/fail criterion are the same

as those proposed for the environmental cycling test discussed earlier.

However, prior to cycling, the fuel container would be exposed to salt

spray in accordance with American Society for Testing and Materials

(ASTM) B117-73, ``Method of Salt Spray (Fog) Testing.'' This method of

salt spray testing is used in FMVSS NO. 108, Lamps, Reflective Devices,

and Associated Equipment for testing the corrosion resistance of

headlamps.

Under the proposal, a CNG fuel container would be exposed to the

salt spray for 240 hours, consisting of ten successive 24 hours

periods. Within each period, the container would be exposed to the

spray for 23 hours. During the 24th hour, the salt spray would not be

activated. Following the 240 hours of salt spray exposure, the

container would then be cycled for 5,000 cycles, through hydrostatic

pressurization, from not more than 10 percent of service pressure to

service pressure. Then it would be hydrostatically pressure cycled for

another 5,000 cycles from not more than 10 percent of the service

pressure to 125 percent of the service pressure. When tested in this

way, the container would be prohibited from leaking or permanently

changing in external configuration or dimensions.

NHTSA requests comments on the appropriateness of using this test

to address exterior environmental degradation of CNG fuel containers

due to road salt and other acidic chemicals. The agency specifically

requests comments on whether the proposed test would adequately address

the potential for stress corrosion cracking of fiberglass overwrap in

CNG fuel containers, and whether it should be applied to all types of

CNG fuel containers, including all metal, hoop wrapped with metal

liner, full wrapped with metal liner, and all composite for both

fiberglass and carbon fiber. NHTSA also requests comments on whether

the 240 hours of salt spray exposure appropriately reflects the amount

of exposure which can reasonable be expected during the life of a CNG

fuel container.

In addition, NHTSA requests comments on the pH level of the salt

solution used in the proposed test method. Under ASTM B-117, the pH

level of the salt solution is in the range of 6.5 to 7.2 at 35 deg.C,

although the method provides for an upward or downward adjustment in

pH. A downward adjustment of pH level would make the solution more

acidic, thereby representing more severe road chemicals which CNG

containers may encounter. It appears possible that stress corrosion

cracking of fiberglass may be accelerated with decreasing pH.

Therefore, the agency requests comments on whether a lower pH range for

the salt solution should be specified in the test method, such as three

to four.

NHTSA also requests comments on whether to specify the pass/fail

criterion for the salt spray test to ``no leakage'' in lieu of ``shall

not leak or be permanently changed in external configuration or

dimensions.'' Concurrently, the agency would also increase the number

of cycles during testing from two sets of 5,000 cycles each to two sets

of 9,000 cycles each. The agency requests comments on whether these

modifications in the number of cycles would be appropriate for the road

salt test as well as the environmental cycling test discussed earlier.

The agency also requests comments on the estimated cost of the salt

spray test and the extent to which current CNG containers would comply

with the requirements.

D. Charpy Impact Test

Section 1-12(d) and 1-13(e) of NGV2 set forth an impact test, known

as the Charpy test, and performance criteria to address brittle

fracture of steel CNG containers and liners under low temperatures.

NGV2 states that this test is an indicator of the performance of heat

treated steels.\4\ The Charpy test evaluates marginal heat treating

performance which can lead to poor fracture performance, degraded

resistance to stress corrosion cracking, and lessened fatigue

resistance.

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\4\ The Charpy test only evaluates steel CNG containers and

liners. The environmental cycling test evaluates composite materials

under low temperature conditions.

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In the NPRM, NHTSA requested comments on whether there is a safety

problem sufficiently serious to warrant establishing a requirement for

low temperature testing of CNG container materials. The agency

requested these comments due to its concern that certain materials such

as high strength steels can lose their ductility at low temperatures, a

situation that could lead to a container's catastrophic failure. The

agency requested specific comments on the Charpy impact test set forth

in NGV2.

NGV Systems, ARC, Comdyne, Pressed Steel Tank, EDO, Fiber Dynamics,

AAMA, Minnesota Gas, Amoco, Navistar, CNG Pittsburgh, and Manchester

commented about the need for cold temperature testing. All but

Manchester believed that the standard should include some sort of cold

temperature testing for containers. Manchester stated that the

container's service environment should be examined to determine if such

cold temperature testing is needed. Most commenters stated that

temperature extremes should be accounted for in the standard but did

not elaborate about the specific test. PST recommended that the agency

include the Charpy impact test in the Federal standard. AAMA and EDO

recommended that the containers be cycled at -40 deg. C (-40 deg. F)

and -50 deg. C (-58 deg. F), respectively.

After reviewing the comments, NHTSA has decided to propose amending

Standard No. 304 to include a low temperature test patterned after the

Charpy impact test. This test is set forth in sections 1-12(d) and 1-

13(e) of NGV2, which references Methods for Notched Bar Impact Testing

of Metallic Materials, ASTM E 23. Section 1-13(e) states that the

average energy absorbed by the three test specimens shall not be less

than 100 J/cm\2\. The minimum value for any one specimen shall not be

less than 80 J/cm\2\. Under the test, a pendulum swings down and hits a

specimen. The test device then measures the amount of energy

transmitted into the specimen needed to break it. If the specimen

breaks at low levels of energy, then it would fail the test. To

illustrate, while a substance such as glass would break at very low

energy levels, a non-brittle metal would break only at relatively high

energy levels. Specifically, the purpose of this test is to determine

the brittle fracture behavior of steels. It also evaluates the

performance of steels which have been heat treated as part of the

manufacturing process. An improper heat treatment process can result in

the material being brittle and thus more susceptible to fatigue and

stress corrosion cracking. Non-steel containers and liners need not be

tested to comply with the Charpy test because they are not heat treated

this way. The agency requests comments about the agency's decision to

propose the Charpy impact test. Is it appropriate to only apply these

requirements to Type 1 containers and Type 2 and Type 3 containers with

steel liners? In addition, NHTSA requests comments on applicable

performance tests for fracture and fatigue assessment of liner

materials other than steel, if such materials perform a structural

function, e.g., aluminum liners or containers. Along with this

information, commenters should include a description of the specific

performance tests recommended, along with objective pass/fail criteria.

NHTSA agrees with the recommendations by AAMA and EDO that

containers be pressure cycled at low temperatures (e.g., -40 deg. C

(-40 deg. F)). The agency notes that this low temperature is consistent

with test conditions in NGV2 and NHTSA standards, including Standard

No. 105, Hydraulic Brake Systems, Standard No. 106, Brake Hoses, and

Standard No. 108, Lamps, Reflective Devices, and Associated Equipment.

The agency requests comment about whether the proposed test temperature

is appropriate.

In response to Manchester's comment that the service environment

should be examined to determine if cold temperature testing is needed

for a particular container, NHTSA notes that it would be impracticable

to determine what type of environment each individual container would

encounter. In establishing a requirement, the agency believes that it

is appropriate to test CNG containers in a worst case scenario, such as

the low temperature levels being proposed.

E. Gunfire Test

Section 1-18(j) of NGV2 includes a gunfire test that evaluates

whether a fully pressurized container fragments upon suffering a high

impact puncture. A similar puncture could occur in a motor vehicle

crash, causing the propulsion of container fragments at high speeds.

The gunfire test assures that a container will instead essentially

remain in one piece.

In the NPRM, the agency discussed a specific test criterion in

which the container would be permitted to rupture only if there were no

fragmentation. The container industry refers to this situation as

``leak before burst.'' Containers that leak before bursting are

designed to release their contents through the sidewall without

explosive fragmentation when the container becomes overpressurized. The

industry tests for this characteristic by piercing the pressurized

container with a gunshot. The area around the container is then

examined for fragmentation. The container is supposed to be designed so

that no fragments will break off during this failure. In the NPRM, the

agency requested comments about how to define the term ``without

fragmenting'' for regulatory and compliance purposes.

Brunswick, NGV Systems, PST, EDO, CNG Pittsburg, and AAMA commented

about container fragmentation. These commenters stated that in the

event of a rupture, the CNG fuel containers should be designed to

release their contents through their sidewalls without fragmentation.

Brunswick, AAMA, NGV Systems, EDO, and PST commented about how to

define the phrase ``without fragmenting.'' EDO recommended that the

container be required to remain ``in one piece.'' NGV Systems stated it

should be defined as ``no separation of parts such that projectiles are

possible.'' AAMA stated that it should be defined as ``no separation of

pieces exceeding one gram in mass from the fuel tank.'' Brunswick

stated that it should be defined as loss of small pieces not exceeding

30 grams (one ounce) in weight. PST also indicated that 30 grams (one

ounce) is an acceptable size.

Based on the comments and other available information, NHTSA has

decided to propose amending Standard No. 304 to include a gunfire test

similar to the one set forth in NGV2, with some modifications. The

agency believes that if a CNG container is punctured in a crash, the

failure should result in a controllable situation, e.g., fuel leakage,

rather than a catastrophic explosion of the container. A catastrophic

failure would present a much more serious failure mode than fuel

leakage through the sidewall, since fragments could be propelled in all

directions at high speeds and with tremendous force. Such fragments

could pose a significant safety risk to vehicle occupants and others

near the vehicle.

With respect to the performance criteria for the gunfire test, NGV2

states that ``The tested container shall reveal no evidence of a

fragmentation failure'' and ``Loss of small pieces of composite

material which would not have sufficient momentum to penetrate sheet

metal typically found in automobile construction shall not constitute

failure of the test.'' Under the second phrase, NGV2 allows the

fragmentation of small pieces, even though the gunfire test is intended

to prevent fragmentation.

NHTSA has tentatively concluded that some of NGV2's performance

requirements and test conditions are insufficiently objective for use

in a FMVSS. In order to establish objective, safety criteria, NHTSA has

decided to propose incorporating the recommendations by Brunswick and

PST to prohibit fragments exceeding 30 grams (one ounce) in mass.

Although the intent of the gunfire test is to demonstrate no

fragmentation, the agency understands that small composite pieces or

fragments are considered normal. Therefore, the agency has tentatively

concluded that to prohibit all fragmentation, as recommended by EDO and

NGV Systems would not be practicable. Similarly, the agency believes

that AAMA's recommendation to prohibit the separation of pieces

exceeding one gram (0.035 ounce) would not be practicable and would

involve very small pieces that could be difficult to measure. NHTSA has

tentatively concluded that prohibiting pieces in excess of 30 grams

would provide for a practicable, objective, and safe performance

criterion for the gunfire test. However, the agency requests comments

on the proposed size, and whether the standard should prohibit all

fragmentation or whether some smaller level of fragmentation would be

measurable and safe. What is the lightest container fragment that would

be readily measurable and would not pose an unreasonable risk to the

safety of motorists? NHTSA also seeks comment on whether the container

should be pressurized with nitrogen or air, since only one gas should

be used to assure consistency of testing.

NHTSA has tentatively determined that it is necessary to depart

from certain aspects of the gunfire test in NGV2 to make the agency's

proposed requirement objective and ensure repeatable test results. As

proposed in this notice, these modifications include specifying the

precise muzzle velocity, the projectile's path, and the precise

distance.

F. Damage Tolerance Tests

1. General Considerations

NGV2 addresses damage tolerance with three separate tests: a flaw

tolerance test, a pendulum impact test, and a drop test. In general,

the damage tolerance tests serve to evaluate damage caused by

incidental contact with other objects. Such contact can occur in a

variety of ways. For instance, containers mounted underneath the

vehicle could be damaged by road debris. Similarly, containers mounted

in the bed of a pickup truck could be damaged by cargo or tools being

thrown on them. The flaw tolerance test evaluates abrasive damage to

composite overwraps such as scratches and small cuts on the container.

If the overwraps are cut or gouged, they may unravel or delaminate,

possibly causing container failure. The pendulum impact evaluates sharp

blows to the container. The drop test evaluates blunt impacts to the

container.

NHTSA did not address damage tolerance in the January 1993 NPRM.

Nevertheless, CGA, Tecogen, Comdyne, ARC, and Brunswick commented that

a container's resistance to mechanical damage from incidental contact

or road debris should be tested. Of these commenters, only Brunswick

suggested a specific test procedure to determine container damage

tolerance. Brunswick stated that NGV2 adequately addresses resistance

to mechanical damage with the flaw tolerance, pendulum impact, and drop

tests. In addition, it stated that the effects of more severe damage,

such as a puncture, are addressed with the gunfire test.

NHTSA has decided to propose the three damage tolerance tests in

NGV2 because the agency has tentatively concluded that, during normal

use, CNG containers may be exposed to each type of external damage

addressed by these tests. This may be especially true for containers

sold in the aftermarket, since vehicle manufacturers would presumably

be more likely than vehicle converters to design their vehicles to

protect containers from exposure to road debris and other damage. This

is so because vehicle manufacturers can design a CNG vehicle with

container placement in mind. Converters are not involved in the

original designing of the vehicles they convert and may have to place a

container in a relatively vulnerable location given space limitations.

NHTSA is proposing to subject Type 1 containers to the drop test,

but not to the other two tests, since noncomposite metal containers are

generally not affected by the proposed damage evaluated by those tests.

Type 2, 3, and 4 composite containers would be subject to all three

damage tolerance tests. The agency requests comments about the

appropriateness of applying the proposed damage tolerance tests to the

different types of CNG containers.

In NGV2, the criterion for each damage tolerance test is that the

container, after having a cut made into the container or being

impacted, must sustain 1,500 pressure cycles without evidence of

failure such as distortion or leakage. The only exception to this is

the drop test. The drop test in NGV2 requires two alternative sets of

cycling tests. If the container sustains damage that would cause its

rejection at a three year inspection interval specified by NGV2, the

container is tested for 1,500 cycles. In contrast, if the container

sustains damage that would cause it not to be rejected at a three year

inspection, it is tested for 18,000 cycles. The 1,500 cycles in NGV2

apparently corresponds to the maximum number of fills expected during

the three year inspection interval. Because NGV2 requires reinspection

every three years, it is structured to permit a level of damage to the

container that would keep it in service until the maximum inspection

interval of three years is completed. In contrast, NHTSA has no

statutory authority to require container inspection after the first

consumer purchase of the container.\5\

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\5\The agency is proposing labeling requirements to encourage

the periodic inspection of containers every 12 months, as explained

below.

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In today's notice, NHTSA is proposing 1,500 cycles for the flaw

tolerance and pendulum impact tests, and the more severe alternative of

18,000 cycles for the drop test. This is consistent with the manner of

cycles specified in NGV2, after which the agency is patterning its

proposal. However, since NHTSA has no authority to require the periodic

inspection of CNG containers, the agency requests comments on whether

1,500 cycles is adequate to assure the safety of a CNG container

throughout its life. As a alternative, the agency is considering

requiring 18,000 cycles for the flaw tolerance and pendulum impact

tests. This is consistent with the pressure cycling test in FMVSS No.

304 and with the drop test where no inspection would be involved. It

would also represent the worst case scenario for a container which

sustains damage early in its service life, but may not be subsequently

inspected, since 18,000 cycles represents four refuelings per day, 300

days per year for 15 years. The agency requests comments on the

appropriate number of cycles for the flaw tolerance, pendulum impact,

and drop tests to assure the safety of the traveling public.

2. Flaw Tolerance Test

Section 1-18(f)(1) of NGV2 sets forth a flaw tolerance test, which

evaluates a container's ability to withstand external damage caused by

abrasive material scratching a container, NHTSA is proposing to adopt

the flaw tolerance test in NGV2 with some minor modifications. The

agency's adaptation of these performance requirements and test

conditions and procedures is set forth in sections S7.8 and S8.8 of

this notice's regulatory text.

NGV2's flaw tolerance test specifies that the container shall be

tested ``without evidence of distortion, deterioration or failure'' and

``show no evidence of flaw propagation\6\ or other physical damage

likely to weaken the container appreciably.'' as explained in the

earlier discussion on the environmental cycling test, these performance

requirements contain subjective criteria that the agency believes need

to be modified to be objective and enforceable. The agency believes

that the terms ``without deterioration or failure'' and ``other

physical damage likely to weaken the container appreciably'' are

unreasonably ambiguous and broad. Therefore, the agency has decided not

to include, in the proposed requirement, the terms ``deterioration''

and ``failure'' and the phrase ``other physical damage likely to weaken

the container appreciably'' since these terms are not sufficiently

objective to include in a Federal standard and would not provide

measurable criteria for enforcement. The agency welcomes comments about

ways to refine terms to make them objective. In addition, the agency

requests comments on whether there are other terms, such as fiber

delamination, which should be incorporated and how they could

objectively be defined.

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\6\Propagation is defined as ``enlargement or extension (as of a

crack) in a solid body. (Webster's Ninth New Collegiate Dictionary)

---------------------------------------------------------------------------

Instead, the agency is proposing a modified version of the NGV2

pass/fail criteria for the flaw tolerance test that states that when

cycle tested, the CNG container ``shall not leak or permanently change

in external configuration or dimension.'' In addition, NHTSA is

proposing an additional performance provision to prohibit the growth of

a longitudinal cut made in the container. NHTSA has added the

prohibitions against leakage and increase in the size of cut since

compliance with them can be objectively determined. It is also

consistent with the flaw tolerance test's safety goal and with the

performance requirements for the presence cycling test and the

hydrostatic burst test in Standard No. 304. The agency previously

discussed the no distortion criterion in the environmental cycling

section and request similar comments here. In addition, the other

requirement being proposed for the flaw tolerance test is that the

``cut made in accordance with S8.8 for the purpose of this test shall

not increase in length, width or depth as a result of this test.''

NHTSA has tentatively determined that it is also necessary to

depart from certain aspects of NGV2's flaw tolerance test procedures

and conditions to make agency's flaw tolerance test objective and

repeatable. As proposed in this notice, these modifications include

specifying the precise dimensions and location of the flaw.

NGV2 specifies that a cut be made in the other wall at

approximately midlength and that the cut be not less than 0.75 mm

(0.030 inches) in depth. The agency is proposing additional provisions

to make the proposed FMVSS more precise, thereby increasing the test

procedure's objectivity and repeatability. For instance, the agency is

proposing to amend the standard to specify that the cut be 0.75 mm

wide. The agency tentatively believes that these dimensions represent

abrasions that containers may experience as a result of contacting road

debris. However, the agency requests comments on the cut's dimensions,

including the appropriate width, and whether the length, width, and

number of such cuts should be increased.

3. Pendulum Impact Test

Section 1-18(f)(2) of NGV2 sets forth a pendulum impact test which

evaluates a container's ability to withstand a sharp external blow.

NHTSA is proposing to adopt the pendulum impact test in NGV2 with some

minor modifications. The agency's adoption of these performance

requirements and test conditions is set forth in sections S7.9 and S8.9

of this notice's regulatory text.

NGV2 specifies that ``The tests shall be made on the points of the

container which are regarded as vulnerable. The points regarded as

vulnerable are those which are most exposed or weakest having regard to

the shape of the container and/or the way in which it is installed on

the vehicle.''

NHTSA has decided to propose modifying this provision since it is

not objective. Instead, the agency is proposing to require that the

pendulum impact test be conducted at ``any point and any angle.'' NHTSA

anticipates that to be able to certify compliance with the requirement,

manufacturers would direct the test impacts to the container's most

vulnerable points. Such a test procedure would be consistent with the

regulatory language specified in Standard No. 301's moving contoured

barrier test. The agency requests comments about whether such a test

condition would be appropriate for pendulum impact testing of CNG

containers.

4. Drop Test

Section 1-18(g) of NGV2 sets forth a drop test, which evaluates a

container's ability to withstand a blunt external blow. NHTSA is

proposing to adopt the drop test in NGV2 with some minor modifications.

The agency's adoption of these performance requirements and test

procedures is set forth in sections S7.10 and S8.10 of this notice's

regulatory text.

As with NGV2, NHTSA is proposing to specify that a container be

dropped at ambient temperature without internal pressurization or

attached valves. In the test, the container is held in a horizontal

position with the container's bottom 3.05 meters (10 feet) above the

surface onto which it is dropped.

Today's proposal, consistent with NGV2, specifies that the surface

onto which the CNG container is dropped ``shall be a smooth, horizontal

concrete pad or flooring.'' NHTSA notes that this definition of the

surface is not fully objective. As an alternative, the agency is

considering specifying that the surface be made of concrete that is at

least four inches thick. NHTSA requests comments on this alternative,

and on how the surface could otherwise be more objectively defined.

G. Bonfire Test Fuel

In the NPRM, NHTSA proposed that the fire for the bonfire tests be

generated by No. 2 diesel fuel. This fuel type was proposed so that the

standard would be consistent with the bonfire test in NGV2, which

specifies this type of fuel.

NGVC, CGA, AAMA, and Norris commented that the agency should

specify a different fuel to generate a bonfire that is more

environmentally sound. CGA stated that the large amounts of smoke that

would be created by burning diesel fuel are contrary to the

environmental objectives of developing CNG vehicles. NGVC and Norris

suggested using a CNG or propane grill for the test.

In the final rule, NHTSA decided to specify the use of No. 2 diesel

fuel. The agency explained that it was aware of the environmental

problems associated with this type of fuel and would further study

whether other fuels should be used to generate the bonfire test.

However, the agency stated that until it could determine that a

different fuel is an appropriate (e.g., generates a fire of comparable

heat and intensity) replacement for No. 2 diesel fuel, that fuel will

be specified for generating the bonfire.

NHTSA has decided to propose to amend the bonfire test conditions

to allow alternative types of fuel, given the environmental

difficulties resulting from No. 2 diesel fuel. One alternative would be

to allow manufacturers to conduct the test with any fuel that generates

a flame temperature equivalent to that of No. 2 diesel fuel. Under this

alternative, any fuel that generates a flame temperature of 850 deg. to

900 deg. C (the flame temperature of No. 2 diesel fuel) for the

duration of the test, would be permitted. To verify the flame

temperature of 850 deg. to 900 deg. C for a period of 20 minutes, or

until the container is fully vented or fails, three thermocouples would

be located on the container's bottom, 102 mm above the fuel surface, as

measured before the fire is started. The thermocouples would be placed

so that one would be at the center of the container's bottom and one on

each side of the container where the dome and sidewall intersect. NHTSA

requests comments about the appropriateness of this alternative,

including the use of flame temperature to define ``equivalence'' among

fuel types. Would a different fuel characteristic such as Btu/lb be

more appropriate? If a commenter believes that an alternative approach

would be more appropriate, it should submit the test procedures

associated with such an alternative.

H. Labeling Requirements

1. CNG Containers

a. Labeling information. In the NPRM, NHTSA proposed to require

that container manufacturers certify that each of their containers

comply with the proposed equipment requirements by permanently labeling

the container with the following information: The symbol ``DOT'' to

constitute a certification by the manufacturer that the container

conforms to all requirements of the standard; the date of manufacture

of the container; the name and address of the container manufacturer;

and the maximum service pressure. The agency stated that labeling the

container would provide vehicle manufacturers and consumers with

assurance that they are purchasing containers that comply with the

Federal safety standards. In addition, the agency believed that the

proposed requirement would facilitate the agency's enforcement efforts

by providing a ready means of identifying the container and its

manufacturer.

EDO, NGVC, Thomas, NYCFD, and Volvo GM addressed the proposed

labeling requirements. EDO and NYCFD stated that the label should

include the maximum fill pressure at a location close to the fill

receptacle. NGVC recommended that a blank area for the container

installation date be included in the label to be filled in by the

installer. Volvo GM stated that only containers manufactured after the

standard's effective date should be entitled to display the DOT symbol.

Thomas stated, without elaboration, that the labeling requirements of

NGV2 should be adopted. NHTSA's proposal did not include certain

information specified in NGV2, including the type of container,

inspector symbols, trademarks, manufacturers's part number, and serial

numbers.

In the CNG container final rule, NHTSA decided to adopt the

proposed labeling requirements with a slight modification from the

proposed format. In item (a), the agency modified the proposal which

states ``The tank manufacturer's name and address'' to state the

following: include the statement that ``If there is a question about

the proper use, installation, or maintenance of this container, contact

[manufacturer's name, address, and telephone number].'' In the final

rule, the agency decided not to require the other additional items of

information in NGV2 since the agency had not proposed requiring such

information. Notwithstanding the agency's decision not to require this

additional information, the agency explained that a manufacturer may

list such information on the label, provided that the additional

information does not obscure or confuse the required information. In

particular, NHTSA urged manufacturers to include the container type,

e.g., Type 1, 2, 3 or 4, since the agency had adopted NGV2's design and

material specifications in the final rule. The agency believed that

specifying the type of container would facilitate oversight of

compliance tests since each type of container is required to undergo a

hydrostatic burst test with a safety factor unique to that type.

In the final rule, NHTSA also explained that it anticipated

proposing additional requirements about the CNG fuel container's label.

The agency is now proposing to amend S7.4 to specify that CNG

containers be labeled with the following additional information:

(1) The container designation (Type 1, 2, 3, or 4),

(2) The statement ``CNG ONLY,''

(3) The statement: ``This container should be visually inspected

after a motor vehicle accident or fire and at least every 36 months for

damage and deterioration in accordance with the Compressed Gas

Association (CGA) guidelines C-6 and C-6.1 for Type 1 containers and C-

6.2 for Types 2, 3, and 4 containers.''

(4) The statement: ``Do Not Use After ____________,'' inserting the

year that is the 15th year beginning after the year in which the

container is manufactured.

NHTSA believes that it would be in the interest of motor vehicle

safety to add this information to the CNG container label. Adding

information about container type, e.g., Type 1, 2, 3 or 4 would be

consistent with the agency's adoption of NGV2's design and material

specifications in the CNG final rule. The agency believes that

specifying the type of container would facilitate oversight of

compliance tests since each type of container is required to undergo a

hydrostatic burst test with a safety factor unique to that type. Adding

the phrase ``CNG ONLY'' would assure that CNG containers are used only

for CNG and are not used for other fuels for which the containers were

not designed, such as liquefied petroleum gas (LPG).

Since NHTSA has no statutory authority to require the periodic

inspection of CNG containers after the first consumer purchase, adding

information about periodic inspections would help assure their safe use

after this time. Such statements would alert owners to the desirability

for reinspection over time or in the event of an accident. The agency

notes that the proposed requirement is consistent with NGV2's

guidelines for visual inspection of CNG containers every 36 months.

Reference to the CGA guidelines would provide standardized criteria by

which to inspect containers built by different manufacturers. The

agency is proposing use of the visual inspection guidelines contained

in CGA C-6, C-6.1, and C-6.2, and not those for hydrostatic testing. In

addition to the proposal that the container be inspected after an

accident or at least every 36 months, NHTSA requests comments about the

need to specify both a time interval and a mileage interval (e.g., the

agency could require the following statement: ``This container should

be visually inspected after a motor vehicle accident or fire, and for

damage or deterioration at least every 36 months or 36,000 miles,

whichever comes first, in accordance with . . .''). What time and

mileage intervals would be most appropriate? Would an agency

requirement for inspection every 12 months be appropriate?

NHTSA is proposing to require information about the container's

service life in the belief that this information would help assure that

a CNG container is removed from service after its design service life

expires. As commenters on the NPRM stated, this is especially important

since there is a finite period during which CNG containers can be used

safely. The agency is proposing 15 years because CNG containers built

to follow NGV2 have a design service life of 15 years. Nevertheless,

since containers may be built for a service life other than 15 years,

the agency would allow a manufacturer to specify the service life

length appropriate to its containers.

The agency requests comments about the need for each of these

proposed items of information and alternative ways to specify this

information.

b. Label location. In response to the NPRM, EDO and NYCFD stated

that the label should include certain labeling information such as the

maximum fill pressure at a location close to the fill receptacle.

NHTSA has decided to propose requirements related to the label's

location. Accordingly, the agency has decided to propose that the

containers be installed in a manner that ensures the visibility of the

container labeling. Specifically, the agency is proposing to require

the label to be near the end of the container containing the outlet

valve, since such a location would help ensure that the label would be

more visible during refueling. The agency notes that NGV2 contains a

similar requirement.

2. Vehicle labeling

The CNG vehicle final rule did not specify requirements for the

labeling of CNG fueled vehicles. In this SNPRM, the agency is proposing

to amend Standard No. 303 to include two items of information.

S5.3.1 The statement: ``Maximum service pressure ________ kPa

(________ psig).''

S5.3.2 The statement ``See instructions on fuel container for

inspection and service life.''

The agency believes that the first item of information would help

assure that CNG containers are not overfilled during refueling. The

second item is intended to assure that vehicle owners and operators are

informed about the important safety information on container

inspection. In addition, the agency is proposing that for vehicles

manufactured or converted prior to the first sale to the consumer, the

manufacturer provide this information in writing to the consumer,

either in the owner's manual or on a one page statement. The agency

requests comments about the need for vehicle labeling and written

information bearing this and other information.

I. Other Safety Information

NHTSA requests comments on the following additional issues related

to the safe performance of CNG containers. What are the safety

implications of fast-filling CNG containers during refueling, which can

result in pressure levels of 125 percent of service pressure due to the

heat of pressurization? Do the initial permeation rates of CNG

containers constructed of nonmetallic liners remain constant over the

life of the container? What are the consequences of gas permeation from

vehicles fueled by multiple CNG containers? What are the degradation

characteristics of vinyl esters and thermoplastic resins for composite

material? Should containers and container liners have longitudinal or

circumferential welds?

J. Leadtime

NHTSA is proposing to make the requirements in this notice

effective one year after publication of the final rule in the Federal

Register. The agency believes this would be a reasonable time period

for container manufacturers to test their containers and certify

compliance to the additional tests being proposed in this notice. The

agency anticipates that container manufacturers would readily be able

to certify compliance to the proposed requirements. This is because

container manufacturers already certify compliance with NGV2, which is

essentially consistent with the proposed requirements. The one

exception is the proposed salt spray test. The agency requests comments

about the leadtime. Does one year provide sufficient time for

manufacturers to certify compliance to the proposed requirements? Would

the addition of the proposed salt spray test require a longer leadtime

than one year?

In the meantime, prior to the standard's effective date, the

industry is free to advertise containers as meeting the CNG equipment

standard that will take effect in one year. Manufacturers have sought

to achieve early compliance with other agency requirements\7\ such as

those relating to dynamic side impact protection and air bags. The

agency encourages manufacturers to seek, to the extent feasible, to

manufacture their CNG containers to meet these new requirements before

the date the standard takes effect.

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\7\However, the agency emphasizes that a manufacturer may not

certify a container as meeting the equipment standard until the

standard goes into effect. Under the statte, a certification is a

statement that a vehicle or item of equipment meets all applicable

Federal Motor Vehicle Standards that are then in effect. Therefore,

until a standard is effective, manufacturers may not certify

compliance with it.

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K. Benefits

As explained earlier, NHTSA anticipates that the number of CNG fuel

vehicles will increase greatly in the near future, in light of

directives by the Clinton Administration and legislation by Congress to

develop vehicles powered by cleaner burning fuels. This notice will

enhance the safety of this growing population of vehicles, since CNG

containers will be required to comply with the tests in Standard No.

304. The necessity for certifying compliance with the Federal

requirements will provide added assurance that the containers are safe.

The benefits of the proposal to issue additional requirements

applicable to CNG containers are to provide assurances of the

structural integrity of the CNG containers. The agency is adding one

test not currently part of NGV2 (the salt spray test) to simulate

environmental roadway conditions. In addition, by helping to minimize

any safety concerns associated with CNG vehicles, this rule should

result in positive environmental impacts.

L. Costs

For six of the seven tests proposed, there would be no additional

costs of upgrading current containers to comply with the proposed

requirements, since CNG container manufacturers already comply with

NGV2. Similarly, there would be no additional compliance test costs for

these six tests, since the manufacturers already meet the NGV2 tests.

Testing and container costs for these six tests are estimated to range

from $13,800 to $30,650 per container size and type. The agency does

not know whether existing containers can meet the proposed salt spray

test, and what costs might be incurred if the containers do not meet

the proposed test. The agency estimates that the testing and container

cost for the salt spray test to range from $1,220 to $4,130. Total

testing and container cost for the proposal are $15,020 to $34,780. The

agency has made the criteria in some of the tests more objective than

NGV2 by changing unacceptably subjective and broad terms to more

measurable and therefore more objective criteria.

Rulemaking Analyses and Notices

A. Executive Order 12866 (Federal Regulation) 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 not reviewed

under E.O. 12866, ``Regulatory Planning and Review.'' This action has

been determined to be ``nonsignificant'' under the Department of

Transportation's regulatory policies and procedures. NHTSA has

estimated the costs of the amendments in a Preliminary Regulatory

Evaluation (PRE) which has been placed in the docket for this

rulemaking. As discussed in that document, NHTSA estimates that total

testing and container costs for this proposal are $15,020 to $34,780

per container size and type. The agency believes that a CNG container

which meets the current industry standard, NGV2, would also comply with

the requirements of this proposal, with the exception of the salt spray

test.

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 would not have a significant

economic impact on a substantial number of small entities. For six of

the seven tests, there will be no small business impacts since the

proposed standards are already being met. Comments are requested on

current compliance with the salt spray test and whether this would have

small business impacts. Information available to the agency indicates

that the businesses manufacturing CNG fuel containers are not 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 would not have sufficient Federalism

implications to warrant the preparation of a Federalism Assessment. No

state has adopted requirements regulating CNG containers.

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 would have no adverse impact on the

quality of the human environment. On the contrary, because NHTSA

anticipates that ensuring the safety of CNG vehicles would encourage

their use, NHTSA believes that the rule would 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

The proposal 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 submission of a

petition for reconsideration or other administrative proceedings before

parties may file suit in court.

Public Comments

Interested persons are invited to submit comments on the proposal.

It is requested but not required that 10 copies be submitted.

All comments must not exceed 15 pages in length. (49 CFR 553.21).

Necessary attachments may be appended to thee submissions without

regard to the 15-page limit. This limitation is intended to encourage

commenters to detail their primary arguments in a concise fashion.

If a commenter wishes to submit certain information under a claim

of confidentiality, three copies of the complete submission, including

purportedly confidential business information, should be submitted to

the Chief Counsel, NHTSA, at the street address given above, and seven

copies from which the purportedly confidential information has been

deleted should be submitted to the Docket Section. A request for

confidentiality should be accompanied by a cover letter setting forth

the information specified in the agency's confidential business

information regulation. 49 CFR Part 512.

All comments received before the close of business on the comment

closing date indicated above for the proposal will be considered, and

will be available for examination in the docket at the above address

both before and after that date. To the extent possible, comments filed

after the closing date will also be considered. Comments received too

late for consideration in regard to the final rule will be considered

as suggestions for further rulemaking action. The NHTSA will continue

to file relevant information as it becomes available in the docket

after the closing date, and it is recommended that interested persons

continue to examine the docket for new material.

Those persons desiring to be notified upon receipt of their

comments in the rules docket should enclose a self-addressed, stamped

postcard in the envelope with their comments. Upon receiving the

comments, the docket supervisor will return the postcard by mail.

List of Subjects in 49 CFR Part 571

Imports, Incorporation by reference, Motor vehicle safety, Motor

vehicles, Rubber and rubber products, Tires.

In consideration of the foregoing, the agency proposes to amend

Standard No. 303; Fuel System Integrity of Compressed Natural Gas

Vehicles and Standard No. 304: Compressed Natural Gas Fuel Container

Integrity, in Title 49 of the Code of Federal Regulations at Part 571

as follows:

PART 571--[AMENDED]

1. The authority citation for Part 571 would continue to read as

follows:

Authority: 49 U.S.C. 322, 30111, 30115, 30117 and 30166;

delegation of authority at 49 FR 1.50.

Sec. 571.303 [Amended]

2. In Sec. 571.303, S5 would be amended to add S5.3 through S5.3.2

and S5.4 which would read as follows:

* * * * *

S5.3 Each CNG vehicle shall be permanently labeled, near the

vehicle refueling connection, with the information specified in S5.3.1

and S5.3.2. The information shall be visible during refueling, in

English, and in letters and numbers that are not less than 4.76 mm (3/

16 inch) high.

S5.3.1 The statement: ``Maximum service pressure ________ kPa

(________ psig).''

S5.3.2 The statement ``See instructions on fuel container for

inspection and service life.''

S5.4 When a motor vehicle is delivered to the first purchaser for

purposes other than resale, the manufacturer shall provide the

purchaser with a written statement of the information in S5.3.1 and

S5.3.2 in the owner's manual, or, if there is no owner's manual, on a

one-page document. The information shall be in English and in not less

than 10 point type.

* * * * *

3. Section 571.304, Standard No. 304; Compressed Natural Gas Fuel

Container Integrity, would be amended by revising S7.4, adding S7.5

through S7.11, revising S8.3.2 through S8.3.4, S8.3.6, and S8.3.7, and

adding S8.5 through S8.11.3, to read as follows:

Sec. 571.304 Standard No. 304, Compressed natural gas fuel container

integrity.

* * * * *

S7.4. Labeling. Each CNG fuel container shall be permanently

labeled, within 30.5 cm (12 inches) of the end of the container

containing the outlet valve, with the information specified in

paragraphs (a) through (h) of this section. The information shall be in

English and in letters and numbers that are at least 12.7 mm (\1/2\

inch) high.

(a) The statement: ``If there is a question about the proper use,

installation, or maintenance of this container, contact

______________,'' inserting the CNG fuel container manufacturer's name,

address, and telephone number.

(b) The statement: ``Manufactured in ________,'' inserting the

month and year of manufacture of the CNG fuel container.

(c) The statement: ``Maximum service pressure ________ kPa, ______

psig).''

(d) The symbol DOT, constituting a certification by the CNG

container manufacturer that the container complies with all

requirements of this standard.

(e) The container designation (e.g., Type 1, 2, 3, 4).

(f) The statement: ``CNG Only.''

(g) The statement: ``This container should be visually inspected

after a motor vehicle accident or fire and at least every 36 months for

damage and deterioration in accordance with the Compressed Gas

Association (CGA) guidelines C-6 and C-6.1 for Type 1 containers and C-

6.2 for Types 2, 3, and 4 containers.''

(h) The statement: ``Do Not Use After ____________,'' inserting the

year that is the 15th year beginning after the year in which the

container is manufactured.

* * * * *

S7.5 Environmental cycling test. Each CNG fuel container shall not

leak or permanently change in external configuration or dimensions,

when tested in accordance with S8.5.

S7.6 Charpy impact test. Each steel container and each steel liner

shall comply with the requirements of this section. When three 5 x 10

mm specimens of a steel container or steel liner are tested in

accordance with S8.6--

S7.6.1 Each specimen shall absorb not less than 80 J/cm\2\ before

breaking.

S7.6.2 The average of the amounts of energy absorbed by the three

specimens before breaking shall be not less than 100 J/cm\2\.

S7.7 Gunfire test. Each CNG fuel container shall comply with this

section. When a container is tested in accordance with S8.7, no piece

exceeding 30 grams in mass shall separate from the container.

S7.8 Flaw tolerance test. When tested in accordance with S8.8,

each Type 2, Type 3, and Type 4 CNG fuel container shall not leak or

permanently change in external configuration or dimensions. In

addition, the cut made in accordance with S8.8 for the purpose of this

test shall not increase in length, width or depth as a result of this

test.

S7.9 Pendulum impact test. Each Type 2, Type 3, and Type 4 CNG

container shall not leak, when tested in accordance with S8.9.

S7.10 Drop test. Each CNG fuel container shall not leak, when

tested in accordance with S8.10.

S7.11 Road salt environmental test. Each CNG fuel container shall

not leak or permanently change in external configuration or dimensions,

when tested in accordance with S8.11.

* * * * *

S8.3.2 The CNG fuel container is positioned so that its

longitudinal axis is horizontal. Attach three thermocouples to measure

temperature on the container's bottom side along a line parallel to the

container longitudinal centerline. Attach one at the midpoint of the

container, and one at each end at the point where the dome end

intersects the container sidewall. Subject the entire length to flame

impingement, except that the flame shall not be allowed to impinge

directly on any pressure relief device. Shield the pressure relief

device with a metal plate.

S8.3.3 If the test container is 165 cm (65 inches) in length or

less, place it in the upright position. Attach three thermocouples to

measure temperature on the container's bottom side along a line which

intersects the container longitudinal centerline. Attach one at the

midpoint of the bottom of the container, and one each at the point

where the dome end intersects the container sidewall. Subject the

container to total fire engulfment in the vertical. The flame shall not

be allowed to impinge directly on any pressure relief device. For

containers equipped with a pressure relief device on one end, the

container is positioned with the relief device on top. For containers

equipped with pressure relief devices on both ends, the bottom pressure

relief device shall be shielded with a metal plate.

S8.3.4 The lowest part of the container is suspended at a distance

above the fire such that the container bottom surface temperatures

specified in S8.3.6 are achieved.

* * * * *

S8.3.6 The fire is generated by any fuel that generates a flame

temperature between 850 deg. and 900 deg.C for the duration of the

test, as verified by each of the three thermocouples in S8.3.2 or

S8.3.3.

S8.3.7 The fuel specified in S8.3.6 is such that there is

sufficient fuel to burn for at least 20 minutes. To ensure that the

sides of the fuel container are exposed to the flame, the surface area

of the fire on a horizontal plane is such that it exceeds the fuel

container projection on a horizontal plane by at least 20 cm (8 inches)

but not more than 50 cm (20 inches).

* * * * *

S8.5 Environmental cycling test procedures.

S8.5.1 Adjust a pass/fail gauge to fit the container before the

test.

S8.5.2 After the removal of any protective coating or temporary

coating such as oil or grease, a CNG fuel container is cycle tested as

follows:

S8.5.2.1 Precondition the container's interior as follows: Fill

container \1/2\ full with water, pressurize container to 1.0 psi with

hydrogen sulfide, increase pressure to 50 psi with carbon dioxide, then

increase pressure to 67 percent of the service pressure with automotive

grade natural gas. Maintain the pressure at room temperature for 15

days, then increase the room temperature to 60 deg.C (140 deg.F) and

hold for 15 days. Depressurize the container, drain and dry. Add an

amount of compressor oil sufficient to coat the interior surfaces of

the container. Pressurize to 67 percent of the service pressure using

automotive grade natural gas and hold for 15 days at 60 deg.C (140

deg.F) room temperature. Depressurize the container.

S8.5.2.2 Condition the container for 48 hours at zero pressure, 60

deg.C (140 deg.F) and 95 percent relative humidity. To obtain the

specified temperature and relative humidity, spray with a fine spray or

mist of water at 60 deg.C (140 deg.F) in a chamber held at 60 deg.C

(140 deg.F).

S.8.5.2.3 For 5,000 cycles at 60 deg.C (140 deg.F) and 95

percent relative humidity, hydrostratically pressurize the container

from (1) a level not more than 10 percent of the service pressure, to

(2) 125 percent of the service pressure.

S8.5.2.4 Stabilize at zero pressure and ambient conditions.

S8.5.2.5 For 5,000 cycles at -40 deg.C (-40 deg.F),

hydrostatically pressurize the container from (1) a level not more than

10 percent of the service pressure to (2) the service pressure.

S8.5.2.6 The cycling rate does not exceed 10 cycles per minute.

S8.5.3 Determine that the container has not leaked or permanently

changed in external configuration or dimension. With respect to changes

in the container's external configuration or dimension, adjust a pass/

fail gauge to fit the container. Compare the measurement with the one

in S8.5.1.

S8.6 Charpy impact test procedures.

S8.6.1 Cut one set of three longitudinal 5X10 mm Charpy Vee notch

specimens from one container or liner. Each specimen is then tested at

-40 deg. C (-40 deg. F) in accordance with the Methods for Notched Bar

Impact Testing of Metallic Materials, ASTM E 23.

S8.7 Gunfire test procedures. A container is pressurized with

nitrogen or air to service pressure. The container is then impacted by

a 0.30 caliber armor-piercing projectile having a muzzle velocity of

853 meter/second (2,800 feet/second). The container is positioned so

that the projectile impact point is in the container sidewall, with the

trajectory passing through the container longitudinal centerline at an

angle of 45 degrees and exiting through the opposite sidewall. The

distance from the muzzle to the test container is 46 m (50 yards).

S8.8 Flaw tolerance test procedures.

S8.8.1 Adjust a pass/fail gauge to fit the container before the

test.

S8.8.2 Make a 25.4 mm (1 inch) long longitudinal cut into the

outer wall of a CNG test container at its midlength. The cut's depth is

0.75 mm (0.030 inch) and width is 0.75 mm.

S8.8.3 For 1,5000 cycles at ambient temperature, hydrostatically

pressurize the container from (1) a level not more than 10 percent of

the service pressure, to (2) the service pressure.

S8.8.4 Determine that the container has not leaked or permanently

changed in external configuration or dimension. With respect to changes

in the container's external configuration or dimension, adjust a pass/

fail gauge to fit the container. Compare the measurement with the one

in S8.5.1 or S8.81.

S8.9 Pendulum impact test procedures.

S8.9.1 The container is empty and at 21 deg.C (70 deg.F).

S8.9.2 A pendulum impact testing fixture is used for the test. The

impact body is a steel pyramid with equilateral triangle faces and a

square base. The summit and the edges of the pyramid are rounded to a

radius of 3 mm (0.12 inch). The center of percussion of the pendulum

coincides with the center of gravity of the pyramid. The center's

distance from the axis of rotation of the pendulum is 1 meter (40

inches). The total mass of the pendulum referred to its center of

percussion is 15 kg (33 pounds). The energy of the pendulum at the

moment of impact is not less than 30 Nm (22.1 ft-lbf).

S8.9.3 During the test, the container is held in position by the

end bosses or by the mounting brackets.

S8.9.4 The impact body strikes the test container at any point and

any angle on the container.

S8.9.5 For 1,500 cycles at ambient temperature, hydrostatically

pressurize the container from (1) a level not more than 10 percent of

the service pressure to (2) the service pressure.

S8.9.6 Determine that the container has not leaked.

S8.10 Drop test procedures.

S8.10.1 The container is drop tested at ambient temperature

without internal pressurization or attached valves. The container is

held in a horizontal position with the bottom 3.05 meters (10 feet)

above the surface onto which it is dropped. The surface is a smooth,

horizontal concrete pad or flooring that is 4 inches thick.

S8.10.2 For 5,000 cycles at ambient temperature, hydrostatically

pressurize the container from (1) a level not more than 10 percent of

the service pressure to (2) 125 percent of the service pressure, and

then for 13,000 cycles from (1) a level not more than 10 percent of the

service pressure to (2) the service pressure.

S8.10.3 Determine that the container has not leaked.

S8.11 Road salt environmental test procedures.

S8.11.1 Adjust a pass/fail gauge to fit the container before the

test.

S8.11.2 A CNG fuel container, free of any protective coating, is

cycle tested as follows:

S8.11.2.1 Subject the container to a salt spray (fog) test in

accordance with ASTM B-117-73, ``Method of Salt Spray (Fog) Testing,''

for 240 hours consisting of ten successive 24 hour periods. During each

period, the container shall be mounted in the middle of the chamber and

exposed for 23 hours to the salt spray. The spray is not activated

during the 24th hour.

S8.11.2.2 For 5,000 cycles at ambient conditions, hydrostatically

pressurize the container from (1) a level not more than 10 percent of

the service pressure to (2) 125 percent of the service pressure.

S8.11.2.3 Stabilize at zero pressure and ambient conditions.

S8.11.2.4 For 5,000 cycles at -40 deg. C (-40 deg. F),

hydrostatically pressurize the container from (1) a level not more than

10 percent of the service pressure to (2) the service pressure.

S8.11.2.5 The cycling rate does not exceed 10 cycles per minute.

S8.11.3 Determine that the container has not leaked or permanently

changed in external configuration or dimension. With respect to changes

in the container's external configuration or dimension, adjust a pass/

fail gauge to fit the container. Compare the measurement with the one

in S8.11.1.

Issued on: December 9, 1994.

Barry Felrice,

Associate Administrator for Rulemaking.

[FR Doc. 94-31016 Filed 12-16-94; 8:45 am]

BILLING CODE 4910-59-P