Federal Motor Vehicle Safety Standards; Compressed Natural Gas Fuel Containers

[[Page 37836]]

DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. 93-02; Notice 10]

RIN 2127-AF47

Federal Motor Vehicle Safety Standards; Compressed Natural Gas

Fuel Containers

AGENCY: National Highway Traffic Safety Administration (NHTSA),

Department of Transportation (DOT).

ACTION: Final rule, petitions for reconsideration.

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SUMMARY: This document responds to petitions for reconsideration of the

final rule that established performance requirements for compressed

natural gas (CNG) fuel containers. The final rule specified burst test

safety factors of up to 3.33 for use in evaluating the strength of

carbon fiber containers. In an initial notice responding to the

petitions, a single, lower safety factor of 2.25 was adopted, subject

to further consideration of that issue. This final rule reaffirms that

decision. Today's document also responds to the other issues raised in

the petitions.

DATES: Effective Date: August 23, 1995.

Petitions for Reconsideration: Any petition for reconsideration of

this rule must be received by NHTSA no later than August 23, 1995.

ADDRESSES: Petitions for reconsideration of this rule should refer the

Docket number referenced at the beginning of this document and should

be submitted to: Administrator, National Highway Traffic Safety

Administration, 400 Seventh Street, S.W., Washington, D.C. 20590.

FOR FURTHER INFORMATION CONTACT: Mr. Gary R. Woodford, NPS-01.01,

Special Projects Staff, Office of Safety Performance Standards,

National Highway Traffic Safety Administration, 400 Seventh Street SW.,

Washington, D.C. 20590 (Telephone 202-366-4931) (FAX 202-366-4329).

SUPPLEMENTARY INFORMATION:

I. Final Rule Establishing FMVSS No. 304

II. Petitions for Reconsideration

III. December 1994 Final Rule Responding to Petitions for

Reconsideration

IV. Further Response to Petitions for Reconsideration

A. Carbon Fiber Safety Factors

B. Other Issues

1. Burst Pressure Definition

2. Container and Material Requirements

a. NASA Computer Program

b. Autofrettage Requirement

c. Reference to S5.7.3

d. Container Liner Burst Test

e. Check Analysis Tolerances for Materials

f. Wall Stress Formula

g. Service Pressure vs. Hydrostatic Pressure in Stress Formula

3. Performance Requirements

a. Hydrostatic Test

b. Burst Pressure vs. Fiber Stress Ratio

c. Fiberglass Stress Ratios: Type 2 Containers

4. Labeling Requirements

a. Letter Height

b. Container Label Permanency

c. Fill Pressure

d. Service Pressure

e. ``DOT'' Symbol

f. Service Life

g. Qualification/Batch Test Requirements

5. Test Conditions

a. Diesel Fuel in Bonfire Test

b. More Detail In Bonfire Test

c. Complete Venting of Container During Bonfire Test

d. Burst and Pressure Cycling Test Procedures

6. Miscellaneous

a. Withdraw or Delay the Effective Date of FMVSS 304

b. Flexibility and Adaptability of Final Rule

c. Chemical Compositions

V. Rulemaking Analysis

I. Final Rule Establishing FMVSS No. 304

On September 26, 1994, NHTSA published a final rule addressing the

safe performance of compressed natural gas (CNG) containers 1 (59

FR 49010). The final rule established a new Federal motor vehicle

safety standard (FMVSS) FMVSS No. 304, Compressed Natural Gas Fuel

Container Integrity, that specifies pressure cycling, burst, and

bonfire tests for the purpose of ensuring the durability, initial

strength, and venting of CNG containers. The 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 entire service life. The 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. The

bonfire test evaluates a container's ability to relieve internal

pressure, primarily pressure due to temperature rise. In addition, the

final rule specifies labeling requirements for CNG fuel containers.

FMVSS No. 304 took effect on March 27, 1995.

\1\ When used as a motor fuel, natural gas is stored on-board a

vehicle in cylindrical containers at a pressure of approximately

20,684 kPa (3,000 psi). Among the terms used to describe CNG fuel

containers are tanks, containers, cylinders, and high pressure

vessels. The agency will refer to them as ``containers'' throughout

this document.

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The new FMVSS is patterned after the American National Standards

Institute's (ANSI's) voluntary industry standard known as ANSI/NGV2.

ANSI/NGV2 and FMVSS No. 304 specify detailed material and other

requirements for four different types of containers. 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 sidewall. 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.

For each type of container, ANSI/NGV2 and FMVSS No. 304 specify a

unique safety factor for determining the internal hydrostatic pressure

that the container must withstand during the burst test. The safety

factors range from 2.25 to 3.50, depending on the material and design

involved. The higher the safety factor, the more material is needed to

comply with the requirement. To satisfy this aspect of ANSI/NGV2 and

FMVSS No. 304, a container must meet the applicable material and

manufacturing requirements as well as the burst test.

While FMVSS No. 304 followed ANSI/NGV2 in most respects, it

departed from ANSI/NGV2 in requiring that carbon fiber containers

comply with the burst tests based on higher safety factors.

Specifically, the final rule establishing FMVSS No. 304 specified a

safety factor of 2.50 for Type 2 containers and 3.33 for Type 3 and

Type 4 containers. In contrast, ANSI/NGV2 specifies a safety factor of

2.25 for all carbon fiber containers.

II. Petitions for Reconsideration

NHTSA received 133 petitions for reconsideration of the final rule

that established FMVSS No. 304. The petitions were submitted by CNG

container manufacturers, vehicle manufacturers, natural gas utilities,

research and testing laboratories, and Canada and several of its

provincial governments.

Most of the petitioners addressed the carbon fiber safety factors.

Many of them stated that the levels specified by the agency in the

final rule are higher

[[Page 37837]]

than warranted by safety considerations. They further stated that the

higher safety factors will unduly increase the cost of carbon fiber

containers and make them noncompetitive with other technologies. Some

petitioners stated that NHTSA's safety factors are not harmonized with

the Canadian Standards Association (CSA) standard (Canadian B51 Part

II) or with the 1993 draft International Standards Organization (ISO)

standard (ISO/TC 58/SC 3/WG 17), both of which specify a 2.25 safety

factor for carbon fiber containers. On the other hand, only one

commenter supported the 3.33 safety factor.

While the carbon fiber safety factors were the most controversial

issue raised by petitioners, some petitioners requested changes to

other aspects of the final rule. For example, some petitioners

expressed concern that FMVSS No. 304 prohibits certain materials, such

as new or different aluminum and steel alloys or other new materials.

Some petitioners wanted FMVSS No. 304 to include additional safety

requirements found in ANSI/NGV2. A number of petitioners requested the

agency to delay or withdraw FMVSS No. 304 until the current revision of

ANSI/NGV2 is completed. Petitioners also raised questions about the

need for certain technical amendments to FMVSS No. 304.

NHTSA has responded to the petitions for reconsideration by issuing

two different notices. The two-step approach to responding to the

petitions was necessary to provide immediate regulatory relief by

allowing the manufacture of carbon fiber containers, subject to a

single safety factor of 2.25. This approach also provided NHTSA an

opportunity to review and analyze all the information presented in the

petitions for reconsideration.

III. December 1994 Final Rule Responding to Petitions for

Reconsideration

In an initial notice responding to petitions for reconsideration

published on December 28, 1994, the agency established a burst test

safety factor of 2.25 for carbon fiber containers, and indicated that

it would issue a final determination about the appropriate burst test

safety factor pending completion of the reconsideration process. (59 FR

66773) That notice also responded to several other technical issues

whose resolution did not necessitate extensive review or consideration.

In today's notice, the agency sets forth a final determination about

the safety factor for carbon fiber containers and responds to the

balance of the issues in the petitions for reconsideration.

IV. Further Response to Petitions for Reconsideration

A. Carbon Fiber Safety Factors

In the September 1994 final rule, NHTSA departed from ANSI/NGV2 and

established higher safety factors for carbon fiber containers. The

agency made this determination because at that time the agency was not

aware that these containers were being used extensively in motor

vehicle applications. The agency stated that adopting more stringent

safety factors is consistent with the longstanding approach taken by

the Research and Special Programs Administration (RSPA) 2 to

initially adopt conservative requirements in response to the uncertain

level of risk posed by new technologies and subsequently modify the

requirements if further real-world safety data become available

supporting less stringent regulations. The agency indicated that it

would consider reducing the safety factors for carbon fiber containers

if data supporting a reduction ``are developed and become available on

the use of carbon fiber containers in motor vehicle applications.''

\2\ RSPA is an administration within the United States

Department of Transportation whose functions include regulating the

transportation of hazardous materials.

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In response to the final rule, CNG container manufacturers and

other petitioners have submitted new test data and information

indicating that carbon fiber containers at the lower 2.25 safety factor

can provide a level of performance equal to that of other materials

built to higher safety factors. This information also indicated that

implementing higher safety factors for carbon fiber would make carbon

fiber containers noncompetitive because of the higher costs associated

with adding additional material to meet the higher safety factors. The

data include information on tests and analyses of carbon fiber

containers, the number of containers in use in motor vehicle

applications, and cost and weight information.

Several petitioners, particularly Brunswick Technical Group and EDO

Corp., submitted test data which indicate that carbon fiber containers

that comply with ANSI/NGV2 are safe. Brunswick stated that it has

qualified 26 different configurations of its carbon fiber containers

under ANSI/NGV2 requirements and has destructively tested 500 carbon/

fiberglass CNG containers.3 That manufacturer further stated that

there is no information indicating that carbon fiber containers that

comply with ANSI/NGV2 requirements have failed in the field or that

test data would indicate the likelihood of such failure. To illustrate

its claim, Brunswick provided the results of tests recently performed

by British Gas on its containers.

\3\ Brunswick's design uses carbon as the major load carrying

fiber with a small layer of fiberglass outside.

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EDO also provided extensive testing information and analyses about

its carbon fiber containers built to the 2.25 safety factor. EDO

submitted an analysis showing how its container meets the requirements

of a draft industry-wide guideline for the performance of CNG

containers used in a motor vehicle environment. The guideline, which

was developed by General Motors (GM) following failures of CNG

containers on two GM pickup trucks in 1994, includes requirements for

performance relative to contaminants, corrosives, crashworthiness, leak

integrity, fire resistance, reliability, dependability, and accelerated

aging. The results of the analysis indicate that EDO's carbon fiber

containers built to the 2.25 safety factor comply with these

requirements.

EDO also provided a detailed analysis, known as a Failure Modes and

Effects Analysis (FMEA),4 which it performed to determine the

safety risks of its carbon fiber containers built to ANSI/NGV2

requirements. This analysis led EDO to conclude that no significant

safety risk could be identified for the carbon fiber containers.

Specifically, EDO cited the significantly long fatigue life and high

resistance to stress rupture of carbon fiber, which are evaluated by

the burst test. EDO also cited additional test data that it believes

indicate that no further requirements are needed with respect to

container strength.

\4\ A FMEA sets out in writing each failure mode that is

possible with a product along with the potential cause for the

failure and the design control in place to counter the failure. RSPA

sometimes requires a FMEA to be submitted when it evaluates a

manufacturer's particular container design. NHTSA believes that FMEA

is a valid technique for assessing the adequacy of a particular

design, provided that other supporting information is presented.

Several petitioners supplied information favorably comparing the

performance (under both real world and laboratory test conditions) of

carbon fiber containers subject to the 2.25 safety factor with

fiberglass containers. Based on an evaluation that Powertech conducted

for Transport Canada, Powertech concluded that carbon fiber resists

stress rupture, and

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environmental and fire effects better than fiberglass.

Several petitioners stated that carbon fiber containers subject to

the 2.25 safety factor are being used safely in real world situations.

Thomas Built Buses, Inc., reported that there have been several

thousand carbon fiber CNG containers built to ANSI/NGV2 requirements,

i.e., subject to a safety factor of 2.25. Brunswick and EDO stated that

they have built over 5,000 carbon fiber containers to ANSI/NGV2

requirements (2,600 Brunswick and 2,500 EDO.) According to Brunswick,

many of these containers have been in service for at least 18 months,

including carbon fiber containers that have been used in buses in

Sweden for over five years.

Petitioners further stated that the higher carbon fiber safety

factors in FMVSS No. 304 are not harmonized with the standards being

set by others. For instance, Canada's CSA standard for CNG vehicle fuel

containers uses a 2.25 safety factor. Similarly, the draft ISO standard

for CNG containers incorporates the 2.25 safety factor. Moreover,

several organizations and States have incorporated ANSI/NGV2 into their

standards for CNG vehicles, including the National Fire Protection

Association, New York Department of Transportation, California Highway

Patrol, Texas Railroad Commission, and the State of Nebraska.

Many petitioners contended that the higher safety factors for

carbon fiber containers required by FMVSS No. 304 will make these

containers noncompetitive by unnecessarily increasing their cost and

weight, thereby inhibiting the growth of the natural gas vehicle

market. They noted that for a CNG container of a given size, the

increased safety factor not only increases the cost and weight, because

of the increased carbon fiber needed, but also reduces container

interior volume. The American Gas Association (AGA), the National Gas

Vehicle Coalition (NGVC), Brunswick, EDO, and Thomas each indicated

that these results have a significant impact on the motor vehicle

applications, particularly for buses and small passenger vehicles,

which are particularly weight sensitive.

These petitioners provided specific data on the cost and weight

impacts. AGA and NGVC stated that the higher safety factors in FMVSS

No. 304 will increase the cost of carbon fiber containers by 25 to 40

percent 5 and eliminate their weight advantage. EDO stated that

the higher safety factor for one of its carbon fiber containers would

result in a 38 percent (or $395) selling price increase and 32 percent

weight increase (approximately 25 pounds) for the same container

interior volume. EDO added that for a bus using 12 such containers,

this would result in a price increase of $4,740 for the containers

(excluding other costs such as OEM markup and changes to the mounting

brackets). Similarly, Brunswick stated that the agency's Final

Regulatory Evaluation (FRE) significantly understated the cost impact

of the higher safety factors, particularly for buses. That manufacturer

estimated that the incremental cost impact of the higher safety factors

would be $5,461 per bus, not $1,240 to $2,483 as estimated by the

agency. Thomas Built stated that the high strength, light-weight carbon

fiber container has made its bus applications more practical by

increasing passenger capacity by six persons over what is possible with

steel/fiberglass containers, since a smaller carbon fiber CNG container

has approximately the same internal capacity as a larger steel/

fiberglass container.

\5\ Assuming that each CNG carbon fiber container built to the

2.25 safety factor costs approximately $1,000, costs would increase

between $250 and $400.

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Based on the information submitted in the petitions for

reconsideration and other available information, NHTSA has determined

that a 2.25 safety factor is more appropriate than the factors

originally established in September 1994 for carbon fiber CNG

containers. After analyzing this information, the agency believes that

the lower safety factor adopted in December 1994 is adequate to ensure

that carbon fiber CNG containers will have sufficient strength to

perform in a motor vehicle environment. The test data and information

on real-world experience supplied by the petitioners appear to support

the agency's determination that a 2.25 safety factor is appropriate.

During that time, there have been no known failures. NHTSA further

notes that the 2.25 safety factor harmonizes with the value specified

in ANSI/NGV2 and in the CSA standard. The agency also agrees with the

petitioners that the higher safety factor adopted in the final rule

would have significantly increased the cost and weight associated with

carbon fiber containers, even though the 2.25 safety factor now appears

adequate to ensure their safety. In conclusion, NHTSA has determined

that adopting the 2.25 safety factor is sufficient to ensure safety.

Thus, the safety factor or stress ratio, for each fiber material in a

fuel container will be as defined in FMVSS No. 304 for that fiber, with

the stress ratio for carbon fiber being 2.25.

B. Other Amendments

In the petitions for reconsideration, ten petitioners--Ford,

Pressed Steel Tank (PST), Norris, Structural Composites Industries

(SCI), Compressed Gas Association (CGA), NGV Systems, the Flxible Corp,

Powertech Labs, Brunswick, and Chrysler--requested a variety of

amendments to FMVSS No. 304. Each requested modification, along with

the agency's analysis of the desirability of the requested

modification, is discussed below.

1. Definitions for Burst Pressure

SCI recommended that the reference to temperature in the definition

of burst pressure be in terms of ambient temperature, rather than 70

deg.F, since the current reference implies to the petitioner that the

burst test must be performed at 70 deg.F. Section S4 defines burst

pressure as ``* * * the highest internal pressure reached in a CNG fuel

container during a burst test at a temperature of 21 deg.C (70

deg.F).''

NHTSA has decided not to adopt SCI's request to modify the

definition for burst pressure. Neither NHTSA nor NGV2 specifies the

temperature at which the burst test needs to be conducted. The agency

further notes that SCI provided no other rationale to justify this

modification, and no other petitioner commented that the definition was

inappropriate. Further, the definition for burst pressure in S4 is

consistent with that of ANSI/NGV2, which represents a consensus of the

natural gas vehicle industry. Therefore, adopting the requested

modification might cause confusion for manufacturers.

2. Container and Material Requirements

a. NASA computer program. NGV Systems, SCI, Powertech, and PST

petitioned the agency to correct the name and statement about the

availability of the National Aeronautics and Space Administration

(NASA) computer program referenced in S5.5.1 and Part 571.5(b)(9).

NHTSA has adopted the requested amendments to S5.5.1 and Part

571.5(b)(9), since the agency, in the final rule, used an incorrect

title and erroneously stated that it was available from NASA. The

computer program's correct title is ``Computer Program for the Analysis

of Filament-Reinforced Metal-Wound Pressure Vessels.'' The program is

available from the National Technical Information Service,

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Springfield, Virginia as N67-12097 (NASA CR-72124).

b. Autofrettage requirement. Norris Cylinder Co. (Norris)

petitioned the agency to amend FMVSS No. 304 to include an autofrettage

6 requirement. Norris stated that composite containers are usually

produced by volumetric expansion (autofrettage) of the liner wrapped

with continuous filament windings.

\6\ Autofrettage is a manufacturing process for composite

containers in which the container is pressurized to the point where

the metal liner begins to yield, thereby placing the liner in

compression and the fiber overwrap in tension once pressure is

released.

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NHTSA has decided not to adopt Norris' request to include a

requirement addressing autofrettage. The agency believes that the

current requirements in FMVSS No. 304 such as the material designation

requirements in S5.2 and the manufacturing processes for composite

container requirements in S5.3 adequately ensure the safe performance

of a CNG container. The agency further believes that this manufacturing

process should be left to the discretion of the container manufacturer.

Moreover, no other manufacturer raised this issue, and Norris offered

no convincing rationale for amending FMVSS 304 to include such a

requirement.

c. Reference to S5.7.3. SCI stated that S5.4.3 refers to a

nonexistent S5.7.3, and therefore suggested that this reference be

deleted or defined. NHTSA notes that SCI's statement is incorrect;

there is a section S5.7.3, Tensile Strength.

d. Container liner burst test. SCI petitioned the agency to amend

FMVSS No. 304 to add a new section S5.4.2.4 which would state that

``Wall thickness of a liner shall be such that the burst pressure of

the liner without overwrap is at least 1.25 times the service pressure

of the container.'' SCI stated compliance with this new requirement

should be demonstrated by the addition of a liner burst test in S8. SCI

further stated that these requirements are needed since the safety

factors for Type 2 containers are based on the premise that the liner

without the fiber overwrap will maintain service pressure without

failure.

NHTSA has decided not to amend FMVSS No. 304 to add a wall

thickness performance requirement. While SCI's assertion is true that

the liner alone is to maintain service pressure, this fact is not

relevant to its request for a new test. Moreover, SCI provided no

compelling safety rationale as to why these new requirements should be

added. Section S5.4.2 of the final rule currently specifies liner wall

thickness based on liner stress requirements at various container

pressures, which is consistent with ANSI/NGV2, the voluntary industry

standard. The agency believes that there is no need to add these new

requirements for the liner only, since the rule has burst, pressure

cycling, and bonfire requirements which test the container as a whole

after manufacturing.

e. Check analysis tolerances for materials. PST stated that the

requirements for chemical analysis in S5.2, Material designations, are

unreasonable unless the agency allows normal check analysis tolerances

in addition to the stated chemical composition ranges. Normal check

analysis tolerances are the slight variations found when verifying a

metal's chemical composition. PST added that this is not seen as a

problem with the rule, but only in the definition of NHTSA enforcement

tests. According to the petitioner, since metal analysis is not

absolutely precise, some allowance for non-repeatability in the

analyses is necessary.

NHTSA has decided not to amend FMVSS No. 304 with respect to the

chemical analysis of materials. The agency notes that the requirements

specified in S5.2 already provide ranges for the chemical compositions

of various elements. For example, copper is allowed to be between 0.15

to 0.60 percent in certain aluminum containers. Manufacturers seeking

to ensure compliance could aim to hit the mid-point in each range. PST

provided no data to support its claim that the specified ranges for

chemical compositions, which are consistent with the ranges specified

in NGV2, are inadequate. Moreover, no other manufacturer informed the

agency that these chemical composition ranges posed a problem. NHTSA

believes that absent a compelling reason to provide otherwise, FMVSS

No. 304 should be consistent with ANSI/NGV2 since the manufacturers

already comply with the industry standard. Moreover, the agency

believes that it should not consider amending the requirement absent

input from other manufacturers. Based on the above considerations,

NHTSA has decided that it is not appropriate for the Standard to

specify check analysis tolerances.

f. Wall stress formula. PST and Norris petitioned NHTSA to change

the units which refer to pressure in the wall stress formula to make

the units consistent. The petitioners state that the units are not

consistent: on the left side of the equation, wall stress is in units

of MPa (psi); while, on the right side of the equation, minimum

hydrostatic test pressure is in Bar (psig). The equation is referenced

in S5.4.1(b), Wall thickness, Type 1 containers. The petitioners state

that this is also an error in ANSI/NGV2.

NHTSA has decided to amend FMVSS No. 304 to incorporate this change

in the wall stress formula. The agency notes that the petitioners are

correct that the minimum hydrostatic test pressure should be in units

of MPa, and not in Bar (psig). This change will make the units in the

formula consistent. The agency has docketed a memorandum describing a

telephone conversation between agency personnel and a representative of

the AGA in which AGA stated that this is a typographical error in ANSI/

NGV2. AGA is serving as the secretariat for the Natural Gas Vehicle

Fuel Cylinder Task Group, which is the industry group currently

revising and updating ANSI/NGV2.

g. Service pressure vs. Hydrostatic pressure in stress formula. PST

stated that the wall stress formula in S5.4.1(b) should be modified to

refer to service pressure. The formula currently uses, as part of the

equation, hydrostatic test pressure rather than service pressure to

calculate wall stress. The petitioner also stated that the rule does

not define test pressure.

NHTSA has decided not to adopt PST's request to amend the wall

stress formula in S5.4.1(b). The agency notes that the petitioner

provided no rationale as to why service pressure should be used in the

formula rather than hydrostatic test pressure.7 The agency notes

that ANSI/NGV2, which represents the consensus of the natural gas

vehicle industry, uses hydrostatic test pressure. Regarding the

definition of hydrostatic pressure, the rule specifies the definition

for hydrostatic pressure in S4, which is also consistent with the

definition in ANSI/NGV2.

\7\ The agency notes that the terms ``hydrostatic pressure,''

``hydrostatic test pressure,'' and ``test pressure'' are all

synonymous.

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3. Performance Requirements

a. Hydrostatic test. CGA and Norris petitioned the agency to

specify a hydrostatic test and test pressure. CGA stated that test

pressure is commonly 1.5 times the service pressure, and that all

similar containers worldwide are required to be tested to this level to

establish that each one will withstand such pressure at the time of

manufacture. CGA added that unsafe containers might enter the market if

they are not tested at the time of manufacture.

[[Page 37840]]

NHTSA has decided not to adopt the petitioner's request to include

a hydrostatic test. While ANSI/NGV2 requires a hydrostatic pressure

test be performed on each container, FMVSS No. 304 does not require

such a test. Instead, the agency requires each manufacturer to certify

that its containers comply with the burst test requirement. That test

is based on the level of pressure reached at the safety factors, or

stress ratios, specified in FMVSS No. 304. Further, since the burst

test is more stringent than the hydrostatic test, the hydrostatic test

would not provide any additional information about a container's

strength, and therefore is not necessary.

b. Burst pressure vs. Fiber stress ratio. NGV Systems, Ford, PST,

Brunswick, CGA, SCI and Chrysler petitioned the agency to amend FMVSS

No. 304 to correct what they viewed as a conflict in the wording of

S7.2.2. Specifically, the last sentence in S7.2.2 states that ``Burst

pressure is calculated by multiplying the service pressure by the

applicable fiber stress ratio set forth in Table Three.'' The

petitioners claimed that this requirement is in error since burst

pressure is not always directly proportional to fiber stress ratio,

particularly for Type 2 and Type 3 containers where the liner carries

some of the load. The petitioners further indicated that this statement

is not in keeping with the intent of ANSI/NGV2 requirements or industry

practice. Ford and PST suggested that the last sentence of S7.2.2 be

deleted. SCI suggested other changes, such as changing the term

``stress ratio'' to ``pressure ratio'' in S7.2.2, and making other

similar wording changes in the rule to reflect the last sentence in

S7.2.2.

After reviewing the petitions, NHTSA has decided to amend FMVSS No.

304 by deleting the last sentence of S7.2.2. The agency agrees with the

petitioners that the final rule did not reflect the fact that the liner

carries some of the load. Today's modification recognizes the methods

used to manufacture CNG containers and therefore makes the requirement

more practicable than the requirement that was specified in the final

rule. This modification corrects the wording conflict and makes FMVSS

No. 304 consistent with ANSI/NGV2, which was the agency's intent. The

agency has decided not to adopt SCI's suggested wording changes, which

are not necessary given the agency's decision to delete the last

sentence in S7.2.2. The agency further notes that SCI's requested

modification would have made the final rule inconsistent with ANSI/

NGV2.

c. Fiberglass stress ratios: Type 2 containers. Norris petitioned

the agency to revise the safety factors for E-Glass and S-Glass Type 2

containers. Section S7.2.2 of Standard 304 specifies these at 2.65.

Norris stated that considerable safe experience exists with the similar

DOT FRP-2 cylinder design at a safety factor of 2.5, and that this

should not be arbitrarily changed to 2.65. In addition, the CGA

commented more generally that the stress ratios in Table 3 of S7.2.2

for some cylinder types are different from those used in industry

practice, and suggested an open forum at NHTSA to discuss these points.

NHTSA has decided not to adopt Norris' request to lower the safety

factor for E-Glass and S-Glass containers to 2.5. The agency believes

that it would be inappropriate to make such a change based on DOT FRP-

2, which is a RSPA requirement that regulates cylinders used in

transport. In contrast, FMVSS No. 304 is a Federal motor vehicle safety

standard that regulates the manufacture of CNG containers for use in

motor vehicle applications. Although cylinders made to FRP-2 are

similar in design to Type 2 containers, they are subject to a much

different operating environment. For example, Type 2 containers, being

in the automotive environment, are subject to many more pressurization

cycles due to refueling. Based on these different applications, NHTSA

believes the higher safety factor of 2.65 is justified. More generally,

the fiber stress ratios which NHTSA has currently set in FMVSS No. 304

are the same as those of ANSI/NGV2, which represents a consensus of the

CNG vehicle industry.

4. Labeling Requirements

a. Letter height. Ford, SCI, and Chrysler petitioned the agency to

reduce the height of the required lettering on the container label

specified in S7.4. Ford requested the lettering height be changed from

12.7 mm to 4 mm, stating that 4 mm is the same height required for VIN

lettering. Ford stated that using letters 12.7 mm high will result in a

label so large that, when it is applied to the container, not all parts

of the label will be visible due to the label's wrapping around the

container surface. SCI petitioned the agency to reduce the lettering

height to 6.35 mm. SCI stated that if the lettering were 12.7 mm in

height, the label might be so large that it could be impossible to read

all the necessary information once the fuel container is installed.

Chrysler stated that typical labeling uses a combination of 3 mm and 6

mm characters.

After reviewing these petitions for reconsideration, NHTSA has

decided to amend FMVSS No. 304 to reduce the required lettering height

since the lettering height in the final rule is too large to enable

manufacturers to provide labels that fit appropriately on the CNG

containers. Specifically, the agency has decided to amend S7.4 to

specify that the lettering height be 6.35 mm (0.25 inch), which is

consistent with the comments of Chrysler and SCI. The agency believes

that Ford's request to reduce the lettering height still further, to 4

mm (0.157 inch), would be inappropriate since lettering of that height

could be too small to be readily visible at various locations on CNG

vehicles.

b. Container label permanency. SCI requested that NHTSA clarify how

S7.4 should be interpreted, claiming that it is difficult for a

container manufacturer to guarantee label permanency. That provision

states that ``Each CNG fuel container shall be permanently labeled * *

*.''

By ``permanent,'' NHTSA means that the label should remain in place

and be legible for the manufacturer's recommended life of the

container. For instance, a metal tag with embossed or raised letters

riveted in place would be considered permanent. Similarly, a mylar

label that is subsurface printed and is made of a material that is

resistant to fade, heat, moisture and abrasion would typically be

considered permanent (see Standard No. 129, section S5.4.3). To carry

out this intent, NHTSA has modified section S7.4 to state that ``Any

label affixed to the container in compliance with this section shall

remain in place and be legible for the manufacturer's recommended life

of the container.''

c. Fill pressure. Norris petitioned the agency to require that the

container label indicate the maximum allowed fill pressure during

refueling. Norris stated, without explanation, that information about

fill pressure would be more useful than service pressure.

NHTSA has decided not to adopt Norris's request to include the fill

pressure on the label. Section S7.4 of FMVSS No. 304 requires that the

service pressure be specified on the container label. This is the

pressure at which the container is designed to operate under normal

conditions. At present, there are two basic service pressures for CNG

containers: 3,000 psi and 3,600 psi. NHTSA did not propose and does not

now believe there is a compelling reason to specify maximum fill

pressure. The agency notes that Norris provided no safety rationale to

justify such a requirement and that the current labeling requirement to

specify service pressure is consistent with ANSI/NGV2,

[[Page 37841]]

which represents a consensus of the CNG fuel container industry.

d. Service pressure. SCI petitioned the agency to specify that

``Service pressure'' be on the container label, rather than ``Maximum

service pressure'' as required by S7.4(c). Since ``Service pressure''

is defined in FMVSS No. 304, not ``Maximum service pressure,'' SCI

stated that this revision to the label would retain consistent

terminology.

NHTSA has decided to adopt SCI's request to specify ``service

pressure'' on the container label. The agency notes that the term

``maximum service pressure,'' as required to be on the container label

in FMVSS No. 304, was intended to mean the same as ``service

pressure.'' Thus, the agency was using the two terms interchangeably,

even though FMVSS No. 304 defines ``service pressure'' but not

``maximum service pressure.'' The agency believes that use of the two

different terms in FMVSS No. 304 could be confusing. Specifically, the

term ``maximum service pressure'' could be construed to mean a higher

pressure than what was intended in FMVSS No. 304. Therefore, S7.4(c)

has been revised to read:

``Service Pressure ________ kPa (________ psig).''

e. Symbol ``DOT''. Section S7.4(d) requires the symbol ``DOT'' to

be placed on the container label as the manufacturer's certification

that the container complies with all requirements of FMVSS No. 304. SCI

stated that the container label symbol ``DOT'' is not meaningful and

should be expanded to include the standard and effective date, ``DOT

FMVSS-304-0395.''

NHTSA has decided not to adopt SCI's request to modify the labeling

requirement related to the symbol ``DOT.'' The agency believes that the

information requested by SCI would create additional confusion. The

agency further notes that the use of the symbol ``DOT'' in FMVSS No.

304 is readily understood in the motor vehicle industry and is

consistent with its use in other FMVSSs for items of motor vehicle

equipment, such as FMVSS No. 106, Brake Hoses, and FMVSS No. 109, New

pneumatic tires. The agency decided not to specify the version of the

standard, since the agency typically does not reissue standards en toto

every few years. Rather, at most, it periodically amends specific

provisions in a standard. Therefore, the agency does not refer to its

standards as the 1995 version of a particular standard.

f. Service life. SCI petitioned the agency to specify a 15 year

service life for CNG containers since FMVSS No. 304's pressure cycling

test of 18,000 cycles is based on 15 years (four refuelings per day,

300 days per year for 15 years).

NHTSA does not have the authority to regulate the length of time

that the public uses an item of motor vehicle equipment, such as a CNG

container. The agency does have authority to specify labeling

requirements that address a CNG container's service life. The agency is

currently reviewing comments on this matter in response to a December

1994 supplemental notice of proposed rulemaking (SNPRM) that proposed a

container label requirement specifying a container life of 15 years or

a time period specified by the manufacturer. (59 FR 65299, December 19,

1994). If the agency determines that labeling CNG containers with a

service life is appropriate, it will do so in the context of that

rulemaking.

g. Qualification/batch test requirements. Norris requested that

FMVSS No. 304 define ``design family.'' It also stated that neither

qualification nor batch test requirements are spelled out. Such a

requirement would be consistent with RSPA's method of regulating CNG

containers.

Norris' request for FMVSS No. 304 to include information about

``design family'' and other manufacturing considerations would be

inconsistent with how Federal motor vehicle safety standards are

generally promulgated. The manufacturer typically must certify that

each container it manufactures complies with the standard. Therefore,

to comply with FMVSS No. 304, each container must be capable of meeting

the applicable requirements, such as the burst test, and be certified

to meet them. In rare situations such as the flasher requirements in

FMVSS No. 108, Lamps, reflective devices, and associated equipment,

establishing compliance to the standard through batch testing is

permitted.

Given that a batch testing requirement is typically disfavored by

the agency and that the consequences for a failed CNG container are

likely much more dangerous than a failed flasher, NHTSA believes that

it is necessary for a CNG container manufacturer to certify the

compliance of each CNG container.

NHTSA notes that in contrast to NHTSA's framework, RSPA authorizes

batch testing so that each container need not be certified as complying

with its requirements. Terms such as design family, qualification

testing, or batch are used in ANSI/NGV2, and RSPA requirements for DOT

cylinders. For example, ANSI/NGV2 requires qualification tests, such as

the burst test, only when certain design changes are made to a

particular design of CNG containers. In addition, manufacturer tests

are sometimes done on batches or lots of 200 cylinders. Based on the

above considerations, it would be inappropriate to require the

information requested by Norris.

5. Test Conditions

a. Diesel fuel in bonfire test. NHTSA received two petitions for

reconsideration to amend S8.3.6, which addresses the bonfire test's use

of diesel fuel. Flxible petitioned the agency to allow the use of a

wood-fueled bonfire test rather than diesel fuel. It stated that fire

marshals and other authorities have placed restrictions on the use of

diesel fuel. SCI stated that the use of diesel fuel would adversely

affect the environment, but offered no alternative.

NHTSA has decided not to amend FMVSS No. 304 with respect to the

bonfire test's fuel in today's notice. Instead, the agency is currently

reviewing comments on this matter in response to a SNPRM that included

a proposal to amend the bonfire test to allow alternative types of fuel

given the potential environmental problems with using diesel fuel. If

the agency determines that the bonfire test's fuel needs to be changed,

it will do so in the context of that rulemaking.

b. More detail in bonfire test. PST requested that NHTSA define the

bonfire test in more detail. Paragraph S8.3.10 states that, during the

bonfire test, ``[t]he average wind velocity at the container is not to

exceed 2.24 meters per second (5 mph).'' The petitioner stated that in

some conditions, a 2.24 meters per second wind might preclude the

container from being totally engulfed in flames. This consideration led

PST to recommend that this requirement should instead read ``* * * 5

mph or less if necessary to achieve full impingement and engulfment.''

PST indicated that it uses a system of wind shields during its testing

to assure full impingement or engulfment.

NHTSA has decided not to amend the bonfire test in FMVSS No. 304.

The agency notes that since S8.3.2 and S8.3.3 specify full flame

impingement or engulfment of the container during testing, allowing a

wind speed of up to 2.24 meters per second will not preclude total

flame impingement or engulfment. The agency notes that a manufacturer

is not precluded from using wind shields to assure that full flame

impingement or engulfment is achieved.

c. Venting of container during bonfire test. Section S7.3 specifies

that during the bonfire test, the CNG container shall

[[Page 37842]]

either completely vent its contents through a pressure relief device or

shall not burst while retaining its entire contents. PST stated that

this requirement is unreasonable because it is difficult to verify and

unnecessary. PST offered no alternative language, but stated that under

certain conditions a small amount of gas can escape through seals

around the pressure relief devices and leak small quantities of gas

during the test. According to PST, this leakage is not harmful and

should be allowed. PST further stated that if the intent of S7.3 is

that the container vent completely through the pressure relief device,

incidental leaks should be of no concern.

NHTSA believes that it would be inappropriate to amend FMVSS No.

304 based on PST's unsupported claim that under certain conditions a

small amount of gas can leak through seals around the pressure relief

device. PST provided no information showing that the burst requirement

is inappropriate or that leakage around the seal is a problem in a

properly constructed CNG container. The agency further notes that no

other petitioner believed that this requirement is inappropriate or

raised practicability problems. If such additional information is

provided, NHTSA would consider whether further rulemaking is

appropriate. As an alternative to seeking an amendment to the standard,

PST could file a petition requesting the agency determine that such a

noncompliance with the standard is inconsequential as it relates to

safety under Part 556, Exemption for Inconsequential Defect or

Noncompliance.

d. Burst and pressure cycling test procedures. PST stated that the

allowable range of pressurization rates for the burst test is

unreasonable, and that NHTSA should draft and publish methods for

compliance testing which set a minimum pressurization rate of 100 psi

per second. S8.2.2 specifies that pressurization throughout the burst

test shall not exceed 200 psi per second. PST indicated that test

results are a function of pressurization rate, and that very low rates

can make the test overly stringent. Similarly, PST stated that the

absence of a minimum cycling rate or test duration in the pressure

cycling test, S8.1.3, is unreasonable, since fatigue cycle life is

known to be sensitive to the cycling rate and test duration. Section

S8.1.3 specifies a maximum cycling rate of 10 cycles per minute. PST

stated that a minimum cycling rate of 5 cycles per minute is

reasonable, or alternatively, a test duration of 60 hours. PST stated

that it had previously commented on these issues.

NHTSA has decided not to adopt PST's request to modify the

pressurization rates in the burst test. While PST is correct that

pressurization rates do affect the test's severity, the agency notes

that it is appropriate to specify the range because CNG containers in

the real world will experience a variety of pressurizations. Therefore,

it is in the interest of safety to specify such rates. In addition,

specifying maximum pressurization and cycling rates in FMVSS No. 304

without specifying minimums is consistent with the voluntary industry

standard, ANSI/NGV2. The agency specifically asked CGA and the NGVC

about minimum pressurization and cycling rates, but neither

organization was able to provide adequate rationale to include them in

the final rule. PST has offered no new data to support the inclusion of

a minimum rate for pressurization or cycling. Based on the above

considerations, the agency believes that the rule should remain the

same as those in NGV2 with no minimum pressurization and cycling rates.

6. Miscellaneous

a. Withdraw or delay the effective date of FMVSS 304. Several

petitioners asked that the final rule be withdrawn, or delayed for a

year or more. A number of them stated the rule does not reflect all of

the safety requirements contained in ANSI/NGV2, and therefore is not

comprehensive from a safety standpoint. They also stated that ANSI/NGV2

is currently being revised and updated by the industry, and indicated

that a delay would allow incorporation of these new revisions.

NHTSA has determined that it would be inappropriate to withdraw the

effective date of the September 1994 final rule, which took effect

March 27, 1995. Even though the rule does not contain all of the

requirements of ANSI/NGV2, NHTSA believes that it is better to have

some requirements in place rather than none at all. Further, the agency

is moving toward adding more requirements through the SNPRM that was

published in December 1994. That notice proposes additional performance

requirements, consistent with those in ANSI/NGV2, to evaluate a CNG

fuel container's internal and external resistance to corrosion and

acidic chemicals, brittle fracture, fragmentation, and external damage

caused by incidental contact with road debris or mechanical damage

during the vehicle's operation.

With regard to the revisions currently being made to ANSI/NGV2,

NHTSA believes that it would be inappropriate for the same reason to

delay the rule.

b. Flexibility and adaptability of final rule. Chrysler supported

earlier comments submitted by the American Automobile Manufacturers

Association (AAMA) which included the statement that the ANSI/NGV2

voluntary industry standard ``* * * lacks the flexibility and

adaptability that should be part of a regulatory requirement * * *''

Those earlier comments were submitted by AAMA in response to the

December 1993 SNPRM.

NHTSA notes that in the December 1993 SNPRM, the agency announced

that it was considering the adoption of many of the requirements in

ANSI/NGV2 for its final rule on CNG containers. The agency also laid

out its rationale for this approach. After considering all of the

comments, the agency based the rule on the voluntary industry standard,

ANSI/NGV2. Chrysler offered no new arguments which the agency has not

already considered and responded to in promulgating the rule.

c. Chemical compositions. NHTSA has decided to revise S5.2.2 to

reflect new information provided by AGA in a telephone conversation

with NHTSA staff members. The AGA advised the agency that there is a

typographical error in S5.2.2 concerning the amount of magnesium in

6061 alloy aluminum. While FMVSS No. 304 specifies ``0.60 to 1.20

percent,'' AGA stated that the correct numbers are 0.80 to 1.20. The

error is also present in the current version of ANSI/NGV2.

NGVSys submitted a letter dated February 16, 1995, requesting that

the percent limits for lead and bismuth in aluminum alloy 6061 be

revised. S5.2.2 of Standard 304 currently specifies these each at 0.003

percent maximum. NGVSys requested that the limits be revised to 0.01

percent maximum, indicating that the industry group currently revising

ANSI/NGV2 has accepted this change for its 1995 revision. NGVSys

enclosed with its request a copy of a letter from Alcoa, an aluminum

supplier. The letter indicates that Alcoa's current limit for lead and

bismuth in aluminum alloy 6061 is 0.010 percent each, and that further

reductions in this limit would impact cost.

NHTSA has decided to deny NGV System's request. NGV Systems has

provided no rationale to justify its request, nor has it provided any

information on the safety implications of allowing the increased

amounts of lead and bismuth. The agency notes that FMVSS No. 304's

specifications for lead and bismuth are consistent with both

[[Page 37843]]

the current version of ANSI/NGV2 and the draft ISO standard for CNG

containers.

IV. Rulemaking Analyses

A. Executive Order 12866 and DOT Regulatory Policies and Procedures

NHTSA has considered this rulemaking action in connection with

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. In conjunction

with the September 1994 final rule, NHTSA prepared a Final Regulatory

Evaluation (FRE) in which it estimated the rulemaking's costs. Today's

rule simply reaffirms the December final rule in which the agency

concluded that ``specify(ing) a 2.25 safety factor for carbon fiber

containers would negate this cost increase to container manufacturers,

as they currently manufacture containers to this value.'' As a result,

manufacturers will not have to depart from current manufacturing

practices and thus not incur additional costs. Most of the performance

requirements in the standard are already being met by CNG fuel

container manufacturers, who produce and test containers in accordance

with ANSI/NGV2. The agency's reaffirmation of its December 1994

decision to specify a 2.25 safety factor for carbon fiber containers

negates the cost increase faced by container manufacturers as a result

of the higher factor in the September 1994 final rule. The

manufacturers already manufacture containers to the lower factor. Since

the agency has decided to adopt the same safety factor as that

currently met by container manufacturers, there is no need to perform a

new regulatory evaluation. The agency further notes that the various

minor amendments being made in today's notice will collectively have

only a negligible effect on costs.

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 businesses manufacturing CNG

fuel containers are not small businesses. Further, as noted above, the

amendments made in today's document will have a negligible effect on

costs of compliance.

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. 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 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, Incorporation by reference, Motor vehicle safety, Motor

vehicles.

PART 571--[AMENDED]

In consideration of the foregoing, 49 CFR Part 571 is amended as

follows:

1. The authority citation for Part 571 continues to read as

follows:

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

delegation of authority at 49 CFR 1.50.

Sec. 571.5 [Amended]

2. Section 571.5 is amended by removing paragraph (b)(9).

Sec. 571.304 [Amended]

3. Section 571.304 is amended by revising S5.2.2, S5.4.1(b),

S5.5.1, S7.2.2, S7.4, S8.1.3, S8.2.2, and S8.3.10 to read as follows:

* * * * *

S5.2.2 Aluminum containers and aluminum liners. (Type 1, Type 2 and

Type 3) shall be 6010 alloy, 6061 alloy, and T6 temper. The aluminum

heat analysis shall be in conformance with one of the following grades:

Table Two.--Aluminum Heat Analysis

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

Grade: Element 6010 alloy percent 6061 alloy percent

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

Magnesium.............. 0.60 to 1.00........... 0.80 to 1.20.

Silicon................ 0.80 to 1.20........... 0.40 to 0.80.

Copper................. 0.15 to 0.60........... 0.15 to 0.40.

Chromium............... 0.05 to 0.10........... 0.04 to 0.35.

Iron................... 0.50 max............... 0.70 max.

Titanium............... 0.10 max............... 0.15 max.

Manganese.............. 0.20 to 0.80........... 0.15 max.

Zinc................... 0.25 max............... 0.25 max.

Bismuth................ 0.003 max.............. 0.003 max.

Lead................... 0.003 max.............. 0.003 max.

Others, Each \1\....... 0.05 max............... 0.05 max.

Others, Total \1\...... 0.15 max............... 0.15 max.

Aluminum............... Remainder.............. Remainder.

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

\1\ Analysis is made only for the elements for which specific limits are

shown, except for unalloyed aluminum. If, however, the presence of

other elements is indicated to be in excess of specified limits,

further analysis is made to determine that these other elements are

not in excess of the amount specified. (Aluminum Association Standards

and Data--Sixth Edition 1979).

* * * * *

S5.4.1 Type 1 Containers.

(a) * * *

(b) For minimum wall thickness calculations, the following formula

is used:

[GRAPHIC][TIFF OMITTED]TR24JY95.004

Where:

S = Wall stress in MPa (psi).

P = Minimum hydrostatic test pressure in Mpa (psi).

D = Outside diameter in mm (inches).

d = Inside diameter in mm (inches).

* * * * *

S5.5.1 Compute stresses in the liner and composite reinforcement

using National Aeronautics and Space Administration (NASA), Computer

Program for the Analysis of Filament Reinforced Metal-Wound Pressure

[[Page 37844]]

Vessels, N67-12097 (NASA CR-72124) (May 1966), or its equivalent.

* * * * *

S7.2.2 Each Type 2, Type 3, or Type 4 CNG fuel container shall not

leak when subjected to burst pressure and tested in accordance with

S8.2. Burst pressure shall be no less than the value necessary to meet

the stress ratio requirements of Table 3, when analyzed in accordance

with the requirements of S5.5.1.

Table Three.--Stress Ratios

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

Material Type 2 Type 3 Type 4

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

E-Glass................................... 2.65 3.5 3.5

S-Glass................................... 2.65 3.5 3.5

Aramid.................................... 2.25 3.0 3.0

Carbon.................................... 2.25 2.25 2.25

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

* * * * *

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

labeled with the information specified in paragraphs (a) through (d).

Any label affixed to the container in compliance with this section

shall remain in place and be legible for the manufacturer's recommended

life of the container. The information specified in paragraphs (a)

through (d) of this section shall be in English and in letters and

numbers that are at least 6.35 mm (0.25 inch).

(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) 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.

* * * * *

S8.1.3 The cycling rate for S8.1.1 and S8.1.2 shall be any value

up to and including 10 cycles per minute.

* * * * *

S8.2.2 The pressurization rate throughout the test shall be any

value up to and including 1,379 kPa (200 psi) per second.

* * * * *

S8.3.10 The average wind velocity at the container is any velocity

up to and including 2.24 meters/second (5 mph).

* * * * *

Issued on July 18, 1995.

Ricardo Martinez,

Administrator.

[FR Doc. 95-18109 Filed 7-19-95; 2:09 pm]

BILLING CODE 4910-59-P