Federal Motor Vehicle Safety Standards; Compressed Natural Gas Fuel Container Integrity |
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Topics: National Highway Traffic Safety Administration, Federal Motor Vehicle Safety Standards
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Ricardo Martinez
Federal Register
December 28, 1994
[Federal Register: December 28, 1994] ======================================================================= ----------------------------------------------------------------------- DEPARTMENT OF TRANSPORTATION National Highway Traffic Safety Administration 49 CFR Part 571 [Docket No. 93-02; Notice 08] RIN [2127-AF47] Federal Motor Vehicle Safety Standards; Compressed Natural Gas Fuel Container Integrity AGENCY: National Highway Traffic Safety Administration (NHTSA), Department of Transportation (DOT). ACTION: Final rule; response to Petitions for reconsideration. ----------------------------------------------------------------------- SUMMARY: This rule provides a partial response to petitions for reconsideration of the final rule that established performance requirements applicable to compressed natural gas (CNG) fuel containers. The final rule specified a safety factor of 3.33 for use in evaluating the strength of carbon fiber containers. This rule takes the intermediate step of specifying a 2.25 safety factor for carbon fiber containers and makes several minor changes to the final rule. After thoroughly analyzing the large number of petitions for reconsideration, the agency plans to issue another final rule establishing a permanent safety factor for carbon fiber containers and addressing the other issues raised in the petitions for reconsideration. If the safety factor is increased, a two year lead time will be given. DATES: Effective Date: The amendments in today's final rule become effective March 27, 1995. 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: 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 No. 304, Compressed Natural Gas Fuel Containers, 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 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. FMVSS No. 304 becomes effective 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. --------------------------------------------------------------------------- The new FMVSS is patterned after the American National Standards Institute's (ANSI's) voluntary industry standard known as ANSI/NGV2 (ANSI/NGV2). ANSI/NGV2 and FMVSS No. 304 specify detailed material and design 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 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 calculating 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 both the applicable material and design requirements as well as the burst test. While FMVSS No. 304 follows ANSI/NGV2 in most respects, NHTSA departed from ANSI/NGV2 in deciding to require that carbon fiber containers comply with a higher safety factor for the burst tests. Specifically, FMVSS No. 304 specifies 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 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 factor. Many of these petitioners stated that the levels specified by the agency in the final rule are unnecessarily high from a safety standpoint. They further stated that the higher safety factors will unduly increase the cost of carbon fiber containers, thereby making them noncompetitive with other technologies. Some petitioners stated that NHTSA's safety factors are not harmonized with the Canadian Standards Association standard or the draft International Standards Organization standard, both of which specify a 2.25 safety factor for carbon fiber. On the other hand, at least one commenter supported the 3.33 safety factor. While the carbon fiber safety factor was the most controversial issue raised by petitioners, some petitioners commented about other issues in the final rule. For example, some petitioners commented that FMVSS No. 304 prohibits certain materials, such as new or different aluminum and steel. 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 revision, currently underway, of ANSI/NGV2 is completed. Petitioners also raised questions about the need for a variety of technical amendments to FMVSS No. 304. III. Agency Decision As explained below, NHTSA has decided to respond to the petitions for reconsideration in two stages. In today's final rule, the agency provides an initial, partial response to the issue of the appropriate safety factor for carbon fiber containers, pending completion of the reconsideration process. Today's notice also responds to several other technical issues whose resolution did not necessitate extensive review or consideration. Subsequently, the agency will issue a second notice finally resolving the issue of the safety factor for carbon fiber containers and responding to the balance of the issues in the petitions for reconsideration. Today's decision regarding the safety factor for carbon fiber containers will provide NHTSA with an opportunity to review and analyze all the information presented in the petitions for reconsideration on this issue, while allowing the manufacture of carbon fiber containers, subject to a safety factor of 2.25. After NHSTA has completed its analysis, the agency will then make a final decision on the appropriate safety factor for carbon fiber containers. The agency anticipates issuing this notice in the Spring of 1995. Depending on the conclusions arising from its review, the agency may take one of three actions: reaffirm its decision in this notice that the safety factor for carbon fiber containers should be 2.25; adopt the safety factors specified in the original final rule; or adopt a safety factor somewhere in between those two alternatives. If the agency decides at the conclusion of the reconsideration process to set safety factors at values higher than 2.25, it will set an effective date of two years from the date on which the decision is published in the Federal Register to provide the industry with adequate lead time to manufacture such containers. NHTSA's two step approach to responding to the petitions will provide it with the time it needs to review and analyze the voluminous information submitted by the petitioners. That information includes, among other things, Brunswick's data on how the higher carbon fiber safety factor increases costs; Brunswick's test data on the long term durability of carbon fiber containers (these tests include tests relating to high pressure cycling, severe damage abuse, and acidic environment); EDO's test data on the long term performance of carbon fiber fuel containers, including high impact damage, severe abuse, corrosion resistance, accelerated aging, and exposure to chemicals; information from EDO and Brunswick about the number of carbon fiber CNG containers currently in use; Dynetek's information on the resistance of carbon fiber containers to acidic environments; Thomas Built's information on the safety record of carbon fiber CNG containers currently in-use; and NGVC's and AGA's information on the cost increase of carbon fiber containers due to the higher safety factor. The necessity for providing an initial, expedited response on the issue of the 2.5 and 3.33 safety factors for carbon fiber containers arises from several factors. First, the effective date for FMVSS No. 304, i.e., March 27, 1995, is very near. Second, manufacturers have typically been building CNG carbon fiber containers to comply with a much lower safety factor, the 2.25 safety factor specified in ANSI/ NGV2. Third, the container manufacturers would incur significant cost in switching from the production of carbon fiber containers complying with a 3.33 safety factor. Today's notice will avoid the necessity of carbon fiber container manufacturers having to incur costs and make design adjustments in order to comply with requirements that may ultimately be found to be more stringent than necessary. Given its decision to defer resolution of the issue of whether to impose safety factors of 2.5 and 3.33 for carbon fiber containers, NHTSA was faced with making the further decision whether to specify any safety factor so that the burst test can be implemented pending completion of the reconsideration process. The choice was between not specifying any safety factor or specifying a 2.25 safety factor, the factor with which carbon fiber container manufacturers currently comply. Not specifying any safety factor at all would have permitted the manufacture of weaker, less safe carbon fiber containers. The agency has concluded that, pending a final decision on this matter, a 2.25 safety factor should be adopted. NHTSA believes that this decision is appropriate for several reasons. First, this decision will assure that there is a minimum level of strength for CNG carbon fiber containers. Second, 2.25 is the value specified in ANSI/NGV2 and in the Canadian Standards Association standard. Third, manufacturers have been building CNG carbon fiber containers to this safety factor. Accordingly, adopting a 2.25 safety factor will promote safety, be consistent with current practice and not impose any additional costs. However, after thoroughly analyzing the data provided by the petitioners, the agency may decide to increase the safety factor to 3.33 or some intermediate level. If this occurs, a two year lead time will be given. In today's final rule, NHTSA has decided also to amend two other aspects of the September 1994 final rule. In response to Norris Cylinder Company (Norris), section S6.2 is amended to state ``Each CNG fuel container manufactured on or after March 27, 1994, shall meet the requirements of S7 through S7.4.'' (Emphasis added). This change is necessary to reflect the actual effective date. Norris correctly stated that the final rule had incorrectly referred to containers manufactured on or after March 27, 1994. In response to several petitioners, including Ford and NGV Systems, section S5.5.1 is amended to include the phrase ``or its equivalent.'' These commenters correctly stated that the National Aeronautics and Space Administration (NASA) computer program referenced in ANSI/NGV2 and FMVSS No. 304 is outdated. Therefore, including the phrase ``or its equivalent'' as ANSI/NGV2 does will assist manufacturers in their efforts to establish compliance with FMVSS No. 304. NHTSA notes that several petitioners criticized the agency for not establishing additional performance requirements to ensure the safety of CNG containers. For instance, Brunswick stated that ``The final rule does not incorporate critical safety tests and requirements that are part of the current ANSI/AGA NGV2 Standard and are necessary to insure safety.'' As explained in the September 1994 final rule, NHTSA anticipated issuing additional performance requirements, consistent with ANSI/NGV2, after the final rule was issued. The agency's decision regarding this sequence of notices was made to accommodate requests by Brunswick and other CNG container manufacturers for NHTSA initially to issue requirements to ensure a CNG container's durability, strength, and pressure relief. In keeping with that decision, NHTSA followed the final rule with a supplemental notice of proposed rulemaking (SNPRM) that proposes additional performance requirements, consistent with those in ANSI/NGV2, to evaluate a CNG fuel container's internal and external resistance to corrosion, brittle fracture, fragmentation, and external damage caused by incidental contact with road debris or mechanical damage during the vehicle's operation. (59 FR 65299, December 19, 1994). As the agency stated in the SNPRM, the agency tentatively concludes that these additional performance requirements are critical for determining a CNG container's safety. In addition, the agency proposed additional labeling requirements that should provide important safety information about a CNG container's service life. Accordingly, NHTSA believes that the agency has already responded to the petitioners' suggestion that the agency was not adequately addressing other aspects of CNG container safety. 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 the final rule, the agency concluded that 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. CNG container manufacturers would not incur a cost increase for meeting the requirements in the bonfire test and the pressure cycling test. However, the agency concluded that the decision to increase the safety factor for carbon fiber containers would have an impact on CNG container manufacturers. The agency estimated that increasing the burst test safety factor from 2.25 to 3.33 would result in a direct cost increase of 37.1 percent and weight increase of 35.1 percent for containers that meet the 2.25 safety factor. These estimated cost and weight increases were arrived at through analysis and interpolation of information provided by Brunswick. The agency refers interested parties to the ``Final Regulatory Evaluation'', FMVSS No. 304, Fuel System Integrity, Compressed Natural Gas Containers, September 1994, for details on the additional cost incurred for a 3.33 safety factor. The agency's decision to specify 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. Since the agency is taking this intermediate step to lower the factor to the value which is currently met by container manufacturers, the agency does not see a need to perform a new regulatory evaluation, at this time. 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. 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. 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 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. (inches). Sec. 571.304 [Amended] 2. Section 571.304 is amended by revising S5.5.1, S6.2, and S7.2.2, as follows: * * * * * S5.5.1 Compute stresses in the liner and composite reinforcement using National Aeronautics and Space Administration (NASA) NAS 3-6292, Computer Program for the Analysis of Filament Reinforced Metal-Shell Pressure Vessels, (May 1966), or its equivalent. * * * * * S6.2 Each CNG fuel container manufactured on or after March 27, 1995 shall meet the requirements of S7 through S7.4. * * * * * 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. Burst pressure is calculated by multiplying the service pressure by the applicable stress ratio set forth in Table Three. 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 ------------------------------------------------------------------------ * * * * * Issued on December 21, 1994. Ricardo Martinez, Administrator. [FR Doc. 94-31847 Filed 12-22-94; 10:49 am] BILLING CODE 4910-59-P-M