Hazardous Materials: Requirements for UN Cylinders, 11768-11801 [05-3859]

Agencies

• Pipeline and Hazardous Materials Safety Administration
• DEPARTMENT OF TRANSPORTATION

[Federal Register Volume 70, Number 45 (Wednesday, March 9, 2005)]
[Proposed Rules]
[Pages 11768-11801]
From the Federal Register Online via the Government Printing Office [www.gpo.gov]
[FR Doc No: 05-3859]



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Part III





Department of Transportation





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Pipeline and Hazardous Materials Safety Administration



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49 CFR Parts 107, 171, et al.



Hazardous Materials: Requirements for UN Cylinders; Proposed Rule

Federal Register / Vol. 70, No. 45 / Wednesday, March 9, 2005 / 
Proposed Rules

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DEPARTMENT OF TRANSPORTATION

Pipeline and Hazardous Materials Safety Administration

49 CFR Parts 107, 171, 172, 173, 178, and 180

[Docket No. PHMSA-2005-17463 (HM-220E)]
RIN 2137-AD91


Hazardous Materials: Requirements for UN Cylinders

AGENCY: Pipeline and Hazardous Materials Safety Administration (PHMSA), 
DOT.

ACTION: Notice of proposed rulemaking.

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SUMMARY: PHMSA proposes to amend the Hazardous Materials Regulations 
(HMR) to adopt standards for the design, construction, maintenance and 
use of cylinders and multiple-element gas containers (MEGCs) based on 
the standards contained in the United Nations (UN) Recommendations on 
the Transport of Dangerous Goods. Aligning the HMR with the UN 
Recommendations will promote flexibility, permit the use of 
technological advances for the manufacture of pressure receptacles, 
provide for a broader selection of pressure receptacles, reduce the 
need for exemptions, and facilitate international commerce in the 
transportation of compressed gases.

DATES: Comments must be received by July 7, 2005.

ADDRESSES: You may submit comments to Docket No. PHMSA-05-17463 (HM-
220E) by any of the following methods:
     Federal eRulemaking Portal: Go to https://
www.regulations.gov. Follow the online instructions for submitting 
comments.
     Web Site: https://dms.dot.gov. Follow the instructions for 
submitting comments on the DOT electronic docket site.
     Fax: 202- 493-2251.
     Mail: Docket Management System; U.S. Department of 
Transportation, 400 Seventh Street, SW., Nassif Building, Room PL-401, 
Washington, DC 20590-0001.
     Hand Delivery: Docket Management System; Room PL-401 on 
the plaza level of the Nassif Building, 400 Seventh Street, SW., 
Washington, DC, between 9 a.m. and 5 p.m., Monday through Friday, 
except Federal Holidays.
    Instructions: All submissions must include the agency name and 
docket number or Regulatory Identification Number (RIN) for this 
rulemaking. Comments should identify the docket number (PHMSA-05-
17463). If sent by mail, comments are to be submitted in duplicate. 
Persons wishing to receive confirmation of receipt of their comments 
should include a self-addressed stamped postcard. Internet users may 
access all comments received by the Department of Transportation at 
https://dms.dot.gov. Note that all comments received will be posted 
without change to https://dms.dot.gov including any personal information 
provided. Please see the Privacy Act heading under Regulatory Analyses 
and Notices.
    Docket: For access to the docket to read background documents or 
comments received, go to https://dms.dot.gov at any time or to Room PL-
401 on the plaza level of the Nassif Building, 400 Seventh Street, SW., 
Washington, DC between 9 a.m. and 5 p.m., Monday through Friday, except 
Federal holidays.

FOR FURTHER INFORMATION CONTACT: Duane Pfund, telephone number (202) 
366-0656, Assistant International Standards Coordinator; Mark Toughiry, 
telephone number (202) 366-4545, Office of Hazardous Materials 
Technology; or Sandra Webb, telephone number (202) 366-8553, Office of 
Hazardous Materials Standards, Research and Special Programs 
Administration, U.S. Department of Transportation, Washington, DC 
20590-0001.

SUPPLEMENTARY INFORMATION:

List of Topics

I. Background
II. Overview of Proposed Changes in This NPRM
III. UN Pressure Receptacles and MEGCs--Design and Construction 
Requirements
    A. Refillable Seamless Steel Cylinders
    B. Refillable Seamless Steel Tubes
    C. Refillable Seamless Aluminum Alloy Cylinders
    D. Refillable Seamless Acetylene Cylinders
    E. Non-Refillable Metallic Cylinders
    F. Refillable Composite Cylinders
    G. MEGCs
IV. Pressure Receptacles--Initial and Subsequent Design Type Review 
and Approval Process
V. MEGCs--Initial Design Type Review and Approval Process
VI. Qualification and Approval Process for Persons Performing 
Pressure Certifications
    A. Inspection Bodies
    1. Independent Inspection Agencies (IIAs)
    2. Approval Agencies
    B. Manufacturers
    C. Requalifiers
VII. UN Cylinders and Tubes--Requalification Requirements
VIII. Pressure Receptacles--Filling Limits
IX. Summary of Proposed Regulatory Changes by Part
X. Rulemaking Analyses and Notices

I. Background

    On October 30, 1998, the Research and Special Programs 
Administration (RSPA), the predecessor agency to the Pipeline and 
Hazardous Materials Safety Administration (PHMSA, we), published a 
notice of proposed rulemaking (NPRM) under Docket HM-220 (63 FR 58460). 
In the NPRM, we proposed, among other changes, to amend the Hazardous 
Materials Regulations (HMR; 49 CFR parts 171-180) to establish four (4) 
new metric-marked DOT cylinder specifications to replace twelve (12) 
current cylinder specifications. The proposed specifications were more 
performance-oriented than the current DOT cylinder specifications, and 
were based, in part, on draft standards developed by the International 
Standards Organization (ISO) and the European Committee for 
Standardization.
    Most commenters objected to adoption of specifications based on 
draft ISO standards. These commenters were concerned that the draft ISO 
standards could be changed and that cylinders manufactured to the draft 
standards might not be accepted for transportation in the world market. 
The commenters requested that we delay consideration of the proposed 
metric-marked cylinder specifications until the ISO completed its work 
on the international cylinder standards, and the UN Sub-Committee of 
Experts on the Transport of Dangerous Goods incorporated the ISO 
standards into the UN Recommendations on the Transport of Dangerous 
Goods (UN Model Regulations). Based on the merits of those comments, we 
agreed that the proposed metric-marked cylinder standards and related 
proposals that were based on draft ISO standards should not be adopted. 
On February 13, 2002, we published a notice withdrawing the metric-
marked cylinder standards and related proposals and transferring the 
remaining proposals to Docket No. HM-220D (67 FR 6667) that was 
finalized August 8, 2002 (67 FR 51626).
    The UN Model Regulations establish international standards for the 
safe transportation of hazardous materials. The UN Model Regulations 
are not regulations, but rather recommendations issued by the UN Sub-
Committee of Experts on the Transport of Dangerous Goods (UN Sub-
Committee of Experts). These recommendations are amended and updated 
biennially by the UN Sub-Committee of Experts. They serve as the basis 
for national, regional, and international modal regulations,

[[Page 11769]]

including the International Maritime Dangerous Goods (IMDG) Code issued 
by the International Maritime Organization, and the International Civil 
Aviation Organization Technical Instructions for the Safe Transport of 
Dangerous Goods by Air (ICAO Technical Instructions) issued by the ICAO 
Dangerous Goods Panel. The HMR authorize domestic transportation of 
hazardous materials shipments prepared in accordance with the IMDG Code 
if all or part of the transportation is by vessel, subject to certain 
conditions and limitations, and the transportation of hazardous 
materials shipments prepared in accordance with the ICAO Technical 
Instructions for transportation by aircraft and by motor vehicle either 
before or after being transported by aircraft.
    Since 1999, the UN Sub-Committee of Experts has been working to 
develop international standards for the design, construction, 
inspection, and testing of cylinders and other pressure receptacles for 
inclusion in the UN Model Regulations. The objective was to develop 
requirements that can be globally accepted for international 
transportation, storage, and use. Representatives from the European 
Industrial Gases Association, the Compressed Gas Association, the 
European Cylinder Makers Association, the International Standards 
Organization Technical Committee 58 (ISO/TC 58), and many specialist 
government officials, including cylinder experts from DOT, participated 
in the UN Sub-Committee of Experts' efforts.
    The standards developed for cylinders and other gas receptacles 
address manufacture, approval, filling, and use. The cylinders and 
other gas receptacles must be in compliance with ISO standards for 
design, manufacture, and testing; constructed of materials that are 
compatible with the gas to be contained in the cylinder, as established 
in ISO standards; and periodically inspected according to ISO 
standards. The standards were adopted by the UN Sub-Committee of 
Experts in 2001 and 2004 and are included in the 13th and 14th Edition 
of the UN Model Regulations. Cylinders manufactured in accordance with 
these requirements are marked with the internationally recognized UN 
mark, which ensures that the cylinders are acceptable world-wide.
    The continually increasing amount of hazardous materials 
transported in international commerce warrants the harmonization of 
domestic and international requirements to the greatest extent 
possible. Harmonization serves to facilitate international 
transportation and at the same time ensures the safety of people, 
property and the environment. While the intent of the harmonization 
rulemakings is to align the HMR with international standards, we review 
and consider each amendment on its own merit. Each amendment is 
considered on the basis of the overall impact on transportation safety 
and the economic implications associated with its adoption into the 
HMR. Our goal is to harmonize without sacrificing the current HMR level 
of safety and without imposing undue burdens on the regulated public. 
To this end, we are proposing to adopt the UN standards for cylinders 
(pressure receptacles limited to a water capacity of 150 L), tubes 
(pressure receptacles with a water capacity exceeding 150 L and not 
more than 3,000 L capacity), cylinder bundles (cylinders held together 
in a frame and manifolded together with up to a total water capacity of 
3,000 L or 1,000 L for toxic gases), and multiple element gas 
containers (MEGCs) into the HMR. Our proposal does not remove existing 
requirements for DOT specification cylinders; rather, we propose to 
incorporate the UN standards so that a shipper may use either a DOT 
specification cylinder or a UN standard pressure receptacle as 
appropriate for individual gases and circumstances. The goal of this 
rulemaking is to promote flexibility and permit the use of advanced 
technology for the manufacture and use of pressure receptacles, to 
provide for a broader selection of authorized pressure receptacles, 
reduce the need for exemptions, and to facilitate international 
transportation.
    DOT technical experts participated in evaluating the ISO standards 
on which the UN Model Regulations applicable to pressure receptacles 
are based. We believe that the design, manufacturing, and test 
requirements provide an equivalent level of safety as the DOT cylinder 
requirements. Copies of the ISO standards are available for review in 
the public docket for this rulemaking. The public docket may be viewed 
in Room PL-401 of the Nassif Building, 400 7th Street, SW., Washington, 
DC 20590.

II. Overview of Proposed Changes in This NPRM

    This NPRM proposes to amend the HMR to incorporate:
--Design, construction and testing requirements for refillable seamless 
aluminum alloy cylinders conforming to ISO 7866;
--Design, construction and testing requirements for refillable seamless 
steel cylinders conforming to ISO 9809-1, ISO 9809-2, and ISO 9809-3;
--Design, construction and testing requirements for non-refillable 
metallic cylinders conforming to ISO 11118;
--Design, construction and testing requirements for composite cylinders 
conforming to ISO 11119-1, 11119-2 and 11119-3, with certain 
limitations;
--Design, construction and testing requirement for refillable seamless 
steel tubes with a water capacity between 150 L and 3,000 L conforming 
to ISO 11120;
--Design, construction and testing requirements for UN acetylene 
cylinders conforming to applicable ISO standards, except the cylinders 
must be refillable, made of stainless steel, filled with a suitable 
quantity of solvent (solvent-free not authorized) and fitted with 
suitable fusible plugs;
--Design, construction and testing requirements for MEGCs;
--Requalification of UN pressure receptacles, including pressure 
receptacles installed as components of MEGCs;
--A quality conformity assessment system for UN pressure receptables 
consistent with section 6.2.2.5 of the UN Model Regulations;
--A 10-year requalification interval for UN pressure receptacles, 
except for acetylene and composite cylinders and pressure receptacles 
used for certain specifically named gases; and
--Filling densities prescribed in P200 of the UN Model Regulations for 
UN pressure receptacle or the requirements in proposed Sec.  173.302b 
or Sec.  173.304b in this NPRM.

    Consistent with the current HMR, we are proposing to require UN 
pressure receptacles to meet the pressure relief requirements in Sec.  
173.301(f), and aluminum alloy oxygen cylinders to have straight 
(parallel) threads. In addition, we are proposing to require each new 
UN pressure receptacle and MEGC design type to be approved by the 
Associate Administrator and marked with the letters ``USA,'' to 
identify the United States of America as a country of approval. The USA 
country of approval marking will be required on all UN pressure 
receptacles manufactured within or being shipped to, from, or within 
the United States.

III. UN Pressure Receptacles and MEGCs--Design and Construction 
Requirements

    The UN Model regulations define four types of gas pressure 
receptacles--gas cylinder, pressure drum, tube and bundle of cylinders. 
As defined in the UN Model Regulations, a cylinder is a

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pressure receptacle with a water capacity not exceeding 150 liters. A 
pressure drum is a welded pressure receptacle with a water capacity 
exceeding 150 liters but not more than 1,000 liters. A tube is a 
seamless pressure receptacle with a water capacity exceeding 150 liters 
but not more than 3,000 liters. A bundle of cylinders is an assembly of 
cylinders that is fastened together, interconnected by a manifold and 
transported as a unit; the total water capacity of the bundle may not 
exceed 3,000 liters, or 1,000 liters when used for Division 2.3 gases.
    In this NPRM, we are proposing to adopt the UN Model Regulations 
requirements for seamless cylinders and tubes, bundles of cylinders, 
and MEGCs. The ISO has not finalized its design and construction 
standards for pressure drums or welded cylinders; therefore, we are not 
proposing to adopt these pressure receptacle requirements in this NPRM. 
Thus, the term ``pressure receptacle'' as used in this NPRM refers to 
cylinders and tubes.
    We are proposing to provide for a wider selection of pressure 
receptacles by providing for cylinders, tubes, and MEGCs constructed 
and certified to the referenced ISO standards and Part 178 
requirements. Our present DOT certification system for domestically 
manufactured seamless cylinders, with the exception of the 3B, 3BN and 
3E specifications, requires inspections and verifications of newly 
produced cylinders to be performed by independent inspection agencies 
(IIAs). With the exception of cylinders manufactured outside the United 
States and certain exemption cylinders, PHMSA does not conduct an audit 
of the cylinder manufacturer's operations prior to initial manufacture.
    In this NPRM, we are proposing to require each facility that 
manufactures UN pressure receptacles within the United States and 
foreign manufacturers of UN pressures receptacles used for transporting 
hazardous materials to, from or within the United States to be approved 
by the Associate Administrator. Approval of a pressure receptacle 
manufacturer will be accomplished through approval of:

--Each initial pressure receptacle design type. Prior to manufacture, 
each manufacturer of UN pressure receptacles will be required to have 
each initial pressure receptacle design type reviewed by an IIA and 
approved by the Associate Administrator.
--The pressure receptacle manufacturer's quality system. Each 
manufacturer of UN pressure receptacles will be required to have its 
quality system documented in the form of written policies, procedures, 
and instructions. A manufacturer's technical knowledge, skill and 
integrity are some factors that provide assurance to pressure 
receptacle purchasers and the general public that pressure receptacles 
comply with the HMR and are safe transport of hazardous materials. The 
current HMR requirements contain no formalized criteria for the 
assessment of these factors. Each manufacturer will be required to 
demonstrate its knowledge and technical expertise by manufacturing a 
production lot while being audited by PHMSA personnel.
--The production IIA. During the production run, this IIA has the 
responsibility for ensuring that each pressure receptacle produced by 
the manufacturer conforms to the applicable specification requirements. 
The current application procedures for IIAs in Subpart I of Part 107 
would apply. During PHMSA's audit of the pressure receptacle 
manufacturer, the production IIA will be required to perform all 
prescribed inspections and verifications during the production run.
--The proposed requirements in Sec.  Sec. 178.69 and 178.70 for the 
design and construction of pressure receptacles are consistent with 
those in the UN Model Regulations, except as noted in the following 
discussions. All pressure receptacles and MEGCs designed and 
constructed in full conformance with the applicable requirements will 
be marked with the UN designation, the letters ``USA,'' and the 
manufacturer's approval number. Any UN pressure receptacle or MEGC not 
marked in this manner and with the letters ``USA'' as a country of 
approval will not be authorized to be filled, offered or accepted for 
transportation within the United States. We believe this approach will 
maintain the high level of safety existing within the United States 
while facilitating trade worldwide.

A. Refillable Seamless Steel Cylinders

    This NPRM proposes to allow the use of refillable seamless steel 
cylinders designed, constructed, and tested to the following standards:
    ISO 9809-1 ``Gas cylinders--Refillable seamless steel gas 
cylinders--Design, construction and testing--Part 1: Quenched and 
tempered steel cylinders with tensile strength less than 1100 MPa.'' 
This standard specifies minimum requirements for the material, design, 
construction and workmanship, manufacturing processes, and tests at 
manufacture for refillable quenched and tempered seamless steel gas 
cylinders with water capacities from 0.5 liter up to and including 150 
liters. ISO 9809-1 is applicable to cylinders with a maximum tensile 
strength of 1,100 MPa for chrome-molybdenum steels or 1,030 MPa for 
carbon-manganese steels. However, a lower tensile strength applies when 
there is a risk of hydrogen embrittlement. The materials of 
construction are similar to those of DOT 3AA specification cylinders 
made of carbon manganese alloy steel.
    ISO 9809-2 ``Gas cylinders--Refillable seamless steel gas 
cylinders--Design, construction and testing--Part 2: Quenched and 
tempered steel cylinders with tensile strength greater than or equal to 
1100 MPa.'' This standard specifies minimum requirements for the 
material, design, construction and workmanship, manufacturing 
processes, and tests at manufacture for refillable quenched and 
tempered seamless steel gas cylinders with water capacities from 0.5 
liter up to and including 150 liters. ISO 9809-2 is applicable to 
cylinders with maximum tensile strength of greater than or equal to 
1,100 MPa.
    ISO 9809-3 ``Gas cylinders--Refillable seamless steel gas 
cylinders--Design, construction and testing--Part 3: Normalized steel 
cylinders.'' This standard specifies minimum requirements for the 
material, design, construction and workmanship, manufacturing 
processes, and tests at manufacture for refillable normalized or 
normalized and tempered seamless steel gas cylinders with water 
capacities from 0.5 liter up to and including 150 liters. Materials for 
the manufacture of normalized or normalized and tempered gas cylinders 
are generally classified as carbon-steels, carbon-manganese or 
manganese-molybdenum steels. The maximum tensile strength for cylinders 
made from these steels may not exceed 800 MPa. The materials of 
construction are similar to those of DOT 3A specification cylinders 
made of carbon or carbon manganese steel. ISO-9809-3 provides that 
other steels permitted in ISO 9809-1 or ISO 9809-2 for quenched and 
tempered cylinders may be used and subjected to normalizing and 
tempering, provided they additionally pass the impact test requirements 
specified in ISO 9809-1, and the tensile strength does not exceed 950 
MPa.
    Cylinders with water capacities less than 0.5 liter may also be 
manufactured and certified to ISO 9809-1, 9809-2 and 9809-3. Cylinders 
conforming to these standards are authorized for compressed, liquefied, 
and dissolved gases. These ISO 9809 standards require

[[Page 11771]]

that, following final heat treatment at manufacture, all cylinders 
except those selected for batch testing must be subjected to a 
hydraulic proof pressure test or a hydraulic volumetric expansion test. 
The standards permit the purchaser and the manufacturer to decide 
whether to perform the proof pressure test or volumetric expansion 
test. We consider the proof pressure test to be essentially a leak 
test. We are proposing to require this test to be a volumetric 
expansion test. The volumetric expansion test measures the cylinder's 
elastic expansion and ensures the adequacy of the physical properties 
of each cylinder. Further, this initial elastic expansion measurement 
offers a reference point, or benchmark, for use by requalifiers in 
evaluating whether the cylinder's wall elastic expansion remains within 
the prescribed parameters and the cylinder is safe for continued use.

B. Refillable Seamless Steel Tubes

    This NPRM proposes to allow use of refillable seamless steel tubes 
designed, constructed, and tested to the following standard: ISO 11120 
``Gas cylinders--Refillable seamless steel tubes of water capacity 
between 150 L and 3,000 L--Design, construction and testing.'' This 
standard specifies minimum requirements for the material, design, 
construction and workmanship, manufacturing processes, and tests at the 
time of manufacture for refillable quenched and tempered seamless steel 
tubes with water capacities from 150 liters up to and including 3,000 
liters for compressed and liquefied gases. ISO 11120 is applicable to 
tubes with a maximum tensile strength of less than 1,100 MPa, except 
tubes intended for hydrogen bearing gases are limited to a maximum 
tensile strength of 950 MPa.

C. Refillable Seamless Aluminum Alloy Cylinders

    This NPRM proposes to allow use of refillable seamless aluminum 
alloy cylinders designed, constructed, and tested to the following 
standard: ISO 7866 ``Gas cylinders--Refillable seamless aluminum alloy 
gas cylinders--Design, construction and testing.'' This standard 
specifies minimum requirements for the material, design, construction 
and workmanship, manufacturing processes, and tests at manufacture for 
refillable seamless aluminum alloy gas cylinders with water capacities 
from 0.5 liter up to and including 150 liters. The cylinders are for 
compressed, liquefied, and dissolved gases, other than acetylene.
    The UN Model Regulations permit the use of either tapered or 
straight (parallel) threads in aluminum alloy oxygen cylinders through 
the incorporation by reference of other ISO standards. However, we are 
not proposing to allow the use of tapered threads in aluminum alloy 
cylinders used in oxygen service and transported in the United States. 
This is consistent with Sec.  173.302(b) of the HMR, which requires 
each aluminum oxygen cylinder opening to be configured with straight 
threads only. Requiring the use of straight threads eliminates the 
possibility of a tapered threaded valve being inadvertently inserted 
into a straight threaded cylinder opening. Such a mismatch or cross 
connect could lead to a violent expulsion of the tapered thread valve 
or unintended release of oxygen.
    Within the United States, there are 20 million or more DOT 3AL 
aluminum alloy cylinders in oxygen service equipped with straight 
threads. Allowing the use of UN aluminum alloy oxygen cylinders with 
tapered threads, could increase the potential for inserting improper 
valves, even though the UN cylinders will be marked with the thread 
type code, e.g. 18P for straight or 25E for tapered. Persons who are 
not familiar with the ISO thread type codes may assume that the 
aluminum alloy oxygen cylinder is equipped with straight threads.
    The European countries have widely used tapered threads for all gas 
services; therefore, this mismatching concern may not exist. Although 
our experience within the United States is with straight thread 
designs, the use of both thread designs may offer certain advantages. 
We are asking commenters to address the impact of retaining the 
prohibition against using tapered threads in aluminum alloy oxygen 
cylinders.

D. Refillable Seamless Acetylene Cylinders

    This NPRM proposes to allow use of refillable acetylene cylinders 
complying with ISO 9809-1 or ISO 9809-3 and ISO 3807-2 ``Cylinders for 
acetylene--Basic requirements--Part 2: Cylinders with fusible plugs.'' 
ISO 9809-1 and ISO 9809-3 specify the details for design of the 
cylinder shell. ISO 3807-2 specifies the basic requirements for 
acetylene cylinders with a maximum nominal water capacity of 150 
liters, with shells made from steel and equipped with fusible plugs. It 
includes procedures for type testing, production batch testing, and the 
methods for determining the maximum permissible settled pressure in 
acetylene cylinders and the porosity of the porous mass.
    The UN Model Regulations also allow acetylene cylinder shells to be 
made of aluminum alloy conforming to ISO 7866. We are not proposing to 
allow the use of aluminum shells for acetylene cylinders transported in 
the United States. At manufacture, the cylinder shells are filled with 
a porous mass material and heat cured. The curing temperatures of the 
porous mass typically range from 260 [deg]C (500 [deg]F) to 371 [deg]C 
(700 [deg]F) for 24 to 48 hours, depending on the size of the cylinder, 
until the filler hardens. Exposing an aluminum cylinder to sustained 
high temperatures over long periods of time may adversely affect the 
structural integrity of the aluminum, thus making the cylinders unsafe 
for transportation. Because of this safety concern, we are proposing in 
this NPRM not to allow the manufacture and use of UN aluminum acetylene 
cylinders in the United States.
    In addition, paragraph 6.2.2.1.3 of the UN Model Regulations allows 
the manufacture and use of non-refillable acetylene cylinders without 
fusible plugs. The HMR do not authorize the manufacture or use of non-
refillable acetylene cylinders with or without fusible plugs. We have 
no shipping experience or safety data on the transportation of non-
refillable acetylene cylinders. Therefore, we are proposing that 
acetylene cylinders must be constructed of seamless steel, be 
refillable and equipped with fusible plugs. We are proposing to 
prohibit acetylene cylinders not meeting the proposed requirements from 
transportation and use in the United States.

E. Non-Refillable Metallic Cylinders

    This NPRM proposes to allow use of non-refillable metallic 
cylinders designed, constructed and tested to the following standard: 
ISO 11118 ``Gas cylinders--Non-refillable metallic gas cylinders--
Specification and test methods.'' This standard specifies minimum 
requirements for the material, design, construction and workmanship, 
manufacturing processes, and test at manufacture for non-refillable 
metallic gas cylinders of welded, brazed or seamless construction for 
compressed, liquefied and dissolved gases. As stated above in this 
preamble, we are proposing not to allow the manufacture or use of non-
refillable acetylene cylinders.

F. Refillable Composite Cylinders

    This NPRM proposes to allow use of refillable composite cylinders 
designed, constructed, and tested to the following standards:
    ISO 11119-1 ``Gas cylinders of composite construction--
Specification and test methods--Part 1: Hoop wrapped composite gas 
cylinders.'' This

[[Page 11772]]

standard specifies requirements for composite gas cylinders up to and 
including 450 liters water capacity, for compressed or liquefied gases 
with test pressures up to and including 650 bar. The cylinders consist 
of a seamless metallic liner over-wrapped with carbon fiber, aramid 
fiber, or glass fiber (or a combination thereof) in a resin matrix, or 
steel wire, to provide circumferential reinforcement.
    ISO 11119-2 ``Gas cylinders of composite construction--
Specifications and test methods--Part 2: Fully wrapped fibre reinforced 
composite gas cylinders with load-sharing metal liners.'' This standard 
specifies requirements for composite gas cylinders up to and including 
450 liters water capacity, for compressed or liquefied gases with test 
pressures up to and including 650 bar. The standard addresses fully-
wrapped composite cylinders with a load-sharing liner consisting of a 
seamless metallic liner over-wrapped with carbon fiber, aramid fiber, 
or glass fiber (or a combination thereof) in a resin matrix, to provide 
circumferential reinforcement.
    ISO 11119-3 ``Gas cylinders of composite construction--
Specifications and test methods--Part 3: Fully wrapped fibre reinforced 
composite gas cylinders with non-metallic and non-load-sharing metal 
liners.'' This standard specifies requirements for composite gas 
cylinders up to and including 450 liters water capacity, for compressed 
or liquefied gases with test pressures up to and including 650 bar. The 
cylinders are fully-wrapped composite cylinders with a non-load-sharing 
metallic or non-metallic liner. The cylinders consist of a liner over-
wrapped with carbon fiber or aramid fiber or glass fiber, or a mixture 
thereof, in a resin matrix to provide longitudinal and circumferential 
reinforcement.
    Depending on their construction, the UN Model Regulations specify 
design life for composite cylinders certified to ISO 11119-1, 11119-2 
and 11119-3 from a minimum design life of 10 years to an unlimited 
life. We are proposing to require composite cylinders to be designed 
and constructed to the unlimited life requirements while limiting the 
service life to not more than 15 years from the date of manufacture. 
Under the HMR, composite cylinders are currently authorized for 
construction only under the terms of a DOT exemption. The 15-year 
service life limitation is consistent with that imposed on composite 
cylinders authorized under exemptions.
    The ISO-11119-3 standard was adopted by the UN Sub-Committee of 
Experts in December 2004 for the manufacture and use of fully-wrapped 
composite cylinders with non-metallic and non-load-sharing metal 
liners. This standard also applies to composite cylinders without 
liners. Our experience within the United States is with fully-wrapped 
carbon-fiber reinforced (CFFC) and fiber reinforced plastic (FRP) 
composite aluminum-lined cylinders. We have no safety data on the use 
of composite cylinders with non-metallic and non-load-sharing metal 
liners or without liners. In this NPRM, we are proposing to prohibit in 
the United States the manufacture and use of fully-wrapped composite 
cylinders without liners. Under this proposal, ISO-11119-3 cylinders 
must have either a metallic or non-metallic (plastic) liner. Since the 
stress distribution of both ISO 11119-2 and 3 designs is handled by the 
composite shell rather than the liner, the major concern for plastic-
lined cylinders made in accordance with ISO 11119-3 is the permeation 
of toxic and flammable gases at high temperature ranges (130-154 
[deg]F). Therefore, in this NPRM we are proposing to prohibit the 
transportation of toxic gases or toxic gas mixtures meeting the 
criteria for Division 2.3, Hazard Zone A or B, in ISO 11119-3 
cylinders. When used for Division 2.1 materials, the cylinder will be 
required to have a working pressure not to exceed 62 bar. We are also 
proposing to prohibit the use of ISO 11119-3 cylinders for underwater 
breathing applications because of the effects of saltwater on some 
resins.

G. MEGCs

    A MEGC is an assembly of UN cylinders, tubes, or bundles of 
cylinders interconnected by a manifold and assembled within a 
framework. The term includes all service equipment and structural 
equipment necessary for the transport of the gases. We are proposing to 
prescribe the design type approval procedures and the manufacturing 
specification requirements for MEGCs in new Sec. Sec.  178.74 and 
178.75 respectively. The proposed requirements are based on the 
provisions in Sec.  178.275 of the HMR and paragraph 6.7.5 of the UN 
Model Regulations.

IV. Pressure Receptacles--Initial and Subsequent Design Type Review and 
Approval Process

    We are proposing to implement a conformity assessment system 
consistent with section 6.2.2.5 in the UN Model Regulations. Under this 
conformity assessment system, PHMSA, as the United States Competent 
Authority, will be responsible for implementing a system for providing 
overall approval of each pressure receptacle design type, the 
manufacturer's quality system, and inspection bodies. The conformity 
assessment system requirements in the UN Model Regulations were adopted 
on the basis of the requirements in ISO Technical Report 14600. The 
requirements are based on the practices used in Europe, Canada, and the 
United States for ensuring that cylinder quality is consistent with 
that prescribed in the ISO design and construction standards.
    The initial design type approval consists of an approval of the 
manufacturer's quality system and of the pressure receptacle design to 
be produced. (The manufacturer's quality system is discussed later in 
this preamble.) Under the proposed procedures for approval of the 
pressure receptacle design type, the manufacturer will select an 
inspection body, which, as proposed in this NPRM, will be an IIA 
approved by the Associate Administrator in accordance with the current 
procedures in Subpart I of Part 107. The manufacturer will submit an 
application for an initial design type approval to the IIA for review.
    The IIA will examine the manufacturer's application for an initial 
design type approval for completeness. If the application is 
incomplete, it will be returned to the manufacturer with an 
explanation. If the IIA verifies that the design conforms to the 
applicable standards and the requirements contained in Part 178 of the 
HMR, the manufacturer will fabricate a prototype lot of pressure 
receptacles in accordance with the design specification. The IIA will 
verify that the prototype lot conforms to the applicable requirements 
by witnessing the testing of selected pressure receptacles. If the 
prototype tests indicate that the pressure receptacles conform to all 
applicable requirements, the IIA will prepare a design type approval 
certificate and return the certificate documentation to the 
manufacturer. The manufacturer will submit the design application to 
the Associate Administrator for approval. Each application for an 
initial design type approval must contain the information specified in 
proposed Sec.  178.70, which includes: (1) The manufacturer's name and 
the manufacturing facility's address; (2) the designation of the 
pressure receptacle and the relevant pressure receptacle standard; (3) 
details of any similar approval application submitted to and denied by 
another country's competent authority; (4) technical documentation 
required for design type approval, such as design standards, 
manufacturing drawings, and design calculations; (5) test reports of 
the manufactured

[[Page 11773]]

prototype lot; and (6) documentation on the manufacturer's quality 
system.
    If the application, design drawings, and quality control documents 
are found satisfactory, PHMSA will schedule an on-site audit to assess 
the manufacturing and inspection processes, and test procedures. During 
the audit by PHMSA personnel, the manufacturer will be required to 
produce a group of cylinders to the technical standards for which 
approval is sought. During the production run, the production IIA will 
perform the required inspections and tests of newly manufactured 
cylinders. If the procedures and controls are deemed acceptable, test 
sample cylinders will be selected at random from the production lot and 
sent to a laboratory designated by PHMSA for verification testing. If 
the cylinder test samples are found to conform to all the applicable 
requirements, the Associate Administrator will issue approvals to the 
manufacturer and the production IIA to authorize the manufacture of the 
pressure receptacles. The manufacturer will bear the cost of the audit 
and verification testing.
    Under the system proposed in this NPRM, a manufacturer will be 
required to apply for a new design approval from the Associate 
Administrator for each new pressure receptacle design type or 
modification to an approved UN design type. A pressure receptacle will 
be considered to be of a new design, as specified in the referenced ISO 
design, construction, and testing standards, when:

    1. It is manufactured at a different facility;
    2. It is manufactured by a different process;
    3. It is manufactured from a material with chemical and 
mechanical properties different from those specified in the 
standard;
    4. Heat treatment differs from that specified in the standard;
    5. The base profile has changed (e.g., concave, convex, 
hemispherical) or there is a change in the base thickness/cylinder 
diameter ratio;
    6. The overall length of the cylinder has increased by more than 
50%;
    7. The nominal outside diameter has changed;
    8. The design wall thickness has changed;
    9. The hydraulic test pressure has been increased; or
    10. The guaranteed minimum yield strength and/or the guaranteed 
minimum tensile strength has changed.

    Requests for subsequent UN design type approvals will be reviewed 
by an IIA for design type approval, and approved by the Associate 
Administrator. The production IIA and the manufacturer will retain a 
set of the pressure receptacle design type approval documents for a 
minimum of 20 years. PHMSA has the authority to modify, suspend or 
terminate an approval certificate upon evidence that information upon 
which the approval was based is fraudulent or substantially erroneous, 
or such action is necessary to adequately protect against risks to life 
or property. The conditions for suspension or termination of an 
approval are in proposed Sec.  178.70.

V. MEGCs--Initial Design Type Review and Approval Process

    We are proposing to require MEGCs to be reviewed by an approval 
agency with authorization under the procedures in subpart E of Part 
107. The elements (pressure receptacle) installed in the MEGC will be 
approved as described in section IV of this preamble. The application 
procedure will be similar to that currently prescribed for the approval 
of IM and UN portable tanks in Sec.  178.273. The MEGC's manufacturer 
will submit the application to the approval agency. Each application 
must include all engineering drawings and calculations necessary for 
the approval agency to ensure that the MEGC design complies in all 
respects with the requirements in proposed Sec.  178.75 and 
documentation showing that the cylinders or tubes comprising the MEGC 
assembly are approved. An incomplete application will be returned to 
the applicant with an explanation.
    If an application is complete, the approval agency will review the 
design and arrange with the MEGC manufacturer to witness all required 
tests. Upon satisfactory completion of the prototype testing, the 
approval agency will prepare a design type approval certificate and 
return the certificate and documentation to the manufacturer. The 
manufacturer will submit the certificate and an approval application to 
the Associate Administrator. If the application and supporting 
documentation of the examination and tests performed are acceptable, 
the Associate Administrator will approve the certificate. The approval 
agency will be required to maintain a set of the approved drawings and 
calculations for each MEGC design it reviews and a copy of each initial 
design type approval certificate approved by the Associate 
Administrator for at least 20 years. The approval agency will ensure 
that each MEGC is manufactured to the design type and fully conforms to 
the applicable requirements. The approval agency will issue a 
certificate of compliance for each MEGC that is manufactured. The MEGCs 
will be certified and UN marked as prescribed in proposed Sec.  178.75.

VI. Qualification and Approval Process for Persons Performing Pressure 
Certifications

A. Inspection Bodies

1. Independent Inspection Agencies (IIAs)
    Current Sec.  107.803 of the HMR contains procedures and 
application criteria for a person seeking approval as an IIA to perform 
cylinder manufacture, repair or modification inspections and 
verifications prescribed in Parts 178 and 180. We propose to revise 
these requirements to include UN pressure receptacles. We are proposing 
to expand the criteria contained in Sec.  107.803 to permit the 
selection of any person or organization, foreign as well as domestic, 
for the duties of an IIA, that is technically competent to perform the 
prescribed functions. That person or organization must be free from 
undue influence by persons involved with the fabrication, ownership or 
movement of the cylinders that the applicant, if approved, would be 
called upon to evaluate and certify. If an applicant seeking approval 
to perform the functions of an IIA has its principle place of business 
in a country other than the United States, the Associate Administrator 
may approve the applicant on the basis of an approval issued by the 
Competent Authority of a foreign government. We will recognize UN 
pressure receptacles manufactured outside the United States and 
certified by an inspection body certified by another government if that 
government similarly accepts pressure receptacles manufactured in the 
United States and approved by an IIA approved by DOT. A foreign 
inspection body seeking approval from DOT to certify pressure 
receptacles manufactured outside the United States must submit evidence 
from that country stating that similar authority is delegated to IIAs 
and manufacturers of UN pressure receptacles in the United States and 
that no additional limitations are imposed that are not required of its 
own citizenry.
2. Approval Agencies
    Approval of MEGCs will be handled similarly to the approval of UN 
portable tanks. For a UN portable tank manufactured in the United 
States, we require the portable tank design type to be approved by an 
approval agency. The approval agency must be approved by the Associate 
Administrator under the procedures in Subpart E of Part 107. In new 
Sec.  178.74 of this NPRM, we are proposing to require each new MEGC 
design type to be reviewed by a DOT

[[Page 11774]]

designated approval agency. Authorization to perform functions relating 
to MEGCs must be contained in the approval agency's letter of 
designation.

B. Manufacturers

    The UN procedures for approval of a pressure receptacle 
manufacturer and the manufacturer's quality system are generally 
consistent with PHMSA's current procedures under Sec.  107.807 for 
cylinder manufacturers located outside the United States who perform 
the chemical analyses and tests of cylinders manufactured to DOT 
specifications. PHMSA currently performs an on-site audit of the 
manufacturing and test facilities after a pre-audit has been performed 
of the manufacturer's prototype design by an IIA.
    Under the proposed approval procedures, each manufacturer must have 
in place a documented quality system as outlined in proposed Sec.  
178.69. The manufacturer's quality system involves detailed 
documentation related to the UN pressure receptacles to be produced, 
and of written polices, procedures and instructions. The documentation 
must include (1) adequate descriptions of the organizational structure; 
(2) responsibilities of personnel with regard to design and product 
quality; (3) the design control and verification techniques; (4) 
cylinder manufacturing, quality control, quality assurance and 
operating instructions; (5) quality records, such as inspection 
reports, test data, and calibration data; (6) the process for control 
of documents and their revision; (7) means for control of non-
conforming gas cylinders, purchased components, in-process and final 
materials; and (8) the training for relevant personnel.
    The manufacturer's quality system will be audited by PHMSA during 
the final review of the initial design type approval, as prescribed in 
proposed Sec.  178.70. The Associate Administrator may perform periodic 
audits of approved manufacturers to ensure that the manufacturer's 
quality controls are maintained according to established standards.

C. Requalifiers

    Paragraph 6.2.2.6.2.1 of the UN Model Regulations provides that the 
competent authority must establish an approval system to ensure that 
the periodic inspection and testing of pressure receptacles conform to 
the specified requirements. Consistent with our current requirements in 
Sec.  107.805, any person who requalifies UN pressure receptacles must 
be approved by the Associate Administrator. Before a cylinder 
requalifier is approved and issued a requalification identification 
number (RIN), it must undergo a review and inspection for compliance 
with DOT requalification procedures; demonstrate knowledge of DOT 
cylinder regulations, and verify the accuracy of the calibration test 
equipment. Initially, the applicant will be required to submit an 
application containing specific information about its testing 
equipment, procedures, and knowledge. PHMSA will review all submitted 
documents and, if found satisfactory, the person seeking approval as a 
requalifier of UN pressure receptacles must arrange for an IIA, 
approved by the Associate Administrator, to inspect its facility. If 
the on-site audit reveals that the company has the required knowledge, 
capabilities and equipment, the Associate Administrator may issue a RIN 
to that facility to requalify UN pressure receptacles.

VII. UN Cylinders and Tubes--Requalification Requirements

    We are proposing to prescribe the requalification requirements for 
UN pressure receptacles in new Sec.  180.207. Proposed Table I 
specifies the periodic requalification interval. The standard 
requalification interval is once every ten years, with certain noted 
exceptions. A shorter requalification interval of once every five years 
will apply to pressure receptacles used for any Division 2.3 material, 
certain specifically named gases, and composite cylinders. These 
proposed requalification intervals are consistent with those prescribed 
in the UN Model Regulations.
    The requalification procedures for performing the inspections and 
test will be based on the applicable ISO standards, which depend on the 
pressure receptacle's material of construction. All refillable pressure 
receptacles must be given an internal and external visual inspection at 
the time the requalification is performed.
    Steel UN pressure receptacles constructed to ISO 9809-1, 9809-2, 
9809-3 with a tensile strength less than 950 MPa, will be required to 
be subjected to a visual examination and volumetric expansion pressure 
test in accordance with the procedures in ISO 6406. UN pressure 
receptacles constructed to ISO 9809-1 or ISO 9809-2 with a tensile 
strength greater than 950 MPa may be examined by a nondestructive 
method that is approved by the Associate Administrator. Aluminum UN 
pressure receptacles constructed to ISO 7866 will be required to be 
requalified in accordance with the procedures contained in ISO 10461. 
Both ISO 6406 and 10461 allow pressure receptacles to be pressure 
tested by either a volumetric expansion test or a proof pressure test, 
as appropriate for the design specification of the cylinder. We are 
proposing to require testing by the volumetric expansion test for 
pressure receptacles with a tensile strength of less than 950 MPa. The 
volumetric expansion test is an effective method for determining the 
elastic expansion, which is directly related to the wall thickness of 
the cylinder, and gives a numerical value that can be used to determine 
disposition of the cylinder. However, we are soliciting comments on 
whether requalification by a proof pressure test should be allowed 
under certain conditions. Note that as proposed in this NPRM, pressure 
receptacles with a tensile strength of 950 MPa or greater may be 
examined by a nondestructive method approved by the Associate 
Administrator.
    UN acetylene cylinders will be required to be requalified at 10 
year intervals in accordance with the procedures in ISO 10462, except 
the porous mass and shell must be requalified 3 years, +/-6 months from 
the date of manufacturer. UN composite cylinders will be required to be 
subjected to a complete visual inspection and a volumetric expansion 
test in accordance with the procedures in ISO 11623. These standards 
contain acceptance/rejection criteria for various types of defects or 
damage.
    The ISO standards do not address the repair of pressure 
receptacles. We are proposing to authorize limited repair work to UN 
pressure receptacles, under the terms of an approval issued by the 
Associate Administrator under Subpart H of Part 107. However, certain 
repairs, such as the external rethreading of UN tubes for remounting in 
a MEGC will not require an approval, provided certain conditions are 
met. These provisions are in proposed Sec.  180.212.

VIII. Pressure Receptacles--Filling Limits

    We are proposing to adopt the UN requirements applicable to the 
filling of UN pressure receptacles. Packing Instruction P200 of the UN 
Model Regulations establishes certain conditions that must be met when 
filling UN pressure receptacles with compressed gases and liquefied 
compressed gases. For compressed gases, the maximum filling limit 
(filling density) must be such that the working pressure (service 
pressure) is not greater than two-thirds of the test pressure, and in 
no case may the internal pressure at 65 [deg]C (149 [deg]F) exceed the 
test pressure of

[[Page 11775]]

the pressure receptacle. For high pressure liquefied compressed gases, 
the filling limit must be such that the settled pressure at 65 [deg]C 
(149 [deg]F) will not exceed the test pressure of the pressure 
receptacles. For low pressure liquefied gases, the maximum mass of 
contents per liter of water capacity must be less than or equal to 0.95 
times the density of the liquid phase at 50 [deg]C (122 [deg]F); in 
addition, the liquid phase may not fill the pressure receptacle at any 
temperature less than or equal to 60 [deg]C (140 [deg]F). The test 
pressure of the pressure receptacle must be at least equal to the vapor 
pressure (absolute) of the liquid at 65 [deg]C (149 [deg]F), minus 100 
kPa (1 bar).
    Packing Instruction P200 of the UN Model Regulations allows the 
maximum filling limit to be determined using specified formulas or 
filling ratio values provided for a given gas transported in cylinders 
with specified minimum test pressures. The formulas yield more 
conservative limits as compared to the values provided in Table 2 of 
P200 and are primarily intended to be used for gas mixtures. We are 
proposing to authorize any equally effective method for calculating the 
filling limits as long as the specified conditions for compressed and 
high and low pressure liquefied compressed gases are met. We are 
proposing in new Sec.  173.304b to include the formulas and to allow 
the use of either the formulas or filling limits in Table 2 of P200 of 
UN Model Regulations. A research study conducted to verify the filling 
formulas and specified limits may be reviewed by accessing the docket 
to this rulemaking at https://dms.dot.gov.

IX. Summary of Proposed Regulatory Changes by Part

    The following is a summary by part of the more significant 
proposals of this NPRM.

Part 107

    Sections 107.801, 107.803, and 107.805 contain application 
procedures for persons seeking approval to certify the manufacture, 
repair, rebuild or requalification of DOT specification cylinders. We 
are revising these provisions to include UN pressure receptacles and 
MEGCs.

Part 171

    In Sec.  171.7, we are proposing to incorporate by reference 
several additional ISO standards, and in Sec.  171.8, we are proposing 
to add definitions for ``bundles of cylinders,'' ``multiple element gas 
containers or MEGCs,'' ``UN cylinder,'' ``UN pressure receptacle,'' 
``UN tube'' and ``working pressure.''
    Sections 171.11, 171.12, and 171.12a permit hazardous materials to 
be transported in accordance with the ICAO Technical Instructions, the 
IMDG Code, and the Canadian Transport of Dangerous Goods (TDG) 
Regulations, respectively, under certain conditions. Each of these 
sections also includes a number of limitations applicable to such 
transportation. In this NPRM, we are proposing to add several 
limitations applicable to the use of DOT authorized cylinders and UN 
pressure receptacles transported in the United States under the ICAO 
Technical Instructions, the IMDG Code, and the TDG Regulations.
    We are proposing to clarify that, notwithstanding the requirements 
of the ICAO Technical Instructions, IMDG Code, and TDG Regulations, 
each pressure receptacle transported in accordance with Sec. Sec.  
171.11, 171.12, and 171.12a must be equipped with a pressure relief 
device (PRD) when required by Sec.  173.301(f) of the HMR. The UN Model 
Regulations, the ICAO Technical Instructions, IMDG Code, and the TDG 
Regulations provide that pressure receptacles must be equipped with a 
PRD when used for carbon dioxide (UN 1013), nitrous oxide (UN 1070) or 
required by the country of use. A PRD can prevent a dangerous build-up 
of pressure that could result in a cylinder leak or rupture. Therefore, 
in the interest of safety, pressure receptacles shipped to, from or 
within the United States must be fitted with PRDs consistent with the 
requirements in Sec.  173.301(f), including the PRD requirements in CGA 
Pamphlet S-1.1. As discussed earlier in this preamble, we are also 
proposing to require that the prototype design for all UN pressure 
receptacles manufactured or used for transporting hazardous materials 
within the United States must be approved by the Associate 
Administrator. These requirements are applicable to each pressure 
receptacle, including those assembled in MEGCs and bundles. Each 
approved pressure receptacle will be required to be marked with the 
letters ``USA'' followed by the manufacturer's approval number. This 
approach will readily identify the approved pressure receptacles and 
provide assurance that any UN pressure receptacle imported for use 
within the United States will be similar in strength, durability and 
quality as the DOT specification and UN pressure receptacles 
manufactured within the United States. To obtain a design type 
approval, the pressure receptacle manufacturers will be required to 
comply with the approval and manufacturing requirements proposed in 
Part 178 of this NPRM. As a part of the approval process, the pressure 
receptacle manufacturer's quality system and operating processes must 
be audited by PHMSA personnel as discussed earlier in this preamble. We 
believe this approach will maintain the high level of safety existing 
within the United States while facilitating trade worldwide.
    Readers should be aware that we are proposing other changes to 
Sec. Sec.  171.11, 171.12, 171.12a and certain other sections addressed 
in this NPRM under separate rulemaking actions. Therefore, the 
requirements proposed herein, if adopted in a final rule, may be placed 
in a different paragraph or section.

Part 172

    In Sec.  172.101, we are proposing to make various amendments to 
the Hazardous Materials Table (HMT). In a final rule published July 31, 
2003 (Docket No. RSPA 2002-13658 (HM-215E), 68 FR 44992), we revised 
eleven entries by removing the qualifying word ``compressed.'' The 
eleven entries are as follows:

1008 Boron triflouride
2417 Carbonyl fluoride
1911 Diborane
1962 Ethylene
2193 Hexafluoroethane or Refrigerant
2451 Nitrogen triflouride
2198 Phosphorous pentafluoride
2203 Silane
1859 Silicon tetrafluoride
1982 Tetrafluoromethane or Refrigerant gas R14
2036 Xenon

    We made the revisions for consistency with another amendment that 
revised the reference temperature used in the definitions of a non-
liquefied and liquified compressed gas Sec.  173.115(d) and (e), 
respectively, from 20 [deg]C (70 [deg]F) to -50 [deg]C (-58 [deg]F), 
consistent with internationally accepted definitions for gases adopted 
in the Twelfth Edition of the UN Model Regulations.
    We also divided the compressed liquefied gases into high and low 
pressure categories. In the July 31, 2003 final rule, we stated that in 
a separate rulemaking we would address whether the named gases should 
be reassigned to more appropriate packaging sections. We also stated 
that we would address the use of the high- and low-pressure compressed 
liquefied gas designations. Upon further consideration, we believe the 
packaging authorizations should remain in Sec.  173.302 rather than 
being reassigned to other packaging sections. The UN Model Regulations 
define a ``compressed gas,'' as a gas that when packaged under pressure 
for transport, is entirely gaseous at -50 [deg]C (-58 [deg]F); this 
category includes all gases with a

[[Page 11776]]

critical temperature less than or equal to -50 [deg]C (-58 [deg]F). The 
UN Sub-Committee of Experts removed the descriptor ``compressed'' from 
the shipping names because the gases are partially liquid at 
temperatures above -50 [deg]C (-58 [deg]F) when packaged under pressure 
for transport. We believe these gases seldom encounter temperatures of 
-50 [deg]C (-58 [deg]F) and below when transported within the United 
States and, therefore, changing the packaging authorizations is not 
warranted. However, we are soliciting comments on whether the packaging 
authorization for these gases should remain as Sec.  173.302 or be 
relocated to Sec.  173.304.
    We are proposing to add seven new special provisions to certain 
entries in the HMT. New special provision N86 would be added to 21 
entries. The special provision prohibits the shipment of these gases in 
UN pressure receptacles made of aluminum. The 21 entries are as 
follows:

1001 Acetylene
1017 Chlorine
1037 Ethyl chloride
1045 Fluorine, compressed
1048 Hydrogen bromide, anhydrous
1050 Hydrogen chloride, anhydrous
1052 Hydrogen fluoride, anhydrous
1062 Methyl bromide
1063 Methyl chloride or Refrigerant gas R 40
1085 Vinyl bromide, stabilized
1086 Vinyl chloride, stabilized
1581 Chloropicrin and Methyl bromide mixture
1582 Chloropicrin and Methyl chloride mixture
1749 Chlorine trifluoride
1860 Vinyl fluoride, stabilized
1912 Methyl chloride and Methylene chloride mixture
2190 Oxygen difluoride, compressed
2196 Tungsten hexafluoride
2197 Hydrogen iodide, anhydrous
2548 Chlorine pentafluoride
2901 Bromine chloride

--New special provision N87 would be added to eight entries. The 
special provision prohibits the shipment of these gases in UN pressure 
receptacles with copper valves. The eight entries are:

1005 Ammonia, anhydrous
1032 Dimethylamine, anhydrous
1036 Ethylamine
1043 Fertilizer ammoniating solution with free ammonia
1061 Methylamine, anhydrous
1083 Trimethylamine, anhydrous
2073 Ammonia solution, relative density less than 0.880 at 15 [deg]C 
in water, with more than 35% but not more than 50% ammonia.
3318 Ammonia solution, relative density less than 0.880 at 15 [deg]C 
in water, with more than 50% ammonia.

--New special provision N88 would be added to three entries. The 
special provision provides that the UN pressure receptacle's metal 
parts in contact with the gas must contain no more than 65% copper. The 
three entries are:

1001 Acetylene, dissolved
1060 Methyl acetylene and propadiene mixtures, stabilized
2452 Ethylacetylene, stabilized

--New special provision N89 would be added to fourteen entries. The 
special provision provides that when steel UN pressure receptacles are 
used, only those bearing an ``H'' mark are authorized. The fourteen 
entries are:

1048 Hydrogen bromide, anhydrous
1049 Hydrogen, compressed
1050 Hydrogen chloride, anhydrous
1053 Hydrogen sulphide
1064 Methyl mercaptan
1911 Diborane
1957 Deuterium, compressed
2034 Hydrogen and Methane mixture, compressed
2188 Arsine
2192 Germane
2197 Hydrogen iodide, anhdrous
2199 Phosphine
2203 Silane
2600 Carbon monoxide and Hydrogen mixture, compressed

Part 173

    In Part 173, we are proposing to add authorizations for the use of 
UN pressure receptacles in a number of sections consistent with the 
requirements in the UN Model Regulations. In Sec.  173.40, we are 
proposing to limit a UN cylinder used for Hazard Zone A or B material 
to a maximum water capacity of 85 liters. The cylinder must have a 
minimum test pressure of 200 bar and a minimum wall thickness of 3.5 mm 
if made of aluminum alloy or 2 mm if made of steel or, alternatively, 
be packed in an outer packaging meeting the Packing Group I performance 
level. We are prohibiting the transport of Hazard Zone A material in UN 
tubes and MEGCs.
    In Sec.  173.301, we are proposing to revise the general 
requirements for shipment of hazardous materials in cylinders to apply 
to UN pressure receptacles. However, UN pressure receptacles would not 
be required to meet the requirements for cylinder valve protection in 
paragraph (h) and for cylinders mounted on a motor vehicle or in frames 
in paragraph (i). These particular requirements for UN pressure 
receptacles would be contained in new Sec.  173.301b. The requirements 
applicable to MEGCs would be contained in new Sec.  173.312.
    New Sec.  173.301b would contain additional general requirements 
for the shipment of hazardous materials in UN pressure receptacles. We 
are proposing that gas or gas mixtures must be compatible with the 
pressure receptacle and valve material in accordance with ISO 11114-1 
for metallic materials or ISO 11114-2 for non-metallic materials. When 
a refillable pressure receptacle is filled with a gas different from 
that previously contained in the cylinder, prior to refilling, the 
cylinder must be cleaned in accordance with ISO 11621. A UN pressure 
receptacle must have its valve protected in accordance with the methods 
prescribed in Sec.  173.301(h). Finally, under paragraph (g), a non-
refillable UN pressure receptacle will be required to have a water 
capacity not exceeding 1.25 liters and must be transported as an inner 
packaging. The use of a non-refillable UN pressure receptacle would be 
prohibited for a toxic gas with an LC50 of 200 ml/mg or 
less.
    New Sec.  173.302b would contain the filling requirements for UN 
pressure receptacles used to transport non-liquefied (