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Federal Register / Vol. 86, No. 151 / Tuesday, August 10, 2021 / Proposed Rules
Model Regulations and does not expect any degradation of safety standards in association with the use of these two documents. Additionally, PHMSA
proposes to add an end date of December 31, 2022 to the authorization to use ISO 10297:2014 when not used in conjunction with the supplemental 2017
amendment, ISO 10297:2014/Amd 1:2017.
Also in this paragraph, PHMSA
proposes to amend references to ISO
14246, Gas cylindersCylinder valvesManufacturing tests and examinations. Currently paragraph d2 states that valves must be initially inspected and tested in accordance with ISO 14246:2014E, Gas cylinders Cylinder valvesManufacturing tests and examinations. However, in 2017, ISO published ISO 14246:2014/Amd 1:2017, Gas cylindersCylinder valvesManufacturing tests and examinations, which provides supplemental amendments pertaining to specific pressures to be used in the pressure test and leakproofness test of acetylene valves. PHMSA proposes to require the use of this amended document in 178.71 to require acetylene valve users to use the updated values in ISO 14246:2014/Amd 1:2017.
PHMSA has reviewed these documents as part its regular participation in the review of amendments proposed for the UN Model Regulations and does not expect any degradation of safety standards in association with the use of these two documents. PHMSA also proposes to add analogous compliance requirements for self-closing valves to paragraph d2. ISO 17879:2017Gas cylindersSelf-closing cylinder valvesSpecification and type testing, specifies the design, type testing, marking, and manufacturing tests and examinations requirements for selfclosing cylinder valves intended to be fitted to refillable transportable gas cylinders which convey compressed, liquefied, or dissolved gases.
Additionally, PHMSA proposes to amend paragraph l1, which specifies the design and construction requirements for UN composite cylinders and tubes. The proposed change would add a new subparagraph iv to reference ISO 111194:2016, Gas cylindersRefillable composite gas cylindersDesign, construction and testingPart 4: Fully wrapped fibre reinforced composite gas cylinders up to 150 L with load-sharing welded metallic liners. This document, which was adopted in the UN Model Regulations, specifies requirements for composite gas cylinders with load-sharing welded liners between 0.5 L and 150 L water capacity and a maximum test pressure
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of 450 bar for the storage and transportation of compressed or liquefied gases. PHMSA incorporates by reference the first three parts of the ISO
11119 series, which cover various designs of composite cylinders with a seamless liner. This fourth part defines the requirements for design, construction, and testing of composite cylinders with a welded metallic liner.
Incorporating this ISO standard would eliminate the need and associated burden for manufacturers to request a special permit to construct fully wrapped fiber reinforced composite gas cylinders with load-sharing welded steel liners.30
Finally, PHMSA proposes to amend paragraph o1 of this section to update the reference to ISO 111141:2012E, Gas cylindersCompatibility of cylinder and valve materials with gas contentsPart 1: Metallic materials.
ISO 111141:2012 provides requirements for the selection of safe combinations of metallic cylinder and valve materials and cylinder gas content. PHMSA proposes to amend the compatibility requirements to also require compatibility with the 2017
supplement to ISO 111141:2012, ISO
111141:2012/Amd 1:2017 for material compatibility requirements. Permitting the use of this document would allow shippers to safely transport a wider variety of gases in newly developed types of metallic cylinders and valves.
PHMSA has reviewed this document as part of its regular participation in the review of amendments proposed for the 21st revised edition of the UN Model Regulations and expects that adding it to the HMR will enhance the current safety of hazardous materials in transportation, in addition to harmonizing the HMR with international requirements. This amendment provides compatibility requirements for the selection of combinations of metallic cylinder and valve materials for use with gas or gas mixtures. In the interest of providing uniformity with regard to reference standards used domestically and internationally, PHMSA proposes to revise the compatibility requirements to also refer to the 2017 amendment of this ISO standard. This 2017 supplemental amendment provides more explicit instructions on the permissible concentrations of certain gases. PHMSA
has determined that permitting the use of this updated document would allow safe transport of a wider variety of gases in newly developed types of metallic 30 See, e.g., Special Permit 14457 Dec. 16, 2019, which served as the technical basis for the development of ISO 111194:2016.

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cylinders and valves without compromising safety.
Section 178.75
Section 178.75 prescribes specifications for multiple-element gas containers MEGCs, which are assemblies 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 gases including hazardous materials marked as Division 2.1 such as compressed hydrogen. PHMSA
proposes to revise paragraph d to permit explicitly the use of composite construction, which is allowed for other pressure vessels i.e., cylinders, rather than limiting authorized material of construction for an MEGC to seamless steel as in the current HMR. Composite cylinders are constructed of carbon, fiberglass, or a hybrid composite with high-strength aluminum liners. When the specifications for MEGCs were originally created, there were no standards for composite pressure receptacles in the international transport standards or the HMR. In the decades since standards for the use of ISO composite pressure receptacles have since been developed and authorized. International standards did not consider a corresponding allowance to use these composite pressure receptacles as elements of MEGCs when the specifications were originally adopted. The 21st revised edition of the UN Model Regulations have since been updated to include such an authorization and PHMSA proposes to similarly allow the use of composite pressure receptacles in MEGCs.
To that end, PHMSA is adding references to the following ISO design standards for composite MEGCs: ISO
111191:2012E, Gas cylinders Refillable composite gas cylinders and tubesDesign, construction and testingPart 1: Hoop wrapped fibre reinforced composite gas cylinders and tubes up to 450 L, ISO 11119
2:2012E, Gas cylindersRefillable composite gas cylinders and tubes Design, construction and testingPart 2: Fully wrapped fibre reinforced composite gas cylinders and tubes up to 450 l with load-sharing metal liners, and ISO 111193:2013E, Gas cylindersRefillable composite gas cylinders and tubesDesign, construction and testingPart 3: Fully wrapped fibre reinforced composite gas cylinders and tubes up to 450 L with non-load-sharing metallic or nonmetallic liners. The 19th revised edition of the Model Regulations
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