UN cylinders, UN tubes, UN cryogenic receptacles, and multiple-element gas containers (MEGCs)

CSA B341

Information on CSA B341 (the standard on "UN pressure receptacles and multiple-element gas containers for the transport of dangerous goods").

CSA B342

Information on CSA B342 (the standard on "Selection and use of UN pressure receptacles and multiple-element gas containers for the transport of dangerous goods, Class 2").

FAQ on UN cylinders and UN tubes

The FAQ on UN Cylinders and UN tubes includes information on Transport Canada requirements including the registration requirements for UN cylinder and UN tube manufacturers, inspection bodies, and periodic inspection and test bodies, and information on the selection and use of UN cylinders and tubes for transport of dangerous goods in Class 2.

Standards on UN Cylinders, Tubes, and Multiple-Element Gas Containers for Use in Canada

CSA Standard B341, UN pressure receptacles and multiple-element gas containers for the transport of dangerous goods; and

CSA Standard B342, Selection and use of UN pressure receptacles and multiple-element gas containers for the transport of dangerous goods, Class 2.

These standards establish domestic requirements for Canada in relation to UN cylinders, tubes, and multiple-element gas containers (MEGCs) for transport of dangerous goods included in Class 2, Gases.

Both these standards, which reflect use and safety experience, and advances in technology and industrial practices, are closely harmonized with the United Nations Recommendations on the Transport of Dangerous Goods (UN Model Regulations). Gas cylinders and tubes are referred collectively as “pressure receptacles” by the UN. A MEGC is an assembly of UN pressure receptacles (elements) interconnected by a manifold and assembled within a framework and includes the service and structural equipment necessary for the transport of gases. Such assemblies are the high-pressure equivalents of tank containers, referred to as portable tanks by the UN, and are suitable for carrying gases in all modes. The requirements for UN pressure receptacles are based on standards published by the International Organization for Standardization (ISO). The relevant International Standards are produced by ISO technical committee ISO/TC58, Gas Cylinders, and its three subcommittees – SC2, Cylinder fittings, SC3, Cylinder Design and SC4, Operational requirements for gas cylinders. Transport Canada has and continues to participate in the development of the relevant ISO standards as a committee member representing the Standards Council of Canada, the ISO member body for Canada.

The CSA B341 standard prescribes the requirements for the manufacture of UN pressure receptacles and MEGCs under the authority of the “competent authority” of Canada (Transport Canada). CSA B341 also prescribes the requirements that must be met for periodic inspection and testing (requalification) of UN pressure receptacles and MEGCs. The intervals for the periodic inspection and testing are specified in CSA B342.

The CSA B341 standard requires that any UN pressure receptacle or MEGC manufacturer wishing to manufacture pressure receptacles or MEGCs under that standard must obtain approval for their pressure receptacle or MEGC designs and their quality system from Transport Canada. CSA B341 details the information that must be submitted by the manufacturer, which will then be verified for compliance with the standard by departmental staff as a condition for approval (called “registration” by the standard). A UN pressure receptacle or MEGC manufacturer would be authorized to display the “CAN” “country of approval” certification safety mark, the UN packaging symbol, and the other prescribed certification markings under CSA B341, only on pressure receptacles and MEGCs covered by a certificate of registration issued by Transport Canada under CSA B341. These requirements would apply regardless of where a UN pressure receptacle or MEGC manufacturer is located, whether in Canada or abroad.

The CSA B342 standard prescribes the selection requirements for UN pressure receptacles in relation to the gas to be contained, and prescribes other limits and requirements on the use of UN pressure receptacles and MEGCs in Canada. The CSA B342 standard also prescribes the requirements for the design and testing of gas cylinder valves, valve protection, and pressure-relief devices. The use requirements and limits on UN pressure receptacles differ considerably in their detail from the requirements currently applicable to currently existing domestic cylinders and tubes in Canada. Therefore UN pressure receptacles will be required to be used for Class 2 dangerous goods in Canada in accordance with CSA B342, whereas the use of current (“TC”) cylinders and tubes will still be governed under CSA B340.

What are some differences between UN pressure receptacles and “TC” cylinders? The markings, the filling limits, and the requalification intervals are among the notable differences. The following is an example of markings applied to a UN cylinder:

The top row contains manufacturing marks such as the cylinder thread type, the country of manufacture, and the serial number assigned by the manufacturer. The middle row contains operational marks such as the test pressure, the tare or empty weight, and the minimum guaranteed wall thickness. The bottom row contains certification marks such as the UN packaging symbol, the ISO standard used for the design, manufacturing, and testing, and the country of approval. Please consult CSA B341 for more details on the marking requirements.

The filling requirements of UN pressure receptacles, as set out in CSA B342, are based on those prescribed in Packing Instruction P200 of the UN Model Regulations and represent significant advances in harmonizing filling ratios for gases in cylinders.

For most UN pressure receptacles, the requalification period is 10 years. For UN composite cylinders and other UN pressure receptacles used for toxic gases, the requalification period is 5 years.

The accomplishment of new technical requirements for pressure receptacles through the UN Model Regulations is a significant and welcome achievement. Nonetheless, although the provisions in relation to pressure receptacles in the UN Model Regulations now enjoy international support for their technical adequacy, the operation of those provisions in terms of national implementation and mutual recognition of approvals between international competent authorities remains an issue. Although most other UN container types are accepted for use in most countries on the strength of the approval issued by the country of manufacture, this is not generally the case for UN pressure receptacles any more than it has been the case of pressure receptacles approved under national standards.

Between Canada and the United States the issue of mutual recognition of regulatory approvals for UN pressure receptacles has been addressed. CSA B342 recognizes for use in Canada UN pressure receptacles bearing the country of approval mark “USA” applied in accordance with Title 49 of the U.S. Code of Federal Regulations (49 CFR), in like manner to pressure receptacles approved under CSA B341 with the “CAN” country of approval mark. In paragraph 171.12(a)(4) of 49 CFR, as amended by the recent HM-215F rulemaking, UN cylinders with the “CAN” country of approval mark are recognized for use in the United States equally to UN cylinders with the “USA” country of approval mark. Users of UN “CAN” or UN “USA” cylinders will therefore benefit from reciprocal recognition of regulatory approvals not currently afforded to the cylinder under existing regulations.

It must be emphasized that these standards were not prepared with the intention of removing existing requirements for “TC” cylinders; rather, they were developed to incorporate the ISO standards as referenced in the UN Model Regulations as an optional means of compliance and hence to provide for a broader selection of containers for transport of gases. Therefore cylinder manufacturers wishing to continue the manufacture of existing cylinder types and users wishing to continue their current practices would not be affected by the introduction of these container types. By increasing the variety of containers available to Canadian shippers of gases, we expect there to be opportunities for increased efficiency and reduced costs to industry along with a more effective promotion of public safety.

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