1 Scope
1.1 General
1.1.1
This Standard establishes minimum requirements for pressure relief devices (PRDs) intended for use on fuel containers that comply with ANSI/CSA NGV2, 49 CFR Part 571.304 (FMVSS 304), CSA B51, Part 2, and/or ISO 11439.
PRDs can be of any design or manufacturing method that meets the requirements of this Standard.
1.1.2
This Standard does not apply to reseating or resealing devices.
1.1.3
PRDs designed to comply with this Standard are expected to be used with natural gas fuel containing no more than 2% hydrogen by volume.
1.2 Relevant documents
Documents which apply to fuel container installation and vehicle systems include 49 CFR Part 571.303 (FMVSS 303), TC 301.2, NFPA 52, CSA B109, and CSA/ANSI NGV 6.1.
Other regulations, standards, or codes may permit or require the use of PRDs certified to comply with this Standard. Additional service conditions or requirements beyond the scope of this document are the responsibility of those standards development organizations or the authority having jurisdiction.
1.3 Informative annex
Annex A presents an informative record of the recommended fuel container, fuel storage subsystem, and vehicle level requirements that were identified by the Subcommittee during the development of this Standard. As this Standard contains component level requirements, these recommendations are outside the scope of this document.
Annex A statements are intended as recommendations for consideration of inclusion to the organizations and committees developing these subsystem and vehicle level standards.
1.4 Notes
Fuel containers might accidentally be exposed to fire or elevated temperature. These conditions could act to increase the contained pressure and/or to degrade the structural materials, depending on the container type and materials of construction. A PRD provides a means to vent the fuel container under these conditions.
A specific PRD might not be suitable for all container types, sizes, and/or installations. Fuel container or installation standards may require that a PRD be tested in conjunction with other components.
CGA S-1.1 states “relief devices may not prevent burst of a cylinder under all conditions of fire exposure. When the heat transferred to the cylinder is localized, intensive, and remote to the relief device, or when the fire builds rapidly, such as in an explosion, and is of very high intensity, the cylinder can weaken sufficiently to rupture before the relief device operates, or while it is operating”.
1.5 Terminology
In this Standard, “shall” is used to express a requirement, i.e., a provision that the user is obliged to satisfy in order to comply with the standard; “should” is used to express a recommendation or that which is advised but not required; and “may” is used to express an option or that which is permissible within the limits of the Standard.
Notes accompanying clauses do not include requirements or alternative requirements; the purpose of a note accompanying a clause is to separate from the text explanatory or informative material.
Notes to tables and figures are considered part of the table or figure and may be written as requirements.
Annexes are designated normative (mandatory) or informative (nonmandatory) to define their application.
1.6 Units
The values given in SI units are the units of record for the purposes of this Standard. The values given in parentheses are for information and comparison only.