Compressed natural gas vehicle fuel containers

1.1 General
This Standard contains requirements for the material, design, manufacture, and testing of serially produced, refillable Type NGV 2 containers intended only for the storage of compressed natural gas for vehicle operation. These containers are to be permanently attached to the vehicle. This Standard applies to containers up to and including 1000 L (35.4 ft3) water capacity.
1.2 Container type
1.2.1Type NGV 2 containers are designated as follows:
a)Type 1: metal;
b)Type 2: resin-impregnated continuous filament with metal liner with a minimum burst pressure of 125% of service pressure. The container is hoop-wrapped;
c)Type 3: resin-impregnated continuous filament with metal liner. The container is full-wrapped; and
d)Type 4: resin-impregnated continuous filament with a nonmetallic liner.
1.2.2Conformable container types are designated as follows:
a)CT1: container or assembly of a non-spherocylindrical or non-spherical (i.e., irregular) shape without a protective shell (i.e., outside wall containing gas pressure);
b)CT2: container or assembly of possibly irregular shape within a conformable protective shell that is acting as a shield and not directly assisting the inner container with containing gas pressure; and
c)CT3: container or assembly of possibly irregular shape within a conformable protective shell that is acting as a shield and directly assisting the inner container with containing gas pressure.
The conformable container types are an additional identifier that is used in combination with the container type. A conformable tank is designated based on the design as a Type 1 (metal) to Type 4 (resin-impregnated continuous filament with a nonmetallic liner) with the additional conformable type identifier. For example, a Type 4 CT2 container would be required to meet the criteria for a Type 4 container as well as the criteria specified for a CT2 container.
1.3 Alternative construction or materials
All specifications as to construction or materials set forth herein may be satisfied by the construction or materials actually prescribed or such other construction or materials that will provide at least equivalent level of performance. Additional tests may be required to evaluate potential failure modes that pertain to new construction or materials that are not specifically addressed in this Standard.

1.4 Units of measure
This Standard contains SI (metric) units with yard/pound quantities for reference purposes so as to allow the Standard to be followed using SI (metric) units. IEEE/ASTM SI 10 or ISO 80000-1 is used as a guide in making metric conversion from inch/pound quantities. If a value for a measurement and a corresponding value in other units are stated, the first stated value is regarded as the requirement. The given corresponding value may be approximate. If a value for a measurement and a corresponding value in other units are both specified as a quoted marking requirement, the first stated unit or both are to be provided.
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 (non-mandatory) to define their application.