Filling and Purging Requirements for High Pressure Containers (23)

Criticality: Medium
Progress: Not Addressed
Score: 24
DOT Relevance: §173.302

Description of Key Area

High pressure hydrogen storage technologies are being developed to address the low storage density—both gravimetric and volumetric—of gaseous hydrogen. Fast filling of high pressure gaseous hydrogen containers can result in significant gas temperature increases due to heat of compression. Plastic lined composite containers can have material temperature limits that can be exceeded if proper procedures and controls are not employed. Additionally, thermally-activated pressure relief devices could suffer thermal degradation from repeated exposure to high gas temperatures. Purging of plastic-lined containers Rapid depressurization of plastic lined containers can place potentially harmful thermal stresses on sealing/mating areas between the plastic liner and metal connecting hardware (bosses). Also, it also not generally recommended to bring the internal pressure of a plastic-lined container appreciably below atmospheric pressure as the vacuum pressure can lead to the separation of the liner from the structural composite overwrap, potentially damaging the liner.

Discussion of Criticality

It is anticipated that as these storage technologies develop, their proponents will determine any unique conditions or procedures for container filling. It is also anticipated that as early products are brought to market, initial regulatory coverage will be via special permits which will likely require filling to be performed by the manufacturer or their designated agents, providing a level of control over the filling process through manufacturers’ developed practices.

Discussion of Progress

Most high pressure storage technologies are currently being developed for vehicular applications and are at the prototype stage. They are not yet in use for hydrogen transport. Progress was assessed as “Not Addressed”.

Recommendations

As development and deployment activities increase, initially the special permit process could be used to incorporate any special handling requirements during filling. With sufficiently wider deployment, requirements could be considered for incorporation into regulatory structure.