Hose rupture at a HRS

A dispenser hose failed at a hydrogen refuelling station. It ruptured with a sidewall burst, approximately 30 cm from the crimped end fitting.

The hose had experienced a total of aproximately 300 filling cycles. The rupture occurred while it was temporarily connected to a gas booster, after 1-2 hours of service at 75 MPa. There were no tight bends in the hose during its final service application and no vibration present in the assembly.

The post-rupture examination revealed that the hose contained three distinct kinks, or bent areas, within the immediate area of the failure. However, the burst area did not show any obvious signs of previous damage or flaws. Some strands of the metal braiding exhibited corrosion attack, as well as gouge-type mechanical damage, but no fatigue characteristics or discontinuities were noted on the failed strands that were examined.

[H2TOOLS]

dispenser hose

The hose was high-pressure polytetrafluoroethylene-lined, 4.0 m long. It had been in service for approximately two years, primarily for 70 MPa fueling of hydrogen at ambient conditions ranging from -40 C to +50 C.
The total number of fills during its service life was estimated to be 150. In addition to the high-volume fill events, pressure cycling occurred as part of the routine test procedures and operational protocols. These additional pressure-cycling occurrences were approximated to be 200-250 cycles. During each filling cycle, the hose was allowed to bend during connections, as required by the situation.

H2TOOLS provided these recommendations:
“High-pressure fuelling hoses should be examined daily for signs of external damage, including corrosion, abrasion, cuts, and kinking. High-use fueling hoses should be replaced every six months.”
The basis for these recommendations is however unclear, because (i) the material-related cause of the rupture is not found, (iii) the nominal lifetime of the hoses is not provided, and (iii) leak testing procedures and the replacement strategy of the station are unknown. Also unknown is the specific design of the hose, and the reason why it was temporary connected to a booster.
In other cases of leaking hoses, for example HIAD events 702, 1196 and 1202, failures consisted in a complex series of events involving various material layers, and only a detailed micro-structural investigation could identify causes and recommendations.
A final caveat: the 75 MPa filling hose technology has evolved rapidly sicen the date of this event, improving design and material quality assurance. Also testing and maintenance protocols were adapted, component lifetime extended. so that recommendations on old events for this technology may be no more valid 10 years later.