A sidewall burst failure of a high-pressure polytetrafluoroethylene-lined hose was experienced. The 4.0-m hose was 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. Failure of the hose occurred while 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.
Examination of the hose provided additional information. Failure of the hose occurred approximately 30 cm from the crimped end fitting. The hose contained three distinct kinks, or bent areas, all 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.
High-pressure fueling 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.