Mechanical Impact of Medical Oxygen Cylinders
Over the past thirty years a handful of fires, in medical oxygen high pressure gas storage systems involving aluminum alloy cylinders, have been deemed to be associated with mechanical impact-induced ignition of a contaminated system. For example, mechanical impact ignition of hydrocarbon contamination in a cylinder which was dropped during transportation. While the number of these incidents is minuscule compared to the number of systems used in the field, the effect is significant when such an ignition occurs. However, the kindling chain and initial ignition point of these fires is poorly understood.
WHA's Mechanical Impact System is capable of rotating valves during the impact as shown in the animation video (right).
Although made from more oxygen compatible metallic materials, the cylinder valves attached to these aluminum cylinders contain nonmetallic materials and are in direct contact with the cylinder threads, which are the thinnest cross-section of the cylinder.
WHA developed a mechanical impact test to investigate the conditions required to cause ignition of a cylinder and valve assembly by this ignition mechanism, with and without a wide range of controlled contaminants. The test system is capable of remotely pressurizing cylinders with oxygen while secured under a drop tower capable of delivering energies up to 434 J (320 ft.lb).