Hydrexia’s systems have considerable safety benefits over compressed gas.
Due to low pressure operation, if there is a leak in the system, the flammable zone around the leak is much smaller than for compressed gas systems.
There is also much less gaseous hydrogen, most of it being in metal hydride form, and so in the event of a leak or a major rupture of the tank, only this small amount of gas can escape. Magnesium is a flammable metal, and ball milled metal hydrides are susceptible to spontaneously combusting in air. Hydrexia’s material is stable in air when it is in alloy form, as well as when it has been activated, whether it contains hydrogen or not. This has been tested by exposing it to air and water according to the test procedures of the Japanese Hazardous Material Regulation.
The image on the right illustrates the procedure of exposing the metal hydride powder to water through a filter paper, while holding a flame directly above the sample. Experimentation has also shown that when the material contains hydrogen, it is more difficult to extract the hydrogen from the material in an air atmosphere than when it is in a hydrogen or inert atmosphere.
The magnesium alloy is handled in macroscopic flake form during system manufacturing. This avoids the risks associated with handling a flammable powder, which would otherwise be explosive when mixed with air. Within the system, the flakes break down into much smaller particles as mentioned earlier, but these then sinter together to form a solid porous material, and so in the event of a vessel rupture, there is very little powder able to escape.