A single-stage regulator "failed" while flowing hydrogen gas from a standard 200 cu.ft. gas bottle. The regulator had functioned properly prior to the event through several on-off cycles. During the event, a solenoid valve was opened to allow hydrogen to flow, when a rather loud noise was noted and gas began flowing out of the pressure relief valve on the side of the regulator. It was noted that the low-pressure gauge on the regulator was "pegged" at the high side (>200 psi). The valve on the bottle was shut off, and hydrogen flow was immediately stopped. Hydrogen flowing out of the relief valve did not ignite. With the bottle shut off, the regulator was removed and replaced with another regulator of the same type, and activities continued.

The failed view more

A hydrogen leak and subsequent explosion occurred when tie-downs on a hydrogen transport trailer securing hydrogen cylinder packages failed. The tie-down failure caused the hydrogen cylinder packages to fall off the trailer and eject some cylinders onto the roadway (see Figure 1). The cause of the accident is unknown, but it appears to be unrelated to hydrogen (i.e., likely tie-down strap weakness or error in properly securing tie-downs). The cylinders contained compressed hydrogen gas at 200 bar (2900 psi). The accident caused some hydrogen cylinders to leak and the associated cylinder package plumbing systems were breached. A spark or other local heat source (e.g., from a nearby vehicle motor) ignited the leaking hydrogen and caused a deflagration/explosion that damaged a car view more