Release and Ignition from a CGH2 tube trailer due to a collision

A tractor - semitrailer with horizontally mounted tubes filled with compressed hydrogen struck a northbound pickup truck that had veered in front of it.

The tractor-semitrailer then lost control and overturned while continuing along the highway. It went off the road to the east and travelled 300 or more feet before it stopped (ca. 100 m). Because the valves, piping, and fittings at the rear of the semitrailer were not adequately protected and shielded from the impact caused by the rollover of the semitrailer, 8 of the 10 shutoff valves were sheared off, which resulted in the release and ignition of the hydrogen. One of the tubes separated from the trailer and came to rest at approximately 20 meters distance. It was This the tube which absorbed the initial impact with the roadway or terrain, resulting in the fracture of its front end and its ejection.

In the meantime, the pickup truck had also run off the road. The pickup truck's fuel line ruptured, resulting in the truck being destroyed by fire.

The INITIATING CAUSE was the collision of the hydrogen trailer with another vehicles.
ROOT CAUSE can be attributed generically to a human error (wrong manoeuvre). I-2003100615was a sickness condition of the driver which would have disqualified him as truck driver.
Another ROOT CAUSE or CONTRIUTING CAUSE to the severity of the accident was the inadequacy of the standards/regulations and safety design aiming at protecting and shielding cylinders, valves, piping, and fittings and at securing cylinders on the semitrailer.

trailer with 10 horizontally mounted hydrogen cylinders

DESCRIPTION OF THE TRAILER LOAD
The load cosnsited of 10 metal cylinders, with a nominal working pressure of 2,500 psig (ca. 170 bar) and a volume of 87 cubic feet (ca. 2.5 m^3). The total trailer capacity was 141400 scf (340 kg).

One driver was killed, the other only injured. The cause of the fatality of the injuries were not hydrogen-related, but caused by the rad crash.
Residents of five homes in the vicinity of the accident were asked to evacuate, and the highway was closed for more than 12 hours.
Damage, clean-up, and lost revenues were estimated at $155,000.

Nearly all shutoff valves, piping, and fittings for the 10 cylinders were destroyed by the impact with the roadway and/or terrain. Eight of the 10 shutoff valves were sheared off, resulting in the release and ignition of the hydrogen. The master valve was also destroyed by impact damage. The metal cabinet enclosing the valves, piping, and fittings was also heavily damaged during the accident and rollover.

SPECIFCIC LESSON LEARNT
(1) The national hazardous materials regulations do not provide sufficient and clear requirements for protecting cylinders and valves, piping, and fittings of cylinders that are horizontally mounted on semitrailers.
(2) Because horizontally mounted cylinders on semitrailers typically extend beyond the envelope of the bulkheads, the cylinders were exposed and vulnerable to initial impact with the roadway or terrain during rollover accidents and are at increased risk of damage, failure, and ejection.
(3) It is possible that the lack of information could have increased the risk to emergency response personnel.

RECOMMENDATIONS based on GENERAL LESSON LEARNT
As a result of its investigation, the US National Transportation Safety Board made the following safety recommendations to the Research and Special Programs Administration:

1. Modify the Code of Federal Regulations to clearly require that valves, piping, and fittings for cylinders that are horizontally mounted and used to transport hazardous materials are protected from multi-directional forces that are likely to occur during accidents, including rollovers.

2. Require that cylinders that transport hazardous materials and are horizontally mounted on a semitrailer be protected from impact with the roadway or terrain to reduce the likelihood of their being fractured and ejected during a rollover accident.

3. Revise the information about hydrogen in the North American Emergency Response Guidebook so that it specifically identifies the unique chemical and flammability properties of hydrogen.