Release from a CGH2 trailer

A pressure relief device (frangible burst disc) on one of a 26 tubes on a tube trailers failed prematurely and released hydrogen while filling a hydrogen storage tank at a government facility.
The first responders shut off the supply of hydrogen gas from the tube trailer to the common supply manifold by closing the isolation valve on each of the 26 tubes.

The probable pressure value at the moment of the disc opening was 2100 psi (145 bar), while the over-pressure-protection burst disks on each of the tube trailer's 26 tubes had a rated burst pressure of 4000 psi (275 bar).

The INITIATING CAUSE was the premature opening of e burst disc.

The probable ROOT CAUSE of this event was that the burst disc was degraded by the synergic events of exposure to hydrogen and stress associated with the working pressure involved. A contributing factor in this incident was the burst disc Inconel #600 material that has a high hardness/tensile strength, making it more susceptible to stress corrosion cracking (SCC). It should also be noted that the leak detection step prior to starting the hydrogen fill process is useful for finding leaks in threaded connections, but it could not have detected or predicted the premature failure of the burst disc.

burst disc

Post-event analysis of the incident included removal of the tube trailer's affected over-pressure-protection frangible disc. Inspection of the disc determined that it had ruptured and the disc opening was separated from the rupture disc holder. No visible indication or presence of corrosion or contamination was found. Subsequent testing of other pressure relief devices also showed disc rupture at lower-than-expected pressures.

The hydrogen leak was safely contained and mitigated by the tube trailer vendor`s incident response team. On arrival, the response team first noted a decrease in pressure from the shipped pressure of 2100 to 1700 psi (145 to 117 bar) at the tube trailer`s common supply manifold. The hydrogen leak was located to a single tube on the tube trailer coming from a burst disc (over-pressure-protection rupture disc). The hydrogen gas from the tube trailer to the common supply manifold was shut off by closing the isolation valve on each of the 26 tubes. The leaking tube was vented to atmosphere by attaching a 10-ft (3-meter) vertically oriented pipe downstream and opening the leaking tube`s isolation valve. After the leaking tube was completely vented, the leaking tube`s isolation valve was closed and the vent pipe was removed. The final step was to disconnect the tube trailer from the facility`s regulator distribution control and move it outside of the facility`s designated hydrogen storage area.

No property damage or injuries occurred from this incident.