Event
- Event ID
- 433
- Quality
- Description
After cooldown of a LH2 system, the operator noticed cold gas issuing from a small hole in a flexible section of the vent line. Subsequent examination revealed that a deflagration had taken place in the vent line and there was a small hole in the flexible section. The vent cap showed signs of fire and was stuck in the open position.
- Event Initiating system
- Classification of the physical effects
- Hydrogen Release and Ignition
- Nature of the consequences
- Macro-region
- North America
- Country
- United States
- Date
- -
- Component involved
- venting system (line)
- Failure mode
- internal explosion
- Initiating cause
- inadequate or no purge
- Root CAUSE analysis
The INITIATING CAUSE was the formation of hydrogen-air mixture in the vent.
The mixture may have formed when the line warmed and sucked air back into the line around the seal of the vent cap or the cap may have stuck open and air diffused into the line. No source of ignition was determined. The ROOT CAUSE is unknown.- Root causes
- Unknown
- Date entry in HIAD
- 01/11/2025
Facility
- Application
- Non-road vehicles
- Sub-application
- Aerospace
- Hydrogen supply chain stage
- All components affected
vent
- Process temperature range [C]
- cryogenic temperature (below -50°C)
- Location type
- Unknown
- Location
- industrial area
- Operational condition
Emergency & Consequences
- Number of fatalities
- 0
- Number of injured persons
- 0
- Property loss (onsite)
- 0
In-depth data
- Release type
- liquid
- Involved substances (% vol)
- H2 100%
- Probable IGNITION SOURCE
- Explosion type
References
- Sources categories
- ORDIN
- Reference & weblink
Mishap no 74 in
P. L. Ordin, Review of hydrogen accidents and incidents in NASA operations, 1974, NASA TM X-71565
https://ntrs.nasa.gov/citations/19740020344Hankinson and Lowesmith, Qualitative Risk Assessment of Hydrogen Liquefaction, Storage and Transportation, FCH JU project IDEALHY, Deliverable 3.10 (2013)
confidential
(accessed October 2025)Lowesmith et al., Safety issues of the liquefaction, storage and transportation of liquid hydrogen: An analysis of incidents and HAZIDS, Int. J. Hydrogen energy (2014) https://doi.org/10.1016/j.ijhydene.2014.08.002
