Event
- Event ID
- 323
- Quality
- Description
The event occurred during a pressure testing of a LH2 pump discharge system. A weld joint failed at an internally tied bellows. The weld failed at 1100 psi (ca. 76 bar) while the test pressure planned was 2000 psi (ca. 138 bar). The rupture of the line caused the release of large amounts of liquid hydrogen.
The explosion was heard at 10 000 ft. (ca. 3 km) distance, but there was little evidence of scorching. The piping (part of a triple gimbal) had been hydrostatically tested to 2400 psia (ca. 165 bar) and with helium gas to 2000 psia several days before the failure. The explosion has been evaluated equivalent to 5 lb TNT (ca. 2.3 kg), based on damage to equipment and buildings.- 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
- piping (weld)
- Failure mode
- rupture & ignition
- Initiating cause
- wrong material choice
- Root CAUSE analysis
The INITIATING CAUSE was the weld failure at cryogenic temperature.
The most likely ROOT CAUSES were considered (i) the improper design of the gimbal and (ii) the material selection . The design shortcoming resulted in serious weaknesses. The material used (17-4PH) undergoes ductile to brittle transition near -100° F. The steel was also notch sensitive and could not withstand the non-axial loading at cryogenic temperatures.
The ignition source was considered to be due to the energy from the tearing and moving of metal.- Root causes
- Date entry in HIAD
- 30/10/2025
Facility
- Application
- Non-road vehicles
- Sub-application
- Aerospace
- Hydrogen supply chain stage
- All components affected
weld joint, LH2 pump
- Process temperature range [C]
- cryogenic temperature (below -50°C)
- Location type
- Unknown
- Location
- countryside or desert
- Operational condition
- Pre-event occurrences
The piping had been hydrostatically tested to 2400 psia (ca. 165 bar) and with helium gas to 2000 psia several days before the failure.
Emergency & Consequences
- Number of fatalities
- 0
- Number of injured persons
- 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 34 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
