Event
- Event ID
- 594
- Quality
- Description
The explosion occurred at a ramjet engine of an aerospace testing centre. In order to carry out an airtight test on the engine, a pressure gauge was connected, the bolts on the hydrogen supply pipe flange removed and a closing plate inserted.
After the successful tightness test, the closing plate was removed and the connection between the hydrogen supply and the engine was restored. A preliminary ramjet engine combustion test was started with air, oxygen, and hydrogen.
However, the bolts had been wrongly tightened with an O-ring protruding from the groove on the flange and the pressure gauge main valve had not been not properly closed. This caused a hydrogen gas leak followed by an explosion occurred when the combustion test was ignited.- Event Initiating system
- Classification of the physical effects
- Hydrogen Release and Ignition
- Nature of the consequences
- Macro-region
- Asia
- Country
- Japan
- Date
- Component involved
- flange (gasket)
- Failure mode
- leak & ignition
- Initiating cause
- wrong installation
- Root CAUSE analysis
The INITIATING CAUSE was a hydrogen leak due to a wrongly mounted flange., combined with a valve left open.
The ROOT CAUSES are combination of errors during the preparation of the test and with a human error and possible lack of clear instructions.- Root causes
- Date entry in HIAD
- 01/01/2025
Facility
- Application
- Non-road vehicles
- Sub-application
- Aerospace
- Hydrogen supply chain stage
- All components affected
aerospace engines testing laboratory
- Location type
- Unknown
- Location
- unknown
- Operational condition
- Pre-event occurrences
Atightness test had been performed before the start of engine test. This required the de-installation and re-installation of hydrogen supply connections.
From WIKIPEDIA: a ramjet is "a form of airbreathing jet engine that requires forward motion of the engine to provide air for combustion. Ramjets work most efficiently at supersonic speeds around Mach 3 "
Emergency & Consequences
- Number of fatalities
- 0
- Number of injured persons
- 0
- Post-event summary
The test facilities were destroyed
In-depth data
- Release type
- Gas mixture
- Involved substances (% vol)
- H2, O2, N2 (jet engines fuel)
- Probable IGNITION SOURCE
- Explosion type
References
- Sources categories
- KHK
- Reference & weblink
High Pressure Gas Accident Cases Database of the KHK (High Pressure Gas Safety Association):
https://www.khk.or.jp/public_information/incident_investigation/hpg_inc…
(accessed May 2025)The first entry in HIAD was coming from RISCAD, which is now closed.
