Event
- Event ID
- 1145
- Quality
- Description
A driver found a small audible leak coming from the rear of the trailer compartment, while conducting in-trip visual walk-around inspection at a roadside. The driver set up perimeter around trailer using triangles and safety cones, contacted the trailer company to notify the leak and contacted local police department to inform of the situation. The company experts inspected found a leak coming from the neck valve threads one of the ten tubes. They decided to vent to atmosphere the hydrogen contained in that tube, connecting a portable vent stack. After having disabled the leaking valve, the trailer returned to facility for inspection and repair.
- Event Initiating system
- Classification of the physical effects
- Unignited Hydrogen Release
- Nature of the consequences
- leak no ignition
- Macro-region
- North America
- Country
- United States
- Date
- Component involved
- joint/connection (threaded)
- Failure mode
- rupture, no ignition
- Initiating cause
- material degradation (generic)
- Root CAUSE analysis
The INITIATING CAUSE was probably the loosening of a threaded connection of a valve. A possible technical explanation could be road vibrations, but other material ageing/degradation reasons cannot be excluded.
The ROOT CAUSE is not provided, however, an effective design should be able to take into account road vibrations on a road vehicle.
- Root causes
- Date entry in HIAD
- 25/10/2024
Facility
- Application
- Hydrogen transport and distribution
- Sub-application
- CGH2 tube trailer
- Hydrogen supply chain stage
- All components affected
Threaded Connection
- Process temperature range [C]
- ambient temperature (-50°C to +50°C)
- Process pressure range [MPa]
- medium to high pressure (10 to 50 MPa)
- Location type
- Open
- Location
- highway or similar
- Operational condition
- Description of the facility/unit/process/substances
DESCRIPTION OF THE UNIT
The trailer consisted of 10 tubes. The PHMSA source provides a value of released hydrogen of 11000 GCF (28 kg), which corresponds to the content of one tube. This results slightly lower than the nominal capacity of these tube, declared as 12500 GCF (318 kg)
Emergency & Consequences
- Number of fatalities
- 0
- Number of injured persons
- 0
- Currency
- US$
- Property loss (onsite)
- 0
- Emergency action
The driver set up perimeter around trailer using triangles and safety cones, and notified local police and the company.
The company intervention team decided to depressurise the leaking tube by releasing its content to the atmosphere.
Lesson Learnt
- Lesson Learnt
The mitigating measures worked well: (i) the regular inspection by drivers along the route, and (ii) the emergency handling by depressurising the leaking tube and releasing its content to the atmosphere.
The loosening of threaded connection due to road vibration is a common glitch. It is however unclear, in this event and similar event, how this could be avoided. Is the root cause related shortcoming when installing / maintaining the connections, or to unexpected road conditions during travel?
In-depth data
- Release type
- gas
- Involved substances (% vol)
- H2 100%
- Released amount (kg)
- 28
- Release temperature [°C]
- 25
- Release pressure [MPa]
- 17.4
- Probable IGNITION SOURCE
References
- Sources categories
- PHMSA
- Reference & weblink
Incident I-2015090569 of the US Pipeline and Hazardous Materials Safety Administration PHMSA:
https://portal.phmsa.dot.gov/analytics/saw.dll?Portalpages&PortalPath=%…
(accessed September 2024)
