Event
- Event ID
- 1117
- Quality
- Description
A LH2 trailer was traveling to delivery hydrogen to a customer, while the drivers noticed an increase in trailer pressure. To avoid the possibility of having the safety vent open while on the road, they pulled into a truck stop. There they performed a controlled, manual venting of the trailer in a remote section of the truck stop. Drivers then continued on to destination without further incident.
- 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
- LH2 tank (road tanker)
- Failure mode
- rupture, no ignition
- Initiating cause
- over-pressurisation (wrong operation)
- Root CAUSE analysis
The INITIAL CAUSE was over-pressurisation of the LH2 tank, which caused an intervention of the drivers to reduce pressure.
BY using as proxy several similar events, ROOT CAUSE could be tentatively attributed to the failure to 'stabilise' the pressure of the tanker after delivery and before leaving customer's site. This is a procedure aiming at avoiding over-pressurisation by cold gaseous hydrogen during the return travel.- Root causes
- Date entry in HIAD
- 09/09/2024
Facility
- Application
- Hydrogen transport and distribution
- Sub-application
- LH2 tanker
- Hydrogen supply chain stage
- All components affected
unknown
- Process temperature range [C]
- cryogenic temperature (below -50°C)
- Process pressure range [MPa]
- low to medium pressure (below 2 MPa)
- Location type
- Open
- Location
- highway or similar
- Operational condition
- Pre-event occurrences
The trailer was full loaded, on the road towards a customer
Emergency & Consequences
- Number of fatalities
- 0
- Number of injured persons
- 0
- Currency
- US$
- Property loss (onsite)
- 122
- Post-event summary
A negligible amount of hydrogen was released.
- Emergency action
The emergency was quickly ended by the intervention of the drivers, who performed a manual pressure release operation.
Lesson Learnt
- Lesson Learnt
From this and several other cases reported in PHMSA database, it appears that a corrective measure often adopted in case of a slight increase of LH2 internal tank pressure is to perform a manual, controlled release of the hydrogen vapour to reduce pressure. Although not stated in the reports, the value of the pressure at which the drivers take action is less than the pressure value at which the automatic safety pressure control system activate.
Often the cause of the pressure increase is not stated, in other cases it is assumed having been a partial loss of the thermal insulation capacity (loss of vacuum in eh annular space between the internal and external shells of the cryogenic tank.
Anyhow, the corrective measure appears to be successful to continue the delivery to the customer or to return to the base with an empty tanks, despite the fact that the cause of the pressure increase is not eliminated, and it is expected that it will occur again.
In-depth data
- Release type
- gas
- Involved substances (% vol)
- H2 100%
- Released amount (kg)
- 5.3633610900833
- Probable IGNITION SOURCE
References
- Sources categories
- PHMSA
- Reference & weblink
Incident I-2002090431 of the US Pipeline and Hazardous Materials Safety Administration PHMSA:
https://portal.phmsa.dot.gov/analytics/saw.dll?Portalpages&PortalPath=%…
(accessed September 2024)
