Hydrogen Release from a Public Transport Bus
The accident occurred at a production, distribution and storage station for hydrogen city busses. After filling the hydrogen cylinders of a bus, the hydrogen detection system of the bus triggered an alarm. The site technician pushed the emergency button and the station was put in safety mode. The technician in charge of filling disconnected the hydrogen hose that connects the station to the bus. The maintenance manager of the bus manufacturer was alerted and arrived 20 minutes later and evacuated the personnel. They closed the valves of the on-board storage system. and removed the bus top bonnet to allow the hydrogen to disperse in the atmosphere as rapidly and effectively as possible. The emergency services (fire brigades) were called. The station was shut down for 24 hours. The bus was taken off the road while the cylinder manufacturer carried out an investigation.Approximately 8 kg of hydrogen, i.e. one cylinder, was released into the atmosphere.[ARIA event 57930]
Event Date
September 6, 2021
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
The initial cause of the release was a partially misplaced O-ring of the Pressure Release Device of the tanks. It remained undetected because the leak was extremely small. The root cause of this misplacement or erroneous mounting lies somewhere along the supply chain. Piping and connections are usually delivered by Tier 1 suppliers, the on-board storage system probably by Tier 2 suppliers, or assembled by the bus integrator. The actions taken after the alarm went off revealed deficiencies in the handling of emergencies.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
city bus, on-board hydrogen storage, hydrogen detection
Storage/Process Medium
Storage/Process Quantity
38
Storage/Process Units
Location Type
Location description
Inhabited Area
Operational Condition
Pre-event Summary
The bus had terminated the refueling.
Currency
Lessons Learned
Lessons Learned
The series of events occurred during he handling of the emergency revealed some deficiencies: emergency exercises at the production/storage/distribution station were not carried out. The procedures were written and communicated but were never implemented.CORRECTIVE ACTIONS(1) The leaking component has been sent to the producer for further investigation.(2) The technicians will be equipped with portable sensors with a lower detection limits, to be able to detect very small release flows and concentrations.(3) The operator plans to carry out emergency exercises with the different parties present on site. (4) They also prescribe a full leakage test of the hydrogen lines each time an alarm is triggered, as a requirement for the vehicle to be put back into operation.
Event Nature
Emergency Action
Unknown
Emergency Evaluation
The series of events occurred during he handling of the emergency revealed clear deficiencies: the station operator did not executed the first action of shutting down the station by activating the emergency stop. Emergency exercises at the production/storage/distribution station were not carried out. The procedures were written and communicated but were never implemented.
Release Type
Release Substance
Hydrogen Release Concentration (%)
100.00
Release Amount (kg)
8.00
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References