Release from a Hydrogen Storage
Malfunctioning of the non-return valve of the hydrogen compressor has caused the pressure between the hydrogen bottle and the compressor to rise to the maximum allowed pressure of 275 barg. As a consequence, as foreseen by the safety system, the rupture disk of the safety valve broke and the hydrogen content of the gas bottle and the pipe section involved has been released on the top of the building.The flame seen for some instants by a guard could have been caused by the sequential occurrence of the following events:- Expansion of hydrogen at the end of the exhaust pipe,- Consequent mixing of hydrogen and air up to a near-stoichiometry and increase of gas temperature- Mixture ignition due to sparks from static electricity potential generated by gas molecules friction against suspended dust particles.
Event Date
May 4, 2006
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
- non return valve of the hydrogen compressor- hydrogen gas bottle and pipe section- exhaust pipe- compressor- rupture disk of the safety valve
Storage/Process Medium
Actual Pressure
275
Location Type
Location description
Unknown
Operational Condition
Number of Fatalities
1
Lessons Learned
Lessons Learned
CORRECTIVE MEASURES:1) Dismantling, cleaning and testing of the non-return valve. Following positive testing, the system has been restarted and pressurized without any further faulty operation, thus restoring its normal safety function.2) Extension of the hydrogen discharge pipe from the roof of the building to the roof of the next building (realized in August 06). In this way and temporary hydrogen ignition can only take place above approximately 6 meters from ground, farther away from personnel than the 2.5 meters in the previous situation.3) The compressor has been sent for preventive maintenance and review to the producer, aiming at reducing the frequency of malfunctioning of components (September 06).4) An additional measure has been agreed but it is not yet implemented:Organise and document regular periodic maintenance of the non-return valve. It will be inserted in the next revision of the design and safety report (2007).
Event Nature
Emergency Action
Unknown
Release Type
Release Substance
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
The company Occupational Incident Report is confidential