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This data is from the European Hydrogen Incidents and Accidents database HIAD 2.1, European Commission, Joint Research Centre.

Toxic and Flammable Gas Release from Steels Production Plant
The release of a blast furnace gas occurred at a section of pipework, due to the rupture of valve seal. The gas did not ignite and the fire service attended as a precaution. The gas was both flammable and toxic, containing 21% carbon monoxide and 5% hydrogen.The onsite emergency plan was activated and the workers sheltered in toxic gas refuges. A concentration of 400 ppm carbon monoxide was measured 200 metres away at the power station, but there were no off-site effects. The blast furnace was shutdown, with all the gas being discharged through the flare stack.The investigation identified the sequence of initiating events as follows (see eMARS event description among the sources):The plate valve affected by the release was used for isolation of gas main line during shutdowns. 1.During operation it is kept open, but closed due to an electrical short-circuit which caused the hydraulic closure of the valve. 2.The valve did not fully close and the seal was blown off by the gas flow, 3.The leak occurred through the annulus of the valve. 4.The blast furnace shut down but the residual pressure in the gas holder led further release, some gas flared off, but approximately 750,000 cubic metres of gas were lost via the valve.
Event Date
August 9, 1999
Record Quality Indicator
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
The immediate cause of the release was the wrong automatic closure of a main valve, with consequent rupture of its seal. The root cause may be the lack of assessment of management system in place to prevent and mitigate potential major accidents (at the time of the accident, the plant had just been classified as COMAH top-tier).
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
blast furnace, CO-H2 mixture, steel plant
Storage/Process Medium
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
The unit affected was the blast furnace system. The blast furnace gas formed during furnace operation is directed from the furnace through the demister into the clean gas system. The failed valve was the demister valve. It is a plate valve of 3.5m in diameter and is a normally open valve. It is used to isolate the downstream part of the clean gas system when the furnace is off-blast, it is not an emergency shut-off valve.
Lessons Learned
Lessons Learned
The accidental closure of a valve during operation due to a short-circuit shows that the fault event tree analysis had not been performed with the required accuracy. In particularly, the unit's isolation procedures need to be reviewed to ensure sufficient monitoring as part of safe system.The was only recently classified as COMAH top-tier site and little previous work has been done to evaluate the management system in place to prevent and mitigate potential major accidents.As a consequence of the accidents and the related investigation conclusion, the HSE management model was applied and a management system audit proposed.
Event Nature
Emergency Action
The onsite emergency plan was activated and the workers sheltered in toxic gas refuges.The blast furnace was shutdown, with all the gas being discharged through the flare stack.An attempt was made to close the main entrance to the site however other entrances were not closed and operators from the afternoon shift were able to come onto site and relieve their opposite numbers from the morning shift during the incident.
Emergency Evaluation
Emergency systems and measures were adequate.
Release Type
Release Amount (kg)
207000.00
Hole Shape
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References

A. WHITFIELD, COMAH AND THE ENVIRONMENT Lessons Learned from Major Accidents 1999–2000, Trans IChemE, Vol 80, Part B, January 2002

Description of the event in European database eMARS
https://emars.jrc.ec.europa.eu/en/emars/accident/view/3a130415-58e7-8c2…
(accessed September 2020)

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