Hydrogen Explosion at a Turbine-Generator Unit of a Power Plant
Maintenance works were ongoing after an outage at a turbine and generator unit of the plant. Fifteen maintenance mechanics were working at that time on the unit. An access cover was removed causing the release of hydrogen and resulting in multiple explosions and fires. The explosion was heard 35 miles away. The blast tore a huge section from a building holding the six coal-fired generators of the plant and caused two fatalities and several injuries. The hydrogen was used as cooler of the unit. It should have been purged before opening the system.
Event Date
April 9, 1999
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
Immediate cause was the accidental release of hydrogen used for the cooling of the turbine and generator unit. A possible root cause would be the failing of following the safe procedure, or the inadequacy of the procedures.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
turbine and generator unit, hydrogen-based cooling system, coal-fired generator
Storage/Process Medium
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
Maintenance works were ongoing after an outage at a turbine and generator unit of the plant.
Currency
Lessons Learned
Lessons Learned
The sources do not report corrective actions and/recommendations aiming at preventing the accident. Before starting working on a pressurised hydrogen system, it must be de-pressurised and /or put under inert atmosphere. The fact that workers were performing maintenance on a system containing pressurised oxygen, suggests the needs to have an adequate safe procedures for maintenance, and to ensure that the maintenance team (in particular if it belong to a subcontracting company) is informed and adopt the procedure.
Event Nature
Emergency Action
Unknown
Release Type
Release Substance
Hydrogen Release Concentration (%)
100.00
Ignition Source
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Flame Length (m)
1.00
Source Category
References
References
Event description in the French database ARIA,
https://www.aria.developpement-durable.gouv.fr/accident/15339/
(accessed December 2020)
US Occupational Safety and Health Administration OHSA Report ID: 0420600
https://www.osha.gov/pls/imis/establishment.inspection_detail?id=109212…
(accessed October 2020)