Explosion in a Chlorine Production Plant
A lightning strike caused a voltage drop on the power supply of a chlorine-alkali plant using the mercury process.The emergency electrical system was activated, though restoring the external supply voltage in less than 200 ms rendered the entire system inconsistent; some units were operating normally, but all units connected to the emergency devices (including the mercury pump) remained idle. An explosive mix of 500 kg of chlorine and an unknown amount of hydrogen accumulated inside the low-pressure chlorine treatment circuit. When the mix exploded, it injured two employees and destroyed the whole circuit (damage: 237 000 euros).
Event Date
July 23, 2009
Record Quality Indicator
Region / Country
Event Initiating System
Classification of the Physical Effects
Nature of the Consequences
Causes
Cause Comments
The immediate cause was the loss of power due to lightning. The power recovery system was not considering that several components would have not properly reacted to micro-losses.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
mercury pump
Storage/Process Medium
Location Type
Location description
Industrial Area
Operational Condition
Pre-event Summary
because of a lightning, a power loss had occurred, followed by the activation of the emergency electrical system.
Lessons Learned
Lessons Learned
LESSON LEARNED:Accordig to ARIA, tis accident demonstrated the need to improve the simple binary approach (i.e. on/off) in term of power availability. It is necessary to incorporate short-duration voltage drops (electrical disturbances) into the safety reports. An installation's emergency power supply must be designed by integrating a SIL 2 safety integrity level (according to the Standards IEC 61508 / 61511). CORRECTIVE ACTION:The site operator extended personnel training modules to include the facility's operating details, in a step to better cope with unidentified defects.
Event Nature
Emergency Action
Not reported, probably none.
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
ARIA event
https://www.aria.developpement-durable.gouv.fr/accident/40197/
(accessed July 2023)
ARIA full report
https://www.aria.developpement-durable.gouv.fr/accident/40197/
(accessed July 2023)