Release of Chemical Substances (including Hydrogen) from a Chemicals Production Plant
The event was initiated by the burst of a rupture disc on a reactor during a hydrogenation process. The hydrogenation reaction occurs under pressure in a tank containing 3,000 l of a mixture of ethanol (a flammable and toxic solvent), red hair dye, a catalyst (palladium on carbon) and hydrogen. As a result of the disk rupture and the following tank decompression, decompression, part of the tank content was expelled and landed on the roof of the building.The emergency action consisted in stopping the supply of hydrogen and to purge the tank with nitrogen. The internal investigation showed that the discs maximum operating pressure was 2.83 bar, rather than assumed 3.7 bar. The hydrogenation process operates at pressures up to 2.9 bar. Following a reference change, the rupture disc supplier did not validate the characteristics of the new model sold to the operator, who had not been informed of the reference change. A possible additional contribution to the event could have been the 10-year inspection of the seal and the graphite performed a month earlier, which may have weakened the disc.
Event Date
September 22, 2015
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 burst of the rupture disk under nominal working pressure condition.The root cause was the delivery by the contractor of a disk with different characteristics, without informing the plant operator.A contributing cause could be the absence of an independent control of components by the operator.
Facility Information
Application Type
Application
Specific Application Supply Chain Stage
Components Involved
hydrogenation reactor, rupture disk
Storage/Process Medium
Actual Pressure
2
Design Pressure
2
Location Type
Location description
Industrial Area
Pre-event Summary
A maintenance intervention performed one month before the event may have damaged or weakened the disk.
Lessons Learned
Lessons Learned
According to the ARIA report (see references), following the accident, the operator reviewed the reactor qualification documents, including the max. operative pressure of the rupture discs. All the discs in place on other reactors were checked and the discs below specifications were replaced. The maintenance personnel were made aware of the importance of the proper assembly of rupture discs on the reactors.It is however unclear how these reported measures can guarantee to avoid in the future the same accidents, in absence of a regular internal procedure aiming at checking subcontractors deliveries.
Event Nature
Emergency Action
The emergency state of the plant is called few minutes from the burst. The system is made safe by stopping the hydrogen supply and filling the reactor with nitrogen. The valves of the rain water network are closed to confine the water contaminated by the liquids released. This waste is burned in the evaporator of the plant. The emergency is called off half hour after the event.
Release Type
Release Substance
Release Pressure (bar)
2.90
Detonation
No
Deflagration
No
High Pressure Explosion
No
High Voltage Explosion
No
Source Category
References
References
Event description in the French database ARIA
https://www.aria.developpement-durable.gouv.fr/accident/47182/
(accessed September 2020)