Case No.3
A reaction vessel burst due to a sudden increase in its internal
pressure as a result of abnormal reactions during the process producing
intermediate pharmaceutical products
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[Circumstances of Incident]
The accident occurred in a plant that manufactures intermediate
pharmaceutical products. The production train can be divided into
reaction, maturing, analysis and degasing operations. The accident
occurred during the degasing operation which byproduct gases are removed
from the 6-kl reaction vessel.
On the day
of the accident, two workers in the production section were carrying out
the second day degasing operations under the supervision of the production
manager.
As not all of coolant (ethylene
green in a water solution) had been removed from the vessel jacket on the
previous day, two workers had been working since the morning to try to
remove the coolant by washing the vessel with steam.
Temperatures inside the vessel were elevated partly as a result
of the washing operations, and additional mixing operations caused
abnormal chemical reactions within the vessel, leading to the generation
of heavy foam on the liquid surface at about five o'clock in the
afternoon.
As the manager was absent from
the operational site at the time, the two workers tried to reduce the
internal pressure by opening the pressure-reducing valves at about 5:35,
and then evacuated the site in anticipating imminent danger.
The vessel burst, soon with the cover
plate with clamp coming off. Scattered chemicals injured five employees,
including one fatality.
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[Causes]
A major
cause of this accident can be attributed to the plant managers who did not
anticipate the occurrence of abnormal chemical reactions in the process of
producing benzyl chloroformate. The following conditions can also be
pointed out in relation to this.
(1) The
vessel's internal pressure rapidly increased due to an abnormal reaction,
thus exceeding the vessel's capability to withstand internal pressures.
The vessel was not equipped with safety devices, such as safety valves or
burst plugs, to release internal pressure to the outside before reaching
the bursting point. (2) Appropriate operational
manuals were not prepared regarding countermeasures to deal with abnormal
reactions. Namely, workers engaged in the manufacturing process cannot
take the necessary measures to respond to abnormal conditions as they are
not properly educated or trained. (3) Indirect
causes may include inadequate organizational measures, as shown by the
lack of detailed safety and health education for related workers, and an
undefined command and responsibility structure to ensure safety in
production facilities.
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[Type of business]
Pharmaceuticals manufacturing [Type of
accident]Bursting [Number of victims] Four injured and one
fatality |