At 9:20 a.m., the temperature inside a 4000-l reactor used to manufacture an organomagnesium compound at a chemical plant abruptly rose. At 9:30 a.m., the employees in the shop began flooding the reaction medium with water. As a precaution, the internal emergency plan was implemented for several minutes. Upon contact with the water, the medium underwent hydrolysis and started boiling violently. The internal pressure continued to rise, ultimately bursting the reactor’s rupture disc (tared to 0.4 b). The boiling rapidly decreased and then stopped. No consequences were reported.

The operation underway in the reactor was nonconforming and had been under observation since 16 September. That day, a technician confused the 100% technical grade with the 18% solution indicated in the procedure. As a result, he loaded 3.8 kg of initiator instead of 21 kg (18% solution). The technician at the following station continued synthesising the organomagnesium compound without knowing that the amount of initiator loaded was insufficient. As per the procedure, he added the requisite amount of PBDMA (brominated organohalogen compound), which was in fact over-proportioned to the amount of initiator in the mixture. Not seeing the reaction start after the first pouring set at 36 l, he then added 36 l of PBDMA solution as per the procedure but without informing his supervisors. Seeing that the medium was bubbling slightly, he continued to progressively pour the reagent in 10 l fractions up to a total of 500 l. Between each fraction, he waited for the temperature to rise as expected at the start of the reaction.

As the exothermic reaction did not occur, he finally notified the on-call manager. The manager stopped the reagent supply and lowered the reaction medium’s temperature to 0 °C with a slow stirring. This stopped the reaction so that it could subsequently be reprocessed. Nothing happened for the next 72 hours until the medium’s temperature quickly rose and the rupture disc burst.

The cause of the incident was an ambiguously worded instruction that was misinterpreted by the first technician, who was finishing his shift. In the case of the second technician, the process sheet indicated that the reagent could be added in the absence of a reaction, but only after receiving the supervisor’s approval. The operation took place on a Saturday, when the supervisory staff was off for the weekend. The chemical engineer therefore notified the on-call manager belatedly. The lack of communication between the two stations and the technicians’ lack of experience resulted in the creation of a nonconforming mixture. In addition, the reaction started when it was considered to be controlled at 0 °C.

To prevent any such future incidents, the operator resumed tracking which technicians are authorised to perform synthesis operations. It modified the process sheet to clarify the amounts of reagent to be loaded and provide hold points for starting the reaction. This reaction is no longer allowed to be started on weekends. It must be started at the beginning of a shift so that synthesis can be monitored. The operator set up a working group to conduct a detailed review of organomagnesium compound synthesis operations in order to establish standards of manufacturing and reacting to problems applicable at all plants where such reactions are performed (quick response sheets).

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