In a chemical plant, an exothermic polymerisation reaction took place in a hot room housing five pallets of four 200-kg drums of monomer-acrylate (SR295). An large amount of yellow smoke was released; it consisted of carbon monoxide and carbon dioxide (CO and CO2), according to the product safety data sheet and measurements recorded by the emergency services. The 44 fire-fighters called to the scene deployed five variable-flow water cannons to cool the storage tanks, protect nearby solvent tanks (ethane, heptane, toluene, etc.) and beat down the released fumes.
The situation was brought under control after 4 hours, and the extinction water was confined to the site’s holding tank. No one was injured.
Disruption to the heating system of the heated chamber was responsible for this overheating and initiation of the polymerisation reaction; the high heat release induced by this reaction caused thermal degradation of the substance. Following the accident, the Classified Facilities Inspectorate found that the measures adopted to prevent a change in heating chamber temperature were inadequate due to:
- a lack of procedures governing the control of the temperature by the station manager;
- no indication of the frequency of these controls or actions to be taken in the case of a deviation in temperature.
While the set temperature of the room was 80°C, temperatures of 95°C and 98°C were recorded the day before the accident but were not relayed to the operator. Moreover, Safety Data Sheet SR295 prepared by the operator indicated a maximum storage temperature of 60°C.
To reduce the likelihood of such an accident recurring, the operator agreed to implement various corrective actions, namely:
- define procedures to control room temperature (frequency, warning temperature for each product stored) and actions to handle deviations;
- set up alarms on the temperature measuring devices for each room;
- study the relocation of rooms close to the solvent storage.