Pollution
Humain
Environnement
Economique

In a chemical plant, the rupture disc on a reactor burst at 11:35 a.m. during a hydrogenation process under pressure. The tank on which the rupture disc was installed contained 3,000 l of an ethanol mixture (a flammable and toxic solvent), red hair dye, a catalyst (palladium on carbon) and hydrogen. As a result of decompression, part of the reaction medium (411 kg of ethanol and 23 kg of synthetic products) was expelled and landed on the roof of the building, which became stained in red. The alarm was triggered at 11:37 a.m., the employees were confined, and the site was shut down.

The internal emergency plan was activated at 11:41 a.m. The production process was secured: the reactor’s hydrogen supply was stopped, and nitrogen was injected into the system. The stormwater network valve was closed in an effort to contain the polluted water. The operator informed the neighbouring businesses, the municipality and the Classified Facilities Inspection Authorities. The polluted water network was cleaned using a high water-pressure cleaning process. The 70 m³ of effluent generated was treated in the site’s evaporator. Roughly 10 kg of ethanol was released into the atmosphere. The internal emergency plan was lifted at 12 p.m.

The internal investigation showed that the disc’s maximum operating pressure (max. OP) was 2.83 bar, rather than 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 (max. OP) of the new model that it had sold to the operator. Moreover, the operator had not been informed of the reference change. Also, stacked assembly of the seal and the graphite disc during the 10-year inspection a month earlier may have weakened the disc.

The operator is reviewing the reactor qualification documents, including the max. OP of the rupture discs. The max. OP of the discs in place on the other reactors operating under pressure is being checked as well, and discs with a max. OP below specifications are replaced. The maintenance personnel are being made aware of the importance of the proper assembly of rupture discs on the reactors.