Fire was detected at 10:05 pm in the stainless steel sheet stripping unit of an upper-tier Seveso metallurgical plant. The surface treatment line, composed of 7 unheated polypropylene tanks (5 containing hydrochloric acid, 1 containing hydrofluoric acid, 1 containing nitric acid). The smoke plume was blown by the wind (at 5 to 12 m/s) northwards to an undeveloped zone. The internal emergency plan was activated. In-house fire-fighters were unable to control the blaze and notified municipal first responders at 10:27. The crew called of approx. 100 fire-fighters extinguished the fire at 5 am using 6 hoses (water/foam) at a maximum rate of 5,000 litres/min; residual sources of ignition were snuffed out during the morning hours. A slightly injured employee was treated on-site. Public first responders left the scene at 4 pm.
The extinguishing water could be confined and then channelled to the mill’s treatment plant. The building was destroyed over a 120-m length and an 18-m width (collapse of the metal frame roof) along with 5 of the 7 treatment tanks, which were empty when the fire struck, and the vapour extraction systems on 3 tanks. The asbestos cement roof of a juxtaposed shed and a bridge crane were also damaged. No environmental impact was reported.
This unit had been placed in service during summer 2012 following a €50-million investment. The reconstruction works were to last several months. According to the mill operator, the fire arose subsequent to welding a metal strip (length: 12 m, width: 0.3 m, thickness: 5 mm) on a steel ribbon being continuously unrolled and treated as part of repairs following its tear. Technicians performed this type of repair from inside the previously drained stripping tanks. A smouldering fire under a tape roll lined with a medium-density elastomer (EPDM) had been triggered by ventilation after resetting the tanks’ plastic caps. Both the fire detection (via 14 flame detectors) and the automatic sprinkler extinction of the unit had been deactivated in order to avoid start-up during the works. Subsequent to this accident, the operator planned to implement various technical and organisational measures, including: stainless steel treatment tanks, fluid networks via independent racks, local sprinkler system activation, discontinued extinction independent of fire detection, manager training on the internal emergency plan, regular drill exercises, introduction of an instantaneous feedback protocol in conjunction with outside agencies and the press, and revision of response procedures both on the stripping lines and for hot spot works. The inspection authorities for classified facilities proposed to the local government authority to demand an update of the site’s safety report to the operator. The Prefecture issued 3 press releases within the first few hours after the outbreak.