A flameless combustion occurred around 9:00 am within a silo devoted to storing methionine from an animal feed plant, at which time maintenance work was being performed by a subcontractor on the “lid” of this cell. The welding of a pipe onto the inspection cover had begun 10 min prior when the subcontractor’s employees noticed the emission of irritating smoke. They immediately closed the cover in order to avoid adding oxygen and then sounded the alarm. Onsite at 9:15, firefighters searched for burning points, using a thermal imaging camera, within the silo and this led to a negative outcome. The storage temperature, which had not exceeded 20°C according to the site operator, reached 13°C around noon and the 13 tons of methionine were then transferred into big bags. The emergency response team left the site around 1:00 pm.

The accident was caused by the spraying of incandescent material during pipe welding. The inspection for classified facilities conducted a same-day investigation and reported insufficient guidelines regarding the burning permit (the risk of spattering material was underscored, yet protective measures were left to the choice of work crews), along with a lack of awareness by subcontractor personnel of the risks incurred when working with hot spots. In contrast, the inspector’s report did acknowledge that the installations were being cleaned at regular intervals and recorded in a dedicated logbook and that ATEX zones were being delimited. As a follow-up to this work, the site operator anticipates developing a set of specific instructions for the welding and draining tasks on the cells targeted by this process.