A fire broke out around 2 p.m. in the intake filter of a dust collector on a grain storage silo at a Seveso-rated agricultural marketing cooperative. The fire spread through the redler conveyor to the open-air dust waste container, which created a great deal of smoke. The site’s activity was partially suspended, and the electrical power was disconnected. The fire brigade was able to extinguish the outdoor fire at around 4:30 p.m. The emergency services had difficulty dismantling the dust collector’s filters, then emptied out the redler conveyor to ensure that no hot spots were still present. The intervention ended at 11:45 p.m.
The hot spot that caused the accident was due to a mechanical stress caused by the wear of the bearing on the bucket elevator’s drive shaft (at the top of the elevator). The hot spot was fanned by the nearby fan used to draw in the dust into the system. Incandescent particles were drawn into the dust collection system and notably into the bag filter, causing the entire contents to catch fire. The mechanical stress resulting from bearing wear was not enough to cause deflection of the elevator’s belt. The belt’s offset controllers thus did not detect the defect on the drive shaft. This visual inspection conducted before the collection operation proved ineffective as it did not detect the defect on the drive shaft packed in grease. Following this accident and considering the silo’s numerous handling operations, the operator plans to conduct preventive maintenance of these bearings 3 times a year.