One hundred tonnes of sunflower meal self-heated in a 232 m³ storage bin of a silo at an animal feed plant. Seeing no meal coming out, the production manager opened the inspection hatch under the hopper and saw smoke coming out of it. He alerted the firefighters at 3:20 p.m. The planetary roller screw and screw conveyor were locked out to isolate the storage bin. Firefighters arrived at 4:00 p.m. and used a hose to cool down the inspection hatch. They detected a 100 °C hot spot. They cut a hole in one of the storage bin’s bottom panels and removed as much sunflower meal as they could to reach the hot spot. At 6:00 p.m., the operator removed the hatch located above the screw conveyor in order to reach the hot spot. The firefighters used a bar to break up and pull out the sunflower meal. They extinguished the meal when it ignited in contact with the outside air. At 7:00 p.m., they did the same via a second hatch located opposite the hot spot. After removing the meal, the firefighters found a rathole (ratholing is a condition where material forms a narrow channel at the centre of a silo, restricting flow) extending 5 m up the silo. Using a hose, they drenched it with 1000 l of water per minute. The meal was progressively taken away by heavy machinery. The firefighters extinguished the hot parts that self-ignited. They finished at 1:00 a.m. A total of 2 t of meal remained at the bottom and no hot spots were detected. Smoke was again reported at 8:00 a.m. The firefighters returned. They finished emptying the silo at 12:30 p.m.
The financial loss was estimated at a total of €41,412, broken down as follows:
- 31 t of destroyed sunflower meal (€15,655);
- cleaning of the inside of the silo (€2946);
- repair of the storage bin and replacement of the panels (€7200);
- mechanical and hydraulic system (€15,611).
The most recent meal deliveries were tested and found to be satisfactory. The hot spot was located near an access hatch that had not been planned in the silo’s design. An improper seal may have caused water to enter the silo and cause the meal to become compacted and self-heat.
