Pollution
Humain
Environnement
Economique

Whilst on patrol one Saturday, a watchman detected a suspicious odour coming from an alfalfa pellet silo at a sugar refinery. He passed on the information at the end of his shift. Smoke was detected at around 1:00 a.m. the following morning. The silo, which contained 5500 t of pellets, was ventilated by making openings at the top of the building. Firefighters began removing pellets at 8:30 a.m. Due to the intensity of the smoke and the wind that was blowing it towards the building’s access door, the firefighters temporarily halted their efforts at 11:30 a.m. That night, they removed 2 m² of tiles from the silo’s roof to make a hole to water the hot spot. By the morning of the day after the start of the fire, the number of firefighters was reduced. At 8:00 p.m., the carbon monoxide level was normal and the temperature of the seat of the fire dropped below 40 °C. Most of the building was emptied. The firefighters left at 11:00 p.m.

At 8:30 p.m., during a patrol on the fourth day after the accident, glowing particles were seen to be falling from the metal frame. The firefighters returned and protected the remaining pile of pellets with a tarpaulin. On the fifth day, the probes were put back into the remaining pile. The outside piles were covered until the sixth day.

Multiple factors were identified as causing the fire:

  • This was the first time that alfalfa pellets were stored on the site without the operating personnel being trained in the specific risks;
  • The ambient temperatures were high (it was summer) and the alert thresholds of the temperature probes were not suited to enable personnel to distinguish between high summer temperatures and high temperatures from self-heating. All values were shown in red;
  • No silo ventilation;
  • The technicians were not sufficiently trained in using the new silo temperature monitoring software installed in 2017. In particular and although set out in the procedure, temperature curves were not formally tracked.

The operator subsequently implemented the following corrective actions:

  • updated the building and access maps in the emergency procedure;
  • updated the pellet monitoring procedure and conducted staff awareness training;
  • connected the silo temperature monitoring alarms to the supervision system;
  • trained his operating staff in using the temperature monitoring software and repaired the probes;
  • revised, with the grain-loading contractor, the procedure for lowering probes as grain is transferred;
  • looked into the possibility of installing a ventilation system on the pellet silo.