Pollution
Humain
Environnement
Economique

At 7:15 p.m., a series of sugar dust explosions resulted in 14 worker fatalities. The sugar manufacturing facility housed a refinery that converts raw cane sugar into granulated sugar. A system of screw and belt conveyors, and bucket elevators transported granulated sugar from the refinery to three 32 m tall sugar storage silos. It was then transported through conveyors and bucket elevators to specialty sugar processing areas and granulated sugar packaging machines. Sugar products were packaged in four-story packing buildings that surrounded the silos, or loaded into railcars and tanker trucks in the bulk sugar loading area.

The Chemical Safety and Hazard Investigation Board (U.S. CSB) determined that the first dust explosion initiated in the enclosed steel belt conveyor located below the sugar silos. The recently installed steel cover panels on the belt conveyor allowed explosive concentrations of sugar dust to accumulate inside the enclosure.

An overheated bearing in the steel belt conveyor most likely ignited sugar dust, causing a violent explosion. The explosion lofted sugar dust that had accumulated on the floors and elevated horizontal surfaces, propagating more dust explosions through the buildings. Secondary dust explosions occurred throughout the packing buildings, parts of the refinery, and the bulk sugar loading buildings. The pressure waves from the explosions heaved thick concrete floors and collapsed brick walls, blocking stairwell and other exit routes. The resulting fires destroyed the packing buildings, silos, palletizer building and heavily damaged parts of the refinery and bulk sugar loading area. Eight workers died at the scene and six others eventually succumbed to their injuries. Thirty six workers were treated for serious burns and injuries, some caused permanent, life altering conditions.

The CSB identified the following causes and contributing factors :

  • Sugar and cornstarch conveying equipment was not designed or maintained to minimize the release of sugar and sugar dust into the work area.
  • Inadequate housekeeping practices resulted in significant accumulations of combustible granulated and powdered sugar and combustible sugar dust on the floors and elevated surfaces throughout the packing buildings.
  • Airborne combustible sugar dust accumulated above the minimum explosible concentration inside the newly enclosed steel belt assembly under the silos.
  • Imperial Sugar emergency evacuation plans were inadequate. Emergency notifications inside the refinery and packaging buildings were announced only to personnel using 2-way radios and cell phones. Many workers had to rely on face-to-face verbal alerts in the event of an emergency. Also, the company did not conduct emergency evacuation drills.