U.S. Chemical Safety Board investigators said Thursday the Feb. 7, 2008, explosion at the Imperial Sugar refinery in Port Wentworth resulted from ongoing releases of sugar from inadequately designed and maintained dust collection equipment, conveyors, and sugar handling equipment.
Inadequate housekeeping practices allowed highly combustible sugar dust and granulated sugar to build up throughout the refinery’s packing buildings, CSB investigators concluded.
The first explosion — known as a “primary event” — likely occurred inside a sugar conveyor located beneath two large sugar storage silos. The conveyor had recently been enclosed with steel panels creating a confined, unventilated space where sugar dust could accumulate to an explosive concentration. Sugar dust inside the enclosed conveyor likely was ignited by an overheated bearing, causing an explosion that traveled into the adjacent packing buildings, dislodging sugar dust accumulations and spilled sugar located on equipment, floors, and other horizontal surfaces.
The result was a powerful cascade of secondary dust explosions that fatally injured 14 workers and injured 36 others, many with life-threatening burns. The refinery’s packing buildings were largely destroyed by the blasts and ensuing fires.
“Imperial’s management as well as the managers at the Port Wentworth refinery did not take effective actions over many years to control dust explosion hazards — even as smaller fires and explosions continued to occur at their plants and other sugar facilities around the country, said CSB investigation supervisor John Vorderbruegeen, P.E., who led the 19-month investigation.
The CSB report said that the sugar industry was familiar with dust explosion hazards at least as far back as 1925. Internal correspondence dating from 1967 showed that Port Wentworth refinery managers were seriously concerned about the possibility of a sugar dust explosion that could “travel from one area to another, wrecking large sections of a plant.”
However, Imperial management did not correct the underlying causes of the sugar dust problem at the Port Wentworth facility, where workers testified that spilled sugar was knee-deep in places on the floor, and sugar dust had coated equipment and other elevated surfaces.
“Dust explosions can be among the deadliest of industrial hazards, particularly inside heavily occupied buildings,” said CSB Chairman John Bresland. “But these explosions are readily prevented through appropriate equipment design and maintenance and rigorous dust-cleaning programs. I call upon the sugar industry and other industries to be alert to this serious danger.”
The report said the company had not conducted evacuation drills for its employees and that the explosions and fires disabled most of the emergency lighting, making it difficult for workers to escape from the labyrinth of explosion-damaged buildings as the fires continued to spread.