Date: February 7, 2008

Location: Port Wentworth, Georgia, near Savannah

Facility: Imperial Sugar Company refinery and packaging facility

Outcome: 14 workers killed; dozens injured

At about 7:15 p.m. on February 7, 2008, a series of explosions and fires tore through the Imperial Sugar Company facility in Port Wentworth, Georgia. Fourteen workers were killed, and dozens were injured.

The facility received raw sugar, refined it into granulated sugar, and packaged sugar products for bulk distribution. Its process used screw conveyors, belt conveyors, bucket elevators, storage silos, packing equipment, and bulk loading systems to move large quantities of sugar through the operation. The material was familiar: refined sugar. The hazard was not.

The U.S. Chemical Safety and Hazard Investigation Board (CSB) later determined that the first dust explosion initiated in an enclosed steel belt conveyor located below the sugar silos. Recently installed steel cover panels allowed explosive concentrations of sugar dust to accumulate inside the enclosure. That explosion lofted sugar dust from floors and elevated horizontal surfaces, propagating secondary dust explosions through the packing buildings, parts of the refinery, and the bulk sugar loading buildings.

For engineers, the Imperial Sugar disaster is a reminder that familiar materials can become severe process hazards when combustible dust, dispersion in air, oxygen, confinement, and an ignition source are present.

A Food Product With Explosive Potential

Refined sugar is a familiar food product, but sugar dust can present a fire or explosion hazard when dispersed and ignited in air. The hazard depends not only on the material itself, but on how it is processed, conveyed, contained, released, and cleaned.
A refinery or packaging facility that handles large quantities of granulated and powdered sugar can generate dust during conveying, screening, packing, transfer, and cleanup. If that dust accumulates and is later lofted into the air, it can become the fuel for a much larger event than the initial ignition.
At Port Wentworth, the CSB found that sugar and cornstarch conveying equipment was not designed or maintained to minimize the release of sugar and sugar dust into work areas. It also found that inadequate housekeeping allowed significant accumulations of combustible granulated and powdered sugar and combustible sugar dust on floors and elevated surfaces throughout the packing buildings.

Timeline of the Disaster

Before 2007
• The Port Wentworth facility had operated for decades and had grown through expansions and modifications. Granulated sugar was moved from the refinery to three 105-foot-tall storage silos. From there, conveyors and bucket elevators carried sugar to specialty processing areas, packaging machines, and bulk loading operations.
2007
• The company installed stainless-steel cover panels over the steel belt conveyor beneath silos 1 and 2 to address sugar-contamination concerns. The CSB found that the company did not evaluate the combustible-dust hazards associated with the new enclosure, did not install a dust-removal system to keep sugar dust below the minimum explosible concentration (MEC), and did not provide deflagration vents to direct overpressure safely outside the building if the dust ignited.
About 7:15 p.m., February 7, 2008
• The primary dust explosion most likely occurred in the silo tunnel, approximately midway along the enclosed steel belt conveyor. The CSB identified an overheated bearing in that conveyor as the most likely ignition source, while also noting that the exact ignition source was not established with certainty.
Seconds later
• Massive secondary dust explosions propagated through the granulated and powdered sugar packing buildings, bulk sugar loading buildings, and parts of the refinery. Pressure waves heaved and buckled three-inch-thick concrete floors, collapsed brick walls, blocked stairwells and exit routes, and severely damaged large portions of the facility.
February 8, 2008 and following days
• Major building fires were extinguished the next day, but small fires continued for many days. Fires in the 105-foot-tall silos smoldered for more than seven days before being extinguished by an industrial firefighting company.
Casualty toll
• Eight workers died at the scene. Six more later died from their injuries at the Joseph M. Still Burn Center in Augusta, Georgia. The CSB final report states that 36 injured workers ultimately survived, including some with permanent, life-altering conditions.

Why the Disaster Escalated

The initiating event was not simply that sugar dust existed. Dust generation was part of the process, as it is in many bulk-material handling operations. The incident resulted from multiple control failures: equipment design and maintenance did not minimize dust release; housekeeping did not prevent hazardous accumulations; the enclosed conveyor allowed explosive dust concentrations to build; and emergency evacuation planning was inadequate.

CSB investigators identified seven incident causes. Sugar and cornstarch conveying equipment was not designed or maintained to minimize sugar and sugar-dust release. Housekeeping did not prevent significant combustible accumulations. Airborne sugar dust accumulated above the MEC inside the newly enclosed steel belt assembly under silos 1 and 2. An overheated bearing most likely ignited the primary explosion. That primary explosion led to massive secondary dust explosions and fires. The 14 fatalities were most likely the result of those secondary explosions and fires. Finally, emergency evacuation plans were inadequate.

The hazard was not obscure. The CSB found that Imperial Sugar and the granulated sugar refining and packaging industry had been aware of sugar dust explosion hazards as far back as 1925, and that Port Wentworth facility management had emphasized dusthandling equipment and housekeeping practices as early as 1958.

More than a Housekeeping Problem

It would be too simple to describe the Imperial Sugar disaster only as a cleanup failure. Housekeeping was critical, but the deeper issue was combustible dust hazard management.
The enclosure installed on the steel conveyor belt under silos 1 and 2 created a confined, unventilated space where sugar dust could easily accumulate above the MEC. The enclosed conveyor was not equipped with explosion vents. Equipment design and maintenance allowed dust releases and likely ignition conditions. Dust deposits on overhead and elevated surfaces provided fuel for secondary explosions.
The investigation found that the secondary dust explosions, rapid fire spread, and resulting fatalities would likely not have occurred if Imperial Sugar had enforced routine housekeeping policies and procedures to remove sugar dust from overhead and elevated work surfaces and to remove large accumulations of spilled sugar throughout the packing buildings.
Emergency systems and evacuation practices were also inadequate. The CSB found that emergency notifications inside the refinery and packaging buildings depended on two-way radios, cell phones, and face-to-face alerts, and that the company did not conduct emergency evacuation drills.

Engineering Lessons

The first lesson is that combustible dust must be treated as a process safety hazard, not merely an industrial hygiene or housekeeping issue. Facilities that handle combustible particulate solids should analyze dust generation, accumulation, dispersion, ignition, and explosion propagation as part of the process risk.

The second lesson is that enclosure changes can create new hazards. Covering a conveyor may appear to improve cleanliness or product containment, but enclosure can also increase confinement and allow dust concentrations to build. Any modification to conveying or dust-handling equipment should be reviewed for combustible-dust consequences before installation.

The third lesson is that secondary explosions can dominate the life-safety consequences. At Imperial Sugar, the primary explosion was only the beginning; the CSB concluded that the fatalities were most likely the result of the secondary explosions and fires. In combustible-dust environments, housekeeping functions as fuel control.

The fourth lesson is that maintenance is part of explosion prevention. Bearings, motors, electrical devices, friction points, and hot surfaces must be evaluated as possible ignition sources where combustible dust may be present.

The fifth lesson is that emergency planning must assume degraded conditions. After an explosion, workers may face darkness, smoke, blocked exits, structural damage, fire, debris, and injured coworkers. Alarm systems, exit routes, emergency lighting, drills, and training must be designed for those conditions, not for a normal walk-through.

Conclusion

The Imperial Sugar refinery explosions remain a major U.S. combustible-dust case study. The product was familiar, the equipment was common to bulk-material handling, and the hazard was documented. Yet failures in design, maintenance, housekeeping, hazard recognition, and emergency planning allowed a primary dust explosion to become a facility-wide catastrophe.

For engineers, the lesson is direct: dust control is fuel control. Equipment design is hazard control. Maintenance is ignition control. Evacuation planning is consequence control. Combustible dust safety requires more than knowing that dust can explode. It requires operating, inspecting, cleaning, and modifying facilities as though that fact matters every day.

U.S. Chemical Safety and Hazard Investigation Board, Investigation Report: Sugar Dust Explosion and Fire, Imperial Sugar Company, Port Wentworth, Georgia, Report No. 2008-05-I-GA, September 2009. U.S. Chemical Safety and Hazard Investigation Board, Imperial Sugar Company Dust Explosion and Fire, incident-summary page.