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Imperial Sugar Company Dust Explosion and Fire

Overview

On February 7, 2008, a series of sugar dust explosions and fires occurred at the Imperial Sugar refinery in Port Wentworth, Georgia. The event was fueled by massive accumulations of combustible sugar dust throughout the packaging building and other areas of the facility. The incident resulted in 14 fatalities, numerous serious burn injuries, and major destruction of the plant.

Incident Snapshot

Field Value
Facility / Company Imperial Sugar Company
Location Port Wentworth, GA
Incident Date 02/07/2008
Investigation Status The CSB's final report was released at a public meeting in Savannah, GA on September 24, 2009.
Accident Type Combustible Dust Explosion and Fire
Final Report Release Date 09/24/2009

What Happened

  • On February 7, 2008, at about 7:15 p.m., a series of sugar dust explosions occurred at the Imperial Sugar manufacturing facility in Port Wentworth, Georgia.
  • 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 unknown source ignited the 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.

Facility and Process Context

  • The Imperial 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 105-foot tall sugar storage silos.
  • 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 facility had three 40-foot diameter, 105-foot tall concrete silos.
  • The south packing building was a four-story, steel-frame structure with 3-inch thick poured concrete floors and brick exterior walls.
  • The Bosch packing building was a four-story, steel frame, corrugated steel-sided structure with poured concrete floors.
  • Dozens of screw conveyors, bucket elevators, and horizontal conveyor belts transported granulated sugar throughout the packing buildings.
  • In 2007, Imperial Sugar installed a stainless steel frame with top and side panels to fully enclose each belt assembly in the silo tunnel and penthouse.
  • The enclosure on the belt conveyors in the penthouse could have been designed to safely vent an explosive overpressure outside the building, but designing a deflagration vent system for the belt conveyor in the silo tunnel was impractical.

Consequences

  • Fatalities: 14 worker fatalities
  • Injuries: 36 workers were treated for serious burns and injuries; some caused permanent, life altering conditions
  • Environmental Release: Not reported
  • Facility Damage: The explosions and subsequent fires destroyed the sugar packing buildings, palletizer room, and silos, and severely damaged the bulk train car loading area and parts of the sugar refining process areas.
  • Operational Impact: The packing buildings, granulated sugar silos, and palletizer room were destroyed. The bulk sugar loading area and parts of the refinery were severely damaged. The granulated sugar fires in the 105-foot tall silos continued to smolder for more than 7 days before being extinguished.

Key Findings

Immediate Causes

  • 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 silos 1 and 2.
  • An overheated bearing in the steel belt conveyor most likely ignited a primary dust explosion.
  • The primary dust explosion inside the enclosed steel conveyor belt under silos 1 and 2 triggered massive secondary dust explosions and fires throughout the packing buildings.
  • The 14 fatalities were most likely the result of the secondary explosions and fires.
  • Imperial Sugar emergency evacuation plans were inadequate.

Contributing Factors

  • 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 minimum explosible concentration.
  • The enclosed steel conveyor belt was not equipped with explosion vents to safely vent a combustible dust explosion outside the building.
  • Company management and supervisory personnel had reviewed and distributed the OSHA Combustible Dust National Emphasis Program shortly after it was issued in October 2007, but did not promptly act to remove all significant accumulations of sugar and sugar dust throughout the packing buildings and in the silo penthouse.
  • The secondary dust explosions, rapid spreading of the fires throughout the facility, 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 remove the large accumulations of spilled sugar throughout the packing buildings.
  • The Port Wentworth facility risk assessment performed by Zurich Services Corporation in May 2007 and the report submitted to Imperial Sugar management did not adequately address combustible dust hazards.
  • The fire suppression piping system was heavily damaged in the initial explosions and rendered ineffective.
  • The emergency lights that worked did not provide adequate illumination.
  • Large, complex mechanical equipment and long package conveyors 3 to 4 feet above the floors impeded rapid and safe emergency egress in the darkened work areas.
  • The dust collection equipment was in disrepair, and some equipment was significantly undersized or incorrectly installed.
  • Some dust duct pipes were found to be partially, and in some locations, completely filled with sugar dust.

Organizational and Systemic Factors

  • Prior to the incident, the company did not have a dedicated officer level position responsible for workplace safety.
  • The corporate safety director reported to the director of human resources in the administration department.
  • The director of human resources had minimal occupational safety management experience and training.
  • Imperial Sugar management and staff accepted a riskier condition and failed to correct the ongoing hazardous conditions, despite the well-known and broadly published hazards associated with combustible sugar dust accumulation in the workplace.
  • The process wherein successful operations continue despite existing rejectable conditions or unsafe behaviors results in relaxing the minimum performance standard without basis is called “normalization of deviance.”
  • Imperial Sugar management was aware of the hazards associated with combustible sugar dust, but in the absence of any major catastrophic incident during many years of facility operation, the hazardous conditions went uncorrected.
  • Management did not enforce adequate equipment design and maintenance practices to control sugar dust and spilled sugar.
  • Management did not ensure housekeeping activities were adequate to prevent sugar dust and spilled sugar from accumulating to unsafe levels in the workplace.

Failed Safeguards or Barrier Breakdowns

  • The newly enclosed steel belt assembly was not equipped with a dust removal system.
  • The newly enclosed steel belt assembly was not equipped with explosion vents.
  • The dust collection equipment was in disrepair.
  • Some dust collection equipment was significantly undersized or incorrectly installed.
  • The written emergency response procedure directed workers to use an intercom system to report an emergency, but the intercom system was not used inside the refinery or packing buildings.
  • There were no audible or visual alarm devices in the work areas.
  • The company did not conduct evacuation drills.
  • The fire sprinkler system failed because the explosions ruptured the water pipes.
  • Imperial Sugar had no written policy or procedure to require classifying hazardous areas or require electrical devices rated for such locations at the Port Wentworth facility.
  • Some electrical devices in dusty areas were poorly maintained, such as having missing covers or open doors on many breaker panels and other electrical enclosures.
  • The ceilings in areas where sugar dust was present were not protected with a suspended ceiling to minimize dust accumulation on rafters, conduit, conveyors, piping, and other equipment.
  • The company did not train the workers on the hazards of combustible sugar dust.
  • The company did not provide work location specific evacuation training to all employees and contractors.

Recommendations

  1. 2008-05-I-GA-R1 | Recipient: Imperial Sugar Company | Status: Not specified | Apply the following standards to the design and operation of the new Port Wentworth facility: NFPA 61; NFPA 499-Recommended Practice for the Classification of Combustible Dusts and Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas; NFPA 654-Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids; NFPA Handbook, Electrical Installations in Hazardous Locations; NFPA 70, Article 500 - Hazardous (Classified) Locations.
  2. 2008-05-I-GA-R2 | Recipient: Imperial Sugar Company | Status: Not specified | Conduct a comprehensive review of all existing Imperial Sugar Company sugar manufacturing facilities against the standards listed in recommendation R1 and implement identified corrective actions.
  3. 2008-05-I-GA-R3 | Recipient: Imperial Sugar Company | Status: Not specified | Implement a corporate-wide comprehensive housekeeping program to control combustible dust accumulation that will ensure sugar dust, cornstarch dust, or other combustible dust does not accumulate to hazardous quantities on overhead horizontal surfaces, packing equipment, and floors.
  4. 2008-05-I-GA-R4 | Recipient: Imperial Sugar Company | Status: Not specified | Develop training materials that address combustible dust hazards and train all employees and contractors at all Imperial Sugar Company facilities. Require periodic (e.g., annual) refresher training for all employees and contractors.
  5. 2008-05-I-GA-R5 | Recipient: Imperial Sugar Company | Status: Not specified | Improve the emergency evacuation policies and procedures at the Port Wentworth facility; specifically, install an emergency alert (alarm) system in the facility, and require routine emergency evacuation drills and critiques.
  6. 2008-05-I-GA-R6 | Recipient: AIB International | Status: Not specified | Incorporate combustible dust hazard awareness into employee and member companies’ training programs, such as the Safety and Health Management Systems training course. Include combustible dust characteristics, especially ignition energy and minimum explosible concentration; best practices for minimizing dust accumulation, especially on elevated surfaces; and safe housekeeping practices.
  7. 2008-05-I-GA-R7 | Recipient: AIB International | Status: Not specified | Add specific combustible dust inspection requirements and metrics to the Food Contact Packaging Facility audit procedures.
  8. 2008-05-I-GA-R8 | Recipient: American Bakers Association | Status: Not specified | Actively promote improvements in combustible dust hazard awareness and control throughout the wholesale baking industry by publishing bulletins or safety guidance that address combustible dust characteristics including ignition energy, minimum explosible concentration, best practices for minimizing dust accumulation, and safe housekeeping practices.
  9. 2008-05-I-GA-R9 | Recipient: Risk Insurance Management Society, Inc | Status: Not specified | Require member companies to develop and implement combustible dust hazard awareness training for all facility audit personnel, and incorporate combustible dust hazard identification in the audit protocols.
  10. 2008-05-I-GA-R10 | Recipient: Zurich Services Corporation | Status: Not specified | Ensure that all risk engineers are trained in the hazards of combustible dust, and that refresher training occurs at regular intervals. Provide a copy of your combustible dust hazard awareness training materials to your clients who deal with combustible dust.
  11. 2008-05-I-GA-R11 | Recipient: Occupational Safety and Health Administration | Status: Not specified | Proceed expeditiously, consistent with the Chemical Safety Board’s November, 2006 recommendation and OSHA’s announced intention to conduct rulemaking, to promulgate a comprehensive standard to reduce or eliminate hazards from fire and explosion from combustible powders and dust.

Key Engineering Lessons

  • Confining a belt conveyor in an enclosure without adequate explosion venting can allow combustible dust to accumulate to explosive concentrations and intensify the consequences of ignition.
  • Equipment design and maintenance must minimize fugitive dust release into the work area; otherwise, dust can accumulate on floors and elevated surfaces and provide fuel for secondary explosions.
  • Housekeeping is a critical control for combustible dust hazards because accumulated dust on overhead and horizontal surfaces can be lofted by a primary event and propagate secondary explosions.
  • Dust collection systems must be properly designed, installed, and maintained; undersized, incorrectly installed, or damaged systems can fail to control hazardous dust accumulation.
  • Emergency protection and egress systems must remain effective after an initial explosion; damaged suppression piping, inadequate alarms, and poor evacuation provisions can worsen outcomes.

Source Notes

  • Priority 1 final report information was used to resolve conflicts where supporting documents differed, including casualty counts and the detailed causal sequence.
  • Supporting testimony and transcript documents were used to supplement context, contributing factors, and lessons where consistent with the final report.
  • The recommendation status change summary was used only for the status of CSB Recommendation No. 2008-05-I-GA-R11, which was later closed as Reconsidered/Superseded.

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