NFPA Journal®, November/December 2004
by Stephen Barlas
On January 29, 2003, an accumulation of dust covering the top side of a suspended ceiling above a production room at the West Pharmaceutical Services Inc. plant in Kinston, North Carolina, exploded, killing six workers and injuring 38 people, including two firefighters.
Because the U. S. Food and Drug Administration regulated West Pharmaceutical’s customers, housekeeping in the ground-floor room had been a high priority, particularly around a rubber-processing batchoff machine. The machine, which sat 3 feet (0.9 meters) below the room’s suspended ceiling, had operated 24 hours a day, five or six days a week, since 1987, where rubber strips were coated by dipping them into a slurry containing Acumist, a finely powdered grade of combustible polyethylene. The rubber was used for drug-delivery components such as syringe plungers, septums, and vial seals.
The combustible polyethylene can become explosive when conditions for a dust explosion are met: dust of the right particle size; air or other oxidizer; dust dispersion; confinement, such as in a building or enclosure; and ignition source. In this case, investigators couldn't identify the ignition source or the source of the dispersion mechanism for the dust as it rested in the area above the ceiling.
So what happened? According to a report the U.S. Chemical Safety and Hazard Investigation Board (CSB) released last September, the blast and resulting fire, which turned half the 150,000-square-foot (13,935-square-meter) factory into a charred skeleton, resulted when the layer of combustible polyethylene dust ignited. Although plant maintenance crews regularly and assiduously vacuumed the combustible dust from the walls and underside of the suspended ceiling, they were unaware that the room’s comfort air system was pulling the dust up above the ceiling, where it had accumulated to a depth of 0.25 to 0.5 inches (0.63 to 1.2 centimeters).
If uniformly suspended, combustible dust just 1/32 of an inch (0.0794 centimeters) deep can create a cloud of optimal explosive concentration 10 feet (3 meters) high, according to the 2000 edition of NFPA 654, Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids. NFPA 654 specifies engineering and construction requirements for dust-tight segregation of hazardous building zones, classification of electrical equipment in dusty areas, and special air-conditioning explosion venting. It also recommends management systems for fugitive dust emissions, associated housekeeping, and employee training.
CSB member John Bresland says the disaster at West Pharmaceutical would likely have been avoided had the company understood the hazard and followed the recommendations of NFPA 654. The CSB has recommended to the North Carolina Building Code Council that the state amend its building code to make compliance with NFPA 654 mandatory. The CSB also recommended that North Carolina train its fire inspectors in NFPA 654.
One of three 2003 explosions
The West Pharmaceutical accident was one of three industrial dust explosions in 2003 that resulted in worker deaths. On February 20, phenolic resin powder used as a binder in the production of fiberglass acoustic insulation for the automotive industry exploded at the CTA Acoustics plant in
Bill Hoyle, a CSB investigation manager, says accumulated dust in the production areas of both facilities led to the explosions and deaths at the Kentucky and Indiana factories. As of mid-December, the CSB had not completed its reports on those explosions.
Because of these three incidents, the CSB has undertaken a major study of industrial accidents involving dust explosions over the past 20 years.
"Our preliminary information shows that there have been 150 dust explosions resulting in more than 80 deaths over the past two decades," CSB representative Dan Horowitz says. Hoyle, who is heading the investigation, traveled to Baltimore in October to attend a meeting of NFPA’s Technical Committee on Handling and Conveying of Dusts, Vapors, and Gases, which has jurisdiction over NFPA 654. He asked for help sifting the data he had assembled on those 150 accidents and for advice on how the CSB might proceed if, based on final findings, it decided to recommend a national workplace safety standard for industrial dust. NFPA 654 is currently in the revision process and a new edition will be voted on at the June 2005 World Safety Conference & Exposition® in Las Vegas.
In 1987, the Occupational Safety and Health Administration (OSHA) adopted a dust safety standard for grain-handling facilities in response to repeated loss of life from grain elevator explosions. Other than these regulations and those issued by the Mine Safety and Health Administration to regulate coal dust, no specific federal program currently provides comprehensive safety standards to prevent and control the hazards of combustible dusts such as those found at West Pharmaceutical, CTA Acoustics, and Hayes Lemmerz.
In its investigation of the disaster at West Pharmaceutical, the CSB found that plant officials weren’t sufficiently aware of the dangers of combustible dust, but they hadn’t violated any laws. When the Kinston plant was built in 1975 and expanded in 1984, North Carolina had no fire code. In 1991, the state adopted the Standard Fire Prevention Code published by the Southern Building Code Congress International (SBCCI). In 1994, SBCCI merged with two other
Unlike the extensive coverage various NFPA standards give the hazards of combustible dust, the IFC contains only a single page of text in Chapter 13, "Combustible Dust-Producing Operations," on the subject, and that page does not include specific engineering and management system measures to control the hazard.
Chapter 13 references various NFPA standards for combustible dust hazards but does not mandate compliance. Rather, the IFC authorizes the authority having jurisdiction to enforce applicable provisions of NFPA standards to prevent and control dust hazards on a case-by-case basis and issue operating permits to facilities that use or generate combustible dust. North Carolina leaves the issuance of a permit up to individual counties, and Lenoir County, where Kinston is located, does not require permits. So the West Pharmaceutical plant was under no obligation to comply with Chapter 13 of the IFC.
Thought dust was inert
Why did West Pharmaceutical maintenance workers regularly see the accumulations of dust above the suspended ceiling and fail to remove them? Robert Gombar, an attorney for West Pharmaceuticals, says they thought the dust was inert—even though the 1990 material safety data sheet (MSDS) for Acumist advises users to consult NFPA 654.
West Pharmaceutical executives didn’t make the connection between that MSDS and the potential for dangerous dust accumulations from the Acumist-containing slurry used in the batchoff machine, Gombar says. When West Pharmaceutical started using Acumist in 1990, it was in small quantities as a dusting agent, not as an ingredient in a slurry, which calls for much larger amounts of the polyethylene resin, greatly multiplying the explosion hazard.
In 1994, however, it began using a concentrated water-based paste of Acumist powder to which water was added at the plant to form the anti-tack slurry, into which rubber strips were dipped to prevent them from sticking together when they came out of the batchoff machine. Until that time, West Pharmaceutical used a different slurry containing a different chemical dust, zinc stearate.
The MSDS for this new additive contained no combustibility warnings, and West Pharmaceutical did not explore the implications of using Acumist in greater quantities, Gombar says.
When North Carolina adopted the IFC in 2002, the state amended it to say that building permits were optional for companies producing combustible dust. Barry Gupton, the liaison between the office of the North Carolina Fire Marshal and the North Carolina Building Code Council, says there is currently no petition before the council to amend Chapter 13 of the IFC to make NFPA 654 mandatory. However, the council is considering making it mandatory for counties to require companies to obtain operating permits, which would trigger application of the North Carolina Fire Code.
West Pharmaceutical has built a new Kinston plant, but that facility no longer produces rubber, so compliance with NFPA 654 is not an issue there.
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