Thirteen employees were killed when the Imperial Sugar facility in Savannah, Ga., exploded into an inferno on Feb. 7. The tragedy was the latest in a series of similar deadly accidents that had occurred since 2003.
In January of that year, an explosion destroyed the West Pharmaceutical Services plant in Kinston, N.C., and caused six deaths and dozens of injuries. A month later, a fire damaged the CTA Acoustics manufacturing plant in Corbin, Ky., and killed seven employees. Finally, in October 2003, a series of explosions at the Hayes Lemmerz manufacturing facility in Huntington, Ind., severely burned two employees and injured a third. One of the employees died as a result.
The cause of these disasters wasn’t gasoline or any other obviously flammable, corrosive, toxic, or explosive substance. It was seemingly harmless, nearly invisible dust.
In 2004, investigators from the U.S. Chemical Safety and Hazard Investigation Board (CSB), an independent federal agency that investigates industrial chemical accidents, got involved. While the CSB has no direct regulatory authority, it does make recommendations to facilities and government agencies, such as OSHA.
The agency launched a two-year, nationwide hazard study to determine if federal action is warranted. Angela Blair, chemical incident investigator for the CSB, served as lead investigator for that study. “We found, in all three cases, that voluntary standards, had they been followed, would have prevented the incidents or greatly reduced the effects,” says Blair. She’s referring to voluntary standards issued by the National Fire Protection Association (NFPA)—particularly NFPA 654 and NFPA 484—that are effective in preventing dust explosions.
West Pharmaceutical Services produced rubber stoppers for medical purposes. Blair explains that, during processing, sheets of rubber were dipped into liquid that had a fine polyethylene powder mixed into it. As the sheets cooled, the polyethylene dried, was picked up by air currents in the facility and drifted above a suspended ceiling over the work area. Blair notes that the company employed a full-time cleaning crew. However, “They never cleaned above the suspended ceiling. They were housekeeping like crazy but not in the area that matters,” she says. That dust was then ignited by a source that is still being investigated.
CTA Acoustics manufactured fiberglass insulation for automotive applications, and Hayes Lemmerz made aluminum automot ive wheels. For CTA Acoustics, resin dust was to blame, and for Hayes Lemmerz, the problem was aluminum dust.
Digging deeper, the CSB uncovered a history of similar incidents. Blair and her investigative team discovered that, since 1980, there have been 358 fires and explosions caused by combustible dust. Those incidents resulted in 783 injuries and 133 fatalities.
In November 2006, CSB issued its final report in which it urged OSHA to create a new regulatory standard to prevent dust fires and explosions.
Nearly a year passed. Then, in October 2007, OSHA launched a national emphasis program on combustible dust. In 2008, the Imperial Sugar accident forced the issue back into the headlines.
“The Imperial accident last month is the deadliest industrial dust explosion in the U.S. since 1980,” said CSB board member William E. Wright on March 12 in testimony before the U.S. House of
Representatives Education and Labor Committee.
“OSHA’s existing requirements— including the generalduty clause and the housekeeping standard—apply to combustible dust hazards,” said Wright. He also noted that OSHA’s grain dust standard, issued in 1987, applies to grain handling facilities. According to Wright, however, these guidelines are ineffective. “Some state and local governments have adopted NFPA standards as part of their fire codes, but many have not,” Wright said. “Our study also found that enforcement of these codes at industrial facilities is, at best, uneven.”
Bending under the pressure, OSHA in March reissued its original directive and indicated that every regional OSHA office will inspect facilities for dust hazards. Specifically, inspectors will search for accumulations of hazardous amounts of dust, which OSHA defines as those greater than 1/32 of an inch—the thickness of a paper clip. “Likely areas of dust accumulations within a plant are structural members, conduit and pipe racks, cable trays, floors, above ceiling and on and around equipment,” reads the directive.
For some, however, the directive wasn’t enough. So, on April 30, the U.S. House of Representatives passed the Worker Protection Ag a ins t Combus t i b l e Dus t Explosion and Fires Act (H.R. 5522), which requires OSHA to issue specific rules regulating combustible industrial dusts. The bill was introduced by Reps. George Miller (D-Calif.) and John Barrow (D-Ga.). It’s currently awaiting approval in the Senate. If the measure becomes law, OSHA will be required to issue interim rules on combustible dust within 90 days and final rules within 18 months.
Determining Risk
Now is the time for material handling and facility managers to determine if they are at risk for an OSHA penalty, or worse, a deadly blast. Accurately assessing risk requires knowledge. “During our hazard study, a common factor was a lack of awareness of the hazard,” says Blair. “People need to educate themselves about the problem.”
And, education starts with defining the problem. Described as the extremely rapid burning of a material, ‘deflagration’ is what happens when dust is ignited. “There are basically four criteria required for a deflagration to occur,” says Allen Wagoner, vice president of Flamex Inc. (Greensboro, N.C.), a supplier of spark detection and extinguishing equipment. “The dust particle size must be small enough, the dust must be in sufficient concentration, the dust must be suspended and it must be ignited. A facility is at risk if there is a possibility of all four of these elements coming together within the lifetime of the plant.”
An operation is also at risk if its processes result in the release of fine particles that can burn. Metals, wood, coal, plastics, biosolids, sugar, paper, soap and textiles can all produce combustible dust. As a result, a variety of industries— food products, plastics, automotive parts, rubber, furniture, textiles, grain, fertilizer, pesticides, recycling, pharmaceuticals and metals—will be targeted by OSHA’s new emphasis.
“Many solid or bulk materials may not be explosive but may generate combustible dusts through handling or processing,” Wright said in his testimony before the House. “For example, plastic pellets shipped from a polyethylene plant rarely pose an explosion hazard until they are handled and generate small particles as part of a different process, thus producing dust particles with explosion potential.”
Wagoner adds: “If the dust is about the size of table salt or smaller (420 microns or less) and is allowed to accumulate, you have a hazard to be concerned about.” He emphasizes that it doesn’t take a lot of dust to create a dangerous situation. “For wood dust, it is 60 grams per cubic meter. For rubber dust, it is half of that. Dust accumulations of 1/16 of an inch are usually considered thick enough to require immediate cleaning.”
Hard- to- reach areas—l ike those on high beams or in the nooks and crannies of processing equipment—are places where dust tends to accumulate, and confined spaces present additional hazards. The CSB’s Wright said the Imperial Sugar facility had “horizontal surfaces” where dust collected. “These included overhead floor joists, rafters, ductwork, piping and equipment,” he explained.
Prevention is Everything
“We know that dusty environments are dangerous environments,” says Bill Stevenson, vice
president of engineering at CV Technology (Jupiter, Fla.), a company devoted to the prevention of industrial dust explosions. “But, solving that problem is not as simple as handing someone a broom and telling them to get busy.”
Stevenson points out that eliminating dust from hard-to-reach areas creates additional safety issues. “Companies have spent tremendous amounts of money on scaffolding, safety nets and harnesses to clean areas that are 30 to 50 feet or higher,” he says. “Housekeeping alone won’t solve this problem. The bigger problem is figuring out the best way to minimize accumulations of dust in hard-to-reach areas.”
Prevention may entail a redesign of process equipment to reduce dust releases or altering facility design to minimize horizontal surfaces. “Ignition sources need to be carefully controlled, including not just electrical sources of ignition but also thermal sources of ignition, such as ovens, frictionally heated surfaces and welding and cutting operations,” Wright said in his testimony. “Finally, workers must be made aware of the hazards of combustible dust and trained on safe methods for working in dust environments and for handling and removing dust accumulations.”
One common ignition source is a spark, which, by itself, is not dangerous. Add dust, however, and it’s a recipe for disaster. “Sparks are a very common danger,” says Bob Barnum, vice president of sales at GreCon Inc. (Tigard, Ore.), a supplier of spark detection and extinguishing equipment. “A dull tool, damaged fan bearing, an overheated motor or electric sparks, foreign bodies in conveyed material, defective parts on the production line and friction-generating process are causes of these events.”
Spark detection and extinguishing systems, such as those offered by GreCon and Flamex, can detect minute sparks in ductwork and immediately extinguish them. These systems can be set to activate an extinguishment system, shut off the means of transport or stop the affected production area. Most commonly, the systems are equipped with sensors that detect a spark and then automatically trigger a mist of water to put it out.
“If the process machinery produces a spark that travels in the ducting, the sensor ‘sees’ it, sends an alarm to a control panel, and that activates a water spray,” says Barnum. “Then, the spark is extinguished so that it doesn’t travel to dust-bag filters or silos and propagate into a disastrous situation.” Barnum says the equipment can respond to a spark in 200 milliseconds (two-tenths of a second).
Dust collectors should also be monitored. “More than half of all dust explosions occur in dust collectors,” says Stevenson. In addition, “pneumatic conveyors, often used to transfer powders in bulk, can be conduits for flame and pressure propagation from one area to another.”
When Tomatoes are HazMat
On June 3, when the U.S. Food and Drug Administration (FDA) issued a warning to consumers to avoid raw red plum, red Roma, and red round tomatoes due to a nationwide salmonella outbreak, Baldor Specialty Foods Inc. was ready.
Baldor, headquartered in Bronx, N.Y., is one of the larger importers and distributors of produce in the northeastern U.S. It operates two distribution facilities—one 180,000-square foot facility in Bronx and a 25,000-square foot satellite DC outside of Boston.
Preparing for the unexpected is expected at Baldor. The company is among a few distributors in the country to be HACCP (Hazard Analysis Critical Control Points) accredited by the American Institute of Baking (AIB International). It’s a program often used by manufacturers for identifying and analyzing food-safety hazards, monitoring critical control points and establishing preventive and corrective procedures to keep the food supply safe.
“Our HACCP manager makes us do mock recalls,” explains Michael Muzyk, president of Baldor. On a regular basis, Baldor employees go through a recall process so they can be prepared when the real thing happens. “It’s like a fire drill,” he adds.
“When the FDA’s warning came out, it prompted an emergency conference call with senior management,” says Muzyk. “We made the decision not to sell tomatoes that have not been cleared.”
Baldor carries 40 line items of tomatoes. The distributor had to identify which items were red plum, red Roma and red round tomatoes—the potentially infected varieties—and which were cherry, grape and on the vine—the safe ones, according to the FDA. The process was complex and largely manual since tomatoes don’t come with traceable barcodes.
“We will eventually see barcodes on every produce box,” Muzyk predicts. “Produce is one of the last commodities to have it. We have to be able to trace the product.”
The next step was to review lot numbers and document point of origin for each tomato variety. Baldor purchases tomatoes from growers in several states; however, many of its suppliers are in Florida. The FDA had identified several areas that were not associated with the outbreak and thus deemed safe points of origin. Only certain counties in Florida had been cleared.
Baldor continued to purchase tomatoes that came from FDA-cleared areas and pulled tomatoes that came from growers in unsafe areas out of inventory. Employees manually deleted the associated line items from the computer system and moved the tomatoes into a separate, temperature-controlled zone in the facility.
“We call it a virtual warehouse because the tomatoes have been physically removed from inventory,” says Muzyk. “Customers can’t see them in the computer system, so they are not sellable.” However, they were stored in ideal conditions because, at any given moment, some of them could be cleared by the FDA and then taken out of isolation and sold.
Baldor also substituted safe tomatoes automatically for unsafe ones ordered by customers. The distributor notified suppliers that it wouldn’t be buying their tomatoes until their area was cleared by the FDA and told customers it would automatically substitute their orders. The company also told customers they could return tomatoes that came from unsafe states. While some customers simply threw their tomatoes away, others sent them back to Baldor, and the distributor destroyed them using the steps detailed in its HACCP plan.
“The process is like second nature to us,” Muzyk says.
One of the reasons dust can be so deadly is because it can fuel a chain reaction of multiple explosions, each becoming more destructive. “Say an explosion bursts the side of a dust collector, but the plant is clean,” Stevenson says. “The flames may damage some zone around the collector, but the damage will stop at the end of the zone because the plant is clean. In the second scenario, there is dust on the floor, beams and equipment, and when the collector bursts, a pressure wave sweeps the dust up into a cloud, and the flame ignites the dust and spreads. That’s called a secondary explosion, and those are the ones that make it into the newspapers.”
“In general, a dust collector should be considered a potential explosion hazard,” adds Wagoner. “The dust explosion pentagon illustrates the five elements required for a dust explosion: fuel, oxygen, dispersion, confinement and ignition. Most people do not realize that the first four elements may potentially exist in a dust collector during normal operation. The ignition source is the only element missing.”
Wagoner says Flamex equipment prevents that ignition source from getting into the dust collector. Sensors placed in the ductwork from the process machinery to the collector detect sparks and extinguish them before they can travel.
“The most common way to protect dust collectors is to use explosion vents,” says Stevenson. “Another option is to use suppression.” NFPA 69 defines dust explosion suppression systems as equipment that detects and stops combustion in a confined space to prevent pressure buildup that could result in an explosion. Explosion vents, described in NFPA 68, relieve pressure by allowing heated gases to escape.
Stevenson strongly recommends that material handling and facility managers review NFPA 654. The standard suggests that a facility get a qualified risk analysis during which dust samples are tested in a lab for combustibility. Processes are evaluated to determine risk of explosion, and a plan of attack is developed to reduce overall explosion risk.
Reducing that risk will help avoid production downtime, extensive facility damage, and most importantly, tragic deaths.
For more information about the CSB’s investigation into combustible dust, or for guidance on how to prevent dangerous dust incidents, e-mail [email protected].
