Preventing Dust Explosions: The Human Element

Plant managers need workers' help to control dust and eliminate ignition sources, which are the easiest ways to minimize the chances of an explosion. In fact, workers often are crucial to reducing and preventing dust explosions.

• By Beth Pullin
• Dec 01, 2008

Earlier this year, U.S. Rep. George Miller, D-Calif., and Rep. John Barrow, D-Ga., introduced the Combustible Dust Explosion and Fire Prevention Act of 2008. The goal of their bill was to bring about a federal standard that would require industries to prevent dust explosions in plants, factories, and warehouse facilities. According to the bill's authors, an "emergency exists concerning worker exposure to combustible dust explosions and fires." They cited at least 281 dust incidents that involved explosions from 1981 to 2005, killing 119 people and injuring more than 700. What prompted the bill were two catastrophic dust explosions: the Port Wentworth, Ga., sugar plant blast and fire in February 2008 that killed 14 people and injured more than 60, and the an earlier explosion at a pharmaceutical-manufacturing plant in Kinston, N.C. In that case, six people died, 38 were injured, and it took nearly two years before full operation and production of the factory could resume.

Miller and Barrow said there are currently not enough laws, standards, or guidelines in place to help facility managers prevent dust explosions, nor are most plant managers fully aware of how serious the problem is. Further, although some states do have regulations that have proven helpful in preventing dust and related explosions, many other states have no specific laws or regulations addressing the issue. The bill would try to rectify this by setting a nationwide standard.

Although an investigation identified 281 incidents, it is believed additional, less serious explosions are not reported. In fact, dust explosions are thought to be a relatively common occurrence in a variety of industries. Plants equipped with pneumatic handling systems, which use compressed air to move factory materials and items, and air filtration systems have an inherent dust explosion risk associated with the operation of these machines.

Understanding Dust Explosions

"Instead of gas or some other explosive material, the 'fuel' for a dust explosion is the dust itself. Very fine dust collects during the course of normal operations," said Adam Schaffer, a regional sales representative with Tornado Industries®, a manufacturer of professional cleaning tools and equipment.

Along with the dust, which can be in accumulations as small as 0.031 inches on a surface, four other elements must be in place for an explosion to occur, Schaffer said:

* The dust must be suspended in air.
* The dust must be confined to a specific area of the facility and in a quantity large enough to result in an explosion.
* Oxygen must be present and in sufficient amounts.
* There must be an ignition source, which is typically any hot surface, steam pipes, overheated tools and equipment, smoldering materials, or welding and/or cutting equipment.

"The five conditions are often referred to as the 'dust explosion pentagon,' and they must all be present concurrently in order for an explosion to occur," Schaffer said. "Although it may appear that this would be rare for all components to be in place at the same time, it is actually much more common in a busy factory/warehouse setting than many plant managers might realize." He said it is often because many managers think these conditions and situations are so rare and uncommon that they ignore them. "This is like ignoring the warning signs of a heart attack or disease," he explained. "Eventually it's going to strike, and then you wonder why nothing was done earlier to prevent it."

Reducing the Risk

Of the core elements necessary for a dust explosion to occur (dust, confined area, oxygen, and an ignition source), the two that plant managers can most easily address to help minimize the chances of an explosion are the amount of dust generated in a facility and the elimination of as many ignition sources as possible. Both of these require factory workers' assistance; in fact, workers often are crucial to reducing and preventing dust explosions.

Workers must be educated about the seriousness of dust explosions and how they can occur. This involves training and education regarding where dust tends to accumulate and which surfaces and conditions can cause it to explode. "A lot of this includes factory housecleaning," he said. "The more dust accumulation can be minimized, the fewer the chances for an explosion."

Schaffer said the factory housekeeping plan should include items such as:

* Check work tables and stations regularly for dust accumulation and clean these areas when necessary.

* Check "hidden" areas of the factory, such as under equipment, tables, and cabinets, and keep these areas clean.

* Look for and remove dust that accumulates on ceiling vents, overhead pipes, light fixtures, and fans.

* Keep floor areas clean throughout the work day.

"Keeping floor areas clean is critical. As workers walk over dusty floors, the dust can become airborne. This is one of the key elements required for a dust explosion to occur," Schaffer said.

But be careful, because sweeping floor areas can intensify the problem. Instead, he recommended using a new generation of manually operated floor sweepers that are relatively easy for all workers to use. One such system has multiple rotating brushes that clean corner areas of the floor around workstations, as well as the edges. The dust is trapped inside the machine by "upsweeping" it into a dustpan, where it is stored until emptied.

"This is a safer and more thorough way to clean workstation floor areas in a plant or factory. Additionally, it tends to be much faster than sweeping, so there is less worker downtime," he said.

As to ignition sources, workers and plant managers must be aware of the warning signs, which include:

* Electronic discharge caused by activating a switch or from machinery

* Sparks from equipment or machinery

* Friction generated when operating or moving tools, equipment, or machinery

* Hot surfaces

* Smoking and fire

Act or Wait?

The Combustible Dust Explosion and Fire Prevention Act of 2008 passed the House of Representatives in April 2008 but was not addressed by the Senate. The measure probably will have to be introduced anew in the 111th Congress to have a chance to become law.