Clearing the Air

Explosion-proof industrial vacuums can help facilities combat combustible dust hazards.

In February of 2008, a sugar plant near Savannah, Ga., suffered the ultimate tragedy. Fourteen employees were killed and 40 injured when finely ground motes of sugar dust ignited, setting off a violent blast. Adding to the damage inflicted on the facility and the company's reputation, OSHA then fined the company more than $8 million for workplace violations related to combustible dust.

Although it took a fatal accident in a sugar plant to make combustible dust a nationally recognized issue, industrial facilities have been aware of the risk for years. While the U.S. Chemical and Safety Hazard board estimates there are, on average, 10 explosions, five fatalities and 29 injuries per year resulting from combustible dust-related incidents1, these numbers are most likely underestimated, especially since smaller incidents, such as fires and blasts without injuries, happen daily and often go unreported2.

All it takes for an explosion to occur is an ignitable material, ignition source and oxygen. Most manufacturing plants have all three. In 2006, fatalities involving explosions and fires increased by 26% in the manufacturing sector, according to the Bureau of Labor Statistics' Census of Fatal Occupational Injuries.

In addition, explosions cost businesses millions of dollars. Between 1992 and 2002, Factory Mutual Global's pharmaceutical and chemical clients suffered dust explosions resulting in $32 million in losses. And, OSHA has estimated that there are approximately 30,000 U.S. facilities at risk for combustible dust explosions. Simply put, there's a lot of stake and more to come.

Late last year, OSHA issued an advance notice of proposed rulemaking on combustible dust.3 At a recent OSHA stakeholder meeting, decision makers in the industrial sector widely agreed that proper housekeeping is 50% of the equation for combating combustible dust. Eliminating hazardous dust also eliminates or greatly reduces the risk of a combustible dust incident.

Of course, facility managers should be aware of best housekeeping practices when it comes to combustible dust. Merely sweeping or cleaning with compressed air does not address the problem; in fact, these methods can create dust clouds and often just move particulate from one place to another.

On the other hand, industrial vacuums can eliminate potentially hazardous dust that settles on overhead pipes, walls, floors and machinery. The use of industrial vacuums — specifically, explosion-proof models — as a preventative housekeeping method has been a large part of OSHA discussions and will likely appear in the final standard.

Selecting a Vacuum

Purchasing a certified explosion-proof (EXP) vacuum is a solid first step toward preventing dust explosions. As with all investments, pre-sale research is key. Material handling managers shouldn't hesitate to ask a vacuum supplier for an on-site analysis of their vacuum needs to recommend the specific vacuum, hose and accessories for the application. A properly specified vacuum can be used to collect dust and debris from the floor, machinery, walls and even overhead pipes and vents. And, naturally, every manufacturer will be responsive to your needs before you buy, so look for a company that will still be there after the bill is paid. Excellent post-sale support and training will make things easier when it's time to purchase replacement parts and filters or service the vacuum.

If you plan on collecting hazardous materials — such as coal, fuel or even sugar — a certified EXP vacuum is imperative. In fact, using just a basic vacuum made of metal parts and exposed motors can increase the risk of explosion. An EXP vacuum is explosion-proof to the core. This means that everything from the outer shell to the internal mechanics — motor, switches, filters and inner chambers — is grounded and constructed of non-sparking materials, such as stainless steel.

Purchasing a vacuum approved by a nationally recognized testing agency, such as the Canadian Standards Association (CSA) or Underwriters Laboratories (UL), will protect buyers by providing legal certification that the vacuum can be used in a particular National Fire Protection Association (NFPA)-classified environment. Certification by a third party ensures that every component in the vacuum meets strict standards for preventing shock and fire hazards.

In environments where electricity is unavailable or undesirable, air-operated vacuums for hazardous locations are excellent alternatives, but not all air-operated equipment is explosion-proof. Referred to as “intrinsically-safe,” pneumatic vacuums for hazardous locations still must meet the requirements for use in NFPA-classified environments.

Accessories

Superior filtration does not have to be sacrificed on an explosion-proof model, especially when collecting potentially hazardous materials. For peak safety and operating efficiency, an EXP vacuum should have a multi-stage, graduated filtration system, which uses a series of progressively finer anti-static filters to trap and retain particles as they move through the vacuum. To eliminate combustible dust from being exhausted back into the ambient air, a HEPA or ULPA filter can be positioned after the motor to filter the exhaust stream. HEPA filters offer an efficient, effective way to trap and retain the smallest dust particles, down to and including 0.3 microns. ULPA filters capture even smaller particles, down to and including 0.12 microns.

The ability to safely and easily collect liquid spills should also be taken into account when purchasing an EXP vacuum. Although OSHA's national emphasis program specifically targets companies that handle dry solids, manufacturers' maintenance plans are also under the microscope. If workers need to collect flammable or explosive chemicals, an EXP vacuum capable of collecting liquids should be considered. These wet-models are available in both electric and air-operated versions.

If used consistently and in conjunction with a comprehensive maintenance plan, an EXP vacuum can do more than just clean a facility. It can save money, protect brand integrity, increase productivity, and, most importantly, protect the most valuable asset of all — your employees.

Paul Miller is vice president and general manager of Nilfisk CFM, a provider of industrial and specialty vacuums.

The NFPA Dust Standard

National Fire Protection Association (NFPA) 654 — Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids — contains comprehensive guidance on the control of dust to prevent explosions. Following are some of its recommendations:

  • Minimize the escape of dust from process equipment or ventilation systems;
  • Use dust collection systems and filters;
  • Use work surfaces that minimize dust accumulation and facilitate cleaning;
  • Provide access to all hidden areas to permit inspection;
  • Inspect for dust residues in open and hidden areas at regular intervals;
  • Clean dust residues at regular intervals;
  • Use cleaning methods that do not generate dust clouds, especially if ignition sources are present;
  • Only use vacuum cleaners approved for dust collection;
  • Locate relief valves away from dust-hazard areas;
  • Develop and implement a hazardous dust inspection, testing, housekeeping and control program, preferably in writing with established frequency and methods.

  1. “Investigation Report: Combustible Dust Hazard Study.” U.S. Chemical Safety and Hazard Investigation Board. 02 Jan 2008. www.csb.gov/completed_investigations/docs/Dust%20Final%20Report%20Website%2011-17-06.pdf

  2. “OSHA Combustible Dust Prerule Agenda.” Combustible Dust Policy Institute. 03 Jun 2009. www.combustibledust.com

  3. “U.S. Department of Labor's OSHA announces rulemaking on combustible dust hazards.” National News Release. Occupational Health and Safety Association. 03 Jun 2009. www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=NEWS_RELEASES&p_id=17828

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