Industrial Utility Efficiency    

Explosion-Proof Vacuum Systems for Combustible Dust

In February of 2008, a sugar plant near Savannah, Georgia suffered the ultimate tragedy. Fourteen employees were killed and 40 injured when finely ground motes of sugar dust ignited, setting off a violent blast. If the fatalities and a tarnished reputation weren’t enough, the Occupational Safety and Health Administration (OSHA) then fined the company more than 8 million dollars in workplace violations related to combustible dust.

Although it took a fatal accident in a sugar plant to make combustible dust a national headline, power plants have been aware of the risk for years. In 1999, six workers were killed at the Ford Power Plant in Dearborn, Michigan after a natural gas explosion caused a secondary explosion induced by coal dust. The Michigan Occupational Safety and Health Administration (MIOSHA) concluded the secondary blast could have been prevented if there was adequate housekeeping to minimize accumulation of coal dust on horizontal surfaces. Unfortunately, the Ford Power Plant wasn’t the first or last industrial workplace blast; The U.S. Chemical and Safety Hazard board estimates there are on average 10 explosions, 5 fatalities, and 29 injuries per year, as a result of combustible dust-related incidents.

    
  Power plant facilities should develop and implement hazardous dust inspection, testing, housekeeping, and control procedures in order to prevent dust-related explosions. Photo courtesy of Nilfisk CFM.    

So what can be done to prevent these types of accidents in the future? In March 2008, OSHA reissued their National Emphasis Program (NEP) on combustible dust to call attention to the agency’s rigorous expectations for combustible dust-related explosion prevention, which includes random unannounced audits. Although the NEP applies to all industries that handle combustible dusts, there is a particular emphasis on power plants and coal/carbon dusts due to their high risk for dust-related explosions. The program also outlines recommendations for decreasing plants’ risk of an explosion, of which include incorporating a HEPA-filtered industrial vacuum into maintenance plans. While this is indeed a smart decision, power plant facilities that handle materials classified hazardous by the National Fire Protection Agency, such as coal, must actually use a certified explosion-proof/dust ignition-proof vacuum or properly outfitted air-operated vacuum.

Certifiable Explosion-Proof: Beware of “Dress Up”

Most power plant supervisors assume the machinery in their plants are explosion-proof, including the industrial vacuums, but as seen in multiple tragedies, it often isn’t the case. In fact, using just a basic vacuum, made of plastic and unenclosed motors, can actually add to the risk of explosion.

Explosion-proof or dust ignition-proof vacuums, as certified models are referred, are explosion-proof to the core. This means that everything from the outer shell to the internal mechanics including the motor, switches, filters and inner chambers are grounded and constructed of non-sparking materials like stainless steel. Some industrial vacuum companies offer basic models dressed up with a few anti-static accessories and describe them as suitable for explosive material. These imposters can still create arcs, sparks or heat that can cause ignition of the exterior atmosphere and overheating that can ignite dust blanketing the vacuum.

Purchasing an explosion-proof/dust ignition-proof vacuum approved by a nationally recognized testing agency such as the Canadian Standards Association (CSA) or Underwriters Laboratories (UL) will protect buyers from purchasing a poser by providing legal certification that the vacuum can be used in a particular NFPA-classified environment. It ensures every component in the vacuum from the ground up meets strict standards for preventing shock and fire hazards.

 

Air-Operated Vacuums for Combustible Dust

In environments where electricity is unavailable or undesirable, air-operated vacuums for hazardous locations are excellent alternatives; however not all air vacuums are suitable for use in hazardous locations.

Pneumatic vacuum cleaners being used to collect classed materials must still meet the NFPA requirements for equipment used in classified environments. This means that just like their electric counterparts, air-operated vacuums for combustible dust maintenance must also be completely grounded and constructed of non-sparking materials like stainless steel.

 

Filtration

Superior filtration does not have to be sacrificed on an explosion proof model, especially when collecting potentially hazardous material like coal dust. 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. In order 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. Quality HEPA filters offer an efficient, effective way to trap and retain the smallest dust particles, down to and including 0.3 microns. An ULPA filter captures even smaller particles, down to and including 0.12 microns.

    
  Nilfisk CFM A15EXP Air-Operated Vacuum: Pneumatic vacuums that meet the requirements for use in hazardous locations are a viable option when electricity isn’t available or desired, Photo courtesy of Nilfisk CFM.    

Spill Response

Spill response should also be taken into account when purchasing an explosion-proof vacuum. Although OSHA’s National Emphasis Program is specifically looking at companies that handle dry solids, manufacturers’ maintenance plans are also under the microscope. If workers might need to collect flammable or explosive chemicals, a wet-model explosion-proof vacuum should be considered, also available in both electric and air-operated versions.

 

Conclusion

It is only a matter of when, not if, OSHA will initiate enforced standards for combustible dust procedures, and with power plants being at the top of the agency’s watch list, facilities can guarantee they’ll be seeing an OSHA agent on their doorstep in the near future. Purchasing a high-quality, certified explosion-proof or intrinsically-safe vacuum is a solid first step in preventing a combustible-dust related explosion, and picking the right vacuum often raises a lot of questions, especially when it comes to disaster prevention. Like all investments, pre-sale research is key. Plant managers shouldn’t hesitate to ask the vacuum-manufacturer for an onsite analysis of their vacuum needs in order to recommend what type of explosion-proof vacuum, hose and accessories are needed for the application. With the right equipment, the 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 used consistently and in conjunction with a comprehensive maintenance plan, the facility’s investment in an explosion-proof vacuum will result in much more than just a clean plant; It will save money, protect company integrity, increase productivity, and most importantly, protect the most valuable asset, employees.

  

An ignitable material, an ignition source and oxygen- all it takes for a potential explosion at your facility. 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 to injuries, explosions cost companies millions of dollars. Between 1992 and 2002, Factory Mutual Global’s pharmaceutical and chemical clients experienced 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.

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 dusts to prevent explosions. The following are some of its recommendations:

 

  • Minimize the escape of dust from process equipment or ventilation systems;
  • Use dust collection systems and filters;
  • Utilize 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, if ignition sources are present;
  • Only use vacuum cleaners approved for dust collection;
  • Locate relief valves away from dust hazard areas; and
  • Develop and implement a hazardous dust inspection, testing, housekeeping, and control program (preferably in writing with established frequency and methods).

 

 

 

BIO:

Paul R. Miller is vice president and general manager of Nilfisk CFM. He has more than 20 years of experience in the industrial vacuum cleaner industry, serving in various capacities throughout his tenure with the company. As a former sales representative, product manager, and director of operations, Miller has seen firsthand the unique maintenance challenges manufacturers face, developing effective and efficient solutions for their dust and debris problems.

About Nilfisk CFM:

Nilfisk CFM, the industrial vacuum division of Nilfisk-Advance America, helps its industrial customers meet their individual cleaning requirements and challenges with an extensive range of high-performance vacuum cleaners. From its Malvern, Pa. headquarters, Nilfisk CFM provides industrial vacuums for heavy-duty applications that require maximum suction power; and specialty vacuums for clean applications that demand “absolute” air purity and facility cleanliness. The company’s vacuums are equipped with industry-specific features and exceptionally efficient filtration systems, ensuring dust- and debris-free facilities in the food, chemical/pharmaceutical, electronics, metalworking/powder coating, and a variety of manufacturing industries. For more information, visit www.explosionproof-vacuum.com.