Protect valuable assets with explosion-proof vacuums
08/01/2008
Choosing the wrong vacuum can put your facility, processes, and personnel at risk
By Paul Miller, Nilfisk CFM
In the past several years, plants across the United States have seen an increase in dust-related explosions. From sugar dust to phenolic resin, blasts in the workplace are becoming all too common. Although critically controlled environments–like those found in food, pharmaceutical, and electronics manufacturing–may not contain an explosive concentration of combustible dust as seen in the plants that did fall victim to dust-related catastrophes, these facilities are not immune from similar disasters that can destroy more than just infrastructure, especially those that handle hazardous materials.
In response to the recent blasts, the Occupational Safety and Health Administration (OSHA) is embarking on a journey to develop industry standards of prevention. The agency’s preliminary research includes random audits of any facility that handles powder and bulk solids. And in the meantime, officials have made suggestions that include incorporating an industrial HEPA-filtered vacuum into maintenance plans, but for facilities that are handling materials classified hazardous by the National Fire Protection Agency (NFPA), incorporating the wrong vacuum can actually add to the risk. For this reason, cleaning with a certified explosion-proof vacuum (EXP) that surpasses industry standards is critical.
Certifiable explosion-proof: Beware of ‘dress up’
Operators and managers cannot afford to take chances when it comes to protecting the facility. Look for EXPs that 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 should be grounded and constructed of non-sparking materials such as stainless steel. Some companies offer basic models dressed up with a few anti-static accessories and describe them as suitable for explosive material. These imposters may still create arcs, sparks, or heat that can cause ignition of the exterior atmosphere and overheating that can ignite dust blanketing the vacuum.
Approval by a nationally or internationally recognized testing agency such as CSA is imperative and will protect the buyer from purchasing a “poser.” Users should look for models that state they are certified for use in their specific NFPA classified environments. This provides legal certification and ensures that every component in the vacuum from the ground up meets strict standards for preventing shock and fire hazards.
Explosion-proof vs. intrinsically safe
In environments where electricity is unavailable or undesirable, pneumatic vacuums for hazardous locations are excellent alternatives. It is important to note that only electric vacuums can be certified and deemed “explosion-proof,” but properly outfitted pneumatic vacuums, referred to as “intrinsically safe,” often pack the same punch as their electric counterparts while still meeting the requirements for use in an NFPA classified environment. Again, beware of companies that refer to their pneumatic models as certified explosion-proof. Testing agencies for air-operated machines simply do not exist.
Filtration
As with any critical environment vacuum, superior filtration should not be sacrificed on an explosion-proof model. For peak operating efficiency, the 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. For companies of all shapes and sizes, the use of HEPA filters is not just critical but mandatory. Quality HEPA filters offer an efficient, effective way to trap and retain the smallest dust particles, down to and including 0.3 μm, helping to preserve air quality and protect workers. Manufacturers also have the option for an ULPA filter, which captures particles down to and including 0.12 μm. In order to prevent combustible dust from being exhausted back into the ambient air, the HEPA or ULPA filter should be positioned after the motor to properly filter the exhaust stream. The motor’s commutator and carbon brushes generate dust, and if the exhaust stream is not filtered that dust will simply be released back into the environment.
Spill response
Spill response should also be taken into account when purchasing an EXP. Although OSHA’s current audits are specifically looking at companies that handle dry solids, manufacturers’ maintenance plans are also under the microscope. If the user plans to collect flammable or explosive chemicals, a wet-model EXP is a viable option; these are also available in both electric and pneumatic versions.
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Conclusion
Picking the right vacuum often raises a lot of questions, especially when it comes to disaster prevention. Ask the vacuum manufacturer to do an on-site analysis of each operation’s vacuum needs in order to recommend the appropriate types of vacuum, hose, and accessories.
As displayed in one too many plants all across the U.S., the term “maintenance” oversimplifies the role an industrial vacuum system plays in today’s manufacturing processes. The right vacuum can save money, protect the integrity of the product, increase productivity, and most importantly, protect your most valuable asset, your employees.
Paul Miller is vice president and general manager at Nilfisk CFM in Malvern, PA (www.nilfiskcfm.com).
Guidance on dust explosion prevention
An ignitable material, an ignition source, and oxygen are all it takes for a potential explosion at a facility. Most manufacturing plants have all three. In 2006, fatalities involving explosions and fires increased by 26 percent 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, FM 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 at 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.
- Develop and implement a hazardous dust inspection, testing, housekeeping, and control program (preferably in writing with established frequency and methods).