The Importance of Dust Control

Here are a couple or articles on the importance of dust control. Enjoy the read and have a great day!


7 Ways Dust Control Improves Composite Manufacturing Operations


“For composite manufacturers, dust is a constant. Whether you make aircraft wings, car fenders, or tennis rackets, chances are if you look around your facility, you’ll see plenty of dust.

Because it’s everywhere, dust can affect many different aspects of your operations, especially if it’s not properly controlled. In that way, controlling your dust is like properly hydrating your body. If you’re hydrated, all of your body systems can function at their peak. If you’re dehydrated, your other systems won’t work well at all.

Let’s look at seven ways dust control can improve your composite manufacturing operations across the board.

1. Reduced risk of cross-contamination
Composites manufacturing is highly sensitive to contamination. Dust that becomes airborne can travel to and interfere with other processes and products. This can quickly increase the size of your scrap pile. By controlling dust at the source, you can ensure that it doesn’t affect what’s happening in other areas of your plant.

2. Improved product quality
In addition to contaminating processes and products, dust also has an immediate and negative impact on how your equipment functions. Dust control will help you keep your equipment working in top shape, which means your products will continue to reflect the quality your company is known for providing.

3. Lower equipment maintenance costs
Over time, if dust is allowed to accumulate, it can cause wear and tear on your equipment. This not only affects product quality, but also increases the cost of maintaining your equipment.

4. Less downtime due to equipment breakdowns
In the worst case scenario, dust accumulation can cause your equipment to break down entirely. This means not only emergency maintenance, which is much more expensive than scheduled maintenance, but you might have to replace the equipment entirely. And, of course, if your equipment breaks down, your production line has to stop, and every minute of downtime equals a dip in your bottom line.

5. Improved compliance
Pretty much all dust in composites manufacturing facilities is combustible. And composites manufacturers are being targeted by OSHA for dust-related violations. By implementing OSHA’s recommended methods for dust control, you can keep your company on your inspector’s good side.

Composites manufacturers also need to be aware of OSHA’s new final rule on exposure to silica dust. Many composite raw materials and molded products contain silica, which can have long-term adverse effects on health. The American Composites Manufacturers Association (ACMA) has published a study to help composites manufacturers comply with OSHA requirements. Learn more from Industrial Equipment News and on the ACMA website.

6. Reduced risk of a dust-related fire or explosion
Of course, the main reason to comply with dust standards isn’t just to avoid OSHA penalties. It’s to ensure your entire operation doesn’t go up in smoke. Keeping your dust level below the recommended threshold is the best way to protect your facility against dust-related fires and explosions.

7. Improved worker health and safety
Fires, explosions, and silica are just a few of the dust-related risks to worker health. Many composite manufacturing processes produce other particles small enough to be respirable. Certain types of dust are also slippery, which can lead to falls. Overall, a clean facility is a safe and healthy facility.”


Dust Collection: Expense or Investment?

BY – Karen Wood

Composites World 

Well-engineered dust control systems not only improve shop air quality but also boost productivity, prolong machine life and save energy.

Fifteen years ago, dust management in composites manufacturing operations was somewhat unsophisticated. A common solution to the dust generated by cutting, trimming, sanding and grinding was to cut a hole in the shop wall and install an exhaust fan. Although simple and relatively inexpensive, this method did little but improve visibility. Today, governments mandate particulate emission control, both inside and outside the plant. Respirable dust, which is classified as less than or equal to 5 µm in diameter, is small enough to penetrate deep into the lungs, with serious health consequences. But the cost of uncontrolled dust goes beyond worker health. Inhalable dust, which averages 10 µm in diameter, not only can get trapped in the nose, throat, and upper respiratory tract and irritate eyes and skin, but it also can build up on machinery components, causing premature wear. Moreover, dust can impact product quality as well. In this respect, says Ken Abbott, managing member of Envirosystems LLC (Tucson, Ariz.), “the composites industry is unique. It’s very sophisticated in terms of materials and techniques, and with that sophistication comes an increased sensitivity to contamination.” If allowed to float freely through the air, dust from carbon fiber, for example, can corrode surrounding aluminum components, and a small amount of any contaminant on a faying surface can interfere with adhesion in bonded part assemblies. As a result, the industry’s overall perception of dust control has begun to change.

“Long perceived as simply a cost of doing business, companies are now realizing that dust collection equipment — when done right — can be an investment,” says Abbot. “Our customers expect dust collection to help improve product quality, reduce scrap due to contaminated parts, lower housekeeping and equipment maintenance costs, and boost worker productivity.”

Managing particulate as minute as one-twelfth the width of a human hair is challenging: The U.S. Occupational Safety and Health Admin. (OSHA), for example, requires that worker exposure levels for respirable dust be limited to just 5 mg/m³ averaged over an eight-hour period. Without dust control, “most people using a sander or grinder will quickly exceed the OSHA level,” says D. Scott McConnell, vice president, Dustcontrol Inc. (Wilmington, N.C.). The key is to investment in what dust control system designers call an engineered solution.

Today, dust control systems are rarely off-the-shelf products. Instead, each is customized to meet the requirements of the customer’s application, and there are many variations from which to choose. While a well-designed system can have a positive affect on the bottom line, the opposite also is true: “You can put an inexpensive system together and collect dust with it, but if it is not done correctly, it can be very expensive to operate,” warns Abbott. System design involves consideration of factors that impact the effectiveness of dust containment technology, including the dust collection method and vacuum systems (fan size, motor power rating and filter media) — the selection of which depends on careful calculation of application-specific process variables, such as air volume, capture velocity and static pressure.

One of the most important variables in dust control system design is air volume. To determine the air volume required for a particular application, the width of the space to be controlled is multiplied by the height, resulting in a room cross-section value expressed in square feet (ft²). This cross-sectional area is multiplied by the required speed of air movement through the room in feet per minute (fpm) to calculate air volume, as expressed in cubic feet per minute (cfm). Therefore, airflow speed of 50 fpm in a room that measures 40 ft wide by 10 ft high (12m by 3m) would require fan volume of 20,000 cfm.

When selecting a fan, says Abbott, “static pressure will determine whether or not the fan will perform the function for which it was chosen.” Static pressure (SP) — or resistance to airflow — essentially rates how much resistance to airflow can be introduced (by dust buildup, filter media and/or ductwork, for example) without affecting the air volume rating. “Using a fan with the incorrect SP rating will result in a system that, at best, will cost more than it should to operate or, at worst, won’t be able to do the job at all,” says Abbott.

“As an example, a fan with a rating of 10,000 cfm at 0.75-inch SP may only use a 5-hp motor to effectively move air, at that static pressure, through a paint booth or other type of low-resistance system,” says Abbott. If this same fan and paint booth were used to collect dust, however, “the fan will be all but useless before dust is even collected because a new filter provides 0.75-inch SP right out of the box,” he contends, noting that “a 10,000-cfm fan suitable for a typical dust collection system will need to achieve its full rated volume at a resistance closer to 3 inches SP or more to be effective and would require 10 hp or more.”

A large factor that affects system design is the size of ductwork that might be required to transport dust from the source to its collection point. Duct size in cross-section directly affects system performance and is based on what particulate will be collected and the volume of air that must be moved. According to Donaldson Torit (Minneapolis, Minn.), which offers cartridge- and bag-type dust collectors, ductwork that’s too small tends to restrict airflow, resulting in pressure loss. This reduces the air volume and increases energy use. If the ducts are too large compared to the air volume, air velocity is reduced. Dust capture will be poor and dust will not be pulled through the ductwork.

A key to system efficiency, then, is to minimize static pressure. Assuming an average cost of industrial power of approximately $0.08 (USD) per kilowatt hour (KwH), operating one 5-hp fan for a single shift, five days a week, for 52 weeks would cost $805 per year. If, due to ducting or other installation requirements, the fan needs 30 hp to move the same air volume, the cost would be $4,238 per year. “The most cost-effective method of eliminating airborne contamination is to confine it to one area where it can be isolated and filtered using the least amount of air,” says Abbott. Strategies include locating the dust collector as close as possible to the area it is filtering to reduce ductwork and, therefore, the fan’s horsepower requirement. Whenever possible, the filtered air should be exhausted back into the plant to retain conditioned air — heated air in the winter or chilled air in the summer — to minimize building heating and cooling costs.

Given these design constraints, dust control system manufacturers have developed three basic collection strategies: whole-room, containment booth and source-point capture. Strategy selection is based on the size, type and number of the customer’s dust-generating machines.

Whole-room systems are often the only practical option when an individual piece of equipment is massive, such as a gantry-style CNC router. The whole-room approach typically involves a room built around a machine to reduce noise and dust. The dust collector, which can be located outside the building or inside, pulls air from the work area into an inlet device — typically mounted along the wall at the narrow end of the room. The air is directed through filter media where contaminants are trapped and clean air is exhausted back into the work area or outside the building. These systems can involve extensive ductwork or, in some cases, be free of ductwork.

Envirosystems’ trademarked AirWall dust collection equipment, for example, is self-contained, eliminating the need for ductwork and greatly reducing static pressure. “By saving 2 to 3 inches in static pressure with no ductwork, we can move the same amount of air with a 5-hp fan as a ducted system [can move] with a 40-hp fan,” Abbott claims.

The system reportedly removes more than 99.99 percent of airborne sub-micron particles (down to 0.5 micron in size), which surpasses current OSHA requirements. A high-velocity, reverse pulse-jet cleaning system automatically cleans cartridge filters (see “Filtration Facts” at the end of this article, on p. 3).

Given a room size of 20-ft by 30-ft by 10-ft (6.1m by 9.1m by 3m), a complete air change every minute would require air to be pulled through the room at 30 fpm and could demand a fan volume as high as 6,000 cfm in a ducted system. In a duct-free system, the same air volume reportedly can be achieved with a 5-hp fan. The average cost of the duct-free system would be about $15,000.

Where room size is larger than the dust-generating machinery, the latter can be located within a contamination control booth (CCB), a three-sided, ceilinged structure with integral lighting, open on the fourth side for easy access. “Booth sizes can be as small as 10-ft by 10-ft or as large as 130-ft by 50-ft [39.6m by 15.2m],” explains Ronnie Frees, president of Frees Inc. (Shreveport, La.). “Tub and shower manufacturing operations, for instance, typically require 40-ft by 40-ft [12.2m by 12.2m] containment rooms.”

An exhaust fan with relatively high airflow, typically in the 140 fpm to 160 fpm range, draws air out of the CCB, creating negative pressure within the CCB that draws air into the booth’s open end, preventing dust from escaping. A grinding booth for two to four workers measuring 22 ft wide by 7.5 ft high by 8 ft deep (6.7m by 2.3m by 2.4m) would require a 20-hp to 30-hp fan motor to pull the 160 fpm necessary to generate an air velocity of 22,000 cfm. The system would cost approximately $36,000.

Frees and other companies offer an additional “air curtain” feature that can be adapted to both large CCBs and room-size exhaust systems. A blower system is positioned at the front edges of the open booth or on the side opposite the collectors in room-size applications (see photo, this page). These blowers generate a high-velocity positive airflow angled toward the collectors to reinforce transport velocity within the booth.

To create its air curtain, Frees’ trademarked Dust-Free system uses a “push-pull” recirculation method. An exhaust fan draws dust into a dust-separation chamber at the back of the CCB where a filter tube sheet traps up to 99 percent of the airborne dust particles. The clean air then is channeled through ductwork to the open end of the chamber where it provides positive airflow, pushing the air inside the room back toward the dust collector inlet. The system uses digital direct control (DDC) to save energy. “When workers are in the containment area working, the system is on, and when they stop working, the system will gradually slow down until it is off or nearly off,” says Frees.

The source-point capture strategy can take several forms and becomes a practical option when the dust source can be localized and is especially useful when large volumes of dust are being generated by one source. “The source-point capture system offers advantages for operations where there are many different machines operating in a large space with no way to effectively group and enclose them for effective dust control,” says Abbott.

For stationary equipment — both large and small — source-point capture can be accomplished via an overhead or side-draft hood. For handheld tools, there are two options: The down draft table, which draws dust down through a perforated tabletop, does not impair tool use, but it is best used with smaller parts because large parts can block airflow and create pockets of dust-filled air. Capture also can be accomplished by affixing a suction casing, or shroud, and vacuum hose as near as possible to the dust-generating portion of the tool. (See photos, this page) Ductwork, typically located overhead, connects the dust collection unit to suction outlets from which individual hoses can be dropped down to the work area. Usually located near or along compressed air “drops,” hoses are typically looped with and run parallel to the pneumatic airline or electrical power cord for easy handling. Automatic valves can be used so that suction only occurs when the tool is actually in use.

A typical source-point capture system designed with four drops to accommodate two to four workers operating vacuum-assisted, heavy-duty sanders, for example, would require a 10-hp turbo pump and cost approximately $18,000.”

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