Newsfront: Dust collection: Clean up your act

December 1, 2008 | By Joy LePree

When it comes to dust collection in the chemical process industries (CPI), there exists a wide variety of needs. For example, folks in dyes and pigments have a different set of dust collection challenges than those in the pharmaceutical industry, who have differing requirements from processors working with paints and varnishes. However, any and all chemical processors can boost process efficiency by updating old dust collectors with new, easier-to-service models.

"Dust collection, in general, is a grudge purchase," says Lee Morgan, president of Farr APC (Jonesboro, Ark.). "Chemical processors want to buy equipment that makes their product, not dust collectors. But, they need to be reminded that when done correctly, dust collection equipment offers one of the easiest ways to increase efficiency because it is often tied to all their primary pieces of production equipment."

This means that when the dust collection system is running poorly, the equipment it’s tied to will also run poorly and, when dust collectors perform optimally, so too will the related equipment.

Simplified serviceability

One way to ensure that the dust collection system is performing well is to make sure it’s being properly maintained. Realizing this, manufacturers of dust collectors and related air-management equipment are redesigning their products for simplified serviceability. The theory is that easier maintenance often results in a better bottom line due to increased uptime and productivity and reduced labor spending.

"People hate changing filters and doing other tasks associated with maintaining dust collection equipment," notes Morgan. "Our customers were asking for ways to change the filter without using hand knobs and wing knobs and without getting into the dust collector, so we designed the Gold Series to address those issues."

Farr’s Gold Series dust collectors feature a quick-open, heavy-gauge door that provides access to a simplified cartridge change-out system, which includes a Gold Cone cartridge with Cambar action that positively seals the cartridges without using threads or knobs, and does not require entry into the collector. The door is fully reversible for access from either side and has a lock-out feature for added worker safety.

In addition to simplified serviceability, the Gold Series provides efficient dust collection. The vertical design of the filter cartridges provides more efficient pulsing of dust, and a high-entry, cross-flow inlet eliminates upward velocities associated with traditional hopper inlets. The channel baffles installed in the inlet protect the filters from incoming dust and separate the larger particles directly into the hopper, reducing the load on the filters.

Also striving to make maintenance and filter changes easier, Precision AirConvey (Newark, Del.) offers the PAC Sonic Jet Dust Collector, with a low-maintenance, safety-first design that places all serviceable components on the outside of the casing to permit inspection, part replacement and other maintenance without requiring human entry inside the unit. The dust collector includes a front-loading filter-cartridge array that enables one person to perform filter inspection and replacement from outside the unit with no tools by simply sliding the cartridge in and out like a file drawer.

Similarly, the KleenFlo Series of collectors from Flex-Kleen (Glendale Heights, Ill.) offers simplified cartridge replacement. The unit is designed so that there is external access to the cartridges, which require no tools for replacement. In addition to the easy maintenance, the KleenFlo provides excellent dust collection. During normal operation, dirty air enters the top of the collector and moves downward through the filter cartridges, leaving dust on the outer surface of the cartridge element. Clean air exits through the center of the cartridge to the plenum and leaves the unit. Pulse-jet technology, controlled by a programmable timer, releases compressed air down the cartridge to release dirt, which falls off into the hopper below for removal.

Also looking to combine enhanced filtration with reduced maintenance effort and costs, Donaldson Torit (Minneapolis, Minn.) recently introduced the PowerCore dust collector with PowerCore filter packs (CE, October, p. 16). "The PowerCore, which we believe will eventually take the place of cartridge collectors and baghouses, is half the size of current traditional baghouse collectors. The size reduction provides a lot of savings because there is less metal, lower shipping costs, lower energy consumption and very large labor savings," says Petra Meinke, senior product manager, with Donaldson Torit.

Stand-alone PowerCore dust collectors are up to 50% smaller than traditional baghouses, and bin vent models are up to 70% smaller than traditional technology. The company says testing has shown that the units filter dust better, save space, allow point-of-use filtration and offer easy maintenance.

The PowerCore media technology is integral to the downsizing of the collector. At 7 in. tall, one PowerCore filter pack replaces six traditional 8-ft long, fabric filter bags. Instead of hours or days to remove the traditional filter bags, the Powercore filter packs are removed from the clean side of the collector with one hand in minutes without tools.

"We found that 80 baghouse bags can be replaced by 12 PowerCore filter packs. To change 80 bags can take 13 hours, but the 12 PowerCore filter packs took only 24 minutes to replace," says Meinke. "This will save a lot of time and money in related labor hours for our customers in chemical processing."

And, serviceability improvements aren’t limited to dust collectors. Companies such as Cyclonaire (York, Neb.) are working to simplify maintenance on equipment such as dust reclaim systems as well. While the intent of Cyclonaire’s Collect and Convey (C&C) Reclaim System was to preserve air quality and conserve material by capturing product dust from the silo-filling operation and automatically returning it directly to source silos, the design also saves time and labor because it provides convenient servicing at ground level. "Instead of having the traditional bin on top of the silo, we run the duct to the ground and transfer the dust collected back up to the silo," explains Joe Morris, vice president of sales and marketing with Cyclonaire. "The system is also automated, so if there’s a problem, not only is it easy to pinpoint, but maintenance will be more attentive to the problem since the unit can be serviced from the ground."

Airlanco (Falls City, Neb.) is working on its filtration units. The company’s Pulse Jet Filter has no moving parts to wear out and offers a compact, modular design to simplify maintenance. The Pulse Jet Filter comes in a variety of shapes, sizes and filter bag layouts to fit multiple applications. But, the cleaning cycle is the same throughout the line: Dust-laden air or gas enters the unit through a hopper inlet where it is directed toward a deflector that slows the airflow and causes heavier particles to fall directly into the hopper. Lighter, airborne particles follow the air stream into the filter area and collect on the outside surface of the bag filters. The filtered air then flows into the clean air plenum and exits the unit. Sequential signals from a timer open valves, allowing short bursts of compressed air to reverse the airflow in each row of bags. This dislodges the surface dust from the bags so that it falls into the hopper. The angled hopper also helps funnel the dust and debris to the airlock, simplifying disposal, as well.

Filter manufacturers, like Midwesco Filter Resources (Winchester, Va.), are also working on their end to simplify maintenance. The company now offers a bottom-load baghouse element, the Seal-Tite II, which is reputed to be an easy-to-install, bottom-load filter with a proprietary installation and sealing design that provides significant labor cost savings. The new intricate retainer clamp combined with the Super-Bead sealing design makes it almost impossible to incorrectly install the element, providing a virtually leak-proof seal and reducing downtime and maintenance costs. Other benefits include operating efficiencies to 99.99%, lower element operating pressure drop, prolonged filter life due to washable filter designs and reduced product retention due to surface filtration.

Advanced automation

The addition of automated monitoring is another way of ensuring that needed maintenance occurs in an effort to keep dust collectors running smoothly, according to T.J. Winalski, product manager with FilterSense (Beverly, Mass.). "Historically, maintenance on dust collection equipment has been ignored until it becomes a major issue that affects production, so we began to supply particulate emissions monitoring and baghouse controls," he explains. "By installing reliable instrumentation, processors not only keep abreast of baghouse performance, but tend to see process efficiency improvements, as well."

This occurs, he says, because if there’s a broken bag on an unmonitored baghouse, it tends to go unnoticed. Early on, product goes out the stack and is wasted, and as the problem grows worse, it eventually necessitates a major repair. But the monitors allow customers to find very small problems inside the baghouse and perform proactive, rather than reactive, maintenance. "They can fix a small problem according to schedule, rather than being forced to shut down the whole operation when it becomes a big problem," notes Winalski. This results in less downtime and less maintenance hours because it’s easier to fix a small tear in one bag than it is to replace four broken bags."

To provide reliable instrumentation, FilterSense has introduced its Self-Validating Particulate Sensor, which offers continuous, particulate-emission monitoring and filter leak detection incorporated with automatic zero and span for self validation. Self validation, combined with induction-sensing and protected-probe technologies, is said to provide enhanced reliability and lower instrument-maintenance costs over older opacity and triboelectric technology, especially in applications such as pharmaceutical spray dryers, cement, carbon black and other chemical processes.

FilterSense’s B-PAC MICS Series of Baghouse Diagnostic Controllers integrates intelligent filter cleaning, pressure control, particulate monitoring and auxiliary sensing into a single system. The benefits here include reduced maintenance costs, energy savings and maximum product recovery.

Reaching for compliance

Equipment such as FilterSense’s instruments are also helpful in meeting U.S. Environmental Protection Agency (EPA; Washington, D.C.) MACT, Title V and other compliance regulations.

However, one of the hottest regulatory topics in dust collection is the recent NFPA (National Fire Prevention Assn., (Quincy, Mass.; www.nfpa.org) revision to its guidelines, which now requires compliance on issues such as rupture vent designs and location of enclosures, including dust collectors that handle explosive or combustible dusts, gases and mists. NFPA-68 now places a greater emphasis on total plant safety in areas where explosions could occur. The requirements of this revision must be incorporated in all, new baghouse collectors and may have to be retrofitted into some existing baghouse collectors.

"The new NFPA guidelines for explosion venting is upon everyone’s mind these days because it became a law versus a guideline almost overnight following a recent expolsion," says Ron Krebs, president of Airlanco. "This is a big topic for discussion among dust collector manufacturers and chemical processors. Processors need to know how to meet those guidelines and be sure they are installing or updating equipment that helps them do that."

While many equipment manufacturers are already providing equipment that complies with NFPA-68, some are taking it a step further. "To help our customers comply with the new rule, we will be offering them a free evaluation of their current system to determine if they need to upgrade or modify their current installations," says Arun Govil, president of Cemtrex, Inc., parent company of Griffin Filters (Farmingdale, N.Y.). "We have made great improvements to our product line and address really important issues for our customers and their plant safety."