Irony, it seems, has a sense of humor. A leading manufacturer of HVAC filtration products for residential, commercial/industrial, and HEPA applications was having problems with (of all things) the air quality in its largest manufacturing facility. This particular production plant in the southeastern United States manufactures more than 30 million fiberglass furnace filters every year, including the standard 1 in. filter that you probably have in your own furnace at home.

The manufacturing process used to produce these filters creates a thick haze of fiberglass particulate matter in the atmosphere of the plant. The dust is created at two specific spots in the production chain; first, where the fiberglass rolls are cut into lengths and the glass is actually broken; and second, at a carousel where the fiberglass media is inserted into a cardboard frame. Once a filter is complete, it is ejected off the carousel by a powerful blast of compressed air, which in turn launches fiberglass dust into the work atmosphere. (Photo shows fiberglass cutting station as well as custom hood system at the point of media insertion; system is built to maximize efficiency with minimal use of floor space.)

The plant includes seven filter-manufacturing lines, each with its own cutter and carousel. Although the facility occupies more than 260,000 sq ft, the seven manufacturing lines are located next to one another in one small area.

The 200 plant employees were accustomed to working in a haze of fiberglass particulate matter. Although it posed no serious health threat, it had a large irritant factor, with dust settling on clothes and hair -- and despite the use of safety goggles and glasses, in employees' eyes. In fact, one third-shift employee's full-time job was to sweep up all the dust from the previous day's work.

"When the sunlight came through the window at a certain angle, all you would see was a thick blue haze," said Mark Gerken, engineering manger at United Air Specialists (UAS) Inc, a manufacturer of industrial air cleaning equipment.

The filter company tried a variety of different solutions, including local exhausts, misting fans (to weigh down the dust and keep it out of the air), wash stations, all in addition to protective eyewear.

Until now, all attempts for a solution were unsatisfactory.

"It was just a nuisance for employees," said the plant manager. "Nearly every day, someone would require medical attention because of dust in their eye. That's $40 to $50 an incident, plus the lost time. We really wanted to solve this problem."

Finding the Right Solution

After observing and doing some research, the United Air Specialists engineering team recommended the BDC 22T dust collector. The unique BDC is a compact, self-cleaning, continuous-duty system that uses a pulse-jet cleaning system to effectively "pulse off" captured dust and clean the filter while the system stays on-line.

Extremely versatile, Series BDC has many media filter options, including cartridges, pleated bags, and felted bags. For this particular plant, the UAS team recommended 2 in., 16 oz polyester felted bags, believing they were best suited to capture the fiberglass dust. The 2 in. felted bags offer the best durability and highest-filtration efficiency.

The biggest challenge for UAS engineers was the carousel where the fiberglass filter is inserted into the cardboard frame. It emitted large quantities of fiberglass dust in the air and was the main source of the blue haze. The fiberglass cutter was slightly less of a problem. It also created dust, but it mostly fell to the floor, where it was tracked around the plant -- an added irritant.

Customization

UAS' standard hood designs were not capable of capturing the quantity of dust generated by the carousel. So UAS engineers custom designed and built a bigger, more complex hood. The first part of the hood is like a tunnel; the last half has the bottom removed so that the completed filters will fall onto the conveyor.

This installation required several other special features. Height restrictions allowed the unit to be only 11 ft tall, so UAS recommended a short 30 gal discharge drum rather than the taller 55 gal drum. Additionally, the unit was fully equipped with a direct-drive blower and a silencer for worker comfort.

UAS also supplied motor starter panels and a separate digital pressure and pulse control panel, which help govern and monitor the self-cleaning system. Pulse cleaning systems can be set up to offer several different cleaning modes, including continuous, on-demand, at set points, and during downtime. The gauge on the control panel indicates the dust loading condition of the cartridge filters, while the circuit panel activates continuous pulse cleaning. Users can adjust a switch inside the Pulse Control Panel to activate a downtime-cleaning mode upon system shutdown, as well as program pulse cleaning sequences as required.

For those who prefer on-demand cleaning, UAS also offers a Photohelic gauge option. In addition to continuous and downtime pulse cleaning, on-demand cleaning gives operators the flexibility to manually set the high and low points at which the unit pulses. This prolongs filter life, maximizes the efficiency of the dust collector, and saves money by conserving compressed air.

For this filter manufacturing application, UAS set up the units to pulse on demand. This means that when the pressure drop across the filters rises to a certain point the cleaning would initiate until the pressure was reduced below the set point. In addition to the cleaning on demand, the units were set up to perform downtime cleaning. This means that when the units were shut down the unit would go through two cycles of cleaning with the blower off. This is when you get the most out of the cleaning system because it is not fighting against the blowers' resistance. (Shown here, the custom hood designed for this application.)

UAS tested just one unit at first, with a hood over only the carousel and not the cutter. The system shipped in August 2004, and installation was completed in less than a month. The plant monitored results over the next several months, and the results were dramatic -- the BDC was clearly capturing a great deal of fiberglass dust. So the company made the decision to complete the installation and purchase six more units for their other six lines.

Easy Routine Maintenance

Any dust collection system will require fine-tuning and maintenance specific to the installation. That's why the BDC collector was engineered for fast, tool-free, safe maintenance and filter change-out. Instead of systems that require workers to crawl inside the unit (a practice that is slow, dirty, and dangerous), the BDC's filters can be removed quickly by unlocking the cam bar and simply sliding the filter trays out. This ensures worker safety and greatly reduces routine service time. Since the BDC system operates automatically and with continuous duty, the BDC requires little maintenance.

"This system is very easy to maintain," says the plant manager.

The final installation was completed in February 2005, and Gerken visited the plant in April to check on the installation, make adjustments, and fine-tune the maintenance. Two results have become immediately apparent: "The blue haze was completely gone," reports Gerken. Even more important, eye injuries -- which had been a near-daily occurrence -- have dropped to near zero. There have been only a handful of reportable eye injuries since the installation.

The plant reports another benefit as well. The third-shift employee charged with sweeping up the previous day's dust . . . well, he has been reassigned to another job.