Bag House's Efficiency Leads to Cost Savings.

Investment in dust collection system pays off for millwork firm.

WHEN BRUCE WHISENHUNT moved his woodworking operation, Diversified Millwork, into a 45,000-square-foot plant in Aurora, CO, he also added a high-volume baghouse dust collection system that is so efficient its $2-a-year operating permit is the lowest in the state.

"At our former location we had a traditional cyclone dust collector and paid $2,000 a year for our permit," Whisenhunt says. In moving into the expanded facility in 1997, Whisenhunt overcame the potential environmental problems associated with dust collection by installing a high-capacity Torit RF baghouse. The baghouse captures, filters and recycles air throughout all stages of dust collection, right down to the final bin collection where a closed-loop material handling system helps to prevent measurable dust from being released into the atmosphere.

"State inspectors frequently come to check and monitor our system and we al ways get accolades from them," Whisenhunt says. "We're pleased that the dust collection system meets the strict requirements of the inner city."

80 Tons a Month

Whisenhunt purchased Diversified Millwork in 1992. As business grew for the company's mix of mouldings, millwork, furniture parts and wood flooring, it became imperative that it gain more leg room for its 32 employees and equipment.

Whisenhunt purchased a 6.5-acre site in Aurora, a suburb of Denver. Before constructing the new building, much thought was given to plant layout to maximize product flow and dust collection efficiency.

Mel Zeman of Airpro Inc., a Denver based specialist in air cleaning and dust collection systems, helped specify a system meeting the requirements of the new facility, double the size of the one it replaced. Equipment, including two Weinig six-head moulders, two Pinhiero ripsaws, a Steiner resaw and a Pinhiero planer generates 80 tons of sawdust each month. Most of it is oak, though the company also uses maple, cherry, ash, walnut and hickory in its products.

Dust Collector Particulars

The features of the 17,000-cifm baghouse allow the plant to operate efficiently and effectively. Cyclonic airflow separates dust particles, and a uniform airflow design delivers constant airflow that reduces wear and tear on the filter bags. A medium pressure, positive displacement pump (71/2- psi) eliminates the need for using compressed air to clean the filters.

Also important to Diversified Millworks' operation is the baghouse's self-cleaning system. Torit's Reliable Fire cleaning system cleans each filter bag every 4 minutes, reducing the need for filter bag changes and providing continuous duty operation.

In addition to these basic features, the flexibility of the RF baghouse allowed Whisenhunt to fine-tune the system to meet his specific application. To increase the life of the 16-ounce polyester filter bags, the entire system is purged twice a week during plant downtime. The same purging operation that cleans the filters regularly during plant operation blows reverse air through the filters, removing more dirt off the filters and ensuring more efficient operation. Three years after being built, the plant still uses the original filter bags.

A second portion of the system is the closed-loop material handling system used to transport dust from the collective hopper and rotary valve. A blower system under the collector transports captured dust into a large collecting bin. Clean air from this vented process is recycled back to the plant so that no dust is emitted into the atmosphere.

"Because this is now an automatic process, nobody has to touch it, which was a problem with the previous collectors," Zeman says. "A key to the success of the closed-loop system is the clamping duct work, which contains the dust as it's transported from the collector to the bin."

The combination of efficient baghouse and closed-loop material handling system means that no measurable dust is emitted from the collector, resulting in the low-cost operating permit. "It's worked out much better than we envisioned," Whisenhunt says.