The Coleman Tool & Manufacturing Co. in Union Grove, Wis., had one goal when it installed new air curtains - to save on monthly winter heating costs.
Such costs are not insignificant in a cold weather, upper-Midwest state like Wisconsin. To the company’s surprise, the curtains had another effect: Not only were they saving energy, but filtering the welding smoke and improving indoor air quality in the facility.
“We hit two birds with one stone,” said Michael Coleman, president of Coleman Tool.
Industrial plants have used air curtains above open doorways for decades to save energy and keep cool or warm air out. Coleman, a welding, machining and metal fabrication company that specializes in replacement parts for waste disposal vehicles, specified air curtains for its new 60,000-square-foot plant. An in-house mechanical engineering team, which performed much of the building’s mechanical requirements, wanted air curtains for two 16-foot by 16-foot overhead doors, and one 12-foot by 12-foot overhead door.
Coleman Tool now uses one CFA and two CFC model air curtains manufactured by Berner International. The air curtains retain heat while the doors are open at a significant energy savings. Consequently, the building now maintains a 60°F plant wintertime temperature generated purely from the waste heat of its industrial welding process production.
The former Coleman Tool building didn’t have air curtains. The company used supplemental heaters, kept the shipping doors open more frequently, and used exhaust fans to expel welding smoke. Unfortunately, wintertime heat was exhausted, too. However, the new building now incurs no supplemental winter heating costs, significantly reduces heat loss during open-door periods, and re-circulates heated air through the air curtains, all which contribute to the company’s ongoing green mission, according to Paul Bugner, head of maintenance.
The air curtains, which are activated manually or with a switch triggered by a door opening, help maintain the temperature because they eliminate outdoor air infiltration. Air curtain technology draws interior air from the facility and discharges it through field-adjustable linear nozzles to produce a smooth airstream that meets the floor approximately where the door opens.
Temperature differences and prevailing wind conditions cause the majority energy loss from open doors. An air curtain can contain approximately 70 percent to 80 percent of indoor air and return it to the space. Because the air curtain discharges at velocities generally in the range from 3,000 to 6,500 feet per minute, the strong airstream shield also prevents insect infiltration.
To continually protect the door opening from these exterior forces, Berner factory-engineered the air curtains for size, air volume flow rate, airstream velocity and discharge nozzle uniformity, which is critical to air curtain performance, officials said. Performance levels are certified by the Air Movement & Control Association.
Smoked outWhile Coleman Tool was racking up energy savings with the air curtains, the lack of air infiltration and cross-ventilation during the winter had affected IAQ. To control smoke and other airborne contaminants generated by Coleman Tools’ 10 Miller Electric welding bays and four IGM Robotic Systems stations, mechanical engineers specified 14 Industrial Maid industrial air-filter walls that surround the 15,000-square-foot welding area.
Despite the efficacy of the air cleaners, an estimated 20 percent of the smoke still rose up and out of the welding area, creating a haze throughout the plant. Energy savings were important, but not at the expense of air quality, Coleman representatives said.
One expensive solution proposed adding tens of thousands of dollars worth of rooftop makeup-air equipment to re-circulate the heated air. Instead, Bugner thought that the air curtains might serve a dual duty as air cleaners as well as energy savers. The high 16-foot height above the doorways helped the air curtains draw in the lofty haze.
Some air curtain manufacturers offer options for conventional filtration add-ons; however Bugner said he felt heavy industrial welding smoke would need a filter holder designed for quick and frequent replacements to keep labor expenses in check. Also, most conventional fiber filters carry a minimum efficiency rating value of one to six, while welding smoke and particulates would need at least a MERV-8 filter - the same rating as the filters used in the welding area air cleaners.
“We designed a filter holder we could manufacturer ourselves, required only 10 minutes or less to replace, was aesthetic, didn’t affect the air curtain’s airflow and would use inexpensive off-the-shelf filters,” said Coleman, who has since applied for patents on the filter design to market it to industrial air curtain users needing heavy duty filtration.
Fine tuningBugner experimented with different combinations of inexpensive filter media and filter holder styles to further reduce maintenance costs. Since a 24-inch by 24-inch filter is a standard off-the-shelf size, the steel filter holder was made to allow eight pleated fiber filters for the two 16-foot-wide air curtains (six for the 12-foot-wide air curtain) to be slid into either end in 10 minutes or less.
The filter holder’s metal fabrication was designed to be lightweight and rigid. It also featured an attractive safety grille to prevent larger items such as hands from entering the filter.
The air quality improvements have been significant: The haze is gone, the production floor’s air smells fresh, and the plant’s chronic asthma sufferers noticed significant breathing improvements, Bugner said.
Coleman executives said they now believe all industrial buildings should be outfitted with air curtains.
“In our case we had to have air curtains to save energy, so the fact they also boost IAQ is a bonus that carries virtually little additional cost,” Bugner said. “Anyone that thinks they have a clean environment should put up an air curtain with a filter. They’ll find out the air isn’t as clean as they thought.”
This article and its images were supplied by Berner International.