|One of nine, 20-ft.-diameter, slow-speed cooling fans Plasti-Line, Inc., installed at its 82,500-sq.-ft. facility in Columbia, SC.|
Rather than rely on personal air-circulation fans, the company chose large, 20-ft. diameter slow-moving fans from the HVLS Fan Co., Lexington, KY. Nine of these fans were able to provide significant air movement both to workers at individual workstations and to workers whose jobs took them throughout the facility. The installation of these fans measurably improved the thermal comfort conditions within the entire plant were.
Plasti-Line's manufacturing processes involve "thermo-forming" or "vacuum-forming," whereby plastic sheets are put onto mold. A vacuum is applied, and the sheets are baked at 325 to 350 degrees F. The ovens that bake the plastic sheets are open to the manufacturing floor. Curing ovens are also used that generate temperatures up to 175 degrees, and the company uses MIG and TIG welding in constructing sign frames. All of these processes create a sizeable internal heat load.
Plasti-Line discovered it had a cooling problem soon after opening its brand-new, 82,500-sq.-ft. facility in Columbia. When summer arrived and temperatures inside the plant topped 110 degrees F, the company knew something had to be done. Summer working conditions were so uncomfortable that employees were given an additional break each day to cool down. With 100 employees, the 10-minute break amounted to nearly 17 hours of lost production time each day. Even seasoned workers in the plant had problems dealing with the heat Some required medical attention from heat stress symptoms.
Creating a more comfortable plant environment naturally included consideration of air conditioning, "But it wasn't in the cards," says Michael Smith, manufacturing engineer at Plasti-Line. "We wanted to stay within a budget and air conditioning was too expensive on both the installation and operating levels." Moreover, air conditioning wasn't feasible because Plasti-Line had several bay doors that were kept open all the time.
Smith says he recognized that the solution to the problem required improving the airflow within the plant. "The ventilation system that was in place [a ridge-mounted vent spanning the length of the building and eight supply fans] did not move a sufficient amount of air at the floor level where the employees were working."
When ambient daytime temperatures regularly exceeding 100 degrees F, Smith realized he could turn the air over inside the building an infinite number of times without making employees feel any cooler. What was needed was a flow of air that could simulate the natural cooling effect of an outdoor breeze. Small pedestal and column-mounted fans were an option. However, with small fans, Smith would have to purchase and install a separate fan for each workstation. With 100 employees, this would be no small expense, not to mention the maintenance required for that number of units. Also, workers were not always stationary. They would only feel relief when standing directly in front of the fans.
The ideal cooling solution would circulate as much air as possible to as many workers as possible, preferably with as few fans as possible. This solution was available in the form of large-diameter, high-volume, low-speed ceiling fans. The HVLS fans the company chose use 10 hollow-core extruded aluminum blades. They can be made in 4-ft. to 12-ft. lengths, creating fans that range in size from 8 ft. to 24 ft. in diameter. Unlike a high-velocity fan, which moves a lot of air by rotating quickly and repeatedly stirring a small amount of air, an HVLS fan moves a lot of air by moving a very large column of air very slowly, at about 3 mph. It can move from 15,000 cfm (8-ft. diameter fan) to 122,000 cfm (24-ft. diameter fan) of air, and will cover an unobstructed area of up to 20,000 sq. ft. with no significant reduction in the air velocity at the outer perimeter of the column of air. The effect throughout the area of coverage is a gentle breeze.
Plasti-Line installed nine 20-ft.-diameter HVLS fans. The final cost amounted to less than the company's estimate for air conditioning an area comprising less than 20% of the total manufacturing area. It was slightly more than twice the cost of the production time lost by the additional daily 10-minute breaks. Not only were the fans less expensive than air conditioning, the operating cost of each is less than 50 cents per day, a fraction of the operating costs of air conditioning.
"We have been extremely pleased with the fans," says Smith. "They run continuously and provide a flow of air that can be felt throughout the entire manufacturing area. What's more, all employees within the area are provided the same level of comfort, regardless of where they are working."
HVLS Fan Co., 133-T Trade St., Lexington, KY 40575; 859-233-1271.