Originally published in Refrigerated & Frozen Foods, February 2002

Air of Success
Air-curtain doorways give CSI freedom from ice buildup, collisions and other problems.

When CS Integrated LLC (CSI) got tired of frost buildup, accidents and other problems with its freezer doors, it gave them the air. As in air-curtain doors from HCR Inc. CSI, a public refrigerated storage company with 30 U.S. locations, was having trouble getting its doors to work properly in high-traffic distribution centers. The high-speed rollup doors just couldn’t cope with the passage of up to 25 forklifts an hour.

"We had tried a number of other doors, including high-speed doors, but we could never get them to work," says John Aviles, CSI’s vice president of engineering. "The doors would get warped – there was a lot of maintenance and frosting associated with them."

The problems stemmed from the difference in temperature between the loading docks and the freezers. The docks could range from 60°F to 35°F while the freezers were at –10°F to –15°F. That led inevitably to ice buildup on the floors and door jambs.

"The doors that were out there just didn’t work properly, either because of the cold or because of the pressure differential," Aviles says. "They wouldn’t seal up properly. The deciding factor for us was mostly to find a solution to get something that would prevent the frost buildup inside the freezers and around the doorways, which was a significant safety hazard for us."

Chipping away the ice sometimes damaged the concrete floors. Another problem was that standard freezer doors often didn’t open properly, due to icing or to problems with the controls. That made them liable to be hit by forklifts.

About four years ago, CSI installed air-curtain doors from HCR Inc. Lewistown, Mont. These doors literally create an air-based barrier by continually blowing a sheet of air across the freezer doorway. The company’s name comes from characteristics of this curtain: a Horizontally directed air stream that travels in a Curvilinear path and is Re-circulatory. The first installation came at a warehouse in Hopkins, Minn. Since then, eight more CSI warehouses across the country have installed at least one HCR door – some have up to four.

The model CSI chose is the ECAV, which features a pair of fringed vinyl curtains about 18 inches apart. The curtains retract when infrared motion sensors detect an approaching forklift. CSI chose the ECAV because the vinyl strips add to the strength of the barrier between the freezer and the dock.

The amount of traffic was the deciding factor in determining whether an HCR door would be cost-effective in a given installation, Aviles says.

"In what we consider our low-volume warehouses where the door traffic was a lot more controlled, we didn’t see the need to change those doors to an HCR door," he says. "Where we did was where we have what we consider our distribution sites, where we have a lot more traffic through those doors on a consistent basis."

The ECAV model uses a physical barrier – the vinyl strips – in addition to the air curtain, but this does not present the same problems as a solid door. The mechanism that opens the strips is mounted at the top of the doorway, making it almost impossible to hit with a forklift.

That mechanism, besides being safer from accidents, is just generally more reliable than most ordinary door systems, Aviles says: "The controls are a little more high-end than what you get on a standard freezer door. So practically, we’ve had less problems with the doors not opening properly, and as long as our people keep them adjusted, they’ve essentially been trouble-free."

The employees, both drivers and managers, love the new doors he says: "It was a significant improvement over the past things we have tried."

HCR markets 10 main styles of doorway systems for coolers and freezers. The systems are differentiated by their suitability for various applications, taking into account temperature difference on either side of the doorway, traffic, air flow and pressure, and other factors. In addition to systems suitable for forklifts, HCR also makes units for conveyor passages.