Traffic Doors and Cold Storage

There really are not perfect choices.

Take the doors used in food processing/handling plants for traffic going in and out of chilled and frozen areas for storage and production. At all of these facilities vehicles go through doorways hundreds if not thousands of times a day to meet split-second schedules. At the same time, temperature differentials can run 35 degrees Fahrenheit or more, and there needs to be protection against heat transmission through these 80 foot (ft)² or larger openings, threatening both energy bills and product quality.

Plants and DCs regard getting product rapidly from the receiving dock to the shipping dock as crucial to profitability. Also important is maintaining proper temperatures to protect food quality where product is handled or processed. Not only is the desired flavor and mouth feel threatened but also product that is warmer than it should be promotes the growth of bacteria and other microorganism contaminants.

Safe at Faster Speeds

Doors play a key role in protecting the low-temp environment—if specified and used properly. In the storage and handling areas maximum temperatures for vegetables are 55 degrees Fahrenheit, dairy products are 34 degrees Fahrenheit, meat at 28 degrees Fahrenheit, and ice-cream at -10 degrees Fahrenheit. Waiting outside the processing or storage room can be temperatures that are 30 degrees Fahrenheit or higher.

That warmer air can be transmitted through walls and door panels. As for walls, the higher the R-value for the insulation the better. But is that necessarily true for doors?

(left) Even with a steady stream of high-mast forklifts accessing the GSF freezer room, this high-speed door on 16-ft. high doorway
can close in under two seconds. (right) At the Palermo’s Pizza plant in Milwaukee, the high speed and tight doorway seal protects product quality while enabling them to save about eight tons of ­refrigerant a year.
Image Credit: Ryetec

Bear in mind that doors have to get out of the way of traffic. So here is the dilemma for facility food processing/handling facility managers—do you cover the doorway with a thick panel door and slow down material handling, or compromise the environment to enable fast traffic flow? Not only is product put at risk if the temperature rises, but to maintain spec temperatures chillers have to work harder, start up more often, and use more energy while shortening their performance life.

Recent research from the Door and Access System Manufacturers Association (DASMA) provides some help in making this choice. The study, “High-Speed Doors and Thermal Performance,” finds that today’s industrial and commercial buildings can deliver high door speed while at the same time save energy, depending on doorway factors.

The DASMA research took into consideration common U-factor, air leakage, and motor horsepower values in a comparison of high-speed doors to conventionally operating insulated doors. Turns out high-speed doors become more energy efficient when cycled 55 or more times per day, according to this analysis. As you may know, in a busy facility doors can be cycled hundreds if not thousands of times a day.

At the GSF DC, 52 dock doors receives product and keeps 460 McDonald’s restaurants supplied with everything from buns to burger patties.
Image Credit: Ryetec

While 55 cycles is the minimum, high-speed doors are typically specified for applications requiring well over hundreds of cycles daily. Thus, the doors studied demonstrate superior overall energy efficiency when meeting the demand for high-cycle operation in a building.

This new approach views the doors as dynamic parts of the building. High-speed doors, in addition to providing rapid access, also contribute to the efficiency of a low temp operation through dynamic thermal performance characteristics when the door is not closed.