Facilities that process, manufacture and store temperature-sensitive products create a host of challenges for workers and facility managers. Inside the facility, the cold-storage doors play a critical role in maintaining temperature separation — essential to better product integrity. Yet, as many facility managers already understand, it can be difficult to find doors that meet regulations in industries that require temperature-critical environments. The doors must provide adequate R value, minimal air infiltration and quick enough cycle times so that the temperature-sensitive products in cold storage are not ruined.
Changing cold-storage door options have created designs that facilities can use to improve temperature separation inside the plant. Offering features such as quick cycle times and the ability to withstand being struck by equipment are reasons that high speed doors are finding a role in cold environments.
Pros and Cons of Traditional Freezer Door Designs
The traditional way to approach industrial refrigeration spaces is to install heavy, insulated, rigid doors with a high R-value. Refrigerated spaces are designed to trap cold inside and keep heat and humidity out, after all.
Such heavy doors perform effectively in low traffic areas. In high traffic areas, however, the slow-moving, side-acting doors can result in longer door-cycle times and higher rates of air infiltration. Having a slow-moving door can make maintaining temperature control inside the freezer more difficult. In addition, hard-core doors are susceptible to forklift damage, which can lead to substantial energy losses if poor sealing results.
Alternatives sometimes selected as a means to minimize air infiltration include folding doors or low R-value, high speed doors. Depending on the model, some solid cold-storage doors may have poor sealing characteristics or an R-value too low to prevent frost from building on the door panel surface itself. (When such frost develops, some facilities add heat lamps or air curtains for the doors at an operating cost of $10,000 or more annually.)
Other traditional approaches include comparatively inexpensive strip curtains and air systems. These designs consist of clear plastic strips suspended in the opening. They have such a low R-value, however, that frost can build up on the strips and floor, and the vision of forklift drivers can be obscured. Although the low upfront cost is appealing, they are not particularly good at sealing most freezer applications — which ultimately makes them an expensive choice in the long run.
Air systems can be either stand-alone or housed in multiple units integrated into a vestibule assembly. Often, these systems do not seal the opening well, and proper alignment is critical for best performance. Vestibules also can require a large footprint, eating up valuable floor space. In addition, air units generally consist of heaters that reduce the relative humidity of the infiltrating air. Unfortunately, it usually takes a tremendous amount of energy for them to operate at a level that keeps the opening free of ice and frost.
This soft-edged curtain door is impactable. If it is hit, the door will fix itself as it rolls up.
High Speed Rollup Doors
The biggest advantage high speed rollup doors offer in cold-storage operations is in their name: high speed. While doors with high R-values offer better temperature separation when closed, their slower operating speeds are detrimental in facilities that maintain regular traffic between spaces. In cold operations that require frequent material-handling operations, doors with slightly lower R-values that reduce air infiltration with fast cycle times become more practical.
Faster doors also may mean less opportunity for materials-handling operators to run into the doors. If some high speed door designs are struck, the doors can break from the tracks and then realign when rolled back up. Some high speed doors come with LED countdown systems that reduces the likelihood of an impact.
Some high speed rollup doors have washdown capabilities and antimicrobial materials. This makes them well suited for use in food and pharmaceutical industries, which are two of the largest segments of cold operations.
Some high speed rollup doors have washdown capabilities and are manufactured of antimicrobial materials. This makes them suited for use in cold-storage applications in food and pharmaceutical industries.
In food and pharma applications, high speed doors can help maintain clean operations and food product integrity. They are designed to address food facility needs for environmental control, productivity and safety, and cleanliness. In cleanroom applications, they are used in applications to prevent cross-contamination. They also help maintain correct room pressures, ensure proper air-circulation rates and optimal operating efficiency.
The U.S. Food and Drug Administration’s cleanroom standards outline recommendations and requirements for manufacturers. The starting point is to look for doors compliant with current good manufacturing practices (cGMP) as well as requirements set by the FDA and the U.S. Department of Agriculture.
Among the key considerations for any door configuration include ease of cleaning and durability. In all cases, the doors must be able to withstand repeated cleanings with chemical solvents and have a smooth, nonporous surface resistant to microbial and fungal growth. Other recommendations and requirements of cold-storage doors for food and pharma include:
- Doors should have tapered surfaces and edges that essentially eliminate harborage of dust or other contaminants.
- They should possess no sharp angles to minimize harborage of microbes.
- They should be corrosion resistant. (This is often a problem with older door systems.)
- Doors should use stainless steel side frames and shrouds.
- They should incorporate a lubrication-free design. (Lubricants can attract particulates.)
Rollup doors have high operating speeds of up to 100 in/sec (2.5 m/sec), which helps to avoid air infiltration in cold-storage applications.
Also, it is also advisable to avoid doors with exposed fasteners and coils because they will take longer to clean and could harbor contaminants.
In conclusion, when evaluating what type of door to implement in an operation that requires low temperatures, it is important to understand if the doors will be used frequently. If they are, using the high speed rollup doors inside the plant may help facility managers improve operational efficiency, decrease energy use, and make the plant safer for employees and customers. PC