The Global Steel Potato Storage facility consists of an arched standing seam metal building, concrete foundation, urethane foam insulation, and a CPU controlled air system. The standing seam arched building is comprised of a series of metal arches, each formed into a continuous piece of metal and placed from ground to ground, thus eliminating lap seams in the metal arches. Additionally, the use of the standing seam eliminates the need for bolts. This construction makes it virtually impossible for the arched building to develop water leaks. Another benefit the standing seam arched building offers results from the building’s unique shape. Since the arch shape closely matches the angle of repose of the potato pile in storage, side wall pressure on the building is reduced.
Concrete is used both in the foundation and in the grouting of the building. Global Steel places a small amount of extra masonry sand in the concrete for easy finish. Since the end of the arched panels are grouted into the final pour of concrete, it is necessary to have a good “cream” on the surface to produce a good seal. This method provides just that seal.
Urethane foam insulation in the United States is rated at 7r per inch. Urethane foam, a closed cell structure, is a two part petroleum product that mixes at the tip of the applicating gun. It then expands 32-1 and cures within approximately one minute. Once cured, the urethane foam is inert. In these storage facilities, Global Steel uses a Class A urethane foam with a flame spread of 25 and a 2 lb. density. The CPU controlled Air System is a state of the art atmospheric control system. This feature is critical to the potato storage unit the system regulates the temperature and humidity inside the storage facility.
However, optimum performance of the ventilation equipment is enhanced by quality storage management. If the storage unit is managed properly, potato temperatures should vary less than one degree from the top to the bottom of the potato pile. Additionally, a high relative humidity is achieved through the use of humidifiers. The high humidity aids in minimizing potato shrinkage throughout the duration of the storage season. Some of Global Steel’s customers have indicated that they have incurred less than three percent shrinkage during a storage season. These impressive results relate to the proper storage methods implemented in conjunction with the use of the CPU driven control panel.
Proper management of the storage begins when the potatoes are placed in a pile within the storage unit and go through a 10-day to two week suberization. After the potato pile has had time to stabilize and heal, the temperature is dropped approximately one degree at a time until the desired storage temperature is realized. The temperature is then maintained at this level throughout the storage season. During the very cold months of winter, the volume of humidification used is reduced or the humidifiers are turned off to eliminate free moisture or condensation on the top of the potato storage ceiling and potato pile. The volume of water placed through the humidifiers is related to the temperature variations between the outside and inside of the storage. While it is not uncommon to see beads of moisture on the ceiling of the storage facility, if the humidity becomes too high this moisture begins to form droplets and puts “free moisture” onto the potato pile, which may begin breakdown in the pile. A well managed, controlled atmosphere commodity storage will eliminate the presence of “free moisture” which begins breakdown in the pile. The Global Steel Potato Storage will maintain the quality of the potato by providing adequate air movement and high humidity in an airtight building.
Storage periods of up to 8-9 months are not unrealistic with the use of the CPU air system and proper management. Storage time can be lengthened even further by placing ice in the air plenum near the end of the storage season. It is imperative that the potato pile not be allowed to rise in temperature during this time. Although the ice will not lower the temperature of the potato pile, it will assist in maintaining the temperature of the potato pile to achieve an even longer storage period. Additionally, some potato storages utilize mechanical refrigeration units to lengthen the storage season.
The basic potato storage bay, which measures 60 ft. wide by 160 ft. long, is attached to a fan house or mixing chamber. Return air or fresh air enters the mixing chamber and is redistributed through the air plenum. The air plenum consists of a series of lateral ducts running under the potato pile, delivering the humidified air through the potato pile at a metered rate.
The Global Steel Potato Storage is just one of the innovative products Global Steel offers using the Arch Machine Metal Building System. Global Steel will not only construct the storage facility but also offers training on proper management of the building in conjunction with the CPU controlled air system. Global Steel’s expertise in this area has provided it a competitive edge in the marketplace.
Global Steel has the capability to produce controlled-atmosphere commodity storage to house potatoes, carrots and onions. In fact, Global Steel became a leader in creating safe environments for storing potatoes with its product, the Global Steel Potato Storage. This product implements standard industry guidelines such as storing potatoes for the commercial market at 38 to 40 degrees Fahrenheit with a humidified atmosphere of 97% or higher, without the presence of “free moisture.” Potatoes for processors (French fries, chips, etc.) are stored at a temperature of closer to 50 degrees Fahrenheit. Special care must be taken, however, since these potatoes are more susceptible to bacterial action while in storage due to the higher temperature. These facts have been taken into account during development of the potato storage facility with a CPU controlled air system. Furthermore, the Global Steel Potato Storage is an excellent facility because no structural steel penetrates the insulation envelope. This reduces the possibility of temperature variations on the insulation surface, which would create “free moisture.” It also reduces the possibility of potato breakdown in the potato pile due to condensation that can form from temperature variations.
Global Steel has the capability to provide a storage facility for carrots similar to the potato storage unit. However, since carrots are stored at a temperature as close as possible to 32½ degrees Fahrenheit, adjustments in the facility are made to meet this requirement. Special care must be taken in the storage of carrots as they are extremely sensitive to temperature variations. Any such variations would stimulate sprouting in the carrot. In contrast to potato storage, the carrot is stored in an atmosphere as close as possible to 100% humidity.
Onions are yet another commodity that a Global Steel storage facility can house. The environment can be regulated to store the onions at 34 to 35 degrees Fahrenheit with a relative humidity of 60-70%, which is normal for this vegetable. Higher temperatures are allowable, but usually correspond to shorter storage times.
Grains and Fruits
Many other commodities requiring special environments can be stored in GSI’s controlled-atmosphere buildings. Grains can be stored in a carbon dioxide atmosphere which eliminates rodents and bugs. Additionally, the necessary moisture content can be achieved with the CPU controlled air system or with the installation of a drying system. Fruits, such as apples, are stored in a nitrogen atmosphere.
Global Steel not only supplies buildings and equipment that meet the storage needs of its customers, but it also provides training for the proper management of the commodity storage facility. These features have made it a leader in its field.