Editor’s note: The following is an excerpt from an article published in the March 2017 issue of Dry Cargo International.
Grain storage is steeped in decades of tradition. Grain producers have long relied upon multiple low-maintenance metal bins or silos that each hold a small capacity of grain with varying degrees of purity. Keeping product separate allows for easier mixing and selling.
But for companies bringing in and pushing out a high volume of grain or milled product through a port, a dome is a better fit for many reasons. As more companies are discovering, a reinforced concrete dome is cost-competitive with silos and delivers increased protection over storage facilities with seams. In fact, the continuous dome shell provides greater ability to regulate internal conditions, including humidity and temperature control and pest protection.
How domes mitigate major grain concerns
Since wheat, corn, canola, soybeans, and the like are sensitive to moisture and temperature changes, an airtight structure that wards off water and controls the interior environment is the best way to ensure quality control. Here are a few considerations when planning a grain-storage facility:
- Increased and improved storage
Oftentimes those who buy land on a port get less property for their money, requiring decisions on how to get the necessary storage on a smaller parcel of land.
“If a port does not have height restrictions, which some do, the most efficient thing is to go vertical instead of horizontal,” Dome Technology sales manager Lane Roberts said.
Because of its height, a dome allows companies to stack product deeper, taking up less property at the site. The double curvature of a dome lends itself to the ability to build up, rather than out, and that curve provides strength at all points of the structure, even near the apex. The entire interior of a dome, then, can be used to contain product.
- A structure that lasts
Facilities storing grain should be robust enough to tolerate frequent loading and unloading. “The storage facility needs to be able to hold a high volume and be able to handle its throughput. A dome can handle that because of its structural integrity, (but) steel bins after a certain amount of time wear out. Steel bins are not built for high throughput,” Dome Technology sales manager James Stoker said.
That’s because steel bins are built with fasteners or welded seams to secure metal sections together. Frequent loading and unloading cycles fatigue the bin at bolt holes or weld imperfections until a crack develops at these locations and causes structural failure. Filling and emptying will stress a dome too, but a dome’s rebar can accept the force without the same fatigue problems; the stress is not channeled to weak spots like bolts or seams because there aren’t any.
- Superior product protection through climate control
Insulation doesn’t come standard with traditional storage facilities like bins and silos, and fluctuations in external and internal temperature, plus the possibility of moisture or condensation inside the structure, can compromise product integrity and pose a danger for volatile materials.
In contrast, a dome staves off some boundary issues other structures face. First, the airform covering the entire dome prevents water and moisture from seeping in. Important for moisture-affected products, this feature eliminates introduction of outside water into the pile.
Secondly, the combination of waterproof membrane, reinforced concrete shell, and continuous layer of polyurethane foam prevents extreme interior temperature fluctuation; these features reduce heating and cooling of the walls and air inside, preventing condensation.
Aeration systems, and a cable array of moisture meters and temperature cables ensure internal conditions are ideal.
- Heat, fire and explosion
Heat spoils grain, which spoils a company’s bottom line. But grain can also be combustible—the dust especially—and explosion happens when an ignition source lights a dust cloud generated by moving product. “The dust is very explosive, so you’re trying to control ignition sources through correct wiring methods, making sure it’s rated for the area or minimizing the amount of electrical equipment in the area,” Aagard said. Dome Technology’s team of experts will help customers identify the right equipment for a dome and the ideal places to put it.
- Food-safe finishes and materials
Food-safe paint is necessary when storing products intended for human consumption. It’s an expensive but necessary finish for food products headed directly to customers. The paint creates a barrier between product and concrete.