by Rebecca Long Pyper, Dome Technology, US

 

With greater focus on food safety and increased capacities, storage structures need to get more sophisticated too. Enter a monolithic, steel-reinforced concrete dome from Dome Technology, a company that has been building domes for more than four decades in capacities ranging from 5,000 to 200,000 metric tonnes.

"The dome is an affordable structure that fits the grain industry well. Concrete is going to be more durable, making a dome more of a long-term investment, compared to other storage options," says Dome Technology Sales Manager Heath Harrison, a grain-industry expert of 20 years, who previously worked in management for major grain companies in the Midwest and West Coast of America.

 

The shape of domes to come

Historically, the most popular domes for grain customers are the hemispheric dome and the DomeSilo. Companies with ample land might select the hemispheric dome, a storage solution that can be built to hold any amount.

On the other hand, companies requiring substantial storage, on a smaller parcel of land, might consider the DomeSilo, a tall and narrow dome in which product can be stacked deep on a small footprint. Increased capacity is made possible by geometry: the double curvature of the dome lends itself to building up, rather than out, and the curve provides strength at all points of the structure, even at the apex. The entire interior of a dome can be used to contain product, not to mention domes are designed to withstand high wind and seismic events.

Every dome model delivers flexibility. For products where explosion is a concern, round relief panels channel pressure out of the structure, preventing structural damage. Integrating existing reclaim systems is always an option with a dome. And for companies moving product from barge to storage to truck in short order, the Drive-Thru DomeSilo might be the answer.

 

Longevity and low maintenance

A dome differs from steel tanks and silos in key ways, including upfront and long-term cost savings. A dome has a longer life cycle than a steel tank, and compared to a silo of similar dimensions, a single dome stores more product.

Diverse foundation systems may reduce deep-foundation costs. A dome can be built quickly, once the outer weather proofing membrane is in place, equipment moves inside so construction can proceed regardless of the weather. This allows for construction to take place year-round.

 

Other dome benefits include strength, climate control and optional food-safe features:

Strength: The dome"s tolerance for cyclic throughput is high because of its structural integrity. Filling and emptying will stress any structure, but a dome"s rebar can accept the force without fatigue problems; the stress is not channelled to weak spots, like bolts or seams, because there aren"t any. The robust nature of a dome doesn"t require regular maintenance, and the concrete shell"s lifespan is indefinite.

For processors, shuttle loaders and exporters, blending can be a key component. The strength of the dome makes blending and mixing possible. A dome is cost competitive with silos, when providing the ability to pull from multiple gates, an option limited with steel tanks.

"Domes allow you to maximise blending capability, giving companies the opportunity to maximise profits and efficiencies," Mr Harrison says.

"It"s also allowing us to cycle the bin multiple times, which can be an issue with other storage."

Climate control: A stable interior climate begins with the first step of the building process,, with inflation of the PVC airform that provides the form for what will become the concrete shell. The airform remains in place indefinitely to provide weatherproofing for the structure.

With the airform inflated, polyurethane-foam insulation is applied to the inside, as part of the construction process, and to protect the concrete shell for the lifetime of the structure. Shotcrete is then applied, with rebar providing reinforcement.

With construction complete, a dome staves off some boundary issue steel bins and silos face. In addition to the airform acting as an impermeable membrane, the heat-sink properties of the reinforced concrete shell, combined with the outer layer of polyurethane foam, prevents extreme interior temperature fluctuation. This reduces heating and cooling of the walls and air inside, minimising or eliminating condensation that damages grain"s integrity.

Aeration systems, customised to each project, also ensure climate control. These can be built into the floor or included in removable tunnel systems.

Food-safe options: Recent expensive recalls have led industry experts to anticipate changes to the Food Safety Modernisation Act and government regulations, within the next five years, requiring grain companies to cover ground piles.

"The public is becoming more aware of where their food comes from, due to the media and education, and companies are seeing increased costs, due to recalls and food-safety issues, so food-safe storage is definitely getting more focus and will continue to in the years to come," Mr Harrison says.

"Domes are a great solution for reducing ground-pile losses and increasing food-safe storage capacity for any company looking at reducing expenses, gaining efficiencies and maximising their operation."

For those working with ground piles, the hemispheric dome can utilise the same footprint, or even shrink it up a bit, and incorporate existing tunnels and conveyance systems.

Those in the milling industry can select food-grade coating on a dome"s interior. Dome Technology has been applying polyurea on the inside surface of sugar domes for years. Stainless-steel conveyance and reclaim screws and lubrication, with food-grade mineral oils, meet food-safe requirements.

A turnkey solution: According to Mr Harrison, more grain and milling companies are interested in selecting a single company to manage the entire scope of a new project. Dome Technology"s expertise in engineering and construction suits them for this kind of role; for instance, Dome Technology built a canola dome for agricultural-goods processor Louis Dreyfus Commodities in Yorkton, Canada, and also provided engineering, mechanical works and tunnel systems.

The team additionally completed a Louis Dreyfus Commodities project in Cahokia, Illinois, a dome capable of storing 18,000 metric tonnes of grain, that tied into an existing barge loader, and provided access to a rail pit on site.

The company selected Dome Technology, after determining a concrete dome would be the best solution for its canola storage needs at the Yorkton site, says Louis Dreyfus Project Manager Ross McEllhiney.

"This is our first time in using concrete domes for this type of storage, and Dome Technology was determined to be the most qualified for this application and location," he says.

By working with an expert team, to design and execute a custom facility, companies will reap benefits from capacity to throughput.

www.dometechnology.com

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