Metal Grain Bins

There are two common round metal grain bins; smooth-walled or corrugated walled structures.

Smooth-walled bins can be assembled on-site using tightly fitted panels or prefabricated off-site and delivered to the storage site. Smooth-walled bins can be hopper bottomed or flat-bottomed. They are commonly welded metal hopper-bottomed bins that are prefabricated and ready to set on a steel unloading base or concrete, which makes them easier to install. The interior of smooth-walled metal bins is typically epoxy or enamel coated to increase bin longevity and decrease corrosion caused by storing commodities like granular fertilizer. Additives to the interior bin coating can also improve material flow and ease of cleanout. Typically grain is unloaded from the cone bottom of the smooth-walled hopper bin using gravity. A high degree of slope on the hopper bottom bin walls and a very smooth interior surface allow the grain to flow freely down the bin walls leading to the discharge chute at the bin centre. The degree of bin slope is often customized to the type of commodity stored in the bin.

Smooth-walled grain bins range from small feed bins (~200 bu) to larger (~6,400 bu) industrial-sized bins.

Corrugated metal bins are comprised of bolted-together galvanized steel sheets of corrugated metal. These precision-cut sheets fit together tightly using a system of bolts and fasteners. Corrugated bins can come with metal stiffeners added either internally or externally. The stiffeners usually consist of metal ribs or rings that add strength and load capacity to the bin structures. The depth of the corrugations and the gauge or thickness of the steel can vary by manufacturer and affect the load capacity and longevity of the bins. Corrugated metal bins are typically less expensive to buy initially. They are cheaper over the long term because they have excellent durability when well maintained and generally are not used to store corrosive substances like fertilizers.

Metal structures have many beneficial properties, including being fire and rodent resistant, cheap to maintain and strong and durable even in winter conditions. Metal grain buildings provide less opportunity for insect infiltration and mould growth. They also do not wick moisture in from the exterior of the structure. Seams can easily be waterproofed, and the interior walls can be washed down and cleaned frequently without harming the structure. Another benefit is that fully sealed metal structures can be easily fumigated for better control of stored grain insects.

Wood Grain Bins and Structures

Grain bins can also be constructed of wood. Wood bins can be round, rectangular or built into an existing peak-roofed or arch-roofed structure. The advantage of placing grain storage within an existing structure is that the building can be functional for other types of storage when not used for grain. Wood bins have inherent disadvantages, including not being fireproof or rodent-resistant and requiring frequent maintenance to keep them weatherproof. The ability to load and unload grain from the storage effectively may also create extra work as grain handling equipment like augers and bin sweeps are difficult to position within the space. Grain inside wooden buildings is often stored in grain bags or flexible intermediate bulk containers (FIBCs) that can stack on pallets and racks. When bulk, loose grain bins are situated inside a wooden building, they are often built as bunks or cribs. Wood bins such as these may require structural reinforcement to prevent overloading walls.

Flat-Bottomed Or Hopper-Bottomed Grain Bins

A hopper bottom is a cone-shaped structure that can be an integral part of the metal bin or be a separate piece to which the bin is affixed upon installation. Smaller, smooth-walled metal bins tend to be constructed by manufacturers as one unit that only requires mounting on a raised base or stand when installed. Some manufacturers build metal bin hoppers (cones) as add-ons or additions to corrugated metal bins. These hopper base structures have reinforced metal legs, or metal stands to create space for an auger under the bin.

Smooth-walled grain bins tend to be predominantly hopper bottomed because the slippery interior wall surfaces are part of the grain unloading system of the bin. Hopper-bottomed bins can be easily unloaded and cleaned without mechanized equipment. This is from the effects of the gravity assist on the flowable grain or granular products moving down the bin into the discharge area at the centre bottom of the bin. It is beneficial for bin users as it can decrease the need for mechanized equipment required inside the bin to unload it. Hopper bins can be used for grain aeration and drying, but a flat-bottomed bin is often better suited for situations where grain conditioning and aeration are of primary importance. The airflow patterns inside a hopper-bottomed bin are less conducive to creating good drying air movement throughout the grain mass. It’s also important to note that properly maintained hopper-bottomed bins tend to keep their resale value and are easier to move and set up in new locations.

Flat-bottomed corrugated metal bins are common in the Prairies because they have many benefits, such as ease of construction, large capacity, lower initial purchase costs, and excellent longevity. Flat-bottomed bins with integrated aeration systems are very effective at conditioning and drying stored grain. Perforated floor systems for aeration and grain unloading systems, such as grain sweeps or trough-style unload systems, can be built into the flat-bottomed bin to increase functionality at a reasonable cost.

Why We Recommend Western Canadian Producers to Have Aeration Flooring in their Grain Bins

Aeration flooring in a flat bottom bin is highly recommended for Prairie producers requiring longer-term storage. Aeration flooring can OPTIMIZE grain storage on your farm! This technique, used in flat bottom grain bins, involves circulating air beneath the perforated floor to remove excess moisture. Not only does this dry down your grain faster and at a lower cost, but it also maintains the perfect temperature for storage without relying on fans or dryers. It also helps prevent the build-up of hot spots where pests and fungi can thrive, saving you from costly problems in the future.

Larger diameter flat bottom bins (27’ and larger) require some centre unloading so as not to overload one side of the bin. A flat-bottomed grain bin without a trough unload and bin sweep built into the floor can be more labour-intensive to clean between grain batches and may require manually operated bin unloading vacuum systems. Smaller diameter flat bottom bins (24’ diameter and smaller) can also be more challenging to unload grain from when not using an unload trough and may require more physical labour utilizing a vacuum system or augering out the bin.