Metal Grain Bins
There are basically two common types of round metal grain bins; smooth walled or corrugated walled structures.
Smooth walled bins can be assembled on site using tightly fitted panels or can be prefabricated off-site and delivered to the storage site. Smooth walled bins can be hopper bottomed or flat-bottomed but are most commonly welded metal hopper bottomed bins that are prefabricated and ready to set on a steel unloading base or concrete. The interior of smooth walled metal bins can be are 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.
These prefabricated bins are quick and easy to install. 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 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 in size from small feed bins (~200 bu) to larger sizes (~6,400 bu). very large 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 will affect the load capacity and longevity of your bins. Corrugated metal bins are typically less expensive to buy initially and are cheaper over the long-term because they have excellent durability when well maintained and are typically not used to store corrosive substances like fertilizers.
Metal structures have many advantageous properties including the fact that they are fire and rodent resistant, cheap to maintain and are strong and durable even in winter conditions. Metal grain buildings provide less opportunity for insect infiltration and mould growth and do not wick moisture in from the exterior of the structure. Seams can be waterproofed easily and the interior walls can be easily washed down and cleaned frequently without harming the structure. 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 in use for grain. Wood bins have some inherent disadvantages including not being fireproof or rodent resistant and also requiring frequent maintenance to keep 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 be stacked 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 ensure walls are not overloaded.
Read our other blog: The Importance of Cleaning and Maintaining Your Grain Bins
Flat Bottomed Or Hopper Bottomed Grain Bins
A hopper bottom is a cone-shaped structure that can be either an integral part of the metal bin or it can also be a separate piece that the bin is affixed to upon installation. Smaller, smooth walled metal bins tend to be constructed by manufacturers as one single unit that only requires mounting on a raised base or stand when being 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 due strictly to 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. This is advantageous 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 air flow 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 easy to move and set up in new locations.
Flat bottomed corrugated metal bins are very common on 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.
Aeration is a very important aspect of every grain storage system and can be easier to achieve in a flat-bottomed grain bin. A properly installed and operated aeration system keeps grain in good condition and can help control insect infestations and moisture migration in the grain mass and reduce grain spoilage. Bins not intended for high turnover of contents and for longer term storage where interior monitoring and temperature/humidity control are important are criteria best suited to a flat-bottomed corrugated metal bin.
Larger diameter flat bottom bins (27’ and larger) require some type of centre unloading as to not 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 the use of manually operated bin unloading vacuum systems. Smaller diameter The flat bottom bins (24’ diameter and smaller) can also be more difficult to unload grain from when not using an unload trough requiring and may require more physical labour using a vacuum system or augering out the bin.
Wall Grain experts are here to help. Contact Wall Grain for tips on concrete pad repairs. Or for advice on how to seal over any openings or gaps where rodents can enter your grain bin.
Call us at +1 844-744-9255 for all your grain bin needs.