Storage:
Corrugated Steel Bins
One of the cornerstones of the grain industry is grain storage. The U.S. currently has approximately 25 billion bushels of grain storage, with around 55% on-farm and 45% off-farm. While the exact percentage of these bins that are made from corrugated steel is not known, it is understood that they make up the largest share, with over 750,000 having been erected in the past 75 years.
Steel grain bins are a cost-effective alternative to traditional concrete storage, providing numerous benefits in maintaining grain quality, especially when equipped with additional tools such as aeration and monitoring. Beyond merely serving as storage containers, they play a crucial role in managing market risks associated with grain ownership and in smoothing out fluctuations in the supply chain.
Acknowledging the significant role of steel grain bins in the food supply chain also illuminates the importance of proper selection, installation, usage, and maintenance of these valuable assets.
Selection:
When selecting grain bins, it is critical to know what and how much grain you want to store, along with the intended end use for the grain. Additionally, height and diameter restrictions come into play, as do soil types and foundation selections, and cost per bushel. Decisions regarding the addition of aeration and the required volume of CFM, as well as any monitoring equipment, also need to be made. Site selection is vital and should consider present needs and future growth.
Installation:
It is essential that those involved in installation are trained and qualified, experience matters. Soil analysis and foundation design should be the first steps after site selection. Proper preparation and pouring of foundations are critical; failure to do so increases the risk of structural issues. Placement of anchor bolts, aeration ducts, and floor gates require careful supervision. The assembly of roof panels and bin jacking needs meticulous attention to detail. Installation of fill and reclaim equipment , aeration fans, temp cables sweep augers etc. should all be in the project plan.
Maintenance:
Routine inspections of the exterior of the bins and periodic inspections of the interior should be performed. When walking around the bin exterior look for foundational cracks, drainage issues around bins, water standing on foundation pooling against the bottom sheets, and anchor bolt condition. Look for any signs of water intrusion on the roofs, bins sheets or cutouts for doors, aeration, or equipment. Are there any bin bolts missing or misaligned and is there any indication of separation of sheet laminations?
As you walk around the bin look for any indications of deflection or indentations on the surface, do the wind rings look ok? Check that all roof vents and exhausters are open and allow free air access. When looking at the wall sheets is there any sign of corrosion? Pay special attention to the alignment and condition of the stiffeners. When inspecting the interior look at the roof support members, floors, and for any signs of water intrusion. Also look at aeration ducts, floor gates and sumps. Temp cables and sweep auger should also be inspected during this time. If any conditions are noted during these inspections corrective actions need to be taken asap. As bins age more frequent inspections are required.
Proper selection, installation, and maintenance will minimize the risks of bin failure during their operational lifespan, which can range from 25 to 40 or more years, depending on the design and application.
Why Do Bins Fail?
Bin failures typically result from one of the following categories: improper selection and design, improper installation, improper operating procedures, and acts of God.
While elevator operators cannot prevent failures due to extreme weather or Acts of God—such as high winds, tornadoes, hurricanes, flooding, or lightning strikes, they can mitigate risks through preventive measures in design.
Fabrication errors may cause failure but are very infrequent. Utilizing reputable design and installation contractors can help avoid design and installation issues. However, problems can still arise from lack of accurate soil analysis, improper installation of rebar, poor concrete applications, and misalignment during erection. Roof loads resulting from a fill conveyor , trusses, and catwalks must be considered in the design to prevent overloading . Do not forget to include temp cables in the load calculations. Be sure to account for the operating weight on conveyors and calculate on dynamic loading not just static. Consider supporting conveyors on self-supporting trusses not off the bins, and do not attach truss supports to bin walls or off bin foundations.
If maintenance inspections and schedules are followed diligently and any identified issues are promptly addressed, bin failures can typically be avoided.
Operational Procedures:
Many root causes of bin failures stem from improper operational procedures during filling or unloading. Bin structural integrity relies on uniform loading along the bin walls; off-center loading can undermine this over time. Increasing fill conveyor capacity can create undesigned loads. When space is tight be sure not to overfill the bin where grain is contacting the roof support system.
Uneven unloading poses significant risks. During emptying, it’s important to pull grain only from the center draw until reaching the angle of repose on the side walls. Premature withdrawal from outside floor gates places uneven pressure on the bin, leading it to adopt an elliptical shape rather than remaining round, which can result in catastrophic failures. Bins designed for side draw unloading must have specific design elements that consider sheet configurations, stiffeners, wind rings, and grain ladders. If you are retrofitting a side draw into a bin, be sure to have a structural engineer involved.
Know if your bin design is for single or double pass sweeps. In large diameter bins single pass unloading may result in uneven pressure on the walls. Ensure proper auger selection by consulting your bin OEM or design contractor. When discharging bins in freezing weather be sure roof vents are open to avoid putting a vacuum in the bin leading to collapse. Visual inspections are vital for bins holding non-free-flowing grains with high moisture or F.M. content to ensure there is no hanging material or ratholing. When first filling a new bin be sure to follow the manufacturers’ recommended fill schedule.
Conclusion:
In summary, this blog touched on the high points of steel bins which are a crucial asset in the grain industry, supporting efficient storage and management of grain quality. Proper selection, installation, operations, and maintenance are key components to maximizing their lifespan, functionality, and safety. Understanding the potential causes of failure and adhering to best practices can greatly enhance the resilience of these structures against both environmental factors and operational challenges and operators can safeguard their investments and ensure a reliable grain supply chain for years to come.
Regards,
Grain Guy Fifty
