Examine grain bins and handling equipment for wind damage

When steel grain bins sustain wind damage, careful inspection is needed to evaluate repair or replacement options. Ken Hellevang, professor emeritus and retired North Dakota State University Extension agricultural engineer, recommends receiving inspection assistance and advice from a bin manufacturer representative. He says they have the expertise to evaluate the damage and provide recommendations for repair or replacement.

Metal grain bins are designed to carry loads imposed by grain. The round shape puts the metal wall sheeting in tension as the grain pushes outward. Wind load on a bin wall pushes in on the windward side of the bin while it pulls out away from the bin in the remaining directions. Wind, in effect, tries to crush the bin, pulling and pushing it out of shape.

Wind also tends to push the windward roof inward, collapsing it into the bin, while it can produce a suction on the leeward side of the roof. Wind moving through a group of bins can cause the wind to accelerate between and around bins, significantly increasing wind load.

“A bin with a deformed wall is also likely to have the bin wall pulled up from the foundation and the roof pulled down,” says Hellevang, “so the entire bin needs to be inspected.”

An initial inspection should look for alignment, any indents or bends in the bin sheets, the connection between the roof and wall, and the wall connection to the foundation.

Start on the outside of the bin, far enough away so that you can see the top of the bin. Walk completely around the bin to see if the walls are straight, the eave is parallel to the ground and no wall or roof sheets are missing or badly deformed. A bin can slide on its foundation, so check if the bin appears to be centered on the concrete foundation.

Also, check if doors are intact and not out of square. Does the sealant between the bin wall and the concrete foundation look to be intact? If the sealant is damaged, then the wall sheets, bin or anchors may have failed.

The following are some of the items that Hellevang advises to examine during an inspection:

• Are any anchor bolts or anchor plates missing, bent, or broken?
• Does the concrete show any cracks that indicate that the anchor bolt is not being held securely?
• Are there bolts or bolt heads missing? Is there any stretching or other indications of movement at bolt holes? Are the bolts tight?
• Are the wall sheets buckled or flattened? Deformation may overload steel, resulting in a loss of strength. The sealant between sheets should be intact, too.
• Inspect door openings and other openings in the wall. The opening frame should be square with no frame member buckling. The welds should not have cracks or otherwise show signs of failure.
• Stiffeners (vertical members attached to the bin wall) should be straight. The bolts attaching the stiffener to the wall, wind rings and foundation should not show evidence of deformation as described earlier. The base plate connecting the stiffener to the foundation should sit flush on the foundation with shims installed as needed.
• Wind rings may be used on the bins to help keep the bins round. The wind ring bolt connections attaching the ring to the wall or stiffeners should be present and tight. The rings should be round in shape and not deformed.
• From the doorway, examine the interior of the bin walls for damage.
• Look for light entering the bin from damaged components.
• If a raised aeration floor is installed, check if the floor attachment to the wall is damaged and if all bolts are present. Also, look for wall deformation near the raised floor line.
• Look at the inside of the roof to see if the roof sheets look damaged (bent). If the roof is attached to the wall through clips and bolts, inspect the bolts and clips for damage and tightness.
• Examine the roof for bent or deformed roof sheeting ribs. Are the sheets running evenly down the roof slope?
• Are the roof-to-wall clips and bolts that connect the wall to the roof sheeting present and tight?
• Are the supporting roof rings round and secured in place with tight bolts if present on the roof?
• Is the door for the top opening in the bin roof bent or dislocated relative to the opening in the roof? The seal should be intact and capable of sealing so moisture cannot enter the bin.
• Examine roof vents. Damaged vents will affect the aeration system.
• Check junction boxes at the fan and all controls.
• Is the electrical conduit damaged? Are conduit joints sealed and intact? Does the conduit run straight, or is it pulled away from a straight run?
• Are connections to the fan motor and all controls and sensors intact and sealed?

Grain handling equipment such as bucket elevators, downspouts, cross conveyors and support structures should also be inspected for damage caused by the wind or by stresses from movement of attached bin parts. Again, look for alignment, deformation and connections that will impact the function and strength of the equipment.

Document with pictures and take legible and complete notes.

Hellevang says that filling a bin that has some damage may lead to an imbalance in loading, which in some situations could lead to a bin failure. There may also be entry points for water and inadequate aeration due to air leaking out of the bin rather than going through the grain.

Before making replacement decisions, consider the overall grain system design and suitability for current and future needs. While storm damage and repair are stressful and costly, it may present an opportunity for redesigning the system.