Prevention is the most effective method to ensure the integrity of concrete structures, surfaces and silos. A proactive maintenance and inspection program is crucial to increase the life of your concrete and ensure the safety of those working around your structures. A proactive safety program should always include annual or semi-annual inspections to check for concealed damage and to assess visible problems that could lead to structural failure.
Though concrete is a superior material for the construction of storage silos, normal loading and unloading operations can lead to structural issues over time. Cracks in silo walls, linings and foundations are an indication of stress.
Concrete walls that show horizontal, vertical or diagonal cracking may be an indication of delamination, or separation of the concrete into layers. Delamination of the concrete is caused by the lack of bonding to the interior structural steel reinforcement, thus weakening the silo’s structural capacity. Issues of this nature will require repair sooner rather than later. Delamination of silo walls can lead to wall failure or collapse and should be addressed by a professional silo repair company immediately. Corrosion of metal silo components, exposed rebar or other deterioration like spalling should also be noted during a visual inspection.
Horizontal and vertical cracks are typically caused by temperature variations, moisture and internal pressure from the stored material. Cracks can cause concrete and steel rebar corrosion which can decrease wall stiffness, allow deflection, degrade durability and strength due to carbonation, and permit water penetration into the concrete wall.
To repair cracks in a poured in place silo, an epoxy injection is used to fill in the cracks. After epoxy injection, it is recommended to add post-tensioned strands completely around the silo area of delamination to provide additional structural integrity. These strands can replace all of the original steel reinforcing and, assuming the concrete is still sound, the silo can be returned to its original load capacity in an economical manner.
Much of this damage is preventable through routine inspection and maintenance. Third-party inspections, maintenance and repair services are the best way to manage safety on any scale. Many structural issues can be easily and economically addressed if caught early. One of our recent case studies inspects a slipform concrete silo with a horizontal crack.
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Regular silo inspections, on annual, two- or five-year intervals, can help identify problems that increase the risk of structure collapse. Based on inspection results, preventive maintenance can be performed to avoid larger more expensive repairs later.
Time, weather and usage are all contributors to the degradation of silo structures. The signs of degradation and the failures observed are different in concrete and steel silos. For example, with steel silos, those signs include wall deformations, buckling, wear and corrosion. For concrete silos, those signs can be observed in the form of silo wall delamination, cracks, rebar corrosion and discharge configuration issues.
Silo Inspection Components
Proactive silo inspection helps ensure continued, safe operation. Common problems include various roof issues, wall cracking, material buildup and cone failures. Frequent, regular observation of the whole silo structure is the best way to catch potential problems early and avoid possible safety issues.
Silo inspection companies examine aspects known to be potential areas of failure. In general, this includes foundations, walls and roofs. For concrete silos it also includes cones or discharge configuration.
Foundations
A strong foundation is integral to wall stability and the overall safety of the workplace or structure. Cracking foundations and erosion of earth around the foundation are relatively easy to identify during general inspection if above grade. Other issues, such as settlement, can only be identified through close examination by a qualified professional.
Walls
Walls are placed under an enormous amount of stress horizontally and vertically during the normal useful life of the concrete structure or silo. These stresses can result in horizontal, vertical or diagonal cracking of the concrete walls or offset stave joints in the case of stave silo construction. Cracked silo walls can indicate delamination which greatly comprises the structural integrity of steel reinforcement in the silo wall and can potentially lead to failure or collapse if not repaired immediately.
Cones, Floors, Shelves and Tunnels
Silo discharge cones are frequently at the forefront of silo failures and should be of utmost importance in being inspected for wear, weld condition and structural integrity. Silo floors, shelves and tunnels are particular areas of concern with regard to concrete deterioration as they typically involve an interface of steel and/or concrete which can draw moisture, introduce or show signs of movement relative to structure and lead to water and material leaks.
Roofs
As with any structure, the roof generally receives the brunt of the physical and environmental abuse. Proper roof maintenance is needed to keep the materials within the silo safe and dry and prevent further damage to other concrete structures.
Silo roofs are subject to abuse from overfilling, explosions, vibrations and movement during silo loading or unloading and overloading, as well as environmental abuse. Buildup of excess material leaking from conveyors on top of the roof can put undue stress on the internal infrastructure and lead to roof sag which increases the risk of collapse.
We offer advice on all levels of silo inspection, repair, dismantling and reconstruction as well as concrete repair services for industrial concrete. To begin your silo inspection process, contact us today.
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When a silo has structural issues or starts clogging, so does production. Proactive maintenance is the most effective method to ensure the integrity of concrete and steel silos and is crucial to increase the life of the silo.
Bulk storage structure (e.g. silos, bins) failures don’t occur suddenly without any signal or warning. In most cases, the silo structure shows small signs of distress until the signs become too obvious and have caused the structure to fail and potentially collapse. Much of this damage is easily preventable through routine silo maintenance and inspection. Many structural issues can be easily and economically addressed if caught early.
What to Examine Yourself
Silo Roofs
Roofs are an essential part of the silo structure. During in-house inspections, you should look for signs of cracking or peeling in the roof-top coating. Leaking roofs can lead to contamination of stored materials that impacts product quality.
Water penetration also leads to corrosion of metal silo components like roof beams – an issue that can lead to total roof failure if not addressed. Roof beams are a frequent area of corrosion, often due to roof leaks. Spalling of concrete on roof beam pockets can further expose beams and easily lead to a roof failure or collapse. You should also look for signs of ponding water on the silo roof. Regular ponding that sits on the silo roof lowers the lifespan of coating membranes and can lead to deterioration and leaks. More seriously, ponding water is usually caused by issues with the roof beam that supports the roof and can indicate potentially severe structural problems. Left unaddressed, these problems become costlier to correct and increase liabilities.
Exterior Surfaces
Though concrete is a superior material for the construction of storage silos, normal loading and unloading operations can lead to structural issues over time. Cracks in silo walls, linings, roofs and foundations are an indication of stress.
Concrete walls that show horizontal, vertical or diagonal cracking may be an indication of delamination, or separation of the concrete into layers. A serious issue, delamination of silo walls can lead to wall failure or collapse and should be addressed by a professional silo repair company immediately. Corrosion or buckling of metal silo components, exposed rebar or other deterioration like spalling should also be noted during a visual inspection.
In-house inspections should include verification that preventive maintenance measures are being followed. Silo maintenance should include regular checks of airflow systems, a routine professional cleaning and regular, complete silo emptying. Of these measures, one of the most important is the regular emptying of silos.
Silos that are regularly emptied and refilled are less likely to experience buildup issues seen in those kept topped off. Regularly emptied silos need professional cleaning less frequently in comparison. They are also less likely to experience problems like compacting and hydrating. Hydration occurs when moisture mixes with stored materials and causes them to solidify within the silo. When this happens, materials can expand and cause added wall pressure which increases the likelihood of structural failure. Lime and cement are highly susceptible to compacting and hydrating respectively.
Silo Maintenance Checklist
Prepare a preventive maintenance checklist to facilitate data recording and referencing that clearly establishes which components are to be evaluated and which inspection criteria to use.
- If your silo is constructed of reinforced concrete, check for any signs of corrosion, exposed rebar, unusual cracking, concrete spalling or wall stains indicating leakage.
- If you have a metal silo, look for bolted joints near the hopper’s top, waviness along the sheet edges, bolt hole elongation, cracks between bolt holes, outward bulging of the cone shell near the top and damage at vertical seams.
- Determine minimum wall thicknesses required for structural integrity and compare these to your silo’s actual wall thickness.
- Look for and repair or replace damaged or loose liners.
- Remove material buildup that could trap moisture on the outdoor silos’ exterior.
- Check for warning signs, air blowing in or out of vents, wear patterns, vibration or spillage.
- Inspect and maintain mechanical equipment including gates, feeders and dischargers. (When repairing or replacing any mechanical component, remember that seemingly innocuous changes can have significant effects)
If you spot anything wrong during your routine maintenance checks, stop discharging and filling the silo so you can assess the structure’s integrity, and summon expert help.
In addition, annually inspect all alloy, aluminum, stainless steel, and plated components, checking for corrosion, intergranular cracking, pitting, and deterioration. Verify that all bolted connections are properly torqued, retighten loose connections, and re-examine them within 3 months. Annually inspect the interior and exterior finish for damage, wear, or corrosion, and touch them up or repair them as needed.
Every 6 months, inspect the guardrails for looseness or damage, the wear liners for erosion, the ladders for looseness, and the manholes for proper alignment and fit. Check gaskets for unusual wear, and lubricate hinges as needed. Once every 3 months, inspect all relief valves and vents to make sure they’re clear, free, and operational. It’s also important to verify that safety signs are applied to manholes and all attached equipment, and that all personnel have read and understood them. You should always perform a post-disaster examination of the silo and all components and make sure that problems are immediately corrected.
When it comes to keeping your silo clean and running efficiently day in and day out, it's vital that you are proactive with preventive silo maintenance. Marietta Silos and USA Silos are the leading industry experts when it comes to silo inspection, cleaning, maintenance, and repair. Contact us today to schedule a silo inspection.
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