Maintaining Silo Roof Structure and Integrity
Silo safety hazards and Silo roof maintenance Like all structures, silos degrade over time. This natural and inevitable deterioration can lead to safety hazards such as falling debris, leaks, wall failure, silo roof failure, and/or structural failure. When it comes to the silo structure, the roof and its design is a crucial component. In addition to this, proper maintenance of the silo roof is a requirement but may pose a significant challenge. Many areas that may require repair are not readily visible and often structural damage is not noticed until a significant failure has occurred, the roof has settled, or the risk of impending total failure has been reached. Leaking silo roofs Leaking roofs can lead to contamination of stored materials which impact 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, or concrete deterioration often due to roof leaks. Spalling of concrete roof beam pockets can further expose beams and lead to eventual roof failure or collapse. Ponding water on the silo roof Signs of ponding water on the silo roof (as well as signs of cracking or peeling in the roof-top coating) are indicators that your roof structure is at risk. Regular ponding 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 supporting roof beam, potentially indicating severe underlying structural problems. Left unaddressed these problems become costlier to correct and increase liabilities. Silo material buildup Problems with silo roof slabs are mostly related to critical structural conditions such as material buildup, the addition of heavy equipment to the original design or flaws with the original design. The roof beam supports should have been designed to accommodate for thermal expansion and vibration from equipment and cycling of the silo by filling and discharging. This is accomplished by allowing the roof beam base plates to freely slide in the longitudinal direction over an embedded steel plate on the wall beam pocket. The embedded plates that support the roof beams are usually involved in the failure process. Weather and temperature changes, vibration, and movement of beams cause the concrete walls to deteriorate faster around the beam pockets than the rest of the silo walls. Such deterioration leads to spalling and loosening of the bond between the embedded steel anchors and the concrete walls. When such conditions occur, the roof supporting steel beam will eventually rest on unprotected concrete. The constant thermal expansion and contraction of the beam, combined with the dead and live loads applied to it, creates a grinding force between the beam’s base plate and the silo wall. Often times this will lead to breakage of part of the silo wall immediately under the beam. When this happens, the beam shifts downward until it rests again on a solid portion of the silo wall. Silo Repair Case Study Beam pockets are a critical point on the silo as these roof beams hold up the roof slab and all the necessary equipment to operate the bulk storage system. One of our recent case histories examine a silo roof beam bearing repair. Regular inspections of the underside of the silo roof along with all equipment are imperative to eliminate potential failures in any production system, including silos. Proper silo roof design is critical. While roofs are designed to hold equipment, they are not designed for excessive amounts of material. If a loading system fails or a silo is overfilled, creating bulk material on the roof, unseen damage can result and compromise the entire structure. To learn more, be sure to check out our full library of silo construction videos on silo maintenance, repair and inspection on Read Silo Roof Beam Bearing Repair – Florida Case History
Concrete, Steel, Jump‑Form & Slip‑Form Silos | Marietta Silos
Early storage silos, primarily used by farmers for the bulk storage of corn, were built using wood, brick, stone or galvanized steel throughout the late 19th century. The use of concrete for the construction of storage silos revolutionized the industry in the early 20th century and expanded the use of storage silos beyond the farm. Today, both steel and concrete silos are commonly used in industry for the storage of ash, coal, lime, aggregate and more. Concrete Silo vs. Steel Silo, Which One is Better? Concrete silos are favored over steel silos because they are a superior cost savings solution that can be designed to resist internal abrasive wear, while withstanding pressures that would cause steel silos to buckle. Over time, concrete storage silos are less costly to maintain – lifetime savings can reach 50-70% over steel construction. As steel structures battle costly corrosion issues – especially when contents have moisture or are corrosive – regular repair of rust areas as well as exterior cleaning and painting is required. In addition, steel silos often need internal repairs requiring the silo to be emptied, creating costly downtime and inconvenience. Cement silos cannot rust and require no exterior painting or cleaning. Additionally, repairs are usually made to the outside of concrete silos without disturbing the inside contents. Advantages of Concrete Silos Concrete silos are typically lower in cost than metal silos. Concrete silos have good resistance to corrosion, including both corrosion of internal walls due to the stored bulk solid and external corrosion caused by moisture. Metal corrosion is a well-known problem. No need for expensive painting of silos due to corrosion thus lowering operational cost. There is no concern about electrolytic effects at welds or liner connections. Careless detailing of metal walls may leave inward facing ledges or welds, which can obstruct flow and increase wall pressures. This is avoided with concrete. Concrete is better able to resist abrasive wear than most metals. Concrete is more robust and thus better able to withstand internal pressure loads and impact loads. Concrete has higher wall friction angles with most bulk solids than most metals. This results in higher frictional drag down the cylinder walls and hence lower pressures acting normal (i.e. perpendicular) to cylinder and hopper walls. There is no concern about weld quality or stress risers, such as bolted connections. There is no concern about leakage to the environment. To learn more about the advantages of concrete silos over steel silos, read our concrete vs. steel safety bulletin. What’s the Difference Between a Jumpform Silo and a Slipform Silo? Jumpform vs. Slipform What are Jumpform Silos? Jumpform construction is an economical construction choice as the form can be set up and ready to make the first pour of concrete within a week. Due to an incremental schedule rather than the continuous schedule, costs are reduced approximately 20% over Slipform construction. Concrete storage silos from 10' to 65' in diameter can be built using this technique. The Jumpform silo framework is reusable and takes just a few days to set up after delivery to the job site. Once set up, the form provides a safe, circular deck used to access and erect the concrete silo from the interior, allowing a smaller job site. When construction is finished, the form is quickly removed from the job site. Since Jumpform silos are poured in a slow controlled process it allows additional time to complete a thorough quality control inspection of the form, steel reinforcements and embedments before concrete is poured. Marietta Silos’ standard horizontal construction joint detail creates a leak-proof joint system. Jumpform construction is the best choice for concrete storage silos less than 65’ in diameter. Marietta Silos is the only Jumpform manufacturer in the country that complies with OSHA 125' scaffolding requirements. What are Slipform Silos? Slipform silos are best for construction projects over 65’ in diameter. They are formed from a continuous, monolithic pour of the concrete walls, which creates a smooth, continuous outer appearance. The need for a continuous pour necessitates a 24 hours per day schedule, including nights and weekends, until the silo is completed. This contributes to a possible 20% increase in overall costs over Jumpform construction techniques under 65' in diameter. The walls of Slipform silos are faster to pour than Jumpform silos. However, the time savings is offset by the time required to construct a custom-built form system for both the interior and exterior of the silo wall. Construction of the Slipform system takes approximately two months to create. Overall, the construction time is equal to the Jumpform. Slipform silo forms are an integrated form and work deck system that includes an interior work deck and interior and exterior finishing scaffolding. The form is also supported by jack rods that are attached to the hydraulic jacks to slowly raise the forms during construction. The forms raise continually, about one foot per hour, with crews working both above and below the rising forms at the same time. Workers on the interior work deck continue to pour new concrete and steel reinforcement along with embedment as the form raises, while workers on the interior and exterior scaffolding hand finish the silo walls as they are exposed by the rising form. Slipform construction is typically the best choice for more than 65’ diameter silo construction or if multiple concrete silos need to be created at one time. Be sure to check out our full library of silo construction videos on silo maintenance and inspection videos on
Types of Silo Repairs to Prevent Silo Collapse
Collapses are often the result of preventable structural failures that would have been identified during routine inspection. Common problems that cause concrete structure and concrete silo failure include foundation deterioration, roof collapse due to roof beam structural issues, improper material filling and unloading procedures in silos, silo wall delamination or deterioration, silo discharge cone or bin floor issues. Steel silos suffer from corrosion and buckling, which can be inspected using wear-measure thickness ultrasonic gauges. Silo collapse in Charlotte, North Carolina [1] Structural Concrete Silo Repair Services Silo Upgrades Silo Post-Tensioning Vertical silo spalling, cracking or wall separation due to overstress of the horizontal reinforcing are the main symptoms repaired with post-tensioning — a very common problem. To solve this issue, Marietta Silos will install high-strength post-tensioning strands around the wall exterior. 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. Silo Roof Repair As with any structure, the roof of the silo 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. Roofs are subject to abuse from overfilling, explosions and overloading, as well as environmental abuse. Marietta Silos uses a variety of techniques to replace, repair or modify silo roofs including a roof-top coating. USA Silo Service has developed a unique silo roof and silo wall sealing method, a rubber product that applies to a concrete or steel silo roof to cover cracks, holes and equipment attachment areas. This sealing method can be used for roof surfaces or for steel bolted silo joints to offer excellent protection against oxidation, humidity and corrosive environments. The rubberized coating also resists alkali, salts, abrasions and fumes. Additional benefits of roof-top silo coatings: Not a floating membrane Offers excellent adhesion to aluminum, galvanized steel, painted surfaces, modified bitumen, steel joints and many other surfaces Excellent in sealing cracks, laps, fasteners and roof surface penetrations Available in all 50 states and in a variety of colors The rubber coating reduces costly reapplications of surface protectants and can be applied to many surfaces including: metal buildings and roofs, built up roof (BUR) membranes, grain silos and bins, silo exterior walls, single ply roofs, urethane foam roofs and steel bolted joints. Silo Rehooping Marietta Silos has vast experience in rehooping concrete stave silos, whether they store foundry sand, lime, clay, cement, grain products or have been adapted for industry use. Older stave silos often have hoops that are corroded, damaged or missing altogether. In order to maintain the structural integrity of the silo, removing unsound hoops and/or replacing hoops with a full complement of new steel hoops may be necessary. Rehooping can ensure your older stave silos regain or maintain their full storage capacity. A special waterproof coating may be applied after rehooping to ensure the long-term durability of the hoops. Shotcrete-Gunite Gunite is a mixture of sand, cement and water, which is applied with air pressure. Not only is it as strong as poured concrete, it is also very resistant to weather and chemicals and bonds 100% to well-cleaned concrete. Silo Strengthening Composite Fiber Reinforcement Marietta Silos is a certified installation contractor for the Wabo® Composite System. This system uses composite fiber reinforcements to strengthen existing concrete and masonry structures for a variety of applications. Available materials used include standard and vapor permeable resins, as well as specialized fibers with low conductivity, chemical, and impact resistance that may be mounted on or near the surface of the structure with no heavy equipment needed. Steel Silo Repair Steel silo repairs typically involve cutting out and replacing worn or corroded portions of a silo as well as relining damaged silo sections. Marietta Silos handles the full design and engineering of steel silo repairs, with safety as our first priority. Our experienced engineers understand the unique loading and load path requirements based on the silo type and stored material. Silo inspections and preventive maintenance can prevent a silo collapse. Routine inspections and repair of silo walls and/or liners are important for preserving the structural integrity and ensuring that the silo is in proper working condition. Visit AskMrSilo.com to ask Mr. Silo any of your silo-related questions and be sure to check out our full library of silo maintenance and inspection videos on . Reference: April 18, 2008: An 80 feet (24 m) tall silo adjacent to the line, just north of the New Bern Station, collapsed, with some of its debris causing minor damage to the track and disrupting service during the evening rush hour. Service was fully restored by the following day, but this marked the first disruption in service since the opening of the line in November 2007 due to conditions outside the control of CATS. [Wootson, Jr., Cleve R.; Steve Harrison (April 19, 2008). "Silo puts kink in LYNX". The Charlotte Observer. pp. 1A.]
When to Schedule A Silo Inspection?
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. Cracking and bulging in a concrete silo wall 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. Corrosion, even on a concrete silo, can result in a complete silo failure 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. Be sure to check out our full library of silo inspection videos on
Silo Maintenance Checklist | Preventive Maintenance for Bulk Storage Silos
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. Silo Inspection: What to Examine Yourself Silo Roof Inspection & Repairs 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 Wall & Foundation Checks 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. Be sure to check out our full library of silo maintenance videos on
Roof-Top Silo Coating
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. One of the most important is checking your silo roof and walls to make sure they are leakproof. Many concrete silos have either a membrane cover, a concrete slab or other material covering the silo roof. Over time, roof covers develop holes, allowing water intrusion under the roof cover material. Once the water gets underneath, it is trapped and eventually travels along the concrete roof to a crack. Once the trapped water finds an opening, water can make its way into the silo and compromise stored materials. Natural freeze and thaw cycles allow water to expand and contract inside fine exterior cracks and jeopardize a silo’s structural stability. Our Roof-Top and Exterior Wall Coating Method It’s essential that your silo is completely watertight. Even pinhole leaks in silo roofs and walls can damage stored materials and can result in blockages and material flow issues. When selecting a roof covering for a concrete silo, it is critical to select a coating that adheres directly to concrete, rather than a roof cover that merely conceals the concrete roof and can hide future issues. USA Silo Service has developed a unique silo roof and silo wall sealing method, a rubber product that applies to a concrete or steel silo roof to cover cracks, holes and equipment attachment areas. Before and After Roof-Top Silo Coating This sealing method can be used for roof surfaces or for steel bolted silo joints to offer excellent protection against oxidation, humidity and corrosive environments. Our rubberized coating also resists alkali, salts, abrasions and fumes. Additional benefits of roof-top silo coatings: Not a floating membrane Offers excellent adhesion to aluminum, galvanized steel, painted surfaces, modified bitumen, steel joints and many other surfaces Excellent in sealing cracks, laps, fasteners and roof surface penetrations Available in all 50 states and in a variety of colors Our rubber coating reduces costly reapplications of surface protectants and can be applied to many surfaces including: metal buildings and roofs, built up roof (BUR) membranes, grain silos and bins, silo exterior walls, single ply roofs, urethane foam roofs and steel bolted joints. Our roof-top silo coating method is a proven industrial roof coating system that keeps elements out and stored materials dry. Request a quote from us today. See Case History – Does Your Concrete Silo Roof Leak? Be sure to check out our full library of silo maintenance videos on
Our Silo Cleaning Method
A clean silo is comparable to a clean bill of health. When a storage silo is working efficiently, it's successfully meeting production goals. If a silo gets clogged or blocked, production slows down immediately and an array of problems and issues become inevitable. Despite the problems that can arise from a poorly maintained silo, many postpone cleaning and often deem this required maintenance as unnecessary. They may also find silo cleaning expensive and not worth the potential loss of production downtime. The fact is: regular cleaning of your silo is a cost savings benefit that removes buildup and recovers lost material, while maximizing production and profit. Why Routine Silo Cleaning Matters Hung up, clogged or slow running silos are a problem that will interfere with efficiency and profitability. Material buildup deters the silo from reaching its full capacity and we have seen many cases where material buildup and blockages only allowed for the silo to reach half of its capacity. Once a silo begins to lose flow, this accelerates the buildup over time and can lead to additional blockages. It is extremely important that the silo be cleaned professionally if material buildup or other issues are visible. Professional BIN Cleaning – Let Our Experts Do the Job We are your resource for silo or bin cleaning. No matter the type of silo (concrete, steel, flat or cone bottom, funnel or mass flow) or type of material stored (cement, clay, fly ash, grain products and more), we are your professional team of experts. Our specialists are also trained to respond quickly to emergency silo cleaning needs, although our goal is to eliminate emergency plant outages related to silo blockages entirely. As soon as a partial blockage becomes apparent, it's necessary to schedule a cleaning. Our silo cleaning methods will: Remove material buildup Restore material flow rates Recover silo capacity Prevent cross contamination Reclaim lost material The Boss – Silo Cleaning Equipment Professional silo cleaning companies typically use a remote, dry cleaning system to remove stubborn material buildup. The most powerful system available in the U.S. is a unique clean-out head, The Boss, proprietary to USA Silo Service. The Boss removes the most material buildup in the least amount of time, making it the most efficient and cost-effective cleaning system available. It’s many times more powerful than a whip cleaning machine and two-thirds more powerful than pneumatic cleaning systems. The Boss is a unique clean-out head designed to accommodate variable attachments which are selected by our field crews to match the type of material being removed. Our silo cleaning technique includes operating in a systematic pattern within the silo to remove the toughest build-ups. In fact, The Boss is 65% more powerful than other pneumatic systems. By removing more material faster and with more efficiency than any other clean-out method, including the whip system, The Boss accelerates the cleaning process. This minimizes downtime and out time on-site, providing immediate cost-savings. Learn more about the advantages of The Boss cleaning system in the video below. Our silo cleaning methods will save you the most time and money. Learn more about our silo cleaning services. Request a quote today.