Repair of Silo Cracking and Delamination from Asymmetric Flow – Illinois
Market: Mining Material Stored: Clean Coal Silo Size: 70′ diameter by 200′ tall, Quantity (2) with Interstice Issue: Asymmetric flow caused concrete delamination. Project Background Two silos that were Slipformed concrete with an interstice connecting them. Pictured above are two Slipform concrete silos with an interstice connecting them. Designed in the 1970s, these silos were originally constructed to be internally reinforced, however, due to asymmetric material flow within, the exterior concrete began to crack and delaminate. To remedy this issue, steel post-tensioned strands were installed for additional structural support. The strands work to essentially hold the walls against the additional stress put on them by the asymmetric flow. Due to the interstice prohibiting the post-tensioning of the reinforcing steel hoops to be placed uninterrupted around the silo, holes had to be drilled through it. This allowed for the reinforcing steel hoops to maintain constant contact with the silo walls to minimize future cracking and delamination of the walls. A closer look at the silos. Product flow was not commonly studied until the 1980's. Asymmetric flow is when the material, instead of flowing straight down through the middle, actually flows against the silo wall. Experts now know that this flow type creates stress against the concrete wall. The silos pictured were not designed to handle this added stress and therefore needed the additional structural support. Initial design in any new construction is imperative, and with continuing education of how the silos function, material flow is considered during new silos in the design phase. Today this issue could have been prevented prior to construction with the advances in technology.
Cracking Stave Silo Repair – Texas
Market: Manufacturing Material Stored: Coke Silo Size: 28′ diameter by 60′ tall Issue: Cracking staves Project Background Silos that were constructed with concrete staves. The silos, pictured above, were constructed with a poured in place base and concrete staves with steel galvanized hoops around the silo for added structural integrity. Due to cracking staves, the silos have additional steel galvanized hoops around the bottom portion. To repair the cracked staves, walls were first stabilized in the affected areas. Steel wire mesh and reinforcing steel were attached to the surrounding, undamaged, staves. To increase the load capacity of the stave silo wall, 4” of gunite was added around the entire silo circumference. Below is an image of the repair in process. It is imperative to have silos inspected regularly. In the manufacturing process, these silos are in constant use. This, coupled with the stave silo design, makes regular inspections and preventive maintenance supremely important.
Repair of Improper Lime Stave Silo Coating – Texas
Market: Chemical Manufacturing Material Stored: Lime Silo Size: 26′ diameter by 78′ tall Issue: Inappropriate coating. Project Background A concrete stave silo that was coated with latex paint. Pictured above is a concrete stave silo that was coated with latex paint. This coating was inappropriate for the application and allowed time and the weather elements to affect the silos. The coating deteriorated in a short amount of time, did not seal or protect the steel galvanized hoops and did not seal the concrete staves from moisture. Stave silo construction utilizes the steel galvanized hoops for the structural integrity of the bulk storage system. Failure to protect them in the correct manner will shorten the designed structural integrity of the entire system. The best coating to use on concrete stave silos is a cementitious silo coating. In order to effectively repair a silo in this condition, the improper coating must be removed in its entirety. This process significantly adds to the repair costs. A cementitious silo coating is ideal on concrete stave silos as it protects the steel galvanized hoops and prevents leakage. Marietta Silos applies a proprietary cementitious coating that ensures long lasting protection of the concrete staves and the steel hoops. To ensure longevity of your bulk storage system, it is very important to choose a company and engineering firm with experience instead of basing the decision solely on price. This issue could have been prevented and saved a lot of money. It is recommended that all silos are inspected periodically to insure their structural integrity, operability and safety.
Silo Repair of Rusted Hoops, Broken Staves and Wall Failure – Oklahoma
Market: Manufacturing Material Stored: Aggregates Silo Size: 28′ diameter by 58′ tall Issue: Rusted hoops, broken staves and wall failure Project Background A silo that was constructed with concrete staves and utilized steel galvanized hoops. Pictured above is a silo that was constructed with concrete staves and utilized steel galvanized hoops around the silo for structural integrity. Marietta Silos was called in after failure to inspect this silo and provide recommendation for repair. This silo demonstrated rusted and broken hoops, broken staves and silo walls that failed about 10' down from the roof. This could have been prevented with regular inspections of these stave silos. Silos are a bulk storage and material handling system that requires preventive maintenance the same as all other operating equipment in the process.
Sawdust Silo Repair Following Silo Explosion – Kentucky
Market: Manufacturing Material Stored: Sawdust Silo Size: 26′ diameter by 80′ tall Issue: Silo explosion Project Background A concrete silo after ignition of sawdust that caused an explosion. Pictured above is a poured in place concrete silo that is used for storage of sawdust. Marietta Silos was called in after the silo exploded after contents or dusts created inside the silo were ignited. Pictured above, the silo is still being soaked to cool down the material inside. The explosion physically blew the roof up, blew out some concrete around the top and detached a large section of the rook handrail. Marietta Silos fixed this silo by removing the roof, repairing the damaged walls and then constructing a new roof slab. Explosions do not happen often. However, customers need to be aware of potential hazards and preventive measures of such incidents for their silo storage material type.
Aggregate Silo Wall Failure Repair – Pennsylvania
Market: Manufacturing Material Stored: Aggregates Silo Size: 28′ diameter by 66′ tall Issue: Wall failure Project Background A concrete stave silo wall failure. The above picture shows a wall failure in concrete stave silos that used steel galvanized hoops for structural integrity. Originally designed for silage storage in agricultural markets, these silos are typically of simple design with a gravity fed, bottom center discharge location. As industry grew and advantages of silos for bulk storage of loose materials were recognized, stave silos were put to use in new markets. Though the silo above was inspected regularly, buildings around the silo impeded the view of specific areas. In this case, the silo failed due to rusted steel galvanized hoops around the silo. The deterioration and inaccessible location of the hoops meant the structural member eventually broke and caused the collapse. It is imperative that stave silos be inspected regularly to ensure their safe operability. A collar wall, utilizing reinforced, poured in place concrete Jumpform technology, was added to the three silos above to add structural integrity and prevent additional wall failure. A unique solution was engineered based on the customer’s specific application. Using the existing foundation, a new steel reinforced concrete wall was implemented around the full circumference of the silo from grade to top. All penetrations and openings were placed for this application to operate as efficiently and safely as possible. Repairs of this nature are not inexpensive; however, they are more cost effective than building an entirely new silo for changing applications and markets. It is imperative that stave silos be inspected regularly to ensure their safe operability. As times change and new factors are integrated with an older structure, modifications should be considered at the same time for safety and efficiency.
Cement Silo Repair – Virginia
Market: Manufacturing Material Stored: Cement Silo Size: 27′ diameter by 110′ tall Issue: Potential roof collapse Project Background Silo beam pocket. Pictured above is a silo beam pocket, the beam rests on a bearing plate and supports the roof slab. This situation was found during a regular inspection of the silo structure. Beam pockets are a critical point on the silo as they support the roof slab and all the necessary equipment to operate the bulk storage system. The beam end sits on the thick, steel bearing plate, however, the concrete under the plate is spalling leaving this beam pocket at risk for failure. This particular pocket has been cleaned and drilled to receive the required steel reinforcement per professional engineer instruction. The engineered solution to reestablish the structural integrity of the beam pocket. The spalled area above has the engineered solution to reestablish the structural integrity of the beam pocket. First, the roof beam must be lifted off of the beam pocket and bearing plate to allow for repairs. Once this is accomplished, repair work can commence. Structural steel is placed per engineer specifications to ensure the integrity of the repaired beam pocket. A high strength, non-shrink grout is used to patch the spalled area. Lastly, a high strength, non-shrink grout is used to patch the spalled area. After the non-shrink grout has properly cured, the roof beam can then be lowered back into position on the bearing plate. Once the pocket is repaired, the silo roof is structurally sound and safe for use.
Aggregate, Sand and Gravel Stave Silo Repair – Alabama
Market: Manufacturing Material Stored: Aggregate, sand and gravel Silo Size: 28′ diameter by 50′ tall Issue: Cracking and broken staves Project Background A silo constructed with concrete staves and steel galvanized hoops. Pictured above is a concrete stave silo with steel galvanized hoops for structural integrity. The silo shows cracking and stave breakage along the top edge at the roof. On this silo, the conveyor loading system was designed to attach at the roof edge. This connection to the first two silos coupled with standard movement and settling over time led to the cracking issues. Pictured below are the silos after the cracked and broken staves were repaired. The walls were stabilized in the affected areas first. Steel wire mesh was attached to the surrounding staves that were not damaged. Then 4” of gunite was added around the circumference of the silos to make the repaired area the same size before adding the structural steel, tensioned hoops. Lastly, to ensure that the repairs would last and the conveyor would not cause repetitive issues, a new design for attachment was configured by a professional, licensed silo engineer. Silos after the cracked and broken staves were repaired.
Silo Repair of Cracking Silo Pedestal – West Virginia
Market: Cement Material Stored: Cement Silo Size: 30′ diameter by 60′ tall Issue: Cracking silo pedestal Project Background Three stave silos that were constructed on a pedestal structure. Pictured above are three stave silos that were constructed on a pedestal structure to allow for gravity discharge out of the bottom center of the silos. These silos are currently in good operating condition, however, the pedestal is in need of repair as it is displaying significant cracking along the horizontal members. Repair in process. Pictured above and below is the repair in process. First, the cracks are injected with epoxy to eliminate any voids in the concrete structure. Once this is complete, the surface is prepared to receive a three-phase application process of composite fiber reinforcement. When correctly applied, the composite fiber reinforcement will return the concrete support structure to its original strength. Repair in process. It is imperative that all material handling equipment at any facility be inspected regularly to ensure safe, efficient operation.
Clay Powder Silo Roof Repair – Georgia
Market: Manufacturing Material Stored: Clay Powder Silo Size: 26′ diameter by 56′ tall Issue: Detached roof Project Background A silo constructed with concrete staves and steel galvanized hoops. In this example, the concrete stave silo pictured above was modified from a bucket conveyor for filling material into the silo to a pneumatic filling system. This silo was not engineered for the additional pressure and was not modified correctly to accept this change of loading equipment. As a result, the roof of the silo actually lifted up and detached from the silo wall. Pictured below are the silos after they were repaired. The clay powder that filled the void between the roof and the wall had to be removed. Once that was complete the roof had to be reanchored to the silo walls as in new construction. To minimize or eliminate the issue, relief was added to each of the silos to release pressure during the loading process. Silos after they were repaired.