1.What is a spiral silo?
A spiral silo, also known as a Lipp silo or spiral steel silo, is a cylindrical storage facility constructed using a special spiral undercutting process. This technology originated in 1968, when German engineer Lipp invented it. The first spiral silo was built in Germany in 1969, and its unique structural advantages have since spread globally.
The core feature of this storage facility lies in its continuous spiral forming process: galvanized steel strips are spirally raised and undercut using specialized equipment to form a single-piece silo wall, eliminating the need for traditional welding or bolting. This provides two significant advantages: first, a smooth, flat interior wall prevents material accumulation and simplifies cleaning; second, it offers exceptional airtightness. The spiral undercutting structure effectively isolates air and moisture, meeting moisture-proof, insect-proof, and airtight storage requirements. Currently, spiral steel plate storage silos are widely used in various fields, including grain storage, cement storage, fly ash recovery, feed processing, and chemical raw material storage. They are particularly suitable for industrial scenarios with high storage requirements and rapid construction. Their diameter can be flexibly adjusted between 3 and 25 meters, with a maximum height-to-diameter ratio (the ratio of the silo’s height to its diameter) of 5.75. A single silo can hold up to approximately 6,500 tons, adapting to storage needs of varying scales.
2.What Equipment is Required to Build a Spiral Steel Silo?
The construction of a spiral steel plate storage silo relies on a highly integrated suite of specialized equipment that works together to achieve automated, continuous forming. The core equipment and functions are as follows:
Decoiling Machine: Serves as the starting point for raw material supply, responsible for smoothly unwinding the coiled galvanized steel sheet (typically 495mm wide), ensuring wrinkle-free and undistorted conveying during sheet transportation, providing a stable source of raw material for subsequent forming.
Forming Machine: Performs the initial shaping of the steel sheet. Based on the designed silo diameter, the uncoiled flat steel is bent into a curved profile that conforms to the curvature of the silo wall. The steel plate surface is also pre-treated to ensure the precision and strength of the subsequent undercutting.
The Bending Machine: This core equipment in spiral silo construction. The curved steel plates processed by the forming machine undergo a secondary processing step. Through an integrated bending-interlocking-rolling process, the edges of adjacent steel plates are tightly interlocked to form a continuous spiral rib 30-40mm wide. This rib structure effectively forms a reinforcement layer five times the thickness of the steel plate on the outside of the silo wall, significantly increasing the overall load-bearing capacity of the silo.
Load-Bearing Brackets & Running Frames: Serving as the supporting framework during construction, the load-bearing brackets secure the silo’s forming position, while the running frames drive the steel plates’ spiral upwards, ensuring the silo rises vertically and without deviation during construction. Furthermore, the roller system on the running frames reduces friction while the steel plates move, ensuring continuous construction efficiency. This equipment combination automates the entire process from raw material input – forming – undercutting – rising, eliminating significant manual intervention. This is a key factor in ensuring the rapid and precise construction of spiral silos.
3.Main Components of a Spiral Storage Steel Silo System
A complete spiral storage steel silo system consists of the silo structure and auxiliary components. These components work together to ensure the silo’s durability, safety, and functionality. These components include:
Roof and Platform System: This includes the roof cover, top guardrails, maintenance ladders, and operating platforms. The silo roof features a curved or tapered design to prevent rainwater accumulation; the guardrails and ladders ensure safety during maintenance, while the platform provides access for overhead equipment installation (such as ventilators and feed ports).
Wall Structure: This core load-bearing component is composed of standard galvanized steel slats, vertical stiffeners, circular stiffeners, and sealing materials. Standard steel slats are spirally undercut to form the main silo wall. Vertical stiffeners are installed close to the inside of the silo wall to enhance the silo’s resistance to lateral pressure. Circular stiffeners are spaced at regular intervals to further enhance silo wall stability. Sealing material fills the undercut gaps to enhance airtightness.
SiloEntry and Exit and Ventilation System:These include manholes in the silo wall (for easy access and maintenance), ventilation holes (to regulate air circulation within the silo), and temperature gauges (to monitor material temperature in real time). Some large silos are also equipped with induced fan bases and outlet elbows to optimize ventilation efficiency.
Auxiliary Components: These components include inter-silo corridors (used when connecting multiple silos), fixing bolts (connecting the silo to the foundation), silo sealant (filling gaps to prevent leaks), and electrical pipelines (powering the automated equipment). Although these components may seem inconspicuous, they are the detailed support that ensures the long-term and stable operation of the silo.
The design and installation of each component are focused on safe storage and convenient maintenance, forming a structurally complete and functional storage system.
4.Construction Sequence of Spiral Storage Silos
Unlike traditional buildings, which are constructed from the bottom up, spiral storage steel silos utilize a reverse construction method, building from the top down. The specific process is as follows:
First, Build the Roof and Top Protective Structure: Initially, the roof cover, top guardrails, and maintenance platform are fabricated and installed. This step is crucial to ensuring the roof structure is stable, providing a top support point for the subsequent spiral ascent of the silo.
Spiral Ascent and Forming of the Silo: Starting with the installed roof, a forming machine and a biting machine work together to roll galvanized steel strips downward from the top in a spiral. With the continuous biting and conveying of the steel strips, the silo gradually extends downward, creating the visual effect of the silo slowly growing from the top.
Stepwise Installation of Reinforcement Ribs to Ensure Vertical Bearing Capacity: As the silo spirals downward, vertical reinforcement ribs are installed on the inside of the silo walls. Typically, a ring of stiffeners is installed every time the silo rises (or falls) a certain height (e.g., 2-3 meters). This process of forming and reinforcing sections ensures the silo maintains sufficient vertical load-bearing capacity during construction, preventing deformation due to its own weight.
After The Silo Reaches The Designed Height, It Rotates And Falls Into Place: When the silo reaches the designed height, the steel plate feeding and undercutting operations are stopped. The running frame is fine-tuned to rotate the entire silo until it is aligned with the foundation. The silo is then slowly lowered, ensuring the bottom of the silo is precisely aligned with the embedded foundation components.
Welding and Finishing: The bottom of the silo is securely welded to the embedded foundation components. The ring stiffeners are also welded to the foundation connection points to enhance the silo’s anti-overturning capacity. If multiple silos are being constructed and require corridors, the corridors are connected during the construction of the individual silos, eliminating the need for high-rise scaffolding, reducing the risk of working at height. Furthermore, the pre-formed silo roof protects subsequent construction from weather conditions, significantly improving construction efficiency.
5.Detailed Construction Process for Spiral Storage Silos
Based on a clear construction sequence, on-site construction must adhere to the principles of precise positioning, continuous control, and step-by-step acceptance. The detailed process is as follows:
Foundation Inspection and Embedded Parts Verification: Before construction, first check that the flatness and strength of the silo foundation meet the design requirements. Also, verify the position, quantity, and dimensions of the embedded parts on the foundation. Embedded parts are the key to connecting the silo to the foundation, and positional deviations must be controlled to the millimeter level, otherwise they will affect the subsequent silo placement.
Positioning and Laying Out Lines to Determine Equipment Positions: Using the foundation center point as a reference, plot the silo centerline and equipment installation control lines. Based on the designed silo diameter, determine the installation positions of the uncoiler, forming machine, and running frame, ensuring that the centerlines of each piece of equipment align with the silo centerline to provide a precise reference for subsequent continuous forming.
Installing The Forming Equipment And Top Platform: Secure the uncoiler, forming machine, and biting machine according to the laid-out positions. Simultaneously, install the load-bearing brackets and running frame, and securely connect the prefabricated top platform to the running frame. At this stage, the equipment’s operating accuracy must be adjusted to ensure smooth steel plate conveying and uniform edge-biting pressure.
Raw Material Conveying and Continuous Roll-Forming: A 495mm-wide galvanized steel coil is loaded onto the uncoiler. After the equipment is started, the steel plate passes through the uncoiler for flattening, the forming machine for bending, and the edge-biting machine for forming. The result is a silo wall steel strip with 30-40mm wide spiral ribs. Driven by the running frame, the steel strip spirals downward from the silo roof, gradually forming the silo body.
Simultaneous Installation of Reinforcement Ribs and Roof Fixation: When the silo body has descended to approximately 1 meter, the equipment is stopped. The roof and silo body are first welded together to prevent displacement. The first ring of vertical reinforcement ribs and circular stiffeners are then installed, securely fastened to the silo wall with high-strength bolts. The equipment is then resumed, and reinforcement installation is repeated every 2-3 meters of descent, completing the roll-forming and reinforcement fixation cycle until the silo body reaches the designed height.
Cutting Steel Plates and Creating Manholes: After the silo reaches the designed height, the galvanized steel strips are cut, and manholes are cut into the silo wall at the pre-set location (usually located in the lower middle of the silo for easy access). After cutting, the cuts are polished and treated with anti-rust treatment to prevent corrosion of the steel plates.
Silo Lowering and Foundation Welding: The silo is slowly lowered using the hydraulic system of the running frame, allowing the bottom of the silo to precisely align with the embedded foundation components. After alignment, welders fully weld the bottom of the silo to the embedded components to ensure connection strength. Circular reinforcements are also welded to the foundation support triangles to further enhance silo stability.
Removing Temporary Equipment and Cleaning: After welding is completed and inspected, temporary equipment such as the uncoiler, forming machine, and running frame are removed, and waste and debris are cleared from the construction site. Finally, the silo wall surfaces are cleaned, and the sealing of the undercut seams is inspected. Sealant is added if necessary to complete the main silo construction.
The entire construction process relies on mechanized, continuous operations, requiring strict precision control at every step. For example, the undercut depth deviation must be ≤1mm, and the verticality deviation of the silo must be ≤1‰. This precise, automated construction method reduces the construction period of spiral silos by over 50% compared to traditional reinforced concrete silos.
6.Installation of Supporting Systems
After the main structure of the spiral storage steel silo is completed, supporting systems must be installed to complete the entire storage, conveying, and management process. These primarily include the following:
Material Conveying System: Responsible for the inflow and outflow of materials, including infeed equipment (such as belt conveyors, air cushion belt conveyors, bucket elevators, and ship unloaders) and outfeed equipment (such as scraper conveyors, cage screw conveyors, truck loaders, and packaging machines). These equipment must be selected based on the material’s characteristics (e.g., granular or powdery) to ensure efficient conveying and material integrity.
Weighing and Measuring System: Used to measure the weight of materials entering and leaving the silo, these systems include floor scales, truck scales, rail scales (for rail transportation), and electronic platform scales (for small materials). Some systems are also equipped with online weighing sensors for real-time material weight monitoring and data upload.
Ventilation and Dust Removal System:Ensures safe storage of materials within the warehouse, including ventilation fans (to regulate temperature and humidity), dust collectors (to collect material dust and prevent contamination), and filters (to filter out airborne impurities). Dehumidification equipment is also provided for moisture-sensitive materials to prevent clumping and deterioration.
Automated Control System:Enables intelligent warehouse management, including a control panel (centralized operation), monitoring sensors (temperature, humidity, and material level sensors), safety alarms (automatic alarms for over-temperature and over-level), and a remote monitoring module (supporting remote monitoring of warehouse status via mobile phone or computer).
The installation of supporting systems must be planned in parallel with the silo construction to avoid damage to the silo structure due to subsequent modifications. The coordinated operation of these systems can transform spiral silos from simple storage containers into intelligent storage units, significantly improving storage efficiency and ease of management.
7.Advantages of Spiral Storage Silos
Compared to traditional reinforced concrete silos or ordinary welded steel silos, spiral storage silos offer significant advantages, primarily in the following aspects:
Lightweight, High-Strength, and Excellent Load-Bearing Capacity: Made from galvanized steel sheets, while the steel sheets are relatively thin (typically 1.5-3mm), the ribbed structure created by the spiral undercut significantly enhances the silo wall strength. The overall load-bearing capacity far exceeds that of ordinary steel silos of the same thickness, easily withstanding the weight of materials and external wind pressure.
Fast Construction and Short Turnaround Time: Utilizing a fully mechanized continuous forming process, a spiral silo with a diameter of 10 meters and a height of 20 meters can be completed in just 7-10 days, 2-3 times shorter than a traditional concrete silo. This makes it particularly suitable for projects with tight deadlines. Excellent airtightness and a controlled storage environment: The 30-40mm wide spiral undercut, combined with sealant filling, achieves a near-zero-leakage seal, meeting the stringent airtight storage requirements of grain, chemical raw materials, and other applications, effectively preventing moisture, oxidation, and contamination.
Long Service Life and Low Maintenance Costs: Galvanized steel offers excellent corrosion and weathering resistance, and with normal use and maintenance, it boasts a service life of over 30 years. The smooth interior, free of dead corners, makes cleaning easy, requiring only a brief annual inspection of the seals and corrosion protection. Maintenance costs are significantly lower than those of concrete silos.
Smooth Interior Walls and Minimal Material Residue: The spiral forming process creates a smooth interior with no protruding joints, preventing material from clinging to the silo. This reduces waste and mitigates the risk of cross-contamination caused by moldy residual materials, making it particularly suitable for applications where stored materials are frequently rotated. Cost-Effective and High Performance: Firstly, the use of galvanized steel sheets is approximately 30% less than that of traditional silos, resulting in lower raw material costs. Secondly, mechanized construction reduces labor requirements, reducing labor costs by over 40%, making the overall construction cost significantly lower than that of a concrete silo of similar size.
Aesthetically Pleasing and Suitable For Industrial Environments: The continuous and uniform spiral lines give the silo a modern industrial aesthetic that blends seamlessly with the overall environment of factories and storage parks, avoiding the “bulky and crude” visual effect of traditional silos.
8.Conclusion
Spiral silos, with their unique reverse construction and continuous forming process, perfectly combine mechanical precision, structural strength, and construction efficiency, addressing the challenges of traditional storage facilities, such as long construction times, high costs, and poor sealing. Their lightweight, high strength, rapid construction, and long-lasting durability make them an ideal choice for efficient storage in industries such as grain, cement, and chemicals.
If you require a customized spiral silo design for your specific storage needs, or would like to learn more about the technical specifications and costs of silos of different sizes, please feel free to contact us. We will provide you with a professional, one-stop solution.