Spiral Silo
Specifications
1
Basic Dimensions and Forming Parameters
Our spiral silos enable an est. flexible storage capacity of 500 – 25,000 ton/silo. With an ability to support up to 35 m in height and 40 m in diameter, our silos are adequate for cement, fly ash, grains, and other bulk material storage in virtually any region of the world.
| Parameter | Specification/Range | Description |
|---|---|---|
| Body Diameter | 3 – 40 m | From small to ultra-large capacity requirements |
| Body Height | ≤ 40 m | Height-to-Diameter Ratio 1.0:1 ~ 1.5:1 |
| Strip Width | 495 mm, 625mm, 750mm | A variety of optional spiral strip widths |
| Plate Thickness | 2.0 – 6.0 mm | 4–6 mm for Dia > 20m or heavy materials |
| Spiral Rib Width | 30 – 50 mm | Enhanced structural rigidity |
| Forming Speed | 3 – 5 m/min | High-efficiency on-site construction |
| Optimal H/D Ratio | 1.5 : 1 | Ensures structural stability |
Technical Highlights
- For Diameter >20 m: We suggest the use of 40 mm spiral ribs with 4 - 6 mm steel plates for walls to control hoop stresses and wall deformations.
- For silos storing heavy and/or abrasive materials: We recommend the use of steel plates of at least 8 mm thickness.
- For height/diameter (H/D) ratio greater than 1.5: Add external supports or stiffeners.
- Forming Speed: Limit on-site forming speeds to 3 – 5 m/min to maintain quality of the joints and to ensure long-term airtightness.
2
Material and Structural Specifications
The grade of steel and the type of anti-corrosion systems can be modified based on the type of storage media bulk storage system utilize, humidity in the environment, and the expected lifespan of the project.
| Parameter | Specification Range | Description |
|---|---|---|
| Steel Grade | Q235 / Q345 / Hardox / 304 / 316 | Selected based on capacity and environment |
| Yield Strength | 235 – 550 MPa | Adapts to various stress requirements |
| Seaming Depth | 11-31 mm (Lip ≥ 5×thickness) | Ensures spiral seam airtightness |
| Anti-corrosion | Polyurethane / Epoxy Coating | Optional Vinyl Ester/Fluoropolymer for harsh environments |
| Galvanized Level | Z-275 / Z-450 / Z-600 / Verinox | Selected by humidity and corrosivity |
Technical Highlights
- For large diameter or tall silos: We suggest the use of Q345 steel, use Hardox for silos storing abrasive materials, and use 304 or 316 stainless steel for silos in corrosive environments.
- To control air leaks and water ingress: The seam depth should be equal to or greater than 5 times the thickness of the plate, or at least 15 mm.
- In coastal or highly chemical environments: Replace standard epoxy systems with Z-600 galvanizing and choose vinyl ester or fluorocarbon coatings.
- For dry, inland areas: Use Z-275 for galvanizing, while in coastal or highly salting areas, use Z-600 or Verinox coatings for prolonged service.
3
Capacity and Investment Reference
Spiral silo systems provide a cost-efficient solution for medium and large-capacity bulk storage with fast construction and scalable expansion.
| Unit Capacity (t) | Diameter (m) | Total Height (m) | Footprint (m²) | Investment (USD) |
|---|---|---|---|---|
| 500 | 7 | 14 | 38.5 | $37,000 – $59,000 |
| 1,000 | 10 | 14 | 78.5 | $52,000 – $81,000 |
| 5,000 | 18 | 22 | 254.5 | $89,000 – $133,000 |
| 10,000 | 22 | 26 | 380.2 | $178,000 – $237,000 |
Technical Highlights
- Centered Investment: Centralized large-capacity silos mean large storage silos have a lower cost-per-ton capacity which makes centralized storage a better use of infrastructure and equipment investments.
- Space Maximization: The larger the silos the less floor space is needed per ton of storage, making larger silos the better option when space is constrained.
- Height and Budget Variability: Small-capacity silos offer larger height variability, while large-capacity silos offer a more predictable budget.
- Economy of Scale: A 10,000-ton class spiral silo optimizes storage land and cost for either new storage or expansion of existing storage.
4
Construction and Maintenance
There is a large reduction in construction, maintenance, and labor costs with the use of spiral steel silos over concrete or welded silos.
| Parameter | Value | Impact on Investment/Construction |
|---|---|---|
| Construction Period | 3 – 15 days/silo | Climbing method saves ~20% labor costs |
| Base Load | 15 – 30 t/m² | Pile foundation needed for poor soil (+10% cost) |
| Maintenance Cycle | Annual inspection, 25 year lifespan | Annual maintenance cost < 0.5% of investment |
| Seismic Rating | 9 Degree, Wind Load 4 kN/m² | Reinforcement required for high-risk zones (+5% budget) |
Technical Highlights
- Construction Speed and Labor: Because labor costs are reduced by approximately 20% due to silo construction which occurs in 3-15 day intervals, the rapid formation of silos works well for fast-track construction.
- Foundation Adaptability: Civil costs are reduced due to the standard load of 15-30 t/m². Soft soil may require a pile foundation with budget adjustments.
- Cost Control over Lifecycle: Long term costs are controlled due to a large service life of 25 years and annual maintenance costs under 0.5% of the total investment.
- Wind and Seismic Design: Standard designs allow for4 kN/m² wind load and 8-degree seismic protection. For high risk areas, budgets should account for additional design requirements.
5
Material-Specific Silo Design
At Neorigin Silo Gropu, the design of silos is tailored to a specific material so that the silo structure, flow system and discharge design can be the most effective.
General Material Guidelines
| Material Type | Bulk Density Range | Rec. Thickness (mm) | Special Design Requirements |
|---|---|---|---|
| Grain | 0.70 ~ 0.75 t/m³ | 2.0 – 6.0 mm | External stiffeners to prevent accumulation |
| Cement | 1.10 ~ 1.25 t/m³ | 2.5 – 6.0 mm | Powder flow characteristics and anti-blocking discharge system |
| Fly Ash | 1.30 ~ 1.50 t/m³ | 2.5 – 6.0 mm | |
| Mineral Powder | 1.50 ~ 2.20 t/m³ | 2.5 – 6.0 mm | |
| Lump Ore ≤80mm | 1.50 ~ 2.8 t/m³ | 2.5 – 6.0 mm | Internal wear-resistant lining |
Specific Hopper Design Parameters
| Material | Typical Bulk Density (t/m³) | WALL FRICTION ANGLE (°) | RECOMMENDED HOPPER HALF-ANGLE |
|---|---|---|---|
| Wheat | 0.75 t/m³ | 24 – 28 | ≥ 35 |
| Paddy (Rice) | 0.58 t/m³ | 22 – 26 | ≥ 35 |
| Corn | 0.72 t/m³ | 22 – 26 | ≥ 35 |
| Cement Powder | 1.20 t/m³ | 25 – 35 | ≥ 45 |
| Fly Ash | 1.45 t/m³ | 28 – 38 | ≥ 50 |
| Mineral Powder | 1.80 t/m³ | 30 – 40 | ≥ 55 |
| Lump Ore ≤80mm | 1.60 t/m³ | 35 – 45 | ≥ 60 |
Technical Highlights
- Material Density vs. Plate Thickness: To avoid silos with large density (≥1.5 t/m³, including mineral powder and lump ore ≤80mm) from high abrasion wear, silos should be constructed of thicken steel sheets (≥ 4 mm) which should be lined with wear resistant linings.
- Friction Angle & Hopper Design: Materials that easily form bridges, like rice or corn, need a minimum hopper half-angle of 35° for smooth flow. On the other hand, dry wheat with a wall friction angle of 24°–28° works well with standard conventional conical hoppers without extra flow aids..
- Storage for Cement & Fly Ash: Design silos for fly ash and cement to be airtight and moisture proof. Incorporate fluidization to reduce the caking of powders and facilitate discharge.
- Grain Storage Design: Use external stiffeners to avoid the retention of product in the silo and subsequent spoilage. Combine with a 3 to 4 mm thick plate to optimize cost and strength.
6
Steel Grades
A wide range of galvanized and stainless steel options are available to match different corrosion and storage conditions.
6.1 Galvanized Steel Levels
| Level | Coating (g/m²) | Environment |
|---|---|---|
| Z-275 | 275 | Dry indoor / Regular Agri |
| Z-450 | 450 | Outdoor general industrial |
| Z-600 | 600 | Coastal / Corrosive |
| Verinox | Composite | Zinc outer + SS304 inner |
6.2 Structural Base Metal
| Grade | Yield Point | Best Use Case |
|---|---|---|
| Q235B | 235 MPa | Common welded silos |
| Q345B | 345 MPa | High capacity / Main structures |
| 304 / 304L | 205 MPa | Food grade / Anti-corrosion |
| 316 / 316L | 170 MPa | Chemical / Chloride environment |
Technical Highlights
- Steel Strength Selection: Use Q345 (345 MPa yield strength) steel for large capacity or tall silos. For standard silos of medium or small capacity, use Q235B.
- Galvanization by Environment: For inland agricultural use, use Z-275. For coastal and other corrosive environments use Z-600 or long-term corrosion resistant Verinox coatings.
- Stainless Steel Selection: For food grade and mild corrosion use 304/304L, and use 316/316L for chloride or chemical corrosion.
- Composite Coating Advantage: For humid and material corrosive and coatings, Verinox combines corrosion resistance and cost.