Design of Silo for Storing Rice

Welded Silos Specifications

I. SCOPE:

The following specifications cover the process for welded silo fabrication.

II. CODES:

These specifications are used in conjunction with the following codes:

• AISC - American Institute of Steel Construction
• AWS - American Welding Society
• UBC - Uniform Building Code
• FDA - Food and Drug Administration
• OSHA - Occupational Safety and Health Administration
• ASTM - American Society for Testing and Materials
• SAE - Society of Automotive Engineers
• SSPC - Steel Structures Painting Council

III. Design Criteria:

1. Standard wind design is for 100 MPH wind velocity based on the UBC 1999 Edition. Combined height, exposure and gust factor coefficient is based on Exposure B. A horizontal force shape factor of 1.4 is included.
2. Seismic design is based on UBC 1999 Edition. When designing a silo for a particular seismic zone, the load producing the highest stresses comparing wind and seismic forces will control the dynamic portion of the design.
3. Combined live, dead, and roof loads shall be uniformly distributed, with all nozzles, manhole and filter locations designed for a minimum of 200 lbs. concentrated load. Live and dead loads to be a combined minimum of 24 lbs. psf. Roof is not designed as a working platform. Standard roof will have a 10 degree slope for water drainage.
4. Silo design is based on the critical buckling formula from the book titled Structural Engineering Handbook by Gaylord and Gaylord (Boardman formula).
5. Silos are designed to atmospheric pressure as a standard. Silos are capable of withstanding normal pneumatic fill line pressures of 0.5 oz. per square inch vacuum and maximum of 4.0 oz. per square inch of pressure.
6. LEMANCO Welded Industrial Silo`s are designed for loads as follows: The silo may be filled to capacity with bulk materials at design unit weight having a material repose angle of 30 degree and a coefficient of friction of 0.7. This combination of material repose and friction coefficient results in a more severe condition than is normally likely to be encountered.
7. Loads are based on center discharge and near center fill. Other arrangements will alter design conditions.
8. Silos can be designed for either funnel flow or mass flow.
9. Due to the wide variation in Building and Zoning Codes and their interpretations, Chief Industries, Inc. does not warrant The Lemanco Product or collateral materials or equipment to comply with any Building or Zoning Code requirements, permit requirements, design procedure, design load, material or equipment requirements, fabrication procedure, or work procedure except those expressly provided herein or in the order. Costs of any additions, deletions, modifications, or changes that may be required to comply with any building or zoning code requirement, permit requirement, design procedure, design load, material or equipment requirement, fabrication or work procedures which are not expressly provided herein or in the order are paid by buyer. When the size, shape, general characteristics, or design are specified by the Buyer, the Seller is not responsible for the suitability, adequacy, or legality of the design.
10. Chief Industries, Inc. does not design and is not responsible for the design, materials or workmanship of the foundation unless agreed. The BUYER assures himself that adequate provisions are made in the foundation design for the loads imposed by LEMANCO PRODUCTS (See Anchor Bolt Plan for magnitude and direction of column reactions), or other imposed loads, and the soil bearing capacity and other conditions of the building site. Please note that all above design conditions were chosen to cover most standard situations. All other criteria can be evaluated per application and requirement.

IV. Material Specifications:

1. SHEET - Carbon steel shall conform to or shall be at least equal to ASTM 569 Commercial quality.
2. PLATE - Carbon steel plates 3/16" or thicker shall conform to or at least be equal to the requirements of ASTM A36 with a minimum yield strength of 36,000 psi.
3. ROLLED STRUCTURAL SHAPES - Rolled structural shapes shall conform to ASTM A36.
4. PIPE - Structural pipes shall conform to ASTM A53 Grade B.
5. BOLTS -
   A. Miscellaneous bolts are stainless steel and meet the minimum requirements of SAE Grade 5.
   B. Structural bolts meet the minimum requirements of ASTM A325.
6. HANDRAILS, LADDERS, SAFETY CAGES AND PLATFORMS -
   A. Handrails, ladders, cages and platforms are designed to meet OSHA requirements and are welded units to minimize field erection.
   B. Standard equipment includes aluminum handrails and carbon steel ladders, cages and rest platforms galvanized or painted.

V. Manufacturing Specifications:

1. WELDING
   A. When specified, all structural welding shall conform to the latest edition of AWS using AWS certified welders.
   B. Shell seams shall be a minimum of 85% penetration using .045 gauge ER70XX welding wire with a semi-automatic MIG Welder and copper backed internal sizing rings.
2. SURFACE PREPARATION
   A. All weld surfaces with sharp edges are ground, any undercuts will be repaired and ground. All weld spatter will be removed and exterior surfaces shall be grit blasted prior to painting per SSPC-SP7.
   B. Gritblasting per SSPC-SP 6 or SSPC-SP10 is available for interior or exterior walls when specified.
   C. SSPC-SP 10 near white is used for FDA applications. (All interior weld seams are ground flush)
3. COATINGS CARBON STEEL
   A. Silo exterior shall be coated (when required) with minimum 2.0 mils of rust inhibitive gray primer and 1.5 mils minimum of polyurethane finish coat. Epoxy coating up to 10.0 mils is available for interior or exterior coating when specified.

VI. Quality Control:

1. All welds are visually inspected for air holes, pinholes, undercut, penetration and satisfactory finish. Dye penetration inspection shall be performed on all liquid storage silos as standard (refer to testing data). All inspections are documented per Manufacturers Quality Control Policy and Procedures Manual.
2. Quality Control inspection points are placed at critical intervals during the manufacturing process.
3. Final inspection is made before and after loading for shipment with photographs.

Standard Silos Include

• Funnel flow design.
• 10 degree slope on deck roof.
• 20 inch diameter center fill dome with cover plate.
• 12 inch diameter flange discharge with 2 foot 6 inch clearance.
• 3 foot x 6 foot 8 inch steel access door with louver (on skirted tank, except when skirt height does not permit).
• Lifting lugs.
• Exterior primed with epoxy and top coated with polyurethane.
• Three sets of standard engineering drawings provided.
• Standard Hoppers.
• Standard silo diameters: 7, 8, 9, 10, 11.6, 12, 13, and 14 feet.
• Standard silo heights are in nominal 6 foot increments.
• Standard hoppers are symmetrical with outlet. Larger or smaller outlets are available per customer requirements.

I hope this will help