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IS 9178:2000 (Part 2) is the Indian Standard (BIS) for criteria for design of steel bins for storage of bulk materials, part 2: design criteria. This standard provides criteria for the structural design of steel bins for storing bulk materials, focusing on achieving desired flow patterns. It outlines the design methodology for both mass flow bins, where all material moves during discharge, and funnel flow bins, where a channel forms within stagnant material. The code details the application of Janssen's and Jenike's theories to calculate material pressures and determine hopper geometry.
Criteria for Design of Steel Bins for Storage of Bulk Materials, Part 2: Design Criteria
Overview
Status
Current
Usage level
Specialized
Domain
Structural Engineering — Structural Engineering and Structural Sections
BIM-relevant code. See the BIM Hub for ISO 19650, IFC, and LOD/LOIN frameworks used alongside it.
Practical Notes
! Accurate measurement of the bulk material's properties (like angle of internal friction, wall friction angle, and bulk density) via laboratory testing is critical for a safe and functional design; using assumed values is highly discouraged.
! Mass flow design avoids many flow problems like 'ratholing' but results in higher wall loads, particularly a 'switch' pressure at the cylinder-hopper transition, which must be accounted for.
! Funnel flow is simpler and imposes lower loads but is only suitable for coarse, free-flowing, non-degrading materials where first-in-first-out flow is not required.
Consolidated list per BIS. For the text of each amendment, refer to the BIS portal link above.
steelbulk materials
International Equivalents
Similar International Standards
EN 1991-4:2006European Committee for Standardization (CEN), Europe
HighCurrent
Eurocode 1: Actions on structures - Part 4: Silos and tanks
Provides principles and rules for the determination of actions from granular solids in silos and tanks.
AS 3774-1996Standards Australia, Australia
HighCurrent
Loads on bulk solids containers
Specifies methods for determining loads for the design of containers used for the storage of bulk solids.
ANSI/ASCE/AISC/ASABE 722-21American Society of Civil Engineers (ASCE), USA
MediumCurrent
Standard for Design of Bins, Hoppers, Silos, and Bunkers
Provides a comprehensive standard for structural design, including detailed load assessment methods.
DIN 1055-6:2005Deutsches Institut für Normung (DIN), Germany
HighWithdrawn
Actions on structures - Part 6: Design loads for buildings and loads in silo bins
Served as a foundational standard for silo loads in Germany and heavily influenced the Eurocode.
Key Differences
≠IS 9178 uses a single discharge load factor (C_d) to increase filling pressures for discharge conditions. In contrast, EN 1991-4 uses a more complex system of over-pressure factors (C_h for horizontal pressure, C_w for wall friction) and considers specific flow patterns (mass flow vs. funnel flow).
≠EN 1991-4 explicitly requires the calculation and application of non-uniform 'patch loads' to account for flow imperfections, especially in slender silos. IS 9178 does not have a similar mandatory requirement for a distinct patch load case.
≠For eccentric discharge, IS 9178 recommends a simplified approach of increasing the symmetrical pressure by 25% over one-quarter of the circumference. International standards like EN 1991-4 and AS 3774 provide detailed methods for calculating the magnitude and distribution of a non-uniform pressure patch based on the eccentricity.
≠EN 1991-4 provides detailed guidance and specific calculation methods for thermal loads arising from temperature differences between the stored material and the silo wall. IS 9178 acknowledges thermal effects but provides less quantitative guidance for their calculation.
Key Similarities
≈All standards, including IS 9178, use Janssen's theory as the fundamental basis for calculating horizontal pressures in the vertical (cylindrical or prismatic) section of the silo during filling.
≈A clear distinction is made in all standards between loads during filling (static) and loads during discharge (dynamic). All mandate the use of higher, magnified pressures for the discharge condition to ensure safety.
≈The concept of calculating vertical frictional load on the silo wall as a product of the horizontal pressure, the coefficient of wall friction, and the wall surface area is a common principle across all mentioned standards.
≈All standards recognize that pressures in the hopper section are significantly different from the barrel and that a pressure peak typically occurs at the transition between the vertical section and the hopper.
Three classes: Slender (h_c/d_c > 2.0), Intermediate (1.0 < h_c/d_c ≤ 2.0), and Squat (0.4 < h_c/d_c ≤ 1.0).
EN 1991-4:2006
Discharge Load Factor (Hopper Wall)
A single factor 'C_d' is used, typically ranging from 1.4 to 1.6.
An over-pressure factor 'C_h' is applied, whose value depends on silo class, hopper geometry, and flow pattern.
EN 1991-4:2006
Pressure Ratio (K = p_h/p_v)
Calculated using Rankine's theory, e.g., K = (1 - sinφ) / (1 + sinφ). A single value is typically used.
Different values are used for filling (K_0) and discharge (K_e), with values provided in tables based on silo slenderness and wall roughness.
EN 1991-4:2006
Eccentric Discharge Pressure Model
Symmetrical pressure increased by 25% over 1/4 of the perimeter (Clause 6.3.3.1).
Application of a defined external pressure patch (p_pe) with a specific magnitude and area (Clause 5.4.3).
EN 1991-4:2006
Hydraulic Radius (R)
Area of horizontal cross-section / Perimeter of horizontal cross-section (A/U).
Area of horizontal cross-section / Wetted perimeter of horizontal cross-section (A/U).
EN 1991-4:2006
Coefficient of Wall Friction (μ)
A single mean value is selected from tables for a given material-wall pair.
Upper and lower characteristic values are defined. The upper value is used to maximize horizontal pressure, while the lower value is used to maximize vertical wall friction load.
EN 1991-4:2006
⚠ Verify details from original standards before use
Key Values5
Quick Reference Values
Janssen's pressure ratio 'K' (typical)0.4 to 0.6
Mass Flow Hopper Angle Condition (Conical)α < f(wall friction angle)
What is the main difference between mass flow and funnel flow?+
In mass flow, the entire contents of the bin move during discharge, ensuring first-in-first-out flow. In funnel flow, a flow channel forms above the outlet with stagnant material at the periphery (Clause 4).
How do I calculate the pressure on the vertical silo wall?+
Use Janssen's theory (Clause 8), where vertical pressure is a function of depth, and horizontal pressure is the vertical pressure multiplied by the Janssen ratio 'K'.
How do I determine the minimum outlet size for a mass flow bin?+
The minimum outlet dimension must be large enough to prevent the formation of a stable cohesive arch. It is calculated using Jenike's theory based on the material's critical stress for arching (σ_cr) and flow factor (Clause 6.3).
What causes 'switch' pressure?+
During the onset of flow in a mass flow bin, the stress field shifts, causing a localized high-pressure zone near the transition from the vertical section to the hopper. This must be considered in the structural design (Clause 8.4).