CENTRE FOR BULK SOLIDS AND PARTICULATE TECHNOLOGIES
MECH XXXXXXXXXX
Assignment 3 – Wall loads and feeder design
Alignment with Course Learning Outcomes: This assignment aligns with the following Course
Learning Outcomes:
• Determine the stress distribution within a particulate system in symmetrical silos and bins
• Compute feeder and gate loads for defined cases
Instructions: Conceptually determine bin wall loads and design a belt-apron feeder
Assessment Criteria: This assignment is worth 30% of the total course assessment. The focus will be on
a demonstration of a clear understanding of the technical issues within the tasks. However, a reasonable
standard of presentation is expected. That is, neat and tidy with all graphs appropriately labelled and an
explanation of the process given to demonstrate a clear understanding of the tasks undertaken.
Q1 Silo Wall Loads
The axi-symmetric (conical) silo of Figure 1 is designed to handle GOLD ORE at 7.2% moisture
content. You are asked to determine:
(a) The initial vertical and normal wall pressures as a function of bin height during filling of the
silo using the methodology presented in Australian Standard AS XXXXXXXXXX.
For the cylindrical section of the silo is k = 0.37.
For the hopper section, the pressure ratio is
given by
khi =
tan α
tan α + tan φw
(b) The vertical and normal wall pressures as a
function of bin height for the flow case in
accordance with AS3774, but using the
modified khf value for the hopper pressures as
given by:
khf(mod) =
2 (1 + sin δ cos 2η)
2 - sin δ(1 + cos 2(α + η))
For the normal pressures on the cylinder walls
during flow, the over-pressure factor (cnf) based on
the Janssen pressure should be used (Refer to notes)
The following information is given:
Wall friction angles -
φw for Mild Steel = 34°
φw for Arcoplate = 23°
Effective angle of internal friction δ = 52°
Bulk density, XXXXXXXXXXρ = 1850 kg/m3
The angle of repose of the GOLD ORE is 38°. The silo is initially centre filled.
NOTE: The wall load results determined are to be plotted against the height of gold ore in the silo.
All parameters used for calculating the wall loads are to be provided.
Figure 1. Gold ore bin
12
m
0.8 m Dia
10 m Dia
25o
38o
Hopper Lining:
Arcoplate
Cylinder:
Mild Steel
Q2. Apron feeder design
A plane flow hopper is proposed for delivering gold ore from a course ore stockpile. This hopper
is to provide feed to a processing plant at a controlled throughput of 2000 t/hr using a belt feeder
inclined at 8⁰. The bin opening and hopper half angle chart is shown in Figure 2.
The following parameters are known from flow property test and design constraints:
• Distance between top of hopper and belt feeder: 4m
• The vertical surcharge pressure (Ps) at the top of the hopper is 140 kPa
• Maximum Belt Feeder Speed: 0.35 m/s
• Bulk Density: 1850 kg/m3
• Internal Friction Angle: δ=52°
• Hopper Liner Material: Arcoplate
• Optimum Hopper Gate Height to Width: 0.7
• Vertical End Walls
• Volumetric Efficiency of Feeder: 75%
• The projected ‘length’ to ‘front gate width’ aspect ratio of the outlet should be 3.5:1
• Particle Top Size: 40 mm
• Bulk Material is very moderately compressible.
Tasks:
1. Provide Basic Hopper Geometry for Mass Flow to the feeder
2. Develop Transition Geometry to ensure optimal draw down in the mass flow hopper
3. Calculate the Load Estimate required for the belt feeder
Figure 2. Hopper half angle (α) / Discharge rate (Q) Vs Outlet width (B)
for Gold Ore at 7.2% Moisture Content
Arcoplate
Bisalloy 360
NiHard