1. Off-Road Equipment Management TSM 262: Spring 2016
LECTURE 18: Materials Handling II
Off-Road Equipment Engineering
Dept of Agricultural and Biological Engineering

2. Homework and Lab

3. Materials Handling: Class Objectives
Students should be able to:
Explain the operation of pneumatic conveyors, bucket conveyors and forage blowers
Analyze the capacity and power requirements for a bucket conveyor
Explain the operation of forage blowers

4. Pneumatic Conveyors
Move grain by imparting the kinetic energy of air to grain in conduits
Advantages
Flexible
Low cost
Disadvantages
Require higher specific power compared to auger conveyor

5. Types of Pneumatic Conveyors
Negative pressure
Seldom used
“sucks” the material to destination
Positive pressure
“blows” the material to destination
Combination negative/positive
Vacuum draws the grain in
Positive pressure conveys material

6. Positive Pressure System
Air lock brings grain in
Positive pressure conveys material
Rotary Air Lock

7. Combination Negative/Positive Pressure System
Vacuum draws grain in
Positive pressure conveys material

8. Example
AFS-Air Filtering System
Cyclone
Blower

9. Examples

10. Components Air moving system Feeding system Discharge system
Pipelines and fitting

11. Bucket Elevators Vertical Conveying Capacity range: 7~350 m3/h
Uses inertial forces and gravity
Capacity range: 7~350 m3/h
Performance dependent on:
Head wheel speed
Head wheel diameter

12. Examples of Bucket Elevators
Centrifugal Discharge
Perfect Discharge
Heavy Duty Continuous Discharge

13. Force Diagram on Grains
At position 5 require that vertical forces on grain at center of bucket are zero
S = Centrifugal force
W= Weight of grain
R = Resultant force

14. Bucket Elevator Capacity
Q = V·v/s
V = bucket volume (m3)
v = belt speed ( m/s)
s = bucket spacing (m)

15. Bucket Elevator Power Must lift, scoop, and discharge material
Overcome friction
Actual Power, P = 1.1~1.15 Pt
Theoretical power requirement:
Pt = m·g·h/t = Q·rb·g·h
Pt = theoretical power (W)
Q = elevator capacity (m3/s)
rb = material bulk density (kg/ m3)
h = material lift height (m)

16. Class Problem
A bucket conveyor is to be used to convey shelled corn with a lift height of 35 m. The buckets have a capacity of 2.58x10-3 m3 and are spaced 150 mm apart. Bulk density of shelled corn is 719 kg/m3. Assuming a belt speed of 2.5 m/s calculate the following:
Elevator capacity, m3/s
Theoretical power , kW
Actual power assuming 15% safety margin

17. Solution
Given
Find Q, Pt and actual power
Q = V·v/s
Pt = Q rb g h

18. Solution

19. Forage Blowers
Conveying
Pipe
Radial
Paddle
Blower
Feed
Hopper

20. Factors Affecting Blower Efficiency
Blower design
Blower size
Number of blades
Angle of paddle slant
Clearance between paddle tip and scroll
Location and size of material inlet opening
Size of conveying pipe

21. Factors Affecting Blower Efficiency
Operating conditions
Conveying height
Blower speed
Material flow rate
Material properties
Bulk density
Coefficient of friction

22. Minimum Air Velocities for Flotation
In general require 2-3m3 of air to float 1 kg of grain
Energy required = kW/t
Material
m/s
Beans 30
Shelled corn 29
Oats 22
Wheat
Chopped hay 20
Ensilage
Source: Hunt, 2001