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

Homework and Lab

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

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

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

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

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

Example AFS-Air Filtering System Cyclone Blower

Examples

Components Air moving system Feeding system Discharge system Pipelines and fitting

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

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

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

Bucket Elevator Capacity Q = V·v/s V = bucket volume (m3) v = belt speed (1.2 - 3.3 m/s) s = bucket spacing (m)

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)

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

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

Solution

Forage Blowers Conveying Pipe Radial Paddle Blower Feed Hopper

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

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

Minimum Air Velocities for Flotation In general require 2-3m3 of air to float 1 kg of grain Energy required =0.33-0.4 kW/t Material m/s Beans 30 Shelled corn 29 Oats 22 Wheat Chopped hay 20 Ensilage Source: Hunt, 2001