1. Feeding Arrangements for Screw Conveyors
Good design focuses on the fill percentage and method of loading material. We base calculations for transporteur capacity and power on the chosen fill percentage.
We describe various feeding methods below.
(1) Fixed Feeding
A screw feeder uses a specially designed screw sealed in a tubular trough. It moves material from a hopper at a set rate. The output rate does not depend on the material height in the hopper.
A rotary vane feeder uses a rotating cylinder with pockets of fixed volume. Its rotation speed sets the feed rate. We can drive it in sync with the conveyor screw or use a separate fixed-speed or variable-speed drive.
(2) Multiple-Point Feeding
Sometimes a conveyor needs multiple feed points. An operator must manually control them.
If only one inlet opens at a time, we must set the gate or valve. Its maximum opening should not overload the conveyor.
If more than one inlet opens, we must carefully adjust each one. The total flow from all inlets must stay below the conveyor’s design capacity.
If all inlets open and feed simultaneously, we must control the total material flow.
(3) Feeding from a Fixed Bin
Feeding directly from a fixed bin is risky. Without a flow control device, overload risk increases significantly.
A simple, practical solution is to add an ammeter to the motor starter. This meter shows the load current. It indicates when the conveyor reaches full load. This method works well for manual control of feeding.
(4) Flood Feeding
Material often falls vertically onto the conveyor’s inlet flange. The impact from falling lumps or particles can cause damage or wear.
We can solve this by installing a baffle plate or a cushion box in the inlet chute.
2. Discharge Arrangements for Screw Conveyors
A standard discharge outlet is very common. It controls the discharged material and directs it into the next process equipment or storage.
An end discharge outlet is similar. However, the outlet is at the very end of the conveyor trough. Its end flange is integral with the trough end.
(1) Discharge Opening without Spout
Material falls directly through an opening in the bottom of the trough. We typically use this for intermediate discharge points. Discharge continues here until the drop height is gone. An example is discharging into a silo.
(2) Bottom Discharge for Piling
We use this to discharge and distribute material into a hopper, bin, or stockpile. An opening along the required length of the trough bottom lets material out. The material forms a natural pile. Later material travels over this pile to reach undischarged areas.
(3) Discharge at Trough End
Material discharges directly through an opening at the end of the trough. A partial end plate supports the screw. The bearing mounts on the end flange. We cannot use this method if the conveyor fill factor exceeds 0.45.
(4) Open End Discharge
The conveyor’s last screw section uses a standard hanger bearing for support. This setup allows material to discharge freely into a bin, stockpile, or similar location.
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