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There us a wide variety of such equipment available on the market, and table 9.6 is an attempt to categorise their ability to move grain.
Table 9.6 Grain Handling Equipment
|Type of Equipment||Fixed or Portable||Horizontal or H Vertical V||Capacity range||Power Requirement||Cost||Advantages||Disadvantages|
|Belt and Bucket elevator||F||V||medium||low||medium||1. efficient||1. can be|
|3. high capacity||2. expensive|
|F P||H + V||medium||medium||medium||1. wide range||1. can damage|
|2. medium to|
|Belts||F||H||high||low||high||1. long distances||1. expensive|
|If belt is||2. low power||2. angle very|
|ribbed max||3. self cleaning||limited|
|General purpose elevator with belt or chain with slats||F P||H||medium||low to||medium||1. multipurpose||1. noisy with chain|
|and inclined with ribs||medium||2. inexpensive|
|P||H||medium||on tractor||low||1. (flexible||requires space|
|to||- high||2. high output in||to operate in|
|high||short time -for loading lorries|
|P||H||depends on||-||-||1. high labour|
|P||H + V||low||high||high||1. flexible||1. noisy|
|to||2. much dust|
|medium||3. reduced cap for wet grain|
A flat belt is carried between a crowned pulley at the top and bottom of casing. Small buckets or scoops are fixed to the belts at regular intervals and these carry the grain from the elevator bottom to the top. The capacity depends upon width of buckets, spacing and belt speed. Elevators of up to 20m height and capacities of 50tonnes/h are available.
Auger (Screw Conveyors)
Auger elevators are reasonable in cost, comparatively light in weight, and dependable in their operation. They are available in a wide range of lengths and capacities and are usually powered by an electric motor. Long augers may be mounted on wheels for easy transport. The angle of operation is adjustable, however, the capacity goes down as the auger is raised, see table 9.7. High moisture content also reduces the capacity.
Table 9.7 Example of Auger capacity and power requirements per 3m length of auger (0150mm)
Angle of Elevation
|0° t/hr kW||22.5° t/hr kW||45° t/hr kW||67.5° t/hr kW||90° t/hr kW|
Note: Auger speed 400 rpm
Power requirement is directly proportional to the auger length.
Flat Belt Conveyor
These are used in practice horizontally although up to 15° inclination is possible. With ribs the angle can be increased to 30°. The capacity is high and loading and unloading can be done any place along the belt. It does not cause any damage to the crop and raises little dust.
Chain and Slats Conveyor
These consist of a chain carrying traverse slats which drag the grain along a metal or wooden trough. Slat width up to 300mm spaced 150 to 300mm apart and chain speeds of 10 - 77 cm/s are used to give outputs up to 30 tonnes/in. Small sized models have no support frame and can be carried by two men.
These may be a continuous belt with ribs or a chain conveyor with slats.
To achieve high capacity with tractors and trailers when taking grain to the store, an effective system of receiving grain must be used. Ideally, it should be possible to dump a trailer load and pull away within minutes. Such a reception facility will normally be associated with an elevator to raise grain for conditioning or storage.
Reception Pit with an Elevator
A concrete wood or steel-lined pit with an inverted pyramid or V-shaped bottom is built in the ground, see figure 9.29.
Figure 9.29 Dump Pit with an auger moving the grain to the elevator.
The crop is dumped from a trailer into the reception pit from which it flows by gravity or by the help of an auger into a second pit containing the bottom end of an elevator. Much time is saved, if reversing to the tipping pit by the farm transport is avoided, by having a "run-over" pit. This requires a safety grid, which must be strong enough to carry a loaded trailer.
Shallow Surface Pits
These are usually in conjunction with an auger. Two simple pits of this kind are shown in Figure 9.30.
Figure 9.30 Small Simple Reception Pits.
Overhead Grain-loading Bins
Hopper-base gravity discharge bins, when erected at a suitable height, facilitate the loading of transport vehicles at high rates. This will cut the waiting cost and should therefore be considered where the capacity of the loading equipment is low compared to the load capacity of the vehicle.
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