The document discusses grain loss in combine harvesters. There are four main areas where grain loss can occur: from the ear prior to entering the combine (field loss), from the straw walkers (walker loss), from the header (header loss), and from the sieves (sieve loss). Grain loss is monitored using sensors on the straw walkers and sieves that detect grain and transmit signals to a cab monitor. The amount of grain loss increases proportionally to the combine's throughput as separation capacity is exceeded.

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Combine Harvesters
Grain Loss

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Combine Harvesters
Grain Loss
Zero grain loss is unachievable due to a culmination of circumstances.
The best any operator can hope to achieve is an acceptable level that is
consistent with the crop being harvested .
Loss will occur four main areas.
from the ear prior to the combine entering the crop. Field Loss
from the straw walkers. Walker Loss
from the header. Header Loss
from the sieves. Sieve Loss

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Combine Harvesters
Grain Loss monitors
Cab Monitor
Straw Walker Sensor
Sieve Sensor

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Combine Harvesters
Grain Loss monitors
Grain loss in most combines is monitored by the use of sounding boards.
The boards cover the full width of the straw walkers and sieves.
The grain hits the sensor and this either generates an electric impulse or
a sound wave that is picked up by a microphone
The signals are then transmitted to the monitor in the cab usually
appearing as a light signal, bar graph .
With some harvested crops the monitors are not effective due to the straw
creating more impulses than the seed.

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Throughput
% Loss
A
Grain Loss increases in proportion to throughput.
Point A = separation Capacity at concave overload
Combine Harvesters
Grain Loss

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Combine Harvesters
Grain Loss
A
B
C D
A = Field Loss B= Header Loss
C = Thresher Loss B = Total Loss

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Header Width
Yield
Kg/ha
2.6m 3.0m 3.3 3.6 3.9 4.5 5.1 5.8 6.7
4,000 228 268 295 322 349 402 456 510 590
4.500 257 302 352 362 392 463 513 573 610
5.000 285 355 369 402 436 503 570 637 738
5.500 314 369 402 443 479 553 627 701 811
6.000 342 402 443 483 523 604 684 764 885
Combine Harvesters
Grain Loss

8. Combine Harvesters
Grain Loss
M&E/GHA/Combines/04/05 8
Loss of grain over the sieves. Cylinder speed too high – concave
clearance too close causing over
threshing
Adjust speed and clearance.
Ground speed too high.
Incorrect sieve settings
Fan speed to slow/high.
Air diffusers incorrectly set.
Shaker speed incorrect
Excessive returns.
Uneven feed.
Reduce ground speed
Adjust sieves to a wider setting
Adjust fan speed
Adjust diffusers.
Check belts and speed.
Adjust sieves

9. Combine Harvesters
Grain Loss
M&E/GHA/Combines/04/05 9
Straw Walker Loss. Over threshing at the cylinder.
Concave blocked with dirt and mud.
Heavy straw.
Straw walker speed too slow.
Filler bars still fitted.
Straw walker curtains damaged.
Ground speed too fast.
Insufficient feed (thin crop)
Concave too wide.
Excessive returns to cylinder.
Reduce cylinder speed.
Clean out concave
Reduce forward speed.
Check belt adjustment and speed.
Remove filler bars.
Check curtains and
replace if necessary.
Reduce ground speed.
Increase ground speed.
Adjust concave.
Adjust sieves

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Combine Harvesters
Yield Monitoring
Signal
Grain Flow

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Combine Harvesters
Grain Damage
Grain sample shows excess
of cracked grain.
Cylinder speed too high. Reduce cylinder speed.
Concave clearances too close Adjust concave.
Grain cracked in returns system.
Check returns, if good grain
is in the system
– open top or bottom sieves.
Slack chains on good grain
and/or returns elevator.
Adjust elevator chains.
Filler bars fitted. Remove filler bars.
Sieve settings. Adjust sieves to a wider setting

12. Combine Harvesters
M&E/GHA/Combines/04/05 12