New Holland CX720 Operator's Manual page 313

Cleaning fan
The cleaning fan speed can be adjusted electrically
from the operator's platform and can be read from the
InfoViewt monitor.
It's only possible to change the fan rpm when the
threshing mechanism is engaged.
Adjust it to suit the nature of the crop, chaff load and
moisture content. A grass seed variator kit can be
installed to obtain a lower fan speed regulation when
threshing small seeds. An insufficient air blast will
reduce the"clean area" of the top sieve causing a dirty
sample or grain loss (grain will shake over the end of
the shaker shoe).
The best way to check whether the volume of air is
satisfactory is to complete a "kill-stall", i.e. stopping
the engine with the threshing mechanism engaged
and checking the sieve coverage pattern.
If this method of checking is used:
The two rakes must be clean while the sieves
•
must be evenly loaded. Little or no grain should
be found on the rear part of the upper sieve.
• If the whole sieve is clear of grain and chaff, the
volume of air is too high. The grain will be blown
out of the machine and clean grain will be
transported over the lower sieve into the returns
cross auger.
• If the upper sieve is full of grain, the volume of air
is too low, so that the wind does not blow through
the chaff. Therefore grain will be shaken off the
sieve together with the chaff.
Sieve operation can also be checked by collecting
material coming from the rear of the cleaning shoe
and checking the sample for grain loss.
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SECTION 3 – FIELD AND SITE OPERATION
121