34
Use of mistblower
be held steady or moved only very slowly to ensure that
the spray mist is properly formed and stable.
In mistblowing the solution flows from the container, down
through the open shut-off cock and the metering nozzle to
the spray tube. The jet of solution is injected into the air-
Influence of walking speed and working width on
stream, atomized and discharged. The airstream is per-
discharge rate and amount of solution needed
meated more or less uniformly with very fine droplets.
Practical experience has shown that walking speed can
vary by 5 to 6 m/min. A slower walking speed means that
The factors which influence the liquid discharge rate per
it is necessary to reduce the discharge rate or amount of
unit area are either fixed by the setting (discharge rate per
solution and vice versa. Walking 6 m/min slower than the
unit time) or determined by the operator. Walking speed
specified 60 m/min means a reduction of 10%.
and working width can vary. These variations can result in
considerable differences in the quantity of active ingre-
In our example the setting of the metering unit would also
dient applied per unit area. In addition, the wetting effect
have to be reduced by 10%, from 2.7 to 2.43 I/min. If this
can be altered by the direction and strength of the wind.
is not done, the quantity of solution required would in
crease 10%, from 54 liters to 59.4 liters.
Great care must be taken with active ingredients which
can harm plants and the environment if applied in too high
The variation in working width can be considerable, espe
a dosage. Too low a dosage may fail to achieve the desired
cially if the field has not be marked with stakes. A reduc
effect.
tion of the working width at a given walking speed means
that the discharge rate would have to be' reduced or the
To limit these variations, always run the mistblower at full
amount of solution increased and vice versa. Reducing the
throttle with the shut-off cock fully open. Accelerate the
width by 0.5 m, after having assumed a working width of
engine up to full throttle first and then open the shut-off
3 meters, represents a reduction of 17%.
cock. Note that the discharge rate is controlled by the me
tering unit, not the shut-off cock.
The normal walking speed for low-growing crops is 1 m/s.
It may be necessary to walk slower when mistblowing
higher crops.
To achieve greater working widths or treat open and high
growing crops, the spray tube must be moved quickly
back and forth or up and down. In order to extend the
mistblower's vertical reach (tall trees), the spray tube must
