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How a Crop Sprayer Works. |
| A Sprayer is basically a very simple machine consisting of
a tank, a pump and nozzles. The tank holds around 1200 litres water
and chemical, the pump sucks from the tank, discharges through
filters and pressure controls to the booms where the pressure is
converted to velocity in jets, causing atomisation. To increase
accuracy and efficiency controls systems are fitted to assist the
operator. As the working width has increased boom weights have
increased requiring hydraulic movement and to maintain the correct
working height, hydraulic levelling is used. Electronics are used to read
tractor speed from a radar sensor, fluid flow rate and fluid pressure
to control the output at the nozzle precisely. |
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The in-cab controls
The 'computer' which monitors forward speed, pump pressure and flow and regulates the output to maintain a fixed rate per hectare. Details are displayed on the LCD screen (a) and the menus are accessed by membrane keys (b). Below that are the controls for the boom sections; the main on/off is (c) whilst each section can be turned on or off by the switches (d). The switch at top left is to increase/decrease the pressure should the sprayer ever be used in manual mode. Under this are the hydraulic controls for boom lifting/lowering, tilting individually or together, locking for transport and folding unfolding. |
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A nozzle tip showing the oval outlet (g) to create a 'flat
fan' spray pattern, and the strainer gauze (f) which fits inside the tip. |
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A closeup of a triple jet holder, which is rotated to select a different
nozzle. The red pipe leads to a remote pressure gauge.
Anti- drip diaphragm (h) ensures a positive shut of when pressure drops.
(i) 150 lt 'Lo Drift' Nozzle. The forms a coarse droplet to reduce spray drift.
(j) Standard
120 lt Fan nozzle. Probably the most common nozle in use.
(k) Air inclusion 'bubble jet'. Forms bubbles by drawing air in holes
at the base of the nozzle - reduces drift immensely. |
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The left side of the sprayer showing:
(m) Main on/off and pressure regulation valves(Motorised)
(n) Manual control
valves. Black=suction, Green=discharge, Blue=control.
(o) Self Cleaning
filter on pressure side.
(p) Induction hopper for chemical filling.
(q) Chemical rinse pipe.
(r) Filling connector. |
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Rear View of the sprayer with booms around half height.
(s) 6 chamber diaphragm pump which is powered by the tractor PTO (power take
off)
(t) Clean locker for overalls etc.
(u) Clean water tank for washout system. Used when completing a days work
so that all chemicals are sprayed on crop and sprayer has very little residue
remaining in tanks and pipweork.
(v) Hydraulic ram for main boom swingout. All folding is carried out hydraulically
(see below)
(v) Cover over hydraulic solenoid valves.
(w) Boom selection motorised valves. Two outer sections of 4m and two inner
sections of 6m.
(x) Flow meter supplying information to the computer. |
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The 600lt front tank. The pump and valves are just visible where the
pipes emerge. It is filled using the pump on the rear tank and chemical
added by induction hopper. A hydraulically powered pump is used
to circulate, or transfer the contents to the rear tank when required. |
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Boom Folding/unfolding.
1)The booms in the transport position.
2)Lifted from their cradles and starting to swing rearwards.
3)Fully back and starting to lower to the horizontal working position.
At this point the booms may be used as a 12metre (40 foot) sprayer.
4)The last 4m (13 foot) section is unfolding.
5)Fully extended and locked at 21 metres (70 feet). |
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::Copyright J. Cranston::
2000 -
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