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Sprayers
Manually operated sprayers
Foot operated sprayers
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- The pump in the foot sprayer consists of a
pump barrel and a pressure chamber.
- The plunger with a suction cup or piston
drives into the pump barrel, thus sucking the liquid into the
pressure chamber and expelling it through the discharge
line.
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- The return stroke of the plunger pulls the liquid
in through the suction hose for the next discharge.
- The sprayer develops a pressure of 60 – 80 psi and
has a provision for attaching two discharge lines.
Rocker type sprayers
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- Operating on the same principle as the foot
operated sprayer, this model is different only in as much as the
plunger is operated by means of a lever that is pushed by
hand.
- The pressure vessel is detachable. The
options of two lines are available.
- The Rocker Sprayer develops 60 – 80 psi
pressure.
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Pressure retaining knapsack
sprayers
- Also known as the Battery Sprayer, this model
permits the use of more than one tank depending upon the number of
operators employed.
- A separate charge pump with an inlet and an outlet
device is used to fill the tank with air and liquid. The tank is first
pumped with air upto a pressure of 40 – 50 psi and then charged with
liquid, boosting the pressure to 100 – 110 psi.
- As soon as the liquid is completely discharged from
the tank, a check valve designed like a float seals the outlet vent,
preventing the air from escaping.
Compression sprayers
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- The tank is a pressure vessel in which the liquid
is filled to two – third capacity.
- It is then pressurized to 60 psi by means of
the air charge pump.
- A pressure gauge or safety valve may
optionally be fitted to the tank.
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- A pressure regulator may also be used when the
discharge pressure needs to be strictly controlled.
Knapsack sprayers
- The tank is non-pressurised and made of brass, or
galvanized steel. The pump may be fitted into or outside the tank, and
sucks the liquid from the tank and expels it through the discharge
line.
- A spray boom or rig may be attached when wider
areas have to be covered. The knapsack sprayer develops 30 – 40 psi
pressure.
Bucket sprayers
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- In the single barrel type the plunger is
hollow and acts as a pressure chamber.
- In the double barrel variety, one barrel is
of smaller diameter than the other and acts as a pump, while the
bigger barrel serves as a pressure chamber, to produce more
continuous spraying. A pressure of 30 – 40 psi is
generated.
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Nursery sprayers
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- These are small, simple sprayers, generally
recommended for use in a nursery or private garden.
- They produce a fine mist spray and can be
effortlessly operated.
- Varieties with a small compressor-type or
plunger-type sprayer are also available.
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Power Operated Sprayers
Hydraulic sprayers
- Hydraulic sprayers may be engine or electric motor
driven, and are available with single, double, and the triple piston
pumps.
- The single piston pump develops a maximum pressure
of 150 psi, whereas the double and triple piston type develops 300 – 400
psi. Only two discharge lines can be used with the single piston pump,
whereas the double and triple piston pumps can accommodate 4 – 6
discharge lines.
- Operation is by means of 1 – 2 HP electric motor,
or 2 – 3 HP petrol, petrol-kerosene or diesel engine.
- These sprayers can also be driven by a power tiller
or tractor.
Motorised Knapsack Mistblower cum
duster
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- This sprayer cum duster is fitted with a
two-stroke air cooled engine of 35 or 70 cc capacity, connected to
a centrifugal fan by a direct drive.
- The spray liquid is first pressurized by air
generated by the blower. This air current achieves a velocity of
over 275 kmph at the nozzle, and sprays the chemical in fine
particles than can be measured in microns.
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- The nozzle design enables even spraying at maximum
efficiency.
- When dusting, the air blast enters the tank from an
air inlet, which is connected, to a tube with several holes on its
surface.
- This agitates the powder which is then thrust out
by the velocity of the air coming out of the blower, through the pleated
hose and out through the nozzle.
Tractor mount sprayers
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- As the name indicates, this sprayer is
attached to a tractor for use.
- The pump is driven by the PTO shaft of the
tractor, and the sprayer unit sucks the chemical and discharges it
through the spray boom, or through the discharge line consisting
of a delivery hose and spray guns.
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- The boom has a swivel arm to direct the spray
correctly. The main frame allows the spray boom to be adjusted according
to the height of the crops being sprayed.
Spinning disc sprayers
- Liquid is fed from the tank on to the spinning disc
by the force of gravity. The spinning disc, which has 180 channels on
the wall and 180 teeth on its periphery, operates at 4000 – 5000 rpm to
stir the liquid and create very fine, even particles for low volume
spraying.
- A smooth flow of liquid with highly controlled
droplet (100 – 165 microns) application is thus achieved. The stainless
steel disc is interchangeable.
Electrostatic spraying
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- This sprayer consists of a battery operated motor with a spinning
disc, a liquid tank, a handle and a set of batteries.
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- This is a fairly new technique, which has greatly
enhanced uniformity of spraying throughout the plant canopy.
- In this process, a free charge flows to the plant
in response to the presence of an electrical field, which is created by
a charged cloud. The surface charge is of the opposite polarity to the
charged cloud, and has a magnitude and distribution that maintains the
plant at ground potential (Zero Volts) in the presence of the charged
cloud.
- The most commonly used version of this new system
is the hand-held Electrodyn Sprayer, which atomises and propels charged
droplets, by means of electrical forces set up between a high voltage,
positively charged nozzle, the droplets and the earthed crop.
- The formulation is fed by gravity to the ‘bozzle’
(bottle plus nozzle) where it picks up a high voltage charge.
- The formulation then forms a number of uniform
ligaments, which in turn are broken up into electrically charged
droplets.
- These droplets are of uniform size and mutually
repellent and form a tenacious, even coating all over the crop,
including stems and undersides of leaves.
- No mechanical energy is required at the nozzle to
induce droplet formation; neither are compressors or centrifugal energy
employed, so the whole system works without moving parts.
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