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Sprayers Tutorials

Plant protection equipment classification

Plant Protection equipment falls into two major categories

  • Spraying equipment, which is used for the dispersal of insecticide in liquid form.

  • Dusting equipment, which is used for the dispersal of insecticide in powder form.

Both dusters and sprayers are available in manually operated and power operated varieties.


Manually operated sprayers

Foot sprayers

  • The pump in the foot sprayer consists of a pump barrel and a pressure chamber.

  • The pump is fixed in a vertical position with necessary braces.

  • The plunger moves up and down when operated by the pedal.

  • A ball valve is provided in the plunger assembly itself to allow the fluid to cross the plunger and getting pressurized in the pressure vessel.

  • During the upward motion of the piston fluid is sucked in and pressurized into the pressure vessel and during downward movement, the sucked fluid crosses the plungers and enter the pump.

  • The sprayer develops a pressure of 60 - 80 psi and has a provision for attaching two discharge lines.

Rocker sprayers

  • The rocker sprayer has a pump assembly, fixed on a wooden platform with an operating lever, a valve assembly with two ball valves, a pressure chamber, suction hose with strainer, and delivery hose with spray lance.

  • When the plunger is pulled behind by pulling the lever way from the pump, the spray fluid from the container is sucked through the strainer and pushes the bottom ball valve above and enters the pump.

  • The movement of the lower ball valve is arrested by the upper valve seat.

  • When the lever is pushed towards the pump, the sucked fluid is forced to enter the pressure chamber by opening the upper ball valve.

  • The operation is continued till the entire suction pipe, ball valve assembly, delivery hose and a portion of pressure vessel is fitted with spray fluid and the pump operator finds it difficult to push the piston forward, due to the downward pressure developed by the entrapped compressed air in the pressure vessel.

  • Thereafter, the trigger cut off valve will be opened to allow the spray fluid to rush through the nozzle and get atomized.

  • Usually 60 - 80 psi pressure can be built in the pressure chamber and hence can be conveniently used for tree spraying.

Hand Compression sprayers

  • 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.

  • A pressure regulator may also be used when the discharge pressure needs to be strictly controlled.

Knapsack sprayers

  • Any sprayer which is carried on the back of the operator is called a knapsack sprayer.

  • The commonly used manually operated knapsack sprayer will have one hydraulic pump working inside the container.

  • The plunger works inside the replacement well attached at the bottom of the container, for easier maintenance.

  • The pump can be operated through the appropriate linkages by oscillating the handle, with the sprayer carried on the back.

  • An agitator is also provided with the pressure chamber to agitate the fluid so that the particles in suspension will not be allowed to settle down.

  • A delivery tube is attached on the other end of the pump which carries the pressurized fluid to the spray lance.

  • The knapsack sprayer develops 30 - 40 psi pressure.

Stirrup Sprayers

  • The stirrup sprayer is designed to pump the spray fluid directly from, the open container, usually a bucket.

  • The hydraulic pump will be put inside the bucked and held properly with the help of foot rest.

  • As the plunger is pulled up, the fluid enters through the suction ball valve assembly and when the plunger is pressed down, the suction valve closes and the fluid enters the pressure chamber through a ball valve assembly.

  • As the plunger is continuously worked, pressure is built in the pressure chamber and the delivery hose.

  • As soon as the required pressure is built up, the spraying will be done.

  • A stirrup sprayer develops 30-40 psi pressure.

Nursery sprayers

  • It has a hydraulic pump inside the container, with cylinder, plunger and a plunger rod.

  • By operating the plunger up, the spray fluid in the container is sucked into the cylinder through a ball valve assembly and then pressurised during the downward stroke.

  • The pressurised fluid is then let out through a nozzle, and sprayed into fine droplets.

  • 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.

Power Operated Sprayers

Motorised Knapsack Mistblower cum duster

  • 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.

  • 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/Piston Power Sprayer

  • 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.

  • The sprayer unit alone is ideal for feeding pressurised fluids into boilers & for other industrial purposes.


Hand Rotary Duster Belly Mounted

  • It consists of a blower complete with a gear box and a hopper. It is operated by rotating the crank.

  • The cranking motion is transmitted through the gear box to the blower.

  • The blower sucks the dust or powder from the hopper through the connecting pipe, and pushes it out forcefully to achieve efficient dispersal.

  • The operator carries the duster by means of one or two shoulder straps, and holds the lance in his left hand cranking the handle with his right.

  • The feed is controlled by a feed control lever, which operates a slide to control the aperture at the bottom of the hopper.

Every sprayer should have

  • A discharge Line consisting of a delivery hose with couplings and a spray lance.

Every Spray Lance must have

  • A cut-off valve

  • An extension rod-straight or goose-neck

  • An appropriate nozzle

Extension Rod

  • Comes in varying lengths, according to customer requirements but lengths longer than 90 cm are difficult to handle.

  • For tree spraying, bamboo lances i.e. brass tubes inserted into a hollow bamboo are recommended.

  • The larger diameter of the bamboo helps to off-set the length of the lance (up to 2.5 meters, making it easier to handle).

Cut-off Valves

  • These are spring-activated (trigger control) or operated by means of a simple knob or trap.

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