Plant protection equipment-Sprayer
Authors: ANURAG PATEL¹, PRABHAKAR SHUKLA² AND DUSHYANT SINGH²
3679anuragpatel@gmail.com
¹Vaugh School of Agricultural Engineering and Technology, SHUATS, Allahabad (U.P.) - 211007
²ICAR-Central Institute of Agricultural Engineering, Bhopal (M.P.) - 462038

Introduction

Sprayer machine used to apply liquid chemicals on plants to control pest and diseases. It can also be used to apply herbicides to control weeds and to spray micronutrients to enhance plant growth. Many pesticides used to control weeds, insects, and disease in field crops, fruits and vegetables etc. The different types of sprayer, (Commercially available) tractor mounted pull-type, pickup-mounted and self propelled sprayers are available from numerous manufacturers to do all types of spraying. Properly applied pesticides should be expected to return a profit. Improper or inaccurate application is usually very expensive and will result in wasted chemical, marginal pest control, excessive carryover, or crop damage. Agriculture is under intense economic and environmental pressure today. The high cost of pesticides and the need to protect the environment are incentives for applicators to do their very best in handling and applying pesticides. Studies have shown that many application errors are due to improper calibration of the sprayer. Applicators of pesticides need to know proper application methods, chemical effects on equipment, equipment calibration, and correct cleaning methods. Equipment should be recalibrated periodically to compensate for wear in pumps, nozzles, and metering systems. They are some precautions of spraying. There are many types of sprayers may be classified in to

(1) High volume sprayer (more than 400 l/ha.)

(2) Low volume sprayer (5 to 400 l/ha.)

(3) Ultra low volume sprayer (less than 5 l/ha.)

Main functions of a sprayer

• Breaking the chemical solution in to fine droplets of effective size.
• Distributing the droplets uniformly over the plants.
• Applying the chemicals with sufficient pressure for positive reaching the plants.
• Regulating the amount of liquid applied on plants to avoid excessive application.

Desirable purpose of a sprayer

• Application of herbicides to remove weeds.
• Application of fungicides to minimize fungus diseases.
• Application of insecticides to control insect pests.
• Application of micro nutrients on the plants.

Types of Sprayers

• Hand operated Sprayer
• Foot/Pedal Pump Sprayer
• Battery Operated Sprayer
• Tractor mounted sprayer
• Aerial sprayer

Components of a sprayer

• Pump: A pump is a device used to move fluids, such as liquids or slurries, or gases from one place to another. A pump displaces a volume by physical or mechanical action. Most hydraulic sprayers are equipped with positive displacement pumps capable of developing pressure, required for many spraying jobs. The discharge capacity of these pumps is approximately proportional to the speed.
• Chemical Tank: It is the container to hold the chemical solution. It is made up of PVC, Brass, etc. It is usually made of metal sheet or synthetic rubber or plastic having good resistant quality against corrosion, erosion, and similar actions.
• Agitator: It is the device which stirs the solution and keeps the contents in homogenous condition. Positive agitation of spray material in the tank is essential to permit using the full range of spray materials including powdery emulsions, fungicides, cold water paints or other spray material.
• Air chamber: Reciprocating type pump, an air chamber is provided on the discharge line of the pump to level out the pulsations of the pump and thus providing a constant nozzle pressure.
• Pressure gauge: It is a dial gauge which indicates the pressure at which the liquid is delivered from the pump. A pressure gauge properly calibrated, within the pressure range of the pump is provided on the discharge line to guide the operator for making proper adjustment of the pressure.
• Pressure regulator: The pressure regulator serves several important functions, adjusting the pressure as required for any spray job within the pressure range of the pump. With the positive displacement type of pump, it also serves as a safety device in automatically unloading the excess pressure by directing the unused discharge flow from pump back to the tank.
• Valves: A valve is a device that regulates the flow of a fluid by opening, closing, or partially obstructing various passageways.
• Cut-off valve: is provided in the delivery line to control the flow from the pump,
• By-pass valve: is provided in the delivery line to by-pass the flow from pump to tank when flow in delivery line is reduced than the pump capacity
• Relief valve: It is an automatic device to control the pressure of fluid or gas within a range a pre-determined pressure.
• Strainer: It is a small circular plastic filter any dust particle coming with the chemical solution. It is included in the suction line between the chemical tank and the check valves. In some sprayers strainers are provided at the mouth of the chemical tank.
• Nozzles: It is the component which breaks the fluid in to fine droplet. Automation of spray fluid is usually achieved by discharging the liquid through an orifice called nozzle under pressure.
• Spray gun: It is a hand held metallic of PVC pipe to one end of which the nozzle is fitted and a flow cut off valve and a handle are fitted at the other end. The delivery hose is connected to the spray gun. It conducts the fluid from the delivery hose to the nozzle.
• Spray boom: It is a long metallic or PVC pipe to which several nozzles are fitted with. The delivery hose is connected to the spray gun. High power and high capacity sprayers use spray booms. The coverage is larger compared to spray guns. Booms are usually mounted on suitable structures and used.
• Over-flow pipe: It is a conduit pipe through which excess fluid from a pump is bypassed in to chemical tank by the action of a relief valve or pressure regulator.

Types of nozzle

(a) Hollow cone nozzle: This liquid is fed into a whirl chamber through a tangential entry or through a fixed spiral passage to give a rotating motion. The liquid comes out in the form of a harrow conical sheet which then breaks up into small drops.

(b) Solid cone nozzle: This nozzle covers the entire area at small range. The construction is similar to hollow cone nozzle with the addition of an internal jet which strikes the rotating liquid just within the orifice of discharge. The breaking of drop is mainly due to impact.

(c) Fan nozzle: It is a nozzle which forms narrow elliptical spray pattern. In this type the liquid is forced to come out as a flat fan shaped sheet which is then broken into droplets. This nozzle is mostly used for low pressure spraying.

Components of a nozzle

• Nozzle body: It is the main component which encloses all other components of a nozzle
• Swirl plate: It is metal disc with two tangential holes which imparts a swirl or rotation to the liquid passing through it
• Nozzle disc: It is the component which breaks the fluid in to fine droplet. It is a flat disc with an orifice at the centre. When the spray solution reaches the disc from the swirl plate the disc builds up further pressure on the fluid and when the fluid passes out of the orifice, it breaks in to fine droplets.
• Strainer: It is a small circular plastic ring with nylon wire mesh to filter any dust particle coming with the chemical solution
• Spacer: There are two numbers of runner/ plastic rings placed in between nozzle plate and swirl plate and between swirl plate and strainer for effective travel of the solution.

Calibration of Sprayer

Sprayer calibration aims at obtaining a spray pattern and droplet size that will ensure optimum coverage of the target area with uniform sized droplets without causing runoff. Calibration should therefore be taken into account

• Target Area: Area to be sprayed (large area would require higher quantities)
• Droplet size: Fine droplets cover a large area with less volume and reduce run off, but can cause more drift and evaporation losses.
• Nozzle size and spacing: Once the volume of the spray and droplet size is determined, the nozzle size and spacing on the boom should be decided keeping in view the height between the boom and the crop.
• Nozzle capacity: Nozzle capacity is a manufacturer’s rating that depicts what output a nozzle will have at a given pressure. At constant pressure and speed, nozzle capacity is directly proportional to sprayer output. Output becomes greater as nozzle capacity increases.
• Speed: Keeping boom output constant Speed is inversely proportional to spray application. As you walk faster, less spray is applied to a given area.
• Pressure: A pressure increases, sprayer output increases. However, this relationship is not direct. Pressure must increase four times in order to double nozzle output. Variable pressure will cause variable output. Pressure may also affect the spray angle of different nozzles. The nozzle angle rating is for a specific pressure.

Testing of sprayer

The laboratory tests were carried out of the following.

• Functional performance of different components.
• Inspection of different components in respect of their satisfactory working.
• Checking of all fasteners and assembling the spraying unit as per the guide lines given by the manufacturers.
• Comparison of specifications of the machine supplied by the manufacturers with designer specifications.
  
  Calculations:

• Suction capacity of power sprayer

  Q = (Pi / 4) x D²x L x n x 10^-6 Where

Q= Theoretical suction capacity in lit/min

D= Diameter of plunger mm,

n= rev/min

L= Stroke length, mm

• Volumetric efficiency = (Actual suction capacity / Theoretical suction capacity) x 100
  
  
• Pump efficiency = (Water horse power / Shaft horse power) x 100
• Water horse power, kw = (Q x 9.8 x H / 6 x 1000) kw

Precautions of sprayers

1. Only take sufficient pesticide for the day’s application from the store to the site.

2. Recheck the use instruction of pesticide and equipment.

3. Make sure pesticides are mixed in the correct quantities.

4. Wear appropriate clothing.

5. Avoid contamination of the skin especially eyes and mouth.

6. Do not spray in high wind, high temperature and rain.

7. Selecting proper direction of spraying and also holding nozzle and boom at proper height.

8. Start spraying near the downwind edge of the field and proceed up wind so that operator moves into up sprayed area.

9. Never eat, drink or smoke when mixing or applying pesticides, never blow out clogged nozzle or hoses with your mouth.

10. Follow correct spray technique, spray plant crop thoroughly by operating sprayer at correct speed and correct pressure.

11. Never allow children or other unauthorized persons to be nearby during mixing never leave pesticides unattended in the field.

Cleaning and Storage of Sprayers

1. Remove and clean all screens and boom extensions with kerosene and a small brush.

2. Clean the tank with detergent.

3. Flush with two tanks full of clean waters spraying through the boom with the nozzle removed.

4. Store the sprayer away from sunlight and protect from frost.

5. Generally keep the sprayer away from children.

Future scope and farmer’s opinion

The machine has wide scope, if it is modified according to farmer’s opinion.

• The performance of sprayer was satisfactory; however the plastic valves may be replaced with brass valve.
• The crop row spacing has to be planned before planting for tractor movement with aero blast sprayer.
• The use of this equipment will reduce in labour and cost.
• It is useful for spraying on horticultural trees and tall crop such as cotton, sunflower, pigeon pea etc. The machine consists of a tank of 400 litres capacity, pump, fan, control value, filling unit, spout adjustable handle and spraying nozzles to release the pesticide solution.

Conclusions

This article will be helpful for the users in selection of nozzle for precise spray as per the need of operation. Knowledge of calibration and precautions taken during operation by the operator will reduce the losses and health hazard during operation. This will not only reduces the cost by application of correct quantity of chemical in appropriate manner but also helpful in saving the environment by reducing the soil, water and air pollution.

References:

1. D. Nuyttens, K. Baetens, M. De Schampheleire, B. Sonck.(2007): Effects of nozzle type, size and pressure on spray droplet characteristic. Biosystem Engineering 97, pp 333-345.
2. Pedro Teixeira Lacava, Demétrio BastosNetto, Amílcar Porto Pimenta (2004): Design procedure and experimental evaluation of pressure-swirl atomizers.24th International Congress of Aeronautical Science.
3. Brent A. Pringnitz: Sprayer nozzle selection for pesticide performance and drift reduction. Extension program specialist, Department of Agronomy Iowa State University.
4. John W. Slocomb: Agricultural spray nozzle: selection and sizing, extension agricultural engineer, Kansas State university [
5. BETE Flat fan nozzle catalogue, www.bete.com.




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