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Visit our new site Pesticidewise.com for more help on spraying pesticides with a knapsack sprayer including:

Our pages on calibrating your knapsack sprayer as still being developed. You can see an example of how to calibrate your knapsack sprayer for pesticide dose and spray mix rate on our YouTube channel.

Calibration of hand held sprayer equipment

Calibration of hand held sprayer equipment | Flash movie 


This is the web page version of the presentation "Calibration of hand held sprayer equipment" which is available to download as a PowerPoint presentation or view as a Flash movie

We welcome your feedback on this site. Please take a few moments to let me (helen.editor@stewardshipcommunity.com) know what you think: https://www.surveymonkey.co.uk/r/GRB538Y

Summary

  • Always follow high hygiene standards when working with crop protection products;
  • Spraying equipment must be calibrated at least once in every season of use;
  • Keep calibration records
  • Product labels often contain recommendations on optimum application volumes, timing and the choice of nozzles.

Calibration of hand held spraying equipment

There are many different ways to calibrate spraying equipment. This module contains several examples of calibration procedures for the following spraying equipment:

  • Single nozzle knapsack and lance sprayers;
  • Multi nozzle boom sprayers;
  • Hand held mist blowers;
  • Compression sprayers.

Factors affecting application volume are:

  • Forward speed,
  • Sprayer pressure,
  • Nozzle size, type and condition,
  • Operator accuracy

Forward speed

Forward speed will vary between spray operators thus always calibrate in the actual spraying situation:

  • Crop density and growing conditions will have an effect on walking speed (flood/irrigated crops)
  • It is very difficult to maintain an even forward speed when trying to walk at an unnatural forced pace

Do not use adjusted forward speed to vary the output of hand held equipment unless there are no other alternatives to achieve the desired application volume

Pressure

  • Built in control systems - Pressure regulators
  • External control sytems - Control flow valves

Several manufacturers make control flow valves that can be fitted behind the spray nozzle to keep constant pressure. Valves are available with a working pressure of 1 (yellow), 1.5 (red), 2 (blue) and 3 bar (green).

Valves are available with a working pressure of 1 (yellow) 1.5 (red) and 3 bar (green). (11 KB JPEG)
Valves are available with a working pressure of 1 (yellow) 1.5 (red) and 3 bar (green).

Nozzles - fans, hollow cones

  • Changing nozzles gives the greatest flexibility in spray liquid sprayer output
  • Many different types of nozzles are available which can generate contrasting application volumes and spray qualities.
  • Nozzles are colour coded according to emission rates
Nozzle range; air inducing (bubble jet), flat fan, low drift, hollow cone and flood jets (anvil, reflex) (24 KB JPEG)
Nozzle range; air inducing (bubble jet), flat fan, low drift, hollow cone and flood jets (anvil, reflex)

Operator accuracy

Even with a full, calibrated and checked sprayer, operator accuracy can have a major impact on the final results achieved. It is important to:

  1. Maintain a constant forward speed.
  2. Keep the nozzle at a uniform height above/from the target.
  3. If using a lever operated knapsack maintain a uniform pumping action.
  4. If spraying in a Zig Zig pattern ensure forward speed is suited to the width of the spray area to ensure even cover.
  5. Ensure accuracy in mixing the correct dose of product to the spray tank

Before carrying out any calibration:

  • Fill the sprayer with water and test that the sprayer is working well and has no leaks
  • Check that the nozzle is functioning correctly. Change the nozzle if needed.

Why calibrate?

Calibration enables the accurate calculation of how much product to add per tank and that product‘s optimal safe use. Under-dosing can lead to product failure, over dosing can lead to un-acceptable crop residues and other risks. Both under-dosing and over-dosing lead to wasted product and wasted money.

Easy calibration method

This method allows the calibration of single and multi nozzle sprayers without the use of calculations. Items required are:

  • A clean non-leaking knapsack with appropriate working nozzle
  • A means of measuring swath width and area to spray
  • Graduated measuring jug
  • Clean water
  • Stopwatch or watch with a second hand
  • Calibration disc/chart
  • Calibration record sheet
3. Most nozzles have an optimum height of 50 cms above the first intercepting surface; line drawing (7KB JPEG)
3. Most nozzles have an optimum height of 50 cms above the first intercepting surface
Calibration wheels can be useful to calculate different application volumes at different walking speeds. (12 KB JPEG)
Calibration wheels can be useful to calculate different application volumes at different walking speeds.

Calibration process

  1. Fill the knapsacks spray tank to maximum rated capacity with clean water.
  2. Set the correct operating pressure.
  3. Spray holding the nozzle at the required height and measure the swath width; most nozzles have an optimum height of 50 cms above the first intercepting surface
  4. Using the calibration chart below, find out how far you must walk to cover 100m2
  5. Measure out the required distance to enable you to spray 100m2 (this should preferably be done in the intended spray area to provide a reliable walking speed).
  6. Prime the sprayer and fill the tank to the maximum rated graduation line or if there is no line fill to the top.
  7. Walking at an even speed spray the 100m2, recording the amount of time taken to complete the task (if you spray more than one row do not record the time taken turning at the end of each row).
  8. Refill the sprayer to the same level as in step 6 recording the amount of water required.
  9. Using the calibration chart below, find out the application volume per ha.
  10. Record all the results on the calibration form.
  11. Repeat steps 7 to 10 three times to ensure accuracy.
4. Using the calibration chart find out how far you must walk to cover 100m2 (31 KB JPEG)
4. Using the calibration chart find out how far you must walk to cover 100m2
9. Using the calibration chart find out the application volume per ha. (16 KB JPEG)
9. Using the calibration chart find out the application volume per ha.

Calibration records

The following items should be recorded during calibration:

Calibration record (12 KB GIF)

Kalibottle calibration method

This method allows the calibration of sprayers using the Kalibottle. items required:

  1. A clean non-leaking knapsack with working nozzle
  2. A means of measuring swath width and area to spray
  3. Kalibottle
  4. Clean water
  5. Stopwatch or watch with a second hand
  6. Calibration disc/chart
  7. Calibration record sheet

Kalibottles are designed to fit over the sprayer nozzle to collect the spray emitted by the nozzle during a calibration. The Kalibottle has a graduated scale which allows the user to determine the application volume per hectare.

(22KB GIF)
Follow these steps to achieve an accurate calibration

Follow these steps to achieve an accurate calibration

1. Is the sprayer clean? If so:

  • Add clean water
  • Check sprayer working correctly without leak

2. Measure swath width at optional nozzle height
3. Practise spraying at a comfortable walking speed and even pressure
4. Mark out the distance require to spray 25m2

Swath width

Spraying distance

0.5m

50m

0.7m

35.7m

1.0m

25m

1.2m

20.8m

1.5m

16.7

5. Fit Kallbottle to lance by:

  • remove nozzle and cap
  • slip on Kallbottle cap
  • Refit nozzle and cap
  • screw bottle to cap

6. Hold lance vertical and spray into bottle when covering the 25m2
7. Hold bottle level. Spray rate is read from bottle
8. Empty bottle and repeat to check accuracy.

Caution: when full the Kalibottle is heavy and could damage the sprayer lance and the trigger assembly.

See also IPARC's Do-it-yourself Calibrator

The following items should be recorded during a calibration

Calibration records when using Kalibottle (13 KB GIF)
Calibration records when using Kalibottle

Static calibration

This calibration process works best with multi-nozzle sprayers because it not only gives an overal measurement of sprayer output but also allows the indentification in variation of flow from each nozzle to be measured. Items required:

  1. Sprayer
  2. Clean water
  3. Watch with second hand
  4. Measuring jugs
  5. Calibration sheet
  6. Means to measure 100m
  7. Calculator
  8. Spare nozzles

Calibration process

  1. Measure out 100m in intended spray area.
  2. Record the amount of time taken to walk the 100m, this should be done with the sprayer as it would be used by operator.
  3. On a level surface place a jug under each nozzle.
  4. Prime the sprayer with clean water.
  5. Place the nozzles over the jugs and spray for 1 minute.
  6. Record the output of each nozzle
  7. If any nozzles are more than 10% from the mean output then they should be changed.
  8. Repeat steps 5 to 6 three times to ensure accuracy.
  9. Use the collected measurements to obtain the output per hectare.

Static calibration calculation

Information Required

Example

1. Nozzle spacing (m)

 0.5m

2. Nozzle output per minute

 650mls

3. Number of nozzles

 3. 4

4. Forward speed (m/sec)

 1.9m/sec

 Static calibration records

Static calibration records (14 KB GIF)
Static calibration records

Calibrating mist blowers

A mist blower can be calibrated using the easy calibration method. When calibrating a mist blower it is important to hold the nozzle at the same angle as will be used when spraying.

  • Water to the nozzle is often gravity fed so altering the nozzle height will increase or decrease the flow rate.
  • You do not need to have the fan running when calibrating mist blowers.

Calibrating compression sprayers

To enable accurate calibration of controlled outputs of spray liquid from a compression sprayer the sprayer must be fitted with a constant flow value to enable constant pressure to be achieved.

A compression sprayer can be calibrated using any of the calibration methods mentioned in this Power Point.

Calibrating for inter-row applications

Sometimes it is not appropriate to spray the whole area within a treatment zone e.g.

  • Inter-row weed control
  •  Crops grown in rows or in beds

Calibration for band application

How to calculate the lowest amount of product required:

Calibration for band application (25 KB JPEG)
From within a 1 hectare field only 0.36 x 10,000m2 = 3600 m2 is to be treated. Less product is required but localised dose rates maintained.

From within a 1 hectare field only 0.36 x 10,000m2 = 3600 m2 is to be treated. Less product is required but localised dose rates maintained.

Efficient knapsack use

If the calibrated output is too high or too low changes can be made to ensure the application is made to suit the label recommendations and the crop geography.

  1. Increasing or decreasing walking speed will reduce or increase application volume per ha; difficult to maintain an un-natural walking speed.
  2. Increasing or decreasing sprayer pressure (if possible) will increase or decrease spray volume; will alter spray coverage and may increase spray drift.
  3. Changing the nozzle to one that has the correct output; this is the best solution. See the training module  Nozzle selection and their optimised use for more information.

Calculating product rate using dosage wheel for knapsacks

If you do not have a dosage wheel, send us your address and we will post one to you (12 KB JPEG)
If you do not have a dosage wheel, send us your address and we will post one to you.

If available use the calibration disc to work out how much product to ad to each knapsack.

  • Select product rate (B)
  • Select calibrated application volume (A)
  • Identify knapsack volume (C)
  • Result is the amount of proudct required for each knapsack (D)

If you do not have a dosage wheel please send us your address and we will post you a dosage wheel. You can also use the following formula to calculate doses per knapsack:

Quantity per tank = [Product rate/ha x tank size (lt)]/Calibrated application vol (lt)

Trainer notes

  1. Ensure that there is sufficient space to enable participants to calibrate sprayers.
  2. Have sufficient spraying equipment to ensure that there are no more than 3 people per sprayer.
  3. Have calibration equipment and sheets.
  4. If using the Kalibottle have sufficient bottles and calibration discs.

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 Calibration of hand held spraying equipment   | Flash movie


 
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