How to Calibrate an Airblast Sprayer

Set the pressure for 540 rpm and leave all nozzles needed for spraying attached. Keep the fan off.

Fill up the spray tank with clean water and set a measuring jug beneath one nozzle. To avoid getting wet, secure a plastic hose to the nozzle and set the other end in the jug.

Operate the sprayer for one minute with all nozzles operating. Measure the amount of water the sprayer puts out into the jug. Check the output outlined in the user manual and compare it to this amount. The nozzle output should not vary by 10 percent. If it does, then the nozzles are worn and should be replaced.

Repeat the calibration process for all nozzles. Add all the water measurements together for all nozzles to calculate the total sprayer output in liters per minute.

Calculate the travel speed by inserting the time in seconds into the following formula:

Travel speed (km/h) = 100 (m) x 3.6 divided by time in seconds. For example, if you operated the sprayer for one minute or 60 seconds, the equation is 360 divided by 60, which equals 6 km/hour. Insert this answer into the formula in the next step. The normal speed for spraying is between 6 and 8 kilometers.

Calculate how many seconds it takes to travel 100 meters with the sprayer attached and half full. Measure out 100 meters on the ground and mark the start and finish positions with wooden pegs. Measure row width and then calculate the spray application rate with the following formula:

Application rate (L/ha) = 600 x total sprayer output (L/min) divided by row width (m) multiplied by travel speed (km/h). For example, if your total sprayer output is 50 liters per minute and the speed is 6 kilometers per hour and the row spacing is 4 meters then the application rate is 600 x 50 = 30,000/25 = 1,250 L/ha.