The “128” Method of Boom Sprayer Calibration. Smithco Spray Star 1602P

THE NOZZLE CHART METHOD OF CALIBRATION

(CONTINUED)

5. For Sprayer with Electronic Spray Control Systems.

On sprayers equipped with Electronic Spray Control Systems such as those manufactured by Raven

Ind., Micro-Trak Co. and Dickey-John Co., it is still important to select the right type and size of nozzle for the required operation. Electronic Spray Control Systems cannot function properly if the nozzles are not capable of delivering the programmed (desired) application rate. Nozzles which are too large will not develop adequate pressure or satisfactory spray patterns. Nozzles which are too small will not allow the discharge of spray material at the programmed application rate.

Further, when calibrating sprayers which are equipped with Electronic Spray Control Systems, care must be taken to use the mode of operation on the Spray Control System (Gallons per acre “US” Mode);

Gallons per 1,000 Square Feet (“Turf” Mode); or Liters per Hectare (Standard International Model), which corresponds with the nozzle calibration charts (gpa, gpt or lph).

6. Using the Nozzle Charts.

Select the correct chart based on your nozzle type, nozzle spacing and desired expression of application rate (gpa, gpt or lph). If the desired operating speed is not found on the nozzle chart, it is simple to determine application rate at different speeds by estimating from the known facts.

Example 1: If the desired speed is 2

1

/

2

MPH (4 kph) on a sprayer using TurfJet nozzles (Chart 5). The average between the application rates for 2 MPH and 3 MPH may be assumed to be the application rate for 2

1

/

2

MPH.

Example 2: The desired speed is 6 MPH. Use the application rate column for 3 MPH a divide by 2.

7. Converting Nozzle Chart Method to British Gallons.

To convert any of the Gallon Per Acre rates to Imperial Gallons per acre, (Imp gpa) multiply by 0.83. To convert any of the Liter Per Hectare rates to Imperial Gallons Per Hectare (Imp GPH), multiply by 0.22.

8. Checking the Actual Application Rate.

After the combination of ground speed, nozzle size and operating pressure has been selected, the sprayer should be operated with water only to determine if the target application rate is achieved.

THE “128” METHOD OF BOOM SPRAYER CALIBRATION

The “128” Method is useful for calibrating sprayers and also for checking the calibration of sprayer calibrated by the Nozzle Chart Method and sprayers using Electronic Spray Control Systems. The “128” is based on a convenient mathematical relationship that exists between US Gallons, liquid ounces and acres.

An ounce is 1/128th of a (US) gallon. If an area which was “1/128th of an acre” could be found, the number of ounces applied to that small area would be equal to the number of gallons applied to the acre Thus, no mathematical computations would be required.

To determine an area which is 1/128 of an acre:

• On nozzles with 20 inch (51 cm) spacing, measure off a distance of 204 ft (62 meters). Mark a “START” and a “STOP” line. The rectangle formed by this distance and the spraying width of one nozzle 20" (51 cm) is equal to 340 square feet which is equal to 1/128 acre. Therefore, the amount of material applied to this area by one nozzle in OUNCES is the same amount of material applied to an acre in GALLONS

(gpa).

• On nozzles with 10 inch (25 cm) spacing, the measure distance is 408 feet (124 meters).

• On nozzles with 30 inch (76 cm) spacing the measured distance is 136 feet (41 meters).

CALIBRATING FOR APPLICATION

1. Fill the sprayer tank with water. Run the sprayer, inspect it for leaks and make sure all systems function properly.

2. Drive the sprayer through the measured distance discussed above at normal spraying speed, record the travel time required to cover the measured distance in seconds with a stopwatch.

31

THE “128” METHOD OF BOOM SPRAYER CALIBRATION

The carrying or towing vehicle is to be traveling at the desired speed when it crosses the start line of the measured course.

Repeat this procedure and determine the average of the two times.

3. With the sprayer parked, run the sprayer at the required pressure level. Catch the output of each nozzle in a container which is marked or graduated in Ounces for the exact same period of time which it took the sprayer to cover the measured course in step #2. It is necessary to operate the vehicle engine at spraying speed using a hand throttle.

4. Observe the volume of water in the collection bottle. The number of OUNCES collected in the time it takes to cover the marked course. Take the average nozzle output by adding the outputs of each nozzle and then dividing that sum by the number of nozzles.

The NUMBER OF OUNCES collected in the time required to cover the SMALL AREA is equal to the

NUMBER OF GALLONS applied per ACRE. For example: if an average of 40 ounces of water is collected in the time required to cover the 1/128 acre area, the application rate is 40 gallons per acre (gpa).

As a practical matter, if high application rates are desired (above 75 gpa), the measured course length should be reduced by half (i.e. 102 ft (31 m) for 20 inch (52 cm) spaced nozzles). The volume collected (above) is then doubled (multiplied by 2).

AVERAGE OUTPUT (Ounces) = APPLICATION RATE (gpa)

5. Observe individual nozzle output volumes. If an individual nozzle is 10% above or below the average output, check for blockages in the nozzle or in the nozzle strainer. If the nozzle is worn or damaged, replace it.

6. Compare this actual application rate with the recommended rate. If the actual rate is more than 5% higher or lower than the intended rate, adjustments must be made.

7. Minor adjustments in application rate may be made by increasing or decreasing the spraying pressure.

Lowering spraying pressure decreases application rate. Increasing spraying pressure increases application rate. This procedure normally does not apply to spray systems controlled by an Electronic Spray

Control System, which governs flow rate.

8. Adjustments in application rate may be made by increasing or decreasing the travel speed of the sprayer if conditions permit. Slower speeds increase application rate. Faster speeds decrease application rate.

9. Nozzle sizes can be changed to provide the correct application rate. Refer to the nozzle charts in this book for the desired nozzle type.

10. Re-calibrate the sprayer (steps 2-6) after any adjustments are made.

As previously discussed, there are other acceptable methods of Turf Sprayer Calibration. Chemical suppliers, Agricultural Extension Agents, Universities and consultants of various types offer helpful advice on this subject. Technical catalogues are available from nozzle manufacturers.

TRANSFERRING THE “128” METHOD INTO METRIC (LITERS PER HECTARE)

The same steps are used that are used when calibrating in gallons per acre. First a relationship between a measurable amount (milliliters) and the calibration amount (liter) is determined. That ratio is 1:1000.

Now an area which is 1/1000th of a hectare must be measured.

On spray booms with 51 cm (20 inch) spacing, mark off an area which is 20 meters (65.6 feet) long . The area formed by that length and the width of one spray nozzle (20 meters by 0.5 meters) is 10 square meters which is

1/1000 of a hectare. Therefore, the amount of spray material applied to this small area in milliliters is equal to the amount applied to one hectare in liters.

Then, follow the remaining steps 2-10, substituting milliliters for ounces, liters for gallons, square meters for square feet and hectares for acres.

AVERAGE OUTPUT (Milliliters) = APPLICATION RATE (LITERS/HECTARE)

32