When using a hand gun nozzle (Fig. 9), four factors are critical to delivering the correct rate uniformly over the application area:
To calibrate a hand gun nozzle, spray a known area and record the time required to cover this area. Then use a bucket to catch the spray from the hand gun for the time period elapsed during spraying of the marked area. Determine the application rate by measuring the amount of liquid in the bucket.
|
| Fig. 9. hand gun sprayer. |
You would like to spray at a rate of 1.5 gallons per 1,000 sq ft using a hand gun. To determine the actual ap-plication rate, you marked off an area 20 ft x 25 ft (500 sq ft). It took 2 minutes for you to spray this area. Then you sprayed into a bucket for 2 minutes and measured the amount of liquid in the bucket. It was 5.5 pints. What is the application rate in gallons per 1,000 sq ft and gallons per acre? What is the percent application error?
| 5.5 pints | = | 11 pints | (1 gallon = 8 pints) |
| 500 sq ft | 1,000 sq ft |
| 11 pints | x | 1 gallon | = | 1.38 gallon |
| 1,000 sq ft | 8 pints | 1,000 sq ft |
OR
| 1.38 gallon | x | 43,560 sq ft | = | 60.11 gallons | (1 acre = 43,560 sq ft) |
| 1,000 sq ft | acre | acre |
| Percent Application Error = | 1.5 - 1.38 |
| 1.5 |
Your actual application rate is 1.38 gal. per 1,000 sq ft. It should have been 1.5. This is an 8 percent application error, which is unacceptable (more than 5 percent of the intended rate). You should slightly reduce your walking pace, and repeat the calibration steps outlined above until the variation between the intended application rate and the actual measured rate is not more than 5 percent of the intended rate.