Calibrating the sprayer--first method

Sprayers often do not deliver the calculated amount of spray per minute. There are several ways to check this. The following method is suggested.
1. Fill the sprayer tank completely with water only.
2. Pressurize the system to desired level and spray for 3 minutes. With PTO units, be sure that the pump speed and pressure are identical to that used when spraying.
3. Determine the amount of water required to refill tank.
4. Calculate gallons per minute and compare that amount with what should have been used (see Table 3-1).
5. Adjust pressure, nozzle sizes, or flow control and repeat the procedure until the delivery is correct.
6. Further check application rate by observing the acreage covered by a tankful (1 acre equals 43,560 sq ft).

Example: We pressurize a sprayer to 200 psi and spray (in place) for 3 minutes. Carefully measuring, we determine that it requires 14.5 gallons to refill the sprayer tank to previous level. To determine the rate, divide the amount delivered (14.5 gal) by the time (3 min) to calculate the delivery rate (4.8 gal/min). If we are to spray an orchard having a distance between rows of 26 ft at a rate of 50 gal of spray/A with the sprayer traveling at 2 mph, we find that the rate should be 5.3 gallons per minute (by checking Table 3-1). To increase application, we can increase pressure, increase nozzle size or flow rate, decrease travel speed, or any combination of these. Make changes and rerun calibration test.