7.6 Selecting Nozzles from the Nozzle Catalogue -Boom Sprayers
Step 1. Calculate the required nozzle output.
Formula: GPM = GPA X mph X nozzle spacing
Example: GPM = 20 X 4 X 20 =1600 = 0.27 GPM
Consider forward speed e.g. 4 mph, if too high: boom bounce and boom yaw
Consider pressure, too high: may lead to drift, too low: may lead to droplet bounce
Example 1 - Using a Spraying Systems catalogue #49A, page 10
Look at the columns headed GPA at 20" nozzle spacing
Select the 4 mph column
Look down the column until you see a figure close to 20 gpa, then look to the left to find the operating pressure
- Select nozzle XR8003VS or XR11003VS at 30psi to give 19.3 gpa
- Select nozzle XR8004VS or XR11004VS at 20psi to give 21 gpa
Select the appropriate nozzle.
Example 2 - Using a Spraying Systems catalogue #49A, page 10
Look at column headed: Capacity of 1 nozzle in GPM
Read down column
- Select nozzle XR8003VS or XR11003VS at 30 psi to give 0.26 GPM or
- Select nozzle XR8004VS or XR11004VS at 20 psi to give 0.28GPM
But what about spray quality?34196
7.6.1 Selecting a Nozzle to Give Desired Spray Quality
Example using a Spraying Systems catalogue #49A, page 161
In the previous exercise we considered selecting:
- Nozzle XR8003VS or XR11003VS at 30psi to give 0.26GPM or
- Nozzle XR8004VS or XR11004VS at 20psi to give 0.28GPM
Using the table in the next column, you can see:
- An XR8003VS at 30psi gives a medium spray quality
- An XR8004VS at 20psi gives a coarse spray quality but note:
- An XR11003VS at 30psi gives a fine spray quality
- An XR11004VS at 20psi gives a medium spray quality
Spray classification and target
1. Fine sprays can produce enhanced retention on the target and may be used for foliar acting weed control and cotyledon-stage weed control
Careful attention must be paid to weather conditions: do not use a fine spray for pesticides labeled toxic, or when drift may cause problems near susceptible or sensitive areas.
2. Medium sprays when the leaf is the target.
3. Coarse sprays have a low risk of drift but should be used only where recommended as a lot of spray is wasted as the larger droplets bounce off the leaves.