Crop and Pest Management Guidelines

A Cornell Cooperative Extension Publication
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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

5940 (constant)

Example: GPM = 20 X 4 X 20 =1600 = 0.27 GPM

59405940

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

For example:

  1. Select nozzle XR8003VS or XR11003VS at 30psi to give 19.3 gpa
  2. 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

  1. Select nozzle XR8003VS or XR11003VS at 30 psi to give 0.26 GPM or
  2. Select nozzle XR8004VS or XR11004VS at 20 psi to give 0.28GPM

But what about spray quality?

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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:

  1. Nozzle XR8003VS or XR11003VS at 30psi to give 0.26GPM or
  2. Nozzle XR8004VS or XR11004VS at 20psi to give 0.28GPM

Using the table in the next column, you can see:

  1. An XR8003VS at 30psi gives a medium spray quality
  2. An XR8004VS at 20psi gives a coarse spray quality but note:
  3. An XR11003VS at 30psi gives a fine spray quality
  4. 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.

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