Given a minimally-acceptable overlap of 50% (25% from each neighbouring nozzle), the boom could be as low as 11”. The penalty is that this increases the distance droplets need to travel, increasing drift potential and any turbulent displacement problems arising from the moving boom.Īssuming a 110° flat fan at 24” boom height, each nozzle achieves a theoretical pattern width of about 70”, which is an overlap of 70÷20=3.4-fold or 240% on 20” nozzle spacing. This is why many operators set their booms above the minimum height – to prevent striping when the boom sways low. ContingenciesĪ suspended boom hardly ever stays at a uniform height It sways up and down with field conditions, topography, etc. For example, for 20 and 15” spacings, angling nozzles forward or backwards by 30° allows us to drop the boom another 2” closer to the target. Figure 4: Using 110° tips with 20″ spacing, the theoretical height at which we achieve 50% overlap is 11″ above target.īy tilting the nozzles forward or backward from the vertical, we can reduce the boom height somewhat further and still get the same overlap. Every time we halve boom height, we also halve drift potential. For those booms that are able to operate at a consistent height, narrower spacings permit lower heights that will reduce drift potential significantly. At that height, there’s plenty of overlap to go around for 20″ nozzle spacing. However, consider that most modern suspended booms are not operated at heights less than 24” to allow for sway. For 15” spacing, the height is reduced to 11”. Most nozzle catalogues have tables to help with this, or you can download a handy spreadsheet to calculate your own scenarios here.įor today’s standard 110° fans, a minimum boom height of 14” is needed to achieve 100% overlap. You must calculate the required fan angle and boom height to achieve this. If the boom has 20” nozzle spacing and we need 100% overlap, the width of the spray pattern at target height must be two times the nozzle spacing, which is 40″. Using nozzles with smaller flow rates would generally result in nozzle blockages.īut what if we want to change any of those variables? How does this affect nozzle spacing? Figuring out the pros and cons of an alternate spacing requires a little math and some contingency management. Combined with 0.15 to 0.3 US gallon per minute (gpm) nozzles and travel speeds of 6 to 8 mph, operators were able to apply 5 to 15 US gallons per acre (gpa) volumes. Specifically, this spacing required a boom height of 20” to obtain good overlap of the once-dominant 80° fan angle. The generic 20” spacing arose from long-held conventions about boom height, fan angle, and travel speed. This blends those regions of the patterns with high and low droplet densities. ![]() ![]() ![]() Figure 3: Consistent droplet number distribution along the boom requires at minimum 100% overlap (50% from each neighbouring nozzle).
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