Choosing a nozzle type

Choose the right type of nozzle that will produce the best spread of spray drops in the best shaped swath with the best sized spray drops for your spraying task. Understand how nozzle spacing affects the quality of your spraying. Check your pesticide label for advice.

Types of nozzle

The types of nozzles shown above are even fan, standard flat fan, deflector (x2), hollow cone and solid cone nozzles.

Nozzles are designed to create and direct drops of spray, which land and form a shape or swath. Different types of nozzles create swaths (footprints) of different shapes.

These swaths are from even fan, standard flat fan, deflector, hollow cone and solid cone nozzles. The first row shows the downward spray patterns of each of the nozzles. The second row shows the 'footprint' on the ground of each nozzle. The third row shows the volume of spray deposited across the swath.

Some swaths are better for some spraying tasks than others. Choose the nozzle that is best for your spraying need.

How nozzles work: Design and size

As the pressurised spray mix comes out of the nozzle it forms a sheet of liquid. This sheet gets thinner and thinner as it widens out, before breaking up into drops. The width of the footprint of these drops on the ground and the spread of the drops within the footprint, are controlled by the design of the nozzle.

The size of, and pressure of the liquid at, the nozzle opening, control the flow rate (L/minute). The speed at which you spray then determines the spray mix volume rate that you apply.

The design of the nozzle and the pressure at the nozzle opening also combine to produce smaller or larger drops of spray. For example at the same pressure, hollow cone nozzles produce smaller drops than deflector nozzles. This means that for nozzles producing larger drops there will be fewer drops to cover the target surface and for nozzle producing smaller drops there will be more drops to cover the target surface.

Each single nozzle can produce a range of flow rates and hence volume rates. The nozzle size (e.g. 03 Blue, 02E) that will produce the combination of drop size and volume rate that you need is a function of:

the size of the nozzle orifice
the pressure at the nozzle orifice
the operator's walking speed.

Drop sizes

Drop size can affect both how well the drop reaches and remains on a target surface and the cover of pesticide drops over the target surface. It can also affect your safety and that of your enviroment.

Stop the pesticide from spreading: spread sand, sawdust, soil, vermiculite, clay or cat litter around the spill to create a wall. Scatter more over the top of the liquid to absorb it. Block nearby drains and prevent the spill from getting into any ground or surface water.

Keep people, animals and children at least 10 meters away: make sure no-one is downwind and if needed, rope off the spill site. Control the flow of the pesticide spill: if the source of the pesticide is a leaking pesticide pack, place the pack into the empty, leak-proof drum and seal the drum. If the spill is from a leaking knapsack sprayer put the knapsack sprayer into the leak-proof drum or a bunded site. Keep people, animals and children at least 10 meters away:

Terms used for drop size

The terms often used for drop size are:

Code	Category	VMD range (microns)
XF	Extremely Fine	Up to 60
VF	Very Fine	61-144
F	Fine	145-235
M	Medium	236-340
C	Coarse	341-403
VC	Very Coarse	404-502
XC	Extremely Coarse	503-665
UC	Ultra Coarse	More than 665

Nozzle spacing

Make sure that you space your nozzle correctly so that you:

apply the right amount of spray mix
get a uniform spread of spray drops.

Spray width, swath width and nozzle spacing

The spray width (A) is the width of the area wetted by the sprayer in one pass. Where more than one nozzle is used this is the entire width of the area wetted by all the nozzles. The swath width (B) is that part of the spray width that has a uniform spread of spray drops. Note the difference between the swath width produced by the nozzles with an even distribution of spray drops across the spray width (shown left) and the nozzles with a tapered distribution of spray drops across the spray width (shown right). Nozzle spacing (C) is the distance between the nozzles on a boom. Where only one nozzle is used it is the distance between the nozzle positions on adjacent spraying paths.

For nozzles that give an even spread of spray drops across the whole spray width, the spray width and the swath width are the same. Swaths should be sprayed alongside one another and each swath should adjoin but not overlap the one before it. The nozzle spacing will equal the spray width.

Standard flat fan nozzles are designed for broadcast spraying and can also be used for lateral spraying. They spray fewer drops at the edges of the spray width. As the spread of drops is not even across the whole spray width, the spray width will be wider than the swath width. When spraying, each spray width should overlap the spray width before it. The amount of the overlap will be set by the nozzle spacing. Refer to your nozzle's chart for the right spacing to use. The swath width will be the number of nozzles multiplied by the nozzle spacing.

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