2 Very Good Reasons to use Air Induction Nozzles on your knapsack sprayer
… rather than conventional nozzles:
- They make the spraying activity safer for the operator
- The sprayed pesticide is more likely to hit the spot and stay there
Air bubble jets, air induction nozzles, air inclusion nozzles, injector nozzles and venturi nozzles all work on the same basic principles and are available as flat fan or hollow cone nozzle types.
Research indicates that when using air induction nozzles, spray drift can be reduced by an impressive 50 to 70%; reducing the risk to operators and the environment by reducing exposure to the pesticide from spray drift. It also means that more pesticide reaches the target surface and – because the designed drops incorporate air which cushions the drops on landing - these drops are more likely to remain on the target surface. Spray drops emitted using conventional nozzles however, are less likely to remain on the target surface as they bounce or run off thus air bubble jets are more likely to help you gain improved control in a safer manner!
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How do air induction nozzles work?
The liquid spray passes through a removable tapered nozzle (A) that accelerates the liquid and projects the flow into the tapered opening of the venturi (B). This movement of liquid creates a vacuum that causes air to be sucked in through the slots marked (C).The mixture of air and liquid is compressed as it passes through the mixing chamber (D) and is then sprayed through the nozzle which may be a fan (E) or hollow cone (not shown).The spray emitted comprises larger droplets filled with air bubbles and contains very few small [fine], drift prone droplets. (Billericay Farm Services)
The problem with conventional nozzles is that the spray entrains [picks up] quantities of air and together the drops of spray and air form a near solid curtain across the full swath of individual or multi nozzle swaths. As the sprayer moves forward, air pressure builds up in front of the spray swath; which forces the smaller drops out of the swath and to form clouds of drift.
In contrast, the spraying swath from bubble jets is porous; the drops are fewer and slower and so air is let through the swath and the drops stay on route to their intended target. This use of larger, air-filled drops and the resulting porosity of the spraying swath to wind allows the operator to achieve high levels of drift control and produce very high levels of target surface cover. Improvements in target coverage mean that where contact pesticides are used, even the smallest weeds will be adequately sprayed.
Trials by independent researchers and the pesticide manufacturer all agree; drift is reduced to such a level that these nozzles can meet regulatory needs yet the biological response is not compromised. (Powell, Orson, Miller, Kudsk & Mathiassen, 2002)
How many types of Air Bubble Jets are available?
There are two main variants on the Air Bubble Jet,
- high pressure jets which are ideally suited to use on boom sprayers or other pumped sprayer units. These require pressures in excess of 3.0 bar and up to 7.0 bar. And
- low pressure jets which are best used on knapsack sprayers and produce good quality spray from 2.0 bar.
Fitting Air Bubble Jets is easy
Nozzles are colour coded and conform to International Standards for size, flow rate and other operating parameters such as pressure. It is therefore a simple task to replace your existing nozzle with the drift reducing Air Bubble Jet of a similar size. The nozzles most suitable for knapsack sprayers are 015 Green, 02 Yellow, 025 Lilac, 03 Blue and the 01 Orange which is especially important for spraying low water volume rates. (See also: Answers to FAQ's: What is ultra low volume spraying?).
To find out which air induction nozzle is best for your purposes try BFS' nozzle calculator. You will need to know the
- Spray volume required [litres/hectare]
- Spraying speed [km/hour]
Check out the research: “Considering the use of air induction nozzles to reduce operator contamination when using knapsack sprayers” (Stephens, Woods, Cooper & Goddard, 2006)
Powell E S; Orson J H; Miller, P C H; Kudsk, P & Mathiassen S . Defining the size of target for air induction nozzles. Aspects of Applied Biology 66, International Advances in Pesticide Application 2002 pp65-72