TIBRE Arable Handbook 2004 - Targeted Inputs for a Better Rural Environment

Rotary Atomisers

What are they?

Rotary atomisers use the centrifugal energy created by a spinning disc, cup or cage to create a spray, rather than using liquid pressure. Important features of this system are the ability to produce a more tightly controlled droplet spectrum than pressure based nozzles, and the ability to maintain spray quality over a large range of liquid flow rates at a particular atomiser rotational speed. Rotary atomisers can operate effectively at very low volumes. Trials have shown that good control of drift can be achieved when compared with conventional nozzles producing the same spray quality. Rotary atomisers are usually either electrically or hydraulically powered.

How can they help you?

  • The ability to closely control droplet size and change spray quality and output rate on the move improves targeting and minimises pesticide costs
  • Improved timeliness and optimised pesticide use from use of low volumes
  • Systems are less prone to blockage than conventional nozzles, resulting in less downtime and less risk of operator contamination

How can they help the environment?

Caution

Using very low volumes with rotary atomisers requires careful choice of product and spray quality. Spray behaviour/trajectory is different from conventional hydraulic pressure nozzles.

Availability and use

Rotary atomisers need special mounting brackets and additional electrical wiring/controls or hydraulic lines/valves and are therefore better suited to being incorporated into a complete spraying system. Retrofitting such a system onto a conventional sprayer is possible but complex.

Rotary atomisers are more complex to operate and maintain than conventional spraying systems because of the need to set/adjust atomiser rotational speed as well as liquid output. The atomisers are relatively complex, have moving parts, and a reasonably high degree of maintenance is required to ensure good performance.

The tight control over droplet sizes in the spray from rotary atomisers means that some of the defined spray qualities will not directly match those from conventional nozzles; this is why drift reduction is achieved for the same nominal spray quality. If very low drift levels are needed, low atomiser rotational speeds must be used in order to produce large spray droplets.

Because the output from rotary atomisers can be adjusted over a wide range (more than a factor of 3:1), this design is useful in targeting sprays better and in patch spraying.

Deposition (Ál cm-2 x 10,000) of fluorescein tracer after correction for application volume through a wheat crop at different growth stages from flat fan nozzles and rotary atomisers (▒SE).

Growth
stage

Sampling
position
Flat fan
nozzles
200l/ha
Rotary 20l/ha
(fine quality
spray)
Rotary atomiser
40l/ha (medium
quality spray)
31 Leaf 1 5 (1) 75 (5) 15 (1)
Leaf 3 7 (1) 35 (4) 17 (6)
Ground 9 (1) 44 (6) 21 (3)
39 Flag 5 (0) 34 (2) 12 (1)
Leaf 3 4 (1) 23 (1) 10 (0)
Ground 2 (0) 10 (0) 9 (1)
59 Ear 2 (0) 10 (0) 10 (0)
Flag 3 (0) 12 (1) 16 (1)
Leaf 3 2 (0) 13 (1) 13 (1)
Ground 3 (0) 11 (0) 11 (0)
70 Ear 9 (1)   6 (1)
Flag leaf 26 (2)   30 (3)
Leaf 1 25 (1)   26 (3)
Ground 12 (1)   18 (2)
75 Ear 15 (1) 24 (2)  
Flag leaf 26 (1) 60 (14)  
Leaf 1 23 (2) 17 (1)  
Ground 15 (1) 10 (1)  
77 Ear   30 (2) 19 (3)
Flag leaf   30 (2) 30 (3)
Leaf 1   20 (1) 20 (2)
Ground   16 (1) 14 (2)

From Holland et al., 1997

Using reduced volumes with rotary atomisers gives equivalent control to high volume applications, with large reductions in dosage rates possible against specific targets (see figure).

Corrected cereal aphid mortality following application of deltamethrin at half (3.125g a.i./ha) and one twentieth (0.313g a.i./ha) of the full recommended dosage rate on winter wheat using rotary atomiser and flat fan nozzle sprays

From Holland et al., 1997

How much will it cost you?

Capital cost There is a higher capital cost than for a conventional sprayer because of the need to power the atomisers and because of the complexity of the atomisers

££

Operating cost Operating costs for rotary atomiser sprayers are higher than for a conventional system due to maintenance requirements

£

Cost benefits Better timeliness and better use of pesticides due to targeted low volume sprays should enable the higher capital and operating costs to be recovered

J

 

Technical tip

Rotary atomisers need to be well maintained.Ensure that the system is thoroughly cleaned and basic maintenance is carried out at the end of each spray operation.

Further information

Technology links

References

Holland J.M., Jepson P.C., Jones E.C. and Turner C. (1997). A comparison of spinning disc atomisers and flat fan pressure nozzles in terms of pesticide deposition and biological efficacy within cereal crops. Crop Protection 16 (2), 179-185.

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