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This page illustrates the main nozzle
types and some of the droplet size data that
is available in the DROPDATA database. Data and pictures are available
on:
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Hydraulic Nozzles
See:
The 
guide to hydraulic nozzles and examples of droplet
size spectra of various nozzles.
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Standard
flat fan nozzles are perhaps the most widely used nozzle in
western agriculture. They commonly are fitted to both vehicle-mounted
and manual hydraulic
sprayers.
A
flat fan nozzle: the 110 03
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A
cone nozzle fitted to the Chinese 'River Mountain' sprayer.
Nozzles such as this are very common in Asia. |
Current
research on narrow-angle cone nozzles:
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Optimising
dose transfer to cocoa pods and other small biological targets
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Links: hydraulic nozzles:
Home
Grown Cereal Authority nozzle calculator
for grains and oilseed-rape.
Protocols
for hydraulic nozzle evaluation: the BCPC
Expert Working Group on Pesticide Application
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Air Shear Nozzles
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Air
shear nozzles are most commonly found on motorised
mistblowers; these now have many uses, but one of the
first was achieving good droplet coverage for control of mirids
in the tall cocoa trees of West Africa. They also can be used
for fungicides, which perhaps require the greatest efficiency
of coverage of all the pesticide types. However, they are
out the price-range of many smallholder farmers.
The
most common design of nozzle is of the air-shear type, in
which thin layers of liquid are introduced into the air stream
and thus produce fine sprays.
Illustration:
nozzle of a 'Stihl' SR420 mistblower
with baffle plate
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Rotary Nozzles
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Rotary
(spinning disc and cage) atomisers usually produce a more
uniform droplet size spectrum than conventional nozzles, and
have proved to be the most successful way of delivering pesticides
in the form of Controlled Droplet Application (CDA). CDA
can be defined in terms of optimising technology to achieve
a biological objective: delivering appropriately sized droplets
(within practical engineering limits) for maximising the control
of a given pest target, (where this is known).
Since
CDA atomisers are capable of maximising coverage
at very low volume application
rates, they are frequently used for specialised, targeted
application techniques such as seed and nursery treatments.
High
speed photograph of ligament formation on the periphery of
a rotary atomiser. (Photo courtesy Micron
Sprayers Ltd.)
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Droplet
data on Motorised Mistblowers
Motorised
mistblowers may be supplied (or retro-fitted) with rotary
atomisers to improve the quality of droplet spectrain order
to lower volume application
rates. CDA techniques have necessitated detailed analysis
of formulation, droplet size and recovery: especially with
particulate agents such as biopesticides. This paper describes
droplet size work that was carried out on spinning disc (handheld)
and motorised mistblower nozzles, with oil-based and aqueous
formulations.
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Other
atomisers:
Foggers and Electrostatic Application
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(Matthews & Bateman, 2004, AAB): A rotary atomiser operated
at 17,000 rpm with a flow rate of 35ml/min is proposed as a
reference nozzle to differentiate between the spray spectra
produced by mist and fog application equipment. |
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Electrostatic spraying: Whatever
happened to the 'Electodyn'? ... ED
use in Forestry.
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Issues
Disappointingly
few farmers world-wide are aware of the true performance
of hydraulic nozzles, which inefficiently use large volumes
of water, but remain by far the most important method of pesticide
application. Worse still, recent emphasis in application research
has focused on the reduction of spray drift (especially in Europe
and N. America). The most common solution to be implemented to date
has been to increase droplet size spectra (without necessarily improving
spray quality); thus spray application has probably become generally
more inefficient.
Spray
drift:
The UK Government's Pesticide
Safety Directorate gives guidance on many pesticide issues relevant
to N. European agriculture. The UK has pioneered work on reducing
spray drift: developing the first classification
scheme for commonly-used flat-fan nozzles, then later developing
the Local Environment Risk Assessment For Pesticides or LERAPS
protocols.
In the USA, the spray drift task force
was set-up to develop generic data base on premise that spray drift
behaviour is independent of active ingredient. See: http://www.agdrift.com/.
Much of the focus was on aerial
spraying - for which rotary nozzles are available and recommended
for ULV to achieve high work rates.
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| Note
These data are placed in the public
domain on the understanding that:
- The data on nozzle performance is
for information and guidance only, and have no commercial or legal
implications whatsoever.
- All readings have been obtained
using commercially available nozzles and blank formulations (unless
stated otherwise); the work was carried out either as part of
a publicly-funded project or in the author’s own time. None of
this information has been obtained during contract research (unless
permission has been given by the contractor).
- This data is contributed to the
public domain in the spirit of open access to useful scientific
information. We have taken reasonable efforts to make accurate
measurements (which have been replicated, unless stated otherwise),
but mistakes may of course occur. Any comments, criticisms or
other observations should initially be directed to the author,
who will try to clarify statements or correct errors.
For more information contact
us. As well as pursuing our current
research
programme, we are
able to carry out contract R&D on:
- Measurement of sprayer performance
(especially droplet sizing) for commercial product development
and registration.
- Droplet sizing of new formulations
and adjuvants (provided they are in WHO mammalian toxicity class
III or above).
- Assessment of durability of sprayers
and nozzles under simulated operational use.
- Consultancy on any of the subject
matter in the DROPDATA pages.
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