The advantages of modifying spray droplet trajectory by inclining the nozzles that produce them is not only well documented from trials, but also from widespread field experience.
Improved target coverage and better penetration of a dense crop canopy compared with sprays projected vertically make the use of angled sprays common practice and increasingly operators are angling nozzles both forwards and backwards to obtain two lots of coverage and two different droplet trajectories.
The latter approach can be achieved in two ways – by installing angled tips alternatively forwards and backwards across the boom and using a height setting that gives sufficient fan overlap for double spray coverage across the full width, or by fitting two vertical tips into a twin bayonet cap.
“The twin cap has its attractions because it caters for high volume applications and allows operators to mix and match tip sizes to achieve a particular working speed, pressure and volume combination,” notes Richard Riley of Altek International. “But for simplicity – and for a more compact installation – the single nozzle with two outlets is an attractive solution.”
A further advantage of this approach over alternating angled nozzles is that the boom can be set lower – which itself will have a positive impact on drift control – and the target treated with four overlapping sprays.
As Altek is the newly-appointed UK distributor for the Lechler range of agricultural spray nozzles, Mr Riley welcomes the introduction of two additional sizes to Lechler’s IDK-T line-up. The IDK is the German manufacturer’s single outlet air inclusion tip, which mixes air and liquid to produce a relatively coarse spray with good drift control properties.
The IDK-T is the twin outlet version, which was initially introduced with ceramic tip inserts and last year became available as an all-plastic moulding.
“Ceramic is favoured by contractors and other high usage operators because of its durability, especially at the higher operating pressure used with air inclusion tips,” Mr Riley points out. “But it is more expensive: The IDK-T ceramic retails at £7.50 each compared with the polyoxymethtlene (POM) version at £5.50.”
The Lechler IDK-T is similar in appearance to the single outlet version and at just 8mm long is very compact. The ceramic model is available in 03, 04 and 05 sizes, while the POM version comes in those same sizes and the newly-introduced 02 and 025.
“Those will be welcome additions because they’re ideal for smaller sprayers not working too fast,” says Mr Riley. “It concerns some people, though, that the tips will be prone to blocking, as a result of incorrectly assuming that the outlet orifices of an 02 must be equivalent to an 01.
“But that’s not the case,” he assures. “The liquid is metered in the body of the nozzle through a hole equivalent to a conventional 02 tip and then divided between the two outlets; they merely form the spray pattern.”
The 120° flat fan sprays produced by the IDK-T are inclined 30° forward and 30° backward – as are the sprays produced by the equivalent design produced by Lechler for Hardi.
At present, the MiniDrift Duo range comprises three sizes – 03, 04 and 05 – all produced in thermodynamic plastic. Like the IDK-T, the MiniDrift Duo is reckoned to produce an output with “medium to very coarse” spray quality in air inclusion tip terms. This results in effective anti-drift at low pressures between 1 and 2 bar, but the tip is said to also provide good coverage in the high pressure range up to 6 bar.
Two large air inlets located in the sides of the tip are designed to minimise the risk of blockages caused by dust and debris, and the injector or metering insert can be removed for cleaning inside the tip, which is produced to ISO norms and fits a standard bayonet cap.
Hypro has also introduced a two-outlet air inclusion product – but as a complete nozzle assembly with an integral cap rather than as a separate tip.
“It’s an assembly with a new smooth-turning bayonet fitting action that not only makes it easy to fit, but automatically aligns the tip correctly,” explains Roger James of Hypro EU. “I think operators will like the convenience of the all-in-one design.”
The GuardianAIR Twin air inclusion nozzle has a single metering orifice and air mixing chamber, but two outlets, each producing a 110° flat fan spray pattern that are inclined 30° forwards and 30° backwards.
It has a two-piece metering/air-mixing insert that can be removed to clean behind the outlets and will be produced in five sizes – 03, 04, 05, 06 and 08. The GuardianAIR Twin has been released on a limited availability basis this year following successful field experience with a handful of growers in 2010.
But it has already been put through tests at NIAB TAG’s Spray Application Unit in Bedfordshire to produce droplet size data for the HGCA’s latest Nozzle Selection Chart. The results showed that at the 3 bar test pressure, the GuardianAIR Twin produced the smallest droplets of any air inclusion tip tested, narrowly beating the single GuardianAIR in this respect.
“A spray tip making droplets only 15% bigger than those from the GuardianAIR will produce around a third fewer droplets for the same application volume,” Mr James points out.
“This loss of coverage has clear implications for the reliable delivery and retention of crop chemicals, especially to small targets.”
A conventional flat fan tip is still the best option for targets requiring the finest droplets, he agrees.
“But they require ideal spraying conditions to avoid the loss of coverage and potential to damage adjoining crops caused by drift,” Mr James adds. “Operators can use the versatility of an air inclusion tip like the GuardianAIR that holds its pattern across a range of operating pressures to spray at normal pressures when conditions are good and get a very small droplet size for this type of nozzle, and then increase droplet size for optimum drift control when spraying conditions are imperfect.”