HARDI H-SELECT - Precise speed, rate and droplet control for large spray booms

Not so long ago, 36 metres was considered a large spray boom. But in recent years the rise of engineered aluminium has made 48.5 and even 54.5 metre booms increasingly normal.

Larger booms boost productivity – getting more ground covered in the available weather window and sparing the operator many hours on the sprayer. However the tip-to-tip speed difference across a wide, turning boom is also driving the need for a fast, precise nozzle control technology.

As HARDI Australia’s Product Manager for large sprayers Steve Lancaster points out, the outer tip of a 48.5 m boom travels considerably faster than the inner tip in every turn – leading to significant under- and over-dosing around headlands or any obstacle in the paddock.

‘If you’re making a 50 m radius turn at 20 km/h, the inner end of a 48.5 m boom will slow down to just 10.3 km/h while the outer tip will accelerate to 29.7 km/h. In other words the tip-to-tip speed range of 19.4 km/h is almost equal to the forward speed of the sprayer, and the flow rate will need to double across the boom.’

“HARDI solves the problem by combining multi-tiered spraying with the H-SELECT system,” he says. “It provides accurate target rate control over the widest possible speed range.”

H-SELECT uses 4-head nozzle bodies arrayed in individual or selected boom sections. An autonomous controller manages each section’s speed against the set spray rate, then switches the nozzle heads on and off rapidly and precisely in order to achieve consistent spray delivery across the turning boom.

“H-SELECT calculates the speed of the sprayer and automatically activates the best combination of nozzles for each boom section,” Lancaster explains.

This rapid, blended switching between nozzle combinations means H-SELECT can achieve a target rate accuracy of 90% or better over the entire paddock – virtually eliminating patches of over- or under-dosage.

The nozzle switching is controlled by a solenoid-activated air pressure system, which also enables constant fluid recirculation and lets the boom be operated in unlimited sections. (18 sections is standard.)

Air switching frees the system from the electrical losses incurred by electronic platforms when the wire runs exceed about 18 metres per side, or 36 metres overall.

Precise droplet control also makes H-SELECT an effective drift management system. Because it uses combinations of nozzles to manage the target rate at a constant pressure, the droplet size doesn’t change with the rate adjustments.

“The operator can set a droplet size and even change it on the move, using the in-cab Run Screen,” Lancaster reports. “It means they can adjust their droplet size throughout the day, to manage wind speed, temperature and humidity changes.”

“Farmers can also use a coarse droplet to spray the paddock perimeter, then change to a finer setting once they’re away from the fence lines.”

H-SELECT is currently available on HARDI RUBICON, SARITOR, and ALPHA Self Propelled machines, and HARDI COMMANDER trailed sprayers. The system integrates with the on-board ISOBUS.

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